Dear Daryl,
The question of how far can you QSY without tuning is a mixed bag of
information.
Essentially, the point of resonance is at a particular frequency, and
shifting
that frequency throws the amplifier off resonance.
The point of resonance may have a broad occurrence whereby a "flat top"
to the peak power is observed.
Every amplifier is different. Six Commanders, side-by-side, will exhibit
six different curves for resonance. The choice of tank components
will also affect tuning bandwidth. For instance, in the dual 3CPX1500A7
amplifier just completed here, the Plate Tuning vacuum capacitor was
originally
a 12~500pF and that had a broad bandwidth, but lousy 160 meter
performance.
A 7 - 1,000pF cap was installed instead, and it has great top band
performance
but razor sharp tuning.
Why not do a bench test with a good dummy load and a wattmeter? Make a
chart,
and tune up in your favorite hangout area, and while the amp is keyed at
minimum
drive, QSY 500 Hz., and see if you need to re-tune. Change bands, change
frequencies
and chart the results. You will see the amplifier has different
requirements in different places,
but your chart will remind you in the heat of the contest that Yes, you
need to peak, or
No, go ahead and get 'er done!
Sincerely,
Hal Mandel
W4HBM
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|