GPS

GNSS Global Navigation Satellite Systems now provide the preferred GLOBAL Time and Frequency National and International referenced “off air” signals. US GPS, CIS Glonass, EU Galileo, the Chinese and Japanese GNS systems will enable a choice of non-military, civilian and commercial freedom to any user looking for long term security of ‘ultimate’ frequency and time accuracy.

At this time the US GPS and CIS Glonass systems provide both carrier and CA code information for time and frequency synchronisation in addition to navigation ephemeris for position fixing at any place on the Earth’s surface. The GPS system is preferred by most users at this time.

GPS frequency standards normally provide a 10MHz (+13dBm) and 1PPS (square wave TTL, 3.3VCMOS) outputs.

Today with Quartzlock’s E8-X and E8000  line, a GPS Frequency Standard is available for the same cost as an LF tracking RX was some 25 years ago accuracy to at least 1 x 10-12/day and x 10-10 over seconds is 100 x better than even the best LF Tracking RX. With low cost OCXO options the short term stability reaches x 10-12. The objective is to have stability similar to accuracy over short usable measurement times that meet the everyday needs of calibration and frequency referencing of largely OCXO based instrumentation with external referencing inputs. Frequency Counters, Spectrum Analyzers, Digital Oscilloscopes, Network Analyzers, Microwave Analyzers, Signal Generators, Wireless Analyzers etc.

The disadvantages of GPS are few but must be addressed. No sub aqua use. The antenna should have a clear view of the sky. The cable connecting the GPS antenna to the GPS standard should be as short as practical. Low loss cable should be used. Properly assembled connectors and in precision systems, matching for lowest VSWR / highest return loss should be the aim.

The advantages of GPS are: unsurpassed accuracy both for time and frequency, no drift, nationally and internationally referenced. Some 200 atomic clocks world-wide are compared, and in an algorithmically weighted average (by satellite time transfer) system, provided by BIPM (Paris) to give UTC. GPS time is provided by USNO that is also probably the largest contributor to UTC. UTC (GPS), UTC (USNO) and other leading national timing centres NIST (USA), PTB (Germany), Observatoire d Paris, NPL (UK) have time / frequency differences of parts in 10-14.

Quartzlock is equipped with both Active and Passive Hydrogen Masers to maintain our in-house frequency reference stable to x 10-15/100s. With a NIST FMS GPS reference system installed, we recorded offsets / day of e-15 occasionally and e-14 regularly of our Quartzlock A8-M 100% carrier phase tracking GPS disciplined rubidium.