Don't forget the good old hot wire meters!
As long as you have a good, accurate dummy load, that stays good throughout the
frequency range of interest, all you need to measure RF power is a hot wire
meter. That one can be calibrated easily using low voltage DC, in series with a
digital multimeter. As long as the hot wire is really thin, as they usually are,
skin effect shouldn't be important enough to introduce much error. And skin
effect can be calculated and compensated for, if necessary.
The hot wire can (and should!) be located between two ground planes, so that it
has 50 ohm impedance, and doesn't change the impedance as it moves.
If you can't find such a hot wire meter, they are easy enough to make!
This method ends up being about as accurate as the calorimeter system, but is
easier to make, easier to calibrate, and much, much faster to use! A hot wire
meter typically has a response time well under one second, or a few seconds for
a high current one, while accurate calorimeter measurement requires minutes of
key-down time.
And yes, Roger, Joe and Jim are correct. Bill goofed. To err is human, they
say... :-)
Manfred
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