Meinberg LANTIME M600 Technical Information download pdf (Page 15)

NTP Target

The software package NTP was tested on different UNIX systems. Many UNIX

systems have pre-installed a NTP client. Only some configurations have to be made

(/etc/ntp.conf). NTP clients as freeware or shareware are also available for the most

other operating systems like Windows XP/2000/NT/95/98/3x, OS2 or MAC. The

following WEB site is recommended to get the latest version of NTP:

"http://www.eecis.udel.edu/~ntp/". More information you can find on our web page at

"http://www.meinberg.de/english/sw/ntp.htm".

GPS satellite controlled clock

A Meinberg GPS170 satellite controlled radio clock is used as a reference time

base. The satellite receiver clock GPS170 has been designed to provide extremely

precise time to its user. The clock has been developed for applications where

conventional radio controlled clocks can not meet the growing requirements in

precision. High precision available 24 hours a day around the whole world is the main

feature of the new system which receives its information from the satellites of the

Global Positioning System.

The Global Positioning System (GPS) is a satellite-based radio-positioning,

navigation, and time-transfer system. It was installed by the United States Department

of Defence and provides two levels of accuracy: The Standard Positioning Service

(SPS) and the Precise Positioning Service (PPS). While PPS is encrypted and only

available for authorized (military) users, SPS has been made available to the general

public.

GPS is based on accurately measuring the propagation time of signals transmitted

from satellites to the user’s receiver. A nominal constellation of 21 satellites together

with 3 active spares in six orbital planes 20000 km over ground provides a minimum

of four satellites to be in view 24 hours a day at every point of the globe. Four

satellites need to be received simultaneously if both receiver position (x, y, z) and

receiver clock offset from GPS system time must be computed. All the satellites are

monitored by control stations which determine the exact orbit parameters as well as

the clock offset of the satellites' on-board atomic clocks. These parameters are

uploaded to the satellites and become part of a navigation message which is

retransmitted by the satellites in order to pass that information to the user’s receiver.

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Meinberg LANTIME M600 Technical Information Page 15