Tektronix SPG8000 Technical Reference page 73

SPG8000 Technical Reference
GPS ANTENNA POWER. This menu item appears only when Option GPS is
installed. The GPS ANT connector on the rear panel can supply DC power for a
connected GPS antenna. Use the left (◄) or right (►) arrow button to select from
the following antenna power settings:
CAUTION.
To avoid antenna damage, do not turn on the DC antenna power until
you know that the antenna is designed to handle the selected voltage. Antenna
damage can occur if the antenna is not designed to handle the voltage you select.
OFF: No power is supplied to the GPS antenna.
3.3 V: Supplies 3.3 V DC to power the GPS antenna.
5 V: Supplies 5 V DC to power the GPS antenna.
When the GPS ANT connector is configured to provide power to the antenna, the
rear-panel POWER indicator lights as follows:
Blinks green to indicate an open circuit. This occurs if no antenna is
connected or if the current load is less than expected because a splitter or DC
block is being used.
Displays solid red if the connected antenna is shorted. A shorted antenna will
not damage the GPS7 module. If a splitter is used on the antenna, it may
appear as a short at DC but still pass through the RF signal, which would
allow the GPS to function.
Displays solid green if the current load of the antenna is within the nominal
range.
GPS POSITION. This menu item appears only when Option GPS is installed and
GPS Signal is the selected reference source. Use the left (◄) or right (►) arrow
button to select Fixed or Mobile. The Fixed and Mobile settings define how the
GPS receiver calculates the time and position information.
In fixed mode, an averaged position is stored in flash memory, and only the
time is calculated each second. This provides greater stability of the time
information, and allows operation with fewer satellites. This mode is well suited
to broadcast-type installations where the antenna and mainframe do not move.
Mobile mode recalculates both the position and time each second. This allows
for compensation of velocity and acceleration, so the frequency and timing
information stay correct while moving, at the expense of some stability. This
mode is required if the antenna and mainframe are moving.
For applications where the position changes occasionally, but where the antenna
and unit are not moving, then either mode may be applicable. Mobile mode
may boot up faster since it does not need to average 60 fixes to establish a fixed
location. However, fixed mode can run with fewer satellites once the position
is stored.
REF button menu
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