Mds Sdm9-Bandpass-Type Duplexers; Testing And Removing An Internal Duplexer; Testing - GE MDS Master Station Technical Manual

realigned.
MDS SDM9—Bandpass-Type Duplexers
These duplexers (Figure 7-2. 900 MHz Bandpass Duplexer) typically allow the transmitter fre-
quency to change up to 500 kHz without undesired results. Since this type of duplexer cannot be
re-aligned in the field, we recommend contacting the GE MDS Technical Support Department if
you suspect a duplexer problem or need one for a different frequency.
(Adjustment generally not required for transmit changes up to 500 kHz)

7.5 Testing and Removing an Internal Duplexer

Testing

If you suspect that the internal duplexer is not functioning properly, perform the following steps
to determine if requires replacement:
1. Measure the RF power out of the antenna jack.
- If the power registers approximately +37 dBm (5 watts), the internal duplexer is
probably functioning correctly (see Table 8-1. dBm–Volts–Watts Conversion
Chart for dBm-volts-watts conversion chart).
- If the power registers significantly less than +37 dBm, proceed with Step 2.
2. Locate the TX SMA connection on the front of the duplexer tray.
3. Using an adapter, connect the RF power meter to the SMA Cable on the front of the unit
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 frequencies 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.
96
Figure 7-2. 900 MHz Bandpass Duplexer
MDS™ Master Station MDS 05-6399A01, Rev. E