I'm looking at picking up the TYT TH-9800, which is a Quad-Band FM radio on 10m/6m/2m and 440 (I'm lucky enough to have some 6m and 10m repeaters in the area). I know there exists quad band antennas for this radio, however not only are they a bit of a compromise on all bands, but they all use UHF connectors for the mount connection - which I am very against. So I began my search for a triplexer so I could use 3 separate antennas, this should be more efficient than the one quad band, allow me to swap out the HF antennas as needed, have a much larger selection of antennas, and allow me to switch the HF side (via antenna switch) to another radio while also not sacrificing 6m/2m/440.
I started searching online, however no one that I've found makes such a triplexer - the best off the shelf solution I can do is 2 diplexers; one VHF/UHF and 6m/HF diplexer with a second 6m and HF diplexer. I'm not the biggest fan of that solution. So I started looking into the DIY/Homebrew approach, which also was unfruitful. I found plenty of resources for making diplexers, but very little for triplexers.
So here's the TL;DR: does anyone know the proper formulas to make triplexers and/or know of any good resources for building?
Below is what the end state would look like, also with an AnyTone 6666 for 10m AM/SSB/CW. I should also note this will be a mobile solution, thus only focusing on 10m for now.
TYT 9800 AT6666 -------- ------ | | | | ----------- | ___ |triplexer| | 2m/440 \|/ ----------- | | | | | | |-------| | | ---------- | ___ | |----| sw box |----| ___ \|/ 6m | ---------- \|/ HF/10m | | | | |-----------------| |-----------------|