"H. Adam Stevens, NQ5H" wrote in message ...

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.

A 2" diameter bare copper rod or cylinder at 14MHz, 3' long, should
have an RF resistance about 6 milliohms. The worst aluminum alloy
you're likely to see should be about 12 milliohms; 24 for the 1"
diameter. What am I missing here? How does that translate to a
change from 9 ohms to 20 ohms to 30 ohms at the feedpoint? If the
cause is resistance heating of the copper or aluminum tube, what's
doing the impedance transformation, and how is it so efficient? That
much loss should result in measurable temperature rise in the tube (or
wherever the loss is), at 100-W power levels.

Or perhaps my image of what you're measuring is all out of whack.
Same loading coil in each case? I'd kind of expect the loading coil
to be the main loss mechanism, if all the connections are tight.

Puzzled and seeking enlightenment,
Tom