Kenwood TS-890S Operation Manual - Page 94

Notch Filter, Noise Reduction

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6 REJECTING INTERFERENCE Notch Filter Noise Reduction Notch filter is capable of suppressing beat interference at the IF level. It can be employed to eliminate beat noise and bring up weak signals or during operation while checking the noise condition. The notch filter can be used in the SSB, CW, FSK, PSK and AM modes. Turning ON/OFF Notch Filter 1 Press [NCH]. Pressing [NCH] each time toggles the notch filter between ON and OFF. • When the notch filter is ON, "NOTCH" is displayed on the screen. • When notch filter is ON, an indicator showing the notch point is displayed in the RX filter passband characteristics inside the filter scope. 2 Turn the [NOTCH] control. Adjust the notch frequency to the point where beat or interference is to be suppressed. • The notch point indicator moves as the notch frequency changes. ● Once the notch point has been set in the CW mode, altering the PITCH and SHIFT values will not change the notch point set for beat suppression. This transceiver comes with two types of noise reduction functions NR1 and NR2 which are effective for reducing continuous noise. When NR1 is used, the optimal method is activated according to the mode in use. Noise Reduction 1 (NR1) • In the SSB, FM and AM modes, noise reduction uses a spectrum subtraction system that places focus on the clarity. • In the CW, FSK and PSK modes, noise reduction employs an LMS filter system that emphasizes the periodic signal. • The noise reduction effect for NR1 can be adjusted. Noise Reduction 2 (NR2) • NR2 employs an SPAC system for all modes which extracts the periodic signal. This system detects periodic signals that are contained in the RX signals, connects the detected periodic signals and plays them as part of the RX audio. For this reason, this method is effective for signals with a single frequency such as CW signals. • NR2 allows configuration to the optimal RX conditions by varying the autocorrelation time for periodic signal detection. • NR2 is most effective in the CW mode. (Use of NR1 is recommended for modes other than CW.) ● Beat signals are also suppressed when NR1 is used in the SSB, FM and AM modes as it suppresses stationary signals. This is a theoretical behavior and not a malfunction. ● When NR2 is set to ON in the SSB mode, the signal clarity may deteriorate, or pulse noise or distortion may occur. This is a theoretical behavior and not a malfunction. ● NR2 cannot be used in the FM mode. Switching the Notch Filter Bandwidth The bandwidth of the stopband for the notch filter can be configured to normal, middle or wide. The middle and wide stopbands are wider than the bandwidth of the normal stopband by two and three times respectively. Press and hold [NCH]. Pressing and holding [NCH] each time switches the bandwidth and changes the display as follows. > (Normal) → > (Middle) → > (Wide) Turning ON/OFF Noise Reduction 1 Press [NR]. Pressing [NR] each time toggles the option in the following sequence: "NR1" → "NR2" → "OFF". • When NR1 or NR2 is ON, > or > is displayed on the screen. .. ● NR1 and NR2 cannot be turned on at the same time. 6-8

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Notch Filter
Notch filter is capable of suppressing beat interference at the IF level.
It can be employed to eliminate beat noise and bring up weak
signals or during operation while checking the noise condition.
The notch filter can be used in the SSB, CW, FSK, PSK and AM modes.
Turning ON/OFF Notch Filter
1
Press [NCH].
Pressing
[NCH]
each time toggles the notch filter between ON
and OFF.
•
When the notch filter is ON, “NOTCH” is displayed on the
screen.
•
When notch filter is ON, an indicator showing the notch point
is displayed in the RX filter passband characteristics inside
the filter scope.
2
Turn the [NOTCH] control.
Adjust the notch frequency to the point where beat or
interference is to be suppressed.
•
The notch point indicator moves as the notch frequency
changes.
●
Once the notch point has been set in the CW mode,
altering the PITCH and SHIFT values will not change the
notch point set for beat suppression.
Switching the Notch Filter Bandwidth
The bandwidth of the stopband for the notch filter can be
configured to normal, middle or wide. The middle and wide
stopbands are wider than the bandwidth of the normal stopband
by two and three times respectively.
Press and hold [NCH].
Pressing and holding
[NCH]
each time switches the bandwidth
and changes the display as follows.
<<
>> (Normal) → <<
>> (Middle) →
<<
>> (Wide)
Noise Reduction
This transceiver comes with two types of noise reduction functions
NR1 and NR2 which are effective for reducing continuous noise.
When NR1 is used, the optimal method is activated according to
the mode in use.
Noise Reduction 1 (NR1)
•
In the SSB, FM and AM modes, noise reduction uses a
spectrum subtraction system that places focus on the clarity.
•
In the CW, FSK and PSK modes, noise reduction employs an
LMS filter system that emphasizes the periodic signal.
•
The noise reduction effect for NR1 can be adjusted.
Noise Reduction 2 (NR2)
•
NR2 employs an SPAC system for all modes which extracts the
periodic signal. This system detects periodic signals that are
contained in the RX signals, connects the detected periodic
signals and plays them as part of the RX audio. For this reason,
this method is effective for signals with a single frequency such
as CW signals.
•
NR2 allows configuration to the optimal RX conditions by
varying the autocorrelation time for periodic signal detection.
•
NR2 is most effective in the CW mode. (Use of NR1 is
recommended for modes other than CW.)
●
Beat signals are also suppressed when NR1 is used in
the SSB, FM and AM modes as it suppresses stationary
signals. This is a theoretical behavior and not a
malfunction.
●
When NR2 is set to ON in the SSB mode, the signal
clarity may deteriorate, or pulse noise or distortion may
occur. This is a theoretical behavior and not a
malfunction.
●
NR2 cannot be used in the FM mode.
Turning ON/OFF Noise Reduction
1
Press [NR].
Pressing
[NR]
each time toggles the option in the following
sequence: “NR1” → “NR2” → “OFF”.
•
When NR1 or NR2 is ON, <<
>> or <<
>> is
displayed on the screen.
●
NR1 and NR2 cannot be turned on at the same time.
6 REJECTING INTERFERENCE
6-8