Paradise Datacom Quantum Installation And Operating Handbook page 229

Quantum and Evolution Series Installation and Operating Handbook
Tx Data Tx Clock (TT) Internal Tx Clock (ST)
8.1.1.3 Receive Reference
When Receive Reference is selected, it allows the modem to provide an ST clock to the
DTE that is locked to the receive satellite signal. The timing is actually phase locked to
the Rx data rate but at the frequency of the Tx data rate. This is to allow asymmetric
operation. The DTE then synchronises the data going into the modem (SD) to this clock.
If the external clock is missing for any reason then the modem will substitute an internal
clock.
Tx Data Tx Clock (TT) Internal Tx Clock (ST)
Modem Tx
Data Interface
FIFO
DDS
PLL TCXO
VCXO
External Tx Clock Mode
Modem Tx
Data Interface
FIFO
DDS
PLL VCXO
VCXO PLL
Rx Clk
Receive Reference Tx Clock Mode
8-3