92 MDS 4790/9790 Series I/O Guide MDS 05-3438A01, Rev. F
3. Using an adapter, connect the RF power meter to the SMA connec-
tor on the vertical interface board, key the radio and measure the RF
power.
• If the power registers +39 dBm, the radio board is functioning
correctly.
• If the power registers less than +39 dBm, 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 +39 dBm, the internal
duplexer probably needs replacing.
5. Before replacing the duplexer, verify that the highest or lowest fre-
quencies marked on the duplexer are the same as radio’s transmit
and receive frequencies or within the nominal operating range:
100 kHz for 400 MHz radios, and 500 kHz for 900 MHz radios.
Removing the Internal Duplexer
To remove the internal duplexer, follow these steps:
1. Disconnect the cables from the back of the duplexer (see Figure 45).
Figure 45. Internal Duplexer Cabling
NOTE: A number of different duplexers can be installed in the radio.
While the physical appearance of the duplexer may vary
slightly, its operation and removal remain the same.
2. Remove the four screws that secure the duplexer to the chassis as
shown in Figure 46 on Page 93.
3. Carefully lift the duplexer out of the chassis.
Duplexer Assy.
TX (Transmit) Cable
Antennna Cable
RX (Receive) Cable
Vertical Interface
Board
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