The issue you have with any discrete modem like this, if using a PLL, is
false triggering of the output while the PLL is trying to acquire the signal.
That complicates the issue substantially. As you close the BW down to get
rid of noise you lose modem baud rate, classic tradeoff in speed vs noise
immunity in many EE fields.
If you ever looked inside a Hayes modem even they did not do this discrete,
although its pretty "partsy"
As info only I stumbled across this, fascinating how this was done. -
Access Google Sites with a personal Google account or Google Workspace account (for business use).
sites.google.com
Good luck, should be fun.
Regards, Dana.