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117-842: DCF77 is controlled by the Physikalisch-Technische Bundesanstalt (PTB), Germany's national physics laboratory and transmits in continuous operation (24 hours). It is operated by Media Broadcast GmbH (previously a subsidiary of Deutsche Telekom AG ), on behalf of the PTB. With Media Broadcast GmbH, a temporal transmission availability of at least 99.7% per year or under 26.28 hours of annual downtime has been agreed upon. Most service interruptions are short-term disconnections of under two minutes. Longer lasting transmission service interruptions are generally caused by strong winds, freezing rain or snow-induced T-antenna movement. This manifests itself in electrical detuning of

234-418: A call sign (also known as a call name or call letters —and historically as a call signal —or abbreviated as a call ) is a unique identifier for a transmitter station . A call sign can be formally assigned by a government agency, informally adopted by individuals or organizations, or even cryptographically encoded to disguise a station's identity. The use of call signs as unique identifiers dates to

351-637: A general aviation flight would use the call sign November-niner-seven-eight-Charlie-Papa . However, in the United States a pilot of an aircraft would normally omit saying November , and instead use the name of the aircraft manufacturer or the specific model. At times, general aviation pilots might omit additional preceding numbers and use only the last three numbers and letters. This is especially true at uncontrolled fields (those without control towers) when reporting traffic pattern positions or at towered airports after establishing two-way communication with

468-428: A phase modulation of the carrier wave with a pseudorandom noise sequence of 512 bits length. Using cross-correlation the reproduced signal at the receiving end can be used to determine the beginning of the second markers much more accurately. The drawback of using phase-modulated time signals lies in the complex instrument grade receiving hardware required for using this time signal reception method. Using this method

585-490: A way that ensures compatibility with the transmission protocols of the warning messages. For decoding the weather forecast data a license is required. Since the bits previously reserved for the PTB are used, older radio clocks should not be affected by the weather data signal. The signal distribution contract between the PTB and the DCF77 transmitter operator Media Broadcast GmbH is periodically renewed. After negotiations in 2021

702-560: A "reunification in metrology". PTB took over parts of the ASMW (Office for Standardization, Metrology and Quality Control of the former German Democratic Republic), among them 400 employees, and the site Berlin-Friedrichshagen as additional field office (this has since been given up again). Other parts of the ASMW were integrated into the BAM . Despite a phase of staff reductions – after the strong expansion following reunification – PTB ranks today among

819-517: A 0-bit is inserted during second 59, and the special missing bit is transmitted during the leap second itself, second 60. Although the time code only includes two digits of year, it is possible to deduce two bits of century using the day of week. There is still a 400-year ambiguity, as the Gregorian calendar repeats weeks every 400 years, but this is sufficient to determine which years ending in 00 are leap years. The time zone bits can be considered

936-548: A Great Britain call sign prefix, 90 and MGY to commemorate the 90th anniversary of historic 1912 radio distress calls from MGY , the Marconi station aboard the famed White Star luxury liner RMS Titanic ). The late King Hussein of Jordan was issued a special amateur license number, JY1 , which would have been the shortest possible call sign issued by the Hashemite Kingdom of Jordan. When identifying

1053-488: A binary-coded representation of the UTC offset. Z1 set indicates UTC+2 , while Z2 indicates UTC+1 . The phase modulation generally encodes the same data as the amplitude modulation, but differs for bits 59 through 14, inclusive. Bit 59 (no amplitude modulation) is phase-modulated as a 0-bit. Bits 0–9 are phase modulated as 1 bits, and bits 10–14 are phase modulated as 0 bits. The civil protection warnings and weather information

1170-468: A call sign for broadcast stations; however, they are still required for broadcasters in many countries, including the United States. Mobile phone services do not use call signs on-air because the phones and their users are not licensed, instead the cell operator is the one holding the license. However, the U.S. still assigns a call sign to each mobile-phone spectrum license. In the United States, voluntary ships operating domestically are not required to have

1287-425: A call sign or license to operate VHF radios , radar or an EPIRB . Voluntary ships (mostly pleasure and recreational) are not required to have a radio. However, ships which are required to have radio equipment (most large commercial vessels) are issued a call sign. A directory of radio station call signs is called a callbook. Callbooks were originally bound books that resembled a telephone directory and contained

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1404-690: A convention that aircraft radio stations (and, by extension, the aircraft itself) receive call signs consisting of five letters. For example, all British civil aircraft have a five-letter registration beginning with the letter G, which can also serve for a call sign. Canadian aircraft have a call sign beginning with C–F or C–G, such as C–FABC. wing-in-ground-effect vehicles and hovercraft in Canada are eligible to receive C–Hxxx call signs, and ultralight aircraft receive C-Ixxx call signs. In days gone by, even American aircraft used five-letter call signs, such as KH–ABC, but they were replaced prior to World War II by

1521-406: A few times a day, but this practice is becoming very rare. Argentinian broadcast call signs consist of two or three letters followed by multiple numbers, the second and third letters indicating region. In Brazil, radio and TV stations are identified by a ZY, a third letter and three numbers. ZYA and ZYB are allocated to television stations; ZYI , ZYJ , ZYL , and ZYK designate AM stations; ZYG

1638-457: A geographical area, class of license, or identify a licensee as a visitor or temporary resident), and a 1-, 2-, or 3-letter suffix. In Australia, call signs are structured with a two letter prefix, a digit (which identifies geographical area), and a 2, 3 or 4 letter suffix. This suffix may be followed by a further suffix, or personal identifier, such as /P (portable), /M (mobile), /AM (aeronautical mobile) or /MM (maritime mobile). The number following

1755-597: A group of researchers dealing with nuclear fission. Later, he took over the specialist area "nuclear fission" in the Reich Research Council which supervised, from spring 1942 on, the German uranium project. Shortly after that, Hermann Göring subordinated the working group under the former PTR physicist Kurt Diebner to Division V for atomic physics at the PTR. Esau received the title "Authorized Representative of

