Quantum and Evolution Series Installation and Operating Handbook
8-7
Set the Tx and Clock modes as follows to use the clock listed:
Clock from the interface / terrestrial network:
Tx Clock =
Tx clk in
, Rx Clock =
Tx clk in.
Modem internal clock
Rx Clock =
Internal
and feeds the clock to the terrestrial equipment. If the Rx output clock
is externally looped by equipment or internally then set Tx Clock =
Tx Clk In
. If the Rx
output clock is not returned to the modem Tx input by the equipment or the cable then set
Tx Clock =
Rx Clk
.
Station clock
Rx Clock =
Station
, Tx Clock as for ‘Modem Internal Clock’ above.
Satellite
This is not possible - with clock loop at the distant end, Rx satellite clock is
already
a copy
of our Tx clock we cannot loop it again.
8.1.3.2
No Clock Loop
If there is no clock loop, then both ends need the buffer active to cope with the normal
Doppler effect, plus the plesiochronous effect (i.e. the difference between the clocks at
each end). Apply the following rules to both ends.
8.1.3.3 Clock from the interface / terrestrial network
If the modem has a station clock (which also drives the network which the Rx output feeds),
then select Rx Clock =
Station
. If there is no station clock then set Rx Clock =
Tx Clk In
(which as the Tx clock comes from the network, is presumably derived from the same
master clock which clocks the network). Set the Tx Clock =
Tx Clk In
.
8.1.3.4 Other clock modes
These require careful consideration based on the exact situation. If you have questions
relating to this subject, and are willing to at least draw a diagram of the system you are
implementing then you are welcome to contact us by fax for advice for your exact
application.
8.1.3.5 Determining Buffer Size
Use the following calculation to determine the buffer size required for
any
application:
