Antenna Switch Module - GE MDS 4790M Installation And Operation Manual

Troubleshooting the
Antenna Switch
Removing the Antenna
Switch
70

Antenna Switch Module

The antenna switch connects the transmitter or receiver circuit to the station
antenna in a simplex radio.
NOTE:
The radio contains either an internal duplexer for full duplex opera-
tion or an antenna switch for simplex operation. Refer to "Internal
Duplexer" on page 68 for information on the internal duplexer.
If you suspect that the antenna switch is not functioning properly, perform the
following steps to determine if it needs to be replaced.
1. Measure the RF power out of the antenna jack.
If the power registers approximately +37dBm, the antenna switch is
functioning correctly.
If the power registers less than +37dBm, proceed with Step 2.
2. Open the radio chassis, locate the TX cable, and disconnect the cable from
vertical interface board.
3. Using an adapter, connect the RF power meter to the SMA connector on the
vertical interface board, key the radio and measure the RF power.
If the power registers +39 dBm, the antenna switch is functioning correctly.
If the power registers less than +39dBm, proceed with Step 4.
4. Use the front panel to switch to the alternate transmitter and again measure
the RF power output.
If the alternate transmitter registers +39dBm, the antenna switch likely needs
replacing.
5. Before replacing the antenna switch, make sure that +14vdc is present on pin
2 of J14 and pin 1 is less than 1vdc on the PCB interface.
To remove the antenna switch module:
1. Remove the four screws that mount the antenna switch module to the
chassis as shown in Figure 34.
2. Disconnect the cables from the switch module and lift the module out of the
chassis.
Antenna Cable
Figure 34. Antenna Switch Module Removal
MDS 4790M (MPT 1411) I/O Guide
Antenna Switch
TX Transmit Cable
RX Receive Cable
MDS 05-3628A01, Rev. B