[Elecraft] Balun Questions

[Dave Cole]

Hi Jim,

I have been reading about your exploits with THHN, and the 100 to 50
ohm change caused by the insulation... 

I am going to pick some up today and wind a choke using it, (as opposed
to enameled 14 GA copper), to see just how close to 50 ohms it will
come...  Any last minute tips? 

BTW, thanks again for publishing all of your work!

-- 
73's, and thanks,
Dave

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On Tue, 2016-02-09 at 10:10 -0800, Jim Brown wrote:
> 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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