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Installation
2.7 Self-Test Mode
⇒
CAUTION: The Self-Test Mode will disconnect the transmit and receive IF from the
ground station equipment and will therefore disrupt any traffic currently through the PSM-
500 under test. This Test Mode should not be used on a live traffic unit.
The PSM-500 provides a built–in self-test mode which uses the IF Loop-back and a predefined
sequence of actions to test the basic modem operation. This test mode can be used to verify
correct functioning of the modem before placing it into service. The modem is placed into self-test
mode by using the front panel controls to initiate the test mode sequence.
The Self-Test Mode does not use or change the current configuration parameters, and returns to
these parameters after the test is completed.
To access the Self-Test Mode from the front panel, select "Unit" and use the right arrow key to
scroll to the "Test" column of the configuration matrix and then scroll down until "Test Modem" is
displayed. Then press "Edit", the "3" key then "Enter" to start the test. The modem self-test only
requires approximately one minute. This tests both the lamp and unit functioning. Just the lamp
test is performed by selecting "1" above or the Loop tests by selecting "2" above.
If any portion of the self-test fails, the modem will halt on the failed test and enter a loop with 4
short "beeps" then pause for several seconds and repeat the 4 short beeps.
The Self-Test Mode state is not stored in EEPROM, therefore if the unit is powered off during
Self-Test Mode it will be configured for Self-Test Mode disabled when powered up again
2.8 IF Loop-back Test Mode
⇒
CAUTION: The IF Loop-back Mode will disconnect the receive IF from the ground
station equipment and will therefore disrupt any traffic currently through the PSM-500
under test. The transmit output is still active if it was enabled before initiating an IF Loop-
back. This Test Mode should not be used on a live traffic unit.
The PSM-500 provides a built–in IF loop-back mode which couples the transmit output to the
receive input via physical relays at the modem IF and an internal attenuator to achieve proper
input levels. This mode can be used to test modem operation with data, for instance using a BER
test set, before going up on the satellite.
The IF Loop-back Test Mode uses the current modulator carrier frequency (plus offset setting)
only and sets the demodulator to the same carrier frequency setting when in loop-back. The user
is responsible for all other compatible settings in order for the modulator and demodulator to
operate properly. When the IF Loop-back Test Mode is disabled, the demodulator carrier
frequency is returned to that stored in EEPROM (present before Loop-back was initiated).
To access the IF Loop-back Mode using the front panel, select the "Demod" and use the arrow
keys to scroll to the "Test" column of the configuration matrix and then scroll down until "IF
Loopbck" is displayed. Then press "Edit", the "1" key for enable and then "Enter" to enable the IF
Loop-back. When finished using this mode, return to the "Test - IF Loop" position and press the
"0" option key to disable.
2.8.1 Built-in BERT
When in IF Loop-back mode a Bit Error Rate Test (BERT) can also be performed using the
modem's built in BER test capabilities. The transmit and receive BERTs are independent and are
enabled in the <Int'f: Test – Mod BER> and <Int'f: Test – Dem BER> parameters. Note this
convention for accessing a parameter. It means press the "Int'f" key (if not already set) and scroll
left or right to the Test column and then up or down until the LCD displays "Test – Mod BER" on
the upper line. The BER test is enabled by pressing "Edit" and then pressing either "1" for a
Page 2-14
PSM-500/500L/500LT SCPC Satellite Modem
PSM-500/500L/500L T- Rev. 0.91
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