Comtech EF Data CDM-740 - Manual (Page 66)

CDM-740 Advanced Satellite Modem Revision 0
Front Panel Operation MN-CDM740
5–14
5.4.3 CONFIG: Clocks
Clocking: Ext-Ref Int-Ref-Adj
(
◄► E)
Select Ext-Ref or Int-Ref-Adj using the ◄ ► arrow keys, then press ENTER.
5.4.3.1 (CONFIG:) Clocks Æ Ext-Ref
External Frequency Reference:
Int10 Ext1 Ext2 Ext5 Ext10 10+Output
Select Int10, Ext1, Ext2, Ext5, Ext10, or 10+Output using the ◄ ► arrow keys, then press
ENTER. Note the following:
Selection Description
Int10 Internal Reference selection is available at 10 MHz.
Ext1
The unit phase locks to the external input at the rear panel BNC connector labeled EXT REF for External 1,
2, 5, or 10 MHz input.
Ext2
Ext5
Ext10
10+Output The Internal 10 MHz Reference is available via the rear panel BNC connector labeled EXT REF.
5.4.3.2 (CONFIG:) Clocks Æ Int-Ref-Adj
Internal Hi-Stability 10Mhz Reference
Fine Adjust: +000 (+/-999) (
◄► E)
Fine adjustment of the Internal 10 MHz reference oscillator is possible through this menu. Use
the
▲ ▼ arrow keys to edit both the sign ( + [positive] or – [negative]) and the value. The range
of values is from –999 to +999.
Note: The numbers displayed here do not correspond to an exact frequency increment. A user
should perform this fine adjustment while using an external frequency counter, connected to either:
a) the internal 10 MHz reference, if the user has internal access to the equipment,
or
b) the Tx Output, set for CW, 0 dBm output level, and an exact center frequency (1000
MHz, for example).
IMPORTANT
In order for this operating parameter to be retained, the user must save this
configuration in any one of the 10 available modem configurations (SELECT:
Utility
Æ Save/Load). Otherwise, when the CDM-740 power is cycled, this
value will be reset.