Rx Sat Clock; Scte: Serial Clock Transmit External; Sct: Serial Clock Transmit; Ext Clk/Ext Bnc: External Clock, J16 - Comtech EF Data DMD50 Installation And Operation Manual

DMD50 Universal Satellite Modem

EXC Clock/EXT BNC (External Clock Source)

EXT IDI (Drop and Insert)
The modem handles RX Buffer clock selections based on source priority levels. The user assigns
priorities to the clock sources based on source selections. Source 1 has the highest priority and
Source 5 being the last resort or lowest priority. If a fallback clock is selected and activity is lost
at the highest priority source, the modem will fall back to the next highest priority clock with
activity. When activity resumes on a higher priority source, the modem resumes using the higher
priority source
Clock Source
RX SAT
SCTE
SCT
EXC BNC
EXT IDI
Refer to Front panel setup menus or Web Browser manual MN-DMDREMOTEOP
3.7.2.1

RX SAT Clock

The RX Sat clock is recovered from the satellite that is received from the distant end. If selected
the Buffer Clock is lock to the RX sat clock.
3.7.2.2

SCTE: Serial Clock Transmit External

When SCTE is selected as the Rx Buffer clock, the modem receives the clock from the Transmit
Terrestrial interface.
3.7.2.3

SCT: Serial Clock Transmit

If SCT clock is selected as the RX Buffer clock source, then it should be configured for internal.
SCT is sometimes referred to as Internal Timing or Send Timing (ST).
3.7.2.4

EXT CLK/EXT BNC: External Clock, J16

The External Clock that can be selected as the RX Buffer clock source. This is a 75ohm
unbalanced BNC connector. This clock source is also identified as EXT BNC. The External
Clock is often used as the station master clock. The RX Clock selection can be accessed in the
INTERFACE/RX SETUP menu. The clock frequency, EXT FREQ can be selected, in the
Interface/General Menu.
Clock specification:
Frequency:
Level:
MN-DMD50– Revision 3
Priority
1 of 5
2 of 5
3 of 5
4 of 5
5 of 5
1 MHz to 20 MHz
0.3 Vp-p to 5 Vp-p (Sine or Square wave)
Theory of Operation
3–13