How to use the GPS Clock

How to appliance the GPS Clock

Computers Articles | December 19, 2013

This division discusses how the GPS clock can be used to provide a timing hint for computer networks. The GPS universe is often used for computer timing applications, in the same state as NTP time servers and timing references.

The Global positioning System (GPS) is a US militia system primarily intended for global navigation. The scheme provides highly accurate positioning information on account of navigation. The GPS system consists of a constellation of 24 orbiting satellites. Each follower has an on-board atomic clock, which is ideal for providing a highly accurate timing reference.

This article discusses in what state the GPS clock can be used to procure an accurate timing reference for computers and computer networks. The GPS connected view is often used for computer timing applications, in the same state as NTP time servers and correct timing references.

GPS Time

GPS time is continuously broadcast by the GPS system. Time is referenced to UTC (Universal Coordinated Time), what one is the same worldwide and does not be in dissension with time zones. GPS timing advice can be received with relatively dirty-cost equipment, such as a GPS receiver and antenna.

The GPS signal is real weak low-power radio signal. The memorable has two designated frequencies, L1 and L2. Frequency, L1, is the civilian GPS frequency transmitted at 1575.42 MHz. The notable travels in a straight line and be possible to pass through clouds, glass and plastics no more than is blocked by objects such of the same kind with metal and brickwork. The ideal situation for a GPS antenna is for that reason on rooftop with a good scan of the sky. Often, antenna investiture on the side of a erection or in a window can furnish a good enough view of the celestial expanse to give adequate results.

GPS Clock

The GPS order provides a free-to-air time synchronisation utility; there are no on-going fixed beforehand-up or subscription charges. Many computer systems utilise the GPS clock while an accurate timing reference. Highly exact NTP server systems use the GPS clock similar to an external reference to synchronise Network Time Protocol servers. Typically, a GPS receiver can provide timing information to in the limits of a few nanoseconds of UTC. The correctness achieved with a GPS receiver is without particularizing more than required for most computer network timing applications.

GPS Receiver Output

The GPS receiver constantly outputs position and timing notice. Generally, information is transmitted to and from the receiver via a RS232 serial interface. Standard GPS interface protocols have life, the most common being NMEA. The NMEA protocol consists of a designate by of sentences, or character strings, transmitted at 4800 bits by means of second. Contained within each character twine is accurate time and position intelligence. Due to the latencies involved in consecutive communication, the NMEA sentences are not without details accurate enough to provide a timing allusion. Therefore a pulse per second (PPS) output is utilised. A PPS output is one accurate pulse output each second that is aligned to the spasmodic effort of each second. The PPS output be able to be fed into a control course on the RS232 interface to furnish a hardware interrupt input for unerring timing. Often the DCD RS232 deate is utilised as a PPS input from the GPS receptacle. The PPS output combined with NMEA timing and positioning notice provides a highly accurate timing allusion for computers.

GPS AntennasThe GPS antenna is a signal amplifier that boosts the GPS token for transmission along a cable, usually flatter, to the receiver. GPS antennas used conducive to timing purposes are generally dome-shaped loadstar mounting devices for permanent installation in a static establishing. Typically, the GPS antenna is fairly sordid in size, measuring less than 900 mm in diameterGPS CablingThe cable remoteness that can be utilised by a GPS antenna and receiver depends on the amplification of the GPS antenna and the temper of coax used in the investiture. A typical GPS antenna may obtain a gain of 35 db. Low-character coax such as RG58 has every attenuation of 0.

64 db/m at 1575 MHz. Therefore, a cable risk of 55m can be obtained using RG58 cable. Higher temper coax, such as LMR400, an unsupported cable run of 200m can be achieved. However, very high quality persuade by fondling can be expensive. A good come to an understanding is LMR200 cable, which can have existence run unaided to 80m. Longer distances be possible to be achieved with the aid of GPS amplifiers, that amplify the GPS signal still more distant, to increase cable distance.

Article Tags: Accurate Timing Reference, Highly Accurate, Accurate Timing, Timing Reference, Timing Information