[aprssig] BPSK decoding

[Stephen H. Smith]

scott at opentrac.org wrote:
>> What is an XR2211 going to do when presented with 5 or 10 different 
>> phase-shifting tones simultaneously?
>>     
>
> I'd just assumed it'd have a narrow audio filter on the input (say at 500
> hz) and you'd just tune the dial until the carrier you were after was in the
> passband.
>
>   

That's nowhere near narrow enough!  PSK'ers take for granted the 
"brickwall" selectivity of soundcard DSP processing that can be easily 
under 75 Hz wide, and routinely work within 50 or 100 Hz of each other.  

Further,  since the soundcard DSP schemes are essentially audio 
"transceivers" with an effective bandwidth of 60 Hz or so without the 
equivalent of an RIT control, unless you transmit back to the other 
party on EXACTLY  the same frequency (with 30-50 Hz) they won't copy you.






--

Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      14400    [Think bottom of the 2M band]
Home Page:          http://wa8lmf.com


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