[Elecraft] Experience with KXPA100

[Hans J Rasmusen OZ7BQ]

Hello,

My KXPA100 ser.nr. 00822 has now been on the air for several months and produced several hundred QSO's. The performance however, is mixed.
The output power varies from one band to another with the output set on the KX3 to 110 Watts and using the KXPA100 utility for meetering and a dummy load. The antenna tuner is in manual and SWR indicated to be between 1:1 and 1:1.1 from 160 M to 10 M.

The best band is 20 M, where the KXPA100 will produce 112 Watts out with 5.5 Watts driving power and an indicated power dissipation of 62 Watts.
The worst band is 40 M where the KXPA 100 only will produce 83 watts out with 2.8 Watts drive and an indicated power dissipation of 92 Watts.
On 80 M the KXPA100 utility shows a power dissipation of 118 Watts and an output power of 89 Watts.
Except on 20 M no band produce more than 90 to 95 Watts output.


I am surprised by the big variation in efficiency. Almost twice the loss on 80 M compared to 20 M. Besides there seems to be plenty of drive power, so why less than full power on most bands?

Has anyone else observed similar variations?

73 OZ7BQ, Hans Jørgen (Joe)