Twin Pbt Operation - Icom IC-7700 Instruction Manual

5
FUNCTIONS FOR RECEIVE

■ Twin PBT operation

Shows filter width, shifting value and condition
• Filter set screen
• PBT operation example
Both controls at
center position
PBT2
IF center frequency
[TWIN-PBT]
PBT-CLR
PBT1
Interference
PBT (Passband Tuning) electronically narrows the IF
passband width by shifting the IF frequency slightly
outside of the IF filter passband to reject interference.
The IC-7700 uses DSP for the PBT function. Moving
both [TWIN-PBT] controls to the same position shifts
the IF both above and below the received frequency.
➥ The LCD shows the passband width and shift fre-
quency graphically.
• PBT indicator above
is in use.
➥ Push and hold
set screen. Current passband width and shift fre-
quency is displayed in the filter set screen.
➥ To set the [TWIN-PBT] controls to the center posi-
tions, push and hold
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
(SSB/CW/RTTY/PSK modes) or 100 Hz (AM mode)
steps.
• [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 the lower
passband edge
PBT2
PBT1
Passband
Desired signal
5-12
switch lights when PBT
PBT-CLR
for 1 sec. to enter the filter
FILTER
for 1 sec.
PBT-CLR
Cutting both lower and
higher passband edges
Interference Desired signal
PBT2
PBT1
Passband
Interference