[Elecraft] Balun Questions

[Jim Brown]

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
>