Comtech EF Data SDM-2020 - Manual (Page 50)

SDM-2020 Satellite Modulator Revision 7
Front Panel Operation MN/SDM2020M.IOM
5-8
5.6.1.1.1 CONFIGURATION:MODULATOR:TX-DR
TX-DR QPSK 1/2
15.000000 Mbps
Selections include: QPSK 1/2, 3/4, 5/6, or 7/8
8PSK 2/3, 5/6, or 7/8
16QAM 3/4 or 7/8
Programming is done by either data rate or symbol rate. Data rate refers to the
equivalent serial data rate at the data interface connector. Symbol rate refers to the
modulation rate after framing, trellis (Viterbi) coding, and Reed-Solomon coding are
applied.
The framing type selection affects the symbol rate (if programming from the data rate
[TX-DR] menu), or the data rate (if programming from the symbol rate [TX-SR] menu).
If data rate is programmed, the symbol rate menu is updated to reflect the code rate and
framing selections. If symbol rate is programmed, the data rate display is similarly
updated.
Programing the modulator data rate (DR) from 1.5 to 100 Mbit/s, in 1 bit/s steps is
limited by code rate and data interface.
1 Press while the menu is displayed to turn OFF TX-IF Output.
2 Press a second time while the menu is displayed to turn ON TX-IF OUTPUT.
3 Observe the on/off status of the TRANSMITTER LED.
On entry , the current data rate is displayed with the flashing cursor on the first character.
1 Press [ ←] or [→] to move the flashing cursor.
2 Press [ ↑] or [↓] to increase or decrease the digit at the flashing cursor.
3 Press to execute the change.
When is pressed to change the data rate, the transmitter is automatically turned
OFF to prevent the possible swamping of other channels.
Another menu is displayed that allows the operator to turn the transmitter ON again, simply by
pressing .