It's probably worth mentioning, that all of the lossy situations I
encountered in EZNEC also caused fairly significant modification of the
feedpoint impedance. I suppose it makes sense; this is a necessary
condition for coupling significant power into the rod, and could
potentially give you extra information beyond just measuring the
temperature rise.


What I plan to do is to measure SWR in three conditions, i.e. the rod alone (no parallel copper wire), rod + wire connected at the two extremes, and rod insulated from the radiating wire. The measured SWR variation in the three cases will give me an indication of the feedpoint impedance variation, which, as you say, can constitute an indicator of ohmic losses presence.

By means of a tuner, I will be able to deliver the desired amount of RF power into the antenna for quite a wide feedpoint impedance range (and SWR). I can use a short run of coaxial cable to feed the antenna, so the cable loss variation for different SWR values will be negligible on 20 meters.

73

Tony I0JX