5-13
5
FUNCTIONS FOR RECEIVE
■
Twin PBT operation
To reject interference, PBT (Passband Tuning) elec-
tronically narrows the IF passband width by shifting
the IF frequency slightly outside of the IF filter pass-
band. The IC-7700 uses DSP for the PBT function.
Moving both [TWIN-PBT] controls shifts the IF pass-
band center frequency both above and below the re-
ceived frequency.
➥
The LCD graphically shows the passband width
and shift frequency.
• PBT indicator above
PBT-CLR
switch lights when PBT
is in use.
➥
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.
➥
Hold down
PBT-CLR
for 1 second to set the
[TWIN-PBT] controls to the center positions.
The PBT is adjustable in 50 Hz steps in the SSB/CW/
RTTY/PSK modes, and 200 Hz in the AM mode.
In this time, the shift value changes 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.
[TWIN-PBT]
PBT-CLR
Shows passband width, shift value and condition
IF center frequency
Interference
Desired signal
Passband
Both controls in the
center positions
Cutting the lower
passband edge
Cutting both lower and
higher passband edges
Interference
Interference
Desired signal
Passband
PBT2
PBT1
PBT2
PBT1
PBT2
PBT1
• Filter set screen
• PBT operation example
BW: Passband width
Passband’s center frequency
IF center frequency
PBT1
PBT2
SFT: Shift value
• About passband width and shift value on the screen
