[FoxHunt] feedthrough capacitors/EMI filters

[Matthew Francey]

I have an old doppler project that I am resurrecting.  It was based on a
68HC11, and was successfully implemented and used on a few hunts in 1994
and 1995).  At the time, someone gave me a few feedthrough capacitors
in an effort to squelch the compu-shriek from weasling its way from the
microcontroller, into the antenna switcher, and then into the radio.

I'm currently looking for a bunch of feedthrough capacitors, or even
better (based on some grepping's of the net) EMI filters.  They have to
be fairly small (~1cm diameter), and should be low-pass as the signals
are TTL-level digial control lines and vary <1kHz.  While they all have
to conduct DC, most of them don't need to carry signifigant currents,
though at least one will have to take maybe a hundred milliamps (if that)
at +12V: everything needs a power supply.

Can someone recommend a part+source?  Thanks!