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Encyclopedia > Radio clock
A radio clock
A radio clock

A radio clock is a clock that is synchronized by a time code bit stream transmitted by a radio transmitter connected to a time standard such as an atomic clock. The picture shows a type of radio-controlled digital clock. Radio-controlled analog clocks are also available. File links The following pages link to this file: Radio clock Categories: GFDL images ... File links The following pages link to this file: Radio clock Categories: GFDL images ... A clock (from the Latin cloca, bell) is an instrument for measuring time. ... Synchronization is coordination with respect to time. ... Timecode is also the title of a 2000 film directed by Mike Figgis which was shot in one continuous take. ... A time scale specifies divisions of time. ... Chip-Scale Atomic Clock Unveiled by NIST An atomic clock is a type of clock that uses an atomic resonance frequency standard to feed its counter. ... Basic digital alarm clock without a radio. ...


A radio-controlled clock consists of an antenna for receiving the RF time code signal, a receiving circuit to convert the time code RF signal into the simple (digital) time code, and a controller circuit to decode the time code bit stream(s) and to drive an output circuit, which could be an LCD in case of digital clocks or stepping motors in the case of analog clocks. LCD redirects here. ...

Contents

Operation

Radio clocks depend on time signal radio stations, which usually

  • refer the broadcast frequency to the frequency standard
  • broadcast 'pips' to identify the starts of second intervals
  • broadcast time codes as a way of identifying second intervals
  • publish the exact geographic location of each antenna, so the radio signal’s time of propagation can be estimated.

A variety of frequencies helps reception no matter what the ionospheric weather. Timecode is also the title of a 2000 film directed by Mike Figgis which was shot in one continuous take. ... Radio propagation is a term used to explain how radio waves behave when they are transmitted, or are propagated from one point on the Earth to another. ...


Terrestrial time signals

Radio clocks synchronized to terrestrial time signals can usually achieve an accuracy of around 1 millisecond relative to the time standard, generally limited by uncertainties and variability in radio propagation. Radio propagation is a term used to explain how radio waves behave when they are transmitted, or are propagated from one point on the Earth to another. ...


Time signals that can be used as references for radio clocks include

  • U.S. NIST Broadcasts:
    • Longwave radio station WWVB at 60 kHz (binary coded decimal only) at 50 kW,
    • Shortwave radio station WWV (a male voice, Fort Collins, Colorado, about 100 km north of Denver at approximately 40°40′49″N, 105°02′27″W ) at 2.5, 5, 10, 15 and 20 MHz at 2.5 kW to 10 kW,
    • Shortwave radio station WWVH (a female voice, on Kauai near Kekaha, at about 21°59′16″N, 159°45′50″W) at 2.5, 5, 10, and 15 MHz at 2.5 kW to 10 kW.
  • German Broadcasts: A time signal from DCF77 (Mainflingen, a transmitter near Frankfurt at about 50°01′N, 9°00′E) can be received on 77.5 kHz to a range of about 2000 km.
  • Canadian Broadcasts: The official time can be obtained by tuning to radio station CHU (Ottawa, Ontario) at 3.33, 7.335 and 14.67 MHz, with FSK digital time data sent once per minute at 300 baud.
  • UK Broadcasts: A time signal from MSF, an atomic clock near Anthorn (which was relocated from Rugby on 2007-04-01) can be received on 60 kHz.
  • The JJY radio stations in Japan on 40/60 kHz.
  • The BPM radio station in Xi'an, China at 2.5, 5, 10 and 15 MHz
  • Swiss Broadcasts: The legal Swiss time can be picked up from the HBG longwave transmitter in Prangins on 75 kHz. The time code is compatible with that of the German DCF-77 transmitter.
  • French Broadcasts: Station TDF transmits timecodes on 162 kHz from a site near Allouis.

