Twin Pbt Operation - Icom IC-756PROIII Instruction Manual

■ Twin PBT operation

General PBT (Passband Tuning) function electronically
narrows the IF passband width by shifting the IF fre-
quency to slightly outside of the IF filter passband to
reject interference. This transceiver uses the DSP cir-
cuit for the PBT function. Moving both [TWIN PBT]
controls to the same position shifts the IF.
➥ The LCD shows the passband width and shift fre-
quency graphically.
➥ Push [FILTER] for 1 sec. to enter the filter set
mode. Current passband width and shift frequency
is displayed in the filter set mode screen.
➥ To set the [TWIN PBT] controls to the center posi-
tions, push [PBT CLR] for 1 sec.
The variable range depends on the passband width
and mode. The edge of the variable range is half of the
passband width, and PBT is adjustable in 25 or 50 Hz
steps. These controls function as an IF shift control
while in AM mode and when the RTTY filter is turned
ON. Only the inner control may function in this case.
IF shift is adjustable in 20/40 Hz steps in RTTY (RTTY
filter is turned ON) or 150/300/500 Hz steps in AM.
PBT OPERATION EXAMPLE
Both controls at
center position
TWIN PBT
IF center frequency
Shows filter width, shifting value and condition
• [TWIN PBT] should normally be set to the center posi-
tions (PBT setting is cleared) when there is no interfer-
ence.
• When PBT is used, the audio tone may be changed.
• Not available for FM mode.
• While rotating [TWIN PBT], noise may occur. This comes
from the DSP unit and does not indicate an equipment
malfunction.
Cutting a lower
passband
TWIN PBT
Passband
Interference Desired signal
FUNCTION FOR RECEIVE
[FILTER]
ANT ANT
BW BW 2.4k 2.4k 0
SFT SFT
1
TX T X VFO VFO U S B U S B
FIL2 FIL2
qr.qot.pp
METER METER
Po Po
USB USB
1 14.100.00 14.100.00
P.AMP P.AMP
1
VFO VFO USB USB
FIL2 FIL2
qr.wpt.pp
ATT ATT
OFF OFF
USB USB
1 14.100.00 14.100.00
Cutting both higher and
lower passbands
TWIN PBT
Interference
Desired signal
5
[TWIN PBT]
5
[PBT CLR]
qw:pp
12:00
Passband
Interference
60