[TowerTalk] Voltage Breakdown For Enameled Wire

Richard Solomon dickw1ksz at gmail.com
Tue Jan 30 11:43:27 EST 2018

Dumb question ... is the insulation
sufficiently flexible that it will not
crack when wrapped around the
toroid ?

73, Dick, W1KSZ

On Tue, Jan 30, 2018 at 9:37 AM, Jim Thomson <jim.thom at telus.net> wrote:

> Date: Sun, 28 Jan 2018 18:02:55 -0800
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: towertalk reflector <towertalk at contesting.com>
> Subject: [TowerTalk] Voltage Breakdown For Enameled Wire
> <I'm once again considering winding high power chokes with enameled wire.
> Zo of a closely #12 pair is about 53 ohms, which makes it desirable IF
> breakdown voltage is sufficient. I would appreciate for sources of #10
> or #12 enameled wire with published breakdown specs.
> I've found that THHN (about 93 ohms Zo) works fine for simple antennas
> like dipoles, but some multiband antennas with complex matching/coupling
> systems don't like that much mismatch. We had this problem with the
> Force 12 C3SS, the choke is enameled #12 of unknown pedigree. No
> breakdown issues with a 600W power amp and the antenna is a good match
> to it, but the engineer in me wants to be conservative for legal limit
> to an 80/75 dipole that I use from 3.5-3.9 MHz.
> Yes, I know I could put the conductors in Teflon tubing, but that
> increases Zo. I've measured #12 pairs with various Teflon insulation and
> get values around 101 ohms at HF.
> Suggestions?
> 73, Jim K9YC
> ##  I bought a bunch of 10 gauge and also 8 gauge  from SSON, on sale,
> years ago.  It used polyimide.  Was rated for  15 kv, at least in the
> larger gauges,
> like  14-12-10-8.    V rating was reduced with the smaller gauges, since
> if  15 kv
> insulation used on real small stuff, like   18-28 gauge wire, then the
> insulation  would be super
> thick compared to the actual  small gauge wire diameter itself...and  28
> gauge wire would resemble
> something like 20 gauge wire.
> ##  In  Orrs very last handbook, the blue covered one, they had a chart at
> the back of the book, showing
> 3 different  diameters for the SAME  gauge magnet wire.   The difference
> between the 3 was the thickness
> of the insulation used.    This can have a profound effect when winding
> plate chokes for tube amps, and explains
> why 2 identical wound chokes  can have series resonances on  different
> freqs.   The turns per inch was less
> when the thicker insulation was used.
> ##  The stuff I bought hi pot tested to > 15 kv.  And  >  30 kv between
> adjacent turns.   If you really want to go crazy,
> you can slide it into teflon tubing, but as you stated, for your
> application, Zo increases too much.   For my application,
> I was just using it for bifilar fil chokes..and the  15 kv rating was
> gross overkill anyway, but at the time, the price was right.
> ##  What ever you end up buying, easy enough to hi pot test it, which is
> typ done at  DC..or  60 hz  AC.
> Jim   VE7RF
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