In article , Michael Coslo
wrote:

My knowledge of the matter is at the noobie level, but given that loss
eventually gets you reading only the Z0 of the cable, it's what I
suspected. I hadn't thought about a big mismatch between the cable and
antenna, so there's another data point.


- 73 de Mike N3LI -

Hello, and I ran into this issue years ago when trying to measure high (
10 or 20) VSWR loads (in this case out-of-band shipboard HF antenna
feedpoint impedance) connected via a length of transmission line.
Accurate determination of load resistance is difficult to ascertain under
these conditions. A 1953 AIEE (a progenitor of the IEEE) paper by W.W.
Macalpine, "Computation of Impedance and Efficiency of Transmission Lines
with High Sanding Wave Ratio" describes the problem.

I was, however, able to obtain accurate results when I included the small
imaginary part (frequency dependent) of the characteristic impedance that
is present in a low-loss line. Outside the high VSWR load issue the
imaginary part can be ignored. Sincerely, and 73s from N4GGO,

John Wood (Code 5550) e-mail:
Naval Research Laboratory
4555 Overlook Avenue, SW
Washington, DC 20375-5337