presented by dale svetanoff, wa9ena jones county (iowa) ec iowa technical coordinator inarte...

Simplex Operations & ARES®

The Issues

Presented by

Dale Svetanoff, WA9ENAJones County (Iowa) EC

Iowa Technical CoordinatoriNARTE Certified Sr. EMC Engineer

March, 2015

© 2015, E-N-A Systems, LLCMonticello, Iowa

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Dale Svetanoff, WA9ENA, was first licensed in 1962

Appointed Jones County EC and Iowa Technical Coordinator in 2013

Advanced Class License, active 160m thru 70cm Practicing EMC engineer for more than 35 years Active on VHF/UHF simplex modes for 50+ years

◦ FM, SSB, AM◦ Prior to arrival in IA in 2000, simplex/repeater operation

percentage was roughly 70/30. Chair of IEEE Cedar Rapids EMC Society Chapter President of E-N-A Systems, LLC – EMC consulting Member: ARRL, ARES, QCWA, CCA, AWA, JCARC,

IEEE, iNARTE, etc.

EMC & ARES – Presenter’s Bio

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Simplex – What is it?◦ Simplex is, from a ham perspective, the exchange of

information using one communication channel, alternating between transmit and receive modes

There are 3 main simplex-related issues associated with Amateur Radio operations:◦ Limitations of area coverage due to terrain◦ Interference due to:

Operations on the same frequency by users not related to the local operation

Operations on the same frequency by distant users due to propagation anomalies

◦ Co-location of multiple radio systems that results in desensing of receivers & interrupted communications

Simplex & ARES – The Issues

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A proper, thorough discussion of these issues would be the subject of a full day seminar

The objective of this presentation is to give participants of this meeting a feel for the basic problems associated with each major issue and some guidance for mitigation and/or avoidance of the problems

Simplex & ARES – The Issues

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I will discuss the terrain and interference issues first, and then concentrate on the co-location problems.

Due to the nature of VHF/UHF propagation, as well as the wavelengths involved, some issues can be resolved by relocation, change of antenna, or use of a different band. Keep all options in mind when evaluating your specific problem.

Simplex & ARES – The Issues

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The “name of the game” at VHF+ frequencies:ALL propagation is Line of Sight, with a few rare exceptions.

Height above terrain is everything – lack of = no communications to distant areas

When repeaters are not available to cover the lower areas (from repeater high locations), you must be able to communicate to and from low lying areas in some manner if the event affects them.

Consider positioning mobile or portable ops in certain locations as required

Simplex & ARES – Terrain Issues

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Consider use of portable masts or towers in critical locations◦ Do you have any serious VHF contest rovers in

your area? They might have a mobile mast!

Simplex & ARES – Terrain Issues

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The first instance, interference from local area users not related to the ARES event, should be addressable by:◦ Use of simplex frequencies not ordinarily used in

your area (monitor a few times per year to gauge local activity)

◦ Discussing the situation with those causing interference to ARES operations – work out “gentlemen’s agreement” or enlist their help

◦ Use of frequencies suggested by the NØGUD matrix so as to minimize interaction with adjacent county activities

Simplex & ARES – Interference

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Propagation anomalies can and do result in unintentional interference to all sorts of VHF+ communications – a real problem for Public Safety folks, a real boost to VHF+ DXers

The chief anomalous prop modes are:◦ Tropo ducting◦ Sporadic-E skip

Either can happen ANY time of the year!

Simplex & ARES – Interference

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Tropospheric Ducting …◦ Occurs mostly during warm weather months, BUT

can happen in Winter (WA9ENA was the beneficiary of an extended QSO with WD9BGA in January, 2015, made possible by a duct: 86 miles, EN-42 to EN-53, 146.58 MHz, 5 watts, FM)

◦ Often occurs ahead of severe storm lines◦ Greatest impact is on 2m and above◦ Typical ducting range of 50 to 300 miles, can be

further◦ Signal polarity does not change

Simplex & ARES – Interference

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Sporadic-E Skip …◦ Occurs mostly during times of increased solar

activity◦ Trans-equatorial skip on 6m happens in Spring and

Fall◦ Greatest impact is on 6m, less so on 2m, very rare

on UHF ◦ Signal polarity varies◦ One-hop distance usually 800 to 1500 miles◦ Example: 2m Sporadic-E was open to EN-42 for

about 15 minutes in late July, 2007. WA9ENA worked Havana, Cuba, during the opening on 2m SSB. He also worked West Coast of Florida in that same opening.

