Strange happenings with my Directv

I use my receivers from home when we go camping. I have two H-21 200 receivers. I had an experience the other morning that I can't explain. Each receiver has a home run coax from the LNB to the receiver. Last week we had been set up all week with Directv working fine. Friday morning when we were getting ready to leave, I disconnected the bedroom receiver. When I went to the living area, I turned on the other receiver and got "771-no signal message" on all three sats. (I use a 3 LNB dish when camping and have a slimline 5 LNB dish at home). I assumed that a wire had gotten disconnected or someone had bumped the dish. I checked both and there were no problems.

My first thought was possibly my LNB had went bad. I went back and reconnected the bedroom receiver and the living room receiver started working. When I would disconnect the antenna wire from the bedroom receiver the living room receiver would give me the 771 message. If I unplugged the bedroom receiver from AC it had no effect on the living room receiver. The message only happened when I disconnected the antenna wire. Anyone have any suggestions on what maybe causing this. I tried the same thing when I got home and did not have this problem.