I suspect its the grid bias and grid current monitoring system in the Emtron amplifiers that is the real cause of the problem. There is no reliable indicator of grid current on these amps. When these amps splatter they must be drawing grid current that is only detected when there is an excessive amount of grid current. I have monitored a DX2SP into a dummy load using a real time spectrum analyzer. The resulting splatter in real time is like square wave on either side of the signal as you get the peak splatter. If this was a normal normal metered homebrew amplifier you would see this fault immediately on the grid I meter.
If you do a real dynamic IMD test using a voice signal you will hear this leading edge splatter burst thats indicative of grid current draw. What other conclusion can you come to when its a given that drawing grid current on SSB will cause splatter. While I have done 2 tone measurements on one of these amplifiers and the resulting 2 tone numbers are respectable, the dynamic on air performance is terrible. Who do you blame the amplifier manufacturer or the radio, manufacturer?
All my homebrew Tetrode amplifiers have always a sensitive op-amp driven grid current I meter. Any hint of grid current flowing could be detected. How do you do this on a tetrode control that uses a LED display with coarse poor current monitoring hysteresis and one one that has no active grid current display?
In the hands of the average ham these poorly designed tetrode amplifiers are nuisance on the bands. Try tuning the websdr.org SDR receivers in Europe and listen on 40 and 20 meters you can easily spot these tetrode amplifiers they that obvious on the waterfall display. Its very rare to hear splattering triode amplifiers, its always a joker with tetrode amp that causes the damage. When something as simple a single LED grid current indicator could help these operators tune these amps, one has to wonder why they leave such critical monitoring off the front panel and only give an alarm when there is really excessive current drawn. Its then no surprise that just about every commercial tetrode amplifiers causes excessive splatter.
You making life difficult following the attenuator path. This would be a good idea for those Aussie Emtron amplifiers that produce a lot of splatter from ALC and power overshoot.
Do they reallly do that? A friend of mine has several of them. I always wondered how well designed any tetrode amp really is.
Overshoot or dynamic regulation problems do not show in a two-tone test. Which do you think it has?