[AMPS] Receiver tests in the past........

[Peter Chadwick]

Tom says:

>What is the intercept at 2 kHz spacing (narrow),  and 
>20 kHz spacing (wide)? How do they compare to tests 
>at 100 kHz? 

Tom, go wash your mouth out! You're not supposed to ask awkward questions like
that! Generally, the close in (2kHz) IMD specs are set by in channel IMD
requirements, where AGC is supposed to prevent overload. (Ripple from the
demodulated envelope on the AGC line is another matter, and often screws things
up - one answer is a phase compenstaed active LPF with a cut off around 50 -
100Hz in the AGC path) These awkward people who use CW and are thus interested
in real IMD from signals out of passband are generally ignored - not enough
commercial demand. This is where there are advantages in older rigs with an IF
around 8MHz or whatever, where the first crystal filter is a narrow CW filter.
But those filters aren't as good on IMD as a lower frequency filter, of course.
Resurrect 3395, the Heathkit IF?

But to repeat - the close in phase noise has got to be good enough to allow the
good IMD performance to be used.

73

Peter G3RZP


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