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TUNE IN TO THE 800 -MHz SCANNER BAND!48783

1992

Emile

TECHNOLOGY - VIDEO - STEREO - COMPUTERS - SERVICE

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Introducing SCOPEAETERThere's More Than One Reason to Reach for It.In fact, there's every reason to reach for ScopeMeter:" Because only ScopeMetercombines the expertise of Fluke and Philips to bring you a dual -channel digital scopealong with everything you've come to expect from Fluke digital multimeters.

The result: an integrated scope-and-multimeter that lets you see a waveform anddigital meter display at the same time from the same input. Or switch betweendedicated high-performance Scope and Meter functions with the touch of akey. That makes it faster and easier than ever to capture, store and analyzeprecisely what you're looking for. At a price that looks good, too.

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February 1992 Electronics,Zlectrunics,Vol. 63 No. 2

BUILD THIS33 BUILD THE HYPERCLOCK

Display the time in eight eye-catching modes!Leon W. Schmidt

42 SCANNER CONVERTERIt allows unrestricted coverage of the 800 -MHz band!William Sheets and Rudolf F. Graf

53 SWEEP/FUNCTION GENERATORMeasure square, triangle, and sine waves with this inexpensivebenchtop instrument.Michael A. Lashansky

65 EXPERIMENTING WITH ADC FOR YOUR PCAdd analog inputs to the PC -based analog -to -digital converter.James J. Barbarello

48 AM TRIES FOR A COMEBACKWill the new AMAX receivers breathe new life into the AM band?Len Feldman

69 WORKING WITH LED'SOur in-depth survey of LED's continues with practical chaser andbargraph circuits.Ray Marston

BUILD THE

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SCANNERCONVERTER

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PAGE 42

AND MORE6 VIDEO NEWS

What's new in this fast -changing field.David Lachenbruch

16 EQUIPMENT REPORTSKelvin 100K DMM kit.

77 HARDWARE HACKERCaller ID update, and more.Don Lancaster

86 AUDIO UPDATEMore reader questions.Larry Klein

89 DRAWING BOARDGetting back to ouroscilloscope.Robert Grossblatt

92 COMPUTERCONNECTIONSPen -based computing.Jeff Holtzman

106 Advertising and SalesOffices

106 Advertising Index12 Ask R -E

14 Letters97 Market Center27 New Lit22 New Products

4 What's News

ON THE COVER

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The 800-1000 MHz band of UHFfrequencies contains many signalsof interst to the shortwave and scan-ner enthusiast. However, manyscanner can't receive those frequen-cies. Our scanner converter re-ceives signals from 800-1000 MHz,and outputs them at 400-500 MHz.That allows you to monitor frequen-cies in the 800-1000 MHz rangeusing your 400-500 MHz scanner.You can also use it to measure fre-quencies as high as 1000 MHz with a500 -MHz counter. To find out moreabout our converter, turn to page 42.

NEXT MONTH

THE MARCH ISSUEGOES ON SALEFEBRUARY 4.

MIDI INTERFACE FOR YOUR PCYour passport to the world of computer -controlled music.

BUILD DIGI-CALLKeep tabs on phone bills and client billing with this intelligent telephone -line monitor.

SCANNER CONVERTER: PART IIEasy -to -build downconverter gives unrestricted coverage of the 800 -MHzband.

ELECTRONIC TEMPERATURE MEASUREMENTAn overview of the components and circuits used to measure temperatureelectronically.

As a service to readers, RADIO -ELECTRONICS publishes available plans or information relating to newsworthy products.techniques and scientific and technological developments. Because of possible variances in the quality and condition ofmaterials and workmanship used by readers, RADIO -ELECTRONICS disclaims any responsibility for the safe and properfunctioning of reader -built projects based upon or from plans or information published in this magazine.

Since some of the equipment and circuitry described in RADIO -ELECTRONICS may relate to or be covered by U.S. patents.RADIO -ELECTRONICS disclaims any liability for the infringement of such patents by the making. using, or selling of any suchequipment or circuitry. and suggests that anyone interested in such projects consult a patent attorney.

RADIO -ELECTRONICS. (ISSN 0033-7862) February 1992. Published monthly by Gernsback Publications, Inc.. 500-B Bi-CountyBoulevard, Farmingdale, NY 11735 Second -Class Postage paid at Farmingdale, NY and additional mailing offices. Second -Classmail registration No. R125166280, authorized at Toronto, Canada. One-year subscription rate U.S.A. and possessions $17.97,Canada $25.65 (includes G.S.T. Canadian Goods and Services Tax Registration No. R125166280), all other countries $26.97. Allsubscription orders payable in U.S.A. funds only, via international postal money order or check drawn on a U.S.A. bank. Singlecopies $2.95. C 1992 by Gernsback Publications. Inc. All rights reserved. Printed in U.S.A.

POSTMASTER: Please send address changes to RADIO -ELECTRONICS. Subscription Dept., Box 55115, Boulder, CO80321-5115.

A stamped self-addressed envelope must accompany all submitted manuscripts and/or artwork or photographs if their return isdesired should they be rejected. We disclaim any responsibility for the loss or damage of manuscripts and/or artwork or

2 photographs while in our possession or otherwise.

anl MaimClectrunics®Hugo Gernsback (1884-1967) founder

Larry Steckler, EHF, CET,editor -in -chief and publisher

EDITORIAL DEPARTMENTBrian C. Fenton, editorMarc Spiwak, associate editorKim Dunleavy,

assistant technical editor

Teri Scaduto, assistant editorJeffrey K. Holtzman

computer editorRobert Grossblatt, circuits editorLarry Klein, audio editorDavid Lachenbruch

contributing editorDon Lancaster

contributing editorKathy Terenzi, editorial assistant

ART DEPARTMENTAndre Duzant, art directorlnjae Lee, illustratorRussell C. Truelson, illustrator

PRODUCTION DEPARTMENTRuby M. Yee, production directorJanice Box,

editorial productionKaren S. Brown

advertising productionMarcella Amoroso

production assistant

CIRCULATION DEPARTMENTJacqueline P. Cheeseboro

circulation directorWendy Alanko

circulation analystTheresa Lombardo

circulation assistantMichele Torrillo, reprint bookstore

Typography by Mates GraphicsCover photo by Diversified Photo

Services

Radio -Electronics is indexed inApplied Science & Technology Indexand Readers Guide to Periodical Liter-ature.Microfilm 8 Microfiche editions areavailable. Contact circulation depart-ment for details.

Advertising Sales Offices listedon page 106.Radio -Electronics Executive and

Administrative Offices1-516-293-3000.

Subscriber Customer Service:1-800-288-0652.

Order Entry for New Subscribers:1-800-999-7139.

TheAuditBureau

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WHAT'S NEWSA review of the latest happenings in electronics.

Device for multipleautomobile air bags

Researchers at Sandia NationalLaboratories (Albuquerque, NM)have invented a low -energy ex-plosive igniter that could make iteasier for automobile manufac-turers to install multiple air bags intheir vehicles. The device, called asemiconductor bridge or SCB, re-quires much less energy than thehot-wire igniters that are tradi-tionally used in air -bag systems.

During the rapid decelerationcaused by a crash, air bags are elec-trically ignited by a hot-wire devicein an explosive cartridge. As the de-vice heats, the sensitive explosivematerial burns. A hot gas is pro-duced that enters the stowed airbag and ignites a gas -generatingpropellant, which then releases aburst of nitrogen gas that quicklyinflates the bag. That entire processtakes place in just thousandths of asecond.

When designing air -bag systems,a worst -case scenario of an almost

SANDIA'S SEMICONDUCTOR BRIDGE,which could be used in multiple air -bagsystems, is shown resting on a penny.The penny's "C" letter give an Indicationof the device's sire.

depleted battery is used. In such acase, one hot-wire igniter wouldconsume nearly all of the battery'sremaining voltage output-whichmeans trouble for systems incor-porating several air bags and ex-plosively activated seat belts.

The semiconductor bridge isabout one one -hundredth the vol-ume of a conventional hot wire, andcan be heated much faster and withmuch less energy. Because SCB'sare processed on a silicon wafer, thechip can incorporate extra circuitryfor logic, timing, and safety.

Multimillion dollarinteractive TV/satellitecontract

The introduction of nationwide in-teractive television is a step closerwith the signing of a multimillioncontract between TV Answer, a pi-oneer in real-time wireless Interac-tive Video Data Service (IVDS)technology, and Hughes NetworkSystems, Inc. (HNS), manufacturerof interactive Very Small ApertureTerminals (VSAT's). Pending FCCapproval, the TV Answer systemwould allow television viewer to usetheir TV's as communication de-vices to pay bills, order take-outfood, shop for groceries, do bank-ing transactions, and respond in reartime to game shows, TV shoppingshows, advertisements, polls, andinteractive news and educationalprograms. In addition, it would serveas a universal remote control, andwould provide on -screen TV sched-ules and VCR programming. Thesystem would work with cable, sat-ellite, and roof -top antenna systemsand is expected to cost about$12.95 a month.

Similar in structure to a cellularphone network, the TV Answer net-work relies on individual cell sites toprovide service to a market areaconsisting of a maximum of 10,000households. Each cell site includesa VSAT two-way satellite dish earth -station that communicates with TV

TVAnswertknornrnrs,

t411MicrowaveTi

TV ANSWER'S INTERACTIVE VIDEODATA SERVICE would use Hughes Net-work Systems' satellite personal earthstations to provide direct transmissionpaths between remote cell sites and thehub station.

Answer Headquarters via a Hughessatellite, and a TV Answer radio re-ceiver/transmitter that communi-cates with TV Answer home units.The data received via satellite istransformed at the cell site into aradio signal that is transmitted toeach home unit. Viewer responsesare relayed to the cell site and thenback to headquarters in the sameway. There the responses are pro-cessed and appropriate collection,billing, and ordering activities areperformed.

The January 10,1991 FCC Noticeof Proposed Rulemaking proposedthe allocation of 1/2 -MHz of the radiospectrum-between 218.00 and219.00 MHz, which is the frequencyon which TV Answer's system oper-ates-for an Interactive Video DataService. The action is expected tobe finalized, and technical stan-dards and licensing procedures is-sued, by mid -1992.

Under the initial phase of the con-tract between HNS and TV Answer,HNS will build and install 1000VSAT units for use in cell sites-enough to meet the projected first -year requirement. The initial phaseincludes a $2.1 million hub and net-work control system at TV Answerheadquarters in Reston, VA. TV An-swer estimates that a minimum of10,000 VAST units will be needed toprovide nationwide coverage for itstechnology. R -E

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VIDEO NEWSWhat's new in the fast -changing video industry.

DAVID LACHENBRUCH

Compact Disc -Interactive.Philips has launched its CD -I inter-active audio -video multimedia sys-tem through 5000 stores, and firstreports indicated that the playersand discs were selling well. Philipschanged its mind about brandname, and its first products wereissued under the "Philips" insteadof the "Magnavox" brand. The listprice of the player was dropped to$1000 from $1400, but for all prac-tical purposes, players are selling atabout $800, and discs from $20 to$40. Using the theme, "the Imag-ination Machine," Philips plans ma-jor advertising campaigns for thesystem throughout 1992. This is thesecond multimedia CD systemaimed at the general public via at-tachments to TV sets, the firstbeing Commodore's CDTV (whichstands for Commodore DynamicTotal Vision). Other manufacturersare competing with video and audioCD-ROM systems designed ascomputer peripherals.

Zenith moves TV. The last ma-jor American -owned TV manufac-turer will end color -TV manufacturein the United States sometime thisyear. Zenith Electronics announcedthat it will start phasing out final as-sembly of sets in its Springfield,MO plant when its union contractexpires on March 22. The company,which has been losing money, ex-plained that price erosion has con-tinued in the TV industry and cost-cutting efforts haven't been suffi-cient, despite wage concessions byits union in Springfield.

Zenith will move final assembly oflarge -screen TV sets to its cabinetplant in Juarez, Mexico. Its 19- and20 -inch sets are already being as-sembled in Reynosa, Mexico. Someplastic molding and distribution op-erations will continue in Springfield.Zenith will continue to operate itslarge -picture -tube plant and head-quarters in the Chicago. The onlyother American -owned TV as-sembler, Curtis Mathis Corpora-

tion, has a final assembly plant inAthens, TX. Although the remainderof TV manufacturers are foreign -owned, many of them continue toassemble their large -screen colorTV's in the United States. The lead-ers are Thomson Consumer Elec-tronics (French -owned), which as-sembles RCA and GE sets inBloomington, IN, and Philips(Dutch), which produces Magna-vox, Sylvania, and Philips sets inGreeneville, TN. Other final TV as-sembly is done in Huntsville, AL, byGoldstar (Korean); by Japanesemanufacturers in Anaheim, CA;JVC in Elmwood Park, NJ; Mit-subishi in Santa Ana, CA andBraselton, GA; Orion in Princeton,IN; Sanyo in Forrest City, AR; Sharpin Memphis; Toshiba in Lebanon,TN; and Sony in San Diego aidsoon in New Stanton, PA.

"Stereo" TV debate. As itpromised more than a year ago (Ra-dio -Electronics, March 1991), acompany called dbx Technology Li-censing has started a public -rela-tions campaign to inform the publicthat if a television set doesn't con-form with the FCC -backed stereo -TV system, it shouldn't be called"stereo TV." However, ThomsonConsumer Electronics, manufac-turer of RCA and GE brand sets,has challenged dbx, saying thatsome of its sets contain a new sys-tem called "XS" and qualify as ster-eo even though they don't use thedbx noise -reduction decoding tech-nology that is officially part of theMultichannel TV System (MTS)stereo standard.

Although Thomson's higher -priced sets do use dbx decoding,Thomson says that the XS soundsystem, which uses phase shift toprocess the sound, qualifies as"stereo" even though little separa-tion between left and right channelsshows up in tests. dbx demon-strated test results that it saysshows that some RCA and GE setsdon't reconstruct the true sound

transmitted by the TV stations.Thomson retorts that its XS systemsounds better than dbx in lower -priced sets. In addition to Thomson,dbx Technology found that somePhilips and some Sharp sets don'tuse dbx decoding in their stereosystems. Both of those companies,which use dbx in some of their sets,say they plan to add dbx across theboard to all of their sets later thisyear. Since there is no official defini-tion of "stereo," the dispute is ex-pected to continue for some time.Stereo systems using various typesof phase -shift techniques to en-hance the "presence" effect in-clude Q sound and SRS, the latterdeveloped by Hughes Aircraft andbeing used tin some high -end setsby Sony and Thomson as an adjunctto MTS stereo. dbx says that's okay,some people may prefer processedsound, but officially MTScludes dbx encoding and decoding;therefore, saying that a set included"broadcast TV stereo" or "MTSstereo" is misleading.

TV for computers. For yearswe've heard about the upcomingmerger of TV and the computer. TheCD -I system is one aspect of it-adding computer functions to theTV set. Moving in the opposite di-rection, IBM and others are addingTV functions to the computer. InMarch, IBM will offer a TV accesso-ry for its PS/2 computers. That is anadaptor that permits the computer'skeyboard to be used to select fromamong 70 TV channels as well asthe other normal TV functions. Ofcourse, other video devices may beinput as well, including laserdiscplayers or VCR's. The TV picturemay be viewed full -screen or inser-ted in a window-there's nothinglike watching MTV while working ona spreadsheet! The IBM accessorywill carry a list price of $495, whichmay be cheap for a computer add-on. But in TV -land, the same amountwill be a 25 -inch color TV set with aremote control. R -E

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Write to Ask R -E, Radio -Electronics, 500-B Bi-County Blvd., Farmingdale, NY 11735

MOTOR SPEED CONTROLLERI have a electric model boat

and I'd like to be able to controlthe speed of the motor. The cir-cuit should be able to make themotor go from very slow to veryfast without stalling. I've tried allsorts of things but haven't hadany luck-particularly at lowspeed. The motor is powered bya 7.2 -volt battery pack. Do youhave any circuits that can helpme?-A. Balsys, Howell, NJ

Electric boats aren't my thing but Iwould have imagined that they allhad some way to vary the speed ofthe motors. Oh well, you live andlearn.

Controlling the spedd of a smallDC motor is something I've talkedabout several times before but,judging from the number of times Iget asked about it in letters and onthe phone, it seems a lot of peopleare interested in the subject. Thereare several ways to get the job doneand even some fairly inexpensivecommercial products that will do itfor you. In this case, particularly withsuch a low -voltage motor, there's aneasy circuit you can build that will dothe job and operate reliably for thelife of the motor.

The circuit I'm referring to isshown in Fig. 1. Despite its apparentsimplicity, the circuit will drive themotor over a range of speeds fromdead slow to full ahead (that's boattalk, I think), without any stalling ateven the lowest speeds. The reasonit can do this is that the circuit worksby controlling the duty cycle of themotor rather than, as in other con-trollers, the supply voltage.

Two of the inverters in the 4049are set up as an oscillator whosefrequency is roughly determined by:

F = 1/1.4RCwhere R is the total value of thepotentiometer. The two diodes iso-late both the positive and negativehalves of the output frequency andmake the output waveform stickclose to a 50-50 duty cycle allthrough its entire operating range.

The remaining inverters in thepackage are all ganged together inparallel to increase the output driveto the transistor. While you can usejust about any inverter for the cir-cuit, the 4049 is probably the bestchoice since it can handle more out-put current than other inverting gatechips. Just make sure you pay at-tention to the fact that the power pinon the 4049 is pin #1-a departurefrom the other IC's.

/4,16-6/4/9/it

/2

764100

r 41o49'

V4OTOR

4410447

0.2/cE

FIG. 1-THIS CIRCUIT WILL DRIVE asmall DC motor over a wide range ofspeeds without stalling by controllingthe duty cycle of the motor rather thanthe supply voltage.

Even though the schematicshows the supply voltage to themotor and the circuit on two sepa-rate lines, there's no reason whyyou can't use the 7.2 -volt battery forboth of them. The battery is supply-ing a perfect voltage for CMOSstuff like the 4049.

There's nothing critical about thelayout of the circuit and you canbuild it using any technique youwant. In actual fact, it's such a handy

circuit you may want to generate aprinted circuit board for it so you caneasily use the circuit somewhereelse.

WATCH THE SPEED LIMITI have an XT -compatible com-

puter and, while it works per-fectly, it's turning out to be muchtoo slow for some of the newersoftware I want to use. Is it pos-sible to speed up the computerby just changing the 14.1318 -MHz crystal and are there limitsas to how much of a speed in-crease this will give me?-F.Geeben, Hunter, IN

Before we get into this, I want tomake sure you understand that anyincrease in speed you can get likethis is going to be far outweighed bythe amount of brain damage it takesto do it. The theory is great but themaximum speed of a motherboard,like an automotive engine, is a con-sequence of how it's designed.They both have red -line numbers.

At the most basic level, the partson your motherboard were chosento match the computer's original de-sign specifications. The memory, I/Ocontroller, interrupt controller, andDMA (Direct Memory Access) con-troller have maximum speed ratingsand the ones in your computer werepicked to match the speed of theboard. The faster any chip's speedrating, the more expensive it is. I

don't know who made your mother-board but it's a safe bet that theparts on it are only as fast as theyhave to be.

Changing the crystal changes theboard's master clock and the moreyou step on the electronic acceler-ator, the closer you're going to getto the point where these chips firstget flaky and finally fail completely.The point where that happens is de-termined by the speed ratingstamped on the chips and the de-tails of the design of your mother-board.

Memory chips have a maximumspeed rating as well and it's usually

stamped on the top of the IC rightafter the chip number. A suffix of 20means 200 nanoseconds, 15means 150 nanoseconds, and soon. If the only crystal on your moth-erboard is a 14.31818 -MHz one, it'smore than likely that your computeris running, like the original IBM PC,at a speed of 4.77 MHz. This meansthat your motherboard can operatewith memory as slow as 200 nano-seconds. If that's what you have inyour machine, you don't have muchof a chance of upping the systemspeed and still maintain much in theway of reliability.

It's possible you can overcomethese problems if the design of yourmotherboard incorporates enoughwait states to do things like memoryrefresh and other housekeepingchores at an increased speed. Butthere's still another problem thathas to be considered.

There are two clock frequenciesat the expansion slots and most ofthe cards you plug into the mother-board are designed to expect thetwo clocks to be in a particular fre-quency range. Pin #B20 is knownas the CLK and on your motherboardit's probably a buffered version ofthe 8088's clock frequency -4.77MHz. That frequency can be higher,and you'll frequently find that it's ashigh up as 8 MHz.

The second frequency is the onethat can cause you a problem. In theoriginal PC (of which yours is aclone), pin #B30 was a buffered ver-sion of the crystal frequency -14.31818 MHz. That has remained astandard, even up to this day. Mea-sure the frequency at that pin on thelatest 33 -MHz 486 motherboardand you'll find 14.31818 MHz. Whenyou change the crystal on theboard, you'll also be changing bothfrequencies at the expansion slotswhich can cause a problem withsome cards that use the two clocks.

The biggest problem will comewith floppy -disk controllers sincethey use those clocks for writing tothe disk. Even if you somehow avoidthe problem, it's a guaranteed factthat you'll have problems formattingdisks.

Keeping all this stuff in mind, youcan start experimenting with higher -frequency crystals to see how faryou can go before you have major

problems. My guess is that themost you'll be able to get is a 50%increase in speed. If you want to beable to format disks, you have tosupply the computer with the origi-nal frequencies so don't get rid ofthe original crystal. Probably theeasiest way to do that is to haveboth the crystals on the mother-board and use a switch to selectone or the other.

We're talking about doing a gooddeal of work here and the possiblerewards are really minimal. A 50%increase in speed may sound like alot but you'll find that the practicaleffects are just not all that notice-able. A much better solution to thewhole problem is to buy a newmotherboard that's been designedfrom the ground up to run fasterthan the one you have now. R -E

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LETTERSWrite to Letters, Radio -Electronics, 500-B Bi-County Blvd., Farmingdale, NY 11735

VEHICLE GENERATORSAND REGULATORS

Radio -Electronics and itspredecessor, Radio -Craft, havegiven me much pleasure for 50years. Robert Grossblatt's articleshave been favorites, but he fell offthe track with his comment, "... (ve-hicle) generators and the regulatorsthat control the current they pro-duce are a really stupid chargingsystem ..." (Drawing Board, Ra-dio -Electronics, December1991).

Low-cost, high -current siliconrectifiers that made the superior al-ternator available were not de-veloped until after the transistorwas invented in 1947. There hap-pened to be a lot of high technologybefore that. Radio, TV, computers,and automobiles all pre -date thebenefits brought by advanced solid-state devices. As I recall, sub-marines, Rolls Royce automobiles,and high-speed aircraft all used gen-erators, and the electromechanicalvoltage regulators they required. I

don't believe the word "stupid"characterizes that use.

I suspect the author was just try-ing to interject some lightness-which is all right with me-but hisdescription of the operation of theolder voltage regulator is incorrect.

The generator's field current wasmodulated by a voltage -sensing re-lay that inserted various values ofresistance in the field circuit, not theoutput lead. The varying field cur-rent would then cause the outputvoltage to remain at the desired val-ue. The relay was also designed tosense the ambient temperature andchange the generator -charging volt-age accordingly. The voltage reg-ulator case usually contained acurrent -limiting relay to protect thegenerator from over -load, and a re-verse -current relay to prevent thebattery from discharging throughthe generator windings when theengine was not running.

14 These latter two functions were

not needed in the alternator, butwhen they were first installed in newcars, there were no low-cost, h'gh-current transistors developed thatcould operate at the high -tempera-tures in the engine compartment.So the same old electromechanicalvoltage regulator that had beenused for 40 years was used againwith the new alternator!

The rest of Mr. Grossblatt's arti-cle was well done and informative,as usual. I just didn't want to readyour fine magazine for the next 50years without contributing to itstechnical excellence!GEORGE W. HAILSArlington Heights, IL

TESLA COIL IMPOSTORSI have been tempted several

times in the past to write to variousmagazines after the appearance ofcertain articles on the constructionof Tesla coils. Don Lancaster's com-ments on the Tesla coil (HardwareHacker, Radio -Electronics, Oc-tober 1991) finally pushed me to fireup the word processor.

I agree that many "Tesla" coilsare essentially nothing more thanglorified step-up transformers. TheTesla coil, however, is meant to gen-erate its high -frequency high volt-age by taking advantage of thespecial properties of the resonant(quarter wavelength) transmissionline (also known, somewhat eso-terically, as the Ferranti effect). Itcan be shown that the voltageamplitude V, at the unloaded end ofan ideal (i.e., lossless, uniform, etc.)quarter wavelength transmissionline driven by a source of resonantvoltage of amplitude Vs, and of im-pedance Zs at the resonant fre-quency(assumed real for notationalsimplicity) is V= (Zo/Zs)Vs, whereZo is the characteristic impedanceof the line. This is different in numer-ous ways from the standard voltagemultiplication of a transformer, as itshould be; these are quite distinctphysical phenomena.

Although the physics of the trans-former is pretty amazing, what ismore impressive is that a wire (or,more properly, a transmission line)may itself act as a "transformer." Agreat experiment that shows this isthe construction of a mock trans-mission line using discrete compo-nents to model (mock) thedistributed parameters of a realtransmission line.

In reality, a Tesla coil impostor ispretty easy to spot. It will suffer froma variety of maladies, some of whichinclude improper magnetic coupling(making it a transformer instead of apropagating transmission line) and amarked insensitivity to resonant fre-quency tuning. Generally, even themost heinously constructed "Teslacoils" will generate hefty attention -grabbing sparks, but they are oftenmissing the "magic and mystery" ofthe physics of the resonant line thatmakes it a true Tesla coil.MATTHEW KLEJWASchaumburg, IL

HERE'S TO HOW-TO ARTICLESI'm writing in response to Alex

Funk's letter (Radio -Elec-tronics, April 1991) titled "Mac -Hack Attack." It might be true that ifyou add up all the components re-quired for a home -built computersystem, the final price tag will comeclose to a dealer -bought system.However, there are quite a few peo-ple in this world who cannot affordto shell out over $1000 at one time,but who can afford to do it piece bypiece. It's a lot easier to spend $25or $50 at a time than it is to spend$1000.

And how can you put a price onyour time when you are learning howto build something as useful as acomputer system? How much isyour time worth when you sit andwatch television?

Please keep publishing thosehow-to articles!JOHN CULLIVANNiles, OH

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EQUIPMENT REPORTSThe Kelvin 100K Digital Multimeter

Most multimeters areready to use

right out of the box-but not the Kelvin 100K.


If we were to tell you that thisreview is about an inexpensivemultimeter, you'd probably be in-

clined to turn to the next page. Afterall, multimeters are as common to-day as silicon chips, and the fea-tures found on inexpensive oneshave been around for years. Sowhat can we tell you about theKelvin 100K digital multimeter thatyou couldn't already guess? The an-swer is that it's available as a kit.

The Kelvin 100K (Kelvin Elec-tronics, 7 Fairchild Ave., Plainview,NY 11803) comes with a PC boardand all parts that mount on it, a casewith a backstand (that's alwayshandy), a pair of test leads, anowner's manual, an assembly man-ual, an extra fuse, and even a 9 -voltbattery, all for $29.95. The 100Ksfeatures include a 31/2 -digit LCD;DC ranges of 2, 20, 200, and 1000volts; AC ranges of 200 and 500volts; resistance ranges of 200ohms, 2K, 20K, 200K, and 2megohms; and DC current rangesof 2 mA, 20 mA, 200 mA, and 10amps. There's no provision for mea-suring AC current.

The 100K also hosts a diode test,a low -battery indicator, and a batterytest-a handy feature for a general-purpose multimeter. In the "batterytest" mode, the meter will displaythe voltage of any 1.5 -volt batteryunder a 100-mA load or the voltageof any 9 -volt battery under a 6-mAload.

16 It's likely that not too many experi-

enced kit builders will be interestedin building the 100K, mainly becausethey almost certainly already own amultimeter. However, the 100K kit isperfect for any beginner in elec-tronics or a child who's old enoughto attempt soldering-especially akid who's always playing with hisdad's multimeter!

The assembly manual is par-ticularly well -suited for a classroomenvironment, as it reads like an elec-tronics lab manual; parts are in-stalled a small group at a time,alternating with precautionary cir-cuit checks, explanations of howeach section of the circuit works,troubleshooting tips, and variousquizzes on what has been coveredso far.

Experienced kit builders may ac-tually find the assembly manualsomewhat irritating, because thesections in which components areinstalled are scattered throughout alot of other explanatory paperwork.Remember though, that the kit isaimed at beginners. But this iswhere the kit's one flaw emerges:the assembly manual contains morethan just a few typographical errors.A seasoned kit builder should beable to overcome these problemsbut they may be very confusing tothe beginner. Let's go over the as-sembly manual and point out anyproblems we encountered.

The manual starts out with an in-troduction to the meter and a tablelisting all of its specifications. A

schematic of the meter's circuitryand a parts list follows. Diagrams ofall of the parts are provided to helpyou quickly identify everything. Aparts -placement diagram is next, al-though the PC board issilkscreened with all of the compo-nent designations as well. Also in-cluded are charts to help youidentify resistor values by their colorcodes and capacitor values by theirnumbering. Pinout diagrams areprovided, of the 31/2 -digit LCD, the7106 A/D converter, and the quadXOR gate used in the meter. There's abrief discussion on proper solderingtechniques and the proper handlingof IC's. A list of all tools needed tobuild the meter is also given. Circuittheory is the last thing to be coveredbefore the actual assembly of theboard begins.

In the first assembly procedure,certain resistors and capacitorsmust be soldered to the PC board,and some might find this step con-fusing. You are instructed to installC14, 10 nF, and C16, 0.01 µF-butthe two capacitors are actually thesame value. And the fact that theparts list shows capacitors C14 andC16 to be "0.0 µF" only adds to theconfusion.

Next you have to install the 40 -pin7106 IC so that the A/D circuitrycan be tested out, which also re-quires the temporary installation ofthe battery clip, the LCD, and therotary knob. The LCD and knob re-quire a bit of sub -assembling beforeattaching them to the meter, and forsome reason the sub -assembly in-structions are found much fartheron in the manual. The assembly di-agram shows the back of the rotaryknob as having six plastic tabs overwhich you are to snap on six metalcontact clips-but the knob thatcame with our kit had seven tabs.After putting the clips on the sixoutermost tabs, the A/D sectionseemed to work just fine.

For the voltage -reference circuit,continued on page 90

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CABLE/TV SIGNAL LEVELMETER. Designed for mea-suring performance levelsduring system con-struction, installation, andmaintenance, Leader In-struments' Model 951CATV signal -level metercan be used by the broad-cast -TV, FM, MATV, andCATV industries. It has anauto -scanning feature thatselects 32 channels en-countered and displaysmeasurement results thatare auto -ranged and auto -scaled for storage to (or re-call from) four groups ofeight channel-bargraph

data registers. Users canalso select and store fourmemory -scans of pictureand/or sound carriers, andmeasured results. Single -or multi -channel displayscan be selected, using dig-ital readouts and analogbargraph indications on alarge, backlit, supertwisted

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LCD readout. The Model951 provides continuousfrequency coverage from48 to 870 MHz. It featuresEEPROM look -up tablesfor picture and sound car-riers in broadcast VHF,UHF, and CATV standardsof 16 countries. The bat-tery -powered (8 "D" -sizecells) unit measures8.4 x 4.75 x 7.9 inches andweighs just 10.5 pounds.An optional RS -232 inter-face allows data to bedownloaded to a printer orcomputer.

The Model 951 Cable/TV signal -level meter costs

$1695. Leader Instru-ments Corporation. 380Oser Avenue, Hauppauge,NY 11788; Phone:1-800-645-5104 (in NY,516-231-69000).

SCHEMATIC DRAWINGSOFTWARE. Developed tohelp engineers, techni-cians, and hobbyists de-sign and draw electroniccircuits on -screen,AutoSkem CAD Version1.4 produces a high -qualityprintout, eliminating therough hand -drawn sketch.

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Drawings can be con-structed using lines, text,and symbols. A software li-brary of more than 50 pre-defined electronic sym-bols, logic gates, op -amps,transistors, diodes, coils,etc., is included. Users cancreate their own symbolsand organize them into anunlimited number of librar-ies of up to 100 symbolseach. Text can be rotatedand scaled to five sizes be-fore being placed in a draw-ing. Version 1.4 featuresimproved graphics anddrawing features for EGAand VGA systems; "rub-ber -banding" for drawing

48 HOURSHIPPING

ELENCO & HITACHI PRODUCTS TO ORDERCALL TOLL FREE

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Hitachi RSO Series(Portable Real-time Digital Storage Oscilloscopes)VC -6023 - 20MHz, 20MS/s $1,695VC -6024 - 50MHz, 20MS/s $1,995VC -6025 - 50MHz, 20MS/s $2,195VC -6045 - 100MHz, 40MS/s $2,995VC -6145 - 100MHz, 100MS/s $4,495

RSO's from Hitachi feature roll mode, averaging, savememory, smoothing, interpolation, pretriggering; cursormeasurements. These scopes enable more accurate,simplier observation of complex waveforms, in addition tosuch functions as hardcopy via a plotter interface andwaveform transfer via the RS -232C interface. Enjoy thecomfort of analog and the power fo digital.

25MHz Elenco Oscilloscope$349S-1325

Dual Trace 1 mV Sensitivity

6" CRT X -Y Operation

TV Sync (2) 1X, 10x Probes included

SPECIAL BUYV-212 - 20MHz Scope $425

Hitachi Portable ScopesDC to 50MHz, 2 -Channel, DC offset func-

tion, Alternate magnifier functionV-525 - CRT Readout, Cursor Meas. $995V-523 - Delayed Sweep $975V-522 - Basic Model $875V-422 - 40MHz $775V-223 - 20MHz delayed sweep $695V-222 - 20MHz deluxe $625

PRICE BREAKTHRU20MHz Digital Storage Oscilloscope

Analog/Digital Scope 2K word per channel memory DS203 toMS/s sampling rate $795 State -of -art technology Includes probes

HITACHI COMPACT SERIES SCOPESThis series provides many new functions such as CRTReadout, Cursor measurements (V-1085/1065A/665A), Fre-quency Ctr. (V-1085), Sweeptime Autoranging, Delayedsweep and Tripper Lock using a 6 -inch CRT.You don't feelthe compactness in terms of performance and operation.

V-660 - 60MHz, Dual Trace $1,149V -665A - 60MHz, DT, w/cursor $1,345V-1060 - 100MHz, Dual Trace $1,395V -1065A - 100MHz, DT, w/cursor $1,649V-1085 - 100MHz, QT, w/cursor $1,995V -1100A - 100MHz, Quad Trace $2,195V-1150 - 150MHz, Quad Trace $2,695

Elenco 40MHz Dual TraceGood to it 495

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High luminance 6" CRT 1 mV Sensitivity

10KV Acceleration Voltage 17ns Rise Time

X -Y Operation Includes (2) lx, 10x Probes

All scopes include probes, schematics, operators manual and 3 year (2 yrs for Elenco scopes) world wide warranty on parts & labor. Many accessories available for all Hitachiscopes Call or write for complete specifications on these and many other fine oscilloscopes. lx, 10x Scope Probes: P-1 65MHz $19.95, P-2 100MHz $26.95

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GF-8015 without Freq. Meter $179

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Triple Power Supply XP -620Assembled $69

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Provides sine, triangle, squarewave from 1Hz to 1MHz

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Wide Band SignalGenerators

SG -9000 $129RF Freq 100K-450MHz AM Modula-

tion of 1KHz Variable RF output

SG -9500 vd Digital Display &150 MHz built-in Counter $249

Muttimeter withCapacitance &Transistor Tester

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Current, Capacitors,Transistors and

Diodes / with caseBig 1" Display

AM/FM TransistorRadio Kit

with Training Course

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Makes a great school project

FLUKEMULTIMETERSAll Models AvailableFluke 70-11 $65Fluke 77-11 $145Fluke 79-11 $169Fluke 87 '$289Call for special price

True RMS 4 1/2

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XK-500 / Analog TrainerA complete mini -lab for building, testing, prototyping analog and digital circuitsElenco's Digital / Analog Trainer is specially designed for school projects, with 5 built-in powersupplies. Includes a function generator withcontinously variable, sine, triangular, square waveforms. All power supplies are regulated and protected against shorts.Power Supplies Variable Power Supply +1.25 to 20VDC @ .5 Amp

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840 tie points (total 1,680)

$149.95 Assembled$119.95 Kit

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straight or diagonal lines;the ability to save the draw-ing configuration file withall current program drawingconfigurations; improvedmouse support; and inter-nal high -resolution printerdrivers for 9- and 24 -pin dotmatrix and HP LaserJetprinters, and HP Pen Plot-ters. Parallel as well as se-rial interfaces are sup-ported. The program re-quires an IBM PC, XT AT,PS/2, or compatible com-puter running DOS 2.1 orhigher; 384K RAM; andCGA, EGA, VGA, or Her-cules graphics.

