First of all, thanks for the excellent information provided in your
tutorials and reflector postings.
Per your comment below, I'm curious why I don't hear people using small
diameter high-flexibility heliax for ferrite core baluns. FSJ1-50 (1/4
inch diameter) and FSJ2-50 (3/8 inch diameter) are both rated for a
one-time bend radius of 1 inch, and either should handle a lot of
power. Short lengths (5 to 50 feet) of both types regularly show up on
eBay at well under a buck a foot. Official Andrew connectors are also
usually available, although at HF I don't think it should be a problem
to simply hardwire the heliax to more common connectors.
Jim Brown wrote:
> So it is important to minimize the contribution of the coax that is outside
> the cores. That contribution will be least if the diameter is smallest and
> the turns are widely spaced. Increasing the diameter of the turns lowers
> the resonant frequency of the choke a lot if you allow the turns to be
> closely spaced outside the toroid stack, but not a lot if you do not. The
> MOST important thing about winding these chokes is to keep the turns widely
> spaced outside the stack. I recommend the smallest diameter that does not
> compromise the recommended bend radius of the coax.
> Jim Brown K9YC
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