Lea wrote:

> I need it to detect CTCSS tones from a given radio channel, so it must
> have less than 2 Hz of error, it is possible to do it with a F84??.

  If you have a quiet signal for a whole second such that the CTCSS is
your only modulation, you could probably count zero-crossings OK.

  Otherwise, it means using DSP techniques and for that a PIC won't do.
Interestingly, Microchip *used to* make DSP chips but has dropped these!
--
  Cheers,
        Paul B.