Icom IC-R8500 Instruction Manual - Page 17

4 RECEIVE FUNCTIONS s Squelch function The IC-R8500 has 2 types of squelch, noise squelch and S-meter squelch. Noise squelch: Only acts on noise; has good sensitivity. It can be adjusted for reception of weak signals. Strong signals exceeding a certain level will always cause the squelch to open. S-meter squelch: S-meter squelch does not open for weak signals but can be adjusted to open for signals over a wide range of strengths. Once you have selected a threshold point in a range, the IC-R8500 will open for all signals above this point. To adjust the squelch, rotate [SQUELCH]. • Clockwise rotation closes the squelch (sets the threshold point higher); counterclockwise rotation opens the squelch (for reception of weak signals). Noise squelch threshold (not available in SSB, CW, WFM and AM narrow modes) When [SQUELCH] is rotated past center, the S-meter shows the signal strength needed to open the squelch. S-meter squelch threshold • Signals below the S-meter level are muted. S 1 3 5 7 9 +20dB +60dB SIGNAL s Functions for FM D Center indicator FM signals have a wide bandwidth which makes them easy to receive. However, you may be tuned off-center resulting in audio distortion. The IC-R8500's offcenter indicators appear in such cases, making it easy to fine tune to the center of the frequency. D AFC AFC stands for automatic frequency control. The AFC circuit automatically compensates the tuning when a receive frequency drifts or goes off frequency. When one of the off-center indicators appears, the IC-R8500 can adjust the receive frequency automatically-when the AFC function is turned ON and an off-center frequency is received, the frequency in the display automatically changes to reflect the center of the signal. RECV One of these indicators appears when the received signal is off-center. AFC RECV When one of these indicators appears, the displayed frequency is automatically moved to the center frequency. s Functions for SSB/CW D IF shift The IF shift function electronically changes the center of the IF (intermediate frequency) passband frequency to reject interference. The IF shift is not available in FM and AM modes. Œ Adjust the [SHIFT] control for a minimum interference signal level. • The audio tone may be changed while the IF shift is in use.  Set the shift control to its center position when there is no interference. APF IF SHIFT APF IF SHIFT APF IF SHIFT Shifts low Center Shifts high 14