[RFI] Choke questions

[Grant Saviers]

It could happen, but I've not experienced it.  It was a problem with TFE 
insulated wire wrap if the wire route was very tight to a post.  The 
spec on posts was 0.002" maximum corner radius and I've never seen 
anything that sharp on ferrite cores.

Another factor is it is pretty difficult to get a very tight wrap with 
RG400 or #12. If concerned, then 1/4" or 3/8" wide kapton tape wrap of 
the core is a choice.  Or diamond file any rough spots.

IIRC, Fair-Rite also offers optional epoxy coatings for most all 
products, but I've never seen that for #31 cores in stock.

Grant KZ1W

On 1/21/2020 12:47, K9MA wrote:
> Back in my spacecraft hardware building career, it was well known that 
> Teflon would "cold flow". Great care was taken where wires went around 
> corners, etc., that there was no pressure on the insulation. Has anyone 
> heard of such issues with chokes?
> 
> 73,
> Scott K9MA
> 
> 
> On 1/21/2020 12:21, Jim Brown wrote:
>> On 1/21/2020 9:32 AM, EDWARDS, EDDIE J via RFI wrote:
>>> Use coaxial cable when making RF chokes for antenna systems.
>>
>> Parallel wires work fine for winding chokes. There's no need for 
>> shielding -- the field from the choke is confined to the core.
>>
>> At least half of the chokes in my station are wound with a pair of 
>> Teflon insulated #12 stranded silver-coated copper wire. The rest are 
>> wound with RG400. The Cookbook includes data for #12 THHN as a lower 
>> cost alternative.
>>
>> http://k9yc.com/2018Cookbook.pdf
>>
>> 73, Jim K9YC
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> 
>