The most important thing to know about preamplifiers is that they do not pull in signal or extend the range of TV antenna. If we do not have a good strong enough signal at the antenna a preamplifier will not help. The function of a preamplifier is to amplify the TV signal received by the antenna and strengthen the signal so that you can over come your cable loss, splitter loss, etc that is between the antenna and your TV set. The gain of the preamplifier determines the amount of loss that you can over come. As you increase the gain of the preamplifier your input levels decrease. What this means one has to be careful when there are local channels and distant channels involved because you can overload the higher gain preamplifiers with too much incoming signals from the close stations and cause problems on the distant channels.
The best way to choose a preamplifier is to choose the one that has enough gain to over come the loss of your antenna system or at least the cable loss from the antenna to your splitter location.
Average losses are:
-6.0dB / 100’ of RG6/U cable
-3.5 - 4.0dB for a 2 way splitter
-7.0 - 8.0dB for a 4 way splitterExample you have 50 feet of cable from the antenna to the splitter equals -3.0dB loss
You have a 4 way splitter you have -7.0dB loss
You have 50 feet of cable from the splitter to the TV set on the longest line from the splitter equals -3.0db loss
Total: -13.0db loss
Preamplifier size would be the AP-8700 for UHF/VHF or the AP-4700 for UHF only since these preamplifiers have 17-19dB gain.Suggested preamplifier choices would be 0-20 miles no preamplifier. For 20-30 miles HDP-269, 25-40 miles AP-8700, AP4700, AP-2870, AP-3700 and for 35+ miles the AP-8275, AP-8780, AP-4800, AP-8800.