Icom IC-7700 - Manual (Page 100)

5-12
■
Twin PBT operation
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 for both high and low frequencies.
➥
The LCD shows the passband width and shift fre-
quency graphically.
• PBT indicator above switch lights when PBT
is in use.
➥
Push and hold for 1 sec. to enter the filter
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
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
(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.
• Filter set screen
• PBT operation example
PBT-CLR
FILTER
PBT-CLR
[TWIN-PBT]
PBT-CLR
Shows filter width, shifting value and condition
IF center frequency Interference Desired signal
Passband
Both controls at
center position Cutting a lower
passband Cutting both higher and
lower passbands
Interference Interference Desired signal
Passband
PBT1
PBT2
PBT1
PBT2
PBT1
PBT2
5
FUNCTIONS FOR RECEIVE