Maxon SD170EX Series - Page 21

Service Manual SD170EX Series
Page 21 of 38
Adjust the RF output level of the RF signal generator to –47dBm and connect to the radio.
Monitor the output on the audio output pin and adjust RV401 for the specific audio output
level.
Squelch Adjustment
Before squelch adjustment is made the squelch type should be selected via software. Squelch
level to open or close (un-mute or mute) is set up by not only software control but also hardware
control and programmed by the system option of the ACC-916 programming software.
Squelch Adjustment (Noise SQ only)
Select a receiver channel which is programmed for narrow band (12.5 kHz) operation. Set the
RF signal generator to the receiver frequency and set the AF modulation signal to 1 kHz at
1.5kH deviation.
Adjust the RF output level of the RF signal generator until the 1 kHz signal is heard. Adjust
the RF signal to the desired level for squelch sensitivity as you monitor SINAD, usually 8 to 12
dB. On the RF board, adjust RV5 until the squelch is just un-muted (open).
Switch off the RF generator (squelch should be closed).
Switch on the RF generator, Squelch should be opened at the SINAD point where RV5 was
adjusted.
Select a receiver channel that is programmed for wide band operation (25kHz). Set the RF
signal generator to the receiver frequency and the AF modulation signal to 1 kHz at 3kH
deviation.
Adjust the RF output level of the RF signal generator until the 1kHz signal is heard, and then
adjust the RF signal to the desired level for squelch sensitivity as you monitor SINAD, usually
8 to 12 dB. On the RF board, adjust RV6 until the squelch is just un-muted (open).
Switch off the RF generator (squelch should be closed).
Switch on the RF generator, Squelch should be opened at the SINAD point where RV6 was
adjusted.
Disconnect the test equipment.
Squelch Adjustment (RSSI SQ only) using ACC-2016 & ACC-916
Default setting of squelch level for all radios is approximately set at:
Squelch open (un-mute) at -114 to -113dBm (0.45 - 0.5mV of the RX signal strength)
Squelch close (mute) at -117 to -116dBm (0.3 - 0.35mV of the RX signal strength)
Changing the default squelch settings requires use of the programming cable and software.
Those are designed for use not only as part of the programming kit but also as a tool of squelch
level setting.
Still using the same connections for the receiver performance test, run the programmer ACC-
916 on the PC and select calibration mode. Select “Custom Define” menu of Squelch program
menu of ACC-916.
Adjust the RF signal generator for the desired signal strength to OPEN squelch (e.g. default
setting is approximately –113dBm, equivalent to 0.5mV)
Press “Set(OPEN)” button, LED indicator will flash 3 times then it will be ON.
Adjust the RF signal generator for the desired signal strength to CLOSE squelch (e.g. default
setting is approximately -116dBm, equivalent to 0.35mV). Press “Set(CLOSE)” button, LED
indicator will flash 2 times then it will be OFF.
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