T e m p u s L X G P S U s e r M a n u a l
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C H A P T E R F I V E
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T e m p u s L X G P S U s e r M a n u a l
F R O N T - P A N E L K E Y P A D A N D D I S P L A Y
Carrier-to-Noise:
The carrier-to-noise ratio is an indicator of the GPS signal quality. This
number typically ranges from 30 to 45 dB when the instrument is locked.
Satellite ID#:
This field lists the satellites that are currently being tracked.
Reference Position
This display shows the current GPS position and allows you to enter a position, if desired. The GPS
reference position is the position of the GPS receiver antenna. Accurate position is necessary to gen-
erate precise time and frequency outputs.
The source field (SRC) indicates the source of the position information. Possible values are “un-
known”, “average” and “user”. When first installed, the position source will be “unknown”. It
changes to “average” after the receiver has computed the first 3-dimensional position fix. The posi-
tion continues to be averaged for about 24 hours. Computation requires that a minimum of 4 or
more satellites be in view. The position is shown as latitude, longitude and elevation. Latitude and
longitude are shown as hemisphere (North, South, East, West), degrees, minutes and seconds. Eleva-
tion is shown in meters above the WGS-84 ellipsoid.
With a rooftop antenna installation that has an unobscured view of the sky, the instrument will de-
termine position automatically. Once determined, the position information is saved in non-volatile
FLASH and will be restored after a power outage. After position has been determined, the instrument
can achieve time lock with only one satellite.
In some situations, visibility of the sky is limited and the unit may not be able to determine its posi-
tion. In this case the user must determine an accurate WGS-84 position by other means and input it
either through the serial interface or via the front panel. In addition to loading a new accurate refer-
ence position, the user can also invalidate an existing one by setting the position source to unknown.
This will force the instrument to re-establish a new reference position using the GPS satellite constel-
lation. Push the EDIT key to start the process. First, select the reference position source:
Unknown: Selecting “unknown” will cause the CALCULATE NEW POSITION AVERAGE
confirmation display to appear. Select YES. The front panel will return to the GPS
Reference Position display. This action will force the unit to re-establish a new reference
position. Once the receiver has computed a new accurate reference position the position
source will change from “unknown” to “average”.
User:
Selecting “user” will allow you to enter a position. It is very important that the new
reference position be accurate. Refer to
Appendix D - GPS Reference Position
for
detailed instructions on how to obtain an accurate reference position for your location.
GPS Dynamic Mode
The GPS dynamic mode setting affects the position value used by the system to derive accurate time
synchronization. In dynamic mode, the average position is the current position, i.e. there is no pos-
tion averaging. Set the mode to “static” when the instrument is in a static installation. Set the mode
to “dynamic” if the instrument is installed on a moving platform such as a ship or aircraft.
Oscillator Status
This display provides the oscillator type and electronic frequency control status. The oscillator
control DAC value indicates the frequency control setting. The system automatically sets this value
to remove frequency errors. Values may range from 0 to 65,535. Values less than 10,000 or greater
Summary of Contents for Tempus LX GPS
Page 1: ...Smarter Timing Solutions Tempus LX GPS Network Time Server User Manual...
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