John,
You are exactly right for bring that factor to attention. Typically
wattmeters use diodes in their detectors, and the response will vary by
frequency and by the power level.
I would trust only something that has been calibrated to NIST traceable
standards. The Telepost LP-100 is one example (and those are used on
many Elecraft test benches).
While 10% is an OK deviation for amateur purposes, two wattmeters each
with 10% accuracy can lead to a 20% error in the final measurements.
It is too easy to jump to conclusions by not considering the potential
errors in measurement accuracy. If you want 5% accuracy in your
conclusions, your measurement tools should be accurate to 0.5% - a far
stretch for wattmeters as we know them.
73,
Don W3FPR
On 6/19/2018 6:25 PM, John Oppenheimer wrote:
Hi Scott,
I wonder how the linearity of the two power meters was evaluated?
Some years ago I checked the K3 and KX3 power meter against two other
meters. They were just within 10%
http://www.kn5l.net/Elecraft/Power.html
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