Comtech EF Data SDM-300A User Manual

Page 117

SDM-300A Satellite Modem

Revision 6

Front Panel Operation

MN/SDM300A.IOM

5–23

FUNCTION SELECT: CONFIGURATION: INTERFACE:

TX CLOCK PHASE

AUTO

Transmit Clock Phase: AUTO, NORMAL, or INVERT

Note: AUTO is the default.

Upon entry, the current setting of the TX clock phase is displayed. Press [

↑] or [↓] to make the

selection. When AUTO is selected, the modem will automatically select NORMAL or INVERT
to properly phase the TX clock with the TX data. Press [ENTER] to execute the change.

FUNCTION SELECT: CONFIGURATION: INTERFACE:EXT-CLK FREQ

EXT-CLK FREQ
1544.000 KHz

Programs the EXT REF clock input frequency between 8.000 to 10000.000 kHz.

Note: The clock rate shall be equal to the data rate unless the asymmetrical loop timing option
is present.

This clock frequency can be any multiple of 600 Hz from 2.4 to 64 kHz, and can be any
multiple of 8 kHz from 64 kHz to 4.376 MHz. This can be used for the Doppler/plesiochronous
buffer clock. It can be a referenced to SCT. Use the master clock input on J8 for the external
master clock . The external reference on CP3 only allows for 1, 5, 10, and 20 MHz external
reference input.

Upon entry, the current setting for the external clock is displayed. Press [

←] or [→] to increase

or decrease the digit at the flashing cursor. Press [ENTER] to execute the change.