I have a Dish 500 with a DP Dual LNBF, and a single DP311 receiver. I am able to view programs from Sat 119, but not 110 as the signal goes in and out constantly. I have had this configuration for almost 4 years now with no problems. A tech told me the dish is aimed perfectly. I had branches cut from a tree across the street to ensure no interference, but it did nothing to change the status. Could my LNBF be bad? What can I do to test it? Thanx.