Hi Gale,
I build and use a lot of EFHW antennas¡giving many to other members of my portable ops team. There are two general approaches to how the balun wind is connected to the coax. There¡¯s either an external ground connection or not:
A. The so-239 or bnc connector has no external connector for a counterpoise (see B). This makes the coax shield the effective counterpoise. This will put part of the transmitted signal coming down the line to the radio.
IF a choke is placed at the balun connector, the antenna tuning suffers since the signal produces more standing waves. If the choke is placed at the transceiver end, the coax braid more effectively radiates part of the signal, making tuning a match easier.
B. If a connector to the ground side of the balun is placed outside the case, a small counterpoise can be attached which allows for a more effective match. I use 0.05 wl coins n the fundamental design frequency for a ¡°pig tail¡± style counterpoise. Sometimes I add a 1:1 choke at the radio (or tuner) end of the coax but only rarely.
When I build EFHW antennas, I attach a Rig Expert Stick analyzer directly to the balun using a pl-259 to pl-259 adapter when I hang them up for final wire length adjustments. I use the Bluetooth connection to the Antscope 2 software to make the sweep without the contamination effects of the coax. This allows me to get the antenna length ¡ª- and the 0.05wl pig-tail counterpoise ¡ª- more precisely tuned to each band: the fundamental design frequency as well as the higher harmonic bands. Most of my EFHW antennas get hung up in the field and don¡¯t require much ATU activity at all.
This is just how I¡¯ve come up with doing it but others may have superior methods.
73,
Frank
K4FMH
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Frank M. Howell, PhD
Ridgeland, MS
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K4FMH