AutoSkem CAD Version1.4 costs $49.-BSOFTSoftware, Inc., 444 ColtonRoad, Columbus, OH4 3 2 0 7 ; Phone:1-800-728-3805

CARTOON -A -DAY PRO-GRAM. A PC -calendar pro -


gram with a twist, theCartoon -A -Day CalendarPlus from Individual Soft-ware offers DOS and Win-dows users a daily dose ofwhimsical humor in theform of the farcical drawingof nationally syndicated"Inside Out" cartoonistKevin Pope. The daily car-toon can be added to per-sonal calendars, printedcorrespondence, daily to-do lists, or schedules. Theprogram displays (and

prints) personal scheduleinformation by the day,week, month, or year, andeven keeps track of vaca-tion time, personal plans,travel time, and holidays. Itcan also be used to createor update to-do lists. Bothversions feature digital andanalog clocks; the Win-dows version also featurestime -saving "QuickMemo" and "Quick Fax"functions that generate amemo or fax cover sheetthat incorporates the dailycomputer right from theircomputer. The DOS ver-sion runs on any IBM-com-patible PC with DOS 3.3 orhigher and 512K of memo-ry. The Windows versionrequires Windows 3.0 soft-ware.

The Cartoon -A -Day Cal-endar Plus program (forDOS or Windows) costs$29.95.-Individual Soft-

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Portable IC Color Pattern GeneratorIN Battery operated, compact portable unit 13 patterns including gated rainbow CH 3/CH 4 output crystal controlled Composite video output to 1 Vp-pIN Progressive scanModel 1211C $229

NTSC Signal Generator NTSC color bars, with or without IWQIN Linear staircase with high or low chromaMI Multiburst External video, external audio

Interlaced scanModel 1251 $1,195

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NTSC Generator with RGB NTSC color bar pattern 1 Vp-p or variable composite video output RGB outputs on BNC or 9 -pin D -type

subminiature connector Composite sync, vertical sync, and

horizontal sync outputsIII Interlaced or progressive scanModel 1249A $558

Deluxe NTSC Video Signal GeneratorIII High accuracy NTSC color bars TCXO master oscillator RGB, Gen Lock, Circle, and Black Burst Multiburst to 8 MHz, 1000/0/50% level Interlaced or progressive scanModel 1260 $1,995

Start working smarter! For details on the complete line of B+K PRECISIONvideo generators or for immediate delivery, contact your local distributor or:

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ROBOTIC PROBE. Aimed atthe electronic service in-dustry, where low -volumeboards, varying devicetechnologies, and a widerange of repair problemsexist, the Prober RP388 isa computer -controlled,electro-mechanical probethat automates the testingprocess for components ofvarious sizes and packag-ing, including surface -


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mount devices. Accordingto Huntron Instruments,the robotic probe can setup and test any kind ofcomponent on a printed -circuit board faster thanusing a conventional "bed -of -nails" test system.

The Prober RP388,which requires the 5100DStroubleshooting system foroperation, consists of aprecision electro-mechan-ical probe and a software -controlled video -imagingsystem. The probe can bedriven to the test point withapproximately ± 4 -mils ac-curacy, and the imagingsystem shows a detailed,real-time image of theboard on the PC monitor.Establishing a test routineand troubleshooting is athree -step process usingthe combination of the5100DS and the ProberRP388: Teach the Prober

the test -point locations;learn and store signaturesof good components; andfind faulty components byautomatically comparingtheir signatures to the sig-natures stored on the PChard drive. On average, aPCB with 39 surface -mount devices (14 to 20pins per component) canbe tested in less than 10minutes.

The Prober RP388 costs$23,000; the 5100DS sys-tem required to operate itstarts at $10,000.-Hunt-ron Instruments Inc., 15720Mill Creek Blvd., MillCreek, WA 98012; Phone:800-426-2965 or206-743-3171; Fax:206-743-1360.

DIGITAL VOICE CHIP SET.Electech Electronics'VCS -1870 allows circuitdesigners to easily add dig -


itized voice to their de-signs. The set consists ofthe 40 -pin DIP VP -1870voice -processing chip andthe 21 -pin SF -700 filtermodule board. The chipfeatures CVSD encodingat variable sampling ratesfor natural -sounding voicedigitization. Its 8 -bit bi-di-rectional interfaces is com-patible with most micro-processors. Digitized voicedata is stored in externalRAM or ROM. The SF -700is an active band-pass(300 -Hz to 3.4 -kHz) filtermodule with pre -amp for

microphone or line inputsignals. Specially designedto work with the VP -1870, itprovides good voice qualityand high reliability withgreatly reduced compo-nents count, board space,and power consumption.Operation requires a single3- to 6 -volt DC power sup-ply.

The VCS -1870 digitalvoice chip set costs $16 inquantities of 1000.-Elec-tech Electronics, 1262 EastKatella Avenue, Anaheim,CA 92805; Phone:7 1 4-3 8 5-1 7 0 7; Fax:714-385-1708.

DIGITAL MULTIMETERS. Anenhanced line of low-cost,pocket -sized digital multi -

meters from Beckman In-dustrial include featuresordinarily found only inmore expensive units. Forinstance, Models DM5XL,

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DM1OXL and DM1OXLeach offer 10 -amp currentfusing to protect both theuser and the meter, safetytest leads with shroudedinput plugs and text points,a warning beeper when thetest leads are placed in thewrong input jacks, largeLCD numerals, and in-creased battery life. Allthree meters measure DCvoltage to 1000 volts, ACvoltage (to 500 volts for theDM5XL and to 750 voltsfor the other two), resis-

tance, and diode test, andhave a continuity beeper.Model DM1OXL adds a fea-ture called the "SafetyTester- which detects anddisplays commonly en-countered AC and DC volt-age levels from 6 to 220volts. This feature workseven when the DMM bat-tery is dead, ensuring thatthe user can always safelydetect the presence of livevoltage levels. ModelDM15XL also adds a logic -measurement function thatindicates the presence andpolarity of TTL pulses up to20 MHz.Models DM5XL, DM1OXL,and DM15XL digital multi -meters cost $34.95,$44.95, and $59.95, re-spectively.-Beckman In-dustrial Corporation, 3883Ruffin Road, San Diego,CA 92123-1898; Phone:619-495-3218.

SEMIANALYZER SIGNALTRACER. The EDS-59CSemianalyzer II from Elec-tronic Design Specialistsallows the technician totrace audio, video, digital,or FG signals to the prob-lem area, while simulta-neously monitoring DCvoltages along the way onits 31/2 -digit voltmeter.Once the technician is in

the suspected area, the in-strument will check semi-conductor devices in circuitand display the type, polar-ity, and condition of the de-vice in plain English. Dif-ferent tones beep to


indicate various problems.The Semianalyzer 11 alsochecks Zener diodes fortheir proper voltages, aswell as neons, LED's, andcapacitors for leakage,noise, and voltage break-down up to 175 volts DCusing a built-in "Hi -Pot"tester. For repairing remotecontrols, an optional in-frared detector probe isavailable. TheSemianalyzerlIcomes witha three-year limited warran-ty and a 60 -day money -back trial period. It is alsoavailable in kit form, withoutthe 60 -day trial period.

The Semianalyzer 11costs $399 fully as-sembled, and $299 in kitform, with cabinet.-Elec-tronic Design Specialists,Inc., 275 Rock Island Road,North Lauderdale, FL33068; Phone or Fax:305-720-4497. R -E

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The ER -4 PHOTO ETCHm KIT gives you the tools, materials and chemicalsto make your own circuit boards from the artwork printed in magazines likethis one. You can also do original 1X art using the enclosed patterns, tapesand drafting film. Or try the DIRECT ETCH -RI system (also included)to makesingle circuit boards without artwork.You'll need a reflector photoflood and a UV light source (or sunlight). Whysearch? Get an ER -19 bulb set with your ER -4. Bulbs use an ordinary 120Vsocket. The ER -4 and ER -19 are stocked by electronic parts distributors ororder direct. Add $4.50 for shipping. NV and CA residents must add sales tax.ER -4 PHOTO ETCH SET $38.00ER -19 LIGHT BULB SET 16.45

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YOUR NATURAL RE-SOURCE: 1992 ANNUAL CAT-ALOG; from Jameco Elec-tronic Components andComputer Products, 1355Shoreway Road, Belmont,CA 94002; Phone:800-831-4242; Fax:800-237-6948; free.

This year's catalog fromJameco, printed on re-cycled paper, carries thetheme "Your Natural Re-source." Intended as acomplete source book forelectronics hobbyists andcomputer enthusiasts, the90 -page, full -color catalogincludes descriptions ofmore than 3000 products,


from electronic compo-nents to test and measure-ment equipment, from ca-bles to complete computersystems. Other features ofthe catalog include educa-tional information and aRAM cross-referenceguide. To further assistcustomers in making pur-chasing decisions, Jamecooffers 24 -hour toll -freeorder placement and toll -

free fax and BBS service.

TECHNI-TOOL CATALOG 41;from Techni-Tool Inc., 5 Ap-ollo Road, P.O. Box 368,

Plymouth Meeting, PA 19462;Phone: 215-941-2400; Fax:215-828-5623; free.

The 240 pages of thiscatalog are filled with an as-sortment of tools, tool kits,and test equipment that in-cludes more than 18,000items from 850 manufac-turers. Electronics profes-sionals and hobbyists willfind items ranging fromelectro-mechanical and as-sembly devices to elec-tronic, telecommunication,and field -service tool kits.Also featured are full linesof tools, equipment, andaccessories for computermaintenance and for thefast-growing field of sur-face -mount technology.Static control and clean -room items are included.Several new items are high-lighted, including 100 -MHzmonolithic oscilloscope


probes, the ESD heat gun,the Fluke 88 AutomotiveMeter, and the kit bag withconductive plastic cabinetsfor easy carrying of smallelectronic parts.

TEST INSTRUMENTS ANA-LOG & DIGITAL; from Sim-pson Electric Company, 853Dundee Avenue, Elgin, IL60120-3090; Phone:708-697-2260; Fax

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catalog features Simpson'slines of hand-held andbenchtop multimeters,


special function meters,clamp -on testers, andother specialized testersfor electrical, electronic,and environmental applica-tions. In addition to thatequipment, the catalogcovers special -functionohmmeters, voltmeters,and ammeters; insulationand temperature testers;testers for microwave andAC current leakage; andsound- and noise -measure-ment instruments and tele-phone -industry test sets.Capsule descriptions ofeach item, along with listsof features, ordering infor-

continued on page 87

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THE TECHNOLOGY TO PRODUCEIOW -cost digital docks has ex-isted for years. Unfortunately,the style in which these clockshave displayed the time hasbeen mostly limited to four dig-its (representing hours andminutes). Few digital clocks, ifany, have taken full advantageof the great capabilities of to-day's microprocessors to pro-vide a more novel display . . .

that is until the HyperClock.The HyperClock has a

custom -programmed micro -controller that generates all thesignals necessary to displaytime in eight eye-catching (yeteasily readable) modes. Amongits features are the ability tosimulate a sweep second handwith a ring of 60 LED's; it cangraphically display the level ofocean tides; it has a "fading"display mode that causes theLED's to gradually change whenupdated; it has a hourly chime/alarm output; supports 50- or60 -Hz powerline operation; ithas a battery backup; and anintelligent date display thatknows the last day of eachmonth. Let's take a look at thosefeatures in greater depth.

The digital displayIn four of the HyperClock's

eight modes it can display timewith a clever twist that those ofyou that grewup before the "dig-ital -clock revolution" will appre-ciate. You may recall that it wasfairly common for folks to speakof how many minutes it was tillthe next hour. For example, peo-ple would say "it's ten beforefive" rather than "it's four -fifty."Well, the HyperClock can actu-ally "display" the time in thatmanner.

lb help explain how that isdone, take a look at Fig. 1-a; itshows the six seven -segmentLED displays that are used toform the clock's digital display.During the first 30 minutes ofeach hour, the two middle digitssignify the hour and the right-most digits indicate minutespast the hour (like most digitalclocks), and the two digits onthe left are blank. Figure 1-bshows how eleven fourteen (orliterally "fourteen after eleven")would look in this mode.

BUILD THE

ri-tr-eir

Build a digital clockthat's way ahead of its time!

LEON W. SCHMIDT

However, once the clock ad-vances to beyond half -past thehour, the right digits go blank,the middle display would incre-ment to display the next hour,and the left two digits would in-dicate how many minutes areleft until that hour. For exam-ple, if it was thirteen minutes totwelve (or 11:47), the displaywould look like Fig. 1-c. Youcould read that literally as "thir-teen before twelve."

On the hour, the clock just

displays the hour, so the left andright minute displays remainblank (see the display for 12o'clock shown in Fig. 1-d).

As mentioned earlier, thereare 60 LED's arranged in a circleto display seconds or an approx-imation of the current tide levelin your locale. The LED's act as alight chaser sweeping throughthe seconds of a minute. Theycan also show the relative tidelevel by moving from the 12o'clock position at high tide to 33

the 6 o'clock position at lowtide. The timing of the tide -in-dicator mode is set to displaytwo complete tide cycles in24.51 hours just as it should.(For more on this subject see thesidebar entitled "A Bit AboutTides.")

Fading -out the digitsThe HyperClock also differs

from other clocks in how it up-dates its display. In typicalclocks, the display digitsabruptly change as time passes.However, in four of HyperClock'seight modes when a digit mustbe updated, the LED segmentsrepresenting its old value are di-mmed as the segments for thenew value become brighter.Likewise, each LED in the lightchaser fades off rather thanturns off. This animation israther relaxing to watch.

These display effects are ac-complished by a mixture of mul-tiplexing and duty -cycle modu-lation. The seven -segment dis-plays are all common -anodetypes, so each digit has its ownanode -driver transistor. In typ-ical multiplexed -display fash-ion, the cathodes of correspond-ing segments of each digit areconnected together and share acommon driver.

Like any other multiplexeddisplay when the segment datafor a digit is placed on the seg-ment data lines, the anode driv-er for that digit is activated, andthe seven -segment displaylights to exhibit the appropriatedigit. All the other digits are offat this time. After a short periodof time (1.83 ms) the segmentsare turned off via the segmentlines and the anode driver is de-activated. The anode driver forthe next digit is then activated,the segment data for that digitis placed on the segment lines,and the process continues untilall the digits have been lit. Sincethe human eye is too slow to seethe digits turn on and off, it ap-pears as though they are all onsimultaneously. Multiplexingthe digits in this fashion re-duces the number of pins on themicrocontroller needed to con-trol the LED displays.

HyperClock's fading effect is34 created by modulating the duty

nu uA

C

N

FIG. 1-HYPERCLOCK'S TIME DISPLAY (a) is unique in that it not only displays timenormally (b), but it can indicate minutes left to the next hour (c), and blanks the minutedisplays on the hour (d).

cycle of the segment enable sig-nals. When a seven -segmentdisplay is enabled, the segmentdata lines spend part of the timein states corresponding to thecurrent digit to be displayed,and the rest of the time in statescorresponding to the next or"future" digit that will be dis-played. Each time the digit isenabled, the duty cycle will favorthe future -digit data more andmore, until only the new digit isdisplayed, and the process re-peats each time the displaymust be updated.

The microcontrollerAt the heart of the HyperClock

is an Intel 8749 microcontroller.It is programmed to perform avariety of functions, namely:display multiplexing, time-keeping, receiving switch in-put, coordinating the hour andalarm chime, and initiating apower -fail mode that permitsthe time -keeping functions to

continue while blanking thedisplay to conserve backup -bat-tery power.

The 8749 has 2K of EPROM,128 bytes of RAM, 24 I/O pins, aprogrammable 8 -bit timer, andan interrupt -control structure.The custom -program placed inthe processor to create Hyper -Clock's special effects exten-sively exercises all of the chip'sfeatures; Fig. 2 contains a sim-plified flow chart for the Hyper -Clock program. The program isshown divided into two sec-tions: an interrupt routine anda main loop.

The interrupt routine ismainly responsible for takingthe segment data from the seg-ment -data buffer in the micro -controller and placing it on thedisplay -control lines in a multi-plexed fashion. The interruptthat initiates the routine comesfrom the 8749's internal timer,which has been programmed toexecute the interrupt every 1.83

INTERRUPT ROUTINE MAIN -PROGRAM LOOP

START INTERRUPT ROUTINE

AFTER EVERY 1.83ms

SI ANK DISPI AY

F SEGMENT DATA

UPDATE LED DISPLAY FROM FROM BUFFER

THE SEGMENT DATA BUFFER 1

ENABI I NEXT DISPLAY 01011

SAMPLE LINE CYCLE FROMLINE INPUT

ENDRETURN TO MAIN PROGRAM

r 1I SEGMENT I

DATA

I BUFFER I

SEGMENT DATATO BUFFER

INPUT LINE CYCLECOUNTED FROM INTERRUPT

DISPLAY MULTIPLEXROUTINE

YES

NO

UPDATE TIME COUNTERS

DOES THE DISPLAYNEED TO BE UPDATED?

YES

UPDATE LED SEGMENTDATA BUFFER

INPUT KEY SWITCH ROUTINESFOR PROGRAMMING CLOCK

OPERATION

CHIME SOFTWARE FUNCTIONS

ALARM SOFTWARE FUNCTIONS

FIG. 2-HYPERCLOCK'S SOFTWARE can be broken down into two distinct codesegments: a clock -scheduled interrupt routine, and a main -program loop.

ms. Using an interrupt -pro-gram segment in this way al-lows the display's fading effectto appear gradual because theprocess of updating the displayoccurs at regular intervals. Thisroutine is also responsible forchecking a powerline-frequencyinput on the microcontroller todetermine if a powerline cyclehas passed. If so, it informs themain loop of the program.

The main loop keeps track ofthe number of cycles that passso it knows when to update thesegment -data buffer or initiatethe alarm or chime. If nopowerline cycles are detected,the main loop assumes ACpower has been terminated andputs the clock in power -fail

mode. In that mode it shuts offthe display and allows the mi-crocontroller to "invisibly" keeptrack of time via a 6 -MHz crys-tal. The main loop also pro-cesses input from the clock'sswitches (we'll talk more aboutthat later).

For all that goes on inside themicrocontroller, the functionsassigned to its pins by the Hy-perClock program (see Fig. 3)are relatively easy to under-stand. Let's take them onegroup at a time.

The pins labeled A throughand DP (pins 12-19) in Fig. 3 arethe outputs for the display -seg-ment data. They indirectly con-trol the cathode drivers for themultiplexed display. Similarly,

X1

3X2

12

4 13RESET B

5,26,49 14+5 VOLTS

1550/60 D

6 16LINE

27 17SW1

SW2

874928 18

29 19SW3 DP

30 21SW4 DEO

31 22SW5 DE1

32 23SW6 DE2

33 24SW7 DE3

34 35CHIME DE4

7,20GROUND

FIG. 3-THE PINS ON THE 8749 micro-controler are assigned various func-tions by the HyperClock program.

the outputs labeled DEO-DE4(pins 21-24 and 35) control theanode drivers for the display viademultiplexer chips, whichwe'll discuss later.

The pins labeled si-s7 (pins27-34) are used as function -switch inputs. The switchesconnected to those inputs(DISPLAY MODE, DISPLAY DATE, DIS-PLAY ALARM, INCREMENT HOUR/MONTH/MODE, INCREMENT MINUTE/DAY, SNOOZEMDE ADVANCE, andALARM TOGGLE, respectively) ac-tivate various chip functions bygrounding those pins. A com-plete explanation of the switch-es' functions will be presentedlater.

Low -going pulses from thepin labeled CHIME (pin 34) acti-vate the chime circuit, which iscomposed of discrete compo-nents. The microcontroller trig-gers the chime circuit with a12.8 -ms wide low -going pulse atone -second intervals. When notin alarm mode, the chime sig-nals the hour by chiming an ap-propriate number of times, andsignals each half-hour by chim-ing once.

When the microcontroller isin the "alarm" mode, the chimecircuitry is used as an alarm an-nunciator. In this mode theclock does not chime on thehour and half hour. That per-mits you to use the HyperClockas an alarm clock without thechimes disturbing you until theappointed time. 35

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FIG. 4-THE HYPERCLOCK DISPLAY is controlled by only 13 data lines from themicrocontroller.

The LINE input (pin 6) is usedby the IC to accept a 50- or 60 -Hz square wave. The squarewave is used for time keepingand to detect AC -power failureas mentioned earlier. The50Hz/60Hz input (pin 1), tellsthe 8749 what frequency to ex-pect at the line input. If pin 6 islow, the 8749 assumes the linesignal is at 60 Hz, but if that pinis high the 8749 prepares for50 -Hz operation.

As its name implies, theRESET input (pin 4) initializesthe microcontroller. A low atthat input will erase all modesand settings previously entered.

The xi and X2 inputs (pins 2and 3) need to be connected tothe 6 -MHz crystal, XTAL1, men -

36 tinned previously. Last, but cer-

tainly not least, are the 5 -voltpower inputs (pins 5, 26, and40) and the grounds (pins 7 and20). Those inputs of course, areself explanatory.

The display circuitWhile the microcontroller

does a great deal, the Hyper -Clock requires some additionalcircuitry to make it a completetimepiece. For example, the mi-crocontroller cannot providenearly enough current to drivethe LED display. For that reasonadditional anode and cathodedrivers were included in the de-sign. They are shown along withthe other display componentsin Fig. 4.

The control signals for theLED cathodes originate from

the A-G and DP pins of the micro -

controller. The A-G signals aresent to a ULN2003 buffer/driver(IC7) which contains sevenhigh -current drivers. Each out-put is capable of providing 500mA of peak drive current. Sincethe ULN2003 contains onlyseven of the eight cathode driv-ers required, a Darlington driv-er was made out of two 2N2222transistors to drive the DP line.

The DEO through DE4 outputsgenerated by the micro -controller are decoded by two74LS145 decoder/driver IC's(IC5 and IC6). Only one decoderoutput is driven low at any time.Each 74LS145 output suppliescurrent to a 2N2907 drive tran-sistor that sources current forthe anodes of a group of LED'sor a display digit.

Note that there are additionalLED's to provide an AM/PM in-

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FIG. 5-THIS SCHEMATIC DIAGRAM FOR THE HYPERCLOCK circuit (less the displaycomponents) shows the support circuitry required by the microcontroller.

dication (LED61), tell you if thealarm -mode is active (LED62),and provide a winking seconddisplay (LED63 to LED65).That's all there is to the displaycircuit.

The remainderThe most noteworthy of the

clock's remaining circuitry(shown in Fig. 5) is the chimecircuit. When the micro -

controller generates a low -goingpulse on pin 34, it activatesQ19. That transistor then pro-vides sufficient current to driveQ1 into saturation.

With Q1 on, the negative sideof C13 is effectively grounded,which causes it to charge. WhenQ1 is turned off, C13 dischargesthrough a 470K resistor (R13).The resistor/capacitor com-bination has a time constant of

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0.47 seconds. The exponen-tially decaying signal producedby the discharge is bufferedthrough a unity -gain amplifier(IC3-a) to a 1N914 diode (D3).

The cathode of D3 is con-nected to the output of a 50%duty cycle 5 -kHz square -waveoscillator consisting of IC2-a,R7, C10, and Q2. Transistor Q2serves to provide a dynamicpull-up for that oscillator sincethe LM393 is an open -collectortype comparator. The 5 -kHz 37

All resistors are 1/4 -watt, 5%, unlessotherwise indicated.

R1, R6 -R8, R10 -R12, R16, R17-47,000 ohms

R2, R3, R5, R14, R15, R18 -R32,R41 -R57-4700 ohms

R4, R13, R58-470,000 ohmsR9-2700 ohmsR33 -R40-330 ohms, 1/2 -watt, 5%

CapacitorsC1, C2-20 pF ceramicC3-1000 j.LF, 16 volts, electrolyticC4, C5, C15, C16-0.1 tiF, ceramicC6-22 p.F, 16 volts, electrolyticC7-2.2 p.F, 16 volts, electrolyticC8, CO 0.01 1.1.F, ceramicC10, C14, C17-0.0033 p,F, ceramicC11, C12-560 pF, ceramicC13-1 j.LF, 16 volts, tantalum

SemiconductorsIC1-LM340T-5 5 -volt regulatorIC2-LM393 dual -comparator

square wave present at theemitter of Q2 is clamped in am-plitude by the buffered expo-nential waveform from IC3-a, sothe 5 -kHz signal decays in am-plitude in step with the dis-charge of C13.

The decaying 5 -kHz signal isfed through C14 to a second -order low-pass filter tuned to ap-proximately 5 kHz. The filter iscomposed of a LM324 op -amp(IC3-d), C11, C12, C14, R10, andR11. It removes the high -fre-quency components containedin the decaying square wave tosmooth it out. From there thesignal is passed to two more op -amps (IC3-b and IC3-c) thatform a push-pull amplifier,which provides the piezo trans-ducer with a 10 -volt peak -to -peak drive signal.

While the output signal is notexactly a pure sine wave, the au-dible result sounds pretty muchlike a small bell. If you feel thechime is too loud, you can elimi-nate half of the push-pull ampli-fier by jumpering one side of thetransducer to the 5 -volt supply,which is available via JU2.

The entire circuit receivespower from a 9 -VAC wall -mounttransformer. The 9 -VAC supplyis fed to a full -wave bridge rec-tifier and filtered by C3 to act as

38 an unregulated 12 -volt DC sup -

PARTS LIST

IC3-LM324 quad -op -ampIC4-8749 microcontroller with Hyper -

Clock programIC5, IC6-74LS145 1 -of -8

decoder/driver1C7-ICLN2003 high -current driverD1, D3-1N914A diodeD2 -1N4001 diode01, 02, 017, Q18 -2N2222 NPN

transistorQ3-016, Q19 -2N2907 PNP transistorBR1-1-amp, 50 volts PIV bridge

rectifierDISP1, DISP3-Panasonic LN524RA or

similar 7 -segment display (for thesmaller digits)

DISP2-Panasonic LN526RA or similar7 -segment display (for the larger digit)

LED1-LED65-light-emitting diodesOther componentsXTAL1-6-MHz crystalT1 -9 -VAC 500-mA wall -mount

transformerBZ1-piezo transducerS1 -S7 -miniature momentary -contact

pushbutton switch61 -9 -volt battery

ply. The 12 -volt supply powersthe display circuitry, op -amps,the comparators, and anLM340-5 (IC1) 5 -volt regulator.The regulator in turn powersthe 5 -volt supply line.

If AC power is interrupted, a9 -volt battery connected to J1sources current to the regulatorto keep the HyperClock func-tioning. If you plan to unplugthe clock for any length of time,the battery should be discon-nected to conserve its life.

A BIT ABOUT TIDES

Predicting the tides in any given localeis not a simple job. Tides are affected bymany cyclic astronomical forces: thedeclination in the orbits of the moon andsun relative to a point on the Earth, andthe local geography of the coast line inthe area in which you live, to name a few.HyperClock predicts the tidal levels fromthe most predominate of these forces,the moon. The moon requires 29.53days to orbit Earth, and that combinedwith the 24 -hour solar day causes a highand low tide in every 12 hour and 25.5minute interval. HyperClock tracks themoons primary affect on the tide. Youcan find out about the level of local tidesin your area from your newspaper orlibrary. The information can be used toinitially set the tide indication on yourHyperClock to a low or high point. Fromthen on the graphic display will be an aidin the determination of the relative levelof the tides in your locality.

Miscellanious: T-220 style heatsink,PC board or perforated constructionboard, battery clip, shorting blocks,solder, etc.

Note: The following items are avail-able from SkiTronix, P.O. 9685,Spokane, WA 99209: A pre-programmed HyperClock8749 microcontroller with firmwareI i cen se -$10.00.

An etched and drilled PCboard -$25.00. The foil pattern artwork suitablefor conversion to film -$3.00. Software on floppy disk -$5.00postpaid A complete kit of parts includingthe PC board, programmed 8749IC, LED's, displays, electroniccomponents, and the wall -mounttransformer -$70.00.

A detailed drawing of the HyperClockwood case, will be supplied with allorders. Please include $3.00 forshipping and handling. Wash-ington residents must include anadditional 7.9% sales tax.

The line input (pin 6) of themicrocontroller cannot be driv-en directly from the 12 -VAC walltransformer. So the trans-former signal is conditioned bya Schmitt -trigger circuit to gen-erate a suitable square wave.First the signal's amplitude isreduced by a voltage dividerconsisting of RI and R58, andits positive excursions are lim-ited to about 5 volts by Dl. Thelimited signal is then sent to theinverting input of the LM393comparator. Positive feedbackis applied to the comparator'snon -inverting input by R4 toprevent it from generating falsesignals. The comparator drivesthe microcontroller's line inputwith the resulting square wave.

ConstructionIn order to build a Hyper -

Clock, you'll need a pro-grammed 8749 microcontroller.A preprogrammed and testedmicrocontroller is availablefrom the supplier mentioned inthe parts list. The executablecode to program an 8749 isavailable from the RE-BBS(516-293-2283, 1200/2400,8N1), as a file calledHYPER.HEX. The file is sup-plied in Intel's Hex format,which is directly compatiblewith most EPROM program-

LED60 LED1

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FIG. 6-DISPLAY-SIDE PARTS -PLACEMENT diagram can be used to locate most of theHyperClock's components.

mers. The software is also avail-able on floppy disk from thesource mentioned in the partslist.

A 6.5- x 6.5 -inch octagon -shaped PC board is also avail-able from that supplier to helpyou assemble a HyperClock ofyour own. If you wish, you canmake your own double -sidedprinted -circuit board from thefoil patterns included in this ar-ticle or using artwork from thesupplier listed in the parts list.Of course, you could even use apoint-to-point wiring tech-

nique, so we'll discuss thatbriefly later on.

Figures 6 and 7 show theparts -placement diagrams forthe HyperClock (6 shows thedisplay side and 7 shows thesolder side) for those of you thatwill use a PC board. All compo-nents, except for the wall -mount transformer, are shownmounted on the circuit board.Note that the switches can beplaced on either side of theboard, depending on the cab-inet you wish to place the clockin. There are some additional

LED10

31,144i9 Q1 e11'

C12

-C10

R2' R3

C17 11112

tc2 C R9 R7

0'!"1±) LEDIO

06

(33)

-C15-

51_R5R56 R6 0

connector pads on the board soyou can run wires to the switch-es should your cabinet designrequire that they be located offthe PC board. Figure 8 shows acompleted HyperClock board.

The design readily lends itselfto many different project cases.However, make sure that thecabinet you choose has someopenings in the back to allow alittle cool air to flow around theclock's 5 -volt regulator and heatsink. If you like the case used forthe prototype, you can build oneout of a length of wood moldingas the author did. 39

The PC board was designed towork with many different dual -digit displays, so you don't nec-essarily have to restrict yourselfto the Panasonic units men-tioned in the parts list. Justmake sure that whatever youuse is a pin -for -pin same -size re-placement. If you do use the rec-ommended units, be sure toraise the two minute displaysup from the board so that theirviewing surfaces are flush withthat of the hour display.

Lastly, the PC board providessome holes for wire ties to holdthe 9 -volt battery and the wall -mount transformer leads. Youshould take advantage of them.Remember to install the 9 -voltbackup battery and connectJUI and JU2 to select 50- or 60 -Hz operation and the volume ofthe chime, respectively.

When you connect the clockto power it should come up at12:30 AM and will be ready toaccept the current time, alarmtime, date, and the tide level ifdesired. If you run into any diffi-culty, you may find some of thetroubleshooting tips providedin the following section useful.However, if all is well, you canproceed to the "operating" sec-tion to prepare the clock for use.

Point-to-point wiringWorking with perforated con-

struction board and point-to-point wiring gives you the free-dom to design your own displaylayout. One nice alternate de-sign would be to place the 60LED's in the form of a full cycleof a sine wave, especially if youset the clock to display the tidelevel.

An early prototype of the clockwas built using wire wrap. Re-gardless of the wiring tech-nique, you should invest in alarge enough piece of perforatedconstruction board (at least 6 x6 inches) so that you can makeyour custom display with plentyof room to spare for all the sup-port electronics.

Furthermore, when you areshopping for the hour and min-ute displays, select minute dis-plays that are somehow dis-tinctly different than the hourdisplay. That will make the dis-

40 play more easily readable in the

ea

TO

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BATTERY CLIPWIRES

BATTERY TIE WRAP

FIG. 7-THIS PARTS -PLACEMENT DIAGRAM should be used to position the regulator,battery, a capacitor, and the switches.

"minutes before the hour"mode.

It is also suggested that youdon't place the display compo-nents on the same side of theboard as the heatsink/regulatorassembly, C3, and the 9 -voltbattery. Doing so would in-crease the profile of the displayside of the board, forcing you toplace the LED lens at an un-desirable distance from the dis-play components.

Aside from those sugges-tions, layout is not critical, so ifyou observe good constructionand wiring techniques youshould not have any problemgetting the clock to function.However, if you should encoun-ter some difficulty, the followinghints ought to help: If no LED's are illuminatedwhen you apply power, firstcheck the unregulated supplyfor a minimum of 10 volts DC.While only 2 to 3 volts of over-head are required to operate the5 -volt regulator, at least 10 volts

is required to drive the LED'ssufficiently. If the power -supply circuitryis okay, check the wiringaround the LM393 (IC2) fromthe bridge rectifier and going toIC4 pin 6; the microcontrollerlooks at that line and if there isno line frequency at that input,the clock will shut down theLED drivers (as we explainedearlier).

Since most of the wiring inthe clock runs between the LEDdrivers and the LED's, it is likelythat you could have made an er-ror in one or more of those con-nections. If you observe that anyactive LED segments do notform numbers, then you shouldcheck the connections from IC4to IC7 and the correspondingconnections to the cathodes ofthe LED displays. A mistake be-tween IC4 to IC5 and IC6 willmake the displayed digits and/or seconds appear out of order.An error in wiring from the out-puts of the 74LS145's to the

FIG. 8-A FINISHED HYPERCLOCK. ThePC board makes assembly neat andstraightforward.

/. % '-'1-:-iiiI.Ili...H....?1...ii.;,.1.::,il...iii...ii...1....11:111,

.:.217/;(.1. !.Tlij.1..tte.1

ji Nr:ii.I.Itil...".gIIIIIIi../ f-1:1

T L1111:; _.1..T11:I.2 /--

TABLE 1-MODES AND THEIR FEATURES

FeatureMode

0 1 2 i 3 4 5 6 7

Fading Updates

Plain Updates

Before -The -Hour Display

Plain Display

Tide Light Chaser

Seconds Light Chaser

FM INCHES

THE DISPLAY -SIDE FOIL PATTERN can be used to generate oneside of the clock's PC board.

driver transistors, which con-nect to the LED anodes, willcause the same effect.

