Hi Jim,
As you probably know a Class 3 insulator material is best.
Some enamels work well at 105C temps, FormVAR variants etc...
If you think it will run hotter there are materials that go a lot
higher,but the price scales with it.
I lucked into a roll of #12 Class 3 using a bondable formVAR.
Tough stuff and very hard to scratch or crack when bending.
I use it in Hybrids and baluns. It can take the voltage even when
tightly winding it (no holes or cracks).
But I still tape the cores too.
Mike K9MK
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of Jim
Brown
Sent: Sunday, January 28, 2018 8:03 PM
To: towertalk reflector
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
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