Beat Cancellers - Kenwood TS-990S In-Depth Manual

06 DSP

Beat Cancellers

While the auto notch filter processes signals in the IF stage, the beat cancellers (BC) suppress the beat in the AF stage.
In comparison with the auto notch filter, which is effective only for a single beat signal, the beat cancellers are effective
for several beat signals.
In the beat cancellers, the adaptive filter technique of the same type as that for the NR1 line enhancer method is used.
This cancels a periodic signal like a beat signal contained in the entered signal by feeding the differences of the signal
between the output signals from and the input signal to the line enhancer.
The graphs below show how a beat canceller cancels beat signals.
There are two types of beat cancellers: 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 BCs are for beat signal
elimination and do not work in CW, FSK, and PSK modes.
If there is beat interference stronger than the desired signal in an adjacent frequency, the beat signal may cause the
AGC to activate. The beat cancellers process signals in the AF stage so that the beat signals will be eliminated; hence,
the beat cancellers receive the desired signal, keeping it suppressed, without highlighting the desired signal. In that
case, the auto notch or manual notch filter that works in the IF stage is more effective.
46
BC OFF
Frequency (Hz)
BC ON
Elimination of Multiple Beats
Frequency (Hz)
Fig. 73 Effect of a Beat Canceller