Meinberg GPS163TDHS, Operating Instructions Manual

Page: 16 / 34

16
Powering up the system
If both, the antenna and the power supply have been connected, the system is ready to
operate. About 10 seconds after power-up the receiver´s TCXO has warmed up and
operates with the required accuracy. If the receiver finds valid almanac and epheme-
ris data in its battery-backed memory and the receiver´s position has not changed
significantly since its last operation the receiver can find out which satellites are in
view now. Only a single satellite needs to be received to synchronize and generate
output pulses, so synchronization can be achieved maximally one minute after
power-up.
If the receiver position has changed by some hundred kilometers since last operati-
on, the satellites´ real elevation and doppler might not match those values expected
by the receiver thus forcing the receiver to start scanning for satellites. This mode is
called Warm Boot because the receiver can obtain ID numbers of existing satellites
from the valid almanac. When the receiver has found four satellites in view it can
update its new position and switch to Normal Operation. If the almanac has been
lost because the battery had been disconnected the receiver has to scan for a satellite
and read in the current almanacs. This mode is called Cold Boot. It takes 12 minutes
until the new almanac is complete and the system switches to Warm Boot mode
scanning for other satellites.