There are several variables here other than the conductivity of the
primary metal. Again, what you're seeing is not "the difference between
copper and aluminum" as initially stated, but a number of other factors
-- diameter, length, coating, and alloy --, combined.

If the DC conductivity of two materials differs by a factor of two,
their RF conductivity differs only by a factor of the square root of
two, or about 1.4. This is because the skin depth is greater in the less
conductive material, which partially offsets the conductivity
difference. The relatively small difference in DC conductivity between
pure copper and aluminum is further reduced by this effect, so you'll
very seldom be able to see any difference.

Roy Lewallen, W7EL

H. Adam Stevens, NQ5H wrote:
Roy
I looked up the numbers.
The Nott is 2" diameter bare copper 3' long.
The Tarheel is 2" diameter painted aluminum 4' long.
The Hi-Q is 1" diameter powder-coated aluminum 3' long.
I used the same whip for all measurements.
If we take the conductivity of copper to be 100, aluminum is then 60 and
aluminum alloys are as low as 30.
That's a factor of two between the Nott and Tarheel and the reduced surface
area of the Hi-Q explains the additional resistance there. Considering the
difference in surface area and resistivity among the antennas, the measured
impedances seem quite reasonable to me.
73
H.
NQ5H


"Roy Lewallen" wrote in message
...

That's much, much more difference than can be explained by the different
conductivities of the metals. Either some very resistive alloys are
involved, or there are differences between the antennas other than the
type of metal.

Roy Lewallen, W7EL

H. Adam Stevens, NQ5H wrote:

One place where I can clearly see the difference between copper and

aluminum
. . .