My mailbox was stuff with responses to my request for radial wire info, so
I though it would be a good idea to summarize for the whole list.
In response to my request for vendors, I got a number of leads, none of
which has panned out so far. The lowest cost source of wire remains Home
Depot with #12 insulated available at 3.31 cents/foot and #14 insulated at
2.57 cents/foot (AZ prices, plus tax, of course). Davis RF is the lowest
price for bare wire with #16 going for about 3.6 cents/foot plus shipping.
Salvage yards and such per foot prices are higher than those above prices.
I have no idea why this is so.
Response to my request for information on insulated vs. un-insulated buried
radials was a mixed bag. I really was only looking for references to
technical studies done concerning the RF properties of the two choices. No
one offered such info, but there were a lot of opinions offered.
The vast majority preferred insulated wire with corrosion being the reason
for the choice. It's been a long time since I had to exercise my limited
knowledge of chemistry, so any chemists out there please feel to jump in here.
In my very alkaline AZ soil, I can bury a piece of #16 for ten years and
when I pull it up, it's as good as new except for being dirty. Steel and
Aluminum are a very different story. Maybe the low pH soils in some ares of
the world are worse in this respect than my soil is, but I know that I
don't need to worry about the lifetime of buried bare copper. At the few AM
broadcast antenna installation I have looked close at, the wire was just
bare copper. I would think those application would be very concerned with
lifetime.
Some said the problem was the corrosion layer on the copper and skin effect
causing loss. If this was the case, I should be able to measure degradation
of my buried bare wire radial systems over the course of time. Never have
yet if the wire is not physically damaged. Tom or somebody with ties to the
broad cast industry may be able to help out here.
In my case, the next installation will most likely have the majority of the
radial wires insulated, but only because of cost and availability.
My thanks to everyone who responded.
73,
Larry - W7IUV
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