Microwave Data Systems MDS 4310 Installation, Operation & Field Maintenance page 82

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
is in degrees Celsius.
3. If there is a difference between the thermometer reading and the
adjust potentiometer R33,
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
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 (
functions.
Procedure
Connect a 50 Ω dummy load through a directional wattmeter to the
1.
connector of the transceiver.
2. Connect the HHT to the
3. Key the transmitter with the
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,
forward and reflected power detectors will be automatically calibrated.
6. Dekey the transmitter with the
7. Disconnect the directional wattmeter and dummy load from the
8. Connect a communications service monitor to the
Inject an on-channel unmodulated –110 dBm (.710 µV) signal.
9.
10. Enter the calibrate received signal strength low level command,
Type +
RSSL
calibrated.
11. Increase the signal level to –60 dBm (225 µV) signal.
12. Enter the calibrate received signal strength high level command,
HHT. Type
RSSH
automatically calibrated.
MDS 05-2415A01, Rev. A
command to obtain the temperature reading for the radio. The reading
TEMP SET
command does not have to be invoked after each
TEMP
INTERFACE
command from the HHT. Type
KEY
DKEY
. The low level RSSI calibration point is automatically
ENTER
+
. The high level RSSI calibration point will be
ENTER
FIELD TESTS & ADJUSTMENTS
, on the Remote Maintenance Board to obtain a
) and received signal strength (
FPWR
connector of the transceiver.
, from the HHT. Type
CPWR
command from the HHT. Type
ANTENNA
indication,
TEMP
RSSI
ANTENNA
+
.
KEY
ENTER
+
. The
CPWR
ENTER
+
DKEY
ENTER
connector.
ANTENNA
connector.
, from the HHT.
RSSL
, from the
RSSH
4-21
)
.