originally built this unit for use at the 1999 region II ARDF
championships in Portland Oregon. Old CD4000 series CMOS logic
(which may now be getting harder to obtain) was used because it
could operate directly off of the battery with out a regulator.
if you are willing to experiment would be to replace the whole
osc circuit with a CMOS clock osc. The Digikey catalog has a large
selection of them. If you did that you would also need a regulator
to generate +5 or 3.3 depending on the clock you find.
This would make it a more modern design as you would be doing
away with an old part and all of the components that make up the
can be downloaded by clicking this link
(opens PDF file)