Smx920 Base Station Fault Finding Procedure; Smx920 Base Station; Transmitter Section - RELM SMX920 Technical Manual

SMX920 Base Station & Repeater
6. SMX920 Base Station Fault Finding
Procedure
The following test equipment may be required for the following tests:
♦
SMX920 in built Base Station Programming Utility
♦
RF Test Set (eg HP 8920 or equivalent)
♦
CRO (Cathode Ray Oscilloscope)
♦
RF Power Meter (capable of measuring to 60 Watts continuously)
♦
Multimeter
♦
+13.8V DC Power Supply (capable of supplying 15Amps)
♦
SMX920 test jig (Optional)

6.1 SMX920 Base Station

(The following tests will help diagnose faulty modules)
♦
Check that all of the required connections to the SMX920 Radio are made.
♦
Check that all of the interconnecting cables to the Control board are correctly
installed.
♦
Check voltage supply to the SMX920 by measuring both sides of Fuse 1 located
on the Microcontroller part of PCB. Replace fuse if necessary.
♦
Check that the power LED is lit. If not then go to section 6.2.
♦
Using the in built menu system check that the frequency tables and configuration
settings are correct.

6.1.1 Transmitter Section

♦
Connect the output of the Power Amplifier Module to a Comms test set or a RF
power meter.
♦
Using in built menu system, select Diagnostics check the TXVCO locking
voltage is between 2 – 14 V and there is no TXVCO 'Unlock' alarm displayed.
♦
If the locking voltage is out of spec or an 'Unlock' alarm is displayed then go to
section 6.4.1.
♦
Key up the transmitter using the software PTT in built menu system or by
shorting pins 5 (Earth) & 3 (PTT) of the RJ45 connector at the front of the radio
to ground.
♦
If the output power of the SMX920 is LOW then using the in built menu system
check that the 'Transmit Power' control is not on a low setting.
♦
Adjust the 'Transmit Power' control towards maximum looking for an increase
in the RF power output level. If there is no substantial change go to the
diagnostics screen and check that the Forward power and the Reflected power
levels are not abnormal. NOTE, If there is a high reflected power indication the
SMX920 firmware will hold the PA power low.
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Technical Manual
RELM/ BK RADIO