[rabbit73]

One other thought comes to mind. When I was troubleshooting cable TV distribution systems that had old lengths of RG59 connected with F-81 adapters, sometimes the high (UHF) channels were OK, but the low (VHF)channels were snowy (analog).

What was usually wrong was a bad connection at the F81 adapter. The connection LOOKED OK, but either the center conductor or the shield wasn't making contact. This created a gap that had a small capacitance which would allow the UHF signals to pass with little loss, but the low channels were attenuated because of the high reactance at low frequencies.

So I replaced the F-81 adapters or just ran a new length of RG6, and everybody was happy.