There are three basic approaches:
1) There is some literature in the journals on the effect of insulation on
wires which was the basis of the math in the second approach
2) NEC4 (which understands insulated wires)(but needs licensing)
3) blind empiricism (cut it a bit long and trim)
Just as a note, if your design needs <1% accuracy to work, how do you
account for things like catenary sag, movement of elements in the wind, etc.
How were you planning on confirming the pattern? Measuring patterns of HF
antennas is a decidedly non trivial problem.
----- Original Message -----
From: "Roger Parsons" <ve3zi@hotmail.com>
To: <towertalk@contesting.com>
Sent: Monday, July 28, 2003 10:53 AM
Subject: [TowerTalk] Insulated Wire
> I am building a wire array using insulated wire (copper clad steel +
> jacket). The insulation will change the velocity factor of the wire and
> therefore change the required lengths of the elements. EZNEC does not have
> an option to calculate the actual lengths required, and I am wondering if
> there is any way to do this? It will be very difficult (and expensive) to
> change the antenna once erected, and as the effect would be primarily on
the
> array pattern rather than the feed SWR it would be hard to 'tweak'.
>
> I have seen suggestions that wires should be 3% shorter or 5% shorter but
> then cut and try - that is a lot of difference!
>
> Any suggestions would be gratefully received.
>
> 73 Roger
> VE3ZI
>
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