On Tue, 06 Dec 2005 07:45:36 -0700, Wes Stewart
wrote:

On Mon, 05 Dec 2005 21:18:33 -0800, dansawyeror
wrote:

I would like to know if the follow technique will work to measure resonance of
an antenna. I know have a working HP 8405a. It has been a struggle to repair it
and to align it, however it now appears to be working.

My plan is to connect a bi-directional coupler to the 8405a. The coupler will be
terminated in a 50 Ohm terminator. The phase will be read for this
configuration. The next step is to replace the 50 Ohm terminator with a direct
connection to an unknown antenna. I will then change the frequency until the
phase angle matchs the 50 Ohm phase angle.

Does this make sense?

Sort of, but not exactly. As I described in another thread, the
pitfall is the fact that the phase lengths of the coupler are
different. You could set the phase offset to zero at frequency X but
when you change to frequency Y, there is a built-in error.

I should have added that you don't do this with a 50 ohm load, but a
short circuit instead. You want a big reflection with a known phase
for a calibration standard.