TopBand: Sources of radial wire

[W8AV]

<< he next best source I'm aware of is electric fence wire, available at farm
 suppliers such as Tractor Service Co or Quality Farm and Fleet.  It costs
 about $25.00 for a half mile.  I've never used it. I think it's galvanized,
 so should stand burial OK.  Aluminum will not.  It will be attacked and
 destroyed by chemical reactions in the soil.  
  >>

The only thing to be aware of with electric fence wire is that it will rust
when exposed to the wet earth for a period of time.  Once the rusting happens
the return currents can no longer flow effectively on the surface of the wire
and your antenna efficiency goes to pot.  I have used electric fence wire here
from time to time on prototye antennas but then change to bare copper wire to
make the installation permanent.  For elevated radials, electric fence wire
will last somewhat longer.  Also it is pretty hard to solder to ( I only use
silver solder) as what galvanizing is there is not very thick and the solder
does not stick to steel very well. 

<There is another reason to avoid aluminum.  It's the reason electricians
are not fond of it.  That is, when aluminum is in a compression connection
such as a screw terminal and it cools, the aluminum is squeezed.  The
squeezing causes it to spread sideways.  When it warms up, it doesn't
expand as much as it was squeezed because it's now wider.  Sort of like
expecting toothpaste to be resilient.  The result is that the copper
terminal expands more than the aluminum, so the joint becomes loose.  If
any appreciable current is flowing through the joint, it will then become
hot.  If hot enough, the aluminum will begin to oxidize.  Aluminum oxide is
a pretty good insulator.  You get the picture.  I'm using aluminum wire for
my elevated radials, but I make sure that I periodically check the screws
in the connections for tightness.  There are also joint compounds available
from electrical suppliers which will help. >


Actually what happens is that electrolysis will occur when you join two
dissimilar metals, e.g. copper and aluminum.  The connection will begin to
corrode  when exposed to the weather and  will become very high resistance if
it even conducts current at all.  This will happen despite the different
coefficients of expansion between the copper and the aluminum.  There is a way
to retard the electrolysis, though.  If you use an antioxidant compound (such
as Penetrox or Cramolin) you can slow the process down significantly.  I think
this is the joint compounds you refered to Larry.

73................de Goose W8AV 

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