I have addressed this by showing photographs of winding techniques for
coax normally used for transmitting, and for short lengths of
transmission line formed by taping together a pair of 4-6 ft of #12
THHN. There's also text that goes with it, noting that winding radius
should follow mfr recommendations for bending radius, that close spacing
should be used to lower the resonant frequency and wider spacing to
raise it.
Note also that the dielectric constant of outer jacket material can have
a quite significant effect on the bandwidth of ferrite chokes. For
example, the bandwidth of those THHN chokes is MUCH greater than chokes
would with typical RG8, RG213, RG11. Years ago, someone sent me a length
of one of the teflon coaxes and I measured some chokes. As I recall,
their bandwidth was lower than those wound with conventional coax.
73, Jim K9YC
73, Jim K9YC
On Tue,2/9/2016 7:45 AM, James Robbins wrote:
Good morning Jim,
I am wondering if you could opine about how “tightly” coax needs to be
wound around a torroid for balun use (or other uses, for that matter)?
In other words, while there have been so many Elecraft postings about
the bending radii of various types of coax, there is no information
posted about how tightly (closely) the coax needs to be wound around
the edge of the toroid. (When I have wound small torroids with magnet
wire, the winding is tight against the core. I’m not sure this is
even possible, let alone needed, for a balun.)
If this is in one of your “papers”, please just refer me to the paper
and I’ll dig it out.
73,
Jim Robbins
N1JR
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