The global positioning system (GPS) is widely used by it equipment, how to use NTP-server systems to provide an accurate timing reference for time-critical applications. This article provides an overview of GPS for timing applications and describes the equipment used to install a GPS antenna in a static position.
Overview - with GPS for accurate time
The global positioning system is a US-military system for worldwide navigation. The system consists of 24 satellites orbiting, each satellite has a very accurate atomic clock on board in UTC-time synchronized. The satellites broadcast continuously times and position information. Information around the world the time and location with a GPS receiver and antenna. GPS working conditions continuously all, if, anywhere in the world. In addition, there is no setup fee or subscription fees to use the GPS systems. Many computer systems and NTP server systems use GPS as an accurate external timing reference.
The accuracy of the GPS systems
GPS receiver provide very precise position and timing information. Usually a GPS receiver provide positioning information timing information of GPS with a resolution of a few nanoseconds with a precision of 15 m. NTP server systems get.
The GPS signal
The GPS signal is very weak low radio signal, L1 and L2. L1 is entrusted to the civilian GPS frequency at 1575.42 MHz. Signals from the line of sight travel and can be blocked through clouds, glass and plastic, but objects such as metal and masonry. It is therefore the ideal place for a GPS antenna on the roof with a full 360-degree view of the sky. However, the installation of a building or in a window can often deliver adequate results. As a general rule the view of the sky is the better, the greater the likelihood that a good consistent signal lock.
GPS timing antenna types
The GPS antenna serves as amplifiers to enhance the GPS signal for transmission over a cable that usually coax, GPS receiver. GPS timing antenna is provided with the NTP server systems use a pole position mounting system. The antenna bolts threaded pole for installation on the roofs. This agreement provides that GPS antenna with a rigid mount are easily able to withstand strong winds without damage. The GPS antenna is usually quite small, less than 90 cm in diameter. Low-cost patch type antennas are also available, but these are usually better suited for automotive applications.
GPS antenna of cable types and cabling distances
The cable distance that can be used by a GPS antenna the GPS antenna and the quality of the coax, used in the plant which depends mainly on the gain. A typical GPS timing antenna may be a plus of 35 DB. relative of RG58 coax low quality has an attenuation of 0.64 DB/m at 1575 MHz. Therefore, a series of cables can be obtained from 55 m with cable RG58. With very high quality coax cable, how can such as LMR400 a unassisted cable run of 200 m can be reached. Very high quality coax can be but expensive. A good price-performance compromise is LMR200, which can run at 80 m unassisted.
Extend the wiring with in-line GPS amplifier
In-line GPS amplifiers deliver a further strengthening of the GPS signal on the cable distance between GPS antenna and receiver. GPS amplifiers have in accordance with the antenna cable and turns the receiver via the coax cable. Requires no external power supply. Usually a GPS a further 20 dB amplifier can gain, 30 m from low quality of RG58 coax, 40 m LMR200 coax or 100 m high quality LMR400 coax Add Add. Furthermore, several in-line can be used amplifier to further increase the cable distance.
Sharing a single antenna between multiple receivers - GPS splitter
GPS splitter can be used by two or more NTP server systems a single GPS antenna. The GPS splitter divides the signal from the GPS antenna into multiple outputs for synchronizing multiple NTP servers receive. GPS splitter are usually with 2, 4 or 8 outputs.
GPS system - GPS protection surge suppressors
Overvoltage protectors prevent electrostatic discharges, such as Flash, which can be picked up by an externally mounted GPS antenna expensive equipment of the NTP server. Surge suppressors are installed inline on the coax cable between the antenna and the receiver, ideal where the cable enters the building. Surge suppressors require a low-impedance ground, perceive all received wave. The overvoltage protection requires no power supply or extra wiring.
Developed time synchronize atomic clock Dave Evans to ensure accurate time in computer networks. Click here to learn more about GPS NTP Server solutions.
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