Simplex & ARES – Interference

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So, what can you do if these conditions occur during your ARES event?◦ Try using another frequency◦ Try another band if ops and equipment are

available (ie.: If ducting is the problem, try 6m. If sporadic-E is a problem on 2m, try 70cm.)

◦ Wait for the problem to dissipate Sporadic-E is usually short-lived on 2m and above Tropo ducts can last for hours, or even days

◦ Increase xmit power so as to override the interference, but be mindful of causing problems to the other parties

Simplex & ARES – Interference

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Co-locating multiple radio operations is usually intended to expedite communications between an incident command center (or communications control point) and other parts of a given operation.

Unintended interference issues can, and do, arise when consideration is not given to capabilities of the equipment to be used, frequencies required, antenna types and locations, and transmitter power.

Simplex & ARES – Co-Location

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The realities of co-location interference are easy to overlook when trying to meet rapid deployment and set up requirements in an emergency situation. This is why the co-location issues need to be discussed and addressed before any actual event occurs.

After developing a plan, actual tests should be conducted to affirm that the plan works and that all parties understand the how and why of the equipment arrangements.

Simplex & ARES – Co-Location

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The main issues:◦ Equipment limitations (receiver performance)

◦ Antenna type and placement (Simple vertical versus yagi)

◦ Frequencies used (spacing within a given band)

◦ Transmitter power

Simplex & ARES – Co-Location

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Equipment limitations (receiver performance)◦ The number one issue when receiving antennas are

located near transmit antennas is “desensing” – the reduced (or lost) ability of the receiver to detect the desired signal due to extremely strong in-band signals that saturate the limiter stages, resulting in high IF noise levels that can cause the squelch to close and effectively turning off the receiver.

◦ This situation exists at every single site repeater installation, yet the repeater receivers work just fine. How is that possible?

Simplex & ARES – Co-Location

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◦ The ability of a repeater to operate with good receive sensitivity is obtained with the use of tuned cavities BETWEEN the transmitter and receiver.

◦ One portion of the cavity assembly passes the transmit signal to the antenna (and reduces sideband and spurious amplitudes that may be present), the other portion rejects the transmit signal so that the receiver does not “see” it.

◦ Typical cavity set performance provides 70 to 80 dB of isolation between the transmitter and receiver at the usual 2m separation of 600 kHz (0.6 MHz).

Simplex & ARES – Co-Location

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◦ 70 to 80 dB is a very large amount of isolation. Why is so much needed?

◦ The answer lies in the practical design of “real world” receivers and their circuitry. Users want plenty of sensitivity, which means gain, which makes overload worse.

◦ The most critical aspects of a receiver, relative to desensing issues, are: The type and number of tuned circuits in the front end and

mixer stages The quality of construction used in those circuit areas to

minimize blow-by and maintain high circuit Q

Simplex & ARES – Co-Location

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Example of a design that can help receiver performance - Yaesu FT-90 Multi-band front end:

Simplex & ARES – Co-Location

Tracking filtersin 2m & 70cmsignal paths

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◦ Example of “mediocre” design and construction:

◦ User comment:“Great radio until youget it near a strong RFsource while receivinga weak signal.”

Simplex & ARES – Co-Location

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◦ Examples of “fair” design and construction:

Simplex & ARES – Co-Location

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◦ Examples of “good” design and construction:

Simplex & ARES – Co-Location

Bonus: Name these receivers!

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◦ Example of “good” design and construction:

Simplex & ARES – Co-Location

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◦ Example of “good” design and construction:

Simplex & ARES – Co-Location

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Let’s start with receiver performance, since that is the defining characteristic of what is allowable during multiple in-band radio operations at a single location.

A simple, direct test to show how much signal is required to cause loss of desired received signal is to set up a receiver, 2 RF signal generators, a hybrid (or resistive) combiner, and a meter to measure receiver audio output.

Simplex & ARES – Co-Location

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Here is the “test end” of the test set-up:

Simplex & ARES – Co-Location

Audio meter

RF Input from combiner

Spkr withmeter inputon terminals

R.U.T.

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Here is the “source end” of the test set-up:

Simplex & ARES – Co-Location

To R.U.T.

