I have an oval 18x20 3 LNB dish on the roof and two different receivers. When I check the signal strength on the receivers I get different results. On the RCA 430 receiver the signal is about equal between the 101 and the 110/119 at about 94. On the RCA DTC100 the 101 signal is always around 95 but the 110/119 signal is always lower at around 60-75. How do I know which receiver is giving the accurate reading? Is the 60-75 reading too low for reliable signal reception?