You don't say your modulation mode. (CW - FM or SSB whatever that is)
I'm no expert, but you are achieving 50% efficiency, that doesn't
sound bad to me for 6 meters, to get more power out you need more
power in.
I would double the plate Voltage. That increases efficiency.
--
Ron KA4INM
## Mode had nothing to do with it. Increasing B+ does not increase eff.
Increasing B+ to the max typ results in a higher plate load Z..which is the last
thing you want on a 6m amp...esp one with low eff. .
## I would not run the L4B with oem zero bias either. The resulting idle
current
is way too high. 220-230 ma. You can knock the idle current down to 100 ma,
when on high B+ position, with just 8 x diodes in the CT. Which will also
result in
40 ma when on low B+ position. And nobody will complain about IMD in either
position.
## I installed a miniature SPDT-center off toggle switch on the lower rear
apron
on my L4Bs. Then I can get 3 stages of bias. Center off gets all 8 diodes.
The other
2 positions will get 2 more, tapped at 3 and 7 diodes. The eimac 3-500z is a
lower mu
tube MU=130 vs the MU-200 of a 3-400Z and other brands of 3-500zs. The
higher the
MU, the lower the idle current. If you really want to go crazy, install a
miniature rotary switch,
and tap every diode. 4-400s will idle at a lower idle current.
## IF the tubes are good, he should be able to get 800 ma of plate current,
but will require
100-120 watts of drive.
## His is now a 6M monoband amp, with everything optimized for 6m. I would
check the slug
if a bird or CD wattmeter used. Dont trust the drake internal wattmeter..esp
on 6m.
Jim VE7RF
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