Motorola VSWR, Service Manual Supplement

Page: 38 / 44

Testing the VM
5th Feb 99
2–4
Service Manual Supplement: VSWR Monitor for M-Cell 6
68P02900W86-O
Testing the VM
General
The test procedure described below is designed to test that the VM is working and that
the built-in alarm circuits generate a fault signal when a fault condition is deliberately
induced.
Check that all connections have been made correctly and that the jumper settings are
correct before carrying out the test procedure.
Test procedure
The procedure for testing the VM is as follows:
1. Switch on the –48 V dc power supply and check that the green dc power LED on
the VM is illuminated.
2. Switch on the BTS transmitter to generate RF power and check that the three red
VM alarm LEDs are not lit.
3. Disconnect the alarm input cable from the PIX connector on the BTS and connect
the DMM across the pair of contacts which form the alarm circuit from the VM.
(The pins used will depend on the alarm configuration chosen and the alarm wiring
configuration at the BTS.)
4. Disconnect the Rx coaxial cables (one at a time) at the antenna connection points
for the site and check that the corresponding alarm LED on the VM is illuminated.
Check that the DMM reads an open-circuit of more than 100 k
Ω
on each Rx alarm
circuit which is displaying an illuminated alarm LED.
5. Reconnect the Rx cables. Check that the Rx alarm LEDs on the VM are not lit and
the DMM reads a short circuit of less than 1
Ω
.
6. Disable transmitter RF power to the VM as described previously.
Check that the BTS is unable to transmit RF power before disconnecting the
Tx cable.
WARNING
Disconnect the Tx coaxial cable at the antenna connection points for the site,
restore transmitter power and check that the Tx alarm LED on the VM is
illuminated. Check that the DMM reads an open-circuit of more than 100 k
Ω
on the
Tx alarm circuit.
7. Disable transmitter RF power to the VM. Reconnect the Tx cable and then restore
transmitter power. Check that the Tx alarm LED on the VM is not lit and the DMM
reads a short circuit of less than 1
Ω
.
8. Disconnect the dc input power cable from the VM. Check that the DMM reads an
open-circuit of more than 100 k
Ω
.
9. Disconnect the DMM and reconnect the alarm input cable to the BTS PIX
connector.
10. Reconnect the dc input power cable to the VM.
The VM is now ready for operation.