Meinberg GPS164/AQ/AHS, Руководство по эксплуатации

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Mounting the antenna
The GPS satellites are not stationary but circle round the globe in a period of about 12
hours. They can only be received if no building is in the line-of-sight from the
antenna to the satellite, so the antenna/converter unit must be installed in a location
from which as much of the sky as possible can be seen. The best reception is given
when the antenna has a free view of 8° angular elevation above horizon. If this is not
possible the antenna should be installed with a mostly free view to the equator
because of the satellite courses which are located between latitudes of 55° North and
55° South. If even this is not possible problems occure especially when at least four
sattelites for positioning have to be found.
The unit can be mounted using a pole with a diameter up to 60 mm. A standard
coaxial cable with 50
Ω
impedance (e.g. RG58C) should be used to connect the
antenna/converter unit to the receiver. Cable thinner than RG58 should be avoided
due to its higher DC resistance and RF attenuation. When using the optional antenna
diplexer the total length of one antenna line between antenna, diplexer and receiver
must not be longer than 300 m. If a cable with less attenuation is used its length may
be increased accordingly (e.g. 600 m with RG213).
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 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 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.