1872-535: A more precise low frequency time distribution with less sensitivity to interferences. Phase modulation is however not used by many DCF77 receivers. The reason for this is the worldwide availability of the (precise time reference) signals transmitted by global navigation satellite systems like the Global Positioning System (GPS), GLONASS , Galileo and BeiDou . Due to the GPS signal structure and

1989-463: A one-letter company identifier (for instance, 'M' and two letters as a Marconi station ) was later added. By 1912, the need to quickly identify stations operated by multiple companies in multiple nations required an international standard ; an ITU prefix would be used to identify a country, and the rest of the call sign an individual station in that country. Merchant and naval vessels are assigned call signs by their national licensing authorities. In

2106-1374: A purely metrological specialist journal and does not publish any "Official Notes" any more. Presidents of PTB and of the Physikalisch-Technische Reichsanstalt Berlin-Charlottenburg: Employees of PTR and PTB were, among others: Udo Adelsberger, Walther Bothe , Kurt Diebner , Gerhard Wilhelm Becker, Ernst Engelhard, Abraham Esau , Ernst Gehrcke , Hans Geiger , Werner Gitt , Eugen Goldstein , Ernst Carl Adolph Gumlich, Hermann von Helmholtz , Fritz Hennin, Friedrich Georg Houtermans , Max Jakob , Hellmut Keiter, Dieter Kind, Hans Otto Kneser, Friedrich Wilhelm Kohlrausch, Wilhelm Kösters, Bernhard Anton Ernst Kramer, Johannes Kramer, August Kundt , Max von Laue , Carl von Linde , Leopold Loewenherz, Otto Lummer , Walter Meidinger, Walther Meißner , Franz Mylius, Walther Hermann Nernst , Robert Ochsenfeld , Friedrich Paschen , Matthias Scheffler, Adolf Scheibe, Harald Schering , Reinhard Scherm, Johannes Stark , Ulrich Stille, Ida Tacke , Gotthold Richard Vieweg, Richard Wachsmuth, Emil Warburg , Wilhelm Wien . 52°17′43″N 10°27′49″E  /  52.29528°N 10.46361°E  / 52.29528; 10.46361 Call sign In broadcasting and radio communications ,

2223-484: A similar brand, and the name of a broadcast station for legal purposes is normally its internationally recognised ITU call sign. Some common conventions are followed in each country. Broadcast stations in North America generally use call signs in the international series. In the United States of America, they are used for all FCC-licensed transmitters. The first letter generally is K for stations located west of

2340-521: A station by voice, the call sign may be given by simply stating the letters and numbers, or using a phonetic alphabet . Some countries mandate the use of the phonetic alphabet for identification. In wartime, monitoring an adversary's communications can be a valuable form of intelligence. Consistent call signs can aid in this monitoring, so in wartime, military units often employ tactical call signs and sometimes change them at regular intervals. In peacetime, some military stations will use fixed call signs in

2457-519: A time basis for this, PTB operates several atomic clocks (currently two cesium clocks and, since 1999 and 2009, respectively, two cesium fountain clocks ). By order of PTB, the synchronization of clocks via radio is performed via the time signal transmitter DCF77 operated by Media Broadcast. Computers which are connected to the Internet can obtain the time also via the three public NTP time servers operated by PTB. In Berlin-Adlershof , PTB operates

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2574-557: Is 2 × 10 over a 24-hour period and 2 × 10 over 100 days, with a deviation in phase with respect to UTC that never exceeds 5.5 ± 0.3 microseconds . The four German primary caesium (fountain) atomic clocks (CS1, CS2, CSF1 and CSF2) in use by the PTB in Braunschweig ensure significantly less long term clock drift than the atomic clocks used in the DCF77 facility in Mainflingen. With the aid of external corrections from Braunschweig

2691-451: Is generated by a 9-bit linear feedback shift register (LFSR), repeats every second, and begins with 00000100011000010011100101010110000…. A software implementation of a Galois LFSR can generate the full chip sequence: Each time code bit to be transmitted is exclusive-ored with the LFSR output. The final chipped sequence is used to modulate the transmitter phase. During 0 chips the carrier

2808-632: Is generated from local atomic clocks that are linked with the German master clocks at the PTB in Braunschweig . The DCF77 time signal is used for the dissemination of the German national legal time to the public. Radio clocks and watches have been very popular in Europe since the late 1980s and, in mainland Europe, most of them use the DCF77 signal to set their time automatically. The DCF77 longwave radio emission offers penetration into buildings and

2925-411: Is mixed with a 512-bit pseudo-random chip sequence and encoded on the carrier using ±15.6° phase-shift keying . The chip sequence contains equal amounts of each phase, so the average phase remains unchanged. Each chip spans 120 cycles of the carrier, so the exact duration is cycles 15500 through 76940 out of 77500. The last 560 cycles (7.23 ms) of each second are not phase-modulated. The chip sequence

3042-506: Is not included in the phase-modulated data. With a relatively high power of 50 kW , the DCF77 transmissions can reliably be received in large parts of Europe, as far as 2,000 km (1,200 mi) from the transmitter in Mainflingen. Within this range the signal strength of the DCF77 signal as specified by the Physikalisch-Technische Bundesanstalt (PTB) is ≥ 100 μV/m. This signal strength assessment

3159-767: Is not issued to such stations due to their unlicensed nature. Also, wireless network routers or mobile devices and computers using Wi-Fi are unlicensed and do not have call signs. On some personal radio services, such as CB, it is considered a matter of etiquette to create one's own call sign, which is called a handle (or trail name). Some wireless networking protocols also allow SSIDs or MAC addresses to be set as identifiers, but with no guarantee that this label will remain unique. Many mobile telephony systems identify base transceiver stations by implementing cell ID and mobile stations (e.g., phones) by requiring them to authenticate using international mobile subscriber identity (IMSI). International regulations no longer require

