Comtech EF Data SNM-1010L - Manual (Page 155)

SNM-1010L Data/Control Modem Revision 0
Clocking Options MN/SNM1010L.OM
5.1.4 Transmit Clock Source
Select the Transmit Clock from the following sources.
• Continuous mode:
♦ Serial Clock Transmit (SCT) (internal) ± 10 PPM (from modulator).
♦ Terrestrial. Must be better than
± 130 PPM.
♦ External. Must be better than
± 100 PPM (must be locked to data).
♦ Receive Satellite Clock (Loop Timing). Receive data rate must be the same
as the transmit data rate. Must be better than ± 100 PPM.
• Burst mode:
♦ SCT (internal) ± 10 PPM (from modulator).
♦ External. Must be better than ± 100 PPM (must be locked to data).
5.1.4.1 Transmit Clock Source Specifications
Refer to the following listing for Transmit Clock Source specifications.
External Clock Frequency Range Must equal data rate
External Clock Amplitude Per selected interface specification
External Clock Impedance Per selected interface specification
5.1.4.2 Transmit Clock Switching Due to Failure of Selected Clock
The modem will automatically switch the transmit clock source to SCT on failure of the
selected clock.
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