Topband: THHN

Jim Brown jim at
Tue Oct 23 01:27:01 EDT 2007

On Mon, 22 Oct 2007 19:06:40 -0400 (EDT), n8cc at wrote:

>Faced with this question several years ago, I made a 15 meter dipole
>out of #14 solid copper 600V THHN wire.  I strung it up between a
>tree and  a wooden pole, about 20 feet off the ground.  I checked
>the resonant frequency.  I then lowered the antenna, stripped  the
>insulation off the wire, and repeated the exercise.  The difference
>in resonant frequency was almost exactly 3 percent.  Since then,
>I've observed that THHN wire always makes a difference of between
>2-3 percent from formula, depending on wire size,manufacturer, and
>whether solid or stranded.

>Not the most scientific approach, 

I'd call that VERY scientific -- you set up a controlled experiment and 
carefully measured it! The only way to improve your science would be to 
measure a lot of antennas and a lot of wire types and wire sizes. But 
what you've done was right on, and quite helpful! Thanks. 


Jim K9YC

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