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SC720/SC820
System Adjustments
5.3
Settings
5.3.1
The Squelch Threshold
Squelch Threshold is the sensitivity of the receiver to RADIO carrier. The Squelch is set by Bosch, at the factory,
to 8 db SINAD.
TP1
1
JP2
1
2
3
4
5
6
7
8
JP1
RF AMPLIFIER
1.
System Power ON. When the shorting plug IS Installed on pin group #8 (DK1 000 UP 1 header), for normal
data repeater communications, the MODE LED will illuminate a BLINKING GREEN.
This provides a visual indication that the DK1000 Squelch and Hang Time adjustment controls are
LOCKED and ONLY SAFPCOM messages will activate the SC720/SC820 for Data Repeater
communications.
Any time that the shorting plug is removed from pin group #8, on the DK1000 JP1 header, the MODE LED
will illuminate a BLINKING RED. This provides a visual indication that the DK1000 Squelch and Hang Time
adjustment controls are UNLOCKED.
2.
Remove the shorting pIug from pin group #8 on the DK1000 JP1 header and place it on pin group #7
(DK1000 JPI header). The MODE LED will change to a BLINKING RED illumination.
The HANG (R11) and Squelch (SQU – R10) adjustment controls are NOW UNLOCKED and the DK1000
Controller Board is in the Squelch Repeat Mode for receiver tuning. The Squelch Repeat Mode allows ANY
RF signal to activate the SC720/SC820; NOT just SATECOM messages.
3.
Connect a RF Signal Generator to the receiver (RX) input, located on the rear panel of the SC720/SC820
Data Repeater.
•
Set the output, of the RF Signal Generator, to the SC720/SC820 radio receiver frequency.
•
Ensure the Squelch knob, on the front panel, is set FULL CCW.
•
Take the SINAD reading from Pin #12 or #15 on the accessory Jack located on the rear panel.
•
Inject an RF carrier signal at 8 db SINAD.
4.
Adjust the Squelch pot (SQU – R10), on the DK1000, to a point where the Proper selling of the Squelch pot
will illuminate the RED CD (carrier detect) LED is just staying On (illuminating RED).
Proper setting of the Squelch pot will illuminate the RED CD LED at and above 8 db SINAD.
5.3.2
Setting the Modulation Deviation
Modulation Deviation is the amount of carrier frequency swing caused by the modulating signal. The Modulation
Deviation is normally set by Bosch, at the factory, to +2.0 KHz for Narrowband SAFECOM radios. Bosch can
also set the Modulation Deviation to +3.0 kHz for special configuration export versions of the SAFECOM radio.
90007-201C
HANG
R11
CPU
MODE
LED
Figure 4: System Adjustments
SC720/SC820 Operation and Installation Guide
SQU
CN3
MOD
1
R10
R35
CN1
1
CN2
CD
LED
1
TP5
TP3
TP4
VR1
Page 18
FRONT
© 2004 Bosch Security Systems
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