7.4 Powering up the system
Page 13
7.4 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 receivers TCXO operates with the required accuracy. If the receiver nds valid
almanac and ephemeris data in its battery buered memory and the receivers position has not changed signif-
icantly since its last operation the receiver can nd 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 nal accuracy and the generated
frequencies are within the specied tolerances.
If the receiver position has changed by some hundred kilometers since last operation, the satellites real ele-
vation 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 congure 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 TCXOs output frequency has been adjusted. Up to that time accuracy of frequency
drops to 10-8 reducing the accuracy of pulses to +-2
µ
s.
GPS170PEX
Date: 2009-06-24
13
Summary of Contents for GPS170PEX
Page 1: ...MANUAL GPS170PEX Satellite controlled Radio Clock 2009 06 24 Meinberg Radio Clocks GmbH Co KG...
Page 2: ......
Page 20: ...10 2 IRIG Standard Format Page 17 10 2 IRIG Standard Format GPS170PEX Date 2009 06 24 17...
Page 21: ...Page 18 10 Time codes 10 3 AFNOR Standard Format 18 Date 2009 06 24 GPS170PEX...
