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Page 49 FT-950 O
PERATING
M
ANUAL
I
NTERFERENCE
R
EJECTION
WIDTH
(
IF DSP B
ANDWIDTH
)
T
UNING
(
SSB/CW/RTTY/PKT M
ODES
)
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 signal
fidelity when interference on the band is low.
1. Press the [ WIDTH
] button. The LED inside the
[
WIDTH
] button glows orange. The [
SELECT
] knob
functions as the WITDH knob. The current bandwidth
appears in the WIDTH indicator on the display.
2. Rotate the [ SELECT
] knob to the left or right to re-
duce the interference.
3. Press the [ CLEAR
] button to set the bandwidth to de-
fault.
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 inter-
ference has appeared both on the high and low sides
of the desired signal. Press the [
WIDTH
] button
then rotate the [ SELECT
(
WIDTH
)] knob, the in-
terference from one side can be eliminated (Figure
“
B
”). Next, press the [
SHIFT
] button and rotate
the [ SELECT
(
SHIFT
)] knob to re-positioning the
passband (Figure “ C ”), the interference on the op-
posite side can be removed, without re-introduc-
ing the interference previously eliminated in Fig-
ure “
B ”.
The default bandwidths, and total bandwidth ad-
justment range, will vary according to the operat-
ing mode:
SSB Mode: 1.8 kHz ~ 3.0 kHz (default: 2.4 kHz).
CW Mode: 500 Hz ~ 2.4 kHz (default: 2.4 kHz)
RTTY/PKT Modes: 500 Hz ~ 2.4 kHz (default:
500 Hz)
[WIDTH] Button
[SELECT] Knob
WIDTH Indicator
[CLEAR] Button
A B C
A
DVICE
:
The IF Bandwidth will be memorized independently on
each VFO stack of VFO-A and VFO-B.
Referring to Figure “ B ”, you can see the default
bandwidth on the SSB mode by pressing the
[
CLEAR
] button.
By rotating the [ SELECT
(
WIDTH
)] knob to the
left, the bandwidth will narrow (see Figure “ A ”,
while rotation of the [ SELECT
(
WIDTH
)] knob to
the right, as depicted in Figure “ C ”, will increase
the bandwidth.
A
DVICE
:
For best interference reduction, the WIDTH and
SHIFT features are the primary tools you should
use. After narrowing the bandwidth (WIDTH) and/
or adjusting the center of the passband (SHIFT).
The Contour control may then yield additional sig-
nal-enhancement benefits on the net residual band-
width. Even more, the IF NOTCH Filter (described
later) may also be used, in conjunction with these
filter systems, to significant advantage.
A B C
IF
BANDWIDTH
IF
BANDWIDTH
IF
BANDWIDTH
Desired Signal Desired Signal Desired Signal
QRM
QRM QRM QRM
QRM QRM
IF
BANDWIDTH
IF
BANDWIDTH
IF
BANDWIDTH