I played with software based PL and touch tone decoding at lot and
> while I got a couple of them to work they were NEVER anywhere close
> to as good as a Motorola radio.
Pretty sure you were trying to beat an RC low-pass filter, op-amp
limiter, and hardware counter-timer. The 3870 has event timing built
in, with a base input to the timer unit of 1.8 MHz, and various dividers
and prescalers.
De
