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MDS 4790M (MPT 1411) I/O Guide
MDS 05-3628A01, Rev. B
Front Panel
The front panel is secured to the chassis with spring-loaded latches. To remove
the panel, simply pull out at the bottom edge until it is free from the chassis
(Figure 31). You will also need to disconnect the modular cable from the back
of the panel. Reverse these steps to re-install the front panel on the chassis.
Invisible place holder
Figure 31. Front Panel Removal
Internal Duplexer
The internal duplexer allows the radio to transmit and receive at the same time
using one antenna.
NOTE:
The radio contains either an internal duplexer for full duplex opera-
tion or an antenna switch for simplex operation. Refer to “Antenna
Switch Module” on page 70 for information on the antenna switch.
Troubleshooting the
Internal Duplexer
If you suspect that the internal duplexer 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 approxi37dBm, the internal duplexer 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 (Figure 32).
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 reg39dBm, the internal duplexer 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 reg39dBm, the internal duplexer likely
needs replacing.
5. Before replacing the duplexer, verify that the duplexer frequency and radio
TX frequency match.
