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Important Note: You must enter a sign (+ or -) after entering the numbers and before
pressing the BFO button. If you enter the sign before, the receiver will interpret it as a
step-tuning command and change frequency.
C. Exceptions: BFO Offset is fix-tuned to 0 Hz in CW1 and fix-tuned to ±1800 Hz in
ISB. In USB and LSB, offset is pre-programmed to track the selected bandwidth for best
AF response characteristics. Note that the BFO Offset function works only in CW mode,
and the BFO display remains blanked in other modes. To temporarily view a fixed offset
frequency in other modes, press and hold the BFO button. The fixed Offset will appear in
the display window until the button is released. For example, in ISB, the display will
read 'BFO Freq: ±1800 Hz', and in AM where no BFO is required, it will read 'No BFO
in FM/AM'. The LED on the BFO switch normally remains unlit in all modes except
CW.
4-18 PBT (Passband Tuning) button: The PBT button is used in the CW, USB and
LSB modes to shift the receiver's passband center without altering operating frequency.
The PBT feature is especially useful for rejecting interference caused by encroaching
signals, and for altering the receiver's audio characteristics during SSB or data reception.
To activate the PBT edit feature, press the PBT button. The switch will illuminate, the
Edit Knob will be assigned to the PBT shift function, the previous PBT setting will be
activated, and its frequency will be displayed in the PBT portion of the display:
A. To set Pass band Tuning via the Edit Knob: Rotate the Edit Knob for a setting that
reduces unwanted interference or produces a desired change in audio characteristics.
Shift is adjustable over a 4000 Hz range (-2000 to +2000 Hz). The shift frequency is
shown in Hz in the PBT area of the display window. In USB mode, a plus (+) shift
moves the pass- band toward higher-frequency audio response, and a minus (-) shift
moves it toward lower-frequency response. In LSB, this effect is reversed. In CW, the
PBT and BFO Offset functions interact and should be set for preference.
Once the desired shift is selected, it may be toggled in or out with the PBT button. The
current shift will be retained until a new value is entered. Activating another edit
parameter button will disengage the Edit Knob from the PBT function and exit the PBT
edit mode.
B. Set Passband Tuning via the Key Pad: Enter the desired PBT shift (in Hz) via the
keypad followed by the desired + or - sign to indicate direction of shift (numerical values
from 0 to 2000 are valid). When entering this number, the receiver's main frequency
4-8
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