Page 52
FT-
991
Operating Manual
Interference Rejection
WIDTH
(
IF DSP Bandwidth
)
Tuning
(
SSB/CW/RTTY/DATA Modes
)
The IF WIDTH tuning system allows you to vary the width of the DSP IF passband, to reduce or eliminate interference.
Moreover, the bandwidth may actually be
expanded
from its default setting, should you wish to enhance incoming sig-
nal fidelity when interference on the band is low.
1. Press the
F
(M-LIST)
button to display the function
menu list. Touch the [
WIDTH
] icon to activate this
function and cause the
MULTI
knob to function as
the WIDTH adjustment knob.
MULTI Knob
F(M-LIST) Button
WIDTH indicator
WIDTH level indicator
2. Rotate the
MULTI
knob counter-clockwise to narrow
the bandwidth and reduce interference.
Referring to Figure “
B
”, you can see the default
bandwidth of the SSB mode.
By rotating the
MULTI
knob to the left, the band-
width will narrow (see Figure “
A
”), while rota-
tion of the
MULTI
knob to the right, will increase
the bandwidth as depicted in Figure “
C
”.
The default bandwidths, and total bandwidth ad-
justment range, will vary according to the operat-
ing mode:
SSB Mode: 1.8 kHz - 3.2 kHz (default: 2.4 kHz).
CW Mode: 500 Hz - 3 kHz (default: 2.4 kHz)
RTTY/DATA (LSB, USB) Modes: 500 Hz - 3
kHz (default: 500 Hz)
AM Mode: Fixed at 9 kHz
FM/DATA-FM/C4FM Modes: Fixed at 16 kHz
A
B
C
IF BANDWIDTH
IF BANDWIDTH
IF BANDWIDTH
MULTI
MULTI
MULTI
Advice:
To increase the bandwidth, rotate the knob clock-
wise.
Rotate the
MULTI
knob to display the bandwidth
of the IF filter below the
[
WIDTH
] indicator (Re-
fer to the instruction below).
For reference, the level indicator on the TFT dis-
play shows the bandwidth.
