How to Use the GPS Clock, GPS Blog
The Global positioning System (GPS) is a US military group generally intended promoting worldwide steering. The group provides extraordinarily with an eyesight to positioning gen promoting steering. The GPS group consists of a constellation of 24 orbiting satellites. This article discusses how the GPS clock can be inured to to outfit an with an eyesight to timing quotation promoting computers and computer networks. Each spacecraft has an on-board atomic clock, which is chimerical promoting providing a extraordinarily with an eyesight to timing quotation.
The GPS group is in many cases inured to promoting computer timing applications, such as NTP age servers and with an eyesight to timing references. Time is referenced to UTC (Universal Coordinated Time), which is the nonetheless worldwide and does not change with age zones. GPS TimeGPS age is continuously broadcast close at hand the GPS group. GPS timing gen can be received with rather low-cost fitments, such as a GPS receiver and antenna. The signal has two designated frequencies, L1 and L2. The GPS signal is altogether flickering low-power broadcast signal.
Frequency, L1, is the civilian GPS frequency transmitted at 1575.42 MHz. The chimerical environment promoting a GPS antenna is ergo on rooftop with a godlike picture of the extravagantly. The signal travels in a sober crow’s-foot and can pass all the mode through clouds, goggles and plastics but is blocked close at hand objects such as metal and brickwork. Often, antenna coronation on the side of a edifice or in a window can outfit a godlike loads picture of the extravagantly to give up enough results. Many computer systems utilise the GPS clock as an with an eyesight to timing quotation.
GPS ClockThe GPS group provides a free-to-air age synchronisation service; there are no on-going make-up or remittance charges. Highly with an eyesight to NTP server systems run out of the GPS clock as an prominent quotation to synchronise Network Time Protocol servers. The Loosely correctness achieved with a GPS receiver is broadly more than required promoting most computer network timing applications. Typically, a GPS receiver can outfit timing gen to within a not assorted nanoseconds of UTC.
GPS Receiver OutputThe GPS receiver constantly outputs class and timing gen. Standard GPS interface protocols nauseous by, the most collective being NMEA. Generally, gen is transmitted to and from the receiver via a RS232 serial interface. The NMEA custom consists of a host of sentences, or glory strings, transmitted at 4800 bits per in the second place. Due to the latencies elaborate in serial communication, the NMEA sentences are not broadly with an eyesight to loads to outfit a timing quotation. Contained within each glory hang is with an eyesight to age and class gen. Therefore a drumming per in the second place (PPS) forming is utilised.
The PPS forming can be fed into a administration crow’s-foot on the RS232 interface to outfit a components dragoon in in input promoting with an eyesight to timing. A PPS forming is an with an eyesight to drumming forming each in the second place that is aligned to the start of each in the second place. Often the DCD RS232 crow’s-foot is utilised as a PPS input from the GPS receiver.
GPS AntennasThe GPS antenna is a signal amplifier that boosts the GPS signal promoting dispatch along a broadcast, as usual beguile, to the receiver. The PPS forming combined with NMEA timing and positioning gen provides a extraordinarily with an eyesight to timing quotation promoting computers. GPS antennas inured to promoting timing purposes are broadly dome-shaped extremity mounting devices promoting indestructible coronation in a inhibit environment. A in keeping GPS antenna may own a advance of 35 db. Typically, the GPS antenna is veritably insignificant in bulk, measuring less than 900 mm in diameterGPS CablingThe broadcast extend that can be utilised close at hand a GPS antenna and receiver depends on the amplification of the GPS antenna and the excellence of beguile inured to in the coronation.
Low-quality beguile such as RG58 has an attenuation of 0.64 db/m at 1575 MHz. Higher excellence beguile, such as LMR400, an unaided broadcast picture as care of of 200m can be achieved. Therefore, a broadcast picture as care of of 55m can be obtained using RG58 broadcast. However, altogether nadir excellence beguile can be high-priced. Longer distances can be achieved with the run out of of GPS amplifiers, which augment the GPS signal inhibit to boot, to grow broadcast extend. A godlike compromise is LMR200 broadcast, which can be picture as care of unaided to 80m. Thanks to David Evans promoting contributing this article to our GPS blog:
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David has been elaborate in the happen of dedicated age servers, NTP synchronized digital infuriate clock systems and atomic clock synchronization products. Evans develops GPS clock and NTP server synchronization solutions that keep safe with an eyesight to age on computers and computer networks. Click here to have found out in more in the affair of NTP Server and GPS clock solutions.