Viavi 87339, Operation Manual

Page: 86 / 198

Testing
4 -5
STEP PROCEDURE
12. Enter the desired information on the Route Point edit page and press the Done
button.
13. Complete entering all the Route points.
14. To save Route for future use select Route function key from the Launch Bar.
Select Route Manage button, then enter file name on the Manage Routes popup
and press Save .
15. Select Simulation tab.
16. Select RUN key to start simulation.
17. Select STOP key to stop simulation.
NOTE:
Most GPS receivers expect active antennas. This means they supply a DC voltage
to the antenna connector. The GPSG-1000 has built in DC voltage blocking on the
GPSG - 1000 TX Port.
NOTE:
Some receivers ‘sense’ current draw on the DC supply to their active antenna. If
there is no current drawn, they may assume that no antenna is connected. In such
cases, the current draw must be simulated by some resistive load and perhaps a
series inductor between the signal line and the ground. Such a device may need
to be custom built, depending on the receiver requirements.
NOTE:
It is recommended that the receiver under test is ‘cold started’ and a fresh
almanac obtained from the GPSG-1000 simulation. This process may take several
minutes, dependent on the specific receiver.
NOTE:
Some receivers will not obtain a stable fix when using a simulation time earlier
than the selected almanac. Generally it is best to utilize an almanac that is dated
at least one day before the simulation date.