[BC] Harmonic measurements

[Dan Dickey]

> We have seen a fair number of instances with interference at the 9th 
> harmonic, sometimes caused, rather than mitigated, by real time adaptive 
> correction.

I think this comment is worth a considered reply. Please don't take this as 
a comment on the specific situation because I have no direct knowledge of 
the cases reported here. But I do think it is highly unlikely that adaptive 
correction can be the true culprit as surmised by the poster. There are no 
adaptive correction schemes that can generate 9th or 10th harmonic energy. 
They simply do not have the required sample rate. However, by using adaptive 
correction it is possible to push an amplifier into significantly higher 
compression than without adaptive correction. Therefore, I submit that if 
turning on adaptive correction causes increased harmonics that the true 
source of the harmonics is one or more amplifiers in the chain that are 
being driven too hard into compression. In this case, the obvious solutions 
are to get a bigger amplifier capable of making the required peak power or 
get a better harmonic filter.

If this is a tube transmitter then careful checks of the neutralization are 
in order because as one drives the PA harder poor neutralization can incite 
oscillations that only exist for very short periods of maximum drive. But 
here again the culprit is not adaptive correction itself.

In any case, whether the adaptive correction is real time or non-real time 
probably makes no difference.

Best regards,
Dan