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100 997-01530-01, Rev. C-25, Jan 2008
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Or, for example, to produce a repetitive one-microsecond pulse occurring on every hour, enter:
F111 PPO XXX:XX:10:00.000000<CR>
XL-GPS responds:
OK<CR><LF>
F113 – J3 Input (Freq Meas)
Note: Frequency Measurement is an optional feature. If purchased at the same time as the XL-GPS, it
comes enabled on the system. To purchase this option after you have purchased the XL-GPS,
contact Symmetricom Sales. See “
H: Sales and Customer Assistance” on page 143.
Use function F113 to configure J3 for a Frequency Measurement (Freq Meas) input, to display
Frequency Measurement information, or to disable J3 inputs.
F113 offers the following keypad settings:
• J3 Input Configuration: (FREQ MEAS, DISABLED) Displays “Disabled” if the Frequency
Measurement option has not been installed. Displays “Freq Meas” if it has.
• J3 Select Function: (DISPLAY FREQ MEAS, J3 INPUT CONFIG) Select to display the Freq Meas
information of to configure the Freq Meas input on J3.
• J3 Input Frequency: 1 MHz, 5 MHz, 10 MHz (Select the Freq Meas input frequency)
• J3 Input Impedance: 1kΩ, 50 Ω (Select the input impedance)
• Freq Meas Interval: 1 to 99999 seconds
The factory settings are 10 MHz, and 1kΩ.
Frequency Measurement (Freq Meas) Input
The Frequency Measurement (Freq Meas) option measures an external frequency applied to the J3
input relative to the disciplined XL-GPS oscillator.
Operation: Measurements are displayed on the front panel display and on the command line at the
specified measurement interval. The front panel displays the measured frequency offset (FREQ
OFFSET) and a countdown (COUNT) to completion of the measurement interval. The command line
states the measurement interval (e.g.,“Interval is 1 seconds”) on the first line, and then starts displaying
each measurements; each one on a new line.
Limitations: Note that the accuracy of the frequency measurement is based on the accuracy and stability
of the disciplined XL-GPS oscillator over the measurement interval. Short interval measurements of
external very high stability oscillators (e.g., Cesium) tend to measure the XL-GPS oscillator instead.
Refer to “
Time and Frequency Accuracy” on page 3, and to “Oscillators” on page 11 for more information
for the specifications of disciplined oscillators (while locked to a GPS reference source).