Lloyd Verhage wrote:

> I have a PIC 16Cxx that I'm using for an amateur radio application
> I'm using a 20Mhz crystal, but it appears the PIC is not functioning.

  The crystal requires loading caps, just as it does in a radio.  These
should be present on the board and specified in the circuit diagram.  I
find it highly improbable that these would be absent in a production kit
though if you were building from an article such an oversight could
occur ...

> I wonder if I should go to a ceramic oscillator instead.

  That's a rather implausible suggestion, even if you *could* find a
20MHz resonator, it would likely be even more difficult to coax into
operation and you would lose your baudrate accuracy.

>  Is there crystal "problems" that I should be aware of?

  Sure are, but if you have done any RF work you should know them -
as Dave mentioned, parallel resonant, fundamental mode, load capacity to
match the caps used (allowing for the capacity of the PIC), and you
would recall the trick of listening for the oscillator on your general
coverage RX!

> The application is called a MIM Module.

  Ringing isn't practical from here, and articles may be a bit tedious
but which mag was it in?  If it was on a Web site, that would be more
like it.  Web sites are easy to arrange, *plenty* of volunteer hosts
(such as myself!) for Amateur Radio.

Care to elaborate on a MIM module?  The concept of using a MCU for a TNC
is certainly not new.
--
  Cheers,
        Paul B.