Historical development of time transmission by radio

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Historical

Timing

The time measurement is not only a question of the accuracy of clocks , but also the question of the determination of a "time zero point". Since ancient times it has been customary to determine the absolute time with the help of sundials , which however had the consequence that the time measurement was location-dependent and in particular depended on the duration of the earth's rotation , since every point on the earth's surface rotates once around the earth's axis every 24 hours . In the Middle Ages, the church tower clocks were regularly calibrated based on the local position of the sun and announced their time signal by striking a bell.

Due to the increasing interconnectedness of the world as a result of the constantly increasing volume of traffic ( railways , shipping ), the principle of true local time has proven to be no longer practicable. For this reason, nationwide uniform time zones were established in almost all European countries in the 1840-1860s, in each of which a uniform time prevails. This differs from the local time and therefore cannot be determined at every location with a sun position measurement. Rather, the time signals are generated at a specific location and then have to be distributed within the relevant time zone.

The time can be determined in different ways. While initially measurements of the position of the sun or astronomical measurements were made, there was a relatively quick transition to mechanical precision clocks, later to electrical clocks, electronic clocks, quartz clocks and finally to the atomic clock and the hydrogen maser clock . The latter are so precise that they are no longer calibrated on the basis of the rotation of the earth, but rather serve as a time standard due to the extremely constant intermolecular frequencies and are used to insert or omit leap seconds when the earth's rotation period deviates .

Time transmission

The time signal was initially transmitted from a source to the user in different ways. For example, you could subscribe to the time at the mathematical-physical salon in Dresden , which was then delivered at regular intervals by a messenger with a portable watch.

With the introduction and further development of the railway system, it was necessary to synchronize the mechanical clocks at the stations. This soon happened via electrical lines with the help of actuating pulses.

Other transmission techniques used optical signals. In 1876, a time ball system was built on Kaiserkai warehouse No. 1 in the Port of Hamburg . Around noon, 10 minutes before 12:00, a 1 meter black ball was pulled up halfway - and three minutes before 12:00 finally completely - and dropped 3 meters at exactly 12:00 PM Greenwich Mean Time . This system could be controlled from the observatory by an underground cable - initially directly by pressing a button by the astronomers in the observatory at Millerntor , and from 1899 automatically by electrical contacts on the pendulum clock . The accuracy was a tenth of a second per day. Since such a time ball could only be seen over a comparatively short distance, the desire for a system for transmitting time signals over longer distances soon developed.

Time signals by radio

The possibilities of telegraphy that emerged in the first half of the 19th century were also used to distribute time signals from the very beginning. The prerequisites for this were created by Alexander Stepanowitsch Popow , who in 1895 was the first to succeed in wirelessly transmitting radio signals with a radio transmitter up to an antenna 250 m away.

Guglielmo Marconi had created a wireless communication option between France and England over the English Channel in 1899. In 1901 he first sent wireless signals across the Atlantic Ocean.

Around the middle of Marconi's early work, a proposal was made to use the new, wireless medium for broadcasting time signals by radio. In a conversation before the Royal Dublin Society in November 1898, the instrument maker and engineer Howard Grubb ( Sir Howard Grubb, Parsons and Co. ) was the first to propose the concept of a radio controlled clock.

In the journal “Scientific Proceedings for the Royal Dublin Society”, Grubb wrote under the title “Proposal for the Utilization of the 'Marconi' System of Wireless Telegraphy for the Control of Public and Other Clocks”:

"There is something very beautiful in this action of the 'Marconi' wave. In a city supplied with this apparatus we should be conscious as we hear each hour strike that above us and around us, swiftly and silently, this electrical wave is passing, conscientiously doing its work, and setting each clock in each establishment absolutely right, without any physical connection whatsoever between the central distributing clock, and those which it keeps correct by means of this mysterious electrical wave. "

"We might go even still further, and although I do not put it forward as a proposition likely to be carried out in any way, except as an experiment, yet it undoubtedly would be perfectly possible to carry an apparatus in one's pocket, and have our watches automatically set by this electrical wave as we walk about the streets. "

This gave birth to the basic idea of ​​transmitting the time signals by radio.

