Thanks to all that replied to the tuning question. It seems that there is no
definitive answer. I guess to protect the amplifier it is best to re-tune
when ever the frequency is changed more than a few Khz.
Darryl - K5WAS
> 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
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