Ntp Server Static GPS Antenna Systems

The Global positioning System (GPS) is often used bydamage. Typically the GPS antenna is fairly small in
computer equipment, such as NTP Server systems,size, measuring less than 90cm in diameter. Low-cost
to provide an accurate timing reference for timepatch type antennas are also available, but these are
critical applications. This article provides an overviewgenerally better suited to vehicle applications.
of GPS for timing applications and describes theGPS Antenna Cable Types and Cabling Distances
equipment used to install a GPS antenna in a staticThe cable distance that can be utilised by a GPS
location.antenna depends mainly on the amplification of the
Overview - Using GPS for Accurate TimeGPS antenna and the quality of coax used in the
The Global Positioning System is a US military systeminstallation. A typical GPS timing antenna may have a
for worldwide navigation. The system consists of 24gain of 35 db. Relatively low-quality coax such as
orbiting satellites, each satellite has a highly accurateRG58 has an attenuation of 0.64 db/m at 1575 MHz.
atomic clock on-board synchronised to UTC time. TheTherefore, a cable run of 55m can be obtained using
satellites continuously broadcast time and positionRG58 cable. With very high quality coax cable, such
information. The time and position information can beas LMR400, an unaided cable run of 200m can be
obtained worldwide with a GPS receiver and antenna.achieved. However, very high quality coax can be
GPS works continuously in any whether conditions,expensive. A good price-performance compromise is
anywhere in the world. Additionally, there is no set upLMR200 cable, which can be run unaided to 80m.
fee or subscription charges to utilise the GPSExtending Cabling Distance with In-Line GPS Amplifiers
systems. Many computer timing systems and NTPIn-line GPS amplifiers provide further amplification of
Server systems utilise GPS as an accurate externalthe GPS signal to increase the cable distance
timing reference.between the GPS antenna and receiver. GPS
The Accuracy of GPS Timing Systemsamplifiers are fitted in-line with the antenna cable and
GPS receivers provide highly accurate position andobtain power from the receiver via the coax cable.
timing information. Typically, a GPS receiver canNo external power-supplies are required. Typically, a
provide positioning information to an accuracy of 15m.GPS amplifier may add a further 20 dB of gain, adding
NTP Server systems can obtain timing information30m of low-quality RG58 coax, 40m of LMR200 coax
from GPS to a resolution of a few nanoseconds.or 100m of high quality LMR400 coax. Additionally,
The GPS Signalmultiple in-line amplifiers may be utilised to further
The transmitted GPS signal is very weak low-powerincrease cable distance.
radio signal, designated L1 and L2. L1 is the civilianSharing a Single Antenna Between Multiple Receivers
GPS frequency transmitted at 1575.42 MHz. The- GPS Splitters
signals travel by line of sight and can pass throughGPS splitters allow a single GPS antenna to be utilised
clouds, glass and plastics but are blocked by objectsby two or more NTP server systems. The GPS
such as metal and brickwork. Therefore, the idealsplitter splits the signal received from the GPS
location for a GPS antenna is on rooftop with a fullantenna into multiple outputs for synchronizing
360-degree view of the sky. However, oftenmultiple NTP servers. GPS splitters are generally
installation on the side of a building or in a windowavailable with 2, 4 or 8 outputs.
can provide adequate results. As a rule of thumb, theProtecting GPS Systems - GPS Surge Suppressors
better the view of the sky, the greater the likelihoodSurge suppressors protect expensive NTP server
of a good consistent signal lock.equipment from electro-static discharges, such as
GPS Timing Antenna Typeslightning, that may be picked up by an externally
The GPS antenna acts as an amplifier to boost themounted GPS antenna. Surge suppressors are
GPS signal for transmission along a cable, usuallyinstalled in-line on the coax cable between the
coax, to the GPS receiver. GPS Timing antenna’santenna and receiver, ideally where the cable enters
provided with NTP server systems utilise athe building. Surge suppressors require a
pole-mounting system. The antenna screws to alow-impedance ground, to discharge any received
threaded pole for installation on rooftops. Thissurge. The surge suppressor requires no
arrangement provides the GPS antenna with a rigidpower-supply or additional cabling.
mount easily able to withstand high winds without