Meinberg GPS167PC, Руководство по эксплуатации

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between antenna, diplexer and receiver must not be longer than 200m. If a cable with
less attenuation is used its length may be increased accordingly.
Powering Up the System
After the board has been mounted and the antenna has been connected, the system is
ready to operate. About 10 seconds after power-up the receiver´s TCXO operates with
the required accuracy. If the receiver finds valid almanac and ephemeris data in its
battery buffered 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 at least one minute after power-up. After 20 minutes
of operation the TCXO has achieved its final accuracy and the generated frequencies
are within the spezified tolerances.
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.
In the default mode of operation, neither pulse outputs nor the serial ports will be
enabled after power-up until synchronization has been achieved. However, it is
possible to configure some or all of those outputs to be enabled immediately after
power-up. If the system starts up in a new environment (e. g. receiver position has
changed or new power supply) it can take some minutes until the TCXO´s output
frequency has been adjusted. Up to that time accuracy of frequency drops to 10
-8
reducing the accuracy of pulses to ±2µs.