No guru here either - just a confirmed tinkerer!
The good news about the RS splitter is that there doesn't seem to be such a drastic attenuation factor of 4db or so. With no real equipment, I can't verify it with real specs, but once again the insanely weak VOR station was used for testing in and out of circuit.
This VOR station is so weak that I have to have the squelch open, and my ear pressed to the speaker to hear it with my eyes closed. I can barely make out the "LHS" morse ID. I can almost make it go away just by thinking about it.
With the makeshift bandpass filter inline on the VHF port, and with good direct connections, I can still just barely hear it.
Putting TV-quality gear into place for scanning always makes me cringe, but this might do in a pinch.
Re the adapters: I was actually happy to witness firsthand just how poor they were when testing this thing out. It would be hard to really tell with extremely strong signals, and in fact the wide-open preamp on the Pro-164 (mislabeled "ATT" button) on 800 mhz trunking actually helped prove it. I'm saving this for another thread....