Icom IC-7700 Instruction Manual - Page 100

5 FUNCTIONS FOR RECEIVE ■ Twin PBT operation [TWIN-PBT] PBT-CLR Shows filter width, shifting value and condition • Filter set screen 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 both above and below the received frequency. ➥ The LCD shows the passband width and shift frequency graphically. • PBT indicator above PBT-CLR switch lights when PBT is in use. ➥ Push and hold 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 positions, push and hold 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 (SSB/CW/RTTY/PSK modes) or 100 Hz (AM mode) steps. • [TWIN-PBT] should normally be set to the center positions (PBT setting is cleared) when there is no interference. • 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 Both controls at center position PBT2 PBT1 Cutting the lower passband edge PBT2 PBT1 Cutting both lower and higher passband edges PBT2 PBT1 Passband Passband IF center frequency Interference Desired signal 5-12 Interference Desired signal Interference