On Tue, 22 Aug 2006 20:04:24 -0700, Richard Clark
wrote:

On Wed, 23 Aug 2006 02:18:21 GMT, Owen Duffy wrote:

Apart from the challenge of making reliable connections to aluminium,
are there other "issues" that come to mind in using such wire for
antennas?

Hi Owen,

I've used ordinary house wiring for long-wires and they have survived
100# limb falls that ripped out my matching box from its post. The
survival was with the wire, not the box.

I think "ordinary house wire" may be aluminium, a by product of 110V
utilisation I guess. House wiring here is still principally copper.


[warning to Reggie, the prose that follows contains literary
allusions]
What price tensile strength?

The worst thing you can do is pull a wire tight in an attempt to
totally eliminate sag. The inverse sine angle of its depression
magnifies the stress by huge amounts. A slight sag will never yield a
tensile failure in the most pedestrian of wire.

Subject to more reliable information on the wire's GBS, my initial
calcs are that a span of 40m (half of a half wave dipole on 160m)
would need 3.3% sag (~1.4m) to survive wind at 60m/s with a safety
factor of 3.5. Yes, of course, the mountings must also survive the
wind, and this analysis assumes not deflection of the mounting points
and no stretch of the wire.

The only thing that compares on strength and conductivity is
Copperweld, but it is not easily obtained here... I suspect the cost
of freight might double or triple the price of a 100lb pack of 30% #12
wire.

I did look at heavy galvanised wires, but it seems the move has been
to Zinc/Aluminium alloy with an overall synthetic coating, and since
it erodes much slower, the coatings are only 10 to 20 microns... not
thick enough for good conductivity.

My usual supplier looks like he can't do 3mm HDC economically any
more, hence the search.

Owen
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