Icom IC-7800 Instruction Manual - Page 94

5 FUNCTIONS FOR RECEIVE I Twin PBT operation [TWIN PBT] for main [TWIN PBT] for sub [PBT CLEAR] for main [PBT CLEAR] for sub Shows filter width, shifting value and condition In general PBT (Passband Tuning) electronically narrows the IF passband width by shifting the IF frequency 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 frequency 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 positions, 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 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 PBT1 PBT2 Cutting a lower passband PBT1 PBT2 Cutting both higher and lower passbands PBT1 PBT2 Passband Passband IF center frequency Interference Desired signal Interference Interference Desired signal 5-12