I have found that aluminum wire is quite "adequate" for center supported
dipoles for 80m or shorter wavelengths. I would expect that the same thing
is true for slopers angled down from towers -- but I have no personal
experience with that application using aluminum.
One does not need to solder wire to assure good conductivity between two
pieces that are 'connected' together. Western Electric ran experiments in
the 'middle ages' of technology that showed wrapped joints would actually
have better conductivity than soldered joints. The result was that the
telephone switching centers had wire wrapped connections rather than
soldered connections. The technique had cost and simplicity advantages as
well. Many of our initial commercial computers had wire-wrapped backplanes.
The Western Electric experiments used copper, not aluminum and the pins that
were wrapped with wire were square in cross section, not round.
Using the same principles one can put 5 turns of aluminum wire tightly
around a second aluminum wire and wrap 5 turns of the second wire around the
first wire about 3 inches away from the first splice wrap. The result is a
very satisfactory splice between the wires. One can fabricate SS fasteners
so that they clamp the aluminum wire -- this allows connections to a center
insulator. Because you can 'splice' in the field by simply wrapping wires
around each other, the center insulator connections to the aluminum can be
fabricated in the shop, carefully protected from the elements by coatings
and then installed simply in the field. I have used this methodology for
the past 10 years with satisfactory [for me] results.
I have not taken the time to determine the conductivity of the 'corroded'
[oxidized] aluminum wire by actual measurement and compared those
measurements with some done using oxidized copper wire. My 'experience' is
that I could not tell that my operating results were different when I used
copper wire 80m dipoles and aluminum wire 80m dipoles. The cost of each type
was noticeably different. It may simply be that my 'operating requirements'
are so low that I just don't notice that things are not good. It could also
be that differences measured in units of 0.1 dB of radiated power can't be
perceived by non-superstar operators.
There is one thing that is a significant negative with respect to aluminum
-- metal fatigue. After many tiny flexures aluminum will develop cracks and
then fracture. Airplanes deal with this by inspection and component
replacement. Most hams solve this by replacing broken yagi elements when
they notice them lying on the ground. The guys with the copper elements in
their beams do not seem to have this challenge. At some point one should
expect to replace the 'weathered' dipole -- it would not surprise me to
find that would be true of copper or aluminum dipoles.
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