Radio time signals for shipping

The first time signals for shipping were transmitted in 1903 by the United States Navy using a clock in the United States Naval Observatory in Washington, DC . However, this was an irregular maritime service which was intended to allow seafarers to check and adjust their maritime chronometers .

It was not until August 9, 1904 that regular scheduled radio service began at the Navy Yard in Boston . Possibly the first radio transmitter for time signals outside the USA was the Canadian VCS station in Halifax , which began transmitting in 1907.

From 1910, time signals were also broadcast in Europe. The French Bureau des Longitudes broadcast time signals over the Eiffel Tower twice a day . The reference clock was in the nearby Paris observatory and the transmission wavelength was 2,000 meters. Because of this long-wave frequency, which can be received over great distances, the signals from this transmitter with the code letter "FL" were intended for shipping and should enable the Navy to correct the ship's chronometers.

The radio signals from Norddeich Radio served the same purpose , which were also broadcast from 1910 by a transmitter 30 km north of Emden .

Identifiers of the time signals via radio

One began early to represent the emitted time signals according to the Morse code using a certain sequence of tones. For example, the time signal emitted by the Eiffel Tower with the name "Tempus" had a very specific pattern of successive dots and lines.

As early as 1912 efforts were made to standardize such time codes internationally. As part of the Conference Internationale de l'Heure in 1912/13, the so-called “Onogo time signal” was created on the basis of an international agreement. This is named after the Morse code on which this time signal is based, which only consists of the letters O (---), N (-.) And G (-.) In the sequence ONOGO. This signal was soon introduced in Germany (Radio Norddeich), Sweden and Spain.

World clock of the German Empire

In the meantime, Ferdinand Schneider had come up with the idea of ​​the exact "world clock" - that is, the synchronization of all electrical clocks in the German Empire with remote-controlled electrical pulses from a transmitter in Fulda. For this purpose, a 150-meter-high transmission tower was to be built in the Johannisau in Fulda and had already been measured in spring 1914. But the outbreak of the First World War ruined the plans. The military also confiscated Schneider's wireless transmitter station. That was the first effort to create a transmitter system only for the transmission of time signals, an idea that was only realized in Germany in 1970.

In the course of the First World War, the time signals from the Norddeich coastal radio station were discontinued in 1916, but after many protests by seafarers they were resumed on January 5, 1917 by the major radio station in Nauen and broadcast on long wave with a wavelength of 3,100 meters. The time signal could be heard at noon and at midnight and was coded according to the ONOGO system.

In 1924 the British Broadcasting Corporation in London began introducing the so-called "six pip" signal, using the first five "pips" as audible tones to count down the seconds to the sixth relevant "pip". Formerly known as the "Greenwich Time Signal", these "pips" can still be heard on the BBC radio program today.

In contrast, some regional radio stations in Germany and also the German station broadcast the ONOGO time signal at regular time intervals, for example as part of news broadcasts. The chairman of the German Society for Time Measurement and Watch Technology reported at the general meeting on January 10, 1932 in Berlin that certain groups of radio listeners, but also certain radio magazines, were striving to stop transmitting the ONOGO time signal via radio stations in the future. At this point, the Deutsche Seewarte proposed to introduce an automatic point signal of short duration instead of the inadequate verbal time announcements by the broadcasters, which could possibly also be "faded in" into the entertainment programs. Despite strong protests from the German Society for Time Measurement and Clock Technology, the Reich Ministry of Post then decided to drop the transmission of the ONOGO time signal via the radio stations, so that this symbol was only available via the German station, the German short-wave station, the Radio Norddeich station and the major radio station Nauen could be received.

Short signal

From July 1, 1932, the Reichssender Hamburg sent a so-called short signal as a time signal at 7 a.m., 11 a.m., 3 p.m., 7 p.m. and 11 p.m. CET , which began 30 seconds before the hour and initially comprised ten-second intervals , then three time tones every five seconds and finally another time signal during the last three seconds before the full hour. This time signal was also sent by the secondary broadcasters of the Reichssender Hamburg and also by the German broadcaster before 7:00 a.m., 12:00 p.m., 6:00 p.m. and 11:00 p.m. CET.

