A satellite transponder is a circuit on a satellite that receives, modulates, amplifies and re-transmits an uplinked signal. There can be 20 -30 transponders on a single satellite. Typical bandwidths of a transponder are 27, 33, 36, 54 and 72 MHz.
Carrier signals are received by the satellite at a very low power levels because of the long distance traversed by the radiowaves. The satellite needs to significantly boost the power level of these signals before they are re-transmitted back to the earth to ensure that they are detectable by an earth-based receiver. This is achieved using a set of high power amplifiers on-board the satellite, where each amplifier operates over a defined frequency range.
The combination of equipment required to amplify carriers within a given frequency range is commonly referred to as a transponder. This equipment includes the high power amplifier (HPA) itself, as well as filters at the input and at the output of the amplifier to isolate the desired carriers from the carriers processed by other transponders. The frequency extent over which the amplifier operates is usually referred to as the transponder's usable bandwidth.
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For example, CCTV-4 has Freq 11780, hor, SR 20765. Once i used these info to setup Transponder, then run search, I should get only CCTV-4 or with others if they are available?
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To see what is on that transponder, go to
http://www.lyngsat.com/g3c.shtml