MDS 05-2415A01, Rev. A FIELD TESTS & ADJUSTMENTS 4-21
factory and the need for field adjustment of this parameter is rare. Nevertheless, instructions
are given below. If the temperature calibration is misadjusted, its value in remote (over-the-
air) and local diagnostics will be compromised.
1. Measure the temperature at or near the transceiver chassis using a thermometer that
is accurate to 1°C. The transceiver must be at room temperature.
2. Use the TEMP command to obtain the temperature reading for the radio. The reading
is in degrees Celsius.
3. If there is a difference between the thermometer reading and the TEMP indication,
adjust potentiometer R33, TEMP SET, on the Remote Maintenance Board to obtain a
match between the measurements taken on the HHT and those taken with the
thermometer. (See Figure 4-7.) The measurement given by the HHT is updated once
per second. That is, the TEMP command does not have to be invoked after each
adjustment of R33.
4. Close the Diagnostics Channel to the transceiver. and disconnect the HHT.
5. Reinstall the cover on the transceiver.
Forward Power & RSSI Calibration
If a Remote Maintenance Module is added to a transceiver as a field upgrade, or a module is
transferred from one radio to another, two diagnostic measurements need calibration for
maximum accuracy. These are the forward power (
FPWR) and received signal strength (RSSI)
functions.
Procedure
1. Connect a 50 Ω dummy load through a directional wattmeter to the ANTENNA
connector of the transceiver.
2. Connect the HHT to the INTERFACE connector of the transceiver.
3. Key the transmitter with the
KEY command from the HHT. Type KEY + ENTER .
4. Set the transmit power output to 5 watts using the TX Power Output level control,
R69, on the transceiver motherboard as indicated on the in-line directional
wattmeter.
5. Enter the calibrate power command, CPWR, from the HHT. Type CPWR + ENTER . The
forward and reflected power detectors will be automatically calibrated.
6. Dekey the transmitter with the DKEY command from the HHT. Type DKEY + ENTER .
7. Disconnect the directional wattmeter and dummy load from the
ANTENNA connector.
8. Connect a communications service monitor to the ANTENNA connector.
9. Inject an on-channel unmodulated –110 dBm (.710 µV) signal.
10. Enter the calibrate received signal strength low level command, RSSL, from the HHT.
Type
RSSL + ENTER . The low level RSSI calibration point is automatically
calibrated.
11. Increase the signal level to –60 dBm (225 µV) signal.
12. Enter the calibrate received signal strength high level command, RSSH, from the
HHT. Type RSSH + ENTER . The high level RSSI calibration point will be
automatically calibrated.
To Next Page
Loading...