OperationThe functions performed by

S4 and S5 in the HyperClockdepend on the state of the threedisplay switches (S1 throughS3). If none of the displayswitches are depressed, press-ing S4 advances the currenthour displayed and pressing S5advances the minute display.That is how you set the time.

Pressing and holding downSi (the Display -Mode button)causes the clock to display thenumber of the current operat-ing mode, which can be alteredby pressing S4 (S5 will donothing). The various operating

\t

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THIS FOIL PATTERN can be used to generate the solder side ofthe clock's PC board.

modes and the features theysupport are listed in Table 1.

If you depress and hold switchS2 (the Display -Date button)the current month and day aredisplayed. With that switch de-pressed, the month and day canbe advanced by pressing S4 andS5, respectively.

Activating switch S3 willcause the clock to display thetime the alarm is set for. Bypressing S3 along with S4 youcan alter the hour setting, andby pressing S3 and S5 simulta-neously you can change theminute setting.

Moving on to the last twoswitches, the Alarm Toggleswitch (S7) determines thestate of the alarm and the hourchime of the clock. For example,

on power -up the hour chime isenabled and the alarm is dis-abled. If S7 is pressed once, thealarm is turned on and the hourchime is disabled. Depressingthe switch again will turn offboth the alarm and the hourlychime.

The Snooze/Tide Switch (S6)has a dual purpose. If the Hyper -Clock's alarm was armed andgoes off, that button will silencethe alarm for an additional tenminutes. You can forestall thealarm in this way as many timesas you like. If the alarm is dis-abled, and the clock is in a modethat supports the tide -level dis-play (modes 4 through 7), press-ing S6 will advance the tideindication on the 60 -LED dis-play to set its position. R -E 41

WARNING!Please note that unauthorized wire andelectronic communications interceptionand interception of oral communicationsis illegal under Federal and State Law. Inaddition Federal Law renders illegal theintentional manufacturing, assembling.possessing, or selling any electronic,mechanical, or other device, knowing orhaving reason to know that the design ofsuch device renders it primarily usefulfor the purpose of surreptitious intercep-tion or wire, oral, or electronic commu-nications. Federal law imposes both civiland criminal penalties for violations ofthe applicable statutes. Thus, the use ofthe Scanner Converter described in thisarticle is intended for and should be re-stricted to educational, scientific, and 'orinformational purposes. This is not in-tended to constitute legal advice andreaders are advised to obtain indepen-dent advice as to the propriety of theiruse thereof based upon their individualci7cumstances and jurisdictions.

SCRCONVERTER

Upgrade your scarier to receive signalsin the 800-900 or 900-1000 MHz bands!

WILLIAM SHEETS and RUDOLF F. GRAF

THE 800-1000 MHZ BAND OF FRE -quencies, lying in the portion ofthe radio spectrum known asthe UHF band, has recently be-come populated with many sig-nals of interest to the shortwavelistener (SWL) and scanner hob-byist. Originally, the 800-890

cv MHz portion was allocated tocs) UHF TV broadcasting. Lack of

interest in these frequencies(formerly TV channels 70-83)

te) and a pressing need for spec -6 trum space was largely respon-Y sible for re -allocation. The2 portion of spectrum now in -

eludes business radio, publicLP safety (police, fire, etc.) and() gen-

eral-purpose two-way radio.cc The lower portion is largely

used by cellular mobile radio42 telephone services. The upper

AX 8X.SYSIf

0

tion (above 900 MHz) is usedfor two-way radio, industrial ra-dio, amateur radio, and mis-cellaneous purposes, such aswireless video and audio links,studio to transmitter (STL)links, and various Part 15 ap-plications (low -power license -free uses), and even more! Fig-ure t summarizes the currentfrequency allocations.

The frequencies are almost inthe microwave region. Until re-cently receivers for this bandwere scarce and usually special-purpose types. In the past fewyears, a number of communica-tions receivers have been madeavailable, covering from around25 MHz or so up to over 1000MHz Some of the more expen-sive scanners cover portions of

the 800-1000 MI I/ range, whileothers block out the bands.

Now you can build a converterthat will allow the reception ofsignals from 800-1000 MHz onany scanner that covers fre-quencies in the 400-500 MHzrange. The availability of high-performance transistors andMonolithic Microwave Inte-grated Circuits (MMIC's), to-gether with very small compo-nents such as chip capacitorsand prepackaged mixer assem-blies, have made this feasible.

The antenna shown in theopening photograph is cut spe-cifically for the 800 -MHz band,It's available from the CellularSecurity Group, 4 GerringRoad, Gloucester, MA 01930.Contact them directly for infor-

9024,4HzDIGITALLOW

LIMIT COMMUNICATIONS

WEAKSIGNALWORK

BEACONSI EARTH -MOON -EARTHIL SPACE COMMUNICATIONS

900 902

IJ3FMAND REPEATERS

904

NATIONALSIMPLEX

FREDJENCY906.5MH

+ I

AMATEURTELEVISION

910

325 851 870 895

AJBLICSAFETY

:MOBILE

SAFETYMUNICIPAL,FIRE,POLICE

-MOBILERAD:OTELEPHON

-0-mMUNICIPAL,

FIFIE,POLICE

ELLREAPDHIOON-E--''-

800-1EPEATER OFFSETS JSJALLY 45MHz

CHAP EL SPACING 2.5 ER 12.5kHz

25k1 -zSPACING

I NB:NI DEBAND,

ANLREPEATERS

EXPERIMENTALAND

SPREAD SPECTRUM

AMA-ELRTELEVISION AMATEUR BAND

f (MHz) DI TAIL(902-928MHz)

9.6 92t8 928 (USA)

PART 15 DEVICESVIDEO

DATA LINKSBUSINESS

MIS;' RADIOOMMLNICATION:

I- I

90.4 302- 328MHz t1

AMATEURBAND

SHOWv ABOVE IN DETAIL

STL(BROADCAST)

LINKS

150

AIRCRAFT ANDNAVIGATION

if (MHz)

1000

FIG. --THE 800-1000 MI -Z UHF BAWD has many signals of interest to the shortwavelister-er. Here is a SUMME ry of the ct.rrant frequency allocations.

800MHz- 1GHz ANTENNA

OFFJ1 J1 L., Si

Si °N -9 5dB---

L

E0MilzCRYSTAL_

1FINE TUNECIRaPT

D?POWER RECTIFIERINPUT

+ 14 5-28VDC12- I 8VAC

G=17dENPs;1.5da

01

25137GASF ET

1ST RF

J22K3563

XTA._ OSC

AND DOUBLER

BAND PASSFILTER- 3dB

800M Hz - 1GHz

100MHzFILTER

IC2+ 12V REG

S1.S2-a,S2-b EANGE-D7OGETHER

G -4-15T3NE=5 di

03Mf133511

OUALRUPLE.R-QUI ETUF' LER

OFF

o2NS2 -b

BAND PASFILTER- 2dB

400 OR 5.30MHzFILTER

0 + 12V RFlJLATEDTO ALL STAGEE

Mi*R-7-0B

J2TO

RECEIVER400-- 500

OFT: MHzLOW PASS FUER

0 !AB ON0

)1F,2

- 2dB TP

0

DIRF

DETECTOR

NE <2dBGAIN 20 dBFRED 800-1000MHz IN

400- 600MHz OUT

NOTEG AND NF ARE TYPICALAND MAY VARY IN ANYGIVEN SYSTEM

FIG. 2-BLOCK DIAGRAM. A GaAsFET feeds a rouble -tuned fter aid a MMI: RFamplifier that feeds a second doub e-t-..ded filter. That feeds a doApla balanced mixer.or DBM. The DBM is also fed with a oral oscillator signal of a their 400 -MHz cr 5C0 -MHz_

malion an that and other aci-ous UHF antennas.

The converter described inthis article offers excellent per-formance (about 0.15 1.1.V/12dBSINAD-signal-to-noise-and-distortion-ratio-sensitivity forstandard 5 -kHz FM). having anNF noise figure) of about 2 d3,a gain of 20-25 dB, and an out-put frequency of 400-500 MHz.By simple tuning adjustment it

can be set up ITO: 800-90X, or900-1000 MHz ranges and op-timized for any 31Ci-40 MHz seg-ment in the rarig,T. It will workwell over the entire 100 -MHzrange if circuits are stagger -tuned, with only slightly re-duced sensaivity. Applicationsof the converter are as follows:1. Monitoring 800-900 or900-1000 MHz ranges.2. Amateur use for reception of

902-928 MHz band, downcon-verting to the 420-450 MHzrange.3. Reception of 902-928 MHzAmateur TV, using a standardTV receiver that covers UHFchannels 20-23. and receptionof wireless TV links operating inthe 900 -MHz range.4. in conjunction with a 500 -MHz counter. the measurementof frequencies in the 800-1000MHz range.

Referring to the block di-agram (Fig. 2), the converteruses a low -noise dual -gate 43

GaAsFET (gallium -arsenidefield-effect transistor) as an RFpreamplifier. That feeds a dou-ble -tuned filter and a second RFamplifier using a MMIC. TheMMIC feeds a second double -tuned filter. The overall RF gainis about + 27 to 30 dB and thebandwidth is around 30 MHz.That provides good rejection ofout -of -band signals and helpsminimize the feedthrough ofunwanted signals in the400-500 MHz range. The RFamplifier feeds a double bal-anced mixer, or DBM. The DBMis also fed with a local -oscillatorsignal of either 400 -MHz (for800-900 MHz conversion) or500 -MHz (for 900-1000 MHzconversion). The mixer outputis therefore kept in the 400-500MHz range covered by mostscanners. The receiver shouldbe suitable for the type of trans-mission to be received. A scan-ner is generally set to receivenarrowband frequency modula-tion (NBFM) signals commonlyused in this range in steps of12.5 kHz, 25 kHz, etc. A TV re-ceiver tuned to the lower UHFchannels (14-23) can be used toreceive TV signals in the 900 -MHz range, such as amateur TV(ATV) and the new 900 -MHzwireless video links. Converteroutput is at 50-75 ohms.

The local oscillator (LO) is a50 -MHz crystal -based overtoneoscillator. The second harmonicof the oscillator circuit (at 100MHz) is used. A fine-tuning con-trol is provided to compensatefor any 800-1000 MHz signalsnot fitting the popular 12.5 -kHzchannel spacing used by manyscanners. The LO can be shiftedat least ± 6 kHz to act as a fine-tuning control, if needed. Nor-mally, the fine tuning is left setto center position.

The 100 -MHz oscillator signalis fed to a multiplier stage usinga UHF large -signal transistor asa quadrupler ( x 4) or a quin-tupler ( x 5) stage. The appropri-ate harmonic (4th or 5th) isselected by a triple tuned filterand the signal at 400 or 500MHz is delivered to the mixer.The filter can select either signaldepending on the setting ofthree variable capacitors. A di -

44 ode detector samples the output

TABLE 1-800 TO 100 -MHz CONVERTER SPECIFICATION

Freq RangeRF InputIF Output

400-500 MHz800-900 or 900-1000 MHz

LO Freq 400 or 500 MHz, internally selectable

Noise Figure <2dB typical

Sensitivity gives 0.15 1.012dBSINAD, 5 kHz deviationwith typical scanner

Power Gain, RF to IFpi = 900 fort = 500 MHzRs = RL = 50 11

+ 22 dB typical

RF Bandwidth 40 MHz 013dB typical 0, 900 MHz

Maximum Input Level - 40 dbm (a 1dB compression

Tuning Range 800-1000 MHz

Dynamic Range Approx 90 dB (0.1 ix to 3000 liv)

Voltage and Current + 15-25 VDC 6-t 100mA, Neg ground or12-16 VAC 0 / 300 mA peak, can bemodified for + 12 VDC regulated

Freq Control of L 0 XTAL controlled .005%

Fine Tuning Range ± 7 kHz typical

PC Board (finished) size 31/2' x 5" x 1" high

RF to IF FeedthroughIsolation (IN -OUT) DB

>60 dB (a 400 MHz

Insertion Loss in dB withconverter off

- 1dB typical (44, 400 MHz- 0.3 dB typical @ 30 MHz

Switching Built-in

of the filter so that a VOM can beused to align the filter simply by"peaking" the trimmer capaci-tors for maximum output.

It is possible to just use the400 -MHz signal. However, forreception of 900-1000 MHz, areceiver capable of tuning500-600 MHz would be needed.Most scanners cover only up to512 MHz or thereabouts. There-fore, the 500 -MHz signal is nec-essary with these scanners forreception of frequencies over912 MHz.

The converter board containsa switching network for switch-ing the converter in or out. Inthe "out" position, the inputjack, J1, simply connects to theoutput jack, J2, and all frequen-cies from DC to 550 MHz arepassed. In this position, the DCline to the converter circuitry isalso opened, thus disabling theconverter.

The converter board also con-tains a rectifier and a regulator

that delivers +12 volts DC to theconverter circuitry. Either a+14.5- to + 24 -volt DC, or 12 -volt AC supply can be used.Suitable supplies are either awall transformer or one thatmounts inside the convertercase.

Referring to Fig. 3, let's goover a detailed description ofthe circuit. Signals enter J1from the antenna and arerouted to SI, a DPDT switchwith only one side used. With Siin the "off' position (converteroff), signals from Si are routedto S2 -a, another DPDT switch.(Slide switches Si and S2, al-though mounted at different lo-cations on the PC board, aremechanically linked by an actu-ator rod assembly, so that cor-rect switching is maintained.)Next, signals are routedthrough S2 -a to low-pass filterL16 -C15, and then to J2. Thelow-pass filter rejects signalsabove 600 MHz. A 50 -ohm im-

PARTS LIST

All resistors are 1/4 -watt, 5%, un-less otherwise noted.

R1-100,000 ohms, 143 -wattR2-470,000 ohms, 1/2 -wattR3-180 ohms, 1/2 -wattR4-180 ohmsR5-390 ohms, 1/2 -wattR6-1000 ohmsR7-10,000 ohms, trimmer potenti-

ometer with shaftR8-10,000 ohmsR9-15,000 ohmsR10-3900 ohmsR11-330 ohmsR12-100 ohmsR13-15,000 ohmsR14-2200 ohmsR15-10 ohms, 1/2 -wattR16-47 ohmsR17-1 megohmR18-15 ohms, 1/2 -wattR19-390 ohms, 1/8 -wattR20-10 ohmsCapacitorsCl, C8, C9, C13, C14-1-5 pF

trimmerC2 -C7, C10 -C12, C16, C28, C31-

100 pF, 50 volts, chipC15-5.6 pF NPO ± 0.25 pFC17-100 pF NPO, 5%C18-39 pF NPO, 5%C19-22 pF NPO, 5%C20-2.2 pF NPO, ± 0.25 pFC21, C29-470 pF .± 20%, discC22, C30, C32, C35, C36-0.01

p..F, 50 volts, GMV discC23-33 pF NPO ±5%C24-56 pF NPO ± 5%C25 -C27-2-10 pF trimmerC33-10 p.F/16 volts, electrolyticC34-470 RF/25 volts, electrolyticSemiconductorsIC1-MAR-1 UHF amplifierIC2-7812 +12 -volt regulatorD1-MV2107 varactor diodeD2-HP5082-2800 hot carrier

diodeD3 --1N4007 rectifier diode01-25137 dual -gate GaAsFETQ2 -2N3563 VHF NPN transistor

pedance level is maintainedthrough the converter in the"off' position to reduce VSWR(voltage standing -wave ratio)and line losses, so that a scan-ner connected to J2 has normalreception when the converter isswitched off. Switch S2 -bbreaks the 12 -volt supply line inthis position to disable the con-verter circuitry.

In the converter "on" posi-

03-MPS3866 VHF NPNtransistor

LED1-green light -emitting diode(optionali

LED2-rec light -emitting diode(optional)

InductorsL1 -L5, L1C-L12-part of PC -board

etchingL6, L15-ferrite beadL7-0.2-0.32 [LH (91/2 turns #22

enameled wire)L8-0.05-0.1 ji.H (31/2 turns #22

enameled wire)L9-0.05-0.1 µ,F1 (31/2 turns #22

enameled wire)L13-1.0 uH RF chokeL14-ferrle bead on R20L16-1/2-tJrn #22 enameled wire, 1/4

-inch diameter (see text)Other componentsJ1, J2-female BNC connectorMOD1-MCL SBL-IX mixer moduleSi, S2-DPDT PC -mount slide

switchXTAL1-50-MHz 3rd overtone

crystalMiscellaneous: PC board, small -

diameter 50 -ohm coaxial cable,project case, 14.5-24-vo t DC or12 -volt AC 350-mA transformer(see text), hardware as required,brass rod or wire, 21/4-inci rubbergrommets, line cord if required,solde., etc.

Note: The following items areavailable from North CountryRadio, PO Box 53, WykagylStation, New Rochelle, NY10804: Converter kit including allparts except case and trans-former -$67.50 + $3.50 S&H PC board only-$13.50 + $3.50 S&H Transformer-$9.50 + $3.50S&H

New York State residents mustadd appropriate sales tax.

tion, signals from JI in the800-1000 MHz range are fedthrough Si to LI (an inductorthat is incorporated in the PCboard etching and acts as ashort circuit to lower -frequencysignals) and Cl, which are reso-nant at 900 MHz.

For matching purposes, at900 MHz, CI and LI must forma resonant circuit as well as animpedance transformer to step

up the 50 -ohm impedance tosomewhere between 800 and1000 ohms. The input imped-ance of the gate of RF amplifierQ1 is about 1 to 2K or higher,and shunted by about 1 pF ca-pacitance. The output imped-ance of Q1 is between 1000 and2000 ohms with 0.5-1 pF shuntcapacitance. The voltage gain ofQI is about 7.5 from gate 1 todrain, or about 17.5 dB.

There is about 1.5 dB loss inthe output -coupling networkand about 0.5 dB loss in LI, sothat a total of about 15 dB gainis observed. The device is ratedat 1.1 dB noise figure, but allow-ing 1 dB (approximate) loss inLI and Si, an actual NF of about2 dB will be obtained. That isadequate since cable losses inthe typical antenna system willbe around 6 dB anyway.

Transistor QI is a dual -gategallium arsenide field effecttransistor (GaAsFET) biased toabout 5-10 mA drain current;R3 provides a self bias for Ql.Chip capacitors C4 and C5 areRF-bypass capacitors soldereddirectly to the solder side of thePC board for low inductance.They are the only type of capaci-tor that provides reliable by-passing at 900 MHz. ResistorsRI and R2 bias gate 2 of Ql.

The drain of Ql feeds double -tuned filter C8 -L2 and C9 -L3,and R4 feeds bias to the drain ofQ1 Typically, the tuned circuitsin this RF amplifier are tuned to900 MHz with about 2.5 pF ca-pacitance, and L1 -L5 have anequivalent inductance of 0.012microhenry, although these val-ues are typical and cannot reallybe isolated or measured. Induc-tors L2 and L3 are printed onthe PC board and are propor-tioned to give the desired coup-ling and inductance. Theirlayout is critical and cannot bechanged.

The signal from L3 is coupledthrough chip -capacitor C10 toIC1, a monolithic microwave IC(MMIC) amplifier with 50 -ohminput and output. Resistor R5provides about 17 mA operatingbias for IC1, which gives about13 to 15 dB gain at 900 MHz.The output of IC1 is coupled viaC12 to filter L4 -C13 and L5 -C14.The five tuned circuits in this 45

J1 500 !OFFINPUT TAX ,

ON

&toC6

100pFR2

470K ?:

t --C2

100pF

G2

GI

C3

R1 100pF

100K

L1'

022N3563

OSC

R103.9K

R11

3300

C7 R4100pF 1800

cl,

T100pF

S2 -aOFF

ON i L16

1 3

IC1

4 MAR -1C10

L3 100pF

C81- 5pF

800- 1000MHz

C5100pF

0125137

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FIRST RFSECTION

L750MHz

0.2-0.32µH 100MHzC20 C23

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R53900

C12

100pF

C9 SECOND RF1 - 5pF SECTION

01C C131- 5pF

800- 1000MHz

R3C4 1800

100pFQ3

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100pF

C1839pF

C1922pF

XTAL1 R9 C2115K 470pFT

L13 R8 _L1000

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MV2107

C2456pF

0.05- 0.10

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0 05- 0.10

R12 R1315K

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R1510f2

L11*

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400- 500MHz

C28100pF

R6 R71K 10K DELTA TUNE

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TO LED1(OPTIONAL)

FIG. 3-CONVERTER SCHEMATIC. A 50 -ohm impedance level is maintained throughthe converter with S1 in the "off" position so that a scanner connected to J2 still hasnormal reception. Switch S2 -b breaks the 12 -volt supply line in this position to disablethe converter circuitry.

converter yield an overall RFbandwidth of 40 MHz at the 3dB points. The signal from L5,about 28 to 30 dB stronger thanthe signal at J1, is applied to amixer module (MOD1), an MCL

cy)ci SBL-IX, where it is mixed with

the LO signal at 400-500 MHz.The IF output is then fed to S2 -

P. a, where it is connected to J2 via,2). low-pass filter L16 -C15.6 An LO signal of either 400 or'E 500 MHz is required by mixer.52 MOD I. It is generated as fol-LUio lows: Q2, a 2N3563, is config-o ured as an overtone crystal

oscillator. Emitter stabilizationCC is provided by R11, and R9 -R10

provide base bias. Resistor R12" supplies the collector voltage for

Q2 through L7 and L8. Compo-nents L7 and C18 are nominallytuned to 50 MHz, the frequencyof XTAL1. Components C19 andL8 form a resonant circuit at100 MHz and therefore have alow impedance to 50 -MHz sig-nals. Bypass capacitor C21 RFgrounds the bottom (cold end)of L8.

There exists a feedback ca-pacitance (about 3 pF) betweenthe collector and emitter of Q2.That, in conjunction with C17,forms an oscillator; the oscilla-tion of Q2 would tend to takeplace at the resonant frequencyof C18 (plus strays) and L7 (L7 isvariable by means of a ferriteslug). The base of Q2 must be

RF grounded, which can onlyoccur at the series -resonant fre-quency of XTAL1, L13, andvaractor-diode DI; D1 acts as acapacitor whose value can bevaried via the applied DC volt-age from potentiometer R7. Re-sistor R6 limits the lowestvoltage to about 1 volt, and R8provides RF isolation for DI.Varying R7 has the effect ofvarying the effective frequencyof the crystal plus and minus1000 Hz. When L7 is nominallytuned to 50 MHz, the crystal os-cillator circuit produces a signalof 50.000 MHz. However, weneed 100 MHz.

Since Q2 operates as class -Cand produces harmonics, filterL8 -C19 is tuned to 100 MHz.That transfers 2nd harmonicenergy (6-10 dB below the fun-damental 50 MHz) via couplingcapacitor C20 to a second 100-

MHz tuned circuit (C23, C24,and L9). Capacitors C23 andC24 are chosen so as to matchthe oscillator to the base of fre-quency multiplier Q3, anMPS3866. That generates har-monics of 100 MHz in the basecircuit of Q3. Capacitor C24 ischosen to have a low impedanceat higher frequencies to encour-age the flow of harmonic cur-rents in the base circuit of Q3.

Inductors L10, L11, and L12form a filter tuned to either 400or 500 MHz by adjustment ofC25, C26, and C27. There issufficient tuning range to covereither 400 or 500 MHz. The fil-ter is triple -tuned and L10, L11,L12, and their coupling coeffi-cients are determined by the PCboard layout which they arepart of. RF energy at 400 (or500) MHz is taken from a tap onL12 and fed to mixer MOD1.

Without the right test equip-ment, it would be difficult to al-ign C25, C26 and C27. However,the problem is solved by diodedetector D2, C31, and R17. Re-sistor R17 slightly forwardbiases D2 to produce about+ 0.2V at test point TP2.

When RF drive is applied fromL12, a negative voltage is pro-duced at TP2. When the triple -tuned filter is correctly -tunedand Q3 is operating properly,about - 0.3 volts is produced byD2, since about 300 millivolts ofRF is present from L12. This,when added to the + 0.2V biason D2, produces -0.1V at TP2.Diode D2 is forward -biased toimprove its sensitivity at low RFlevels. 'liming of C25, C26, andC27 simply consists of monitor-ing the DC voltage at TP2, andobtaining the most negativevoltage possible by peakingC25, C26, and C27.

Regulator IC2, a 7812, pro-vides 12 -volts DC power to thecircuit; C32 and C33 and C34,C35 help stabilize IC2. RectifierD3 acts as a protection device incase a negative DC voltage is ap-plied to the circuit, and C36 re-duces 60 -Hz buzz caused byswitching transients in D3. Atleast 14 -volts DC is requiredacross C34 for IC2 to function.

When we continue next time,we'll build the converter andshow you how to align it. R -E

NEXT MONTH IN Popular Electronics

Exciting Features, Projects, Reports, & Columns THE CLASSIC

INDUCTION COILMake a spark ring and more whenyou experiment with this powerfulhigh -voltage generator

BUILD THEPRINTER SENTRYUse it to keep tabs on all of yourprinter's functions

BUILD ASPEAKER PROTECTORIt saves your expensive loudspeak-ers from amplifier shorts, excessivedrive, and turn -on thumps

ELECTRONIC TRACKINGFOILS CAR THIEVESGet the facts on the new high-techcrime -stopping systems

And there is more!PRODUCT REVIEWS-Bang &Olufsen Compact Music System,Memorex Subwoofer/SatelliteSpeaker System, and many more

DX LISTENING-The changingface of Russian shortwave

COMPUTER BITS-Low priced,high speed modems

THINK TANK-A potpourri of auto-motive circuits

HAM RADIO-Design and buildbaded-dipole antennasSCANNER SCENE-Monitoringmovie -set communications

CIRCUIT CIRCUS-Some un-usual uses for common regulator IC's

PICK UP Popular Electronics AT YOUR FAVORITENEWSSTAND, CONVENIENCE STORE, OR SUPERMARKET.,

47

LEN FELDMAN

Will new standards bringof AM radio?

IT MAY COME AS SOMETHING OF A SURPRISE TO THOSE OFus who pay little attention to AM radio that thisoldest of all broadcast services is due for some up-grading. After all, the FM radio service has been thepreferred form of radio broadcasting in this coun-try for at least two decades, now, and even FM radiomay some day be obsoleted by digital audio broad-casting, or DAB. In fact, more than a dozen pro-posals for DAB are currently either on the drawingboards or have been demonstrated in prototypes.So why bother with AM radio at this late date?

The AM stereo debacleBack in the mid -1980's, the Federal Communica-

tions Commission considered several systems forAM stereo broadcasting. Many AM broadcasters feltthen that the reason for the decline of AM radioaudience was the fact that FM could offer stereowhereas AM could not. Initially, the FCC selectedone of some six systems, the Magnavox proposal, asa "standard." Faced with all sorts of threats of litiga-tion by other proponents, the FCC reversed itselfshortly thereafter and in effect, said, "let the mar-ketplace decide." Since then, the field of propo-nents has narrowed down to two-the Motorola C-Quam system (by far the most popular) and theKahn -Hazeltine system. Many experts maintainthat by not coming down in favor of a specific sys-tem, the FCC has discouraged both manufacturersof receivers and AM radio broadcasters from mov-ing to stereo.

With AM broadcasting audience on the declinefor many years, manufacturers of high quality AM/FM tuners and receivers have paid little attention tothe AM circuitry that they incorporate in their prod-

ucts. Figure 1 shows the actual frequency re-sponse measured for the AM section of ahighly reputed AM/FM stereo receiver. No won-der listeners accustomed to playing digitalcompact discs and FM radios are "turned off'by this kind of AM reception! This "after-thought" approach by receiver manufacturersfurther exacerbated the problem. Anotherproblem of AM has been adjacent channel in-terference-a problem that is particularly in-tense during evening listening. Many profes-sionals blame the FCC for that problem aswell, maintaining that the granting of broad-cast licenses by the FCC has been a poorlyadministered "pork barrel" affair with little

back the good ol' days soa waorsaincanatraccit.........i ai4rite-L--".----- ....`::la 1.141: . ,,

:: ZSign 14 1.1111%. OWLS 01110.11.}121,6 e40. 4: ...::'''''''' =.2.7=!.......r= :'" ' 4,

:I: :: :LI: MII51=raZ= LI 34r.141...::.,31,,,waft ragx..111.1111PIEN.041....,........'' =====n,-- .11,71.-----, ,,.411k A ,

A COMEBACKattention paid to the technical problems that haveinevitably resulted from an overcrowding of thebroadcast band.

NRSC to the rescue!As the AM broadcasters situation became worse

and worse, the National Association of Broad-casters (NAB) and the Electronic Industries Associ-ation (EIA) finally decided to address some of theproblems in what amounted to a major cooperativeeffort between organizations that, up until thattime, had pretty well ignored each other. The twoorganizations formed a separate committee knownas the National Radio Systems Committee, orNRSC. In a series of meetings, the NRSC came upwith two standards recommendations, known asNRSC-1 and NRSC-2. A proposal to make NRSC-1 anational voluntary standard was issued in January1990, and in March 1991, the EIA published thecontents of NRSC-1 as an interim standard (EIA/IS -80) entitled 'Audio Bandwidth and DistortionRecommendations for AM Broadcast Receivers."On a parallel track, the FCC issued a report andorder on April 27, 1989 in which compliance withNRSC-1 was made mandatory as of June 30, 1990,while measurement of compliance with NRSC-2was postponed until June 30, 1994. Both NRSC-1and NRSC-2 were designed to address the problemsof audio fidelity and interference mentionec above.

NRSC-1 and EIA/IS80Let's take a look at the EIA Standard developed for

receiver manufacturers first. Radio receivers thatsatisfy the technical requirements of this specifica-tion must have a frequency response of not lessthan 50 Hz to 7500 Hz, with limits of +1.5 dB and- 3.0 dB, referred to 0 dB at 400 Hz. Since "openingup" the bandwidth to this extent might well in-crease interference from adjacent cha L. els-es-pe c ially in crowded metro-politan areas and during night-time listening-receiver man-ufacturers may choose to offer aswitch on their products thatwould, at the user's option, re-duce bandwidth. As long as atleast one of those switch posi-tions results in the frequencyresponse just stated, the re-ceiver will be considered to com- 49

ply with the new standard.The second part of the NRSC

standard deals with harmonicdistortion. It states that re-ceivers designed to satisfy thestandard shall not exhibit morethan two percent (2.0%) totalharmonic distortion plus noise(THD + N) at all measured fre-quencies between 50 Hz and7500 Hz. 'IWo percent distortionmay sound like a high numberto those of us accustomed to thedistortion levels of modern au-dio amplifiers and FM tuners,but, in fact, many current non-conforming AM tuners exhibitfar higher distortion levels thanthat!-particularly at higher au-dio frequencies.

A third recommendation ofthe standard involves the incor-poration of circuitry into AM re-ceivers that attenuates 10.0 -kHz adjacent -channel carrierfrequencies by 30 dB, or 20 dBwhen the measurements aremade with preemphasis charac-teristics inserted at the AM in-put of the RF test signalgenerator. To clarify that lastpoint, we should note that inrecent times, recognizing thatAM radios had very poor high-

frequency response, broad-casters began boosting the au-dio treble response of theirtransmission chains in an at-tempt to overcome the high fre-quency attenuation present innearly all AM radios and tuners.Unfortunately, no two stationsused the same boost of pre -

emphasis characteristic. Fur-thermore, an overly extreme useof high -frequency preemphasismade the problems of inter-ference between adjacent chan-nels even worse. So, included inthe NRSC-1 recommendation isa fixed preemphasis charac-teristic that AM radio broad-casters are required to use. Thepreemphasis characteristic,not unlike the one used by FMbroadcasters in the U.S., isshown in Fig. 2.

Assuming that broadcastersconform (and as of this writing,well over half the AM broad-casters in the United Stateshave embraced NRSC-1 stan-dards), manufacturers of AM ra-dios are expected to voluntarily

50 incorporate standard, fixed

TYPICAL

10.000

8.0000

6.0000

4.0000

2.0000

0.0

-2.000

-4.000

-6.000

-B.000

-10.00

20

FREQUENCY RESPONSE OF AM TUNER SECTION OF 'HIGH FIDELITY" RECEIVER

/lp

100 1k 10k 20k

FIG. 1-AMPLITUDE VERSUS FREQUENCY. This is the response of the AM tunersection of a "hi-fi" AM FM stereo receiver!

20.000

15.000

10.000

5.0000

0.0

-5.000

-10.00

-15.00

-20 00

PREEMPHASIS CHARACTERISTIC USED 3Y AM STATIONS, ACCORDING TO NRSC-1

Ap

20 100 1k 10k

FIG. 2-BY STANDARDIZING THE PREEMFHASIS CHARACTERISTIC used by AMbroadcasters, AM receiver manufacturers are able to incorporate standard deem-phasis networks in their products to achieve the desired flat response to 7.5 kHz orbetter.

deemphasis networks. In mea-suring the frequency responseof an AM radio conforming tothe new standards, a laboratorywould expect to obtain a fre-quency response such as thatshown by the dashed line in Fig.3. The solid lines represent theallowable deviation or toleranceover the range from 50 Hz to 7.5

kHz. Results shown in Fig. 3presuppose that the appropri-ate preemphasis network is in-stalled between the audio gener-ator and the amplitude modula-tion input terminals of the RFsignal generator. If such a pre -emphasis network is not usedin the test, results should be asshown in Fig. 4.

5.0000

0.0

-5.000

-10.00

-15.00

-20.00

-25.00

RESPONSE OF DEMODULATED OUTPUT FOR SETS CONFORMING TO NRSC-1 STANDARD

Ap

20 100 1k 10k 20k

FIG. 3-FREQUENCY RESPONSE of AM circuitry that is required to conform to theNRSC-1 standard. The dashed line represents an ideal response, with the solid linesrepresenting the tolerance limits. (Presumes preemphasis in the RF test generator.)

RESPONSE OF DEMODULATED OUTPUT FOR SETS WHEN NO MODULATION PREEMPHASIS IS USED

5.0000

0.0

-5.000

-10.00

-15.00

-20.00

-25.00

Ap

=,11.

20 100 1k 10k 20k

FIG. 4-FREQUENCY RESPONSE of AM circuitry that is required to conform toNRSC-1, with no preemphasis in the RF test generator.

FIG. 5-AMAX LOGOS will identify AM radios that meet the NRSC requirements.

NRSC-2 by 1994During the interim period

from June 1990 to June 1994.the FCC is going to presumethat if a station conforms toNRSC-1. it is also in compliancewith NRSC-2. The chief reasonfor the delay is the lack of appro-priate, inexpensive test equip-ment needed to confirm com-pliance with all the provisions ofNRSC-2. Those provisions man-date that. NRSC-2 deals pri-marily with attenuation ofcarrier emissions rather thanindirectly with audio responseand performance. According tothe NRSC-2 rules, emissionsbetween 10.2 kHz and 20 kHzremoved from the carrier's fun-damental RF frequency must beattenuated at least 25 dB belowthe unmodulated carrier level.Emissions between 20 kHz and30 kHz away from the carrierfrequency must be attenuatedby at least 35 dB below the un-modulated carrier level. Emis-sions that are between 30 kHzand 60 kHz away from the car-rier frequency must be attenu-ated by at least 5 + ldB/kHzbelow the unmdodulated car-rier level. (For example. emis-sions that are 50 kHz away fromtile carrier frequency wouldhave to be attenuated by 5 + 50.or 55 dB relative to the level ofthe unmodulated carrier). Fi-nally, emissions between 60kHz and 75 kHz must be attenu-ated by at least 65 dB.

