> If your beam uses a balun, can you also wind some of the excess coax
> a choke just before the balun?
If the existing balun works, the coax choke is totally useless there
and it's probably better to collect an excess of cable somewhere else.
> Would say 8 turns of about 6" diameter be the proper size?
It depends by the antenna band/s, and by the size of the used cable.
The effective choke reactance is directly proportional with number of
turns and winding diameter but inversely to the winding lenght.
Reactance is also negatively affacted by capacitance between turns and
larger cables have more.
An 8 turns choke with RG58 (RG142) will isolate better (higher
reactance) than 8 turns with RG213.
A smaller winding diameter requires more turns than a larger one but
has less stray capacitance and is more effective on highest bands.
> How close to the balun should it be?
If the conventional balun doesn't work, it's better to remove it.
When used like a balun, a choke should be placed as close as possible
to the antenna.
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