Coincidence time signal

In contrast, the time signal transmitted by the Nauen and the Deutschlandsender at 1.00 a.m. and 1.00 p.m. CET consisted of a 10-minute sequence. During the last 5 minutes before the hour, the so-called ONOGO time signal was emitted and in the minutes 1 to 6 after the hour a so-called coincidence time signal was emitted . The signal from the radio telegraph station of the Deutsche Großfunkstelle Nauen was broadcast on long wave 18,130 m as well as on short wave . The control took place from the Deutsche Seewarte in Hamburg.

Structure of the ONOGO time signal as it was broadcast by the radio telegraph station of the Deutsche Großfunkstelle Nauen around 1934 (the coincidence signal is not completely included in the figure, as it is either incorrectly represented in the source used or cannot be correctly recognized due to the very poor print quality)

Differences between the ONOGO time signal and the coincidence time signal

While the ONOGO time signal initially sent long second impulses for one minute, this was followed by 50 short second impulses and a 5 second continuous tone to initiate the actual ONOGO code, which took 3 minutes and was ended with a 10 second continuous tone . As part of the actual ONOGO code, three 1-second time signals were sent in the last 5 seconds before the full minute as a code for the letter "O", while in the 50-second intervals the codes for the letters "N" or "G" were sent.

The signals were transmitted as Morse code, in particular the sequence of letters ONNNNNOGGGGGO (briefly referred to as the password ONOGO ) was sent. The (Morse) points of the letters N and G represented the actual time signals.

In contrast, the subsequently transmitted coincidence time signal consists of 5 identical 1-minute sequences, each with a 0.5 second time signal at the beginning of each minute and 60 audio signals of 0.1 seconds each, but with an interval of 0.9836 seconds so that a total of 61 time signals were emitted every 60 seconds.

While the ONOGO time signal was mainly used for roughly setting the local clocks on site, for example by stopping them and restarting them at the end of the time signal, the coincidence time signal was used to set a clock on the receiving end to even one To be set precisely to a hundredth of a second. In doing so, use was made of the fact that, due to the sound signals emitted for 60 seconds, synchronicity or coincidence only prevailed for exactly one second beat of a clock tapped during the received time signal. At exactly this point in time, the number of the relevant time signal, calculated from the last minute signal, was noted and the status of the local clock was noted. Since an interval of the coincidence time signal lasts only 0.9836 seconds, the exact seconds can be calculated from the number of the relevant coincidence tone signal and compared with the clock reading. Since the exact second value can be calculated to three decimal places if the coincidence is observed, it is possible to determine the time interval to be corrected to at least one hundredth of a second and to carry out a correspondingly precise correction.

In the course of the 1930s, with the new transmission possibility of the coincidence signal, the demands on the quality and accuracy of the time signal as such increased. In July 1936 , deviations were measured between the time signal transmitted by the Nauen station and the time signals transmitted by the English station in Rugby and the French station in Bordeaux , which were often in the range of a hundredth of a second, while peak values ​​were quite as high +/- five hundredths of a second. While the time signals from the Nauen station were directed to the Geodetic Institute in Potsdam , the Greenwich observatory was responsible for the Rugby station . The reason for the sometimes considerable deviations was, on the one hand, the imprecise determination of the real time and, on the other hand, the errors that occurred when receiving and registering the time signals.

However, the principle of the quartz clock had been known since the 1920s , with which it would easily have been possible to determine the time with greater precision.

Transmitter of the time signals

However, from 1919 to 1932, for example, the so-called Norddeicher encoder was used, an instrument created from a Hipp drive by adding two contact disks, the first signal transmitter in Germany, which was triggered according to the timing of the Wilhelmshaven marine observatory . This was used as a pre-signaling device for the Seewarte until 1936 and was only then transferred to the German Museum in Munich.

In the meantime, the astronomer Professor Wanach himself had made a transducer from scrap material, the pendulum of which was stopped at rest at the outer turning point, and which formed the first coincidence signal transducer of the Deutsche Seewarte. Even when a new signaling device was built in 1937, what was available had to be used as the main signal clock in order to save costs: two Glashütte second pendulum clocks with Riefler pendulums, which were installed in the clock cellar of the Deutsche Seewarte, while it was not until 1939 under the direction of Upper Government Councilor A. Repsold designed a signaling system with a synchronous motor that was driven by a quartz clock frequency.

