[AMPS] IMD & Phase noise

[Peter Chadwick]

Thread title changed to reflect reality!

Jon says:

	>I would expect my FT-840 to have better receiver IM performance 

One factor that is not appreciated widely is that the intermodulation
limited 
dynamic range in a receiver (some call it 'Spurious Free Dynamic range' - it
is
 2/3 of the difference in dB between the bandwidth dependent noise floor in 
dBm and the input third order intercept point in dBm) and the phase noise 
limited dynamic range need to be about equal. Having one greatly exceeding 
the other is a waste of effort. This also means that a practical limitation
on how 
much IMD performance a receiver needs is how much phase noise exists from 
other transmissions on the band. I've heard a number of FT1000s on the band 
that weren't too good - this on CW. So that could be a limit. Fortunately,
tube 
PAs aren't generally too bad for wideband noise, but the wideband noise from

some solid state drivers leaves a lot to be desired.


73

Peter G3RZP



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