Yaesu FT-991A Operating Manual page 4

General Description
DNR ( Digital Noise Reduction ) by DSP
digital processing ( see page 56. )
The incorporated digital noise reduction circuit may be
set to the optimal working point by varying the 15 step
parameters according to the noise type.
NOTCH feature that significantly
eliminates unwanted beat signals; and
DNF feature that instantly attenuates
multiple beat signals ( see page 56. )
When interfering beat signals are present in the receiver
passband, the IF NOTCH feature can significantly elimi-
nate a part of the passband and remove the beat signal.
Moreover, the function is equipped with an Automatic
Tracking System DNF ( Digital Notch Filter ) that can
be engaged by DSP when there are multiple interfering
signals, even when the frequency is changing.
Reliable High-output Final Amplifier
Stage
In the HF/50MHz frequency range, a pair of RD100HHF1
transistors in a push-pull RF amplifier arrangement deliv-
ers 100 watts of low-distortion, high-quality transmitter
power. The final amplifier for the 144 MHz/430 MHz
bands uses the high-output RDH70HUF2 device, provid-
ing ample output power of 50 watts.
Microphone Amplifier that includes
Parametric Equalizer ( see page 65. )
The microphone amplifier equalizer feature is equipped
with a three-stage parametric equalizer that can alter the
Low, Mid, and High frequencies of the audio separately;
this feature permits the bandwidth and gain for each part of
the audio spectrum to be precisely adjusted independently.
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Real-Time Spectrum Scope and Multi-Color
Waterfall Display ( see page 42. )
The spectrum scope function provides a visual display of
the strength and distribution of signals across the band in
real time. The Waterfall Display Mode portrays color dif-
ferentiation between strong and weak signals.
High speed antenna tuner ( see page 63. )
The transceiver is equipped with the relay switching high
speed digital tuner which supports 1.8 MHz to 50 MHz.
The large 100-channel tuning data memory allows im-
mediate recall of the optimum matching conditions for
previously tuned frequencies.
Optional Five Channel Message Memory
( voice memory ) ( see page 70. )
You can use the 5 channel voice memory function which
is useful for operating in contests, etc. This voice memory
enables recording of up to 20 seconds of audio for each
message you want to send.
Custom selection ( C.S ) button ( see page 39. )
This feature lets you select any Menu item for one-touch
access via the C.S button.
F T-991 Operating Manual