Reception of time signals

While the time determination and emission had reached a completely sufficient quality for the conditions at the time by around 1940, the receiver technology was far from able to keep pace.

Minute signals without time coding

Illustration of the operation of electrical clocks by means of electrical waves, by Franz Morawetz

The first beginnings in Central Europe go back to Max Reithoffer and Franz Morawetz from Vienna, who on September 17, 1907, received a patent from the Imperial Patent Office in Berlin with the number 188425 for their invention registered on September 20, 1905, “Device for the operation of electrical clocks by means of electric Waves ”. In the case of a signal sent by a central station at certain time intervals, the invention consisted in the fact that a drive was opened in the receiving station by this received signal, which then gradually returned to its original position, inhibited by a spring by a pendulum, and only then did the temporarily interrupted receiving circuit closed again to wait for the next pulse. Since the transmission time intervals were set to about 1 minute, the reception of every single minute transmission signal pulse would have been necessary for sufficient accuracy, which was not achievable in practice. Therefore this timing device was never built.

Another invention by Ferdinand Schneider from Fulda, who proposed in his German patent no. 237428, issued on August 17, 1911, to let the minute hand jump forward by exactly one minute with each transmission pulse, could not help achieve this principle.

Luigi Cerebotani from Munich received the German patent no. 260093 on May 19, 1913 for a further development of this principle , but such a device was never sold.

Time coding with optical resonance indicator

Hans Behne and the Dr. Erich Huth GmbH proposed in their German patent specification No. 266861, issued on November 11, 1913, to continuously change the frequency of the transmission signal and to feed it to an oscillating circuit on the receiver side whose resonance frequency was adjusted in parallel , the output signal of which was communicated to a preferably optical resonance indicator, which was derived from it could directly derive a signal for the current pointer position. However, since such a signal had no “memory”, such a watch failed completely without signal reception. At most, the pointer, which is switched every hour, would allow a rough time estimate in this case. This principle did not find its way into practice either.

The inventor Raymond Louis Roze des Órdons from Paris dealt with the hourly advancement of the hour hand , who then received the German patent No. 269324 from the Imperial Patent Office on January 16, 1914. Here, before every full hour, a large number of predefined signals were transmitted, from which certain rotatable disks were switched on at the receiver side. Such a switching sequence comprised a large number of signals sent approximately every minute and also contained Morse code, so it was apparently based on the ONOGO standard that was created shortly before. However, this method was also very susceptible to signal failure and could therefore not be implemented.

Horophones

One of the first devices actually used to receive time signals was the so-called " Horophone ", which was developed by the Synchronome Company Ltd. in 1913 . was sold in London. It consisted of a clock, a radio receiver and a table. The owner of this device had to listen to and decode the time signal with headphones and manually synchronize the clock at a certain point in time. Several other companies sold similar devices, one such company was founded by Marconi, the inventor of the radio station.

Automatically synchronizing receiver clock

In the following years, various inventors attempted to develop a clock that synchronized itself automatically to a received time signal. Among them is FO Read from London , who claimed in an article in the Daily Sketch newspaper on October 4, 1912 that he had such a watch in his home; however, it is not known whether such a watch still exists and whether it even worked, despite Reed trying to obtain watch patents.

The French watchmaker Marius Lavet and the English watchmaker Alfred Ball are also named as candidates for the invention of the self-synchronizing receiver watch . Lavet worked on the development of a radio controlled clock in the 1920s. However, he did not succeed in developing one until it was ready for production, although he received many patents in the field of electrical timekeeping. Ball began experimenting with wireless control of electrical clocks in 1914. Although he subsequently devoted himself primarily to this research, he did not achieve a degree until his death in 1932. He published a series of articles in the Horological Journal from 1928 under the title "The Automatic Synchronization of Clocks and Wireless Waves". His work focused on the development of a master clock and auxiliary clocks connected to it. He used valves , relays, and gears to set the hands and regulate the speed of the pendulum. Although such watches were probably never sold, prototypes marked “Auto Controlled by Wireless from Daventry” have been built.