As a non-regulatory agency of the United States Department of Commerce’s Technology Administration, the National Institute of Standards (NIST) develops and promotes measurement, standards, and technology to enhance productivity, facilitate trade, and improve the quality of life. ... Longwave can also refer to the economics concept of Kondratiev waves, or to the rock band Longwave The Longwave radio broadcasting band is the range of frequencies between 148. ... WWVB is a special NIST time signal radio station in Fort Collins, Colorado, co-located with WWV. WWVB is the station that radio-controlled clocks throughout North America use to synchronize themselves. ... Binary-coded decimal (BCD) is a numeral system used in computing and in electronics systems. ... A solid-state, analog shortwave receiver Shortwave radio operates between the frequencies of 3,000 kHz and 30 MHz (30,000 kHz) [1] and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than those commonly... WWV Transmitter Building WWV is the callsign of NISTs shortwave radio station located in Fort Collins, Colorado. ... Horsetooth Rock, atop Horsetooth Mountain, is often used as a symbol of Fort Collins. ... WWVH is the callsign of NISTs shortwave radio time signal station in Kekaha, on the island of Kauai in the state of Hawaii. ... Kekaha is a census-designated place located in Kauai County, Hawaii. ... DCF77 is a longwave time signal radio station. ... Mainflingen is a small town of about 3800 inhabitants, part of the municipality Mainhausen (near Frankfurt am Main) in Hesse, Germany. ... For other uses, see Frankfurt (disambiguation). ... CHU is the callsign of a shortwave radio station founded in 1929 in Ottawa, Ontario, Canada. ... This article is about the capital city of Canada. ... The Anthorn transmitter is a VLF transmitter near Anthorn, Cumbria, which is used for transmitting orders to submarines on 19. ... A view of the tallest masts ( alternative view) The Rugby VLF transmitter is a large VLF transmission facility near the town of Rugby, Warwickshire in England. ... JJY is the callsign of a longwave time signal radio station similar to WWVB. The station is located in Japan, operated by a branch of the Japanese government known as the National Institute of Information and Communications Technology. ... BPM is the Peoples Republic of Chinas national time signal service, operated by the Chinese Academy of Sciences. ... Xian (Chinese: ; pinyin: ; Wade-Giles: Hsi-An; Postal System Pinyin: Sian), is the capital of Shaanxi province in China and a sub-provincial city. ... HBG transmitter in Prangins (emetteurs. ... Longwave can also refer to the economics concept of Kondratiev waves, or to the rock band Longwave The Longwave radio broadcasting band is the range of frequencies between 148. ... Télé Distribution Française, or TDF, is a time signal service, broadcast on shortwave radio by the French Laboratoire primaire du temps et des frequences (LPTF). ...

Loran clocks

Loran-C time signals may also be used for radio clock synchronization, by augmenting their highly accurate frequency transmissions with external measurements of the offsets of LORAN navigation signals against time standards. LORAN (LOng RAnge Navigation) is a terrestrial navigation system using low frequency radio transmitters. ...


GPS clocks

Many modern radio clocks use the Global Positioning System to provide more accurate time than can be obtained from these terrestrial radio stations. These GPS clocks combine time estimates from multiple satellite atomic clocks with error estimates maintained by a network of ground stations. Due to effects inherent in radio propagation and ionospheric spread and delay, GPS timing requires averaging over several periods of these phenomena. No GPS receiver directly computes time or frequency, rather they use GPS to discipline an oscillator, a quartz crystal in low-end navigation receivers, to an oven-compensated quartz in specialized units. For this reason, these devices are technically referred to as GPS disciplined oscillators. The Global Positioning System (GPS) is currently the only fully functional Global Navigation Satellite System (GNSS). ...


GPS units intended primarily for time measurement as opposed to navigation can be set to assume the antenna position is fixed; in this mode the device will average its position fixes so that after a day or so of operation it will know its position to within a few meters. Once it has averaged its position, it can then determine accurate time even if it can only pick up signals from one or two satellites.


Note that although any GPS receiver that is performing its primary navigational function must have an internal time reference accurate to a small fraction of a second, the displayed time on most consumer GPS units may not be as precise. This is because an inexpensive GPS unit typically has one CPU that is multitasking; the highest-priority task for the CPU is maintaining satellite lock, while updating the display gets a lower priority. Therefore, the displayed time of most consumer handheld GPS units will be accurate to around half a second — more than sufficient accuracy for most civil timekeeping purposes, but not for scientific applications such as astronomy.


For serious precision timekeeping, a more-specialized GPS device is needed. Some amateur astronomers, most notably those who time grazing lunar occultation events when the moon blocks the light from stars and planets, require the highest precision available for persons working outside large research institutions. The Web site of the International Occultation Timing Association [1] has detailed technical information about precision timekeeping for the amateur astronomer. A lunar occultation occurs when the Moon, moving along its orbital path, passes in front of a star or other celestial object, as seen by an observer (normally on the Earth). ...