More breathing roomWhile the NRSC-1 and

NRSC-2 provisions will cer-tainly help alleviate some of theproblems of interference be-tween stations, it cannot do thewhole job in view of the con-gestion of the AM band that nowexists in some geographicalareas. Accordingly, as of July 1.1991, the FCC officially ex-panded the AM band by an additional 100 kHz. The band nowextends from 535 kHz to 1705kHz.

This additional spectrumspace is expected to accommo-date at least 200 AM stations,nationally. Rather than increasethe number of licenses to broad-casters, however, it is expectedthat those stations causing the 51

52

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most severe interference will beasked to move up into the newfrequencies. In order to retaintheir audiences, however, it islikely that those stations whosefrequencies are reallocated tothis new portion of the band willbe allowed to "simulcast" ontheir existing frequencies forsome time until a sufficientnumber of new AM radios arepurchased by the listening pub-lic. Manufacturers (and par-ticularly makers of car audiosystems) have already incorpo-rated the new swath of frequen-cies in their products and itturns out that the cost of doingso is minimal.

A new symbol of excellenceAs these attempts to improve

AM transmission and receptionwere being formulated, the NABand the EIA came up with theidea that it would be nice tohave some visible means ofidentification displayed on radi-os that meet the requirementsof the new standards. Afternearly two years of agonizingover the design of a symbol, theorganizations have come upwith a decal to be called the'AMAX" symbol, which standsfor 'AM Radio at its maximumpotential." The certificationlogo could be affixed to radiosthat meet basic eligibility crite-ria including the equalizationstandards, variable bandwidthand other requirements de-scribed earlier. ltvo types oflogos will be available. The sec-ond one, reading "AMAX Ster-eo," will be applied to improvedAM radios that also have stereocapability. Illustrations of bothlogos appear in Fig. 5.

The "AMAX" program doesnot mandate a particular stereoAM format-only that the radiobe capable of receiving and de-coding some kind of AM stereotransmission. Of course, thedecision to market AMAX cer-tified radios is at the discretionof individual manufacturers, asis the decision to apply the'AMAX" or 'AMAX Stereo" logoto the sets themselves. Inter-estingly, we recently learnedthat the latest Delco/Bose caraudio radios, as installed insome 1992 model General

Motors automobiles, do in factmeet the AMAX criteria but forreasons of aesthetics, the carmaker elected not to apply thelogo to the radios, at least forthe present.

The NAB plans to publicizethe logo through its memberstations, who will be encour-aged to develop promotional tie-ins with local audio retailers.NAB is also expected to unveil amajor campaign by the time youread this, promoting enhancedAM radio to consumers. In addi-tion to the improvements thatwe have already mentioned, eli-gibility of a radio to bear theAMAX symbol must also includeprovision for an external anten-na, noise blanking for pulse -type interference and the ex-panded AM band.

Will improvements help?While both the EIA and the

NAB are enthusiastic aboutthese attempts to improve AM,the question that remains iswhether or not AM can attractenough of an audience to re-main a major broadcasting for-mat in the years ahead. Eventhough it is still uncertainwhether or not the improve-ments in AM broadcasting andreception will attract new lis-teners to the band, the manyimprovements are certain to bewelcomed with open arms bythose who have been listeningto AM for quite some time. Whilemany AM broadcasters speak ofa "level playing field" (againstFM), the fact is that even withresponse extending to 7.5 kHz,sound quality cannot comparewith the quality of FM, to whichso many listeners have becomeaccustomed.

Still, when you hear an AMbroadcast that has extendedfrequency response of this kind,it's amazing how good it doessound when compared with the"typical" AM radio sound wehave endured for many years.Perhaps AM radio can be given anew lease on life-even if it'sonly a temporary reprieve untildigital audio broadasting(which some now prefer to calldigital audio radio, or DAR) re-places both of our currentmodes of radio. R -E

MICHAEL A. LASHANSKI

LAST MONTH WE INTRODUCES) YOUto our professional-qua.ry 2.5 -MHz. function generator a:3d fre-quency counter that can readup to 150 MHz. This mcnth we'llshow you haw to build, tes-., andproperly use this essental testinstrument.

ConstructionThe function generator cir-

cuitry is mounted on thre hoards; the nicthe-- boardaughter board, and LED diplay board. The PC bear isavailable from the sourcetioned in the parts list.terns are provided here if,wish to make your ownhcwever the artwork a.signed for nonplated haiplaces where it is impossisolder both sides of a enent, such as in the swit.rays, vias are providedconnections from. one side othe board to the other Ifyoudcmake your own board you 1_have to solder some -./vbes fromthe top of the switch arrays topoints on the board. That is notnecessary if you use the hoardssupplied with the kit

Figures 6 and 7 shrew internalphotographs of the author'sprototype. Solder all diodes andristors first, folowedi by thecapacitors and then the IC's. ICsockets are not requ red, ot..tthey may make life a lot easier ir.the event of trouble.

It's best to build and test func-tional blocks as yon o ratherthan building the whcle unit allat once. First, start by con-structing all the cab_t assem-blies as indicted in Fig 8. Startwith the power -supply section,and verify that the output %Ail: -ages are correct. The AC powercord routes through a strain re-lief in the back pane and oreside is soldered to tie top ofswitch S15 (pole a). The otherAC lead is soldered to the podconnected to fuse FL.

Next, build the triangle andsquare -wave generator sec-tions. Those secticns consist ofcomponents with the 1XX and2XX component namaberingscheme. A parts plazernent di-agram of those secticns, located

EIV41111i1LIITA0111GENE TORLet's build our benchtop

function generatorand frequency counter!

on the main board, is shown inFig. 9. You will need an os-cilloscope to verify that a tri-angle wave of about two voltspeak -to -peak is present at thegate of Q5, and a one-vcit peak -to -peak square wave is presentat the collector of W. If thosetwo waveforms are not present,go back and check your solderjoints and component orienta-tions.

Potentiometers R125 andR126 set the symmetry of thewaveform and should be ad-justed to give a triangle wavewith equal slopes. R12.c. sets theupper frequency limit and

should be adjusted to give yourdesired high frequency for agiven range. That is done withthe course frequency -adjust po-tentiometer S101 in its max-imum position. As a generalguide set 8129 for a maximumfrequency of 2.5 MHz, with the1 -MHz range switch engaged.Pater tiometer R223 sets thezero balance of the triangle waveand is adjasted to give a cen-tered signal. Square -wave bal-ance _s achieved through poten-tiometers R224 and R225. Youcan now check the pulse outputfor TTL levels and a variableCMOS level. With the basic gen- 53

O

0 _ -

Ely00

ti

O

.m. .0 0..m. ... .. mm .0

_ _\: . ...:,=.. ..: 00 00

4Ye INCHES

O 0

0 0

COMPONENT SIDE DAUGHTER BOARDfoil pattern.

0

4IA INCHES

SOLDER SIDE DAUGHTER BOARDfoil pattern.

erator now functioning, buildthe sine -shaper circuit (compo-nent numbers 3XX) and verify asine wave at the output of IC9.

Adjust R323 for a two -voltpeak -to -peak sine -wave outputat IC9 pin 12. The amplitude ofthe square wave is controlled byR324, which should be set togive a clean square wave with-out any overshoot or roundingon the edges.

The output amplifier shouldbe built next. That section usesthe 4XX numbering scheme.

54 Set to R423 to its center posi-

COPPER TAB CONTACTS

CONDUCTIVE SH,ELDON BOTTOM CASE

FUNCTION FREQUENCYSWITCHES RANGE SWITCHES

DAUGHTER BOARD

FIG. 6-INSIDE VIEW OF the author's prototype. A transparent red acrylic sheet wasused for the front panel. A copper tab is soldered to the ground plane of the daughterboard and contacts a 91/2 by 31/2 -inch conductive shield, which is glued to the inside ofthe bottom case (not shown).

USE SHIELDEDLEADS FOR J1- J4

R325/ R424/R127/

S301 S401S101

F1

R128/ R830/

S201 S802R226/ s102 R831/ S801

FIG. 7-INTERNAL PHOTO OF the author's prototype. Start construction by con-necting all cable assemblies to switch -potentiometers mounted on the front panel.

tion and adjust it only if there isno output. Next, put your os-cilloscope on DC coupling andobserve the DC level of the out-put, adjust R422 until the out-put waveform is centeredaround zero. Verify the open -cir-cuit signal swing of 20 voltspeak -to -peak and the - 20 -dBattenuator switch.

The last work on the motherboard is to build the frequency -counting section and to mountthe display board. The six dis-play LED's are soldered to thedisplay board, which is con-

nected to the motherboard by a90 -degree, 14 -pin strip header.With the display and compo-nents in place, observe the dis-play. Select the MHz range andmake sure that all the digits arefunctioning. If not, go back anddouble check the circuit. Use afrequency counter or scope tocalibrate the counter by adjust-ing C504 so that the displayreading is the correct frequencyselected.

The daughter board, whichholds the counter input ampli-fier and sweep generator is as -

J5

no- -o- --1S101

0I FREQUENCY

o 0 oI ADJUST

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R128

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CABLE ASSEMBLIES

SWEEP TIMEr 1

R8305801

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oS201 R226-

LEVEL

J1

3

4

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3 3

4 4

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J3EXTERNAL

FREQUENCY COUNTERINPUT

F G. 8-CABLE ASSEMBLIES show the potentiometers that are connected to each ofthe function switches.

sembled next. That parts -placement diagram is shown inFig. 10. The frequency -counterinput circuit must be testedwith an external signal or by se-lecting the external -signalsource function and jumpingthe generator output to thecounter input. Testing consistsof verifying the operation of theswitches, S11-S14 and the in-put amplifier.

The input amplifier can betested by varying the amplitude

of an input signal from about 25millivolts to 50 volts peak -to -peak (if no test signal is avail-able, use the generator itself)and observing the frequencyreading on the display. The fre-quency should remain the samefor all amplitude conditions.When selecting the prescalefunction, the display shouldshift two decimal places to theright if working correctly.

All the boards were designedto use transistors with an emit-

ter -collector -base pin arrange-ment, and the rectangular padsare configured to accept that. Ifyou choose to use the alternatetransistors indicated in theparts list, they are Americanmade, and use an emitter -base -collector pin arrangement.When the substitutes are used,a small circular pad is placedbetween the emitter and collec-tor of the rectangular pads. Thiscircular pad is used for the basepin and the collectors and emit-ters remain connected to therectangular pads. 59

All resistors are 1/4 -watt 5% un-less otherwise indicated.

R101-2700 ohms, 1%R102, R104, R105, R109, 8111-

100,000 ohms, 1%R106-33,200 ohms, 1%R107, 8108, 8110-1000 ohms, 1%R112, R114-3010 ohms, 1%R113-49,900 ohms, 1%R115, 8120-4990 ohms, 1%R116, 8121-7150 ohms, 1%R117, R122-348 ohms, 1%R118, R123-75,000 ohms, 1%R119, R124-750,000 ohms, 1%R125, R126, R826, 8827-10,000

ohms, potentiometerR127, 8128-5000 ohms, potenti-

ometer (part of S101 and S102,respectively)

R129, 8825-20,000 ohms,potentiometer

R201, 8210, 8220-10,000 ohmsR202, R222-470 ohmsR203-390 ohmsR204, R206, 8219-1000 ohmsR205, R216, R217-2700 ohms,

10/0

R207, R208-4020 ohms, 1%8209-511 ohmsR211-30,000 ohmsR212-2000 ohmsR213, R214-13,000 ohmsR215-910 ohms, 1%R218-7500 ohmsR221-47 ohmsR223, R828-5000 ohms,

potentiometerR224, R225, R228, R229-2000

ohms, potentiometer8226-10,000 ohms, potentiome-

ter (part of S201)R227-4700 ohms, potentiometerR301-49,900 ohms, 1%R302, R303-11,300 ohms, 1%8304, R306-12,100 ohms, 1%R305-309 ohms, 1%R307-200 ohms, 1%R308, R309-24,900 ohms, 1%R310-127 ohms, 1%R311-63.4 ohms, 1%R312, R313, 8320-1000 ohmsR314-5100 ohmsR315-680 ohms8316-150 ohmsR317-6800 ohmsR318, R319-10,500 ohms, 1%R321-2000 ohms8322-12 ohmsR323, R324-1000 ohms,

potentiometerR325-5000 ohms, potentiometer

(part of S301)R401, R402, R503, R504-10,000

ohmsR403, R404-22,000 ohms

R405-170 ohms, 1%R406-12,000 ohmsR407-1200 ohms8408-2000R409-18,200 ohms 1%R410-270 ohms, 1%8411-100 ohms, 1%R412, R414, 8502-3000 ohmsR413-24,3000 ohms, 1%R415, R418-47 ohms, 1WR416, R417-7.5 ohmsR419-50 ohms, 1/2W8420-499 ohms, 1/2WR421-56.2 ohms, 1%R422, R424-10,000 ohms, poten-

tiometer (R424 is part of S401)R423-200 ohms, potentiometer8501-100,0008505-10 megohmsR701-10,000 ohmsR702-100,000 ohms8703-1 megohmR704-50 ohmsR705, 8718-150 ohmsR706, R712-220 ohmsR707-470 ohmsR708, R715-51 ohms8709-8711, 8713, R714, R716,

8717-510 ohmsR719-36 ohms8720-1000 ohms8801-7500 ohms, 1%8802-33,000 ohms, 1%R803-33 ohms, 1%R804, R805, R807-5100 ohms,

1%R806, R810, R816, R817, R819,

R820, 8822-10,000 ohms, 1%8808-510,000 ohms, 1%R809 2200 ohms, 1%8811-22,000 ohms, 1%R812-2400 ohms, 1%8813-100 ohms, 1%R815-150,000 ohms, 1%R818-15,500 ohms, 1%R821-2000 ohms, 1%8823-15,000 ohms, 1%R824-18,000 ohms, 1%R830, 8831-5000 ohms, potenti-

ometer (part of S801 and S802,respectively)

CapacitorsC101, C102, C204, C205-0.1 1..LF

ceramicC103, C203-100 pF, ceramicC104-0.001 ILF, MylarC105-0.01 ILF, MylarC106-0.1 µ,F, MylarC107-1 1.11, MylarC108, C504-15-60 pF, variable

capacitorC201-68 pF, ceramicC202-0.047 ceramicC301, C303 0.1 11F, ceramicC302, C304, C502-39 pF, ceramic

PARTS LIST

C305, C401-4.7 pF, ceramic0307-15 pF, ceramicC308, C408-5-35 pF, variable

capacitorC402-120 pF, ceramicC403-2.2 pF, ceramicC404, C406 6.8 µF, tantalum,

20 voltsC405, C407-0.047 p.F, ceramicC501-33 pF, ceramic0503-10 pF, ceramicC601, C602-1000 1.LF, electrolytic,

50 voltsC603, 0604-100 µF, electrolytic,

50 volts0605-1 1.LF, tantalum, 20 volts0701, C704 -C706--0.1

ceramicC702, 0707-100 pF, ceramicC703 10u tantalum 16 volts 0801-

22 µ,F, tantalum, 16 voltsC802, C803-220 pF, ceramicC804, C805-100 pF, ceramicC806-500 pF, ceramicSemiconductorsD101 -D108, D201 -D204,

D206 -D226, D301 -D312,D315 -D318, D401, D402, 0701,D702, D801 -1N4148 diode

D205 -1N751, 5.1 -volt Zener diodeD313, D314 -1N746, 3.3 -volt Zener

diodeBR1-WO2M bridge diode01, 04, Q12, Q13, Q21 -2S01815

or MPSA05 NPN transistorQ2, 03, Q6, Q7, Q11, Q19, Q20-

2SA1015 or 2N4403 PNPtransistor

Q5, Q17 -2N4416, N -channel FET08-2N3904, NPN transistor09, 010, Q14-2SC1923 or

MPSH34, NPN transistorQ15 -2N2219, NPN transistorQ16 -2N2905, PNP transistor018-PN5139, PNP transistor101, IC2-LM741, op -ampIC3, 1C4--LM308, op -ampIC5, IC6, IC20-CA3086, NPN

transistor IC (Harris)107-7420, dual 4 -input AND gateIC8-4011, quad NAND gateIC9-CA3030, op -ampIC10-4066, CMOS quad bilateral

switchIC11-7216B, frequency counter

and LED driver (Intersil)1012-7815, + 15 -volt voltage

regulatorIC13-7805, + 5 -volt voltage

regulator1014-7915, -15-volt voltage

regulator1015-MC10116, ECL triple -line re-

ceiver with Schmitt trigger(Motorola)

60

IC16-SP8629, prescaler (Plessy)IC17-LM324, quad op -ampIC18--MC1458, dual op -ampIC19-CA3140, op -amp (Harris)SR801-1000 ohms, thermistorDISP1-DISP6--common-cathode

LED (FND357)Other componentsS1-S7-4PDT-D switchS8-DPDT switchS9-S11-DPDT-D switchS12-S14-DPDT-I switchS15-DPDT on/off switchS101-DTDP switch used with

R127 (5K potentiometer)S102-DTDP switch used with

R128 (5K potentiometer)S201-SPDT switch used with

R226 (10K potentiometer)S301-DPDT switch used with

R325 (5K potentiometer)S401-SPDT switch used with



R831 (5K potentiometer)J1-J4-BNC connectorJ5, J14 -8 -position female/male,

0.1 -inch centersJ6 -5 -position female/male, 0.1 -

inch centersJ7, J12 -2 -position female/maleJ8, J13 -6 -position female/maleJ9-J11, J15, J16 -4 -position

female/male, 0.1 -inch centersXTAL1-10-MHz AT/CUT crystalT1-115/40 volts AC, 0.5 -amp

transformerF1 -0.5 -amp fuseMiscellaneous:Case (CTP-1 by

Global Specialties), three 1.75 -inch standoffs, four 2 -inch stand-offs, two TO -5 heatsinks, threeTO -220 heatsinks, three PCboards, internal wiring,fuseholder, 3 -conductor 18 -gauge power -supply cord, andstrain relief.

Note: The following items areavailable from Tristat Elec-tronics, Inc., 66A BrockingtonCres., Nepean, Ontario, Cana-da, K2G 5L1, (613) 228-7223: A set of three etched anddrilled PC boards-$76. All components without thePC board and case-$250. Complete kit of all parts (un-finished front panel)-$300. Cut and silk-screened frontpanel-$10.

Add $17 for shipping and han-dling. Send check or moneyorder only.

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The sweep generator is built.next. If you're using the boardssupplied with the kit, mountpotentiometers R825-R828 tothe solder side of the board.That will make adjustmentseasier when the unit is as-sembled. If you're making your

own boards, place the potenti-ometers on the component sideand make your adjustments be-fore the board is connected tothe mother board.

Once again you'll need an os-cilloscope to verify proper align-ment. Set R828 to its midpoint, 61

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FIG. 9-THE DUAL -PRIMARY TRANSFORMER can accommodate 115-volt operationby connecting the two primaries in series: 1 to 3 and 2 to 4. For 220-volt operation,connect pins 2 and 3 in series. Also, the transistors have an extra base pad fordifferent packages.

and adjust R825 to give a goodlog output (when selected) and alinear output. Adjust R826 toachieve a good input signal to

J14

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113

R827

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FIG. 10-PARTS PLACEMENT OF DAUGHTER BOARD holds the input amplifier and62 sweep generator circuit.

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center position and adjust-ments can be made by observ-ing the LED display with thecounter set to the internal-count mode.

If everything is working prop-erly, you can install the com-pleted boards into the case. Thetop of the case uses four 2 -inchstandoffs. The front and backpanels supplied with the caseare of 0.065 -inch aluminumand are not recommended foruse as a front panel. A completecut and silk-screened panel isavailable from the source men-tioned in the parts list, or youcan make your own using trans-parent red acrylic. Secure themother board in place (top halfof case) and finally install thedaughter board uses three 13/4-inch standoffs. You're nowready to power up and use yourcombination function gener-ator and frequency counter.

Using your unitTable 1 shows a complete list

TABLE 1-FUNCTION GENERATOR SPECIFICATIONS

FUNCTION MIN MAX UNITS

Sine WaveTriangle WaveSquare WavePulse

0.10.10.10.1

2.5 Mega2.5 Mega2.5 Mega2.5 Mega

HzHzHzHz

Ampitude

Main Output 3.0 20 Vp-p- 20dB 0.5 6 Vp-p

TTL Pulse 50 5 VpCMOS Pulse 0.5 15 Vp

Duty Cycle 10 90 0/0

DC Offset -10 + 10 VDC

Sweep Generator

Sweep Width 1 1000 X Initial Freq.Sweep Time 1 20 Seconds

Frequency Counter

Input Sensitivity 20 100 Vp-pInput Range 0.1 150 Mega Hz

Input Impedance 50 1 Mega OhmsGates Times .01 10 SecondsError LSDStability 5Oppm C

of functions and specificationsof the unit.

The square wave output is inphase with the sine wave andthe triangle wave, but is 180 de-grees out phase with the TTLand CMOS pulse outputs. Thatfeature is useful for creating atwo-phase clocking system ifyou happen to be working withdigital equipment. The unit iscalibrated to give a frequencyrange of 0.1 Hz to 2.5 MHz. Theupper frequency limit can be ex-tended by adjusting variable ca-pacitor C108 and/or R129. Withthe component values that wehave given, the upper frequencylimit can reach as high as 4MHz..

Changing the values of thetiming resistors R115-R119 andR120-R124 will produce outputfrequencies as determined bythe formula 1/RC. That methodwill achieve a maximum sine -wave output of 10 MHz with anamplitude of 1 volt peak -to -peakabove 2 MHz. R -E

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EXPERIMENTING WITHADC FORYOUR PC

Add a variety of analog inputs tothe PC -based analog -to -digital convertor.

PC -BASED TEST INSTRUMENTATIONhas turned out to be a populartopic among readers. We con-tinue this ongoing series by in-terfacing new sensing devices (alinear displacement transducer,a piezoelectric transducer, anda microphone) to the analog -to -digital converter (ADC) dis-cussed in the January 1992 is-sue. If you're just getting startedwith this series, here's a briefreview of progress thus far.

Quick reviewThe heart of the system is a

PC I/O expander called the PC 10that adds 24 lines of digital I/Oby means of an 8255 Parallel In-put/Output (PIO), all on a single8 -bit expansion card. In theJanuary 1992 installment, weadded an outboard analog -to -digital converter (ADC), basedon an ADC0804. The ADC al-lows you to measure and cap-ture any 0-5 volt analog signal(e.g., temperature, displace-ment, and audio). The circuitincludes a variable -gain ampli-fier for low-level inputs, and aDC -offset adjustment for inputswith unwanted DC compo-nents. A temperature probe

shown in that article was builtaround the base -collector junc-tion of a silicon transistor. Withthe proper settings for ampli-fication and DC offset, a several -hundred millivolt change over a100°reeC temperature rangeproduced a digital outputspread over the full input rangeof the ADC0804.

In general, an ND converterand a PC can provide very low-cost solutions to measurementproblems that would ordinarilyrequire costly test equipment.Following are some ideas, prac-tical circuits, and software forinterfacing other types of de-vices. These ideas cover thethree most common types ofsensing: mechanical, electrical,and acoustic.

Mechanical sensingAs an example of mechanical

sensing, the author and afriend were contracted to mea-sure the displacement, impactforce, and velocity of elec-tromechanical rappers used inthe pollution -control industry.Factory smokestacks have en-vironmental controls that con-tain huge, electrostatically

JAMES J. BARBARELLO

charged metal plates. As thesmoke goes up the smokestack.it passes by those plates; theplates "pull" the suspended par-ticles to them, removing pollu-tion that would otherwise bereleased to the outside air. Parti-cles accumulate on the plates,and eventually have to be re-moved. To "clean" the plates,rappers (like giant solenoids)provide quick, hard jolts to theplates, breaking trapped parti-cles free in huge sheets that fallto the bottom of the smoke-stack. Our task was to deter-mine the characteristics ofexisting commercial rappers,and then determine whetherour customer's rapper could bemade better than the competi-tion's.

Our test instrumentationconsisted of an 8 -bit A/D con-verter hooked up to a computer,and fed by a rectilinear potenti- 65

1K

+5V

VIN

IC2

ADC0804

LINEAR A/D CONVERTORDISPLACEMENT (JAN 1992 FIG 2)

POTENTIOMETER

FIG. 1-INTERFACE A LINEAR displace-ment transducer to the PC 10 as shownhere. The wiper of the LDT drives theADC0804 directly. so remember to dis-connect the op -amp output (pin 7) fromthe ADC's input. (The original circuit wasshown in Fig. 2 in the January 1992 in-stallment.)

RED

PIEZOTRANSDUCER

BLACKO

Ve PHONEPLUG

FIG. 2-INTERFACE A PIEZOELECTRICtransducer as shown here. Make surethe red lead goes to the tip and the blacklead to the ring of the plug. Also, to avoidfeeding DC voltage into the transducer,disconnect the J1 end of Ri.

ometer (also called a linear dis-placement transducer, or LDT).LDT's are precision potentiome-ters that move linearly, ratherthan circularly. Even at surplusprices, LDT's aren't cheap($20-$50), but they do a greatjob. Figure 2 in the January1992 issue shows the completeADC circuit; we simply suppliedit with the input shown here inFig. 1. Note that we power theLDT directly with a 5 -volt DCsupply, so neither amplificationnor DC offset were required. In-stead, we drive the ADC0804(IC2) directly, as shown in thefigure.

If you use this type of arrange-ment, be sure to disconnect theop -amp's output (pin 7) fromthe ADC's input (pin 6). In addi-tion, make sure the potentiome-ter has a resistance of at least1K, so as not to draw too muchcurrent from your PC's powersupply. Also, the mechanicallinkage between the LDT andthe rapper must be firm so thereis little or no slippage at thespeeds encountered. Other -

66 wise, the potentiometer will not

+5V(PIN25 OF P1)

R1210K

OFFSET

AUDIOINPUT

0

R1510K

INPUTLEVEL

WitR610K

R13100KNIA

R8100K

IC1-a741

R510K

R141MEG 117

GAIN 10K 6to-AM-6-

-V

ICI -b741

+VR910K

--ITO AD

V

0-111-:82-IljiFIG. 3-INTERFACE AN AUDIO SOURCE as shown here. The nonsequential partnumbers occur to keep numbering consistent with the original circuit.

FIG. 4-GRAPHICAL OUTPUT from GRAFDATA.BAS (Listing 2), which allows you todisplay as many as 1000 data points captured by ADC.BAS (Listing 1).

give a true indication of dis-placement. This type of setupwould also be useful for measur-ing the movement of solenoids,pistons, cams, and similar de-vices.

Using that circuit, we ob-tained a series of outputs thatshowed exactly how the rapper'splunger moved a quarter of asecond after it triggered. Eightbits of digital data made it easyto calculate the rate of change ofdisplacement (velocity), as wellas the maximum displacement.We determined impact forceusing strain gages.

The only problem we had wasin determining just when toread the LDT's resistance. Thesolution turned out to bestraightforward, as we'll seemomentarily.

Electrical sensingThe temperature probe de-

veloped last time is one exampleof electrical sensing. Anothergood sensing device is piezo-electric material, available inboth film and crystal form. Aninexpensive source of piezo-electric crystal is Radio Shack'sPiezo Transducer (273-073).Simply break open the plasticcase, and you have a circularpiezoelectric transducer withred and black leads. When flex-ed in any way, the transducerproduces a voltage that variesproportionally to the amount offlexing.

A piezo transducer can beused to measure force of im-pact, or the amount of bendingand flexing. Figure 2 shows howto connect a piezo transducer to

LISTING 1

1 REm++++++++++++++++++************************+++*2 REM** ADC.BAS - V910803 - JJ Barbarello *3 REM** Capture/Store Analog Data with PcA/D-MATE *4 REm*** ********* ***** ******** ************ ****** ***

10 CLS : DEFINT A, X: DIM A(1000): GOSUB 370: LOCATE 1, 2320 PRINT "PcA/D DATA COLLECTION SYSTEM": LOCATE 2, 1: PRINTSTRING$(79, 220)30 LOCATE 5, 1: PRINT SPACE$(79); : LOCATE 5, 10

40 LINE INPUT "Enter Time (0-3600 seconds) between samples...";interval$50 interval = VAL(interval$)60 IF interval < 0 OR interval > 3600 THEN BEEP: GOTO 3070 LOCATE 7, 10: PRINT 'Press <Enter> to begin, or <Esc> toabort...";80 GOSUB 350: IF AS = CHR$(27) THEN CLOSE : END90 LOCATE 5, 10: PRINT SPACES(60): LOCATE 7, 10: PRINT SPACE$(60)100 LOCATE 10, 22: PRINT "DIGITAL DATA (0-255) ": LOCATE 12, 19

110 IF interval > 0 THEN PRINT "SECONDS BETWEEN SAMPLES: "; interval120 LOCATE 13, 29: PRINT "SAMPLE NUMBER: "

130 LOCATE 16, 20: PRINT "Press <Esc> to End Sampling...";140 acount = 1: xsample . 1

150 told = VAL(MIDS(TIME$, 4, 2)) * 60 + VAL(RIGHT$(TIME$, 2))160 IF interval = 0 THEN GOTO 210170 T = VAL(MIDS(TIMES, 4, 2)) * 60 + VAL(RIGHTS(TIMES, 2))180 IF T = 0 AND (told - T > interval) THEN told = told - 3600190 IF INKEY$ = CHR$(27) THEN GOTO 260200 IF T - told > 0 THEN told = told + interval ELSE GOTO 170210 OUT ADD + 2, 0: OUT ADD + 2, 1

220 x = INP(ADD): LOCATE 10, 44: PRINT USING "###"; x230 LOCATE 13, 44: PRINT xsample; : xsample = xsample + 1

240 IF acount < 1001 THEN A(acount) = x: acount = acount + 1

250 IF INKEY$ <> CHR$(27) THEN GOTO 160260 BEEP: LOCATE 16, 15270 PRINT "Press <Enter> to save data, <Esc> for no save...";280 GOSUB 350: IF ASC(A$) = 27 THEN CLS : END290 LOCATE 16, 15300 LINE INPUT "Enter File Name To Save Data ex: TEST01.ADD)..."; f$310 OPEN "r", 1, f$, 2: FIELD 1, 2 AS dl$320 LOCATE 18, 20: PRINT "Saving Data...";330 FOR i = 1 TO acount: LSET dl$ = MKIS(A(i) : PUT 1, LOF(1) / 2 +

1: NEXT340 PRINT "Done. Press ANY key."; : AS = INFJT$(1): CLOSE : CLS

END350 A$ = INKEY$: IF A$ "" THEN GOTO 350360 IF ASC(A$) = 13 OR ASC(A$) = 27 THEN RETURN ELSE BEEP: GOTO 350370 OPEN "R", 1, "HWADDRES.DAT", 4: FIELD 1, 4 AS AS380 GET 1, 1: ADD = VAL(A$): CLOSE : DEF SEG = 64: OUT ADD + 3, 146:

RETURN1 REM** GRAFDATA.BAS2 REM** Graph PcA/D-Mate .ADD File Data (Requires Graphics Monitor)3 REM** V910802 - JJ Barbarello4 REM**10 CLEAR : DEFINT I -J, Y: KEY OFF: CLS20 COLOR 0, 7: LOCATE 3, 27: PRINT " GRAPH PcA/D-MATE DATA "; : COLOR7, 0

30 LOCATE 10, 20: INPUT "Enter File Name (ex: TEST1.ADD)..."; DENS40 OPEN "R', 1, DFN$, 2: FIELD 1, 2 AS DS: IF LOF(1) > 0 THEN GOTO 8050 CLOSE : KILL DFN$: BEEP: LOCATE 25, 1360 PRINT "That File Doesn't exist. Press AM key to try again...";70 A$ INPUT$(1): CLS : GOTO 2080 LOCATE 21, 34: COLOR 16, 7: PRINT Reading data "; : COLOR 7, 0

90 DIM I((LOF(1) / 2) + 3)

100 FOR I = 1 TO LOF(1) / 2: GET 1, I: I(I) = 190 - CVI(DS): NEXT110 LOCATE 21, 34: PRINT SPACE$(20)120 LOCATE 12, 20: PRINT "File Has"; LOF(1) : 2; 'Samples."130 LOCATE 14, 20: INPUT "Enter Start Sample To View..."; ISTART140 LOCATE 15, 20: INPUT 'Enter End Sample To View"; IFIN150 IF IFIN - ISTART > 1000 THEN IFIN = ISTART + 999160 I(I) = I(I - 1): I(I + 1) = I(I): I(I + 2) = I(I + 1)170 YINC = 500 / (IFIN - ISTART)180 IF (IFIN - ISTART) > 499 THEN istp . 2 EASE istp = 1

190 SCREEN 2: LOCATE 2, 1: PRINT "SAMPLES": LOCATE 3, 1: PRINT "

200 LOCATE 4, 1: PRINT "Start:"; ISTART: LOCATE 5, 3: PRINT "End:";IFIN210 LOCATE 20, 1: PRINT "Press <ESC>": LOCATE 21, 3: PRINT "TOEnd..220 LINE (138, 0)-(138, 190): LINE (138, 196)-(639, 190): J = 139230 FOR I = 0 TO 152 STEP 38: LINE (128, 1)-(137, I): NEXT240 LOCATE 1, 13: PRINT "5.0": LOCATE 24, 16: PRINT '0";250 LOCATE 12, 12: PRINT "VOLTS";260 FOR I = ISTART TO IFIN STEP istp270 LINE (J, I(I))-(J + YINC, I(I + istp)): J = J + YINC: NEXT I280 AS = INKEY$: IF A$ = "" THEN 280290 IF ASC(A$) = 27 THEN SCREEN 0: END ELSE BEEP: GOTO 280

our circuit. We want only thevoltage generated by the piezosensor, so disconnect the J1 end

of R1, shown in Fig. 2 last time(R1 provided + 5 -volts DC to thetemperature probe). With no in-

put signal, adjust R11 for max-imum gain, and R12 so outputis about 2.5 -volts DC. (The lat-ter setting allows the piezo volt-age to vary from that quiescentlevel.) You might also want toadjust the value of R3 so thatthe piezo sensor produces max-imum indication at its max-imum output.

To test the circuit, use a pieceof masking tape to secure thepiezo sensor to a flat surface,making sure you aren't flexingit. 'Pap the surface firmly andnote the response. In actualuse, you would mount the sen-sor using a clamping device orflexible adhesive. This type ofdevice is useful for measuringapplied impact, oscillation afterimpact, or amount of flex orbend.

Acoustic sensingYou've probably seen audio

signals displayed on an os-cilloscope. Now imagine "freez-ing" those signals-i.e., storingthem in digital form. Scientistscapture digitized audio in thisway to study the sounds thatwhales, birds, and other ani-mals make. In digitized form,it's easy to compare and con-trast different sounds to deter-mine which have similarcharacteristics, or to look atother factors that wouldn't oth-erwise be obvious.

To accommodate a micro-phone input, we modified theADC circuit as shown in Fig. 3.The changes allow us to in-crease the gain of IC1-a to amaximum of 100, and to attenu-ate high-level inputs. Gain is de-termined by the ratio R14/R6 = 106/104=102= 100. If thepart numbering in Fig. 3 seemsstrange, it's because we tried tostay consistent with the maincircuit shown in Fig. 2 in Janu-ary Note that in the Januaryversion, R6 was 100K; here wedecreased its value to 10K. Also,we no longer use R1 -R4.