3276-684: Is repeated every minute. Since 2003, fourteen previously unused bits of the time code have been used for civil defence emergency signals. This is an experimental service, aimed to one day replace the German network of civil defence sirens . Since 22 November 2006 the DCF77 transmitter uses bits 1–14 to transmit warning messages and weather information. Under responsibility of the German Federal Office of Civil Protection and Disaster Assistance (the German Bundesamt für Bevölkerungsschutz und Katastrophenhilfe , BBK), warnings to

3393-627: Is the metrological specialist journal and the official information bulletin of PTB. It is published four times a year and contains original scientific articles as well as overview articles on metrological subjects from PTB's fields of activity. Each volume focuses on a main topic. As an official information bulletin, the journal stands in a long tradition which goes back to the beginnings of the Physikalisch-Technische Reichsanstalt (Imperial Technical Physical Institute - PTR, founded in 1887). Until 2014, "PTB-Mitteilungen"

3510-709: Is the national metrology institute of the Federal Republic of Germany , with scientific and technical service tasks. It is a higher federal authority and a public-law institution directly under federal government control, without legal capacity, under the auspices of the Federal Ministry for Economic Affairs and Climate Action . Together with NIST in the USA and the NPL in Great Britain, PTB ranks among

3627-409: Is transmitted with a +15.6° phase advance, while during 1 chips it is transmitted with a −15.6° phase lag. In lieu of the special minute marker used in the amplitude code, bit 59 is transmitted as an ordinary 0-bit, and the first 10 bits (seconds 0–9) are transmitted as binary 1. When compared to amplitude modulation, phase modulation makes better use of the available frequency spectrum and results in

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3744-683: Is used for shortwave stations; ZYC , ZYD , ZYM , and ZYU are given to FM stations. In Australia, broadcast call signs are optional, but are allocated by the Australian Communications and Media Authority and are unique for each broadcast station. Most European and Asian countries do not use call signs to identify broadcast stations, but Japan, South Korea, Indonesia, the Philippines and Taiwan do have call sign systems. Spanish broadcasters used call signs consisting of E followed by two letters and up to three digits until

3861-544: The Dominion of Newfoundland government retain their original VO calls. In Mexico, AM radio stations use XE call signs (such as XEW-AM ), while the majority of FM radio and television stations use XH . Broadcast call signs are normally four or five alpha characters in length, plus the -FM , -TV , or -TDT suffix where applicable. In South America call signs have been a traditional way of identifying radio and TV stations. Some stations still broadcast their call signs

3978-1681: The Mississippi River and W for eastern stations. Historic exceptions in the east include KYW in Philadelphia and KDKA in Pittsburgh, while western exceptions include WJAG in Norfolk, Nebraska , and WOAI in San Antonio. All new call signs have been four-character for some decades, though there are historical three-character call letters still in use today, such as KSL in Salt Lake City; KOA in Denver; WHO in Des Moines; WWJ and WJR in Detroit; WJW-TV in Cleveland ; WBT in Charlotte; WBZ in Boston; WSM in Nashville; WGR in Buffalo; KFI ; KNX and KHJ in Los Angeles; and WGN , WLS and WLS-TV in Chicago. American radio stations announce their call signs (except for rare cases in which would interfere with

4095-598: The Physikalisch-Technische Bundesanstalt (PTB) measured standard deviations of ± 2 to 22 microseconds between UTC (PTB) and UTC (DCF77), depending on the time in the day and season. This was done in Braunschweig located 273  km (170  mi ) from the transmitter in Mainflingen. Normal low cost consumer grade DCF77 receivers solely rely on the amplitude-modulated time signals and use narrow band receivers (with 10 Hz bandwidth) with small ferrite loopstick antennas and circuits with non optimal digital signal processing delay and can therefore only be expected to determine

4212-508: The 162 kHz 800 kW TDF time signal broadcast from France), DCF77 marks seconds by reducing carrier power for an interval beginning on the second. The duration of the reduction is varied to convey one bit of time code per second, repeating every minute. The carrier is synchronized so the rising zero-crossing occurs on the second. All modulation changes also occur at rising zero-crossings. The DCF77 signal uses amplitude-shift keying to transmit digitally coded time information by reducing

4329-518: The 1960s when flight radio officers (FRO) were no longer required on international flights. The Russian Federation kept FROs for the Moscow-Havana run until around 2000. Currently, all signs in aviation are derived from several different policies, depending upon the type of flight operation and whether or not the caller is in an aircraft or at a ground facility. In most countries, unscheduled general aviation flights identify themselves using

4446-418: The DCF77 signal strength is much higher. As an example, under 500 km (300 mi) from the transmitter in Mainflingen the expected signal strength of the ground wave is ≥ 1 mV/m. Depending on signal propagation and multiple reflections (hops) and local interference the DCF77 signal can sometimes be received further away (see tropospheric propagation ). This is associated with a significant decrease in

4563-467: The Experimental and Research Reactor Braunschweig. This reactor served in particular as neutron source for fundamental research , not for the investigation of nuclear energy. PTB dealt with this controversial subject from 1977 to 1989, above all due to the fact that the task "long-term management and disposal of radioactive waste" had been assigned to it. Later on, this field of work passed over to

4680-635: The Federal Constitutional Court has declared the use of such voting machines to be inadmissible. Weapons which may be carried with the Minor Firearms Certificate, i.e. weapons for shooting blanks or irritants and weapons used as signaling devices, require a PTB test mark for their approval. Occasionally, these weapons are also jointly referred to as "PTB weapons" and bear the PTA or PTB proof mark F (see also: Act on

4797-540: The Franco-German War (1870/71), the stagnation in scientific mechanics and in the science of instruments had become evident in Germany. Increasingly precise metrology was required for industrial production. A considerable impact on the initiative for the founding of a state institute for metrology in order to promote the national interests of the economy, of trade and of the military was made – in particular – by

