Icom IC-7850 Instruction Manual - Page 138

Previous view 7 FUNCTIONS FOR RECEIVE ■■Twin PBT operation In general, the 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-7850 uses DSP for the PBT function. You can watch the nearby intended signal using the spectrum scope. (p. 6-2) qqRotate [PBT1] (inner control) and [PBT2] (outer control) to the opposite direction from each other to narrow the IF passband width. • Before rotating, the PBT settings of [PBT1] and [PBT2] should be cleared. • Rejects interference of both higher and lower passbands. If you rotate the control too much, the received audio may not be heard because the passband width is too narrow. • Displays the passband width and shift frequency. • The [PBT CLEAR] indicator lights. • Hold down [PBT CLEAR] for 1 second to clear the PBT setting. In that case, the [PBT CLEAR] indicator goes OFF. • T he variable range depends on the passband width and the operating mode. The edge of the variable range is half of the passband width. The PBT is adjustable in 25 Hz steps in the SSB/CW/RTTY/PSK modes, and 100 Hz in the AM mode. • Moving both [TWIN PBT] controls to the same position shifts the IF left or right. wwHold down [FILTER] for 1 second. • The Filter screen is displayed. The current passband width and shift frequency are displayed. eePush [EXIT/SET]. • Exits the Filter screen. NOTE: While rotating the [TWIN PBT] controls, noise may be heard. This comes from the DSP unit and does not indicate an equipment malfunction. [PBT CLEAR] indicator [FILTER] [TWIN PBT] control [EXIT/SET] [PBT CLEAR] • When operating [TWIN PBT] Passband width Filter width Shifting value (Duplicated with PBT1 and PBT2) Selected IF filter • "FILTER" display when operating [TWIN PBT] • About Passband width and Shift value on the screen IF center frequency Passband's center frequency SFT: Shift value PBT1 PBT2 BW: Passband width • PBT operation example PBT is OFF PBT2 PBT1 Cutting a lower passband PBT2 PBT1 Passband Cutting both higher and lower passbands PBT2 PBT1 Passband IF center frequency Interference Desired signal 7-5 Interference Desired signal Interference