[Elecraft] Elecraft K2 Power Readout Discrepancy

[steve.lawrence@itwfeg.com]

Another measurement alternative... use your oscilloscope!

Assuming you're feeding a 50 ohm dummy load, measure the peak-to-peak 
voltage (Vp) of the (hopefully) output sine wave while transmitting "key 
down". 

Power = (Vp * Vp) / 400

This depends on a calibrated vertical scale on your 'scope.  Also, take 
into account any multiplication factor of your 'scope probe:  X1, X10, 
etc. when calibrating the vertical scale and reading the voltage.

This method falls apart if the output wave is complex (not a sine wave), 
or the dummy load is not 50 ohms.  The underlying formula is derived from:

        Power in watts = Vrms * Vrms / resistance across which the voltage 
is measured

and
        Vrms = 0.707 * (V peak-to-peak / 2)

Steve
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