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4914-610: The Imperial Diet approved the first annual budget of the PTR – the founding of the first state-financed, university-external, major research institution in Germany which combined free fundamental research with services for industry. Werner von Siemens ceded private land in Berlin-Charlottenburg to the Reichsanstalt. Hermann von Helmholtz became its first president. At that time, 65 persons were employed at

5031-601: The Kuratorium and took over its competences himself. Jewish employees and critics of the NSDAP (such as Max von Laue ) were dismissed. After World War II , Von Laue participated in the re-founding of PTB. Albert Einstein , who had been thrown out of the Kuratorium already before its dissolution, broke ties to PTR/PTB. Under Stark and – after 1939 – under his successor Abraham Esau , the PTR strongly dedicated itself to armament research. A newly founded laboratory for acoustics

5148-511: The MLS (Metrology Light Source) electron storage ring for calibrations in the field from the infrared (THz) to the extreme ultraviolet (EUV). Department Q.5 "Technical Cooperation" realizes projects of the German and international development cooperation in the field of quality infrastructure. These activities promote competitiveness as well as environmental protection and consumer protection in developing countries and in countries in transition. One of

5265-412: The PTB and Media Broadcast GmbH agreed to continue the dissemination of the German national legal time for the next 10 years. In order to improve the reliability of the broadcast and also the ease of maintenance by the operator, Media Broadcast GmbH has announced that it will build a second remote-controllable high-performance transmitter in 2022. The facilities will then be completely duplicated on site. In

5382-535: The PTB was dedicated at that time to the so-called New Physics . This included, among other things, research on the newly discovered X-rays, new atomic models, Einstein's Special Theory of Relativity, quantum physics (based on the already mentioned work on the black-body radiator), and the investigation of the properties of the electron. Scientists like Hans Geiger, who established the first radioactivity laboratory of PTR, were involved in this research work. Walther Meißner succeeded in liquefying helium , which led him to

5499-433: The PTB. This control unit, which is housed in an air conditioned room of the transmitting station, is shielded against high-frequency interferences and controlled from Braunschweig. For reasons of operational reliability, the control signal is generated by three independent control channels all equipped with their own caesium atomic clock . In addition a rubidium atomic clock is available on site. To avoid incorrect emissions

5616-489: The PTR President Emil Warburg discontinued the subdivision into a physical and a technical division and re-structured the PTR into divisions for optics, electricity and heat, with sub-divisions of a purely scientific and technical nature. Under Warburg's successor Walther Nernst , the Reichsanstalt für Maß und Gewicht (Imperial Institute for Weights and Measures – RMG) was, in addition, integrated into

5733-517: The PTR successor. In 1948, Wilhelm Kösters, who had been the director of Division 1 in Berlin for many years, became its first president. Many former PTR employees from Berlin , Weida and Heidelberg followed him to Braunschweig. The new institute was named ꞋꞋPhysikalisch-Technische AnstaltꞋꞋ (PTA) and, since 1 April 1950, ꞋꞋPhysikalisch-Technische BundesanstaltꞋꞋ. In 1953, the West Berlin PTR

5850-400: The PTR was also closely connected with Max Planck. To decide whether electricity or gas would be more economic for street lighting in Berlin, the PTR was to develop a more precise standard for luminous intensity. For this purpose, in 1895, Otto Lummer and Wilhelm Wien developed the first cavity radiator for the practical generation of thermal radiation. Their measurements of the spectrum of

5967-498: The PTR was also closely connected with the armament industry of the Third Reich. Since exact measures are a basic requirement for the manufacture of military equipment, the PTR gained a key role in armament production and defense. The extent to which the PTR was also involved in the German nuclear weapons project is controversial. It is, however, known that – prior to his time as PTR president – Abraham Esau conducted – until 1939 –

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6084-408: The PTR – among them more than a dozen physicists – who disposed of a budget of 263,000 Reichsmarks. In its first decades, the PTR succeeded in attracting important scientists and members of the Kuratorium as employees, among them Wilhelm Wien , Friedrich Kohlrausch , Walther Nernst , Emil Warburg , Walther Bothe , Albert Einstein and Max Planck . The first outstanding scientific achievement at

6201-514: The PTR. A newly established division took over from the RMG extensive tasks with regard to the verification system as well as the measurements of length, weight and volume associated with the verification system. The profile of tasks was thus similar to that of PTB today: Through its own research and development, and through services building on this, the PTR was to ensure the uniformity of metrology and its continuous further development. As regards contents,

6318-608: The Proof Testing of Arms and Ammunition). The main site of PTB is in Braunschweig (Lehndorf-Watenbüttel). Other sites are in Berlin-Charlottenburg and Berlin-Adlershof . Divisions 1 to 6 as well as Division Q are located in Braunschweig. In Berlin-Charlottenburg Divisions 7 and 8 are located, and in Berlin-Adlershof the two electron storage rings BESSY II and the Metrology Light Source (MLS);

6435-601: The Reichsmarschall for Nuclear Physics", a post which he, however, ceded to Walther Gerlach already at the end of 1943. To escape the bombing raids of the allies , the PTR was, in 1943, relocated at the initiative of the president and Thuringian privy councillor Abraham Esau to different places in Germany (for example to Weida and Ronneburg in Thuringia and to Bad Warmbrunn in Lower Silesia). During

6552-627: The UTC Time Dissemination Service Accuracy was ≤ 4.3 ns, computed by accumulating samples over the previous 12 months and exceeding the ≤ 30 ns target). The time is represented in binary-coded decimal . It represents civil time, including summer time adjustments. The time transmitted is the time of the following minute; e.g. during December 31 23:59, the transmitted time encodes January 1 00:00. The first 20 seconds are special flags. The minutes are encoded in seconds 21–28, hours during seconds 29–34, and

