Here is some info I found somewhere:
---> "What is a Transponder? On the
installation screen I've noticed that my transponder number changes.
Some numbers have different signal strength than others. Today transponder 05 I can 99% signal strength. Yet 13 for example has 86%. Why is that?
A transponder is the transmitter/antenna on the satellite. Typically a satellite will have around 32 transponders, although the owner of the satellite may not be licensed for all 32. Each transponder operates at a specific frequency, and can carry from 1 to 8 channels of TV and audio. Even and Odd transponders operate with opposite circular polarization to prevent adjacent "channel" interference. When you go to the installation screen, the transponder shown will be the one carrying the program you were last watching. You can not choose to have your program come across a different transponder. Several of the transponders on some of the satellites are operating at double power, and this accounts for some of the difference you are seeing. Other transponders might have different effective strengths at different geographical locations within their footprint. But there's not much point in being concerned, almost any strength over 50 gives you a perfect picture. Higher strengths just give you some margin against rain and snow fade."
I saw a really detailed explanation of transponder power too. Even more juicy than this one -- I'll see if I can find it...
kat