[TowerTalk] Stretching THHN house wiring

[Clive Whelan]

Pete


Not sure if it's relevant, but I discovered to my cost when
making a 21Mhz Moxon that typical PVC insulated wire will
exhibit a "velocity factor", and ends up 3 to 4% long. This
may not be very significant for say an 80m dipole, but sure
as hell is for a 21Mhz wire yagi. In the end I used bare
wire.

I don't know your house wire, but almost certainly it is
soft drawn. and WILL stretch under tension. How much and for
how long? Think of a number.


73


Clive
GW3NJW

-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com]On Behalf Of Pete
Smith
Sent: 29 November 2006 17:52
To: towertalk at contesting.com
Subject: [TowerTalk] Stretching THHN house wiring


Is THHN and similar, garden-variety house wire soft-drawn or
hard?  If the former, what is a reasonable expectation as to
how much it will stretch under, say, 100 lb of tension
before work hardening sets in and it stops?

The reason I ask is that the resonant frequency of my
4-dipole lazy-vee array for 80 seems to have shifted
downward about 150 KHz, which would be 4- 5 percent, and I'm
wondering if stretching could account for that.

73, Pete N4ZR
The World HF Contest Station Database
Full details on 3226 contest stations
recently updated at http://www.pvrc.org/WCSD/WCSDsearch.htm

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