[Elecraft] Which meter to trust?

[Paul Braiman]

Putting my brand new KPA-500 through its paces and I’m noticing a significant difference between the peak power displayed on the amp, and the peak power displayed on a Telepost LP-700 station monitor.  With the amp peaking at 500 watts, the LP-700 will often show peaks in the 600+ watt range. The trapezoidal display on the LP-700 does not show any non-linearity during such operations.

Is this then simply a difference in how the power is metered?

As always, your collective wisdom is both appreciated and valued.

Paul, W2PIR

Dare Mighty Things.
-Jet Propulsion Laboratory