[TowerTalk] solid THHN vs jacketed copperweld

[gwj at me.com]

Actually 50 ohms (resistance, at resonance) at the feedpoint is perfect. The 1/4-wave, 75-ohm phasing line transforms that to 100 ohms. Then pairs of elements are paralleled to yield 50 ohms. Finally, a 90-degree hybrid combiner drives the two pairs in proper phase.

Difference between the two *insulated* wires should be very small. That assumes the copperweld has at least thick enough copper that it doesn’t start looking like a resistor…

-Gary NA6O

> On Sep 19, 2022, at 2:57 PM, towertalk-request at contesting.com wrote:
> 
> From: Steve Maki <lists at oakcom.org <mailto:lists at oakcom.org>>
> Subject: [TowerTalk] solid THHN vs jacketed copperweld
> 
> 
> Wondering whether there is any substantial difference between #12 solid 
> THHN and #12 PVC jacketed copperweld (steel) in terms of cutting a 
> dipole to length.
> 
> I'm in the process of installing a K8UR style 80M four square. I trimmed 
> the first element to length using THHN. Then I decided that I should use 
> steel wire for at least the top half of the elements because of the high 
> wire tension I ended up with after pulling the feed-point out far enough 
> from the array center. It's an issue with not enough acreage around the 
> tower.
> 
> Even so I ended up with a 50 ohm antenna rather than the desired 30-40 
> ohm antenna per the DXE instruction manual. But that's an entirely 
> difference issue (though I'd appreciate any comments on that as well).
> 
> Should I expect the steel wire lengths to be pretty close to the THHN 
> lengths, or should I re-do the initial step of carefully cutting the 
> first element in isolation?
> 
> TIA!
> 
> -Steve K8LX