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SDM-300A Satellite Modem
CARRIER MODE
(Test Mode Configuration)
MODEM REFERENCE
RS ENCODER
Rev. 4
Programs the modem for continuous wave mode. Four modes of operation are
available:
•
NORMAL-MODULATED: The Carrier mode is normally in the off
position.
•
CENTER-CW: Generates a carrier at the current modulator
frequency. This can be used to measure the output frequency.
•
DUAL-CW: Generates a dual side-band suppressed carrier signal.
Side-bands are at one-half of the symbol rate from the carrier. This is
used to check the channel balance and carrier null.
•
OFFSET-CW: Generates a single, upper, side-band-suppressed
carrier signal. The upper side-band is at one-quarter of the symbol
rate from the carrier. When inverted spectrum is selected, this
generates a single, lower, side-band-suppressed carrier.
Upon entry, the Center mode is displayed. To activate this test mode, press
[ENTER]. Press [↑] or [↓] to select the desired mode. To return to the
Configuration menu, press [CLEAR].
Note: When [CLEAR] is pressed, the modem is configured to the state before
CW mode was invoked. The transmitter is automatically turned off to prevent
the possible swamping of other channels. To turn the transmitter on, use the IF
Output function.
Program the following references to the modulator:
•
INTERNAL
•
1, 5, 10, and 20 MHz external references (CP3)
•
High Stability Option only:
This highly stable 10 MHz can be output from the modem. It then can be used
as a clock reference for other equipment at the communications facility.
Note: If any external reference is selected for the modem reference and there
is no input to CP3, the modem will detect an alarm and switch to the internal
clock.
Upon entry, the Internal mode is displayed. Press [↑] or [↓] to make the
selection. Press [ENTER] to execute the change.
Programs the Reed-Solomon encoder ON or OFF.
Upon entry, the status of the Reed-Solomon encoder is displayed. Press [↑] or
[↓] to make the selection. Press [ENTER] to execute the change.
Note: Programming the Reed-Solomon encoder automatically turns off the RF
transmitter (because of symbol rate changes). If none of the proper overhead
types and data rates apply, the Reed-Solomon encoder program in the on state
will be rejected (double beep).
10 MHz Out
Operation
3–11
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