Kenwood TS-990S Operation Manual - Page 153

Audio Peak Filter While In Fsk Mode, Noise Blanker, Fsk/psk/rev], Apf/sel], The Main Band, Nb2].

Page 153 highlights

REJECTING INTERFERENCE 6 AUDIO PEAK FILTER WHILE IN FSK MODE While the transceiver receives a signal in FSK mode, the audio peak filter allows the mark frequency and space frequency each to have a peak, thus reducing the occurrence of garbled characters and increasing the readability of the signal. The audio peak filter supports not only high-tone signals with a mark frequency of 2125 Hz but also low-tone signals with a mark frequency of 1275 Hz. {page 5-49}  .

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REJECTING INTERFERENCE 6
6-9
Index
Contents
AUDIO PEAK FILTER WHILE IN FSK MODE
While the transceiver receives a signal in FSK mode,
the audio peak filter allows the mark frequency and
space frequency each to have a peak, thus reducing the
occurrence of garbled characters and increasing the
readability of the signal. The audio peak filter supports not
only high-tone signals with a mark frequency of 2125 Hz
but also low-tone signals with a mark frequency of 1275
Hz.
{page 5-49}
[FSK/PSK/REV]
[APF/SEL] (S)
[APF/SEL] (M)
1
Press
[FSK/PSK/REV]
to select FSK mode.
2
Press
[APF/SEL]
(M) or
[APF/SEL]
(S) to enable the
audio peak filter for the selected band.
While the audio peak filter is active, the "APF/SEL" (M) or
"APF/SEL" (S) LED lights green.
Note:
If the shift width for RTTY mode exceeds 170 Hz, the audio peak
filter for the selected band cannot be enabled
The audio filter for use in FSK mode does not process the signal to
be demodulated internally.
NOISE BLANKER
The noise blanker suppresses “crunching” pulse noise.
The transceiver incorporates two types of noise blanker;
Noise Blanker 1 (NB1) for analog signal processing, and
Noise Blanker 2 (NB2) for digital signal processing at the
IF stage by means of a DSP. You can select either NB1 or
NB2 as desired depending on the noise status. Both can
be enabled at the same time.
Note:
In FM mode, you cannot use Noise Blanker.
Noise is suppressed more effectively if a larger value is configured,
but there may be some effect on the received signal.
[F1]~[F7]
[ESC]
[NB2]
[MULTI/CH]
[NB1]
[NB1/SEL]
[NB2/SEL]
[NB2] [NB1]
■ Activating or deactivating the Noise Blankers for
the main band
1
Press
[NB1]
or
[NB2]
.
Noise Blanker 1 or 2 for the main band is activated or
deactivated.
While Noise Blanker 1 or Noise Blanker 2 is active, "NB1"
or "NB2" appears on the upper left side of the main screen.
While both Noise Blanker 1 and Noise Blanker 2 are active,
"NB1 2" appears on the upper left side of the main screen.
Pressing the key again deactivates Noise Blanker for the
main band.
2
Press and hold
[NB2].
Pressing and holding
[NB2]
for the main band displays
the NB2 function configuration screen on the main screen.
Pressing
[TYPE]
(F6) in this state allows you to switch
between “TYPE A” (conventional method) and “TYPE
B” (newly added method). If “TYPE B” is configured, the
parameters for “WIDTH” (width for blanking the pulse width)
and “DEPTH” (depth for blanking the pulse width) can be
configured to 20 steps.
Pressing and holding
[NB2
] again or pressing
[ESC]
exits
the NB2 function configuration screen.
“TYPE A” detects and suppresses pulse noise according to
the signal amplitude. The target signal is not blanked so it
is effective for receiving signals buried in noise pulses.
“TYPE B” detects and blanks pulse noise according to
the rate of amplitude change. As with NB1 (noise blanker
that employs analog processing at the IF stage), TYPE B
blanks the pulse noise together with target signal. However,
the “WIDTH” and “DEPTH” can be configured according to
the receiving condition.
“TYPE B” does not support the sub band due to memory
limit for the DSP.
Depending on the receiving condition, the combined use of
“TYPE A” or
“TYPE B” together with NB1 may be effective.
And by widening the passband width of the roofing filter,
NB2 may function more effectively.
{page 6-3}