In the days before the cushman ce50tg, I used an FM10CS with a bearcat scanner to set pass and reject on BpBr duplexers. Be sure and use a 50 Ohm 10 db attenuator on each port to normalize mismatch between the duplexer port and the antenna port on the bearcat, or the generator and the duplexer. Also terminate the unused port. This is not a highly precise way to do the job, but in a pinch this will work. Of course you don't just routinely go out ant tweak cavity duplexers, this is only when there is a reason.
Best luck, Steve NU5D