6669-754: The amateur radio service as a citizen of their country has been assigned there. The first amateur radio call sign assigned to the International Space Station was NA1SS by the United States. OR4ISS (Belgium), DP0ISS (Germany), and RS0ISS (Russia) are examples of others, but are not all-inclusive of others also issued. Broadcasters are allocated call signs in many countries. While broadcast radio stations will often brand themselves with plain-text names, identities such as " Cool FM ", " Rock 105" or "the ABC network" are not globally unique. Another station in another city or country may (and often will) have

6786-479: The amplitude of the carrier to 15% of normal (−16½  dB ) for 0.1 or 0.2 seconds at the beginning of each second. A 0.1 second reduction (7750 cycles of the 77500 Hz carrier amplitude) denotes a binary 0; a 0.2 second reduction denotes a binary 1. As a special case, the last second of every minute is marked with no carrier power reduction. There was also a Morse code station identification until 2006, sent during minutes 19, 39 and 59 of each hour, however this

6903-486: The amplitude-modulated time signals with accompanying antennas oriented tangential to the transmitter's antenna in Mainflingern to ensure the best possible interference-free time signal reception at fixed locations, can achieve a practical accuracy uncertainty better than ± 2 milliseconds. In addition to the amplitude-modulated time signal transmission this information is also transmitted since June 1983 by DCF77 via

7020-569: The antenna resonance circuit and hence a measurable phase modulation of the received signal. When the maladjustment is too large, the transmitter is taken out of service temporarily. In the year 2002, almost 99.95% availability, or just over 4.38 hours of downtime, was realized. The timestamp sent is either in Coordinated Universal Time (UTC)+1 or UTC +2 depending on daylight saving time . The highly accurate 77.5 kHz ( 3 868 .289 7806  m wavelength) carrier signal

7137-687: The attacks on Berlin, the buildings of the PTR were heavily damaged. In 1945, the Reichsanstalt was virtually destroyed and the few departments which still existed were scattered all over the country. Approximately from 1947 on, successor institutes were developed in addition to the PTR in Berlin-Charlottenburg, i.e. one in East Berlin – for the Soviet Occupation Zone – and one in the Bizone – and later Trizone . With

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7254-401: The beginning of a second with a practical accuracy uncertainty of ± 0.1 second. This is sufficient for radio controlled low cost consumer grade clocks and watches using standard-quality quartz clocks for timekeeping between daily DCF77 synchronization attempts, as they will be most accurate immediately after a successful synchronization and will become less accurate from that point forward until

7371-410: The black-body radiation were so precise that they contradicted Wien's radiation law at long wavelengths. This caused one of the cornerstones of classical physics of that time to totter. The measurements prompted a decisive impulse on the part of Max Planck to divide thermal radiation – in an "act of despair", as he later declared – into separate portions. This was the birth of quantum physics. In 1914,

7488-509: The broad public. In addition, PTB publishes the scientific information bulletin PTB-news three times a year. On four pages, it contains news from the fields of work "Fundamentals of Metrology", "Applied Metrology for Industry", "Medicine and Environmental Protection", "Metrology for Society" and "International Affairs". The PTB-news are published in German and in English. PTB-Mitteilungen

7605-539: The broadcast of very long works of classical or opera music) at or near the top of each hour, as well as sign-on and sign-off for stations that do not broadcast 24 hours. Beginning in the early 2000s, digital subchannels were assigned a -DT# suffix, where # is the subchannel (starting with the number 2). In Canada, the publicly owned Canadian Broadcasting Corporation uses the prefix CB ; privately owned commercial broadcast stations use primarily CF and CH through CK prefixes; and four stations licensed to St. John's by

7722-551: The call sign corresponding to the aircraft's registration number (also called N-number in the U.S., or tail number ). In this case, the call sign is spoken using the International Civil Aviation Organization (ICAO) phonetic alphabet . Aircraft registration numbers internationally follow the pattern of a country prefix, followed by a unique identifier made up of letters and numbers. For example, an aircraft registered as N978CP conducting

7839-464: The case of pure space waves the receiver cannot compensate for the fluctuations since these are the result of the changing altitude of the reflecting and bending layer of the ionosphere. Similar problems arise where ground and skywaves overlap. This field is not constant but changes in the course of the day between approximately 600 to 1,100  km (400 to 700  mi ) from the transmitter position. Corrected instrument grade DCF77 receivers, using

7956-1074: The case of states such as Liberia or Panama , which are flags of convenience for ship registration, call signs for larger vessels consist of the national prefix plus three letters (for example, 3LXY, and sometimes followed by a number, e.g. 3LXY2). United States merchant vessels are given call signs beginning with the letters "W" or "K" while US naval ships are assigned call signs beginning with "N". Originally, both ships and broadcast stations were assigned call signs in this series consisting of three or four letters. Ships equipped with Morse code radiotelegraphy, or life boat radio sets, aviation ground stations, broadcast stations were given four-letter call signs. Maritime coast stations on high frequency (both radiotelegraphy and radiotelephony) were assigned three-letter call signs. As demand for both marine radio and broadcast call signs grew, gradually American-flagged vessels with radiotelephony only were given longer call signs with mixed letters and numbers. Leisure craft with VHF radios may not be assigned call signs, in which case

8073-443: The control unit of DCF77 in Mainflingen is expected to neither gain nor lose a second in approximately 300,000 years. In theory, a DCF77 controlled external clock should be able to synchronize to within one half of the period of the transmitted 77.5 kHz carrier frequency of the DCF77 signal, or within ± 6.452 × 10 s or ± 6.452 microseconds. Due to the propagation process, phase and/or frequency shifts observed in received signals

