Military Antenna Conversion for CB & Marine

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This article shows you how to use the MX-6707 military antenna for a CB antenna. It makes use of the tuning coils that are built into the antenna. You will not need an external antenna tuner.

I offered $30.00 each for three AS-1729/VRC Full Kits plus freight off of ebay. They were shipped in two boxes one for the MX-6707/VRC base unit and one for the AS-1730/VRC and the AT-1095/VRC whip. Ask the seller to over pack the whips

Two A3046166 Antenna Mounting Brackets

Two 5935714B2 Red Reflectors

Now some notes for the MX-6707 base.

DO NOT PAINT IT!
Overtightening will crack the base. Use a torque wrench 100 in. lb

Now for the fun part:

Take the bottom cover off the MX-6707 and look at the bottom of the unit with the coax cable/connector facing you.
Find the 5th tuning capacitor (small screw driver adjustment) counting from the coax cable in a counter-clockwise direction. This capacitor C8 tunes the lowest band 30-33 MHz on the antenna and will allow you to match the antenna at 27MHz.
Make up a coax feed cable from the CB to the 2 antennas. Bring a ground and a hot to each antenna. You might be able to find a coax 'T' fitting.
You will need to have the whip attached and preferably mounted on the H1. (This is a little trickey but it can be done). If not mounted to the H1, tune the antenna on a wooden ladder, away from any large metal objects. (Like the H1)
Now with an SWR meter attached test to see where you are. Using the C8 adjustment (when making adjustments to C8 only use a plastic screw driver) tune it in.
Reassemble and retest

The tuning switch on the bottom of the MX-6707/VRC is set to 30-33 however you retune that selection to encompass 27 MHz.

Set up for an AS 1729 Antenna on Marine Bands

Icom 2200H 2m VHF (shhh... dont tell anyone, but it's unlocked for extended Tx)
MFJ 822 SWR Meter (cross needle - measures both radiated and reflected power; the needle cross point shows SWR)
MX-6707 Tunable HF Antenna Base
AS 1729 HF Antenna
PL-259 to BNC(m) adapter (the mil antenna uses BNC; the radio uses PL259)

The advertised Tx power for the transceiver is 65W. The best actual Tx power I saw (using the SWR meter) was 60W with 10W reflected, SWR of somewhere between 2.1 and 3 (the meter isn't that precise; I'd guess 2.4 - 2.5?). The setting on the antenna base that achieved the best result was "60-65MHz"... which is weird, because I would have expected an even fraction of 157ish. I did a radio check with the local coast guard radio station (157.125MHz, ch 83a) , and they got me "loud and clear". picked up a few broadcasts on 156.800MHz ch 16.