Batboard

I am in the process of repairing a repeater set for the 136-150 mhz spectrum. The duplexers that are in place are Motorola Model # TU312H. They seem to be bandpass filters as they don't provide notch when swept. Currently the isolation between the two frequencies (1.5 MHz apart) are about 45 db. When I measure the return loss, it only reads about -5db (about an SWR of 9:1).
Can anyone provide me with some information on these (a digital manual would be nice) so I can reaccomplish the harness and realign them?

MARS

"a digital manual would be nice"
___________________________

Digital manual? I can't find any kind of manual! We're talking really old here. Like 30+ years. Most of my archives from that era have decomposed by now!

What I do have says that the TU312H is a VHF bandpass cavity covering 132-174 MHz. There were four different optional coupling loop kits: 0.5/1.0/1.5/2.0/3.0 db insertion loss with corresponding loaded Q of 650/1250/1750/2100/3100.

Your cavities may have been field configured as a duplexer or it is possible that Motorola had a duplex harness for them. I don't remember ever seeing the TU312 used as anything but a bandpass filter.

Tuning is just a matter of turning the knobs to move the rod up and down thereby adjusting the resonant frequency.