Sig gen 1

Sig gen 2

Hybrid Combiner

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First test unit: Alinco DR-590 Dual-bander, ca. 1990, 2m receiver board:

Simplex & ARES – Co-Location

RF Front end

Actual receiver

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Detail of RF Front End:

Simplex & ARES – Co-Location

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Detail of single chipreceiver(ref only)

Simplex & ARES – Co-Location

Motorola IC

Ceramic 455 kHz IF filter

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Second test unit: Icom 228-A 2m only, ca. 1989:

Simplex & ARES – Co-Location

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Third test unit: Icom IC-91A HT, Dual-Band, ca. 2011, 2m section only:

Simplex & ARES – Co-Location

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Fourth test unit: Motorola T53 series, ca. 1960s:

Simplex & ARES – Co-Location

RF In

Ext Spkr connector

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Motorola T53 series front end:

Simplex & ARES – Co-Location

RF in

Mixer & IF

LO chain

PermaKay™ IF Filter

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Fifth test unit: Motorola Micor Series, ca. 1971: (Yes, OK to snicker …)

Simplex & ARES – Co-Location

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OK, now after you snickered at “the piece of junk” ..

Simplex & ARES – Co-Location

These are aperture-coupled helical filters

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Tests were run as follows:◦ Set up equipment as shown◦ Set Sig Gen 1 to on-channel frequency with enough

signal level to achieve “near full quieting” on receiver

◦ Modulate test signal with 400 Hz tone at 4.5 kHz deviation (typical ham situation)

◦ Set audio level from R.U.T. so that audio meter is at “0 dB” reading from detected tone

◦ Set Sig Gen 2 to 600 kHz (or 1 MHz) above the test frequency (carrier only – no modulation)

◦ Increase output until audio drops by 6 dB – note level◦ Increase output until all modulation audio is lost –

note level

Simplex & ARES – Co-Location

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Test Results:

Simplex & ARES – Co-Location

R.U.T. DR-590 IC-228A IC-91A T53- Micor

Test Freq (MHz)On-chan Signal (dBm)Signal @ +600 kHz(dBm)Signal @ 1 MHz (dBm)

146.55

-113

-23/-16

-16/-19

146.55

-107

N-A/-10

N-A/-10

146.55

-117

-36/-31

-35/-28

146.94

-97

-2/+2

0/+2

155.475

-113

-10/0

-10/0

All signal levels adjusted for loss factors.

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What do the test results mean?

◦ Remember, 50 watts = +47 dBm (typical rig)

◦ If YOUR radio “crunches” at -16 dBm (600 kHz spacing), then minimum isolation required is 63 dB just to retain some received audio. Factor an isolation requirement of 75 dB so as to have some margin.

◦ Increasing channel separation to 1 MHz only buys a 0 to 7 dB improvement, depending upon the radio’s design.

Simplex & ARES – Co-Location

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How can essential isolation be obtained without use of tuned cavities?

◦ Antenna spacing (vertical or horizontal)

◦ Site separation

◦ Dual band operation – no in-band (when the above options are not available)

Simplex & ARES – Co-Location

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An excellent reference book on FM systems and their problems is:

Practical Handbook of Amateur Radio FM & Repeaters, by Bill Pasternak, WA6ITF, et al, TAB books #1212, Blue Ridge Summit, PA, second printing, May, 1981.

From page 233 of that book comes one of the most useful charts I’ve ever seen (next slide).

Simplex & ARES – Co-Location

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Simplex & ARES – Co-Location

It is important to note that the “minimum”isolation requirementsare based upon repeaterapplications and the useof commercial grade receivers. However, thatdoes not affect the curves themselves.

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Simplex & ARES – Co-Location So … if you want to operate 2 stations on

2m simultaneously, and assuming 50 watt transmitters, if you use a frequency separation of approximately 1 MHz, then the choices are:◦ Two vertical ground planes, one directly above the

other on a common mast, and a vertical distance of more than 60 feet (if using “typical” ham radios) or about 46 feet if using commercial grade radios.

◦ Two separate masts, one antenna on each, with horizontal separation of 200 to 450 feet, depending on quality of the radio receivers. (Think “football field separation” for starters.)

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Simplex & ARES – Co-Location If your situation can not provide a tall

enough mast or enough horizontal spread, then you can:

◦ Reduce transmit power to 5 watts (reduces isolation requirement by 10 dB)

◦ Use 2 different bands, depending upon available equipment (Note: Make certain that any 70cm frequencies chosen are not 3rd harmonics of 2m frequencies.)

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Summary of good things to do:◦ Make certain that all participants know their

equipment well and have all likely frequencies programmed in prior to an event

◦ Plan and run at least one practice field deployment to see if what you have figured to work WILL work.

◦ Know and understand about how to cope with prop anomalies, which can occur suddenly at times.

◦ Know and understand any RF coverage problems unique to your area or the anticipated assignment

◦ Try to learn from other hams and/or public safety officials about any other communication problems in the area of deployment.

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QUESTIONS?

Contact Dale Svetanoff, WA9ENA, via:

wa9ena@arrl.net or

e-n-asystems@earthlink.netor

(319) 462-5984

Simplex & ARES