In operation, first set R12 tomid -value. Then adjust R14 formaximum range, as describedlast time. Last, readjust R12 asnecessary to set the quiescentlevel to about 2.5 -volts DC. Forexample, a microphone mightprovide a maximum output 67

LISTING 21 REM** GRAFDATA.BAS2 REM** Graph PcA/D-Mate .ADD File Data (Requires Graphics Monitor)3 REM** V910802 - JJ Barbarello4 REM*.10 CLEAR DEFINT I -J, Y: KEY OFF: CLS20 COLOR 0, 7: LOCATE 3, 27: PRINT " GRAPH PcA/D-MATE DATA "; : COLOR7, 0

30 LOCATE 10, 20: INPUT "Enter File Name (ex: TEST1.ADD)...";40 OPEN "R", 1, DFN$, 2: FIELD 1, 2 AS D$: IF LOF(1) > 0 THEN50 CLOSE : KILL DFN$: BEEP: LOCATE 25, 1360 PRINT "That File Doesn't exist. Press ANY key to try again...";70 A$ = INPUT$(1): CLS GOTO 2080 LOCATE 21, 34: COLOR 16, 7: PRINT " Reading data "; : COLOR 7,90 DIM I((LOF(1) / 2) + 3)100 FOR I = 1 TO LOF(1) / 2: GET 1, I: I(I) = 190 - CVI(DS): NEXT110 LOCATE 21, 34: PRINT SPACES(20)120 LOCATE 12, 20: PRINT "File Has"; LOF(1) / 2; "Samples."130 LOCATE 14, 20: INPUT "Enter Start Sample TO View..."; ISTART140 LOCATE 15, 20: INPUT "Enter End Sample To View"; IFIN150 IF IFIN - ISTART > 1000 THEN IFIN = ISTART + 999160 I(1) = I(I - 1): I(I + 1) = I(I): I(I + 2) = I(I + 1)170 YINC = 500 / (IFIN - ISTART)180 IF (IFIN ISTART) > 499 THEN ISTP = 2 ELSE ISTP = 1190 SCREEN 2: LOCATE 2, 1: PRINT "SAMPLES": LOCATE 3, 1: PRINT--"200 LOCATE 4, 1: PRINT "Start:"; ISTART: LOCATE 5, 3: PRINT "End:";IFIN210 LOCATE 20, 1: PRINT "Press <EEC>": LOCATE 21, 3: PRINT "ToEnd..."220 LINE (138, 0)-(138, 190): LINE (138, 190)-(639, 190): J = 139230 FOR I = 0 TO 152 STEP 38: LINE (128, I)-(137, I): NEXT240 LOCATE 1, 13: PRINT "5.0": LOCATE 24, 16: PRINT "0";250 LOCATE 12, 12: PRINT "VOLTS";260 FOR I = ISTART TO IFIN STEP ISTP270 LINE (J, I(I))-(J + YINC, 1(I + ISTP)): J = J + YINC: NEXT I280 AS = INKEY$: IF A$ = "" THEN 280290 IF ASC(AS) = 27 THEN SCREEN 0: END ELSE BEEP: GOTO 280

voltage of 0.5. Adjust R14 so themaximum is about 4.0 volts.Then readjust R12 so the no -sig-nal (quiescent) value is about2.5 -volts DC. Now you'll get thebest resolution from the circuit.

SoftwareWe wrote two programs for

data capture and display. List-ing 1 shows the capture pro-gram (ADC.BAS), and Listing 2the display program ( GRAF-DATA.BAS)-both are availableon the RE-BBS (516-293-3000,1200/2400, 8N1) as a file calledPCADMAT2.LST. Figure 4shows sample output fromGRAFDATA. Enhanced ver-sions of both programs areavailable on disk from the au-thor for a nominal fee; see thesidebar for details.

ADC.BAS is a general-pur-pose data capture and storageutility lb use it, you must createa data file called HWAD-DRES.DAT in the same directo-ry as the program. The file con-tains the decimal address of thePC 10 card. You can create thefile with any text editor or wordprocessor capable of storingtext in ASCII format. Assuming

68 your card is set to the default

DFN$GOTO 80

0

address (640), create a one -linefile that contains "640D" (with-out the quotes) followed by acarriage return.

Connect the ADC circuit toyour PC and run ADC.BAS. Itinitializes the PC I0 card, thenasks you for the interval (in sec-onds) to wait between samples.If you want continuous samples(with no delay), enter 0. Other-wise, you can enter any numberbetween 1 and 3600 (one hour).When you press Enter, sam-pling begins.

The program displays threepieces of information: currentdata (line 100), time betweensamples (line 110), and currentsample number (line 120). PressEsc at any time to end sampling(line 130).

Lines 150-200 take care of in-terval timing. The samplingprogram showed last time useda timing loop that was system -dependent; the current versionreads the system clock, hence issystem -independent. Samplingtakes place in lines 210-250; asmany as 1000 samples are savedin array A.

When you press Esc to endsampling, execution continuesat line 270. If you press Esc

R1

0 efAi10K

TRIGGERINPUT

+ 5V

R210K

TRIGGER01 OUTPUT

2N2222

FIG. 5 -DIGITAL TRIGGER CIRCUIT al-lows the PC 10 to start reading databased on the appearance of a predeter-mined signal. Connect this circuit be-tween that signal and an unused PC 10input, and modify the software accord-ingly.

ORDERING INFORMATIONThe following items are available

from JJ Barbarello, 817 TennentRoad, Manalapan, NJ 07726. Complete PC 10 Board with PCboard and all components (part#PCIO)-$39.95 An ADC0804 and a calibratedPN222A temperature sensor tran-sistor (part #ADC) --$8.00 PC 10 software, including com-piled and source code versionswith continuous and interval sam-pling and data logging/listing.

(part # ADC -S)-$8.00. Software from this installment,including a menu -driven, compiledprogram (with source code), ex-panding on the identified functionsand adding discrete data listing,graphed data sample selection/value display, and other features(part #ADM -S)-$10

Specify part number(s) and sendcheck or Money Order.

The author will be glad to answer anyquestions, but they must be ac-companied by a self-addressedstamped return envelope.

again, data is abandoned and theprogram ends. If you press Enter,the program requests a file namefor storing the data. Specify thecomplete file name, includingany path and extension (e.g.,C:\SUBl\TESTOLADD.) If youdon't specify a complete path, thefile will be stored in the currentdirectory. If the file already exists,current data will be appended tothe end of the file.

GRAFDATA. BAS allows you toplot your data on -screen. Whenyou run the program, it asksyou to specify a data file. As withADC.BAS, specify the full filepath if the file is not in the cur-

(Continued on page 76)

WORKING WITHLED'S

We continue our survey of optoelectronicprinciples and systems, with an in-depth

look at practical LED chaserand bar -graph displays.

RAY MARSTON

LAST MONTH, BEGAN INTRODUC-ing the gene subject of op-toelectronics, and we examinedlight -emitting lodes (LED's)and several pract LED flash-ers in detail. In thi rticle, wellexamine several practical LEDchaser (or sequencer ot, andbar -graph displays.

Chaser principlesOne of the most popula

displays is known as a chalso called a sequencer. Thwhen an IC drives an LED arraso that each LED (or small'groups thereof) turns on and offin a fixed, periodic sequence,that appears as a ripple of lightrunning along a chain. TheLED's don't necessarily have tobe arranged linearly, and can beplaced in any desired geometricpattern, to alter the visualeffect.

The most popular CMOS ICwhich is used for that purposeis the CD4017B, which is a de-cade counter/divider IC with 10decoded outputs, each capableof directly driving an LED dis-play. If desired, the outputs canbe coupled back to the IC con-trol terminals to make the de-vice count to (or divide by) anynumber from 2-9, and eitherstop or recycle.

The CD4017B is easily cas-caded for use in multi -decadefrequency division, or for use incounters with any number ofdecoded outputs. It's extremelyversatile, and it can easily be

used in a chaser orseiluencerLED display of any desiredlength.

Figure 1 shows the pino ofa CD4017B, with decoded ut-puts in arithmetic order. Figure2 is its timing diagram: theCD4017B is a 5 -stage Johnsoncounter with CLOCK, RESET, andCLOCK INHIBIT inputs. The coun-ters are advanced with eachpositive -going clock pulse,when the CLOCK INHIBIT andRESET inputs are low. At anytime, nine of the 10 decodedoutputs are low, while the re-maining one is high.

The 10 outputs go high se-quentially in step with theclock, with the selected output

+3-15V

16t

VDD

IC1 4

CD4017B7

4CLOCK

10 DECODEDDECIMALOUTPUTS

13 CLOCKIN IIIBIT

5RESET 8

11

CARRY 12

OUT

FIG. 1-PINOUTS OF THE CD4017B de-cade counter divider, with its decodedoutputs shown in ascending arithmeticorder. The clock is inhibited by a high onpin 13, and the counter is reset by a highon pin 15 and advances on a positive -going clock transition.

staying high for one full clockcycle. The CARRY OUT goes highfor one clock cycle out of every10 clock cycles, and it can beused to ripple -count moreCD4017B's in a multi -decadecounting application. Thecounting cycle is inhibited bysetting CLOCK INHIBIT high. Ahigh on the RESET input clearsthe counter, and sets the "0" -output high.

CD4017B chaser circuitsFigure 3 shows a practical

CD4017B 10 -LED chaser, withICI, a 555 astable multivibrator,which is used as a variable -speed clock generator. TheCD4017B becomes a decadecounter by grounding pins 13(CLOCK INHIBIT) and 15 (RESET).The visual display will appear asa moving dot sweeping from leftto right (or from LED's "0"-"9")in 10 steps, as the outputs gohigh and turn the LED's on se-quentially. They can either bearranged in a straight line, orconfigured circularly, so thatthe dot appears to rotate.

The LED's shown in Fig. 3en't current -limited. Man-

cturers don't give a max -short -circuit current for

D4017B, but practical ex -e dictates a value some-

where between 10-15 milli -amps. The maximum dissipa-tion per gutput on some datasheets is ielp milliwatts, so up to7 volts DC can be developedsafely across a CD4017B outputstage at maximum current.

Each LED is gonnected be-tween output and ground, andcan have a maximum supply of9 volts DC, for a 2- It DC dropacross each LED that% lit. Above9 volts DC, use the versionsl- own in Fig. 4, which Intainsa :urrent-limiting resis 6r, andis capable of being used withsupplies up to 12 volts DC.

Figure 5 shows a possibleequivalent of the circuit in Fig.4. that uses a 15 -volt DC supply,that also illustrates a major de-sign flaw. When one LED is on,the anodes of the others aregrounded, so R1 reverse -biasesthem. Due to low LED reverse -voltage ratings, you'll often findthat an LED that's off will actlike a Zener diode at about 5 69

CLOCKINPUT

"2"

"4"

"5"

CARRY]OUT

FIG. 2-WAVEFORM TIMING DIAGRAM OF THE CD4017B, with its RESET and CLOCKINHIBIT terminals (pins 13 and 15) grounded.

1r-+ Cl

111F4,

2

R1

1.5K

R21.5K

R3 6100K

7

ICI555

14

3

+9V

16

C2

100µF

CLOCK

vIC2

CD4017B

RESETCLOCK

INHIBIT

3 2 4 7

LED1

LED2 LED3 LED4 LEDS

O ® ®10 1

LED6 LED7

04/ Pi

15

13

8

5 6 9 11

LEDS LED9 LED010

//

FIG. 3-A 10 -LED CHASER OR SEQUENCER that can be used with supply voltages upto only 9 volts DC, and which produces a "moving -dot" display.

14

+6-12V

t 16

CLOCK

vIC1

CD4017B

RESETCLOCKINHIBIT

Vim

15

13

8

3 4

LED27

LED3

®1

10LED4

pei

1

LEDS

Ori

LED65 6

LED7

® ®Pei

LED10

70 FIG. 4-A 10 -LED CHASER, WHICH USES up to a 12 -volt DC supply.

8V

2V

P(/

+ 15V

CD4017B

10mA

5V111

47052

"OFF"LED'SON LED DRIVEN

TO ZENER LEVEL

4,15mAAT 5 VOLTS

FIG. 5-A POSSIBLE EQUIVALENT toFig. 4, which uses up to a 15- volt -DCsupply.

volts DC, and possibly destroy-ing a CD4017B output stage.

When a CD4017B drivesLED's in moving -dot mode, theycan be connected directly to theIC outputs if supply values areno more than 9 volts DC. Forhigher supplies, you'll need cur-rent -limiting resistors. Severalsuch display circuits are shownin Figs. 6-12.

Alternative LED displaysThe output stages of the

CD4017B can either source orsink currents equally well. Fig 6shows IC2 used in sink -mode ina moving -hole LED display;nine of the 10 LED's are on atany given time, while one turnsoff sequentially. If the LED's arearranged circularly, they seemto rotate. Since all LED's exceptone are on at a time, they allneed current -limiting resistors.

Moving -dot displays aremuch more popular than themoving -hole variety. The typeshown in Fig. 3 can be designedto use fewer LED's just by omit-ting the unwanted ones, butthen the dot moves intermit-tently or scans, since IC2 takes10 clock steps per sequence,and all the LED's will be off dur-ing the unwanted steps.

If a continuously -moving dis-play with fewer than 10 LED's isneeded, connect the first un-used CD4017B output to pin 15(RESET), as indicated in the 4-LED version shown in Fig. 7. lbachieve an intermittent displayusing a controlled number of offsteps, just connect the desiredunwanted output to pin 15RESET). Or, in other words, movethe connection going to pin 10

of IC2 to pin 9. In that type of anintermittent display, the LED'swill light for four cycles, goblank for four cycles, and thesequence then repeats.

Figure 8 shows a visually at-tractive 4 -LED, 5 -step se-quencer. Initially, all four LED'sare on, and then turn off se-quentially until they're all off inthe fifth step, as shown in theaccompanying table. The LED'sare effectively in series, and thebasic circuit can't drive overfour LED's.

Figure 9 shows another ver-sion; here, the CD4017B does a10 -step sequence, with LED 1on from steps "0"-"3," LED 2 onfor "4"-"6," LED 3 on for "7"and "8," and LED 4 on for step"9." The display will acceleratefrom LED 1-LED 4, not justsweeping smoothly from oneLED to the next, and the cyclethen repeats ad infinitum.

Figure 10 shows such a cir-cuit modified to produce an in-termittent display, where thevisual acceleration occurs for 10clock cycles, the LED's all blankfor 20 cycles, and then thecounting cycle repeats. WhenIC2 is in a ± 10 mode as shownin Figs. 9 and 10, pin 12 (CARRYouT) produces an output eachtime IC2 does a decade count,which is used to clock IC3(which is connected in ± 3mode), with its "0" output fed toQl.

For the first 10 cycles of a se-quence, the "0" output of IC3 ishigh, and Q1 is biased on, soIC2 acts as shown in Fig. 9, withthe LED's turning on sequen-tially through Ql. After the 10thclock pulse, the "0" output ofIC3 goes low, turning Q1 off; theLED's can no longer light, butIC2 keeps counting. After the30th clock pulse, the "0" outputof IC3 again goes high andturns Q1 on, reenabling the dis-play.

Figure 11 is a simple multi-plexed display, where IC3 andQ3 enable or disable a bank ofLED's. Figure 11 is yet anotherexample of a multiplexed dis-play, which uses three lines ofsix intermittently -sequencedLED's. They're each sequen-tially enabled via IC3 and indi-vidual gating transistors, only

+9V

LED1 LED2 LED3 LED4 LEC5 LED( LED7 LED8 LED9 LED10

R1

1.51<7

R21.5K

R3100K

C1

1µF

IC1

555

itR4 R6 R7 R8 R9

4700 4AI 4700 470D 471:61 4701.1.

2 4 7 10

4

10 R11 R1 R13of 4700 4705547052

5 6 11

3

0 1

CLOCK

V8

3" 4 '5"IC2

CD4017B.,LOCK

INHIBIT13

6 '7 8 "9

VRESET

15

16

FIG. 6-A 10 -LED "MOVING -HOLE- DISPLAY.

1R51K

R21.5K

R3 6

2100K f--

+ Cli1µF

7

IC1

555

14

3

+ C. V

C2

(Mi.&

)1T-

16

CLOCK

VDD

IC2

CD4017E

RESET

CLOCKINHIBIT

3

LED1(!)

LED2 LEE3

10

13

8

C2

100µF

)1+

FIG. 7-A 4 -LED CONTINUOUS "MOVING -DOT" DISPLAY. To get an intermittent "mov-ing -dot" display using a 50% "blanking" period, just change pin 10 (or output "4") topin 9 (or output "8").

R11.5K

7'

R21.5K

R3100K

C1

IvF

I

+-9V

ICI555

16

4

3CLOCK

Uss

IC2CD40178

3 D1 2 D2 4 031N41481 1114148-i- 1N4148

LED1® LED2® LEDE®44\ \44

RESETCLOCKINH IBITV

7

LED4

15

13

8

C2

100µF

STEPNUMBER

2 3 4 5 6

LED1 ON OFF OFF Off OFF ON

LED2 ON ON OFF OFF OFF ON

LED3 ON ON ON OFF OFF ON

LED4 ON ON ON CJ OFF ON

FIG. 8-A 4 -LED, 5 -STEP SEQUENTIAL TURN-OFF DISPLAY.

one line at a time; if you want,you can expand this version stillfurther to control a 10 -line. 100 -LED, matrix display.

Figure 12 shows a 4 -bank. 5 -

)I +

step, 20 -LED chaser; the fourLED's are in series in each of thefive CD4017B outputs, so fourLED's are lit at any one time.Each lit LED drops about 2 volts 71

72

R1

.5K

7

R21.5K

R3 6100K(

+ C1

1µF

I

IC1

555

+9V100µF

16

14CLOCK

DD

IC2CD4017B

RESETCLOCKINHIBITV

3 2 4 7 10 11 5 6 9

DIY D2Y D3r D4r NT D6 D7V D8= D9!

LED

Pei

LED2 LED3 ED

11

15

13

a

D1 - Da1N4148

FIG. 9-A 4 -LED CONTINUOUS "ACCELERATOR" DISPLAY, where the pattern of thedots appears to accelerate from left to right.

+9V A

can use the LED's as either abar- or dot -graph display. In abar -graph display, the input val-ue is indicated by the totalnumber of LED's that are lit. Inthe dot display, the input valueis indicated by the relative posi-tion of just one lit LED.

Special IC's are available forbuilding LED analog displays,the most useful examples beingthe U2X7B family from AEG,and the LM3914 family from Na-tional Semiconductors. TheU2X7B family consists of sim-ple, dedicated devices, which

R1

R21.5K

7

R3 6100Kn

2

C1

T1p.F

I

IC1

555

16

43

CLOCK

0

VDD CARRY OUT

IC2 RESET

CD4017B CLOCK INHIBIT

1612 14

3 2 4 7 10 11 5 6 9

ply my my NY D5,7 D6 D7Y D8= D9I

ql LED1

D9:1N4148

LED2 LED3

11 8

15

13

LED4

FIG. 10-A 4 -LED INTERMITTENT "ACCELERATOR" DISPLAY, where the "accelera-tion" occurs for 10 out of every 30 clock steps.

+9VA

CLOCK VDD

IC3CD4017B

RESET

CLOCKINHIBIT

.3. vss

.1E215

100aF

3

R412K

012N3904

7

13

R1

1.5K

7

R21.5K

R3 6100K12

Cl1µF

I

IC1

555

16

4

3CLOCK

0"" "

3

VD,

IC2CD4017B3

4 7

OLED4

10

,C)LED5

CARRY OU1 12 14

RESET 15CLOCK INHIBIT 13

Vss

1 8

C.)LEN

LED70,

LED8 /OD9O SOLED

LED10

1D

1

12

C)3DL1E4D

Lg 14/ LIT Lfp Lfp

FIG. 11-A MULTIPLEXED 6 -LED x 3 -LINE MOVING -DOT DISPLAY, in which the dotmoves intermittently along the lines.

DC: that's 8 volts DC for eachLED bank that's on, so the sup-ply voltage must be greater thanthat for the circuit to work. Agreater number of LED's can beused in each LED bank if thesupply voltage is correspon-dingly increased to handle theadded load.

Bar -graph displaysAnother multi -LED indicator

circuit is the analog version,which drives a chain of linearly -

spaced LED's. The number ofLED's that are lit is proportionalto the voltage applied to theLED -driver, so the circuit actslike an analog voltmeter. You

16

CLOCK VIC3

CD4017B

RESET

CLOCKINHIBIT

012N3904

2 43

R4

12K

7

03

15

13

R612KVVS,

2148904

C2

10011F

can be usefully cascaded todrive up to 10 LED's in bar-

graph mode only, the membersbeing the U237B, U247B,U257B, and U267B. TheLM3914 family is more complexand versatile by comparison,and are easily cascaded to driveup to 100 LED's in either bar -graph or dot -graph mode. Bothvarieties of IC's are consideredto be bar -graph drivers.

+9V- 12V

/

R1

1.5K

R2

1.5K

R3 6

r* 100K -2

+ Cl71µF

..1.

7

ICI555

14

3

16

C247pFu

+R

VI11)

IC2CD4017B

3

RESET IV5s 8

CLOCK INHIBIT 13

LED1

LED2

LED3

ip(

LED4

10

LED5

iii i() LED13 ()

LED6 LED1 () LED1 ()frei 4( lei

LED7 LED 11 () LED15 ()

lei lie 6(LED8 LED' 2 () LED16 ()

iii /44 ii

5

LED17

LED18

LED19

LED20

FIG. 12-A 4 -BLANK 5 -STEP 20 -LED CHASER, for use with a supply above 9 volts DC.

TABLE 1-U2X7B INTERNALTRANSISTOR STATES AT

VARIOUS INPUT VOLTAGES

V,N,V 01 02 03 04 05

1.0 Off Off Off Off Off

0.8 Off Off Off Off On

0.6 Off Off Off On On

0.4 Off Off On On On

0.2 Off On On On On

0.0 On On On On On

IC -driven bar -graph displaysare inexpensive, superior alter-natives to analog meters. Theydon't stick, they're fast, andthey're unaffected by bothvibration and attitude. Theirscales can have any desiredshape, they can have mixedLED colors to highlight specialsections, and they can beequipped with over -range detec-tors that are activated by the

drivers to either sound analarm, flash the display, or both.

The linearity of such a bar- ordot -graph meter is considerablybetter than that of most analogmeters, and is generally about0.5%. The resolution dependson the number of LED's that areused; a 10 -LED version has ade-quate resolution for most hob-byist purposes.

Basics of the U2X7B IC familyThe AEG U2X7B IC family is

composed of four different 8 -pinDIP's, each capable of drivingfive LED's. The U237B andU247B pair produce a lineardisplay, and are used togetherwhen driving 10 LED's. TheU257B and U267B pair producea logarithmic display, and arealso used together when driving10 LED's. All four IC's in the fam-ily use the same internal circuit-ry, in block diagram form, asshown in Fig. 13.

All four IC's contain fiveSchmitt voltage comparatorswith unique thresholds feeding

TABLE 2-U237B INTERNAL STEP VOLTAGES

Device Step 1 Step 2 Step 3 Step 4 Step 5

U237B 200 mV 400 mV 600 mV 800 mV 1.00 V

U247B 100 mV 300 mV 500 mV 700 mV 900 mV

U257B 0.18V/-15 dBW

0.53V/-6 dBW

0.84V/-1.5 dBW

1.19V/+1.5 dBW

2.0V/+6 dBW

U267B 0.1V/-20 dBW

0.32V/-10 dBW

0.71V/-3 dBW

1.0V/0 dBW

1.41V/+3 dBW

TABLE 3-U237 IC FAMILYMAJOR SPECIFICATIONS

Parameter Mini-mum

Typ-

ical

Maxi-

mum

Supplyvoltage

8V 12V 25V

Inputvoltage

- - 5V

Input current - - 0.5mA

Max supply - 25 30current mA mA

Powerdissipation(at 60°C)

- - 690mW

Step -30 - 30tolerance mV mV

Stephysteresis

- 5 mV 10mV

Inputresistance

- 100 K -Outputsaturationvoltage

- - 1V

into transistor switches. Thethresholds are fixed by the tap-ping points on voltage dividerR1 -R6, which is powered usinga built-in voltage regulator:each comparator input is con-nected to pin 7.

All four IC's also contain aninternal 20-milliamp constant -current source, and the five ex-ternal LED's go in series be-tween it and ground (pin 1), asshown. Groups of LED's areturned on or off using the indi-vidual switching transistors. IfQ3 is turned on, it sinks 20 mil-liamps via LED's 1 and 2, so theyturn on, and LED's 3-5 turn off.

The U2X7B family has stepvoltages spaced at 200 -millivoltDC intervals, and Table 1 liststhe states of its five internaltransistors at various inputvoltages. At 0 volts DC input, allfive transistors are switched on,so Q1 sinks the full 20 milli -amps, and all five LED's are off.At 200 millivolts DC, Q1 turnsoff but all other transistors areon, so Q2 sinks the 20 milli -amps via LED 1, driving LED 1on and turning all others off. 73

vcc1

r - - 1-20mA

o_te7

VIN

L

R1 6i LED1

01 T

502 T

,i 6(4

03 %T.I

3,041.

I lor

05 I

1 PeitR6I -

1e -N LED5

BASIC INTERNALS AND .,. CONNECTIONS OF *U2X7B IC FAMILY

FIG. 13-BLOCK DIAGRAM OF a U2X7Bbar -graph driver, showing the basic ex-ternal connections.

VIN

(0 -1V)

-1+ 12 - 25V

VSTAB

U237B

LED1

LED2

LED3

LED4

LED5

FIG. 14-A 0 -1 -VOLT DC, 5 -LED, linear-scale bar -graph meter using a U237B.

With an input of 1 volt DC, alltransistors are off, the 20 milli -amps go to ground via the

(7)c\I LED's, so all five LED's are on.

The IC current is independentof the number of LED's turned

2 on, so minimal RF interference(RFI) is produced as it switches

co- transistors and LED's..ac.) The four IC's in the U2X7B2 family differ only with regard to

their step voltages, which are6 fixed by R1-R6 as shown in Ta-

ble 2, and the values for whichcc are also given in dBW (or dB rel-

ative to a watt). The linear -scale74 U237B and U247B pair of IC's

can be used to make a 10 -LED,1 -volt DC linear meter. The log-arithmic -scale U257B andU267B pair of IC's can be usedto make a 10 -LED logarithmicmeter with a full-scale value of2.0 volts DC, or + 6 dBW.

The reason for the correspon-dence between those two valuesis justified as follows. Since

P = E2/R,

where P is power, E is voltage,and R is resistance, then the as-sumption, for purposes of con-venience, is that:

R =1 ohm.

If so, then to convert voltageson the logarithmic -scale meterinto a quantity proportional topower (and not into power it-self), just square the voltage in-dicated, take the logo of theresult, and multiply by 10. If Ehas the unit of volts (as opposedto some fractional or multipleunit, like millivolts, for exam-

7 6 5

V V NIC1

U237B

GND

11. 2 3 41

LED7

LEDS

(1) LED10

_t \\

5

4

6 7 8V N V

IC2U247B

GND

3 21

FIG. 15-A 0 -1 -VOLT DC, 10 -LED, linear -scale bar -graph meter using a U237Band a U247B connected as a pair.

FIG. 16 -METHOD OF REDUCING thesensitivity of the bar -graph meter shownin Fig. 14, for use in a 0 -15 -volt DC, 5-

LED, linear -scale, bar -graph meter usinga U237B.

+ 12- 25V (REGULATED)

R1 8

10K

R2100K(SET FORSPECIFICDEVICE)

FIG. 17 -SIMPLE USE OF A transducerto show the value of a physical quantity.

ple), then P has the units ofwatts, and the units in dB arecalled dBV, since they're ex-pressed relative to a fixed valueof potential.

Likewise, if you wanted to ex-press dB in terms of power, thenthe proper terminology wouldbe dBW, or a similar unit for anyfractional unit of power. Thenumber of dBV is always doublethe number of dBW, since tak-ing the logm of both sides of thepower relation gives

log(P) = log(E2/R),= 2 x log(E) + log(R),= 2 x Iog(E) + log(1),= 2 x log(E).

For that reason,1 dBW = 2 dBV.

For example, in Table 2, forthe U267B and step 5, the entrygiven is 1.41 volts DC, or + 3dBW. On squaring that, you get

2 volts2, so 10 times its logic, is+3 dBW, and doubling thatgives + 6 dBW. Of course, whenever you take the logarithm of aquantity like voltage or power,you always operate on the nu-merical part alone, and ignorethe units. If you ever hear of anaudio or noise level that's ex-pressed in dB alone, with nounit appended to indicate "dBwith comparison to what," sucha specification is nonsense.

To express an amplitude in dBrelative to a unit of potential orpower with a multi -letter abbre-viation, just append the wholeunit, like dBmV for dB relativeto a millivolt. Sometimes, theterm dBm is used as an abbre-viation for dBmW, or dB relativeto a milliwatt.

Table 3 lists the specificationsof the U2X7B family. When driv-ing five red LED's, each with a 2 -volt DC forward drop, the mini-mum supply value requiredmust be 12 volts DC. Different -colored LED's with different for-ward drops can be used to-gether, if the supply voltage isadequate.

Although the IC input imped-ance is typically 100K, the IC be-comes unstable if the sourceimpedance is above 20K. Itshould ideally be kept under10K; if it's not, place a 0.01-µFcapacitor between pins 1 and 7for added stability.

Practical U2X7B circuitsFigures 14-19 show practical

U2X7B-family circuits; in all ofthem, the supply is 12-25 volts

+12-25V

DI1N5235

6.8VRI47K

(SET FORSPECIFICDEVICE)

014

1 -10K2N3906

R31 -10K

TRANSDUCER

R22.7K

8

V

ICIU237B

IN

GND

1

LED15

LED24

LED33

LED42

LED5

FIG. 18-AN ALTERNATIVE USE of atransducer to show the value of a phys-ical quantity.

01

1N4146

R11.2K

IN 112

56K

C1

.56

R356K

+12-25V

V

ICIU2678

6LED1

(-20 dBW)

LED2dBW)

LED3(-3 dBW)

LED40 dBW)

LED5(+3 dBW)

FIG. 19-A 5 -LED LOG -SCALE audio -level meter; a 10 -LED version is madeusing a U257B and U267B pair. in a fash-ion similar to the version shown in Fi3.15.

DC, but you'll have to rememberthe constraints previously men-tioned. Figure 14 shows a 0 -1 -volt DC, 5 -LED, linear -scalemeter using a U2X7B, and Fig.15 shows a U237B and U247Bpair used in a 0 -1 -volt DC, 10 -LED, linear -scale meter. The lat-ter circuit operates each IC asshown in Fig. 14, with supplyvoltages that are appropriate tofive LED's, but their input ter-minals are tied together, andthe LED's are alternated, toachieve a 10 -LED display.

Figure 16 shows how the full-scale sensitivity of the meter isreduced by feeding the input toIC1 via R1 -R2 -R3, using a ratioof 15:1, and giving full-scalesensitivity of 15 volts DC. Fig-ures 17 and 18 show how thecircuit shown in Fig. 14 can beused to display a physical quan-tity like light intensity or heat,as represented by the analog re-sistance R3 of a transducer. Inboth, the transducer is fed by aconstant -current source, so theinput voltage to IC1 is directlyproportional to the transducerresistance.

As shown in Fig. 17, constanttransducer current is derivedfrom regulated supply via R1 -R2, since regulated supply volt-age is large relative to the 1 -voltDC full-scale meter sensitivity.By contrast, as shown in Fig.18, constant current is ensuredvia D1 -Q1. Finally, Fig. 19 showsthe U267B used in a 5 -LED log-arithmic audio -level meter. A10 -LED meter can be madeusing a U257B and U267B pairas shown in Fig. 15. R -E

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76

ADC FOR YOUR PC

continued from page 68

rent directory. If the file exists,the program then tells you howmany samples it contains, andasks start and stop points forthe plot; the maximum numberis 1000.

The program (line 170) scalesthe graph to produce the widestpossible graph; lines 220-270graph the data. Press Esc to ter-minate the program. To "magni-fy" a limited portion of the dataset, run the program again, andenter appropriate start and endvalues (e.g., 350 and 450). Youcan print your graphs byrunning the DOS programGRAPHICS.COM beforeGRAFDATA.BAS. When the de-sired graph appears on thescreen, press PrintScrn. (Youmust have a compatible printerin order to print out any of thegraphs.)

Triggered samplingNow with the software under

our belt, it's time to finish the"rapper" story begun earlier.The rapper was triggered by anelectronic control circuit. Wetried to trigger sampling byhand, but it was impossible totell when the rapper was aboutto energize, and reaction timewas too slow and unsure foraccurate triggering. Our solu-tion was to create a trigger in-put. We tapped a digital signalfrom the control circuit thatchanged just before the rappertriggered.

The ADC circuit uses only 8 ofthe 24 input lines on the PC IO.What we did is use bit 0 of port Bas a trigger input. Then byadding a single line of code, wecould trip on either a low -to -high signal:145 IF (INP(ADD + 1) AND 1) = 0 THEN

GOTO 145or a high -to -low signal:145 IF (INP(ADD + 1) AND 1) = 1 THEN

GOTO 145

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If you want to add a slight delaybetween the trigger and thestart of sampling:

146 FOR I = 1 TO DELAYTIME : NEXTHowever, the delay time in thiscase would vary with the speedof your PC. In addition, makesure the trigger signal is TTL-compatible (logic low = OV, andlogic high = 5V). If it isn't, oryou want to buffer the triggersignal from your system, youcan use the circuit of Figure 5.Remember, this circuit invertsthe incoming trigger signal, soa positive -going trigger will benegative -going when it exits thebuffer circuit. Adjust added line145 accordingly.

ConclusionsThe analog world of nature is

not so distant from the digitalworld of computers. Simple cir-cuitry can allow your PC to func-tion as a digital eye, ear, or handon the external world. The cir-cuits and software shown hereare only the beginning. R -E

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We've already seen that Jonesand Bartlett has published THEgreat new wavelets book, and thatthe Ultrawave Explorer from theAware folks is definately one finecommercial wavelet study and de-velopment program.

But the big news is that I've justposted full working PC sharewarecopies of the Wavelet Packet Li-brary from Digital Diagnostics onGEnie PSRT as #365 WAVE-LET.PS.

Those of you into satellite dishesand microwave electronics are nowprobably familiar with Smith Charts,a handy graphical method of doingthings like impedance matching andtuning. I have written a PostScriptSmith Chart generator that lets youinstantly create all your own Smithcharts in any quantity, any size, any.resolution, and any where in yourpublication. Check GEnie PSRT'#367 SMITHCHT.PS for severalfreeware samples. Your download-ing cost on this is around twentyone cents.

Perpetual motion againI get an average of three to five

helpline calls a week on "free ener-gy" and other perpetual -motion top-ics. As we have seen in the past,perpetual motion is definitely real asa historic and ongoing societal phe-nomenon. We have also seen thattwo ongoing sources of perpetual -motion books, videos, and papersare High Energy Research andLindsay Publications.

Now, I personally feel that lookingfor any free -energy systems israther dumb. First, because the de-sirability of any free energy rankssomewhere between Herpes andAIDS. Why? Because this wouldobviously hasten the already ongo-ing entropic heat death of the plan-et. If someone does in fact find afree -energy system, they should bespanked and sent to bed withoutany supper. Or, better yet, choppedup and fed to the cows.

Second, because the odds ofyour accomplishing anything that'seven remotely useful involving freeenergy are stupendously low. Third,because your credibility starts outas less than zero and quicklyplummets. Owing to previousscams, the "not even wrong" re-search, and the "few -chips -shy -of -a -full -board" guilt by association.

And, finally, because there's somuch better to be doing. We're sit-ting on the greatest mountain ofnew hardware hacking chips, tools,info, and concepts anywhere ever.Stuff that's crying for hacker use,and stuff that is nearly certain toresult in lots of interesting and profit-able things. Why should you ignorethe obvious?

