I am looking for some advice on purchasing an amplifier for satellite signal for one of my customers. I have a Dish 500 installed with 3 301's. The problem is I have about 400ft of cable (each line) from dish to receiver. I run the check switch and all I can get is odd transponders on both 119 and 110. I have ruled out the LNB and all receivers for the problem. So could I please have some advice as to which amplifier to buy. Thanks much in advance.