[Amps] A tale of two IMs What happens?

[Roger]

No one has touched the question on how reducing power without returning 
affects IM I now have another one.

Given that most of todays transceivers have an IM or roughly -35db "so 
I've been told", and we put a amp behind it that also has an IM of 
-35db, what is the resultant IM?  What if the amp has an IM of -55db?
Do they add, subtract, or go with the lowest number?  IOW it is the amps 
job to "faithfully" reproduce the input signal, but that really only 
happens when running class A, if the user is lucky.

Intuitively, "I would think" that the two figures would add, but if that 
were the case the amp with -35db and the exciter with -35db would have a 
pretty ratty signal. OTOH in the case of the -55db amp behind the -35 db 
exciter does the amp "clean up" the exciter signal? Doesn't seem likely.

It'd be interesting to see the IM figures for today's exciters, (and 
amplifiers) rather than than adds that just say "Provides amazingly low IM".

I also see I need a refresher on working with logs.<:-))

73

Roger (K8RI)