Icom IC-R8500 Instruction Manual

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The IC-R8500 has 2 types of squelch, noise squelchand S-meter squelch.Noise squelch: Only acts on noise; has good sen-sitivity. It can be adjusted for reception of weak sig-nals. Strong signals exceeding a certain level willalways cause the squelch to open.S-meter squelch: S-meter squelch does not openfor weak signals but can be adjusted to open for sig-nals over a wide range of strengths. Once you haveselected a threshold point in a range, the IC-R8500will open for all signals above this point.To adjust the squelch, rotate [SQUELCH].• Clockwise rotation closes the squelch (sets the thresh-old point higher); counterclockwise rotation opens thesquelch (for reception of weak signals).FM signals have a wide bandwidth which makesthem easy to receive. However, you may be tunedoff-center resulting in audio distortion. The IC-R8500’s off-center indicators appear in such cases, makingit easy to fine tune to the center of the frequency.AFC stands for automatic frequency control. The AFCcircuit automatically compensates the tuning when areceive frequency drifts or goes off frequency.When one of the off-center indicators appears, theIC-R8500 can adjust the receive frequency auto-matically—when the AFC function is turned ON andan off-center frequency is received, the frequencyin the display automatically changes to reflect thecenter of the signal.144RECEIVE FUNCTIONS■ Squelch function■ Functions for FMD Center indicatorS-meter squelchthresholdNoise squelchthreshold (notavailable in SSB,CW, WFM andAM narrow modes)• Signals below theS-meter levelare muted.When [SQUELCH] isrotated past center,the S-meter showsthe signal strengthneeded to open thesquelch.SIGNALS 1 3 5 7 9 +20dB +60dBRECVOne of these indicators appears when the receivedsignal is off-center.RECVWhen one of these indicators appears, thedisplayed frequency is automatically moved to thecenter frequency.AFCD AFCThe IF shift function electronically changes thecenter of the IF (intermediate frequency) passbandfrequency to reject interference. The IF shift is notavailable in FM and AM modes.q Adjust the [SHIFT] control for a minimum interfer-ence signal level.• The audio tone may be changed while the IF shift is inuse.w Set the shift control to its center position whenthere is no interference.■ Functions for SSB/CWD IF shiftShifts low Center Shifts highIF SHIFTAPFIF SHIFTAPF IF SHIFTAPF