GPS, Galileo and GLONASS: These satellite navigation systems have a caesium or rubidium atomic clock on each satellite, referenced to a clock or clocks on the ground. Some navigation units can serve as local time standards, with a precision of about one microsecond (µs). Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ... The Galileo positioning system, referred to simply as Galileo, is a proposed Global Navigation Satellite System, to be built by the European Satellite Navigation Industries for the European Union and European Space Agency (ESA) as an alternative to the United States operated Global Positioning System (GPS) and the Russian GLONASS... GLONASS GLONASS (Russian ГЛОНАСС; ГЛОбальная НАвигационная Спутниковая Система; Globalnaya Navigatsionnaya Sputnikovaya Sistema. ... It has been suggested that this article or section be merged into Global Navigation Satellite System. ... To help compare orders of magnitude of different times this page lists times between 10−6 seconds and 10−5 seconds (1. ...


However, GPS clocks are dependent on the goodwill of the United States government for the operation of the GPS satellite constellation. This is not acceptable for many critical non-US civilian and military systems, although it may be acceptable for many civilian purposes, as it is assumed by most users that the civilian GPS signal would not be switched off except in the event of a global crisis of unprecedented proportions.


The planned establishment of the Galileo positioning system by the EU (expected to be fully operational in 2010) is intended to provide a second source of time for GPS-compatible clocks that are also equipped to receive and decode the Galileo signals. The Galileo positioning system, referred to simply as Galileo, is a proposed Global Navigation Satellite System, to be built by the European Satellite Navigation Industries for the European Union and European Space Agency (ESA) as an alternative to the United States operated Global Positioning System (GPS) and the Russian GLONASS... This article or section does not adequately cite its references or sources. ...


The radio frequencies are set by the clocks and are precise standards, useful for adjusting receivers.


Other access

  • News radio: One method to access standard time is to listen to the news on radio. National radio news programs set their clocks to the transmissions from the standards departments of their respective countries. In the era when national broadcasting networks operated over point-to-point terrestrial microwave links, the time announcements were very precise. Today, however, satellite and digital networks often have latencies on the order of a second. In places where a car radio can receive more than one station broadcasting the same national news program, when switching between them one often either misses part of a word or hears part of the same word twice due to such variations. Also, once upon a time every radio station had a local full-time engineer who took considerable pride in keeping their clocks accurate; today many stations do not care as much about such details. Some stations still do provide highly accurate time beeps, such as WTIC (noted below), or WCBS (AM, 880 kHz) in New York City.
  • Interval signals: Many analog broadcast stations also transmit a distinctive tone or tones at the precise top of every hour, derived from an official source. Most well known is the Greenwich Time Signal, transmitted on BBC radio since 1924. In the US, WTIC in Hartford, Connecticut has broadcast the Morse code letter "V" every hour, on the hour, since 1943.
  • Attached to other broadcast stations: Broadcast stations in many countries have carriers precisely synchronized to a standard phase and frequency, such as the BBC Radio 4 longwave service on 198 kHz, and some also transmit subaudible timecode information, like the Radio France longwave transmitter on 162 kHz. Many digital radio and digital television schemes also include provisions for timecode transmission.
  • Teletext (TTX): Digital text pages embedded in television video also provide accurate time. Many modern TV sets and VCRs with TTX decoders can obtain accurate time from Teletext and set the internal clock.
  • FM Radio Data System (RDS): RDS can send a clock signal with sub-second precision, but not all RDS networks or stations using RDS send accurate time signals.
  • Digital Radio Mondial (DRM): DRM is able to send a clock signal, but one not as precise as GPS-Glonass clock signals.
  • Mobile telephones: Some mobile telephone technologies, such as Qualcomm's CDMA, are designed to distribute high-quality standard time signals (referenced to GPS in the case of CDMA). CDMA clocks are increasingly popular for providing reference time to computer networks. Their precision is nearly as good as that of GPS clocks, but since the signal comes from a nearby cell phone base station rather than a distant satellite, CDMA clocks generally work better inside buildings. So in many cases, when a GPS reference clock would require installing an outdoor antenna, a CDMA clock can overcome this requirement.
  • Network Time Protocol (NTP): The Network Time Protocol (NTP) is a protocol for synchronizing the clocks of computer systems over data networks such as the Internet, and has been in use since before 1985. It is designed particularly to resist the effects of variable latency, such as on the Internet. In practice, NTP is usually precise to within a few tens of milliseconds when used over the Internet. Many computer operating systems, set their clocks automatically using NTP. For operating systems lacking this functionality, third-party NTP client software is usually available.
  • Web sites: Some time references are available through Web sites. Time referenced to the U.S. NIST/USNO and French BIPM atomic clocks are available to the public on their Web sites (see below) with a time-of day display precise to within about 300 ms, depending on the round-trip travel time of IP packets between the client system and the server. Both NIST and BIPM use applets to provide this service: the applet running in your web browser exchanges packets with their server; both also display precision estimates based on network latency. On the dates when civil time changes, time-related sites on the Internet are often very slow to respond due to heavy usage; it is therefore wise to check one's clocks a day or two before the seasonal time change will occur.
  • Telephone: The U.S. clocks are also available by phone at +1 (303) 499-7111 (WWV), +1 (808) 335-4363 (WWVH), or +1 (202) 762-1401, +1 (202) 762-1069, and +1 (719) 567-6742 (USNO). Canadian clocks are available by phone at +1 (613) 745-1576 (English) and +1 (613) 745-9426 (French).