Several of the recent callers weremaking measurements that werejust plain wrong. Since I am one ofthe world's foremost experts ingathering incorrect, misleading, ormeaningless lab data, I thought wemight briefly focus on a few of the

NEED HELP?

Phone or write your HardwareHacker questions directly to:

Don LancasterSynergeticsBox 809Thatcher, AZ 85352(602) 428-4073

EON LANCASTER

ways that casual measurementsmay not end up what they appear tobe.

In general, you'll always want toassume that all meter pointers and,especially, all of your digital numericdisplays are lying through theirteeth. Or, if they are giving you acorrect reading, the odds are over-whelming that the meaning and theunderlying reasons for that readingare not at all what you had in mind.

Oscilloscopes do a far better jobthan the meters or digital displays atshowing you what is really comingdown. Even here, an uncompen-sated probe, the wrong setting, im-proper sync, an invisible glitch, anyoutband signals, or just a groundclip that is slightly too long cancause you wildly incorrect results.

It is only when the same tests arerun over and over again by differentpeople under different circum-stances that you can even remotelybegin to trust your instruments.Even when repeated, that trustshould only apply to the exact mea-suring conditions.

A ferinstance: Figure 1 shows youa seemingly simple method to mea-sure AC power. You connect yournew motors -and -magnets perpetualmotion machine load to the ACpower line through.an ammeter andthen separately measure the linevoltage. Since power equals voltstimes amps, you just multiply yourtwo readings together and you'llhave the input power. Right?

Wrong. Dead wrong.Let's temporarily forget about

any noise, spikes, back-EMFeffects, harmonics, and non-linearities that are certain to bepresent with your new motors -and -magnets load. Assume a pure sine -wave voltage and a similar currentwaveform. You have to take thephase of the current into account.You would get a zero phase shift 77

with a purely resistive load. In apurely inductive load the voltagewould lead the current by 90 de-grees. In a purely capacitive load,the voltage will lag the current by 90degrees.

Good old ELI THE ICE MAN. Thevoltage is ahead of the current in theeLi's L inductor; the current is aheadof the voltage in his iCe capacitor.

And if you have any purely activeload such as another generator,your current could end up phased by180 degrees. Sourcing, not sinking.

Your actual power will end up asthe voltage times the current timesthe cosine of the phase angle be-tween the two. If your voltmeterreads 110 and your ammeter reads4, your actual circuit power will be440 watts to a purely resistive load,ZERO to any purely inductive or ca-pacitive load, and MINUS 440 wattsto any purely active load. Or any-thing between, depending uponyour phase angle.

Why is the power zero to a purelyinductive load? Beceuse of the

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SYNERGETICSBox 809 -RE

Thatcher, AZ 85552(602) 428-4073

78

ACpower

line

4 amps

110Volts

Motors andMagnets

Load

FIG. 1-WHAT IS THE REAL POWER being consumed in this test circuit? There's noway to tell with the setup shown. But you can safely bet that it is probably notanywhere near 440 watts

phase angle. A math freak will tellyou the full cycle cross product of asine and its cosine is zero. Intu-itively, on the first quarter cycle, youhave positive voltage and current.On your next quarter cycle, you willhave positive voltage and negativecurrent. On the next, negative volt-age and negative current. And fi-nally, negative voltage and positivecurrent. Add them all up and aver-age them all out and you end up withzero real power.

Yes, you will get lots of back -and -forth reactive power that can giveyou real fits. And hack off your elec-tric utility. But your net real powerinto a pure inductive or capacitiveload is precisely zero.

Thus, as far as power goes, all thevoltmeter and ammeter readingsare totally meaningless. And theyare even less so in the presence ofnoise, back EMF's, sparking, or har-monics.

Measuring real powerSo how do you measure real and

reactive power? The trick is that youhave to multiply the instantaneousvoltage and current together. Thenyou sum to find the total power.

The power of any arbitrary wave-form is equal to the DC continuouspower that would give you exactlythe same amount of total heating ina purely resistive load.

You can do this measurementwith a real wattmeter, or by measur-ing the rotational speed and direc-tion of a watthour meter. Thewattmeters and watthour metersare often available through Fair Ra-dio Sales or Herbach and Rademan.

Electronically, you can use a multi-

plier chip or a special RMS power-

calculating circuit. Analog Devicesis one leader in low-cost powerchips of this type.

Or graphically, you can take plotsof all the exact voltage and currentwaveforms, split them up into timeslices so narrow that the voltage orcurrent does not change much, mul-tiply the results of those slices andthen sum the results.

Note that you must multiply firstand then add. Never vice versa.

But you still do have to be careful.Nonlinearities, pulses, harmonics,motor back-EMF effects, and noiserequire special treatment. And mostpower measurement schemes havea crest factor limit which ruins theiraccuracy on strong but narrowpulses. Especially things like spikesand glitches.

For these reasons, it is extremelydifficult to accurately measure yourinput power to a motors-and-mag-

+V

Typical ICSeries Regulator rMotors and

MagnetsLoad

FIG. 2-WHEN IS A REGULATOR not aregulator? Any time that your load triesto source (rather than sink) power, a typ-ical IC voltage regulator will shut downor else become unstable. There is nocurrent path to ground.

100 V

(open)

0 V

100µF 100uF

Energy = 0.5 Joules

(closed)

o o50V1 150V

1001.1FT I100.1F

Energy = 0.25 Joules

FIG. 3-QUICKLY CLOSE THE PERFECT AND LOSSLESS SWITCH. And half of yourcircuit energy will vanish without a trace. Where did the energy go?

nets perpetual motion machine. Ifyou do not know exactly what youare doing, all your results areguaranteed to be wildly wrong. Andso, of course, will be all of your con-clusions.

Figure 2 shows you a secondmeasurement pitfall that the recentcallers have all decided to ignore. Avoltage regulator is always a voltageregulator, right?

Wrong. Dead wrong.Most popular voltage regulators

are only capable of sourcing cur-rent. If the load starts sourcing anypower even briefly, there is no placefor the current to go, and the reg-ulator either shuts down or startsoscillating.

Thus, if you have a motors -and -magnets load, there could be timeswhen the back-EMF effects, spikes,commutator noise, or whatever, willtry to source power back into yoursupposed power source.

Put in another way, typical powersupplies and most regulators havewildly different impedances be-tween when they source and sinkpower.

Note that any normally con-nected Zener diode will behave pre-cisely the opposite-they are greatpower sinks but poor sources.

An output filter capacitor on yourregulator is essential for grabbingand smoothing out high -frequencyload sourcing variations.

Beyond proper output filtering,two ways around load sourcingeffects are to hang enough of a re-sistive load on your regulator thatthe regulator will always output a netsourcing current. Most batteriesare usually capable of sourcing andsinking any reasonable amount ofcurrent.

Figure 3 shows you yet anotherway to go astray. All bets are off if

there is any sparking or arcing. It isphysically impossible to instantlychange the voltage across a circuitcapacitor or the current through aninductor. The usual result when youtry this is sparking or arcing.

Take a 100-microfarad capacitorand charge it up to 100 volts. Yourenergy in any capacitor is...

E = 0.5CV2or, in this case, 0.5 Joules of storedenergy. Now, you close yourlossless switch so you have two ca-pacitors in parallel. The voltagemust, of course, drop in half, sincethe same charge is now spreadacross twice your plate area. And bythe same formula, you now haveonly 0.25 Joules of stored energy.

Question: Where did the rest ofyour energy go? If you have a non-lossless switch of resistance R, theanswer is easy. In the process ofcharging the second capacitor, theextra energy got burned up in yourresistor as heat during charging.But go through the chargng math,and you'll find that the loss of halfthe stored energy is a constantwhich is totally independent of thevalue of R!

If R equals zero, then you have toget a spark and radiated energy. Butyou still lose half of it, regardless ofhow good the switch is.

Thus, if there is any sparking orarcing whatsoever in your machine,your readings are once againabsolutely certain to be wrong.

Always think carefully about yourmeasurements and how they couldbe wrong or misleading.

Lumeloid and Lepcon filmsWe sure had a bunch of helpline

calls over the new materials stuff I

announced a column or two backand in our Hardware Hacker Ill re-prints. I've picked up some more

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IGITAL VIDEO STABILIZERELIMINATES ALL VIDEO COPYGUARDS

The transformer is 1:1600 Ohms, with a 1500volt breakdown rating.

phoneline

The zener diodes are3.9 volt devices, such

as a type 1N5228.

2200 pf

user

FIG. 4-A FCC PART 68 INTERFACE is required any time you connect any circuit ofyour own to the phone line. While this interface can be both simple and cheap, therequired submission and approval process is not.

isC

Phone LineLineInputs

+5V

3.58 Mhz Xtal

nc

111

0 0 0 0 0 0 0VCC C.00 DO ED FJ XOL'l XN

SC11211V'S V,F, ELI EL2 EDC VFW GE

0 00 0 0 0 0

T T T0.1µF 0.1µF 11.1F

FIG. 5-PRE-APPROVED PART 68 INTERFACE HYBRIDS are available, but they arerather expensive. Here is a caller -ID circuit that uses the Cermetek CH1845 DAAinterface and the Sierra SC11211 caller ID chip.

info, and have summarized where togo for more in our Lumeloid andLepcon Solar Resources sidebar.

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The key individual behind all this

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is one Alvin Marks and his companyof Advanced Research Develop-ment. Their OTC pink sheet stock istraded under the name Phototherm.This is strictly an unregistered bluesky security, and trading remains il-legal in Massachusetts, the issuingstate.

Marks is a credible, experienced,and independent researcher with along history of successful energy,optical -film, and pollution -controldevelopments. Among other things,he developed the cheap glassesonce used for 3-D movies.

And EPRI, that ultra -conservativeElectric Power Research Instituteelectric utility consortium has seenfit to fund Marks with a modest re-search grant. Albeit a paltry one byEPRI standards. Coffee money.

The two key patents that are in-volved in this are #4,445,050Device for Conversion of LightPower into Electric Power, and#4,574,161 An Ordered DipolarLight -Electric Power Converter.

There is very little .published todate. And all of it is single sourced.None appears to be peer reviewedor critiqued. A collection of reprintsis now available free on requestfrom Advanced Research Develop-ment. One original paper has shownup as Lumeloid Solar Plastic Filmsand Lepcon Submicron Dipolar An-tennae on Glass, from the 1990International New Energy Tech-nology symposium published by thePlanetary Association for Clean En-ergy, located in Ottowa, Canada.

As we've seen a number of timesin the past, you can quickly researchany technical topic by using theDialog Information Service at yourlocal library, and then can get anyreprint by using either interlibraryloan or the UMI reprint service.

So what is the big deal here andhow does it work? Your traditionalmethods of generating electricityfrom the sun are seriously flawed.The old mirrors -and -boilers methodinvolves a thermodynamic cyclewith a Carnot thermodynamic effi-ciency limit around 35 percent. Be-sides not downsizing very well.Silicon solar cells at a theoretical 26percent are even less efficient. Itseems that they can only accept"whole lumps" of quantum energy,

82 and have to throw the rest away as

heat. And, before Marks, any photo.synthesis scheme was well undersix percent efficient.

Efficiency is everything in solarpower. On a good day, you have oneincoming kilowatt per square meterto work with. Say a nickel an hour"avoided cost" income for a perfectconversion. Or two cents a day al-lowing for night and weather. Natu-rally, your bottom -line efficiency willusually be much less than your the-

oretical. Let your efficiency drop toolow and there's no way that solarcan be competitive. Get under thebottom -line efficiency of seven per-cent or so, and you will never beable to pay for your installation andland, owing to the time value ofmoney. The longer it runs, the moreit costs you for the financing.

But, alternatively, the nickel -per-

kilowatt -hour incoming solar energyon a 2200 square foot house roof

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adds up to over $3000 a year.Which is lots more than usually getsused underneath as electricity. Soefficient solar electric conversioncould completely blow away coal,nuclear, and even most hydro.

Marks has developed two dif-ferent solar -to -electric systems thatseem to have rather high theoreticalefficiencies.

Radio waves are electromag-netic. Solar energy is electromag-netic. The main difference betweenorange light (at 600 nanometers)and television channel two (6meters) is a 10,000:1 size factor.Those light wavelengths may seemtiny, but we are starting to routinelyhandle submicron distances in inte-grated -circuit manufacturing.

There's this thing called a crystalset that you might have heard of.Just shove some electromagneticenergy into an antenna, rectify itsomehow, and out comes DCpower. These days, we call thesame thing a rectenna. So why notuse light waves instead of radiowaves?

An antenna is any subsystem forconverting radiated electromag-netic energy into conducted wireelectromagnetic energy. Or vice ver-sa. As a transmitter, if your antennais now properly matched to the restof your circuit, nearly all of your inputenergy will get radiated. And, sincemost antennas are linear and re-ciprocal devices, if you input anyelectromagnetic energy well insideof the antenna's effective area, near-ly all of it will get converted intoconducted electricity. So, a properlymatched antenna can be 100 per-cent efficient. And a rectifier nearlySO.

Now, an optical antenna is trivial.Just make it any old color so long asit is black. Even a black felt tip penwill do. The trick lies in rectifying andgathering all the received solar elec-tromagnetic electricity, rather thanburning it up as heat.

The Lepcon panel is the older ofMarks' two new developments. In aLepcon panel, tiny rectenna ele-ments are created on glass usingmore or less conventional but veryadvanced microlithography. Theseare basically a conductive channelending with a metal barrier diode.The photons in the incoming solar

LUMELOID & LEPCON

Key Paten:s:#4,445,350-Device for Con-

version of Light Power into ElectricPower.

#4,574,-61-An ordered DpolarLight -Electric Power ConvertEr.

Key Paper:Lumeloid Solar Plastic Film and

Lepcon Submicron Dipolar Anten-nae on G ass. 1990 InternationalNew Energy Technology Sym-posium. pages 201-210. From Plan-etary Association for Clean Energybelow.

Key Info Packet:From Advanced Researcn De-

velopmen: below.

Key Players:

Advanced ResearchDevelopment359R Ma n StreetAthol, MA 01331(508) 249-4696CIRCLE 319 ON FREE INFORMATION CARD

SOLAR RESOURCES

Dialog3460 Hi Iview AvenuePalo Alto, CA 94304(415) 8E8-2700CIRCLE 320 ON FREE INFORMATION CARD

Electric Power Research Inst.PO Box 10412Palo Alto, CA 94303(415) 855-2000CIRCLE121 ON FREE INFORMATION CARD

Home PowerFO Box 130Hombrook, CA 96044(916) 475-3179CIRCLE 322 ON FREE INFORMATION CARD

Planetary Assoc Clean Energy191 Promenade du portage, #600Hull PQ, CANADA J8X 2K6(819) 777-9696CIRCLE 323 ON FREE INFORMATION CARD

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energy are used to accelerate elec-trons, which jump the barrier diodeto become a DC current. Unlike atraditional solar cell, there are no

whole lumps only" quantumeffects involved, and nearly all of theavailable energy gets converted.

The antenna/rectifier combina-tion only works with one polariza-tion of light. It converts the onepolarization with up to a theoretical80 percent efficiency, and passesthe remainder on through. You couldput a second Lumeloid panel under-neath that is oriented 90 degreesfrom the first to convert the otherpolarization.

Or, you could use a sneaky trickconsisting of a quarter wave plateand a mirror to rotate your rejectedpolarization by 90 degrees andshove it back up through the originalfilm. Your combined efficiency endsup around a theoretical 72 percent.

The projected costs of the Lep-con process is around $250 perpanel, and the panels should last 25years.

The Lumeloid film process useschemicals instead of very expensivemicrolithography. The chemicaltechniques in theory lend them-selves to low-cost and high -volumeproduction. The chemicals attemptto mimic the first half of the longphotosynthesis process. A ratherlong chain carbon molecule, such aspolyacetylene, is attached to someelectron donor acceptor complex,such as porphyrin and quinone.

The long chain molecule acts as aconductive antenna, changing theinput optical energy into electronenergy. The tunneling gap effect be-tween the large donor and small ac-ceptor rings acts as a rectifyingdiode for DC conversion.

For all this to work, the moleculeshave to be carefully oriented whilethe sheet is being created. Mark'swork has centered on suitable bulkprocesses to do the orientation in alow-cost and high -volume process.Projected costs are five dollars permeter and three cents per watt.

At present, the Lumeloid films areonly expected to last a year instrong sunlight. Once again, Lep-con panels use conventional micro -lithography on glass, whileLumeloid use oriented films that

84 mimic photosynthesis.

Interestingly, the Lumeloid pro-cess is totally reversible. You caninput electricity and get light out aswell. Which could lead to new light-ing and display technologies.

For any of this to become real, wewill need working prototype panels,credible third party research, andthe proper peer review. My "usualsuspects" of Science, Nature,Science News, and the technologypage of the Wall Street Journal havebeen suspiciously silent to date.

My own feelings are that shortand open circuits in production pan-els are going to lead to the verysame type of yield problems thathave held back and restricted de-velopment of large area flat -panelTV displays.

Because of the lack of even labprototypes, their efficiency and costprojections at this time would ap-pear totally meaningless.

Caller ID updateTime sure does fly when you are

having fun. As a result, I've gottenhopelessly far behind on a bunch ofpotentially great projects here. Somy caller -ID project may take awhile.

Caller ID should be available inmost parts of the country very soon.The controversy is dying down,since the benefits so totally and lu-dicrously outweigh any potentialproblems. To see what dozens ofothers are now thinking about callerID, you might want to check #2239CALLERID.CAP on the GEnie RA-DIO RoundTable.

If for no other use, the con-venience of having a no -charge, no -

hassle list of everyone that calledyou while you were out is just flat outwonderful.

Motorola has just announced abrand new MC145447 caller IDchip. Free sample kits are available.This one is supposed to include in-ternal ring detection. But, as near asI can tell so far, the chip of choiceremains the Sierra SC11211.

An FCC Part 68 interface isshown in Fig. 4. Which is what nor-mally has to go between you and thephone company. Key points includean exceptionally well-balancedtransformer with a 1500 -volt isola-tion capability. While such an inter-face is fairly cheap and simple,

getting the needed approval is not.Several companies now offer

some ready -to -go Part 68 inter-faces. These are priced well abovewhat you could build your own for.But they come pre -approved, elim-inating most legal hassles. DallasSemiconductor and Cermetek aretwo typical sources. An interfacebetween the new CermetekCH1845 and the Sierra SC11211caller ID chip is shown in Fig. 5.

Both Cermetek and Sierra havefree caller -ID ap notes available.

As we've seen before, a numberof ready -to -use caller -ID productsare available from Hello Direct.

New tech litFrom Sony, a new Laser Diode

Guidebook. And from Hughes, afree brochure on their NonvolatileSerial Programmable Devices.

The Best of Analog Dialogue is athree decade compilation of thevery best in analog linear integratedcircuit design info. From the compa-ny Analog Devices.

In a startling development, realthermography is now available fortoner -based desktop publishing.One new source is BennetLaserBrite. You spray on chemical Ato soften your toner, dust onpowder B, and then apply heat fromdesklamp C. Presto. Instant raisedletters. Even Braille.

Free stuff this month: A video ona high -end printed circuit prototyp-ing system from Direct Imaging. Afree video on the Toaster, the low-cost broadcast -quality video pro-duction system from NewTek. And agreat new sample A-42 plastic elec-tronic case from. Serpac.

A reminder that l- do have a fullcollection of reprints available.These include Hardware Hacker II &///, my Ask the Guru I & ll & Ill, theBlatant Opportunist I, LaserWriterSecrets, and our brand new Book -on -Demand Resource Kit. Just giveme a call on our no -charge techhelpline (per the box) for more de-tails. Or call me at my Synergetics.

You can also reach me via GEniePSRT (800) 638-9636. Besides thatwavelet freeware and the SmithChart package, you'll find lots ofHardware Hacker and Midnight En-gineering hard -to -find resourcestuff. R -E

AUDIO UPDAT

More from the mail bag

Last month, I answered severalhi-fi questions from readers,but ran out of room before

getting to them all. This month, we'llget to the bottom of the mail bag.

Overpriced signals?I'm appalled by the proliferation of

signal processors-particularlyequalizers-in the audio marketplace. What ever happened to thenotion that a hi-fi system should bea ''straight wire with gain"?A.T.McAlester, OK

The idea is alive and well, but be-set by philosophical confusions.While the concept has validity for,say, power amplifiers, it really can'tbe applied to the entire recordingreproduction chain. Straight -wire -with -gain audiophiles-for whomtone controls of any kind are anath-ema-appear to assume that what-ever signal comes out of theircarefully chosen disc player or tapemachine somehow perfectly em-bodies an original performance.Anyone naive enough to harborsuch a belief has, at best, a veryunclear notion as to how sound isrecorded and reproduced.

Assuming that you had a perfectstereo recording of the sound field(at a specific location) of a live musi-cal event-and all the elec-tromechanical and electronic ele-ments in your playback systemwere perfect-your speakers wouldstill have the task of replicating theacoustics of a concert hall within thecomparatively cramped space of aconventional listening room. Inshort, the chances of exactly du-plicating an original live sound fieldin your listening room are aboutzero.

Given the aberrations in frequen-cy balance, noise level, and dynamicrange likely to be introduced, plusthe loss of rear ambience and reflec-

tions, I see nothing wrong with usingsignal processors to help minimize,ameliorate, or eliminate the variousill effects. I've long since given upany hope of reproducing the precisesound of any original musical perfor-mance in my home. But when I

achieve plausible reproduction, thenI'm satisfied that I've achieved high,if not absolute, fidelity.

System imbalanceAfter a long struggle to find the

reason for my having to operate thebalance control on my preamplifierat the 3 -o'clock position, I tracedthe difficulty to my speakers. Whatwould account for the fact that areadjustment of the midrange con-

my speakers curedthe problem?

Freeport, 7XThe frequencies that contribute

to the perception of "loudness" aremostly in the midrange. (You canconfirm this for yourself by notingthe small effect on the overall loud-ness of music produced by the out-ermost controls of a ten -bandequalizer.) Hence, any control thatboosts or cuts the mid -frequenciesin a speaker system will also neces-sarily influence its relative "efficien-cy" or loudness.

Alcoholic anxietySome tape -cleaner ads seem to

say that alcohol may be injurious tothe insides of recorders. But maga-zines seem to recommend alcoholas a cleanser. Which information iscorrect?N.W.Covington, LA

You should avoid solutions soldas "rubbing alcohols" because theyare likely to include a skin lubricant(usually glycerin) that could betransferred to the tape and thepinch roller. Ask your pharmacy for

LARRY KLEIN

isopropyl alcohol in "NF" purity;that will work fine for heads, pinchrollers, and for general internalcleaning of your machine.

Costly repairsMy receiver recently went dead in

one channel, and I brought it to alocal authorized service center.They charged me $75 to repair aunit that cost $300 when new. Myfriends have had similar experi-ences. Are the repair -shop ownerstrying to get rich at our expense-and why don't the manufacturers dosomething about it?K.U.Boston, MA

We live in a time when very com-plex electronic devices are man-ufactured by automated machinerycontrolled by computers. That is thereason why you can buy a digitalwatch or a pocket AM/FM radio forwell under $10. But the eliminationor reduction of the expensive hand -labor element in many of today'selectronic devices is of no helpwhen the device needs repair. Therepanr process continues to be laborintensive, and it involves skilled, ex-pensive labor at that. In short, al-though electronic products are builtby the most sophisticated auto-mated techniques available to the20th century, they are repaired oneat a time by the equivalent of an18th -century handicraft approach.As you have found, that's not cheap!

Slam damageI've noticed that when I close the

trunk lid the cones of the woofersinstalled in my car's rear deck seemto jump forward. Can the woofersbe damaged by my slamming thetrunk shut?E.G.Chicago, IL

Possibly, but not probably. Thevariables in the situation are the rug - 85

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gedness of the woofer -cone sus-pensions, the size and air leakage ofthe trunk, and the velocity of theslam. To determine whether there isa potential problem, watch thewoofer cone (with its protectivegrille removed, if possible) during a

typical slam. If the forced outwardexcursion exceeds a quarter inch orso, it might be best to close yourtrunk a bit more gently in the future.However, I expect that the bettermanufacturers of the larger car ster-eo speakers, who knew where theywould be mounted, have designedtheir cone suspensions to with-stand large pneumatic shocks.

FM bandwidthWhat is the purpose of a narrow/

broad bandwidth switch on an FMtuner?R.A.Bay Shore, NY

As far as I know, the only justifica-tion for a narrow -band switch is therare case when a listener is locatedbetween two transmitters of com-parable strength that are adjacent toeach other on the FM dial. In anycase, a rotatable directional antennawill probably be of more help in sep-arating the two stations than thetuner's ability to narrow its IF band-width. The narrow bandwidth set-ting may be helpful if the conflictingstations are in approximately thesame direction, or possibly whenthere are severe noise conditions.

Off -frequency FMMany of the rock stations in my

area advertise themselves as beinglocated at, for example, "100 on theFM dial." But my digital tuner won'ttune to even numbers; It sets itselffor 99.9 or 100.1. Does somethingneed adjustment?R.P.

San Diego, CAYes-the thinking of those who

like to reduce all communication tothe short, punchy, and simple-mind-ed. In the U.S., all broadcast sta-tions are assigned odd -numberedoperating frequencies, 2 -mega-hertz apart. Even if you could tune to100 MHz, you wouldn't find anythingthere but a lot of noise and distor-tion. But, come to think of it, thatmay be pretty close to what somestations are really broadcasting!


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continued on page 102 87

DRAWING BOARD

Our long -lost discussion on digital scopes.

ell, it's been a while com-ing but, at long last, we'refinally back to talking

about digital scopes. There havebeen some interruptions in themeantime but that's the way life is-it sometimes interferes with living.This subject got put on hold for a bitbecause of the business of voltageregulators. Sorry about that but,even if you don't have any particularinterest in cars or motorcycles, allthat information should be put awayfor future reference. You neverknow.

Just to refresh all our memories,we had been talking about thethings to be considered in designinga circuit that would serve as thebeginnings of a digital scope. Allscopes, even the one we're going todesign, have certain basic things incommon and any project you have inmind that involves scope design hasto start out life around these funda-mentals. Your ultimate goal may beto construct something that's big-ger, faster, or (to use my favoritephrase), "feature rich," but no mat-ter what you have in mind, whenyou're just getting started it makessense to approach things from thebeginning.

The design criteria for the scopewe are going to be putting togetherare the following:1. The scope will have a maximumbandwidth of at least 1 MHz.2. There will be eight selectablesweep speeds.3. There will be eight selectable gainlevels.4. There will also be a variable gaincontrol.5. The display will be in a twenty -by -twenty matrix.

The block diagram of the scopewe're talking about is shown in Fig.1. While you're looking at it keep inmind that, even though we're only

88 talking about a demonstration cir-

cuit, the basic structure is the samefor every scope there is. Once yougo through the design of a simplescope, it'll be much easier to under-stand the workings of more com-plex ones.

There are all sorts of interestingthings that can be done with thescope we're building and there's noreason whatsoever why you can'ttake the basic circuit and add any-thing you want to it. But we're get-ting ahead of ourselves.

One of the major players in theaccuracy of a digital scope is thetimebase. Ordinarily, in a simplescope such as ours, the timebase isan RC -type circuit that gives you...well, RC -type accuracy. But just be-cause we're not building the world'smost complex scope, there's noreason why we have to settle for so-so accuracy. Whenever you wantaccurate timekeeping, the answeris a crystal -based circuit, and that'swhat we'll use here.

ROBERT GROSSBLATT

There's no shortage of circuitswhen it comes to building a crystaloscillator, and the schematic shownin Fig. 2 is as good as any. If youneed frequencies up in the manymegahertz or even the gigahertzrange, you'd have to devote a lot oftime to this part of the scope, butsince we're keeping everything tounder one measly megahertz, thisschematic is a simple answer to theproblem.

I've picked one megahertz for thebasic crystal frequency because it'sa nice even number to work with and1 -MHz crystals are readily available.You shouldn't have any trouble get-ting the 4049's to work at 1 MHz-even if you're only operating the cir-cuit at 5 volts. If you have any prob-lems, up the voltage to 9 volts or so(working with CMOS stuff isgreat!), and that should take care ofthe problem.

Should you want or need to staydown at 5 volts and you find that the

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oscillator isn't self-starting at thatvoltage, use an equivalent high-speed CMOS part like the74HCT4049. Most of the mail-order houses carry the 74HCT fam-ily and you'll find that they're all fast-er than the 4000 series and just asreliable. Just about the only restric-tion you'll have is that 74HCT partshave the same voltage restrictionsas TTL. They want a supply voltageof 5 volts and going any higher thanthat is a sure way to cook the chip.

Once we have the timebase cir-cuit working properly, the next stepis to do some straightforward fre-quency division to generate all thesweep speeds we need. First, how-ever, we should decide what thosesweep speeds are going to be and,even before that, we have to workout how the horizontal part of thedisplay is going to be conceptuallyorganized.

Our display is going to be, as wespecified, a twenty -by -twenty LEDmatrix. There are twenty columns ofLED's and each column is going tobe enabled in turn for a particularlength of time. When we refer to thesweep speed, we have to dis-tinguish whether we're talkingabout how long it takes to sweepacross the entire twenty 'columns orhow long each of the twenty col-umns is enabled.

If you look at the sweep -speedsettings on a standard os-cilloscope, you'll see that it'smarked in seconds/division. Sinceour display is made up of separate

FIG. 2-A CRYSTAL OSCILLATOR forour scope. For frequencies below 1 MHz,this schematic is a simple solution.

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FIG. 3-THE 4520 DUAL SYNCHRONOUS BINARY COUNTER will provide us with aseries of frequencies that are accurate enough fo. the kind of circuit we're designing.

columns, we can translate that intoseconds per column. Therefore,we'll arrange our sweep speedsaround the time each column is en-abled, and not how long it takes tocycle through all the columns. Thatis important to keep in mind be-cause we want to be able to get arough idea of frequency when we'reviewing a waveform on the scope,and the standard way of doing thatis to count the number of divisionscovered by a complete cycle. Sinceeach division relates to a particularamount of time, you can estimatethe period and calculate the fre-quency of whatever waveform isbeing displayed.

Standard oscilloscopes use a5-2-1 counting sequence for divid-ing the sweep frequency. Thatmeans, at a basic level, that it takesthe trace five, two, or one second(or some fraction of a second) tocover each division. The maximumsweep speed we can reasonably ex-pect to have is about 10 microse-conds since there are certainlimitations to LED intensity, con-struction methods, and so on. It's

possible to do a lot better, but thestuff you have to worry about hasnothing to do with the basic designof the scope itself.

The lowest sweep speed thatmakes sense for the scope we'reworking on is about a tenth of asecond per column. The major fac-tor here is that when you get muchslower than this, it gets increasinglyhard to visualize the waveform onLED's. Remember that the scopewill be enabling one column at atime and only one LED in each col-umn will be lit. If the sweep speed istoo slow, the eye won't be fooledinto seeing several of the columns litat the same time.

Once we get the circuit working,you can experiment with the rangeof sweep speeds and see what theoutside limits are. The top limit is afunction of electronics but the bot-tom is determined by consideringthe- persistence of the retina andother biological factors. If you wantto drop the sweep speed to onesecond per division because youhave a particular need to do that it'srelatively simple to set the elec- 89

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tronics to do it. The best way to getan idea of what it would be like is tosit in front of a real scope and playwith the sweep -speed control.

Now that we know the sweep-

speed range-from a low of a tenthof a second (10 Hz) to a top of 10microseconds (100 kHz) per divi-sion-we can decide what the re-maining six sweep speeds shouldbe. Generating divisions in the stan-dard 1-2-5 sequence is certainlypossible but it's also a pain in theneck to do.

We can cut this part of the designway down and reduce the neededparts to a bare minimum if we let therelationship between the sweepspeeds follow the standard 1-2-4-8binary sequence. By doing that, wecan choose from a wide variety ofstandard binary counters and, asyou can see in Fig. 3, that's exactlywhat I've done. The 4520 is a dualsynchronous binary counter and willprovide us with a series of frequen-cies that, while not exactly whole

numbers, are close enough for thekind of circuit we're designing.

Remember that the resolution ofthe scope we're building isn't all thatgreat in the first place.

Feeding a standard CMOS partlike the 4520 with a clock as high as1 -MHz is an iffy business-es-pecially, as we discussed a whileago, if you're running off a supplythat's down in the range of only fivevolts or so. If you have such a prob-lem, the ways to get around it arethe same as the ones we talkedabout earlier; you can either raisethe supply voltage or use74HCT4520's instead of the stan-dard 4520.

The two 4520's in the circuit giveyou a choice of sixteen clock fre-quencies (seventeen if you countthe basic crystal frequency), so youhave lots of sweep -speed choices.When we get together next time,we'll finish the horizontal circuit andgo through the design of the verticalamps and driver circuit as well. R -E

EQUIPMENT REPORT


the manual says to install C40, a 22pF, 16 -volt electrolytic, but the actu-al part, as shown in the parts list, is22 µF. Also, a spring must be in-stalled to the left of the 7106 IC toground a metallic shield in the backof the meter housing; the instruc-tion manual does not clearly showwhere the spring goes.

Other problems included R43,one of four 1-megohm resistors tobe installed, but the parts list showsonly three 1-megohm resistors andR43 as 100K-also, the 100K re-sistor was missing from our kit. Re-sistor R7 is said to be installed as900K but the parts list shows it tobe 898 ohms and that's what wasincluded in our kit. Likewise with R8;it's installed as 100K but listed andincluded as 100 ohms. Another 100 -

ohm resistor, RX, was not amongthe parts included in our kit, but theydid include an unnecessary 75K re-sistor-perhaps it was intended tobe close enough in value to R43.Resistors R09 and R17 are to beinstalled as 9 ohms each but listed

as 8.98 ohms. Neither of the tworemaining resistors were color -co-ded for 8.98 ohms, but they mea-sured about 12 ohms. Closeenough we decided, and the meterseems to work just fine.

You never know exactly what's in-side something until you take itapart, so you can't help but be famil-iar with the basic insides of any mul-timeter once you build the 100K.The finished 100K is a sturdy, capa-ble meter, and certainly worth itsprice. And although we feel that it'sa pretty decent meter and a greatproject for someone new to elec-tronics, the help of someone moreexperienced might be necessary.However, we've already pointed outthe kit's sore spots so if you plan onbuilding one you should save thisreview as a guide.

If you've read this review andwould like to own a 100K but don'twant to build it yourself, the 100K isavailable preassembled. And the as-sembled 100K multimeter actuallycosts ten dollars less than the kit($19.95). That's because it costsmore to package the unit in pieces,and the kit includes a 47 -page as-sembly manual. R -E


Pen -Based Computing

JEFF HOLTZMAN

pen -based computing is oneof this year's hot topics. Atfirst glance, this new class of

device seems to be more gadgetthan computer. On closer examina-tion, however, it looks more like aglimpse of the future.

As with many hot topics in today'scomputer world, pen -based com-puting got its start at Xerox PARC(Palo Alto Research Center), a re-search division of the corporationmostly famous for photocopying,but whose basic research has fu-eled much of the personal computerrevolution-but that's another story.

In 1968, a fellow by the name ofAlan Kay, now a researcher at Ap-ple, put together a cardboard modelof something he called the Dyna-book. Kay didn't call it a computer;he intended to suggest somethingfar larger, more grandiose, moreconnected, and more accessiblethan any mere data-processing ma-chine. The original design called fora notebook with a megapixelscreen, multiple CPU's, and wiredand wireless networking. Sincethen Kay realized that the hardwarealone was not enough; a user-friend-ly (Macintosh -like) user interfacewould also be required. Even moreimportant, a cooperating system ofsoftware "agents" would assist theuser in gathering information andperforming routine tasks. Agentsare not yet ready for prime -time.User interfaces have evolved con-siderably since 1968, but still have along way to go. Perhaps not sur-prisingly, as in most areas of thecomputer business, the greateststrides have been made in hard-ware.

