I have a PIC 16Cxx that I'm using for an amateur radio application
[1].  I'm using a 20Mhz crystal, but it appears the PIC is not
functioning.  I wonder if I should go to a ceramic oscillator
instead.  Is there crystal "problems" that I should be aware of?

Thanks,
Lloyd

[1]  The application is called a MIM Module.  Its a TNC for amateur
radios (basically a modem for radio).  Its designed by Dr Will
Clement.