WTIC is a 50,000-watt AM radio station operating out of Hartford, Connecticut, broadcasting news and talk radio. ... WCBS (880 kHz. ... New York, NY redirects here. ... An interval signal is a characteristic sound or musical phrase used in international broadcasting and by some domestic broadcasters. ... Graph of the six pips The Greenwich Time Signal (abbreviated GTS) or BBC pips is a time code heard on some BBC radio stations at the start of the hour, most notably on Radio 4 and the World Service. ... The British Broadcasting Corporation, usually known as the BBC (and also informally known as the Beeb or Auntie) is the largest broadcasting corporation in the world in terms of audience numbers, employing 26,000 staff in the United Kingdom alone and with a budget of more than GB£4 billion... This article or section does not cite its references or sources. ... It has been suggested that Farnsworth method and Koch method be merged into this article or section. ... BBC Radio 4 is a British domestic radio station which broadcasts a wide variety of chiefly spoken-word programmes including news, drama, comedy, science and history. ... Longwave can also refer to the economics concept of Kondratiev waves, or to the rock band Longwave The Longwave radio broadcasting band is the range of frequencies between 148. ... Radio France is the French public service radio broadcaster. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Digital television (DTV) is a telecommunication system for broadcasting and receiving moving pictures and sound by means of digital signals, in contrast to analog signals used by analog (traditional) TV. DTV uses digital modulation data, which is digitally compressed and requires decoding by a specially designed television set, or a... A BBC Ceefax page from January 9, 2007. ... Qualcomm (NASDAQ: QCOM) is a wireless telecommunications research and development company based in San Diego, California. ... General Information Generically (as a multiplexing scheme), code division multiple access (CDMA) is any use of any form of spread spectrum by multiple transmitters to send to the same receiver on the same frequency channel at the same time without harmful interference. ... The Network Time Protocol (NTP) is a protocol for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. ... One millisecond is one-thousandth of a second. ... An operating system (OS) is a set of computer programs that manage the hardware and software resources of a computer. ... WWV Transmitter Building WWV is the callsign of NISTs shortwave radio station located in Fort Collins, Colorado. ... WWVH is the callsign of NISTs shortwave radio time signal station in Kekaha, on the island of Kauai in the state of Hawaii. ... Aerial view of USNO. The United States Naval Observatory (USNO) is one of the oldest scientific agencies in the United States. ... The English language is a West Germanic language that originates in England. ...

Time signal stations
  Longwave: DCF77 | HBG | JJY | MSF | TDF | WWVB
  Shortwave: BPM | CHU | RWM | WWV | WWVH | YVTO
  GNSS time transfer: Galileo | NAVSTAR GPS | GLONASS | Beidou
  Defunct time stations: OMA | VNG