On July 17, 1926, the Junghans AG brothers and Oskar Junghans in Schramberg were granted German patent no. 431834 by the Reich Patent Office for the invention of the wirelessly influenced pointer setting device for clocks . The patented idea consisted of triggering a current impulse when a transmission signal was received and thereby causing the interlocking to be returned to the exact time value via a curve heart. With this principle, the reset is obviously too abrupt for the mechanics. Therefore, in a further invention, for which patent no. 430355 was granted on June 15, 1926, the patent owners proposed that the force for the mechanical return of the signal box should be brought about by means of a rake-like drop lever, whose movement into the curve heart is braked by a wind vane escapement becomes. Since this principle became too complex overall, the patent owners, according to patent specification No. 431835 issued on July 16, 1926, took a different approach, namely the resetting of a pointer by a current pulse triggered by a transmission signal in a magnet that points to the Counterweight of the pointer concerned acted magnetically.

On July 31, 1926 the Junghans AG brothers and Oskar Junghans in Schramberg were granted the German patent no. 432096 by the Reich Patent Office for the invention of a radio telegraphic alignment device for independent clocks . This provides for a star wheel with 12 teeth to be turned one tooth at a time with every full revolution of the minute hand. One of the twelve teeth carries a pin that closes a contact every twelfth hour and thus switches on the heating of an amplifier tube about four minutes before the next full hour, which then enables the reception of the transmission signal in order to reset the movement when it is received. It was a table clock with a second balance. A series production of this watch is not known.

The inventors Camille Lipmann, Frédérick Strahm and André Strahm from Besançon in France chose a similar approach, which is documented in German patent no. 423 847 of January 12, 1926. Here, too, the receiving device was only switched on shortly before the expected transmission signal. However, the device known from it was only able to process time signals in the sound wave range , since these signals had to pass through the membrane of a telephone receiver.

In order to minimize the risk of incorrect settings, Camille Lipmann and André Strahm proposed in a further patent no. 490 241 issued on January 27, 1930, to decode the time intervals between several pulses of the transmission signal in quick succession in order to detect interference signals. If a suitable number of pulses follow one another at the correct interval, a local circuit is finally closed and a battery-operated actuating device is activated. Like all previously known devices, this device also suffers from the disadvantage that only the minute hand can be corrected; a second hand cannot be reset with it and was therefore not even intended. The accuracy achievable with this was therefore 60 seconds.

The inventors Heinrich Geffcken, Hans Richter and Erich Zachariä from Leipzig , who received the German patent no.479,900 for this invention on July 31, 1929 , achieved a similar effect - the selective switching through only after the receipt of a predetermined number of signal pulses . However, details of the adjusting mechanism cannot be found in this patent.

On August 28, 1929, the Reich Patent Office granted Otto Muck from Munich-Großhadern patent no. 481 728 for the invention of wireless synchronization of clocks that are temporarily connected to radio sets . In it, Otto Muck makes the suggestion to use a commercially available radio device to receive a time signal, the reception frequency of which is switched to the transmission frequency of the time signal by a variably adjustable radio transmitter shortly before the arrival of an expected time signal. The received time signal is tapped by a transformer at a coil and fed to the grid electrode of an amplifier tube. The anode voltage signal amplified accordingly by this is fed to the actual actuating device. The actuator itself is not described.

In 1930 Roters & Paulding published an article at the Stevens Institute of Technology in Hoboken , New Jersey, about a radio-controlled clock that was said to be able to synchronize with the time signals transmitted by an American transmitter, the NAA . Although this watch was also intended for production, there are no reports that this watch was ever sold. The receiver converted the time signals from the NAA time transmitter between 11.55 a.m. and 12.00 p.m. into running pulses which were used to drive the timing mechanism. An operator had to assist with the initial synchronization by turning on the clock and adjusting the display element prior to the arrival of the time signal. After it was initially synchronized, a magnetic selector was used to detect pulses four times a day and to intervene in the transmission to regulate it.

