9-12 MTR3000 Radio Frequency Distribution System (RFDS) Equipment: Field Tuning Procedures
9.4.1.4 Antenna Relay
The antenna relay module is not field repairable and should be replaced in its entirety if it is faulty. To
replace it,
1. Turn off the base station/repeater power by turning off the breaker at the AC or DC source.
2. Remove the Antenna Relay module (installed on a flange on the rear of the PS module) by
• disconnecting the control and RF coaxial cables and
• using a Torque
Driver T20 bit, remove the screws which secure the Antenna relay to the base
station/repeater.
3. Ensure that the correct replacement Antenna Relay module is being installed.
4. Install the replacement Antenna Relay module by reversing the procedures outlined in step 2
above.
5. Restore power to the base station/repeater.
9.5 Field Tuning Procedures
9.5.1 Base Station/Repeater Preselectors
Depending on the configuration, the base station/repeater may have an External Preselector
assembly with the always present internal preselector. The External Preselector assembly is a 3-
pole bandpass filter equipped with tuning slugs to adjust the passband corresponding to the
operating frequency (s) of the base station/repeater. For the internal preselector, circuitry in the
Receiver Module provides a varactor-tuned bandpass filter which adapts to the required frequency
range under the control of the Station Control Module.
The external preselector must be retuned if the preselector assembly or Receiver Module are
replaced in the field, or if the base station/repeater operating frequency (s) are modified. The internal
varactor-tuned preselector is factory-tuned to cover the relevant frequency band in its entirety. The
internal preselector does not require field tuning even if the Receiver Module is replaced.
9.5.1.1 External Preselector Tuning Procedure (with basic instruments)
9.5.1.1.1 Test Equipment
The following test equipment are required to properly tune the external preselector assembly:
• RF signal generator – Aeroflex 3900 Series Communications System Analyzer (see note
below), or HP8656A signal generator (or equivalent)
• Dip/Peak Monitor – HP435B Power Meter (or equivalent) with HP8484A sensitive power
head, Boonton Model 92E with BNC input, or Aeroflex 3900 Series Communications System
Analyzer using the spectrum analyzer function
• Torque
Driver capable of delivering 1.36 Nm (12 in-lb) of torque with a 10 mm deep well
socket
• Tuning probe
• Flat-blade screwdriver
Note
There is no External Preselector for 800/900 MHz frequency band.
Note
Tuning for best SINAD response DOES NOT result in optimum tuning of the preselector
assembly. Use this field tuning procedure to obtain optimum preselector performance.
Note
When using Aeroflex 3900 Series Communications System Analyzer as the signal
generator, the RF signal must be taken from the Antenna port.
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