35
DSP 07
NB2 affects the noise that cannot be processed by the analog circuit; however, there may be a case where it cannot
suppress the noise depending on the strength of the desired signal and characteristics of the pulse noise.
In such a case, by using noise reduction together, the receiving status may be improved.
Also, use of a narrow roofing filter bandwidth may change the noise component that deteriorates its effect. Employing
NB1, NB2 and noise reduction flexibly according to the circumstances enables you to handle a wider variety of
situations.
●
Notch Filter
The notch filter allows you to change the center frequency of the notch by turning the
[NOTCH]
knob.
The notch filter has an attenuation of 60 dB or higher at the notch center frequency. The diagram below shows how a
minute signal suppressed by the IF-AGC operation can be highlighted when the beat is eliminated by the notch filter.
Time (s)
Time (s)
Amplitude (dB)
Amplitude (dB)
Audio signals suppressed by the
IF-AGC can be highlighted when
the beat is eliminated.
Fig. 41 Effect of the Notch Filter
Pressing and holding down
[NCH]
key switches the notch filter bandwidth in the sequence of “Normal (Narrow)”,
“Medium” followed by “Wide”. “Normal” is effective for a single beat frequency.
In the case of interference by a signal in the SSB mode or when there is difficulty in hearing the desired signal due to its
partial elimination after adjustment of the IF filter, selecting “Wide” for the notch filter may be more effective.
Amplitude (dB)
Frequency (Hz)
Fig. 42 Notch Filter Characteristics (Reference)
