I have used my Directv on my RV for three years. This summer I am in the same spot as last year and my box says I am getting a 78 signal but the soon as I get out of menu it says searching for sat?? I have change cabling, two LNB's and tried three differnt boxes. Can a dish be bad? That is the only thing that is not new. I also get no readings on odd transponders only even ones on the 101,.(It is a sinlgle 18 round dish with one coax). Please help!