Owen,

Yes, you are right. The single coupler doesn't isolate the channels. Putting a
10 dbm attenuator between the tee and the coupler changes the 50 Ohm reading. I
think a dual directional coupler is required. I will have to put this on hold
until that problem is solved.

Thanks - Dan

Owen Duffy wrote:
On Sun, 01 Jan 2006 03:25:23 GMT, Owen Duffy wrote:


On Sat, 31 Dec 2005 18:14:04 -0800, dansawyeror
wrote:



why the tee as described, doesn't the 8405A have a tee probe?


Dan, my reason for this question is that you do not seem to have a
load independent sample of the forward wave (if you are referencing
measurements to the A probe).

Ideally you would use a dual directional coupler, otherwise, you need
to isolate the A sample from load impedance variations and reflections
using a largish attenuator for example.

If you are working the ratios out entirely from the B probe, eg B
probe measurements on s/c and unknown load, then the A measurement
becomes unimportant. Note that while this approach can give you enough
info to measure rho and calculate SWR, it will not permit phase
measurements. This approach dumbs the instrument down to a single
channel RF voltmeter.

Owen
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