Yaesu FT-991 Operating Manual page 53

Width (iF dSp b
Using IF SHIFT and WIDTH Together
The IF SHIFT and Variable IF WIDTH features
together form a very effective interference-fight-
ing filtering system.
For example, in Figure "A", you can see how in-
terference has appeared both on the high and low
sides of the desired signal. Touch [ WIDTH ] on
the LCD, the interference from one side can be
eliminated (Figure "B"). Next, rotate the MULTI
knob to re-position the passband (Figure "C"),
the interference on the opposite side can be re-
moved, without re-introducing the interference
previously eliminated in Figure "B".
A
Desired Signal Desired Signal
QRM
QRM QRM
IF BANDWIDTH IF BANDWIDTH
FT-991 O
peraTing
i
nterference
) t
AndWidth
B C
Desired Signal
QRM
QRM
QRM
IF BANDWIDTH
M
anual
(SSb/cW/rtty/dAtA M
uning
A :
dvice
The WIDTH and SHIFT features are the pri-
mary tools to use for best interference reduction.
After narrowing the bandwidth (WIDTH) and/
or adjusting the center of the passband (SHIFT),
the Contour control may then yield additional
signal-enhancement benefits on the net residual
bandwidth. Even more, the IF NOTCH Filter
(described later) may also be used, in conjunc-
tion with these filter systems, to significant ad-
vantage.
r
eJection
)
odeS
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