Some satellites have transponder with 54 MHz, 72 MHz or other bandwidths. These as well as standard 36 MHz wide channels can be used to transmit two television signals in a half-transponder format. The bandwidth is divided into two 27 or 36 MHz regions with the video carriers are centered in either the upper or lower region. receive half-transponder formats, a receiver must be capable of both tuning to a continuously variable center frequency and employing bandwidth narrowing filters. For example, to receive 23 MHz half- transponder broadcasts, the tuner is centered on either the upper or lower half of the transponder frequency and then bandpass filters reduce the detected bandwidth from the normal 28 to 32 MHz to a more narrow 23 MHz. Adjustable bandpass filters can be interfaced to the IF loopthrough connections available on the rear panels of most satellite receivers. This loopthrough in many brands is connected via a short jumper cable when not in use.rrowing the bandwidth improves the input C/N ratio with an expense in picture quality that ranges from hardly detectable to unacceptable. The trade-off is between a loss of color fidelity and picture detail for reduction in impulse noise, sparklies, and increased clarity. Receiver bandwidths as low as 12 MHz may be acceptable in some cases. At bandwidths below 10 MHz the audio subcarriers fall above the upper frequency cutoff of the high frequency bandpass filters. In this extreme case, a separate receiver would have to be used to recover the audio information. At bandwidths below 7 MHz color subcarriers are also truncated and only black/white video would be visible. The reduced frequency response in the receiver causes an attenuation of both the sync pulses and the high frequency portions of the video signal itself. Some picture tearing might be observed and as noise begins to overpower the signal sparklies again begin to appear.