[Amps] AL-811 low power

[W5WRL]

Folks

I have an Ameritron AL-811. I get very close to 550 watts on 160m but as I
move higher in frequency 40m to 10m the power output falls off. Output on 10
is about 250w. One fellow suggested that I change the tubes. I replaced the
original 811s with 572s and the result is basically the same. I am driving
the amp with a Yaesu 847. 

Any suggestions on how I can get full power out of the amp on the higher
frequencies?

Best Regards,


Bill Lawless - W5WRL
Frequency Coordinator - Zone 5, West Texas 
http://www.txvhffm.org/default.asp
ARRL WTX Assistant Section Manager