8190-517: The country/territory identifier is, instead, appended to the call sign; e.g., W1AW/VE4, or VE3XYZ/W1. Special call signs are issued in the amateur radio service either for special purposes, VIPs, or for temporary use to commemorate special events. Examples include VO1S ( VO1 as a Dominion of Newfoundland call sign prefix, S to commemorate Marconi 's first trans-Atlantic message, a single-character Morse code S sent from Cornwall , England to Signal Hill, St. John's in 1901) and GB90MGY ( GB as

8307-515: The current American system of civilian aircraft call signs (see below). One exception to the parallelism between registration and call sign is ultralight airplanes in France, who are not obliged to carry a radio and indeed often don't. Radio call signs used for communication in crewed spaceflight are not formalized or regulated to the same degree as for aircraft. The three nations currently launching crewed space missions use different methods to identify

8424-425: The date during seconds 36–58. Two flags warn of changes to occur at the end of the current hour: a change of time zones, and a leap second insertion. These flags are set during the hour up to the event. This includes the last minute before the event, during which the other time code bits (including the time zone indicator bits) encode the time of the first minute after the event. In the event of an added leap second,

8541-743: The designated call sign, so F13C would be the Charlie fire team . Unused suffixes can be used for other call signs that do not fall into the standard call sign matrix, for example the unused 33A call sign is used to refer to the company sergeant major . No call signs are issued to transmitters of the long-range navigation systems ( Decca , Alpha , Omega ), or transmitters on frequencies below 10 kHz , because frequencies below 10 kHz are not subject to international regulations. In addition, in some countries lawful unlicensed low-power personal and broadcast radio signals ( Citizen's Band (CB), Part 15 or ISM bands ) are permitted; an international call sign

8658-603: The determination of fundamental and natural constants; the realization, maintenance and dissemination of the legal units of the SI; and safety technology. This spectrum of tasks is supplemented by services such as the German Calibration Service ( Deutscher Kalibrierdienst , DKD) and by metrology for the area regulated by law, metrology for industry, and metrology for technology transfer. As the basis for its tasks, PTB conducts fundamental research and development in

8775-480: The discovery of the superconductivity of a series of metals. In this connection, he recognized some years later – together with his colleague Robert Ochsenfeld – that superconductors have the property of displacing from their interior a magnetic field which has been applied from the outside – the Meißner-Ochsenfeld Effect. With the appointment of Johannes Stark as president on 1 May 1933,

8892-563: The economy and politics. PTB is composed of the following nine divisions: Two essential factors which led to the founding of the Physikalisch-Technische Reichsanstalt (Imperial Physical Technical Institute – PTR) were the determination of internationally valid, uniform measures in the Meter Convention of 1875 and the dynamic industrial development in Germany in the 19th century. Already in

9009-438: The establishment of a state institute in order to solve this problem. The reason for this was that such a task was scientifically too ambitious for industrial laboratories and, in addition, not profitable for them, and classical training institutes were not suited for the task either. Among the supporters of the "Schellbach Memorandum" (named after its author Karl Heinrich Schellbach) ranked, among others, Hermann von Helmholtz and

9126-427: The field of metrology in close cooperation with universities, other research institutions, and industry. PTB employs approximately 1900 staff members. It has a total budget of approx. €183 million at its disposal; in 2012, approx. €15 million was, in addition, canvassed as third-party funds for research projects. The Units and Time Act entrusts PTB also especially with the dissemination of legal time in Germany. To have

9243-506: The field of telecommunication and information technology, and at radio and TV stations are radio-controlled by DCF77 as well as tariff change-over clocks of energy supply companies and clocks in traffic-light facilities. The DCF77 station signal carries an amplitude-modulated, pulse-width coded 1 bit/s data signal. The same data signal is also phase modulated onto the carrier using a 512 bit long pseudorandom sequence ( direct-sequence spread spectrum modulation). The transmitted data signal

9360-563: The first two digits indicate the nominal length of the boat in feet. For example, Coast Guard 47021 refers to the 21st in the series of 47-foot motor lifeboats. The call sign might be abbreviated to the final two or three numbers during operations, for example: Coast Guard zero two one . Originally aviation mobile stations (aircraft) equipped with radiotelegraphy were assigned five-letter call signs (e.g. KHAAQ). Land stations in aviation were assigned four-letter call signs (e.g. WEAL – Eastern Air Lines, NYC.) These call signs were phased out in

9477-434: The ground and space radio stations; the United States uses either the names given to the space vehicles, or else the project name and mission number. Russia traditionally assigns code names as call signs to individual cosmonauts , more in the manner of aviator call signs , rather than to the spacecraft. The only continuity in call signs for spacecraft have been the issuance of "ISS"-suffixed call signs by various countries in

9594-448: The ideology of National Socialism found its way into the PTR. The convinced advocate of a German Physics terminated diverse research projects on issues of modern physics to which he referred to as "Jewish", among them, in particular, works on quantum physics and on the theory of relativity . Stark also tried to enforce the " Führer principle " (Führerprinzip) at the PTR: in 1935, he dissolved

9711-509: The international series. The United States Army uses fixed station call signs which begin with W , such as WAR, used by U.S. Army Headquarters. Fixed call signs for the United States Air Force stations begin with A , such as AIR, used by USAF Headquarters. The United States Navy , United States Marine Corps , and United States Coast Guard use a mixture of tactical call signs and international call signs beginning with

9828-465: The jurisdiction of a foreign government, an identifying station pre-pends the call sign with the country prefix and number of the country/territory from which the operation is occurring. For example, W4/G3ABC would denote a licensed amateur from the United Kingdom who is operating in the fourth district of the United States. There are exceptions; in the case of U.S./Canadian reciprocal operations,

9945-480: The landline railroad telegraph system. Because there was only one telegraph line linking all railroad stations , there needed to be a way to address each one when sending a telegram . In order to save time, two-letter identifiers were adopted for this purpose. This pattern continued in radiotelegraph operation; radio companies initially assigned two-letter identifiers to coastal stations and stations on board ships at sea. These were not globally unique, so

