how antenna matchers...

How Antenna Matchers Work

SMRA Amateur Radio Club

Regular Monthly Meeting

EOC Meeting Rm., Carlisle, PA

18-April-2017

Jack Himes, KA3GLQ

Mentoring credits:

I wish to thank Jerry AA3HB and John W3HMS for their suggestions, comments and encouragement in putting together this presentation. Any errors, omissions and misconceptions are my responsibility.

I learned a lot and hope you will pick up a few new ideas about antenna matchers in the next 15 minutes.

Jack, KA3GLQ

How Antenna Matchers Work.pptx KA3GLQ 2

Simple antenna concepts1. Dipoles2. Verticals

Ways to tune simple antennas1. Dipoles2. Verticals3. Common Tools used to tune antennas

What do antenna matchers do?1. Characteristic Impedance Z0, SWR and Impedance Matching2. Acceptable SWR

Test equipment1. Multimeter2. SWR meters and analyzers3. The meter in your radio

Common Antenna Matchers1. Simple L-C matcher2. Manual L-C matchers3. Auto L-C matchers4. Remote L-C matchers

Proposed Project for a simple 4-band non-resonant dipole and “static” matching device1. Non-resonant dipole and balanced feedline using Zip Cord speaker wire2. AA3HB designed 4-band “static” matching device with discrete coils and caps

References



Simple antenna concepts

Resonant λ/2 Dipole:

Resonant λ/4 Vertical Monopole:


How can antennas such as dipoles and vertical monopoles be tuned?


How can antennas such as dipoles and vertical monopoles be tuned?

Answer: Shorten the antenna or add more wire to achieve an acceptable SWR.


What do antenna matchers do?

Amateur radios have a characteristic impedance of Z0 = 50 ohms resistive

A feedline/antenna system greater than 2.0 SWR result in power fold back to prevent damage

Feedline/antenna impedance may contain capacitive and/or inductive reactances

Matchers counter the capacitive and/or inductive reactances to achieve a low SWR match

An antenna matcher will allow radio to provide full power to unmatched feedline/antenna systems

One antenna can then cover both the CW and Phone portions of 80 meters, etc.

Note: The calculation of the inductive and capacitive reactances and circuits needed to correct these situations are covered in more detail in the ARRL Antenna Book and the ARRL Guide to Antenna Tuners in the Reference list.


Now lets take a look at a few circuits that can be used in antenna matchers, some practical test equipment and some commercially available antenna matchers.

Matching LC circuits contain inductors (L) and capacitors (C). They can be variable or static. The top circuit can match low impedance antennas and the lower circuit can match high impedance antennas. The radio is Z0 = 50 ohms resistive.

Other LC circuits include pi-networks, T-networks(high & low pass), C-L-C and L-C-L networks. Transformers can be useful to match the resistance portion if needed (i.e. Z0 = 50 ohms resistive).


A multimeter can test for opens, shorts and resistance. This device can help solve certain problems and most Amateurs already have one.


The MFJ-259B Analyzer is used by many Hams and can provide much useful information.

The FG-01 analyzer can provide a graphical view of the SWR and other data as shown.

Many other offerings for this type of gear gives you lots of choices if you really want something like these.

Also many radios have built-in SWR meters and power indicators.


Found at the York Hamfest several years ago. Notice large variable capacitor with lots of space between plates and the large diameter tapped coil.


Very popular unit from MFJ. Two coax inputs plus balanced line and long wire inputs. Provision to attach an external dummy load. The 12 V DC input is used to light up the meter if desired.


Note large diameter 12 position tapped coil, variable 1000 volt capacitors with generous space between plates and 4:1 balun upper left. MFJ lists this unit at $149.95 in their 2017 Catalog.


Saw one of these in use at SMRA Field Day 2016. 300 watts SSB, 1.8 through 54 MHz, 12 to 2000 ohms matching (up to 40 SWR?). The 12 VDC is used to light up the meter. Balanced “T” network design using 4 gear driven 1000 volt air variable capacitors. High-Q air wound tapped inductor for 80 – 10 meters.


Note the 1:1 balun (lower right), 4 variable tuning capacitors, large multi-tapped coil so who can live without one of these. Also note the Logged Tuning Chart to the right. Yes, you must fill this out and post at your operating position in case you need to change frequencies, bands or antennas! MFJ sells for $229.95 in their 2017 Catalog.


This LDG unit is a few years old now but can switch between 2 antennas, initiate tune cycle from the front panel or attach the cable to my ICOM rig and let the radio control the tuner.


Inside the LDG unit you can see 7 inductors wound on red toroids, 7 capacitors (dark brown in the center), lots of white boxes housing latching relays to switch capacitors and inductors in and out of the circuit and also re-configure the matching circuit. Notice the CPU in the lower left and the neat surface mount technology.

Latest version is AT-100 Pro II that LDG lists for $229.99. 1.8 – 54 MHz, 2000 memory locations, 125 watts SSB, 30 watts PSK. Tunes 6 to 1000 ohm loads (20.0 SWR).


This Yaesu matcher allowed remote tuning of a random wire antenna with my FT-950 Transceiver. The cable coming out the left side on the bottom is for the coax and the cable on the right is for the control cable. The terminal strip on the short cable allowed the cable to enter the house through a small hole in window panel. Antenna wire is upper left and is 23 feet long and attaches to the ceramic connector on top of the unit. The wing nut on the right is for grounding.


Inside are 7 coils mounted 90 degrees to next coil. In center are 13 capacitors and below the two gray pads are lots of latching relays to switch capacitors and coils in and out of circuits and reconfigure circuits. CPU is in bottom section just right of center. Lots of very tiny surface mount components on this board. Notice black weather seal in groove around perimeter. Unit operates direct from radio panel.

2000 memory settings for instant recall. 5 seconds or less for typical tune time. 1.8 – 54 MHz range with 66 foot minimum wire antenna. $274.95 at Ham Radio Outlet.


Potential SMRA Club Project

1. A 44 foot long non-resonant dipole antenna made from a 50 foot roll of 18 AWG Zip Cord Speaker Wire. The entire 50 foot length of Zip Cord is used with no cuts to give the 44 foot long dipole and a 28 foot long balanced line feeder. Can you figure out how that is done?

2. Jerry Buckwalter (AA3HB) is designing a “Static” Antenna Matcher for 40, 30, 20 & 17 meter bands with discrete capacitors and inductors selected by a 2p6t rotary switch. This antenna and matcher are a “matched set” and are intended to be a low cost, easy to carry and set up antenna and matching system for a variety of situations such as Field Day, hiking, day trips, etc.

More details to follow.


References:

ARRL Antenna Book, 21st Edition.

The ARRL Guide to Antenna Tuners, Joel R. Hallas, W1AR, 1st Edition, 2010.

Practical Antenna Handbook, Fifth Edition, Joseph J. Carr, George W. Hippisley, McGraw-Hill, 2012.

HF Antenna Handbook, William I. Orr, W6SAI, Fourth Printing 2005, CQ Communications, Inc.

For the 44 foot long non-resonant dipole antenna project:

Zip Cord Antennas and Feedlines for Portable Applications, William A. Parmley, KR8L, QST March 2009.

The Broadside Doublet in “My Top Five Backyard Multi-Band Wire HF Antennas” by L.B. Cebik, W4RNL.

Zip-Cord Antennas – Do They Work?, Jerry Hall, K1TD, QST March 1979.

NorCal Doublet Antenna, Doug Henricks, KI6DS, http://www.norcalqrp.org/norcaldoublet.htm.

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