Longwave can also refer to the economics concept of Kondratiev waves, or to the rock band Longwave The Longwave radio broadcasting band is the range of frequencies between 148. ... DCF77 is a longwave time signal radio station. ... HBG transmitter in Prangins (emetteurs. ... JJY is the callsign of a longwave time signal radio station similar to WWVB. The station is located in Japan, operated by a branch of the Japanese government known as the National Institute of Information and Communications Technology. ... The MSF time signal is a broadcast from the VLF transmitter Rugby near Rugby, Warwickshire based on time standards maintained by the British National Physical Laboratory. ... Télé Distribution Française, or TDF, is a time signal service, broadcast on shortwave radio by the French Laboratoire primaire du temps et des frequences (LPTF). ... WWVB is a special NIST time signal radio station in Fort Collins, Colorado, co-located with WWV. WWVB is the station that radio-controlled clocks throughout North America use to synchronize themselves. ... A solid-state, analog shortwave receiver Shortwave radio operates between the frequencies of 3,000 kHz and 30 MHz (30,000 kHz) [1] and came to be referred to as such in the early days of radio because the wavelengths associated with this frequency range were shorter than those commonly... BPM is the Peoples Republic of Chinas national time signal service, operated by the Chinese Academy of Sciences. ... CHU is the callsign of a shortwave radio station founded in 1929 in Ottawa, Ontario, Canada. ... RWM is the callsign of a shortwave radio station in Moscow, Russia. ... WWV Transmitter Building WWV is the callsign of NISTs shortwave radio station located in Fort Collins, Colorado. ... WWVH is the callsign of NISTs shortwave radio time signal station in Kekaha, on the island of Kauai in the state of Hawaii. ... YVTO is the callsign of the official time signal from the Juan Manuel Cagigal Naval Observatory in Caracas, Venezuela. ... GNSS - Global Navigation Satellite System In 1994 in a meeting of the ECAC, a satellite strategy was approved, with as targets: - firstly developing items for an European supplement on the current satellite systems, now called GNSS-1 - secondly designing and defining future satellite systems for civil use (called GNSS-2... The Galileo positioning system, referred to simply as Galileo, is a proposed Global Navigation Satellite System, to be built by the European Satellite Navigation Industries for the European Union and European Space Agency (ESA) as an alternative to the United States operated Global Positioning System (GPS) and the Russian GLONASS... The Global Positioning System (GPS) is currently the only fully functional Global Navigation Satellite System (GNSS). ... GLONASS GLONASS (Russian ГЛОНАСС; ГЛОбальная НАвигационная Спутниковая Система; Globalnaya Navigatsionnaya Sputnikovaya Sistema. ... The Beidou navigation system is a project by the Peoples Republic of China to develop an independent satellite navigation system. ... OMA was the callsgn of a Czech longwave time signal station (frequency: 50 kHz) . OMA was radiated from RKS Liblice 1 with a power of 5 kilowatts. ... VNG was Australias national time signal service, and operated on 2500, 5000, 8638, 12984, and 16000 kHz. ...

See also

A time signal is a visible, audible, mechanical, or electronic signal used as a reference to determine the time of day. ... Time transfer describes methods for transferring reference clock synchronization from one point to another, often over long distances. ... The Network Time Protocol (NTP) is a protocol for synchronizing the clocks of computer systems over packet-switched, variable-latency data networks. ... A speaking clock service is used for people who wish to know the correct and accurate time. ... Chip-Scale Atomic Clock Unveiled by NIST An atomic clock is a type of clock that uses an atomic resonance frequency standard to feed its counter. ... Graph of the six pips The Greenwich Time Signal (abbreviated GTS) or BBC pips is a time code heard on some BBC radio stations at the start of the hour, most notably on Radio 4 and the World Service. ...

External links


  Results from FactBites:
 
Reference.com/Encyclopedia/Radio clock (2239 words)
A radio clock is a clock that is synchronized by a time code bit stream transmitted by a radio transmitter connected to a time standard such as an atomic clock.
Such a clock may be synchronized to the time sent by a single transmitter, such as many national or regional time transmitters, or may use multiple transmitters, like the Global Positioning System.
Radio clocks synchronized to terrestrial time signals can usually achieve an accuracy of around 1 millisecond relative to the time standard, generally limited by uncertainties and variability in radio propagation.
Radio clock (359 words)
A radio clock is a clock that is synchronized by a time code transmitted by a radio transmitter connected to a time standard such as an atomic clock.
Radio clocks synchronized to terrestrial time signals can usually achieve an accuracy of around 1 millisecond relative to the time standard, generally limited by uncertainties and variability in radio propagation[?].
Loran-C time signals may also be used for radio clock synchronization, by augmenting their highly accurate frequency transmissions with external measurements of the offsets of LORAN navigation signals against time standards.
  More results at FactBites »

 
 

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