[Elecraft] QRO - KPA500 Failure

[Andy Durbin]

"I understand that efficiency decreases as one derates from the maximum of 1500W output.It surprises me that the power dissipated would peak at half power output or 750 Watts."

I have no test data for the KPA1500 and will not speculate on the shape of the PA dissipation curves.  All I have is data for one KPA500.  For that one KPA500, and under the conditions tested,  it's clear that PA dissipation is greater at half power than at full power.

It would be easy to get a pair of data points for the KPA1500.

Connect the amplifier to a known good 50 ohm load.
Drive the amplifier to steady state 1500 W output
Record PA current and voltage
Drive the amplifier to steady state 750 W output
Record the PA current and voltage

Repeat on multiple bands if desired and report the results here.

73,
Andy, k3wyc