Meanwhile, the Siemens company , which had been pacemaker in the construction of operating equipment and clocks for the railway since the middle of the last century, developed the so-called "ONOGO" clock in the 1930s, which received the time signal wirelessly with a tube receiver and with it regulated a master clock with an electric elevator. However, this development was initially discontinued after the Second World War .

In 1956, the company IBM , USA, developed a semi-automatic radio-controlled clock and marketed it under the name IBM Type 37 Radio Supervised Time Control Clock . It was a floor clock with a pendulum in a large wooden case, which was able to receive the so-called WWV / WWVH telegraph time signal. Due to the size and gravity of the pendulum, the control is likely to have been limited to changing the duration of the pendulum swing.

Around the same time, Theodore L. Gilliland applied for a US patent for an invention entitled Automatic Radio Control for Clocks, for which he was granted a US patent on February 18, 1958. In this, however, Gilliland primarily deals with the selection of the best broadcast signal to be received, since the American time signals were broadcast on the one hand by two broadcasting stations, one near Washington, DC , and on the other hand from Maui , Hawaii , and also at 6 different radio frequencies, namely 2, 5 MHz, 5.0 MHz, 10 MHz, 15 MHz, 20 MHz and 25 MHz. In addition, due to the large distances of several 1,000 km in the area of ​​the USA, it should be noted that at greater distances from the transmitter location , only the wave reflected from the stratosphere can be received, but not the ground wave . Because of this, Gilliland has developed an extremely complete electro-mechanical system with which the transmitter with the highest reception field strength could be selected and set. In addition to complex mechanics and a few passive electrical components, such as resistors and coils, the circuit only featured tube technology.

Motivation for modern developments

In 1958, Karl Gebhardt from Nuremberg began to deal with the development of a radio clock . Even before his studies, Gebhardt began in 1946 together with the inventor Ludwig Reiss in their parents' watchmaker's workshop in Nuremberg with the development of battery-operated clocks and frequency-controlled clocks based on the alternating current network . Several electric outdoor clocks were operated by the parents' watchmaker's workshop, which were electrically controlled by a master clock . A mechanical pendulum clock, an HU 120 from the Bürk company, was used as the master clock. Although this master clock was very good with an accuracy of approx. Three to four seconds per day and an unlimited running time was ensured due to an automatic winding mechanism, cumulative errors occurred in the course of operation, which gradually added up to one or more minutes.

The increased accuracy requirements for modern watches could no longer be met with mechanical watches. At that time there were already quartz clocks, but their external dimensions were very large and they also had to be operated in temperature-controlled rooms. At that time they were unsuitable for private and medium-sized use. On the other hand, such a quartz clock was used in the studio of the Bavarian Radio in Munich , so that the time information transmitted from there via radio waves was very precise. Due to the tube technology still prevailing at the time, as well as the inadequate setting principles, which only concerned the minute hand, but not the second hand, there were neither radio nor time signal receivers in Germany at that time which would have been able to convert this time signal into a precise time display to implement.

Self-synchronizing clock with transistors

That is why Gebhardt designed a new type of device in 1958, with an evaluation device connected downstream of a transistorized radio receiver, which also works with semiconductor technology using flip-flops . The actual time information was filtered out by counting the time pulses sent and used to release a previously stopped pendulum of a mechanical master clock. A HU-120 from Bürk was used as the adjustable master clock, which was adjusted in such a way that it went forward by a few seconds in a 24-hour cycle. The synchronization of the master clock was carried out once every 24 hours, always in the evening at 6 p.m. For this purpose, the master clock was rebuilt in such a way that about one minute before 6:00 p.m. the radio receiver was switched on automatically via a contact pin and switched off again after the correction. When the hand position was exactly 6:00 p.m., the main clock was stopped by locking the pendulum in the area of ​​its turning point by an electromagnet on the clock case, which interacted with a permanent magnet on the pendulum lens. An air gap to be maintained could be precisely specified by means of an adjusting mechanism for the electromagnet that is fixedly mounted on the housing. At the last decoded tone of the time signal, the circuit of the electromagnet was interrupted and the pendulum system was released again in a second-synchronous state. Gebhardt is the inventor of the transistorized radio synchronization regulator for the precise time synchronization of master clocks by radio.

