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Old March 11th 06, 09:31 PM posted to rec.radio.shortwave
Telamon
 
Posts: n/a
Default New LongWire Antenna - What Type Wire?

In article ,
James Douglas wrote:

As my existing fence is falling down and I have saved the 3K to replace
it it's also time for a new antenna. What type of wire would be best?
My existing antenna is around the fence about 8' in the area and the
area is shaped like [ with the long side running North/South.


Considering
1. Price
2. Conductor performance.
3. Insulation longevity

1. Discount warehouse home improvement hardware stores.

2. If you were to hang it up on insulators where the wire would have to
support its own weight I would give a different answer but you indicate
that the new fence will support it so best and cheapest would be solid
copper and large diameter. The RF current at medium wave and short wave
has a tendency to travel on the exterior of the wire so the resistance
to RF current flow is much higher than it is for DC, which tends to use
more of the wires cross-sectional area. This Rf effect is know as the
skin effect so since the RF current only travels in the "skin" of the
wire a larger diameter for a long stretch provides a helpful improvement
in performance.

How big to go in diameter? Well bigger means larger circumference.
According to this web page calculator 15 MHz has a rounded skin depth of
0.000662 inch. That's a pretty thin layer so a step in wire size must
mean a significant drop in RF resistance per foot. I would go with the
largest wire size available for a reasonable price. Something in the #6,
8 or 10 size would be a good bet.

3. Must withstand the sun and weather effects. Teflon coated is the same
color of the fence would be a good choice.

--
Telamon
Ventura, California