connection to Off-the-air terminal on my HR20-700C

I have a puzzle.  I have an antenna with rotator on my roof.  I want to use it to receive channels that Directv doesn't provide.

I connected the 75 ohm coax to the OTA connection on my HR20.  No TV signals except from our local university station' principal and sub-channel  that is about a mile from my home. No other channels--either primary or sub-channels--from stations within 50 miles were received.

BUT, I moved the coax from the OTA input on the HR20 to the FM input on my SONY DE-845 AM/FM receiver and, where I had heard on a hiss before, I now receive excellent FM stereo reception!! 

I'm not sure if this is relevant or not, but I have two signal splitters I thought about using to take the rooftop antenna signals to my FM receiver and the

HR20's OTA input at the same time.   I have 2, 2-way splitters, a 5 - 900 MHz one and a 5 - 2150 one.  There is also an 8 - way splitter that is part of

the standard Directv installation. It covers 5 - 2150 MHz. None of the connections on that splitter are connected to the OTA input on the HR20.

That's all I can think of that's possibly relevant.

Thanks again for your help.

P.S. The zip code below refers to where I live.  Champaign-Urbana are 61801 and 61820