A few weeks ago I found this at a local get-together taking place at a repeater site. At this meeting they sell (often donated) stuff for the benefit of running the repeater.
This year I found an unknown set of band filters in a box, I suspected that it would be a kind of triplexer, and toady I got my NanoVNA out, and yes it is.
The connector at the far side is the common one. On the near side we see two very recognizable labels, VHF and UHF. I did not know what the third one was, but measuring I found.
Testing from the common port:
TOS: Low pass filter, flat up to 117MHz, then a small dip of up to 5dB, then a 3dB cut-off at about 134MHz.
VHF: Flat from 135MHz - 270MHz, but some feed through up to about 315MHz. Good attenuation below 100MHz and above 400MHz.
UHF: High pass filter with 3dB cut-off around 336MHz. Attenuation on 1300MHz was about 3dB.
Residual attenuation:
Below 100MHz: Practically flat with <0.5dB attenuation
VHF: <0.5dB at 144MHz
UHF: <0.5dB at 435MHz
Attenuation between band ports was more than 22dB at frequencies where I would expect to transmit, so that is insufficient for a transceiver triplexer. For a VHF-UHF monitoring receiver system, this would work nicely.
I got a few of the filters for experiments. I had decided that the shielded boxes, at least, could be useful for other RF projects, and there were some decent looking (SMD) capacitors for VHF and UHF. There were quite a bit of these filters, so I might have got a few more. If they are there next year I may get some of them again.
Yes, finally I got to use my RF test equipment, now it is time to get some construction done.
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