Here's some of the gear I've built or rebuilt over the years.
Built
TNC2C
I built around 25 of these :)
Rebuilt
AP 780
I rebuilt several of both the VHF and UHF versions. At one point I held a repeater licence (145.787,5, if I recall correctly) and used a pair of APs (VHF+UHF) as a repeater from VHF to UHF — no filter needed, oddly enough, since they were simply connected together.