Yaesu MARK-V FT-100MP, Руководство по эксплуатации, Страница: 49 / 120

Page 47
O
PERATING
M
ANUAL
O
PERATION
D
EALING WITH
I
NTERFERENCE
WIDTH C
ONTROL
We just saw that specific IF filters can be selected
to limit the receive bandpass to a pre-set width (essen-
tially the total width of the installed filter). In a crowded
band, you ideally want to narrow the bandwidth just to
the point where the unwanted signal is attenuated while
still retaining enough bandpass to recover the desired
station. In real-life band conditions, however, this ideal
bandwidth is often somewhere “in-between” the sev-
eral selectable filter bandwidths.
The WIDTH control can be used in
all modes except FM to continuously
narrow or broaden the bandpass skirt
(within the limit of the selected filter) for
the best skirt shaping and optimum
cutoff and interference rejection during
each QRM situation. Unlike older types of width con-
trols that adjust both sides of the filter slope at the same
time, the
MARK-V FT-1000MP
Field
’s WIDTH control
narrows the passband from either the upper or lower
side (see illustration below). Thus, you only narrow the
side of the bandpass where the QRM is located.
The center detent on the outer WIDTH control pro-
vides maximum bandwidth, which is equal to the se-
lectivity of the filter used with the operating mode. Clock-
wise rotation moves the upper skirt of the IF passband
lower in frequency, and counter-clockwise rotation
moves the lower skirt upwards. If a QRM condition
occurs after tuning in a station, slowly rotate the con-
trol in the direction where the interference is reduced
while the station is still workable. As you rotate the con-
trol you will hear the audio response change as the
passband is narrowed. If the QRM is very close, the
amount of bandwidth reduction necessary to cut the
QRM may leave the desired station’s audio unrecov-
erable, or it may not be possible to entirely eliminate
the QRM.
When the QRM is all above or all below the desired
signal it is usually only necessary to rotate the WIDTH
control either to the left or right to cut the interference
from the receiver passband. The
SHIFT control (cov-
ered next) will also work for this, but may introduce
interference from the other side of the signal.
When you have activated the IDBT feature by press-
ing the [ IDBT
] button on the
Shuttle Jog , the EDSP
(Contour) filter’s passband width reduces according to
the
WITDH knob setting. That is, the IF bandwidth and
the EDSP bandwidth will be matched, according to the
setting of the
WIDTH control knob’s position. The IDBT
feature is available in the USB and LSB modes.
WIDTH Action Using WIDTH control to reduce QRM