Don Wilhelm wrote:
I find that with a good 50 ohm dummy load and an 100 MHz oscilloscope
with a 10X probe (probe rated for 100 MHz), I can calibrate the KPA100
wattmeter to less than 5% accuracy on bands below 20 meters - at higher
frequencies, the 'scope and probe rolloff will indicate lower than
expected results.
Be careful if you use this method! I learned the hard way (destroyed
THREE probes) that the voltage rating for scope probes goes down as
frequency goes up. There is a little piece of paper that comes with the
probes; look at it, compute the voltage across your dummy load at the
power levels that you will be testing (100 watts is about 70.7 volts),
and make sure that the probe can handle it at the frequency of interest.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco
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