[1000mp] PCT III Not Legal USA? - Sound Card Digital/Ritty Modes

[Tom Rauch]

> Current DSP-based TNC's provide mode-specific configurations in
> firmware, as do S/W TNC's operating with soundcards, and some use
> detectors with performance superior to the limiter/discriminator
> approach, such as linear matched filters.

Even the very best digital filters are limited to dynamic ranges in 
the 50dB range or less. While they handle multiple signals that are 
not extremely different in level OK, they fall apart when some 
signals are significantly louder that others..especially when there 
are multiple signals.

The reliance on digital filtering, even very good specialized digital 
filtering, is why PSK and MFSK people complain so loudly and so often 
about "high power stations". The problem is the  receiving systems 
can't copy weak signals in the presence of multiple signals of 
reasonable strengths.

Best to have the option of using some reasonable amount of IF 
selectivity, should a high power 100-watt station with a good antenna 
happen to come on nearby.73, Tom W8JI
W8JI@contesting.com