Icom IC-7800

5-13
5
FUNCTIONS FOR RECEIVE
■ Twin PBT operation
In general PBT (Passband Tuning) electronically nar-
rows the IF passband width by shifting the IF fre-
quency to slightly outside of the IF filter passband
to reject interference. The IC-7800 uses DSP for the
PBT function. Moving both [TWIN PBT] controls to the
same position shifts the IF.
[TWIN PBT] for main
[PBT CLEAR] for main [PBT CLEAR] for sub
[TWIN PBT] for sub
➥ The LCD shows the passband width and shift fre-
quency graphically.
➥ Hold down [FILTER] for 1 second 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, hold down [PBT CLR] for 1 second.
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 Hz
steps in the SSB/CW/RTTY/PSK modes, and 100 Hz
in the AM mode.
•[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.
• PBT operation example
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
PBT2
PBT1
PBT2
PBT1
PBT2
PBT1
Shows filter width, shifting value and condition