At 5:09 AM -0500 10/10/02, Dennis Mowers wrote:
>I'm using a choke balun formed by winding coax around the boom on a 4
>inch form.
To which I replied:
"The boom will be a big fat shorted turn, so to some extent it will
spoil the choke, but winding coax around the boom on a form should
still work if the diameter of the form is much greater than (say,
more than twice?) the diameter of the boom."
It _might_ still work, but after reflection my advice is _Don't_Do
It_. Not only is the boom a big fat shorted turn, but it has big fat
capacitance to every turn of the coil.
Instead, support your choke coil form below the boom on standoffs,
with least three inches of space between the boom and the near side
of the coil. Make the axis of the coil form parallel to the axis of
the boom, and put one standoff at each end of the form, at least an
inch beyond the end of the winding. Now no shorted turn will be
closely coupled to the coil, and there won't be much added
capacitance to lower the resonant frequency of the choke. And this
arrangement should be pretty sturdy mechanically.
73 de Chuck, W1HIS
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