Since portable computers, laptopcomputers, and notebook comput-ers first started to appear, severalcompanies have released subop-timal designs bearing the title Dyna-book; however, it is only the very

latest generation of pen -based ma-chines that even dignify the con-cept. NCR released the first of thisnew breed in the spring of 1991; fallCOMDEX in Las Vegas saw the re-lease of a spate of new machines byother vendors. This first generationof commercial machines illustratesseveral points: (1) The Dynabookconcept is valid, but (2) currenthardware and software have notfully achieved the vision; even so (3)there is a light at the end of thetunnel.

Hardware and softwareThe typical pen -based machine is

about the same size as a notebookPC (8.5" x 11" x 2", less than fivepounds). The current generationtypically has a 286 or 386SX pro-cessor, a few megabytes of memo-ry, a floppy drive, possibly a harddrive, and a slot or two for specialcredit-card sized memory cards(these cards have now been stan-dardized; more in a future install-ment). Usually there's no keyboard,

although there are "convertible"units that allow both keyboard andpen nput. Some units, such asGrid's GridPad RF (shown in Fig. 1),allow wireless connection to stan-dard networks. Overall, the mostinteresting thing about pen -basedmachines is that the screen is usedfor both input and output. Using aspecial stylus, you draw, write, andedit directly on the display sur-face-it's like an intelligent Etch -A -Sketch, one that allows you to storeand recall text and graphics. It'swhat some call a direct -manipula-tion environment (DME).

If there's no keyboard, how doyou use the thing? There are threebasic approaches. The first simplyglues a pen -input interface on famil-iar operating environments (DOS orWindowS). The second creates arich new environment (GO's Pen -Point operating system). The thirdcreates a limited new environment,one that restrains cost and power inservice of specialized applications.

Microsoft, as might be expected,

FIG. 1-THIS PEN -BASED PC from GRiD features wireless RF connectivity to Novellnetworks. 91

92

has adopted the first course. Thecompany has defined a set of pen -oriented extensions to the Win-dows environment, called Windowsfor Pen Computing (WPC). This en-vironment is scheduled to be re-leased in the first quarter of 1992,right after Windows 3.1. WPC hasalready garnered support fromsome three dozen hardware ven-dors, including AST, Dell, Grid/Tan-dy, NCR, Zenith, Sharp, Sony,Toshiba, Tusk, Momenta, NEC,Samsung, Sanyo, and many more.Currently Grid owns more than 50%of the market, but in five years that'sexpected to drop to about 10% ofthe current level, with Sony,Toshiba, and Sharp accounting forabout 36%, and IBM and Apple to-gether for about 30%. Hundreds ofsoftware developers have alsoshown support for WPC.

A company called GO Corpora-tion has pursued the second optionwith a product called PenPoint, thechief competitor to WPC. PenPointhas not achieved as much supportas WPC (yet), but the support it hasachieved is quite meaningful. IBM,for instance, has licensed PenPoint,and has shown it running on a to -be -

released pen machine. Apple isevaluating use of PenPoint versusits own internally developed pen -

based operating system for a soon -

to -be -released pen machine.Although extending an already

popular environment has some ad-vantages, some feel that a wholenew way of looking at things is re-quired. This new paradigm returnsto square one in the process ofthinking about how people can bestinteract with a computer. For exam-ple, the select -do paradigm (e.g.,select text, press Delete) of Win-dows may not make sense in a di-rect -manipulation environment. In aDME you might simply draw a linethrough unwanted text. It's more di-rect, more natural, more efficient,more comprehensible by computernovices. This is the tack taken byPen Point.

A related area is compound docu-ments, documents that include text,graphics, possibly other media.Windows is just about to the pointwhere building compound docu-ments is reliable and efficient. Bycontrast, PenPoint has been built

Gesture Meaning

Places the insertion point or selects where you tap the pen.- Selects all characters under the line.

Extends the selection to the location where you draw the gesture.

o Deletes the current selection or the character to the right of the insertionpoint.

...-. Deletes words or objects underneath the gesture.

..Backspacesand deletes the character to the left of the insertion point.

(Optional)

,_17.- Inserts space at the insertion point. (Optional; can also be positional)

-J.J Inserts a new line (Return) at tne insertion point. (Optional; can also bepositional)

r-- inserts a Tab at the insertion point. (Optional, can also be positional)

1,7 Places the checked word or selection in the Edit Text dialog box.

y Cuts the selection and places it on the Clipboard.

c< Copies the selection and places it on the Clipboard.

Pastes the contents of the Clipboard at the insertion point. (Optional, can alsobe positional)

t( Reverses the previous action.

Gesture Meaning

Tap ` Select/Invoke

Press -hold ri Initiate drag (move, wipe -through)

Tap -hold 0 Initiate drag (copy)

Flick (four directions) I Scroll/Browse

Cross out X Delete

Scratch out Delete

Circle 0 Edit

Check C, Options

Caret A Insert

Brackets [ ] Select object, adjust selection

Pigtail (vertical) 7 Delete character

Down -right L Insert space

b

FIG. 2-PEN-BASED GESTURES differ between Microsoft's Windows for Pen Com-puting (a) arid GO Corp.'s PenPoint (b).

from the ground up to support Em-bedded Document Architecture(EDA). With EDA, you just grabsomething and start working on it. Ifit's text, a text -editing window popsup; if it's graphics, sizing/shapinghandles appear. This focus on thedocument, rather than the applica-tions used to produce it, is what willmake pen PC's attractive tonovices, and to the those of us tiredof fighting the battle for integration.

Deferred I/O is another interest-ing capability of PenPoint. It allowsyou to "send" documents to otherpeople, regardless whether you'replugged into the company networkor riding a camel in Riyadh. If thehardware can't physically send thefile when you make your request, itadds it to a queue and sends it whenthe required resources becomeavailable. Likewise with modem out-put, fax output, and printer output.

GesturesBoth PenPoint and WPC make

use of gestures, pen motions thatsignal an intent to do something,and depending on the operation,the data to which it is done (e.g.,striking a line of text). Gesturescome in several sizes and shapes,depending on the system; and spe-cific gestures tend to be inconsis-tent from system to system, asshown in Fig. 2-a (WPC) and Fig. 2-b (PenPoint). (This is equivalent tothe once -heated argument aboutwhether the Delete key should workon characters to the right or left ofthe cursor. The vast majority ofusers simply didn't care, as long asusage was consistent from programto program.)

PenPoint demonstrations are ex-tremely compelling. But Microsoftis Microsoft, and Windows is Win-dows. Does PenPoint have achance? It's simply too soon to tell.The Windows juggernaut is rapidlycrushing everything in its path; GOis working hard on data portability,so there's a good chance it will atleast survive. In any case, mosthardware vendors are playing it safeand supporting both operating sys-tems. Phoenix has even released adual -mode BIOS that prOvides low-level support for both.

Theoretically, anything that runsunder Windows should run underWPC. PenPoint is in a more pre-carious position regarding applica-tions; however, WordPerfect andLotus are converting and develop-ing applications, and several othercompanies are developing new ap-plications, including telecom-munication, word processor,spreadsheet, network interface,outliner, PIM, and more.

Some developers are targetingapplications for both environments.Slate is one interesting example.The company has introduced aproduct called PenBook that allowsyou to take any file in PostScriptformat and convert it for use in a penenvironment. The software allowsyou to build a table of contents andlink specific pages to it. It also in-dexes the text. Rather than 45pounds of manuals, imagine beingable to take a notebook with all rele-vant service information on a housecall, and instantly locate the desired

information with a few taps andflicks of the pen. There's potentialhere.

Who cares?Companies marketing pen prod-

ucts see two initial focii: highlymobile personnel (e.g., doctors andnurses, delivery people, sales peo-ple, insurance sales people and ad-justors, etc..) and professionals whotravel a lot.

Mobile usage is already happen-ing. For example, a major pharma-ceutical company recently pur-chased 1000 pen units from Grid foron -site sales; the San Jose PoliceDepartment is evaluating use ofGrid machines to reduce paperwork

Some industry veterans feel thatpen computing is just another over -hyped technology, with little main-stream application. More informedsources, those with a little historicalperspective, see the potential. It willtake a few years, but by the end ofthe decade, most of us will be carry-ing "pentops" and wondering howwe ever got along without them.

News bitsLast time I talked about the sig-

nificant effect that multimedia willbe having on the computer industry,the publishing industry, and societyin general. At the time, I wonderedhow IBM planned to get involved.Shortly after my deadline, Big Blueannounced a wide variety of prod-ucts and services under the banner"Ultimedia." The software (dis-cussed last time) is in some waysthe most interesting part of the an-nouncement; however, there aresome interesting hardware goodiesas well, including a device that letsyou broadcast and receive televi-sions signals across a token -ringnetwork simultaneously with normalnetwork traffic, thereby setting thestage for real-time video-conferenc-ing. IBM also co -released with Intela $2000 NTSC video board, calledthe ActionMedia II, that allows play-back of digitally recorded video. (A$900 add-on allows digital record-ing.) The basic technology is Intel'sDVI (Digital Video Interactive); theboard, though it may sound expen-sive, is about half the cost of theprevious version, occupies half asmuch space, and reportedly pro-

vides about twice the performance.In addition, the company released arather weird multimedia PC (theM57SLC) that includes a high-per-formance CD-ROM drive, XGAgraphics, 16 -bit audio capture/play-back, and a souped -up 386SX pro-cessor that sounds like a 486SXcrammed into a 16 -bit package.

After years of promises, Philipsfinally unleashed its CD -I (Com-pact Disc Interactive) technologyon the consumer market under thename Lrnagination Machine. It costsin the neighborhood of $800, butdoes only one thing. Conversely,you can upgrade your PC with a CD-ROM drive and a slew of useful soft-ware for that amount of money, havechange in your pocket, and have ageneral-purpose tool that's trulyonly limited by your imagination. I

think Philips' marketeers inadver-tently hit on the right name, but forthe wrong reason. The only imagina-tion is in the amount of sales CD -Iwill generate.

On the software front, IBM hasdelayed release of a fully functional(i.e., Windows compatible) versionof OS/2 2.0 until the end of thefirst quarter of 1992. In the mean-time, Microsoft will sell another cou-ple million copies of Windows.However, Microsoft also slipped itsship date for Windows 3.1 until thefirst quarter of 1992, but has pub-licly shown a fairly robust version ofWindows NT (New Technology),betas of which will be shipping todevelopers by the time you readthis. Digital Research released DR -DOS 6.0, the major addition towhich is RAM -based task switchingand some utilities. It seems like agood product, and three or fouryears ago would have been a greatcompetitor to DESQview. R -E

Nifty, huh? . . . I builtthis new drive out of a toaster. 93

94

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PLANS AND KITSFASCINATING electronic devices! Dazers!Lasers! FM/AM/phone transmitters! Detectors!Kits/assembled! Catalog $2.00. QUANTUM RE-SEARCH, 16645-113 Avenue, Edmonton, AB.T5M 2X2.

HOBBY/broadcasting/HAM/CB/surveillancetransmitters, amplifiers, cable TV, science, bugs,other great projects! Catalog $1.00. PANAXIS,Box 130-F2, Paradise, CA 95967.

PCB and schematic CAD. $195.00 IBM EGA CGAMultilayer, rubberband, autovia, NC drill, laser, dotmatrix, plotter, library, Gerber, AUTOSCENE,10565 Bluebird St., Minneapolis, MN 55433. (612)757-8584 free demo disk.

DIGITAL recorder. Digitally record any audiosource with special effects. Microprocessor con-trolled device. Detailed plans, $9.75: T. ZURAW,Box 341, Dearborn Hts, MI 48127.

PRINTED circuit art work. Low cost, for free infor-mation write NEGRON ENGINEERING, 159 Gar-field Place, Brooklyn, NY 11215. Fax or call (718)768-4028.

VIDEOCIPHER II/scanner/cable/satellite modi-fications books. Catalog - $3.00. TELECODE,PO Box 6426 -RE, Yuma, AZ 85366-6426.

REMOTE CONTROL KEYCHAINComplete w,mini-trensmItter.

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to build your own auto alarmQuantity discounts available

Check Vlsa or &VC$24.95 Add '$ 3 shipprig

VISITECT Box 14156, Fremont_Ca. 94539(510) 651-1425 Fax (510) 651-8454

NOW build your own Regulated 12VDC to120VAC, 300W to 500W Inverter, a must forcampers or emergencies. Includes completeschematics, parts and manufacturers lists andmore! Send $19.95 to INVERTER SCIENTIFIC,Box 778, Suffern, NY 10901

'REMOVE

LEADVOCALS

From Records & CD's

Build this kit for under $60 whichremoves lead vocals from standardstereo records, CD's, tapes or FMbroadcasts. Easily connects to anyhome component stereo. Performbye with the backgrounds. You canbe the lead singer of your favoriteband. Detailed Flans. $4.95

Weeder Technologies14773 Lindsey Rd.

Mt Crab, Ohio 45154

DESCRAMBLER kits. Complete cable kit $44.95.Complete satellite kit $49.95. Add $5.00 shipping.Free brochure. No New York sales. SUMMIT RE,Box 489, Bronx, NY 10465.

SURVEILLANCE transmitter kits tune from 65to 305 MHz. Mains powered duplex, telephone,room, combination telephone/room. Catalog withPopular Communications, Popular Elec-tronics and Radio -Electronics book reviews of"Electronic Eavesdropping Equipment De-sign," $2.00. SHEFFIELD ELECTRONICS,7223 Stony Island Ave., Chicago, IL 60649-2806.

ROOM surveillance telephone $175.00. Roomand telephone monitor $275.00. Remote tele-phone recorder $479.00. $3.00 catalog. LISTENELECTRONICS, 603 Elgin, Muskogee, OK74401. (918) 683-9589.

SATELLITE TV descrambler. Build your own.Easy to follow instructions, parts list, circuit board,wiring diagram, $9.95. ABG ENTERPRISES,27081A, Halifax, NS, B3H-4M8.

REMOVE VCR copy protection PCB PAL instruc-tions $16.50 w/P&H NORM HOGARTH, 955 NWOgden, Bend, OR 97701.

TOUCH tone decoder displays dialed number.Store and retrieve up to 256 numbers. Input fromphone, scanner, tape. SASE for brochure. WIND-ESIGNS, Box 200091R, Denver, CO 80220-0091.

Ferro FluidPro -Tech ferro fluid is commonlyused on voice coils to substantiallyimprove frequency response,increase transient and continuouspower handling capabilities andreduce second and third orderharmonic distortion. It reduces theQ and lowers the impedance peakat resonance without a significantreduction in SPL. Generalpurpose fluid for tweeters and midranges only.5cc bottle.

#RC -340-4311095

Each

Light Oak Speaker CabinetPremium ported speaker cabi-net made of acoustical gradeparticle board and covered witha light oak vinyl laminate. Pre-cut with an 11-1/4" hole for usewith most 12" woofers. Thebaffle board has no tweeter ormidrange holes for design flex-ibility. The 3/4" thick particleboard ensures low panel reso-nance. Dimensions: 11"x 15-x27". Volume: 2.5 cu ft. Grilland terminal included. Soldindividually.

#RC -262-100 $4900

Each

Parts

$3990(2 -up)

12 Gauge Neon WireThe competition in today'sauto sound contests is sofierce that good soundalone is not enough towin. More and moreinstallers are striving tomake their installationmore pleasing to the eye.Parts Express now stocks12 gauge speaker wire in vibrant neon colors. This wire isthe same high quality, made in the U.S. wire you haveused before, but now it has flashy, neon colored insulatingjackets. Available in neon pink, neon green, and neonorange. Sold by the foot on or 50 ft. spools.

#RC -100-162 (Neon pink)#RC -100-166 (Neon orange)#RC -100-170 (Neon green)

Tuned Port TubesThese attractive, preformed tunedports allow the back pressure ra-diated from the rear of the wooferto reinforce the sound level infront. Made of black plastic.

Part #

#RC -260-320#RC -260-321#RC -260-322#RC -260-323#RC -260-324#RC -260-326#RC -260-327#RC -260-328

490/Ft

PriceLength Diameter (1-9) (10 -up)

2 3/8" 1-3/4" .404" 1-7/8" .605" 2" .651" 2-7/8" .405" 2-7/8" .603" 2.7/8" .52

2-1/2" 3-7/8" .585" 3-7/8" .64

No mixing for quantity pricing.

.37

.55

.59

.37

.55

.48

.53

.59

Famous Maker 3-1/2" Speaker PairDual cone 3-1/2" speakerpair for upgrading stockdash speakers. Graphitefiber composite woofer coneprovides a smooth extendedresponse at all power levels.The high frequency radiator(whizzer) takes over from the woofer at 6,000 Hz andgreatly extends the response past 20 KHz. Strontiumferrite magnet. 3/4" high temperature voice coil.Impedance: 4 ohm. Power handling capability: 25 wattscontinuous, 70 watts peak. Frequency response: 120-21,000 Hz. Equipped with dust screen. Made in the U.S.by a company with over 40 years experience in the autosound market.

#RC -265-275 $1 995Pan

Subwoofer Input/Output TerminalThis recessed terminalpanel has inputs for rightand left channels as wellas outputs for right andleft channels to route toyour satellite speakers.Greatly simplifiessubwoofer hook-up.Outside dimensions:3-7/8" x 5-3/8".

#RC -260-308

$395

(1-9)

EXPreSS340 E. First St., Dayton, Ohio 45402Local: 1-513-222-0173FAX: 513-222-4644

30 day money back guarantee $20.00 minimum order Weaccept Mastercard, Visa, Discover, and C. 0. D. orders. 24 hourshipping Shipping charge - ups chart rate + $1.00 ($3.50minimum charge) Hours 8:30 am - 7:00 pm EST, Monday - Friday 9:00 am - 2:00 pm Saturday. Mail order customers, please call forshipping estimate on orders exceeding 5 lbs. Foreign destinationcustomers please send $5.00 U.S. funds for catalog postage

$350(10 -up)

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GAMBLING: build miniature computer -clock rou-lette wheels, play perfect blackjack -Z-80 based;software available. For detailed plans and infosend $15.00 to G.R. ENTERPRISES, PO box424, Portland, OR 97207.

ZAPPER! electronic fun, simple and inexpensive,battery powered. Plans $2.00 to: PAR, 417 Asso-ciated, Suite A-313, Brea, CA 92621.

PROJECTION TV... Convert your TV to project a7 -foot picture... Easy!... Results comparable to$2,500.00 projectors... Plans and lens $29.95...Professional systems available... Illustrated cata-log free... MACROCOMA, 15GF Main Street,Washington Crossing, PA 18977... Creditcard or-ders 24hrs. 1 (800) 955-3979.

CABLE TVCONVERTERS with 2 year warranties. ScientificAtlanta - Tocom - Jerrold 8580 & 8590's. Testmodules for Star Comm 6 & 7's. All Tocoms andScientific Atlanta. (712) 323-9445.

SATELLITE TVFREE catalog - Lowest prices worldwide. Save40 - 60%. Systems, upgrades, parts, all majorbrands factory fresh and warrantied. SKYVISION,1012 Frontier, Fergus Falls, MN 56537. 1 (800)334-6455.

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SATELLITE TV - Do it yourself - systems. Up-grades. Parts. Major brands discounted 40% -60%. We'll beat everyone's price. L.J.H. INC., callLarry (609) 596-0656.

CABLE TV Secrets - the outlaw publication thecable companies tried to ban. HBO, Movie Chan-nel, Showtime, descramblers, converters, etc.Suppliers list included. $9.95. CABLE FACTS,Box 711-R, Pataskala, OH 43062.

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LCS.S.,47;!(ja. 11,,ta

IN, CA 1 -800 -521 -MARK (orders only)OUTSIDE CA 1-80-423-FVE (o only)MARK V ELECTRONICS. INC ORDER BY FAX (213) 888-I6868

rders

Competitive Pricing * Fast Shipping Since 1985 CATALOG & INFORMATION (213) 888-8988

indicates the level of difficulty in the assembling of our Products Beginner AA intermediate AAA Advanced * Fully AssembledSM-333

SpECIAL 11;i1 !OFFER 1 4-- II 5M302,#

.

e: "/ li. ;, TAT 000A . ,TA-800MK2

TA -802r

' TA,477 TA -1500 . SIVITooSpecial offer will be given to the purchase of Amplifier + Metal Cabinet + Power Transformer! TA,3600. 1 ' SM-720

AMPLIFIERS KIT ASSEMB. MISCELLANEOUS KIT ASSEMI.

MODEL DESCRIPTION

1A-28MK2 Digital Voice Menlo $ 30001 A 50A B Mtn Purpose Melody Generator 12 84 ,7 20TA 50C Multi Purpose Melody I Ham Bidnda, Welling March etc I Generator i 5 65 18 71

TA-120MK2 35W Class A Mari Poorer Mono Amp 31 50 42 80

TA -300 30W MuOr Purpose Single Channel Amp A 27 00 29 00

SM 302 SOW 60W Stereo Power Amptitter (won Mic inpul IAA 73 00 85 00TA 323A 30W X 2 Stereo Pre-mainAmp A 31 50 42 80TA 377A Slate 01 the An Fully Complementary Symmetrical FAT PreAmp 59 95 75 00

TA 400 40W Solid State Mono Amp A 26 00 34 93

TA -477 120W Mostet Power Mono Amp 6800 85 00

SM 720 120W 120W AC/DC Stereo Eli-Fi X. Pre -Main Aron 7ri 00 89 00

TA 800MK2 120W 120W Low Tiro Pre -Main Stereo Power Amp 68 92

MODEL DESCRIPTIONTY-2313 3 Channel Color Light Controller S $ 65 00TY 25 Stereo Loudspeaker Protector A 14 85 20 85TY 35 FM Wireless Microphooe 11 25TY-36 AC DC Quartz Digital Cock A 19 00 26 20TY-38 Sound Touch Control Swocri 12 00TY-41 MK V Infrared Remote Control 1.1m1 rwCasei 22 00 35 00TY 42 Bar. Dot Level Meter 24 15 33 81TY-43 3' 7 Digital Panel Meter 29 00 38 00TO -45 20 Steps Bar Dot Atm. Level Dop.au 38 45 45 14PI -47 Superior Electronic Roulefle 19 46 2: 24016 10 000 ut BOO DC Capacitor ,TA-3600.TA 477 TA 1000A TA 8021 23 00017 8.200 ul 50V DC Capacitor (TA -802 TA-1208AK2r 13 00021 Nobel Resistor -Single Vol Control TA 3600. TA -477 TA -1000A TA-120MK2) 17.00

022 Alps Resistor Dual Vol Control tTA 377A TA -802 TA -27001 22 00

TA -802 BOW 80W Pure DC Stereo Main Power Amp 45 94 59 72 REGULATORSLA -10000 100W Dynamic Class A Main Power Mono Amp A 50 00 65 00

1A 1500 100W B 2 Class A DC Stereo Pre -Mph' Amp 73 70 95 81

TA -2200 DC Fel Super Class A DC Pre -Amp 47 70 58 24TA 78

TR-35581 0-15V 5A Regulated Di3 Power SAL i ly I fie case A former) $15 65 $ 21 767R -355B 0-30V 3A Regulated D; Power Supolv no case 6 F former, A 15 65 21 76TR-503 0-50V 3A Regulated DC Power Supply f rio case A x tormen A 16 75 23 65

-2500 HQ Pre -Amp Fw10 hand graphic 03 DO

1A-2800 BLEET IC Pre -Amp eir3 way tone L 48 90 63 57 METAL CABINETS WITH ALUMINUM PANEL7A-3000 Stereo Simulator (For Mono TV or i'i '7 o Source( A 27 00 38 50

TA -3600 300W HE) SILT Power Mono Anc 8500 110 00

SM-222 7 Band RI -Fl Graphic Feu, iii 26 80 38 80

SM-333 AuclioAddeo Surround Sr. Ir . 65 00 75 00

SM-666 Dynamic Naise Reditchrii. 26 00 34 00

SM-888 Universal AudtoNi -- - - 155 00

MODEL H" x W' x D" MATCHING PRICE

L0-1273 3' 12 7' TA -2800. TA -377A TA 2200 $ 23 85LG-1684 4 16' 8 TA -323A TA -377A TA 2200 28 50L0 -t924 4- 19 Ili., TA -802. TA -1500 TA -1 'OMK 2 TA -800 MK2 TA -10000 34 50LG-1925 5 19 11i TA -477 TA -800 MK2 TA -1500 TA -10000 TA -3600 38 001.0-1983 2', 19 B TA -377A. TA -2800 TA 2200 TA-120MK 2 30 50

- .POWER TRANSFORMERS

DIGITAL METERS AND COUNTER KIT MEMO MODEL DESCRIPTION MATCHING PRICE

SM-43 3 , Muth -Functional Led 7 i '' ici $ 34 50 $ 43 00

SM-48 4' H crecision 0 c M B 00 48 00

SM-413A - 7i ionion 0 c L' r, ABS 61401. ca,- 41 20 52 00

SM-49 ' i unctior i 0 M P (w -Hold 36 00 44 50v hi fl, fin 0,,.

001 28V x 2 68 to 30V 2 6A TA -840 MK2 TA -B02, TA -1000A. TA -1500 S 28.00002 36V, 2 3A LIC-503 LA -323k TA -400 TA -300. TA -377A 23 00003 40V . 2 6A TA 4'7 30.00004 24V x 2 6A TA -120 MK 2 23 00005 26V F 2 3A TR- 355E1 17 00006 18,7 ?5A TR 3755A 1.00

We

ouOf

accept thasst Credit Cards Money Orders Chocks aria CO D Orders C 0.D tee is 50 50 Mal mum order d 820.00 We stud by UPSsuound msde US . thin SS 001 and cog by us 000,1 Business & Showroom hours: (Pacific Time)stele US Pgase caii out sags department lot orders oyef 2 ets ot lotegn orders 511 assernblea omits have a 30 days warran y Quality Or volume OiSCOunt available won request Resdents Mon. thru Fri. 9:30 am to 5:00 pmCA Jesse add sags tas 8.25°. Prepad Cutlet tor taste, Shgthent Puces are susses, to charge yethouf rotor noose We are not respoestble forhgcgtah.a1 tutors Sat. 10:00 am to 5.00 pm

MARK V ELECTRONICS INC. - 8019 E. Slauson Ave, Montebello, CA 90640 1 = NVCIRCLE 93 ON FREE INFORMATION CARD 97


THE MOST ADVANCEDTECHNOLOGY IN CABLE EQUIPMENT:

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Cable TVDescrambler KitsUniversal Kit $55.00Includes all parts and PC Board. Not includedis the ac adaptor or enclosure.

Tri-Mode Kit $39.00Includes all parts. PC Board and AC Adaptor NotIncluded is the enclosure.

SB-3 Kit $29.00Includes all parts. PC Board and AC Adaptor. Notincluded is the enclosure.

Universal Tutorial $9.95Includes an in depth study at the tecnonology usedand has troubleshooting hints.

Tri-Mode Tutorial $9.95Includes a gate by gate study of the circuit and hastroubleshooting hints.

Call Toll Free 1-800-258-1134

COD Only

M & G Electronics, Inc.72 Orange St., Suite 216Providence, RI. 02903


EDUCATION & INSTRUCTIONF.C.C. Commercial General Radiotelephone li-cense. Electronics home study. Fast, inexpen-sive! "Free" details. COMMAND, D-176, Box2824, San Francisco, CA 94126.

BE a recording engineer; Train at home for highpaying - exciting careers. Free information. AU-DIO INSTITUTE, 2258-A Union St., Suite K, SanFrancisco, CA 94123.

COMPLETE course in electronic engineering.Eight volumes. Includes all necessary math andP BOOKShysics. Free brochure. BANNER TECHNICAL

, 1203 Grant Avenue, Rockford, IL 61103.

Be a TV/VCRRepair Specialistow you can train at home in spare time for a money -making

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U.1 Please send me full information and color brochure on how I canlearn TV/VCR Repair at home in my spare time. I understand

.= there is no obligation and no salesman will visit me.

O Name ApeCC

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Lthone ( I

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CABLE TVDESCRAMBLERSALL TYPES 800-582-1114FREE CATALOGM.K. ELECTRONICS 7958 Pines BlvdSuite 276 Pembroke Pines, FL 33024

MAKE a thing... make a living... Study IndustrialDesign Technology and bring your ideas to life.Learn to problem -solve, sketch, render and de-sign. Develop models, create prosthetic appli-ances. Build your future in movie and theaterspecial effects, toy and product, exhibit, transpor-tation, furniture/fixture, architectural and amuse-ment environmental design at The Art Institutesof Pittsburgh, Fort Lauderdale, Seattle or TheColorado Institute of Art. For information write526 Penn Avenue, Dept. 61, Pittsburgh, PA 15222.Or call 1 (800) 525-1000.

BIOMEDICAL letter covers medical electronics,anatomy, equipment function, electrical safety,troubleshooting. PNP PUBLISHING, Box 333,Brooklyn, NY 11204. (718) 837-9349 Extension55.

PAY TV AND SATELLITE DESCRAMBLING

ALL NEW 1992 EDITION ALL NEWit's up to to minute. All new update on cable, wireless and satellite. Turnrons.bypasses, circuits. chipping, bullets. bags, Decree, Liberty One. ECM's. DataReaders. programming, and lots more. Our best yet.OnN $15.95. Other (all dif./erect) editions 1991. 1989. Volume One (Basics) 515.95 each. MOS Handbook5995 Satellite systems under $600 St 2.95.. Any 3629.95 or 6449 95. VideoS29.95. Scrambling News Monthly $24 95/yr Sample $3 All new catalog $1.Shipping costs included.

Scrambling News. 1552 Hertel AveBuffalo, NY, 14216. Voice,Fax (716) 874-2088

COD s ARE OA ADD 56

VCR tapes by college instructor covering elec-tronic topics. Send for free demo $3.50 P&HO.C.S., PO 292, Fort Mill, SC 29715.

NEW book, Getting Started in Nuclear Physics.Easy to follow with illustrative footnotes and ad-vanced practical procedures. $19.95. FARAHFARAH, PO Box 2464, Sarnia, Ontario, N7T 7T1Canada.

FREE CATALOG!1-800-648-7938

JERROLD HAMLIN OAK ETC


Special Dealer Prices/ Compare our Low Retail Prices! Guaranteed Prices & Warranties! Orders Shipped Immediately!

REPUBLIC CABLE PRODUCTS, INC.4080 Paradise Rd. #15, Dept RE292

Las Vegas, NV 89109For all other information (702) 362-9026

BUSINESS OPPORTUNITIESYOUR own radio station! Licensed/unlicensedAM, FM, TV, cable. Information $1.00. BROAD-CASTING, Box 130-F2, Paradise, CA 95967.

LET the government finance your small business.Grants/loans to $500,000. Free recorded mes-sage: (707) 449-8600. (KS1).

EASY work! Excellent pay! Assemble products athome. Call toll free 1 (800) 467-5566 Ext. 5192.

MAKE SU! Become an American electronicsdealer! Prof it opportunities since 1965. CallSCOTT PRUETT, 1 (800) 872-1373.

HOME assembly work available! Guaranteedeasy money! Free details! HOMEWORK -R, Box520, Danville, NH 03819.

SNOW? Thriving, fully equipped, audio -video re-pair shop. $130K+ thig year! Proven 40% + grosslast three years. $70,000.00 cash. AUDIOTECH,256-B North Highway 101, Encinitas, CA 92024.FAX (619) 944-0345, Phone (619) 944-9048.

MONEYMAKERS! Easy! One man CRT rebuild-ing machinery. $6,900.00 rebuilt. $15,900.00 new.CRT, 1909 Louise, Crystalake, IL 60014. (815)459-0666. Fax (815) 477-7013.

LEGITIMATE $$$ opportunity $$$ weekly com-plete report $19.00. DME, 1317 N. San Fernando#325, Dept. 02W4, Burbank, CA 91504.

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Standard Features Include:-Solid state integrated circuit provides excellent regulationOutput voltage maintained up to 95% of no load valueHigh quality filtering for low noise operation-Heavy duty power transformer for complete line isolation.0n/Off indicator light and rugged on/off switch on faceplate3 conductor grounded cord on 10 Amp and larger modelsCurrent limiting electronic foldback for auto overcurrent protection

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1-800-582-4044 i'LASErtTRIPP LITE - PRECISION REGULATED DC POWER SUPPLIES

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ICS* Continuous RippleOrder # Price (amps) Duty (amps) Fusing Voltage HxWxD (Inches) WeightPR4.5 32.95 4.5 3 Internal 0.1 Volt Max 3.125 x 4.75 x 8.25 5 lbs.PR7 44.95 7 5 Chassis Mount 0.15 Volt Max. 3.75 x 6.5 x 7.5 7 lbs.PR10 64.95 10 7.5 Chassis Mount 0.15 Volt Max. 4.5 x 6.625 x 7.625 10 lbs.PR15 89.95 15 12 Chassis Mount 0.15 Volt Max. 4.75 x 7.5 x 8.25 13 lbs.PR25 126.95 25 20 Chassis Mount 0.15 Volt Max. 5.125 x 12.5 x 10.5 20 lbs.PR40 179.95 40 32 Chassis Mount 0.15 Volt Max 7.25 x 12.5 x 10 26 lbs.PR60 249.95 60 48 Chassis Mount 0.15 Volt Max 8.5 x 12.5 x 10 29 lbs.

*Intermittant Communications Duty (50% Duty Cycle)

SOLDERLESS PROTOTYPING BOARDS WI

SB830

FeaturesColor coordinates for easy recognitiondnsertion wire: 20-29 AWG (0.3 - 0.8 mm)Over 10,000 insertion cyclesAccepts all standard components

SB1660 ,E32390

Order #SB200SB400SB630SB830SB1360SB1660SB2390SB3220

Price1-9

2.994.895.456.49

12.4917.4522.4931.49

Price10+

2.494.394.955.99

11.9916.9521.4930.49

Dimensions (in.)LxWxH

6.5 x 0.37 x 0.43.3 x 2.2 x 0.46.5 x 1.4 x 0.46.5 x 2.2 x 0.48.5 x 3.9 x 1.28.5 x 5.1 x 1.29.1 x 6.9 x 1.29.5 x 8.3 x 1.2

Dist.Strips

2

2

0

2

1

45

7

Dist.Points100 x 2

1000

200100400500700

TerminalStrips

0

1

1

1

223

4

TerminalPoints

0

300630630

1,2601,2601,8902,520

BindingPosts

0

00

0

23

4

4

Z80 CPU Technical ManualThis 338 page manual contains the architecture, pin description, timing, instruction set, instructiondescription, interrupt response and hardware/software implementation examples of the Z80 CPU.

Order # Z29 9.95 Z80 CPU Technical Manual Weight: 1 lb.

Intelligent Peripheral ControllersOver 700 pages of data sheets, application notes and technical information on Zilog's intelligentperipheral controllers. The part numbers contained in this book are Z8400, Z84C00, Z84C01,Z8410/C10, Z8420/C20, Z8430/C30, Z8440/1/2/4, Z84C40/1/2/3/4, Z84C50, Z8470, Z84C90,Z84011/C11, Z84013/15, Z84C13/C15, Z80180, Z80181 and Z280.

Order # Z2480 13.95 Intelligent Peripheral Controllers Weight: 2 lbs.

Datacom ICsOver 700 pages of data sheets and other technical information on Zilog's Data Communications ICs.Part numbers contained in this book are the Z16C30/31/33/35/50, Z5380, Z85230, Z80C30, Z85C30,Z8030, Z8530, Z80181, Z84013, Z84015, Z84C13, Z84C15, Z8440, Z84C40 and Z85C80. Alsoincluded are application notes.

Order # Z2503 13.95 Datacom ICs Weight: 2 lbs.

