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
is comparing my (copper) Nott screwdriver with my (aluminum) Tarheel
screwdriver or my (aluminum) Hi-Q mobile antenna on 20 meters.
Mounted on my Durango, at resonance the Nott's impedance is 9 ohms,
while
the Tarheel is 20 ohms and the (smaller tube) Hi-Q is 30 ohms; Measured
with
the same whip in all cases.
This is a case of a short antenna.
The difference is significant and easily measured.
73
H.
NQ5H