[TowerTalk] Topband: Dielectric Constant of THHN

Gary and Kathleen Pearse pearse at gci.net
Mon Oct 22 20:40:20 EDT 2007

Hello Jim K9YC from Gary NL7Y...I've built dozens of wire antennas  
out of #12/14 THHN...I decrease the typical textbook dimensions about  
3% when using coated wire...for example, I use 226 for verts, and 453  
for dipoles /f MHz to get real close depending upon height above  
electrical ground...loops run -3% also from the text 1005/f Mhz, but  
resonant length will vary depending on the shape and height of the  
loop...973/f MHz is a good one to shoot for...my penny's worth.

73 Gary NL7Y

On Oct 22, 2007, at 1:55 PM, Jim Brown wrote:

> I use THHN for antenna wire. For purposes of using NEC to design for
> length, I need the diectric constant of the insulation used in THHN.
> For #12, I've been using a thickness of 0.0445 inch and constant of
> 2.0. Is this a good first approximation?
> Yes, I know I could hang the antenna, check the resonance, then lower
> it and tweak the length. But this puppy has to be fished through some
> trees, and it's a big deal to raise and lower it. So it's worth
> getting as close as possible the first time.
> 73,
> Jim K9YC
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