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I have been reading the posts on power output and note that most have more power on the lower bands than the higher.? I am getting maximum, well not so maximum, out on 20 meters.about 8 watts dropping to 4 on 40 mtrs and 3 on 80 mtrs.? RV1 and the bias resistors are set to the extreme left, counter clockwise for maximum output.? One of the PAs runs quite hot, while the other is warm. I am tempted to replace the PAs.? Wonder if anyone has some ideas on this?? Thanks Jeff? PS: my wattmeter has been checked with known power outputs and is quite accurate at 100 watts and ten watts so I am inclined to trust it.? SWR is low using a manual atu.

Have you tried the PA bias current adjustment listed here??

Tom, wb6b

Thanks for jumping in Tom.? Yes as I noted above the bias resistors are adjusted for maximum output.? I felt pretty good about 8 watts on 20 but not too happy with the 4 on 40m.? :(.? Any other suggestions would be appreciated.? What is interesting is that maximum power is at the low limit of the resistors which seem to suggest adding a resistor in parallel would give me more power out.
cheers Jeff

Jeff,
>>Thanks for jumping in Tom.? Yes as I noted above the bias resistors are adjusted for maximum output.? I felt pretty good about 8 watts on 20 but not too happy with the 4 on 40m.? :(.? Any other suggestions would be appreciated.? What is interesting is that maximum power is at the low limit of the resistors which seem to suggest adding a resistor in parallel would give me more power out.<<

I recently worked on one that did good power on 80 and 20 but low on 40...
The problem was the PI network for 40 had the wrong coils.? ?Two had
only 8 turns when it should have been more like 14.? Fixing that
produced more power than 20M.

Allison

Jeff,

Also check the emitter of Q90 to see if a .01uf or a 470pf or 220PF is there.

There was a change to lower the value from .01 to 470 pf to level the output
power so 80M wasn't 15-20W when 20m is maybe 8.

Some have tried it with low bands working very poorly.? I tried it on a friends
radio ad the effect was poor power over all.? for his it needed to be 1000pf.

Allison