Beat Canceler - Kenwood TS-890S In-Depth Manual

07 DSP

Beat Canceler

While the notch filter processes signals in the IF stage, the beat canceler suppresses the beat in the AF stage. Beat
canceler is effective when there are multiple beat signals.
The beat canceler employs an adaptive filter technique which is of the same type as that for the NR1 line enhancer
method. It cancels periodic signals such as a beat signal contained in the input signal by feeding the differences
between the output signals from and the input signal to the line enhancer.
The graphs below show how multiple beat signals are canceled by a beat canceler.
There are two types of beat cancelers: BC1 and BC2. BC1 is tuned to be effective against weak or continuous beat
signals. BC2 is tuned to be effective against intermittent beat signals such as Morse signals. The Beat Canceler is for
beat signal elimination and do not work in the CW, FSK and PSK modes.
If there is beat interference that is stronger than the desired signal in an adjacent frequency during signal reception, IF-
AGC may be activated by the beat signal. The beat cancelers process audio signals after demodulation, and thus while
it is able to eliminate beat signals, it does not highlight the suppressed signals. For such cases, it is more effective to use
the notch filter, which functions in the stage preceding IF-AGC.
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Fig. 50 Effect of Beat Canceler Elimination of Multiple Beats
Frequency (Hz)
Elimination of Multiple Beats
Frequency (Hz)