| The Global Positioning System (GPS) is now a | | | | prone to lighting strikes or other voltage surges |
| very familiar tool in helping motorists to navigate | | | | so a suppressor is highly recommend to be |
| but GPS has more uses than merely triangulating | | | | installed inline on the GPS cable. |
| a position for direction finding, it can also be | | | | The cable between the GPS antenna and receiver |
| utilized to provide time and frequency information | | | | is also critical. The maximum distance that a cable |
| worldwide. | | | | can run is normally only 20-30 metres but a high |
| Developed by the United States military, GPS | | | | quality coax cable combined with a GPS amplifier |
| incorporates at least 24 communication satellites in | | | | placed in-line to boost the gain of the antenna can |
| high orbit, all of which contain precise timing | | | | allow in excess of 100 metre cable runs. |
| equipment to enable the satellite to triangulate | | | | A GPS receiver then decodes the GPS signal sent |
| positions accurately. | | | | from the antenna to a computer readable |
| However, each satellite’s highly accurate | | | | protocol which can be utilised by most time |
| atomic clock timing reference can also be used by | | | | servers and operating systems including, |
| NTP (Network Time Protocol) servers to | | | | Windows, LINUX and UNIX. |
| synchronise computer networks using the highly | | | | The GPS receiver also outputs a precise pulse |
| accurate GPS time as an external reference. | | | | every second that GPS Network Time Protocol |
| GPS is an ideal time and frequency source | | | | (NTP) servers and computer time servers may |
| because it can provide highly accurate time | | | | utilise to provide ultra-precise timing. The |
| anywhere in the world using relatively cheap | | | | pulse-per-second timing on most receivers is |
| components. Each GPS satellite transmits in two | | | | accurate to within 0.001 of a second of UTC |
| frequencies L2 for the military use and L1 for use | | | | (Coordinated Universal Time or Temps Universel |
| by civilians transmitted at 1575 MHz, Low-cost | | | | Coordonné) |
| GPS antennas and receivers are now widely | | | | GPS is ideal in providing NTP time servers or |
| available. | | | | stand-alone computers with a highly accurate |
| The radio signal transmitted by the satellite can | | | | external reference for synchronisation. Even with |
| pass through windows but can be blocked by | | | | relatively low cost equipment, accuracy of |
| buildings so the ideal location for a GPS antenna is | | | | hundred nanoseconds (a nanosecond = a billionth |
| on a rooftop with a good view of the sky. The | | | | of a second) can be reasonably achieved using |
| more satellites it can receive from the better the | | | | GPS as an external reference. |
| signal. However, roof-mounted antennas can be | | | | |