Symmetricom ET6000, Руководство пользователя

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OPTION DESCRIPTIONS
External Frequency Control: < -1 x 10
-9
at 0V
(Electrical): > +1 x 10
-9
at +5V
The following specifications apply to the Selected 10 MHz Output at a 13dbm output level:
Harmonics:
-37 dBc
Spurious Noise: >-70 dBc
Phase Noise:
1Hz -76 dBc/Hz
10Hz -91 dBc/Hz
100Hz -131 dBc/Hz
1KHz -144 dBc/Hz
10KHz -146 dBc/Hz
It is recommended that the oscillator be nulled when the DAC value starts to approach either
extreme of 5,000 or 60,000. There is a hole on top of the oscillator for the oscillator adjustment
control.
There are two methods to null/calibrate the internal oscillator.
FIRST METHOD
The oscillator can be nulled against a known frequency standard with an oscilloscope or other
suitable means by using the following steps:
1.
Turn on the unit and wait approximately one hour for the oscillator to warm up and
stabilize.
2.
Sync one trace of an oscilloscope on the known frequency standard. Using the other
trace, monitor the 10MHz output of the unit.
3.
The input of the DAC must be held static prior to the nulling oscillator. This can be
accomplished one of three ways:
•
Disconnect the antenna from the rear of the unit.
•
Select the single satellite mode (1SV), and select a satellite that is not in view (or Pick
SV33 which doesn’t exist).
•
Disable disciplining. Refer to Chapter Four, “Disable Disciplining” in the User’s
Guide.
4.
Set the DAC value to it’s midpoint 32767. Refer to Chapter Four ,“Enter DAC Value” in
the User’s Guide.
Symmetricom Inc ET6xxx ExacTime GPS TC & FG (Rev C) C-43