To be clean, tetrode and pentode amplifiers should be tuned to the tube
mfg's specified screen current, when peaked with the Tune-C. Less screen
current =s heavier loading =s less imd. Zero grid current is cleaner.
>> tube and the regulated supplies. I question whether the splatter Paul had
>> was related to the amplifier at all. I suspect that the amplifier was
>> overdriven by the driver and flat-topped. If ALC was used, this would be
>> almost certainty.
>Recall that the 2000A is a true auto-tune amp and it performs this function
>remarkably well...even better than the Alpha 87A in my opinion. If the amp
>is misadjusted during tune-up, it's the amp's fault (or the designer's), not
>mine. Nevertheless, the amp can be manually tuned as well with similar
>results. I never use ALC and my exciters exhibit zero power overshoot; the
>exciter's internal ALC circuits are all working properly. I monitor my
>output with a scope through a Bird ThruLine sample 100% of the time on SSB.
>I am painfully aware of the effect of flat-topping and excessive overdrive.
>The splattering did in fact worsen when lower drive levels were prevalent at
>the amp's input. This was not an overdrive issue. What I am saying is in
>that particular amplifier, there was an intermod-related problem which does
>not manifest from either of my Alphas. I have three exciters here from
>which to use. The problem was apparent with all exciters when used with the
>ACOM 2000A. Was the problem limited to that particular amp? Perhaps it
>was. Perhaps it wasn't. Correctly measuring 3rd-order intermod is no
>trivial matter and is far beyond the capabilities of my station equipment.
>My solution was simple: I sold the ACOM and kept the Alphas.
- R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K,