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@contesting.com wrote:
>
> From: Steve Maki <lists@oakcom.org <mailto:lists@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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|