If Width & Shift Control; If Notch Filter - Yaesu FT-1000MP Operating Manual

Operation
When QRM is present on both sides of the
tuned station, first adjust the
SHIFT
control just to
the point where the interference from one side is
eliminated, and then rotate the
WIDTH
control in
the opposite direction to eliminate interference
from the other side. The optimum settings of these
controls depend on the relative signal strengths of
the desired station and the QRM, and requires
practice.
SHlFTMllDTH Tuning Steps
Rotating the
SHIFT
or
WIDTH
control tunes the
IF passband using default 10-Hz steps. If
desired, you can change to 20-Hz steps,
which offers a faster response when turning
the control knob. See menu selection1 -2 to set
the default steps as desired.
Notch Filter
After tuning in a desired signal and adjusting
the IF bandwidth and shift, if heterodyne interfer-
ence such as from a carrier or CW signal occurs,
activate the IF notch filter by pressing the NOTCH
button and slowly adjusting the inner control with
the same name to null the heterodyne. Note that
if the interfering carrier is more than about t-1.2
kHz
away from the center of the passband, the
notch filter may be unable to null it. In this case,
switch the notch filter off, and readjust the IF
bandwidth and shift so that the undesired carrier
is outside of the passband.
Q
(Hete
NOTCH
- >
NB NOTCH
- >
NB
NOTCH
NOTCH Action
Advice on QRM Reduction
Use the
BANDWIDTH
buttons and then the
SHIFT
and
WIDTH
controls t~ suppress the
interference. Their use varies somewhat from
mode to mode. In general, however, you will
want to press the
LOCK
button beneath the
tuning knob before adjusting the
SHI F T
and
WIDTH
controls, as accidentally retuning
would invalidate your settings (particularly in
narrow-bandwidth modes).
When you are ready to retune to a new
frequency, press
LOCK
again to release it, and
return the
SHIFT
and
WIDTH
controls to their
default positions (center detent). The
WIDTH
control can also be turned counter-clockwise
to reduce the IF bandwidth more gradually,
and then the
SHIFT
control can be turned left
or right from center to shift the center
frequency lower or higher, as depicted in the
For digital modes, the wider bandwidth
selections are fine for tuning around, but the
500 or 250 (Hz) bandwidths will generally give
the best copy with narrow shifts. If you have
the RTTY and PKT menu selections set to
match your TNClterminal unit (see page 55),
you should not need to adjust the
SHIFT
control at all, and the
WIDTH
control should
only be adjusted with a great deal of care (to
avoid losing the contact). See the section on
For 300-baud packet, use
500
(Hz) bandwidth
and keep the
WIDTH
control centered; the
SHIFT
control may require fine tuning either
side of center for optimum copy of weak
signals. Experiment with the
SHIFT
setting on
a busy packet channel, and then note the
optimum setting for all future HF packet
operation (it will be the same unless you
replace your TNC or recalibrate the input
Note
-
except during extreme Q R M
conditions, the
WIDTH
and
SHIFT
controls
should be left in their center (detent) positions
when tuning the receiver to a new frequency.
This will provide the best fidelity and easiest
page 34