I am considering Hans' low past filters and matching relay board as I have plenty of room in my box. I have no problem with a simple rotary switch to select, and I'm looking for a simple bolt on solution without butchering the board, either by just connecting to the output, or else disconnecting the existing filters, and feeding the new ones directly from the power amp. I see he also sells BPF modules.
IF you using external filters. disable Kt1-3 and run a coax from power amp to K3. Use external filters.
With trivial wiring and trivial code mods you can use the Raduino to select the filters. Stop at 17M
though as without band pass filters you can't clean up above 20mhz.
For band pass you have to alter (butcher) the board as it has to get before the amp. They are
not designed to handle power. There are other issues that makes that messy so 20mhz and
up give it a pass or build in one filter (alter the board) and use it for only one band.
Most tuners have insufficient selectivity (not their function) to suppress spurs much. Those polyvaricon
are cheap and with both sections in parallel hit about 350pf or so. That and they are more available then
the higher power air gaped as well as smaller. Max power is not much over 10W depending on the
style of the tuner. The trimmers are meaningless.
Its one of those either get in there with a precision knife or its wishful thinking. What I can't see is why
people fear making changes. Its the only way to satisfy the wish/need list.