We have a set of these in service at a sight and I personally don’t care for them. When I went to return them to our new frequency, they had a really low insertion loss of like 0.10dB and a weird bandpass shape. I took them apart and used very fine emery cloth and cleaned the tuning rods and fingers and then wiped them down with denatured alcohol, finally applied a thin coat of Triflow oil and reassembled it. Only then it actually tuned up to the spec sheet and just barely. They work but I just don’t care for them.?
I’ve got a set of these 6 cavity VHF model of the mentioned duplexer and they were a PITA to tune and get working, and they still probably aren’t tuned to the best of their ability.
Jared Smudde