Posted by Conrad PA5Y on Feb 11, 2020; 4:27pm URL: http://elecraft.85.s1.nabble.com/QRO-KPA500-Failure-tp7658244p7658368.html
Hello Ed, I don't think that you are in class AB with 80% efficiency, in fact you cannot be. Class B can theoretically achieve 78.5% but this is seldom achieved in practice, especially on VHF. Most likely there is a problem with instrumentation.
That's very high efficiency for a solid-state amplifier. Are they
operating in class C? Are there any IMD specs at those output levels?
73,
Scott K9MA
On 2/11/2020 03:18, Edward R Cole wrote:
> I checked the operating specs on two of my QRO amps. Not a KPA500.
>
> 2m-1500w PA using a MRF1K50 in class AB:
> 945w 1398w dc 67% eff 453w disp
> 1511w 1888w dc 80% eff 377w disp
>
> 2m-1200w PA using a MRFE6VP61K25H in class AB:
> 566w 1200w dc 47% eff 634w disp
> 1133w 1542w dc 73% eff 409w disp
>
> less heat dissipated when running full power RF ouput.
> Both are W6PQL amps.
>
> 73, Ed - KL7UW
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