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[TowerTalk] open wire feeders

To: <towertalk@contesting.com>
Subject: [TowerTalk] open wire feeders
From: w8ji.tom@MCIONE.com (w8ji.tom)
Date: Fri, 23 Oct 1998 09:52:12 -0400
Hi Nate,

> At RF, does stranded wire provide any less loss than solid wire for
> transmission lines. 

No, it has MORE loss Nate.

Strandings using parallel strands (even with Litz wire) have more loss
resistance at RF per unit length for a given wire size.

Braiding has several times the loss of a solid smooth surface.

The denser the weave the greater the loss, especially after the wire
corrodes.

Current can not flow on the surface of the strands inside the bundle, or
even on the side facing the wire core! What you wind up with is a bunch of
very thin current carrying regions along the outer surface that zig-zag and
weave all over the place.

As an example, in RF power amplifiers clean braid removed from RG-8/U coax
will melt when used between the tank capacitor and the ten meter inductor
in a circuit with a circulating current of ten or fifteen amperes. Number
ten wire will not heat enough to fail in the same case! This would be
representative of a pair of 3-500Z's at 2500 volts and 750 watts output.

Even Litz wire is the same way at moderate to high radio frequencies.







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