| Copyright (c) 2007 Galleon Systems | | | | GPS Antenna Types: The GPS antenna is essentially |
| This article explains how GPS Time server Systems | | | | a signal amplifier. The antenna improves the received |
| achieves exact timing information to give a highly | | | | GPS signals for transmission along a cable to a |
| accurate timing reference for Network Computer time. | | | | receiver for decoding. A Coax Cable is normally used |
| GPS System is a navigation system operated by the | | | | to transfer signal information between the GPS |
| Military but also can be used by the civilian and does | | | | antenna and receiver. These antennas can be |
| not need any subscription. The GPS System is known | | | | provided in different shapes and sizes. The general |
| as an extremely accurate global positioning system. | | | | antennas being pole-mounted are dome shaped |
| Each GPS satellite has an onboard a highly accurate | | | | antennas and small patch type antennas. The |
| atomic clock, ideal for supplying the correct time for | | | | pole-mounting antenna screws onto the threaded pole |
| computer network time synchronization. | | | | for mounting. Whereas the patch type antenna is a |
| GPS Time Servers: The GPS System exist of a | | | | small flat bottomed device ideal for mounting on a |
| constellation of 24 orbiting satellites, each has a precise | | | | windowsill. |
| atomic clock timing reference and covers the entire | | | | GPS Receivers: GPS Receivers decipher the GPS |
| globe. The exact time information can be continuously | | | | transmission received from the antenna into a useable |
| broadcast from each of the satellites. You can receive | | | | format. NMEA is the most common protocol used by |
| the broadcast timing information with a relatively low | | | | the GPS receiver. This protocol insists a number of |
| cost GPS antenna and receiver. | | | | sentences which provide a packet on information |
| GPS time is transmitted as Universal Coordinated | | | | confirm of time, date and positioning information. The |
| Time (UTC), which is similar to Greenwich Mean Time | | | | NMEA protocol quotes information indicating visible |
| (GMT). The UTC time is the same worldwide and | | | | satellites and satellite location. |
| does not vary regarding the time zone or daylight | | | | GPS time servers can use a specific GPS timing |
| saving time. UTC is a very accurate atomic time | | | | receiver. These timing receivers have additional |
| standard sustained by atomic clocks located in national | | | | functions to provide a highly accurate reference time. |
| standards laboratories. UTC has consistent seconds | | | | The timing receiver can also perform an automated |
| distinct by the International Atomic Time (TAI) Institute. | | | | survey and compare satellite atomic clocks to check |
| GPS Radio Transmission: The GPS satellites | | | | for synchronicity. GPS time servers may also use an |
| broadcast information as very low-power radio | | | | accurate pulse per second (PPS) output, which |
| frequency transmission. There are two designated | | | | provides a highly accurate reference trigger for GPS |
| frequency that are used, one for civilian use coded L1 | | | | timing, generated by the receiver. |
| and the Military use coded L2.The civilian L1 frequency | | | | GPS Antenna Installation: The gain of the antenna and |
| is transmitted at 1575MHz. It can easiliy pass through | | | | the coax is important for the maximum cable distance |
| plastic and glass but is blocked by metal and brick. | | | | that can be used by a GPS antenna and receiver. An |
| GPS Antenna Location: The precondition to receive | | | | antenna used with a GPS time server may have 35dB |
| transmission from as many satellites as possible is a | | | | gain. RG58 coax has an attenuation of 0.64dB/m at |
| good clear view to the sky. Ideally a roof mounted | | | | 1575MHz. Therefore a cable length of 35/0.64=55m |
| antenna is best with a full 360-degree view of the sky. | | | | could be used. Higher quality coax has a much lower |
| Conversely, an antenna can be located on the side of | | | | attentuation value allowing longer cable runs. Also GPS |
| the building with a 180-degree view of the sky if the | | | | amplifiers and updown converters can be utilized to |
| horizon is not too obscured. | | | | increase the cable length. |