Wes Stewart wrote:

the minute you say "SO-239", all bets are off.

I did some SPICE modelling of an ideal bridge (with resistive detector)
and came to the same conclusions....that the higher-than-50
ohm-impedance UHF connector and adapter may be a limiting factor in the
performance on a good SMA- or N- connectored load. It has virtually no
effect on the difference in level between open and short terminations
though.

I have a link to a must read paper at:

http://www.k6mhe.com/n7ws/

Note No. 11.

Make particular note of the part, "The Curse of Adapters."

Thanks...the original Wiltron app note has been a favourite of mine for
many years, but have never seen the updated version.

73,
Steve VE3SMA