>
> As I think I understand it, the function of the coiled coax is to keep
> any potential RF from traveling back on the shield of the coax - so -
> putting it as close as possible to the feedpoint makes sense to
> me....
This is a correct point, but not the only reason to have a choke near the
element.
The piece of line that runs between the feed element and the coil is infact
a part of the antenna, another antenna.
What happens is that the portion of line will pick up RF and not only
radiate so negatively affecting the antenna pattern and directivity.
When that piece of line runs close to the boom, then the boom itself will be
capacitively coupled to the element making the parasitic antenna quite
consistent.
Altough rarely considered, common mode currents are actually present both on
TX and RX.
When such situation takes place, then a F/B is negatively afected, F/S is
severly compromised and deep nulls can disappear.
73,
Mauri I4JMY
>
> 73,
>
> Jim, K4OJ
>
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