10062-572: The larger bandwidth available, the GPS reception would, in principle, achieve an uncertainty of the time transmission that is lower by at least one order of magnitude than the uncertainty that can be achieved with DCF77 phase modulation receiving hardware (GPS time is accurate to about ± 10 to 30 nanoseconds and the Galileo April, May, June 2021 Quarterly Performance Report by the European GNSS Service Centre reported

10179-555: The largest national metrology institutes in the world. As such, it is in charge of the realization and dissemination of the physical units and promotes the worldwide uniformity of metrology. The PTB magazine maßstäbe , which is published approximately once a year, can be subscribed to free of charge or it can be downloaded from the Internet pages of PTB. It contains articles about the quantities of physics. These articles are intended to be generally understandable and informative for

10296-606: The last GDR years; the name already indicates that this office of the GDR had more extensive tasks than PTB in the Federal Republic of Germany (FRG), namely additional tasks in the field of standardization and quality assurance and in the area of activity of the Bundesanstalt für Materialforschung und -prüfung (BAM). The young PTB grew rapidly in the years after its founding – both in terms of staff and in terms of financial resources. Not only its scientific metrological profile

10413-483: The late 1970s. Portugal had a similar system, their callsigns beginning with C ; these also ceased to be used in the 1970s. Britain has no call signs in the American sense, but allows broadcast stations to choose their own trade mark call sign up to six words in length. Amateur radio call signs are in the international series and normally consist of a one or two character prefix, a digit (which may be used to denote

10530-914: The latter is located in the Willy Wien Laboratory. PTB is headed by the Presidential Board in Braunschweig, which is composed of the President, the Vice-President and a further member. Another executive committee is the Directors' Conference, with the Presidential Board and the Heads of the Divisions as members. PTB is advised by the Kuratorium (PTB's Advisory Board), which is composed of representatives from science,

10647-530: The leading metrology institutes in the world. As the National Metrology Institute of Germany, PTB is Germany's highest and only authority in terms of correct and reliable measurements. The Units and Time Act Bundesgesetzblatt (Federal Law Gazette), volume 2008, part I, No. 28, p. 1185 ff., 11 July 2008] assigns all tasks which are related with the realization and dissemination of the units to PTB. All legally relevant aspects regarding

10764-464: The letter N . In the British military , tactical voice communications use a system of call signs of the form letter-digit-digit . Within a standard infantry battalion, these characters represent companies, platoons and sections respectively, so that 3 Section, 1 Platoon of F Company might be F13. In addition, a suffix following the initial call sign can denote a specific individual or grouping within

10881-412: The mathematician and physicist Wilhelm Foerster . Prussia, however, initially rejected their demands. Not until some years later were Werner von Siemens and Hermann von Helmholtz, the "founding fathers" of the PTR, able to make their vision – the establishment of a research institute which was to link scientific, technical and industrial interests in an optimal way – come true. Finally, on 28 March 1887,

10998-430: The name and addressees of licensed radio stations in a given jurisdiction (country). Modern Electrics published the first callbook in the United States in 1909. Today, the primary purpose of a callbook is to allow amateur radio operators to send a confirmation post card, called a QSL card to an operator with whom they have communicated via radio. Callbooks have evolved to include on-line databases that are accessible via

11115-484: The name of the vessel is used instead. Ships in the US still wishing to have a radio license are under FCC class SA: "Ship recreational or voluntarily equipped." Those calls follow the land mobile format of the initial letter K or W followed by one or two letters followed by three or four numbers (such as KX0983 or WXX0029). U.S. Coast Guard small boats have a number that is shown on both bows (i.e. port and starboard) in which

11232-516: The next synchronization. Some DCF77 controlled consumer grade quartz movements promote accurate time keeping by synchronizing and correcting their time automatically more than once spread over a day. Network Time Protocol time servers display the reference ID (REFID) .DCFa. (amplitude modulation) or .DCFp. (phase modulation) when a standard DCF77 time receiver is used as the reference time source. Physikalisch-Technische Bundesanstalt The Physikalisch-Technische Bundesanstalt ( PTB )

11349-422: The output of these three channels are compared in two electronic switch circuits on site. Output for transmission is only generated when at least two of the three channels are in agreement. Via the public telephone network operational data of the control unit can be called up with the aid of a telecontrol system. Furthermore, the carrier phase time and the states of the second markers are compared in Braunschweig with

11466-422: The past the PTB expressed it will initialize new negotiations if modernization activities at the transmitting station to improve the signal reception reliability throughout Europe are deemed necessary. The call sign DCF77 stands for D = Deutschland (Germany), C = long wave signal, F = Frankfurt am Main as the umbrella regional unit, 77 = frequency: 77.5 kHz. Like most longwave time transmitters (akin to

11583-477: The population can be transmitted using these 14 bits. As a further extension of the information content transmitted by DCF77, appropriately equipped radio clocks can provide a four-day weather forecast for 60 different regions in Europe. The forecast data is provided by and under responsibility of the Swiss company Meteo Time GmbH and is transferred in a proprietary transfer protocol. The same 14 bits are employed in

11700-442: The practical obtainable accuracy is lower than originally realized with the atomic clocks at the place of transmission. As with any time signal radio transmitter the precise establishment of time is affected by the distance to the transmitter, as the time signal propagates to a time signal receiver at the speed of light . For a DCF77 receiver located 1,000  km (600  mi ) away from the DCF77 transmitter, due to transit delay

11817-400: The prefix is normally a single number (0 to 9). Some prefixes, such as Djibouti's (J2), consist of a letter followed by a number. Hence, in the hypothetical Djibouti call sign, J29DBA, the prefix is J2 , the number is 9 , and the suffix is DBA . Others may start with a number followed by a letter, for example, Jamaican call signs begin with 6Y. When operating with reciprocal agreements under

