[digitalradio] Re: Technical Question: FDMDV / QPSK in PSK31

[cesco12342000]

Modem description from Peter G3PLX (the modem author):

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The modem is based on a "raised cosine" shaped tone filter response which 
has the property of zero ISI and zero adjacent tone interference with no 
sidelobes. Half the channel filter is in the tx and the other half in the 
rx, so it's often called "root raised cosine" because the channel filters 
at each end have a response which is the square-root of the complete 
filter.  
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