4-20 FIELD TESTS & ADJUSTMENTS MDS 05-2415A01, Rev. A
display. (Units shipped from the factory are pre-programmed with a default loopback code
consisting of the last four digits of the radio’s serial number.)
The displayed loopback code is followed by the characters
UI (uninstalled) or I (installed) at
the end of the second line in the display to indicate the presence of a Remote Maintenance
Module. If no loopback code has been entered, the indication will be UI for uninstalled, even
if the module is present, since a valid loopback code has not been entered. When the
loopback code is entered, and the radio is shut down and re-powered up, the indicator will be
I for installed.
Programming a New Loopback Code
If you wish to program a new loopback code, type
PLBC_XXXX, where the underline character,
“_”, is a space and “
XXXX” is a four digit address code. This code identifies the unit during
diagnostic polling by the master station. Note—the code must contain four digits and no
letters. After the new loopback code has been entered, the radio responds by displaying the
code on the HHT display.
Diagnostics Mode Selection
The Remote Maintenance Module can be set for one of three levels (modes) of diagnostics
and control. The
MODE command is used to set the diagnostics and control mode. Review
Table 3-1—Diagnostics and Control Capabilities for detailed descriptions of the three
operating modes. MODE_3xxxx is used to invoke Remote Maintenance, the highest level of
diagnostics. Since it provides the highest level of diagnostics and control, many users prefer
to keep the radio set up for Remote Maintenance.
Diagnostics Deviation Adjustment
1. Loosen the four cover screws and remove the top cover from the transceiver by
lifting straight up.
2. Connect the transceiver’s ANTENNA connector to the input of the service monitor
using a short length of RG-8/U or RG-214 coaxial cable.
3. Set the service monitor to receive at the transceiver’s transmit frequency.
4. Connect the transceiver’s power cord and apply power.
5. With the Hand-Held Terminal (HHT) connected to the INTERFACE connector, open
the Diagnostics Channel using the OPEN command.
6. If Remote Maintenance is not already enabled, type MODE 3 xxxx, where xxxx is the
speed in bits per second (i.e., 1200, 4800 or 9600 bps) of the internal data modem
plugged into Jacks J6 and J8. If the radio is not equipped with an internal MDS
modem, use MODE 3 1200.
7. Type TEST_1 to activate a DTMF test tone and key the transmitter.
8. Measure the transmitter deviation on the service monitor. If the deviation is not
2.5 kHz, adjust it to 2.5 kHz using R6, TX Audio, on the Remote Maintenance
Module. (See Figure 4-6.)
9. Type
TEST_2 to disable the test tone and unkey the transmitter.
Temperature Calibration
The Remote Maintenance Module has a built-in temperature sensor used to measure the ra-
dio’s internal temperature during operation. The temperature sensor has been calibrated at the
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