On Sun, 17 Aug 1997 22:06:17 +0100 "Brian K. Short"
<shortckt@primenet.com> writes:
>This question is likely too simple, but I'll ask
>anyway: What is the "fool-proof" way to tune an
>amplifier?
The very first place I would start is with the manual. If that is of no
help then a call to Command and ask them to mail or FAX you tuning
instructions.
Since this is a current production amp I should think that they would be
helpful. It also covers you if there is a warranty.
Once you get the basics down and comfortable then you can get a bit
experimental. I have found that good 3CX800's peak their output well
before the grid current limits. Typically 10ma per tube. Watch the
wattmeter and slowly adjust the load control a bit at a time and use the
Tune control to peak the output. Vary the load control one way or another
until the output is peaked. Then increase the Load (less capacitance)
until the power just starts to drop. This will be the point of best IMD
performance. If you do not know which way is more or less capacitance,
open up and look. Dont go by the dial scale since that changes from
company to company. ALWAYS peak the power with the Tune control; you
should be able to come up, thru and down, etc to make sure there is a
true peak.
NEVER use either control to reduce power; do that with the exciter only.
Many hams make a tuning chart once the values are known and simply dial
in the correct numbers when changing bands. Others place tape over the
dial scales and mark bands. Use whatever works; the less time spent
tuning the longer the tube life.
73....Carl KM1H
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