5-12
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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.
➥
The LCD shows the passband width and shift fre-
quency graphically.
➥
Push [FILTER] for 1 sec. to enter the filter set
screen. Current passband width and shift frequency
is displayed in the filter set 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.
• [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
PBT1
PBT2
PBT1
PBT2
PBT1
PBT2
Shows filter width, shifting value and condition
[TWIN PBT] for main
[PBT CLEAR] for main
[PBT CLEAR] for sub
[TWIN PBT] for sub
5
FUNCTIONS FOR RECEIVE
