[Amps] Power meter calibration

[Martin Sole]

Apologies if this is not really amps but lots of wise old owls on here
methinks.

I have built a power meter, to measure the power out of my amplifier,
hopefully that keeps this on track. I have a question concerning
calibration. Ignoring diode non-linearity's and other spurious
imperfections, what sort of law should the meter scale be calibrated
according to. I have the WB6BLD meter scale drawing program for which
the included 200 watt scale uses a linear exponent of 0.55. Having tried
this it just doesn't seem right. What's the formula?

73
Martin, HS0ZED