Symmetricom Z3801A, User Manual

Page: 27 / 98

Chapter 1 Getting Started
Using Commands to Control Key Functions (Examples)
User Guide 1-15
Initiate “surveying”, an automatic determination of the
Receiver’s antenna position.
When “position survey” is invoked, the Receiver is set to ascertain the
position of its antenna automatically. This survey is important; correct
antenna position data is required for the Receiver to deliver specified
performance.
The Receiver uses data from orbiting satellites to survey; hence, the
antenna must be installed and operational for the survey to work.
However, if you have a limited view of the sky, you can complete basic
installation, then read forward to the section titled “To Install With a
Limited View of the Sky, To Bypass Position Survey Operation” on
page 1-16 for a means of overriding the survey operation and entering
position data directly.
The survey is an iterative process. The Receiver transits to “Position
Hold” when a usable position has been obtained.
Set the Receiver to survey using command:
:PTIME:GPSYSTEM:POSITION:SURVEY ONCE
Set the Receiver to compensate for the length of the
antenna cable.
The Receiver can be custom-configured to compensate for the length of
the antenna cable. The phase of the Receiver’s internal clock is
therefore offset from the GPS standard by the number of nanoseconds
of delay introduced through the antenna cable. The amount of error is
typically on the order of a few hundred nanoseconds. Should you decide
to correct for this error, Table 2-1A and Table 2-1B in Chapter 2,
“Features and Functions,” of this guide provides typical corrections for
standard antenna cable lengths.
Set the Receiver to compensate for antenna cable delay using
command:
:PTIME:GPSYSTEM:ADELAY <seconds>
or
:PTIME:GPSYSTEM:ADELAY <nanoseconds> NS
It is normal to observe that the Receiver momentarily goes into
holdover after any change in antenna delay.