Passband tuning

 
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überarbeitet am 21.10.2010

In the shortwave band, between the channels of broadcasting stations there are often very small distances, the broadcast bands are crowded with a 5 kHz channel spacing. In case, there is a powerful transmitter using the next 5 kHz channel, You will hear a very annoying 5 kHz heterodyne noise.

Particularly in the receiption of a weak signal transmitting on a frequecy very near to a "powerhouse" station or even a co-challel transmitter, major problems arise.

With aid of the Passband Tuning, You can shift the transmission curve of the IF-filter relatively to the carrier signal. So in case there is an interfering signal on 9868 kHz and want to hear the transmitter on 9865 kHz, You can shift the IF-filter transmission curve slightly downward to fade out the interfering signal.

So particularly a hardly perceivable station can be made audible with the so-called ECSS reception. In single-sideband mode, You can switch the receiver to the sideband with less interference, but interfering carriers will generate a most annoying heterodyne tone.

Particularly in ECSS reception mode, shifting the IF - transmission curve by careful operating the passband tuning knob will often the give the crucial tiny bit to make a signal readable.