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Ntp Server Static Gps Antenna Systems
By David Evans
The Global positioning System (GPS) is often used by computer equipment, such as NTP Server systems, to provide an accurate timing reference for time critical applications. This article provides an overview of for timing applications and describes the equipment used to install a antenna in a static location.
Overview - Using for Accurate Time
The Global Positioning System is a US military system for worldwide navigation. The system consists of 24 orbiting satellites, each satellite has a highly accurate atomic clock on-board synchronised to UTC time. The satellites continuously broadcast time and position information. The time and position information can be obtained worldwide with a receiver and antenna. works continuously in any whether conditions, anywhere in the world. Additionally, there is no set up fee or subscription charges to utilise the systems. Many computer timing systems and NTP Server systems utilise as an accurate external timing reference.
The Accuracy of Timing Systems
GPS receivers provide highly accurate position and timing information. Typically, a receiver can provide positioning information to an accuracy of 15m. NTP Server systems can obtain timing information from to a resolution of a few nanoseconds.
The Signal
The transmitted signal is very weak low-power radio signal, designated L1 and L2. L1 is the civilian frequency transmitted at 1575.42 MHz. The signals travel by line of sight and can pass through clouds, glass and plastics but are blocked by objects such as metal and brickwork. Therefore, the ideal location for a antenna is on rooftop with a full 360-degree view of the sky. However, often installation on the side of a building or in a window can provide adequate results. As a rule of thumb, the better the view of the sky, the greater the likelihood of a good consistent signal lock.
GPS Timing Antenna Types
The antenna acts as an amplifier to boost the signal for transmission along a cable, usually coax, to the receiver. Timing antenna's provided with NTP server systems utilise a pole-mounting system. The antenna screws to a threaded pole for installation on rooftops. This arrangement provides the antenna with a rigid mount easily able to withstand high winds without damage. Typically the antenna is fairly small in size, measuring less than 90cm in diameter. Low-cost patch type antennas are also available, but these are generally better suited to vehicle applications.
GPS Antenna Cable
Types and Cabling Distances
The cable distance that can be utilised by a antenna depends mainly on the amplification of the antenna and the quality of coax used in the installation. A typical timing antenna may have a gain of 35 db. Relatively low-quality coax such as RG58 has an attenuation of 0.64 db/m at 1575 MHz. Therefore, a cable run of 55m can be obtained using RG58 cable. With very high quality coax cable, such as LMR400, an unaided cable run of 200m can be achieved. However, very high quality coax can be expensive. A good price-performance compromise is LMR200 cable, which can be run unaided to 80m.
Extending Cabling Distance with In-Line Amplifiers
In-line amplifiers provide further amplification of the signal to increase the cable distance between the antenna and receiver. amplifiers are fitted in-line with the antenna cable and obtain power from the receiver via the coax cable. No external power-supplies are required. Typically, a amplifier may add a further 20 dB of gain, adding 30m of low-quality RG58 coax, 40m of LMR200 coax or 100m of high quality LMR400 coax. Additionally, multiple in-line amplifiers may be utilised to further increase cable distance.
Sharing a Single Antenna Between Multiple Receivers - Splitters
GPS splitters allow a single antenna to be utilised by two or more NTP server systems. The splitter splits the signal received from the antenna into multiple outputs for synchronizing multiple NTP servers. splitters are generally available with 2, 4 or 8 outputs.
Protecting Systems - Surge Suppressors
Surge suppressors protect expensive NTP server equipment from electro-static discharges, such as lightning, that may be picked up by an externally mounted antenna. Surge suppressors are installed in-line on the coax cable between the antenna and receiver, ideally where the cable enters the building. Surge suppressors require a low-impedance ground, to discharge any received surge. The surge suppressor requires no power-supply or additional cabling. Article Source: Article Beam - a service of A1 Web Server Web Hosting Dave Evans develops atomic clock time synchronisation systems to ensure accurate time on PC networks. Click here to find out more about GPS NTP Server solutions.
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