11934-410: The receiver will be set more than 3 milliseconds late. Such a small deviation will seldom be of interest and if desired instrument grade time receivers can be corrected for transit delay. Further inaccuracies may be caused by the type of wave the receiver records. If pure ground wave reception is anticipated and the reception location is permanent a constant may be included in the calculation, while in

12051-507: The setpoints specified by the PTB's atomic master clocks that provide the UTC (PTB). Of these atomic clocks the CS2 atomic clock in Braunschweig provides the German national legal time standard, and can be used as a highly accurate frequency standard. If there are deviations, the necessary corrections will be made via the telecontrol system. The DCF77 transmitted carrier frequency relative uncertainty

12168-456: The signal strength and depends on many factors, e.g., the daytime and season, the angle of incidence of the skywave on the D-layer and the solar activity. The control signal is not transmitted by wire from the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig to the transmitting radio station in Mainflingen but is generated at the place of emission using a control unit developed by

12285-559: The tasks of PTB’s "Metrological Information Technology" Department – in accordance with the German Gambling Ordinance ( § 11 ff. SpielV) – is to grant type approvals for gaming machines which offer the possibility to make winnings. Also, according to the Federal Ordinance on Voting Machines, PTB is in charge of the type approval of voting computers. This is, however, moot as, in a judgment of 3 March 2009,

12402-407: The time-transmissions can be received by small ferrite antennas incorporated in the case of radio-controlled low-cost time keepers without the help of exterior antennas. The accuracy of the DCF77 amplitude-modulated time signals suffices for the every-day use of clocks and watches by consumers where primarily the long-term accuracy matters. Further industrial time-keeping systems at railway stations, in

12519-513: The tower controller. For example, Skyhawk eight-Charlie-Papa, left base . In commercial aviation, the callsign is usually the ICAO Flight number . For example, Delta Airlines Flight 744 would have the flight number DL744 and the callsign would be Delta 744 . In most countries, the aircraft call sign or "tail number"/"tail letters" (also known as registration marks) are linked to the international radio call sign allocation table and follow

12636-694: The units as well as PTB’s responsibilities have been combined in this Act. Previously, all questions regarding the units as well as the role of PTB had been distributed among three laws: the Units Act, the Time Act, and the Verification Act. PTB consists of nine technical-scientific divisions (two of them in Berlin), which are subdivided into approx. 60 departments. These again are subdivided into more than 200 working groups. PTB's tasks are as follows:

12753-489: The upcoming electrical industry under the direction of the inventor and industrialist Werner von Siemens . In contrast to the units of length and weight, no recognized methods and standards existed at that time in the field of electrical metrology. The lack of reliable and verifiable measurement methods for the realization of electrical (and other) measurement units was a pressing scientific and economic problem. In 1872, some Prussian natural scientists joined forces and demanded

12870-726: The well-meaning support of the British Military Government, parts of the old Reichsanstalt were established in Braunschweig. The idea for this re-founding had been developed by the former PTR advisor for theoretical physics, Max von Laue, already during his internment in Farm Hall . In 1947, he succeeded in convincing the British authorities to make the former Luftfahrtforschungsanstalt (Aeronautical Research Institute) in Völkenrode near Braunschweig available to

12987-428: The ″Bundesamt für Strahlenschutz″ ( Federal Office for Radiation Protection ) after same had been newly established. Today, PTB’s Division 6 deals with ionizing radiation in general. This also includes a highly sensitive trace survey station for radionuclides which has been measuring radioactive substances in ground-level air for more than 50 years. The " Wende " ("political change") in Germany in 1990 also led to

13104-482: Was also the official bulletin in which the type approvals granted by PTB as well as the tests and conformity assessments carried out by PTB were published in a section of its own [named "Amtliche Bekanntmachungen" ("Official Notes")]. With the new Measures and Verification Act which has been in force since 1 January 2015 and with the new Measures and Verification Ordinance, there is no longer a legal basis for these notices. From 2015 onwards, "PTB-Mitteilungen" is, therefore,

13221-462: Was discontinued as the station is easily identifiable by the characteristic signal. A 250 Hz tone was generated by square wave modulating the carrier between 100% and 85% power, and that tone was used to send one letter per second, between the second marks. During seconds 20–32, the call sign "DCF77" was transmitted twice. In addition, for 793 ms beginning at 200 ms, each time code bit is transmitted using direct-sequence spread spectrum . The bit

13338-500: Was extended, but also its palette of services rendered to industry, in particular in the form of calibrations of measuring instruments. In the 1970s, this led to the founding of the Deutscher Kalibrierdienst (German Calibration Service), which delegated service tasks to accredited, privately run laboratories and allowed PTB to concentrate itself on more demanding measurement tasks. From 1967 to 1995, PTB operated

13455-635: Was integrated into this institute as ꞋꞋBerlin InstituteꞋꞋ while respecting the four-power status of Berlin. In the German Democratic Republic (GDR), the Deutsches Amt für Maß und Gewicht (DAMG) had established itself with its principle seat in Berlin. After several renamings, this institute was designated Amt für Standardisierung, Meßwesen und Warenprüfung (Office for Standardization, Metrology and Quality Control – ASMW) during

13572-554: Was made according to the reflection model with a reflection (one hop) on the ionospheric D-layer. As an example, reception with consumer grade clocks — assuming the employed radio clock can manage reception with ≈ 100 μV/m signal strength — is possible in Norway (Bodø), Russia (Moscow), Turkey (Istanbul), Gibraltar and Portugal (during night hours). Metal structures or interference caused by other electronic devices can cause reception problems within this range. At shorter distances

13689-440: Was not only to investigate general – but mainly also military – fields of application. This included, among other things, the acoustic finding of artillery, the military utilization of ultrasound and the development of decoding procedures. In addition, researchers of PTR developed acoustic mines and a steering system for torpedoes which orientated itself on the sound field of traveling ships. Due to its classical metrological tasks,

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