Richard Clark wrote in
:

Understanding what is available at Walt's bench, Pf could be off by
5W or 5%. The 0 reading also suffers the same 5W indeterminacy if it
is measured on the same scale (assuming he is using a Bird wattmeter
with a 100W slug).


Richard,

You can wax on all you like, and try as hard as you like, but if the
source was exactly Zs=50+j0, then the Bird 43 reading for Pf should be
exactly the same.

RF measurement is as you note, fraught with problems, but here is a
relatively simple case. Walt reported that he adjusted the radio on a 50
ohm load, measured Pf and Pr, then substituted another load, no other
changes and reported a 5% reduction in Pf.

I will leave you to arguing wether Walt's observed 5% reduction is of any
value.

Anyone who accepts that a competent measurement technician, competently
using the Bird 43, can reasonably discern a 5% reduction in Pf when it
should be 0% if Zs=50+j0, might question whether that observation
supports the proposition that Zs=50+j0.

Owen