I 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.

Another option 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 1Mhz osc.

The schematic can be downloaded by clicking this link (opens PDF file)