MicrocontrollersOver 1300 pages of data sheets, application notes and technical information on Zilog's microcontrollers.The part numbers contained in this book are Z8600/01/02/03/04/11/12/13/71/81/82/91,Z8800/01/20/22, Z86C00/C06/C08/C09/C10/C12/C19/C20/C21/C27/C30/C40/C50/061/C62/C89/C90/C91/C93/C94/C96/C97, Z86E08/E19/E21/E30/E40, 288C00, Z86127, Z86128, Z765A, Z5380 andZ53C80.

Order # Z8275 16.95 Microcontrollers Weight: 3 lbs.

*Books are not returnable. We carry the newest versions available.

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CTIVE COMPONENTSMICROS

Order Os Price6242 8.956502 2.956522A 3.756821 1.756845 2.458080A 2.758085A 2.958086 4.458088 4.25

4.155.752.252.252.75

18.95

8237A58250.8251A8253-58255A58275

STATIC RAMSOrder # Price2101 1.652114L25 1.392147-3 3.756116LP3 2.756116-3 2.256264LP10 4.956264LP15 3.956264-10 4.756264-15 3.7562256LP10 6.7562256LP15 6.25628128LP8 34.95628128LP10 32.95

LINEAROrder # PriceMAX232CPE 4.55LM311N .49LM324N .35LM339N .39LM555CN .29LM741CN .29LM1488N .45LM1489N .45

DRAMSOrder # Price Desc.MK4027N2 .75 4x14116-20 .85 16x14416-12 2.95 16x44164-10 1.95 64x11

4164-15 1.55 64x14164-20 1.25 64x141464-12 2.7541256-80 2.75

64x4256x1

41256-12 2.15651258-80 4.95 22556xx11

514256-10 6.95 256x4514258-80 9.95 256x4511000-80 7.25 1Mx1511000-10 6.95 1Mx1511001-80 8.25 1Mx1

EPROMSPe

Order Pricer # Prog.4.75 25V

2716 3.45 25V2732 3.95 25V2732A25 3.45 21V2732B45 4.25 12.5V2764-25 3.75 21V2764A25 3.25 12.5V27C64A15 3.95 12.5V27128A25 3.95 12.5V27256-25 4.75 12.5V27C512-15 6.95 12.5V27C010-15 9.95 12.5V27CO20-15 24.95 12.5V

LINEAROrder # Price DescriptionCA3161E 1.95 Decoder DriverCA3162E 6.25 Converter78L05 .35...5v Pos Reg. TO -927805K 1.25 5V Pos. Reg. TO -37805T .45 5V Pos. Reg. TO -2207812T .45 5V Pos. Reg. TO -22079L05 .29 ..5V Neg. Reg. TO -927905T .49 5V Neg. Reg. TO -220

'EMORY MODULES-SIMMSOrder # Price Organization Speed256x9-80 19.95 262,144x9 8Ons1 x9-80 57.00 1,048,576x9 8Ons4x9-$0 210.00 4,194,304x9 8Ons

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Your Natural Resource for WideTest/Measurement and Prototype Equzpinent

Jameco Solderless Breadboards

Jameco's long-lasting breadboards feature screen -printed color coordinates and are suitable formany kinds of prototyping and circuit design. Larger models feature a heavy-duty aluminumbacking with voltage and grounding posts.

Part Dim. Contact Binding Dim. Contact BindingNo. L" x W" Points Posts Price L" x W" Points Posts Price

PartNo.

JE21 3.25 x 2.125 400 0 $4.95 JE25 6.500 x 4.25 1,660 3 17.95JE23 6.50 x 2.125 830 0 6.95 JE26 6.875 x 5.75 2,390 4 22.95JE24 6.50 x 3.125 1,360 12.95 JE27 7.250 x 7.50 3,220 4 31.95

GoldStar 20MHz Dual Trace Oscilloscope'Hie perfect unit for today'stesting and measurementneeds! Features include a 6"CRT display, and bandwidthfrom DC to 20 MHz. TheGoldStar Oscilloscope comeswith two 40MHz probes, twofuses, power cord, operationmanual, schematics and blockand wiring diagram. It'slightweight and portable witha two-year warranty.

BNC Cable Assembliesfor 057020

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BNC(M) to BNC(M) RG58AJU (39"L) $3.95

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WCC100

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Metex Digital Multimeters Handheld, high accuracy AC/DC voltage, AC/DC current,

resistance, diodes, continuity, transistor hFE (except M3900) Manual ranging w/ overload protection Comes with probes, batteries, case and manual

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M3800 3.5 Digit Multimeter

M3610 3.5 Digit Multimeter

M3900 3.5 Digit Multimeterwith Tach/Dwell $59.95

M3650 3.5 Digit Multimeter w/Frequency& Capacitance $74.95

M4650 4.5 Digit w/Frequency & Capacitance& Data Hold Switch $99.95

$39.95$59.95

M4690

Jameco Logic Pulser Jameco Logic Probe

Compatible with TFL, DTL, RTL, HTL,HNIL, MOS and CMOS ICs IMS1 Sync input impedance Pulsermode output current: I OmA Square wavecurrent output: 5mA Audible tone

LP540 $16.95

A.R.T. EPROMProgrammer

Programs all current EPROMs in the 2716

to 27512 range plus the X2864 EEPROM

RS232 port Software included

EPP $199.95

Max Frequency 80MHz Minimumdetectable pulse: I Ons 120K52 inputimpedance Max. supply voltage: ±25V TTL threshold: (Lo)+0.8V ±0.I V, (Hi)+2.3V ±0.2V CMOS threshold: (Lo) 30%VCC ±10%, (Hi) 70%VCC±10%

MS104 $24.95

UVP EPROM Eraser

Erases all EPROM's Erases 1 chip in15 minutes and 8 chips in 21 min

UV intensity: 6800 UW/CM2

DE4 $89.95

EPROMs - for your programming needsPart No. Price Part No. Price Part No. Price

TMS2516 $4.25 2764-20 $3.95 272560TP $3.75TMS2532A 6.95 2764-25 3.75 27256-15 5.49TMS2564 5.95 2764A-20 3.75 27256-20 4.95TMS2716 5.95 2764A-25 3.19 27256-25 4.491702A 3.95 27C64-15 3.95 27C256-15 5.952708 4.75 27C64-25 3.25 27C256-20 4.952716 3.39 271280TP 2.49 27C256-25 4.252716-1 3.75 27128-20 7.95 275120TP 4.9527C16 4.25 27128-25 7.75 27512-20 6.752732 4.95 27128A-15 4.95 27512-25 5.952732A-20 4.49 27128A-20 4.49 27C512-15 6.752732A-25 3.49 27128A-25 3.75 27C512-20 6.492732A-45 2.95 27C128-15 5.75 27C512-25 5.9527C32 4.75 27C128-25 7.95 27C010-15 9.95

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Partial Listing Over 4000 Electronicand Computer Components in Stock!


Selection & Competitive PricesComputer Upgrade Products and Electronic Components

Upgrade your existing computer system! Jameco will help you upgrade easily and economically.

Jameco 80386SX Motherboard I6MHz processing speed Baby motherboard (8.5"x13") Zero or one wait state operation Supports up to 8MB of RAM Intel 80387SX/compatible math coprocessor socket AMI BIOS Six 16 -bit and two 8 -hit expansion bus slots One-year Warranty

JE3516SN $299.95

Conner IDE Hard DrivesThis series of high-performance Conner disk drives is designed for largestorage capacity.

CP3000 40MB 3.5" Low Profile $249.95CP30084 80MB 3.5"Low Profile $399.95CP30104 120MB 3.5" Low Profile $479.95CP3204 200MB 3.5" HH $699.95ADP20 16 -bit Host Adapter $29.95

Additional host adapters available!

Integrated Circuits'Part No. 1-9 10+

7400 $.29 $.197402 29 .197404 29 .197406 35 .257407 35 .257408 35 .257410 29 .197417 35 .257420 29 .197432 35 .257447 .89 .797474 39 .297476 45 .357486 45 .357489 2.95 2.757490 59 .4974121 49 .3974192 79 .6974193 79 .69

Linear ICsPart No. 1-9 10+

TL082CP $.59 $.49LM317T 65 .55LM324N 35 .29LM336Z 1.05 .95LM339N 39 .35NE555V 29 .25LM556N 49 .39LM723CN 49 .39LM741CN 29 .251.1141458N 35 .29LIv11488N 45 .39LM1489N 45 .39ULN2003A 69 .59LM3914N 1.95 1.75NE5532 1.19 1.097805T 45 .417812T 45 .41

* Call for a complete listing of ICs

Fujitsu 101 -Key Enhanced KeyboardThis keyboard features 12 function keys, separate cursor and numeric keys.

IBM PC/XT/AT and compatible computers Automatically switches between XT or AT LED Indicators for Num Lock, Caps

Lock, and Scroll Lock Tactile Feedback. Manual included Ocie-year Warranty

FKB4700 $79.95

Dynamic RAMsPart No. Description Price

4164-100 100ns, 64K x 1 $1.894164-120 120ns, 64K x 1 1.694164-150 15Ons, 64K x 1 1.4941256-60 6Ons, 256K x 1 2.4941256-80 8Ons, 256K x 1 2.1941256-100 10Ons, 256K x 1 1.9541256-120 12Ons, 256K x 1 1.7941256-150 150ns, 256K x 1 1.69511000P-80 8Ons, 1MB x 1 5.99511000P-10 100ns, 1MB x 1 5.49

MiscellaneousComponents'

PotentiometersValues available (insert ohms into spacemarked "XX"):5000, 1K, 5K, 10K, 20K, 50K, 100K, I MEG

43PXX 3/4 Watt,15 Turn $.9963PXX 1/2 Watt, 1 Turn 89

Transistors And DiodesPN2222 $.12 1N751 $.15PN2907 .12 C106B1 .651N4004 .10 2N4401 .152N2222A .25 1N4148 .071N4735 .25 2N3055 .692N3904 .12 1N270 .25

SwitchesJMT123 SPDT, On -On (Toggle)206-8 SPST, 16 -pin (DIP) 1.09MPC121 SPDT,

On -Off -On (Toggle) 1.19MS102 SPST, Momentary

(Push -Button).. 39*Additional components available

$1.15

a LitLIEnif LL t ERE

Many moreUpgrade Products

available! 356KU $99.95

Toshiba 1.44MB 3.5"Internal Floppy Disk Drive

IBM PC/XT/AT and compatibles Compatible with DOS versions 3.3 or higher Includes all necessary installation hardware I.44MB formatted high density mode 720KB formatted low density mode

Size: I"H x 4"W x 5.9"D (actual drive size) One-year Manufacturer's Warranty

ConnectorsPart No. Description Price

DB25P Male, 25 -pinDB25S Female, 25 -pinDB25H HoodDB25MH Metal Hood

LEDsXC209R T I , (Red)XC556G T1 3/4, (Green)XC556R TI 3/4, (Red)XC556Y T1 3/4, (Yellow)

$.65.75.39

1.35

$.14.16.12.16

IC SocketsLow Profile Wire Wrap(Gold) Level X2

8LP14LP16LP24LP28LP40LP

$.10.11.12.19.22.28

8WW14WW16WW24WW28WW40WW

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Also Available

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Levitating DeviceObjects float on air and move to thetouch. Defies gravity! Amazing gift.conversation piece, magic trick orgreat scientific project.ANT1K Easy-Ass'y Kit/Plans $19.50

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3 MILE

Telephone -Transmitter!Automatically transmits 2 sides ofphone conversation to any FM radio.Tunable, easy -assembly PC board.Operates only when phone is in use.VWPM7 Plans $7.00VWPMK7 Kit'Plans $39.50

TV & FM Joker/JammerPocket size device lets you remotelydisrupt TV or radio reception. Greatgag! Discretion required. Easy -buildelectronic kit. EJK1KM $19.50

100,000 V - 20' RangeIntimidation Device!Electronic module, may be enclosedfor handheld, portable, or fixed uses.ITM2 Plans (creditable to kit) $10.00ITM2K Kit & Plans $49.50

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Laser PenPen sized laser, great for movies,drive- ins, pointer. Ready to use, withbats. LAPN1 Laser Pen . $149.50

Pocket Laser Kit3mw or 5mw kits, with solid state670nm diode. Caution, Class Illa item.VRL3KM 3mw Laser Kit $99.50VRL5KM 5mw Laser Kit .. $119.50

MORE Laser Kits!LAS1KM 1 mw Laser, 632nm, HeNeEasy to Build Kit $69.50

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NEW LITERATURE


tions are described, alongwith some special modula-tion techniques. Radio fre-quencies, propagation, andspace communications arecovered.

Almost half of the bookfocuses on constructionand maintenance of hamequipment, and getting onthe air. It provides practicaladvice about constructiontechniques, test equip-ment, measurements, trou-bleshooting and repair.Instructions are providedfor building your own power

102 supplies; audio and video

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LASER DIODESSTOCK # MFG.

WAVE- OUTPUT OPER. OPER'1-24 25-99 100+LENGTH POWER CURR. VOLT.

LS9220 TOSHIBA 660nm 3 mW 85 mA 2.5 V 129.99 123.49 111.14LS9200 TOSHIBA 670nm 3 mW 85 mA 2.3 V 49.99 47.99 43.19LS9201 TOSHIBA 670nm 5 mW 80 mA 2.4 V 59.99 56.99 51.29LS9211 TOSHIBA 670nm 5 mW 50 mA 2.3 V 69.99 66.49 59.84LS9215 TOSHIBA 670nm 10 mW 45 mA 2.4 V 109.99 104.49 94.04LS3200 NEC 670nm 3 mW 85 mA 2.2 V 59.99 56.99 51.29LS022 SHARP 780nm 5 mW 65 mA 1.75 V 19.99 18.99 17.09SB1053 PHILLIPS 820nm 10 mW 90 mA 2.2 V 10.99 10.44 9.40

WAO II PROGRAMMABLE ROBOTIC KITThe pen mechanism in-

cluded with the robot allows itto draw. In addition to drawingstraight lines, it can also accu-rately draw circles, and evendraw out words and shortphrases. WAO II comes with128 x 4 bits RAM and 2K ROM,and is programmed directly viathe keypad attached to it. Withits built-in connector port. WAOII is ready to communicate withyour computer. With theoptional interface kit, you canconnect WAO II to an Apple II,Ile, or II+ computei'. Editing andtransfering of any movementprogram, as well as saving andloading a program can beperformed by the interface kit.The kit includes software,cable, card, and instructions.The programming language isBASIC.

Power Source - 3 AA batteries (not included)

STOCK If DESCRIPTION 1-9 13-24 25+

MV961 WAD II Programmable Robotic KitWIIAP Interlace Kit For Apple 11,11E, IP

79.9939.99

75.99.-T7 99

68.3934.19

PROTOBOARD DESIGN STATION

The total design workstation - includingexpanded instrumentation, breadboardand power supply.

Ideal for analog, digital arid micro-processor circuits

8 logic probe circuits Function generator with continuously

variable size, square, triangle waveforms, plus TTL pulses

Triple power supply offers fixed 5 VDCsupply plus 2 variable outputs - - 15VDC and -5 - 15 VDC

8 TTL compatible LED indicators, switches Pulsers Potentiometers Audio experimentation speaker Multiple features in one complete test

instrument saves hundreds of dotlarsneeded for individual units

Unlimited lifetime guarantee on bread-board sockets

Fixed DC output+5 VDC @ 1.0 amp, ripple - 5 mV

Variable DC output- to *15 VDC 0.5 amp, rippe -5 mV

Variable DC output-5-to-is VDC @ 0.5 amp, ripple -

5 mVFrequency generatorfrequency range: 0,1 Hz to 100 KHz in 6rangesoutput voltage: 0 to 10V (20 Vp-p)output impedance: 600 (except TTL)output current: 10mA max.. short circuitprotectedoutput waveforms: sine, square, Mange,TTLsine wave: distortion 3% (10 Hz to 100KHz)TTL pulse: rise and fall time 25nsdrive 20 TTL loadsSquare wave: rise and fall time T 1.5 sLogic Indicators8 LED's, active high, 1.4 volt (nominal)threshold, inputs protected to t 20 voltsDebounced pushbuttons (pulsers)2 push-button operated, open -collectoroutput pulsers, each with 1 normally -open, 1 normally -closed output. Eachoutput can sink up to 250 mAPotentiometers1 - 1K , 1 10K , all leads availableand uncommittedBNC connectors2 BNC connectors pin available anduncommitted shell connected to groundSpeaker0.25 W. 8 12Breadboarding area2520 uncommitted tie pointsDimensions11.5" long x 16" wide x 6.5" highInput3 wire AC line input (117 V, 60 Hztypical)Weight7 lbs.

STOCK a DESCRIPTION 1-9 10-24 25*

PB503 Protoboard Decign Station 299.99 284.99 256.49

IDC BENCH ASSEMBLY PRESS

PV505 Panayise

The Panavise PV505 114 tonmanual IDC bench assemblypress is a rugged practical instal-lation tool designed for lowvolume. mass termination ofvarious IDC connectors on flatribbon cable Assembly base & standard

platen included Base plate & platen may be

rotated 90' for maximumversatility

Base plates & cutting acces-sories are quickly changedwithout any tools required

Additional accessories below Size - 10" W x8.75" D x 9" H Weight - 5.5 lbs

tan Assembly Press 49 99 42 49 28 24

COLLIMATING PENA low power collimator pen contain-

ing a MOVPE grown gain GaAlAs laser.This collimator pen delivers a maximumCW output power of 2.5 mW at 820 nir.

The operating voltage of 2.2-2.5v @90-150mA is designed for lower powerapplications such as data retrieval.telemetry. alignment. etc.

The non -hermetic stainless steel caseis specifically designed for easy align-ment in an optical read or write system,and consists of a lens and a laser diode.The lens system collimates the diverg-ing laser light 18 mrad The wavef rollquality is diffraction limited.

The housing is circular and precision manteactured measuring 11_0mm in diameter and 27.0 man long Data sheet included.

As with all special buy items, quantity is limited to stock on hand.

SB1052 Infra -Red Collimator Pen 49.99 47 49 42.14

COLLIMATING LENS DUAL MODE LASER POINTERThis economical collimatinglens assembly consists of ablack anodized aluminumbarrel that acts as a heat sink.and a glass lens with a focalpoint of 7 5 rnm Designed to 11tstandard 9rtirn laser diodes.this assembly will fit all theabove laser diodes. Simplyplace diode in the lens assem-bly adjust beam to desiredlocus then set with adhesive

STOCK a DESCRIPTION 1-9 10-24 25.

LSLENS Colam.qing Lens Assembly 24 99 23 74 21.37

POWER SUPPLY Input 115730V

Output (a 3 75A 12u7 15A17v a: 4A

S,e 7 I. x 5 Wx? H

STOCK # PRICEPS1003 $19.99

New slimlire laser pointer is onlyin diamete x 6 :" long and weighsunder 2 01 670 em @ less than 1mW produces a 6 mm beam 2switche& cne for continuous mode.and one for pulse mode (red dotflashes rapidly) 2 AAA batteriesprovide 8 hours of use 1 yearwarranty

STOCK a DESCRIPTION 1-9 10-24 25.

1P35 Dual Mode Laser Pointe 199.99 189.99

ROBOTIC ARM KIT70.99

Robots were once confined to sciencefiction movies Today, whether they'reperforming dangerous tasks or puttingtogether complex products roboticsare finding their way into more andmore industries The Robotic Arm Kitis an educational kit that teachesbasic robotic arm fundamentals as wellas testing your own motor skills.Command it to perform simple tasks.

STOCK # PRICEY01 $43.99

LDM135-.5LDM135-1LOM135-2LDM135-3

LASER DIODE MODULEThe LDM 135 integrated as-

sembly consisting of a laserdiode, collimating optics anddrive electronics within a singlecompact housing. Produces abright red dot at 660-685 em It issupplied complete with leads forconnection to a DC power supplyfrom 3 to 5.25 V

Though pre-set to produce aparallel beam. the focal lengthcan readily be adjusted to focusthe beam to a spot.

Sturdy, small and self-con-tained, the LDM135 is a precisiondevice designed for a wide rangeof applications 0.64" dom. x 2"long.

5 mW Laser Diode Module1 mW Laser Diode Module2 mW Laser Diode Module3 mW Laser Diode Module

179.99 170.99 153.89189.99 180.49 162.44199.99 189.99 170.99209.99 199.49 179.54

He-Ne TUBESNew. tested 632nm He-Ne lasertubes ranging from .5mW to 3mW(our choice) Perfect for hobbyistsfor home projects. Because of thevariety we purchase we cannotguarantee specific outputs will beavailable at time of order. All unitsare new tested, and guaranteedto function at manufacturersspecifications.

STOCK DESCRIPTION 1-9 10-24 25+

LT1001 He -He Laser Tube 69.99 6649 59.84

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680093 680097

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680093 0 500 0 4.2$680097 0 840 $ 5.95680098 2 1380 $1175680100 4 2390 $22 95

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FLUKE 86 AUTOMOTIVE $367FLUKE 88 AUTOMOTIVE '423

FLUKE 45 $579

FLUKE 97 SCOPEMETER

NEW! SCOPEMETER SERIESHAND HELD, 50 MHz, DUAL CHANNEL

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Duracell Eveready9V Alkaline Battery'1.95 ea$1.75 ea 10+

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0.37"7 SEGMENTLED READOUT

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COURTEOUS SERVICE QUALITY PARTS DISCOUNT PRICES FAST SHIPPING

"MAX" The Remote VCR Controller"MAX" allows you to watch and control

a single VCR from other locations inthe house. Transmits audio, video

and IR signals up to 100 feel throughmini -cable. Works on up to 4 televisionsat a time, but a separate "MAX" receiver

is required for each TV. Can also beused with other infrared controller devicessuch as CD players or stereos. Because

it is hardwired, signal transmission isclearer than more expensive non -hardwired

units. Includes transmitter, receiver, 100 cable, hook-up cables and wall transformer.These new units originally sold for over $100.00.

CAT# MAX $40.00 each 4 or more $35.00 each

TOUCH DIMMERThe "brain"part of the"LITETOUCH"touch dimmer,when connectedto any lamp,will turn it on and off and change thebrightness level when any metal part istouched. We don't have the wiring har-ness that originally connected this to thelamp, but we can provide a simple hook-up diagram and instruction sheet. Thesolid-state circuitry is contained in a ther-mo-plastic box 1.91" X 3.11" X 0.835".

CAT# DMR-1 $3.50 each

OPTO-SENSORSGE H1381U-shaped opto with0.125" gap betweenemmiter and sensor.0.75" mounting centers.CAT# OSU-11 2 for $1.00

TRW/Optron # OPB5447-2IR emitter/sensor pair inrectangular package with28" color coded leads.

L.E.D.'S

Standard JUMBODiffused T t-3/4 size (5 mm)

RED CAT# LED -110 for $1.50 100 for $13.00

GREEN CAT# LED -210 for $2.00 100 for $17.00

YELLOW CAT# LED -310 for $2.00 100 for $17.00

FLASHING LEDW/ built in flashing circuit5 volt operation. T 1-3/4(5mm)

RED $1.00 eachCAT# LED -4 10 for $9.50

GREEN $1.00 eachCAT# LED -4G 10 for $9.50

YELLOW $1.00 eachCAT# LED -4Y 10 for $9.50

LED HOLDER

Two piece holder.CAT# HLED 10 for 65o

RECHARGEABLECAT# OSR-4 2 for $1.00BATTERIES4 AMP Full Wave BRIDGE

#RS405L4 Amp 500 pivEpoxy package.In -Line leadsCAT# FWB-40585e each

Rechargable BatteriesSUB -C 2 PACK

2 Sub -Cnickel -cadmiumbatteries withsolder tabs.Connected in series.This size battery istypically found inpower tools, remote control models,electric shavers and other homeappliances. Each battery measures0.8T diameter X 1.66" long.

CAT* NCB -2C $3.50 per pack

Nickel -Cad

CLJ

AAA SIZE $1.50 each1.2 volts 180 mAhCATO NCB -AAA

AA SIZE $2.00 each1.25 volts 500 mAh

CAT# NCB -AA

AA SIZE $2.20 eachWITH SOLDER TABS

CAIN NCB-SAA

C SIZE $4.25 each1.2 volts 1200 mAh

CAT# NCB -C

D SIZE $4.50 each1.2 volts 1200 mAh

CAT# NCB -D

WIRELESS REMOTE CONTROL FOR NINTENDOTM

ATTENTIONNINTENDOrm

USERS!!!

CAMERICA "Freedom Connection",.Turns your wired Nintendo,. control paddle into a remote control unit. Infrared remote likethose used on TVs and VCR's eliminates messy wires. Allows players more mobility. Twoplayers can use one remote unit except on games where they play simultaneously. In thosegames two "Freedom Connections" units are required. A well-known national discount toychain sells these for more than twice our price. Operates on 4 AM batteries (not included).

CAT# IR-1 $9.95 eachSet of 4 AAA batteries CAT# BAT-4AAA $2.40 per set

14/3 LINE CORD8' BLACK SJT 14/3

Heavy duty A.G. power cord. Standard 3prong grounded plug one end, bare wire theopposite end. Blue, brown, green w/stripewire color code. 0.37" nom. o.d.CATM RDAC-HD8 $4.50 each

WALL TRANSFORMERS

12 Vdc 500 ma.2.1rnm D.C. powerplus with center

negative. White case.CAT# DCTX-125W $4.50 each12 Vdc 200 ma.

2.1 mm D.C. power plug with center nega-tive. CAT# DCTX-122 $3.00 each

HEAT SINK COMPOUND

G C Electronics # 10-8109 - For effectivetransfer of heat between components andheat sinks. Z9 silicone heat sink compound.CATS HSC-1 $2.00 per 1 oz tube

PHOTORESISTOR1.000 ohms bright light.16K ohms dark0.182" dia. X .08"high. 0.18" long leads.

CAT# PRE -7 2 for $1.00100 for $45.00 1000 for $400.00

DIP RELAYSMiniature Relays With Pin

Configuration To Fit 14 DIP.

ingonla.414.'1'

5 Vdc - S.P.S.T.GI Clare # PRMA-1A05B.Normally open reed relay.500 ohm coil. U.L. listed.

Diode protected.CAT# DRLY-57 $1.50 each

12 Vdc - S.P.S.T.Gordos# 846A-412

575 ohm colt. Sealed.Internal clamping diode.

CAIN DRLY-12 $1.25 each

24 Vdc - S.P.D.T.GI Clare # PRMA 1C24

2,150 ohm coil.10 vA switching power.

CAT# DRLY-1C24 $1.00 ea48Vdc - S.P.D.T.

Aromat # DS1 E-A-DC48V5,750 ohm coil.2 amp contacts.

CAT# RLY-788 $1.00 each

SWITCHESPushbutton SwitchSMK Manufacturing0.47 squareblack pushbutton.SPST normal'yopen. 4 p.c. pins for mount-ing. Ideal for low currentswitching app'ications.

CAT* PB-295 for $1.00 100 for $15.00

RFI/EMI LINE FILTERCorcom# 20B620 amp RFI/EMIgeneral purposecommon -modefilter. Controlsline -to -ground noise.Small size, low leakage.3.46" X 1.16" X 2.81".UL and CSA listed.

CAT# RR -201 $8.50 each

HALL EFFECT SENSORS

Microswitch #SS41Tiny, solid state switch -0reacts instantly toproximity of magnetic field.Operates at extremely high speeds,up to 100 khz. Case size: 0.12" X0.17" X 0.06" thick. 4.5 Vdc to 24 Vdcsupply voltage. 10 ma. sink typedigital output. Operating gauss -15 to 40. P.C. leads.

CAT# HESW-2 75e each10 for $6.50 100 for $60.00

SURFACE MOUNT STYLE

Sprague # UGN3075LTOperates on 4.5 - 24 VoltsCan sink 10 ma With suitable outputpull up, can be used directly withbi-polar or CMOS logic circuits.Especially suited for electronic com-mutation in brushless D.C. motors us-ing multiple ring magnets. Very tinysurface mount package 0.175" X0.07X 0.06" thick.

CAT # HESW-5 2 for $1.00100 for $45.00

LARGE QUANTITIES AVAILABLE

Highest Quality METAL CASSETTESPremium quality metal tape in C-60 style cassettes (30 or more per side).One of the finest "brand -name" tapes on the market, in durable, clear plastictransport mechanisms. Recorded and bulk erased, the record -protect tabshave been removed and therefore, need to be taped over to re-record.Audiophiles will appreciate the wide dynamic range of this tape. If yourcassette deck has a 'metal" setting you will hear the difference. A real bargainl60 min. tape - CAT# C -600M $1.25 each 10 for $10.00

CASSETTE STORAGE CASEBlack, unbreakable plastic audio cassette storage case.CAT# CBOX 5 for $1.00 100 for $15.00

r

011 00

ORDER TOLL FREE 1-800-826-5432FAX (818) 781-2653 INFORMATION (818) 904-0524

Call Or Write For OurFree 64 Page Catalog

Outside the U.S.A. send $2.00postage for a catalog.

Minimum Order $10.00 All Orders Can Be Charged To Visa, MastercardOr Discovercard Checks and Money Orders Accepted By Mail California, AddSales Tax Shipping And Handling $3.50 for the 48 Continental United States -All Others Including Alaska, Hawaii, P.R. And Canada Must Pay Full Shipping

Quantities Limited No C.O.D. Prices Subject to change without notice.

DISC9VE

VISA

MAIL ORDERS TO: ALL ELECTRONICS CORP P.O. BOX 567 VAN NUYS, CA 91408CIR-CLE 107 ON FREE INFORMATION CARD

CABLE DESCRAMBLERSConverters Remote Controls Descramblers more

All major brands carried*JERROLD, *TOCOM, *ZENITH*GENERAL INSTRUMENTS*SCIENTIFIC ATLANTA, *OAK*HAMLIN, *EAGLE, *PIONEER7th Year in business. Thank YouMember of Omaha Chamber of Commerce1 Year warranty on new equipment30 Day money back guaranteeOrders shipped from stock within 24 hours

CALL TODAY FOR A FREE CATALOG

1-800-624-1150= C.O.D.nospripearo

4, 40,t 0MAW .ELSCritatitC1

875 SO. 72nd St+74,Dw Ng> Omaha, NE 68114

el


106

CABLE BOXESBELOW WHOLESALEGUARANTEED STOCK - COD'S

- DESCRAMBLERS-(QTY) (10) (20) (50) (100)TB 23 45 40 36 33SA3-B 45 40 36 33XN12 + 43 38 34 29SB 2.3 43 38 34 30

60 CH REMOTE CONV/DECODERDRX-DIC 90 75 70 65SYL DIC 75 60 50 4,5

CONVERTERS W/REMOTES PANASONIC TZPC145

5 YR. WAR. + PARENTAL + 86 CHTIMER + MEMORY + CH 2 OR 3 +

NEW 70 65 61 57

REFURB 60 CH W/REMOTES-4040 38 36 34 31

HAMLIN-ZEN ITH-TOCOM-CALLIT IS NOT THE INTENT OF LAKE SYLVAN SALES TO DEFRAUDANY CABLE -ELEVISION OPERATOR FEDERAL AND STATELAWS PROVIDE SUBSTANTIAL PENALTIES FOR THEFT OFCABLE TELEVISION SERVICES

LAKE SYLVAN SALES, INC.SORRY. NO MINNESOTA SALES

800-800-4582DESCRAMBLERS PLUS!

ADVERTISING INDEXRADIO -ELECTRONICS does not assume any responsibility for errors that may appearin the index below.

Free Information Number Page

108 AMC Sales 90

75 Ace Products 86, 102

107 All Electronics 105

Amazing Concepts 102

77 B&K Precision 24

109 C & S Sales 23

CIE 3 18

198 Cable Warehouse 76

50 Caig Laboratories 26

179 Chenesko Products 86

Command Productions . 13 27

181 Communications Specialists 87

55 Contact East 86

187 Datak Corporation 26

127 Deco Industries 86

182 EasyTech 99

183 Electronic Goldmine 94

Electronic Tech. Today 80

- Electronics Book Club 28

121 Fluke Manufacturing CV2

176 Global Specialties 7

Grantham College 79

86 Heathkit 75

HighText Publications, Inc 24

ICS Computer Training 90

114 Jameco 100

180 Kelvin 104

199 Lake Sylvan Sales, Inc. 106

200 M&G Electronics 98

87 MCM Electronics 95

188 MD Electronics 106

184 MJS Design 86

93 Mark V. Electronics 97

117 Mouser 76

NR1 Schools 8

71 NTE Electronics CV3

195 Optoelectronics 17

56 Parts Express 96

197 People's College . 25

78 Radio Shack 12

R -E Video Offer 64

177 SCO Electronics 81

196 TECI 87

92,190 Tektronix 5 CV4

- The School of VCR Repair 83

194 Unicorn 103

178 U.S. Cable 81

192,193 Viejo Publications 13, 76

185 WPT Publications 87

- Willabee & Ward 15

191 Worldwide Cable 98

186 Xandi Electronics 86

ADVERTISING SALES OFFICEGernsback Publications, Inc.500-B Bi-County Blvd.Farmingdale, NY 1173514516) 293-3000President: Larry StecklerFor Advertising ONLY516-293-3000Fax 1-516-293-3115Larry Steckler

publisherChristina Estrada

assistant to the PresidentArline Fishman

advertising directorDenise Haven

advertising assistantKelly McQuade

credit managerSubscriber Customer Service1-800-288-0652Order Entry for New Subscribers1-800-999-71397:00 AM - 6:00 PM M -F MSTSALES OFFICESEAST/SOUTHEASTStanley Levitan, Eastern Sales ManagerRadio -Electronics1 Overlook Ave.Great Neck, NY 110211-516-487-9357, 1-516-293-3000Fax 1-516-487-8402MIDWEST/Texas/Arkansas/Okla.Ralph Bergen, Midwest Sales ManagerRadio -ElectronicsOne Northfield Plaza, Suite 300Northfield, IL 60093-12141-708-446-1444Fax 1-708-559-0562

PACIFIC COAST/Mountain StatesMarvin Green, Pacific Sales ManagerRadio -Electronics5430 Van Nuys Blvd. Suite 316Sherman Oaks, CA 914011-818-986-2001Fax 1-818-986-2009RE ShopperJoe Shere, National RepresentativeP.O. Box 169Idyllwild, CA 925491-714-659-9743Fax 1-714-659-2469


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"ULTIMATE PROFESSIONAL'Here's the newest family member: the 60 MHz Tek 224.It's as rugged, reliable and easy to use as the rest of the220 Series-and extended bandwidth makes it the logicalchoice for computer service professionals.

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RUGGED SURVIVALIST"Tek's 222PS Power Scout' offers the field -proven per-formance of the 222, plus it's rated 600 VAC, 850 VDCand 6 kV peak surge. Perfect for circuit measurementsrequiring extra protection-and afew added guts.

-4111111/4.

Copyright 01991, Tektionix, Inc,

222PS 13°°1erSc°tIt

"ACE TROUBLESHOOTER"The Tek 222 is everything a service scope ought to be.Lightweight. Rugged. Fully programmable. Floatableto ± 400 V. Two channels, 10 MHz, Auto Setup andAuto Trigger make it easy finding trouble-fast.

1.37 - .5 owS

Tektronix De .TAIL_ STORAGE

They're just 4V2 pounds. U.L. certified. And start at $2450. 220 Serieshandheld oscilloscopes-all with Tek's exclusive Iso]latedChannelTMarchitecture -are the service tools the professionals use. There's one

with you written all over it. To order, contact your Tek representativeor distributor. Or just call Tek direct: 1-800-426-2200

TektronixJest and Measurement

MAP

TR1GGEEt VII

SEC ,DIV

40W-187643-1

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