On Thu, 30 Jun 2005 06:47:07 GMT, Owen wrote:


The only other inference you can make from one instrument with regard
to the other will be if one of the instruments shows zero reflected
power, then you know the VSWR that the other instrument will indicate.

As Cecil has hinted ), you can
also infer that the impedance at the point where you have two sets of
Pf,Pr readings is that the impedance (R, X) is one of two values
(which can be visualised as the intersection of two circles on a Smith
Chart), one only in the cases VSWR1*VSWR2=Zo1/Zo2 (or the inverse)
(which can be visualised as the kissing of two circles on a Smith
Chart). The latter includes the case above where one or other
instruments indicates VSWR=1, but is more exact because one of the
circles is infinitely small.

These cases are not reliably of practical value, the conversion of
error in the measurements made with each instrument, into error in the
estimated R and X at the point could be huge.

So, I "correct" my statement to "The only other inference that you can
reasonably reliably make from one instrument with regard to the other
will be if one of the instruments shows zero reflected power, then you
know R and X, and the VSWR that the other instrument should indicate.

Thanks Cecil.

Owen
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