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M7/M7L/M7LT Modular Satellite Modem
Maintenance
M7/M7L/M7LT - Rev. 0.05
4-1
4.0
Maintenance
4.1.
Periodic Maintenance
The modem requires no mandatory periodic field maintenance procedures. The unit contains no
required periodic adjustments and the digital calibration data is held in EEPROM. Should a unit be
suspected of a defect in field operations after all interface signals are verified the proper procedure is
to replace the unit with another known working modem. If this does not cure the problem, other
equipment in the link, wiring or power should be suspect. There are no batteries or parts requiring
periodic service contained within the case. The only moving part is the internal fan, which is designed
for a service life in excess of 200,000 hours.There is no external fuse on the M7 Modem. The fuse is
located on the power supply assembly inside the case, and replacement is not intended in the field.
4.1.1.
Internal Reference Calibration
During factory testing and calibration the modem unit is compared to a known in-house reference and
calibrated. A default value is permanently stored representing this factory calibration. The unit may be
offset from this factory value by using the manual tuning or automatic recalibration.
Manual tuning of the modem’s reference is accomplished using the
<Unit: Ref
– Fine Tune>
parameter and entering a value from
–127 to +127
Automatic calibration of the modem’s internal reference is accomplished by inserting a known high
accuracy reference at the rear panel “External Reference” input and enabling the
<Unit: Test
– Cal
Ref>
item. The calibration should take several seconds and will indicate a successful completion. If
the calibration fails then the external reference was out of range in either level or frequency.
CAUTION!: The Reference Calibration procedure may result in lost traffic during performance of
the calibration! The calibration should not be performed in operating links without
prior arrangements.
The factory calibration may be restored by setting the
<Unit: Ref
– Fine Tune>
value to “0”.
4.2.
Modem Checkout
The following descriptions assume that the full system is in operation and that software is running
properly on the central processor.
4.2.1.
Initial Power-Up
CAUTION!: Before initial power-up of the modem, it recommended to disconnect the transmit
output from the operating satellite ground station equipment. This is especially true if
the current modem configuration settings are unknown, where incorrect setting could
disrupt existing communications traffic. New modems from the factory are normally
shipped in a default configuration which includes setting the transmit carrier off.
The modem
does not have a power switch so turning the unit “ON” is done by connecting the DC
power to the DC input connector J2. At every power-up, the modem processor tests itself and several
of its components before beginning its main monitor/control program. These power-up diagnostics
take approximately 1 second and show no results if successful. If a failure is detected, the indications
vary by the type of fault detected. A serious failure will result in the front panel Alarm LEDs flashing at
a rate of approximately 4 times a second, and the unit beeper sounding.
Most potential failures will result in the modem giving an description of the problem on the front panel
LCD display. Status indications are shown highest priority first.
The initial field checkout of the modem can be accomplished from the front panel or in the Terminal
Mode. The Terminal Mode has the advantage of providing full screen access to all of the modem’s
parameters, but requires a separate VT100 terminal or computer running a terminal program in
VT100 or ANSI mode.
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