●Beat cancel
Beat cancel (BC), as its name implies, is designed to cancel unpleasant beat interference. Like NR1, it uses adaptive filter technology, tracking a beat and canceling it by shaping. It is very similar to a band elimination filter. Even if there are multiple beats, BC can track and cancel them all.
However, since BC operates at the AF stage, should powerful beat interference be experienced during DX operations, even though beat cancel works properly, by then the AGC has already attenuated both the interference and the target signal. To combat this sort of beat, IF shift is used to eliminate the interference.
Figs. 18 and 19 show how BC cancels beat signals, as monitored by an FFT analyzer. You can see how the three beats present in the signal are removed with almost surgical precision.
Fig. 18: BC OFF
Fig. 19: BC ON
There are two methods available for beat cancellation: BC1 and BC2. These have been tuned so that BC1 is effective against weak or continuous beat interference, while BC2 cancels intermittent beat such as a CW Morse signal. (Note that since BC is designed to remove the beat, and does not function in CW mode.)
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