In 1970 Gebhardt personally presented his positive experiences with this technology to the company Telefonbau & Normalzeit . However, it did not find its way into watch technology there, because this company intended to push the quartz technology that has since been further developed.

Movementless radio controlled clock

In the years 1966 to 1972, several inventions by Wolfgang Hilberg were registered for patent, each relating to a "method for the continuous transmission of the time". However, all these developments had the disadvantage that continuous time impulses had to be emitted, which had to be received by a receiving device without gaps in order to effect a small progression of the clockwork on the receiver side. It turned out, however, that in the case of technical and atmospheric disturbances, as well as technically caused interference signals, continuous secure transmission was not possible, so that due to this principle an exact time reproduction was not given. This essential weakness was improved by Hilberg in his patent application for a patent on March 23, 1967 and disclosed under the file number 1673793 on December 23, 1970, "Method and arrangement for the continuous transmission of the time" by adding in immediately successive, short basic intervals, e.g. B. minutes or seconds, the complete information of the currently existing normal time is sent in a pulse code and the transmitted pulse code for controlling a display system in the sense of a numerical or analog time display was evaluated in the receiving stations. With this invention, Hilberg completely dispensed with a clock mechanism in the receiving devices. There were only devices for decoding and displaying the current, decoded time signals. The most recently received time signal remained displayed until a subsequent time signal was received. This led to the display device stopping if the signal reception was poor. Hilberg repeatedly tried to conclude license agreements with the watch industry, but he never succeeded.

DCF77 time signal

However, his idea of ​​a permanent, complete time transmission was finally reflected in the introduction of the DCF77 time signal, which has been broadcast 24 hours a day since August 1970 by a transmitter in Mainflingen near Frankfurt am Main . This took its time signal from a cesium standard time clock in the Physikalisch-Technische Bundesanstalt in Braunschweig and has since emitted its signal at a frequency of 77.5 kilohertz with a transmission power of 50 kilowatts, so that this signal can be received within a radius of 1,500 km can be evaluated. The precision of the cesium standard time clock used at that time was a deviation of 1 second in 1 million years. Based on suggestions from Hilberg, the time signal is transmitted every minute, with coded information about the date and the current time (summer or winter time) being transmitted within the interval between two minute time pulses. Information about the current minute between the 21st to the 27th second is transmitted in a binary code; the data for the hour information start with the 29th second mark and last up to the 34th second. The calendar data is then transmitted: The calendar day from the 36th to the 41st second; the day of the week from the 42nd to the 44th second; the calendar month from the 45th to the 49th second and the calendar year from the 50th to the 58th second.

First clock that synchronizes precisely to the second

With the exception of the prototype developed by Gebhardt in 1958 of a mechanical clockwork that could be synchronized to the second with a time standard by radio and would continue to run autonomously if the radio signal failed, there was no evaluation device suitable for this new technology at the time.

In his book "Funkuhren", published in 1983, Hilberg concludes with the outlook:

“In the foreseeable future, it is unlikely that microprocessors will be able to be implemented that can process a high data stream over the years when fed from a small battery. Therefore, if you cannot operate the transmitter and receiver continuously, and if you want to use the advantages of the DCF77 system, keyed operation of the radio clock in cooperation with a mostly autonomously working quartz clock will be inevitable. "

First marketable radio-controlled watches

Junghans RC alarm 1 from 1984 (price at that time 149 DM , which corresponds to around 139 EUR today)

As a result of the further miniaturization of electronic components, the Junghans company began developing a radio-controlled clock in 1984, which was launched on the market in 1986 under the name RC-1. It was a battery-operated quartz clock with radio synchronization, which was offered in two versions, one as a table clock and one as a wall clock.

In the same year the company Kieninger & Obergfell presented their “Spacetimer” under the trademark “Kundo”, a radio controlled clock as a small plastic table clock with a base. In addition to an analog display for the time, it also had a digital display for displaying the date. This technology was later adopted by Steiger GmbH in St. Georgen.

Junghans then further developed the radio-controlled clock technology into the RCS-1 solar radio-controlled clock, a table clock with integrated solar cells for power supply.

First marketable radio-controlled wristwatch

  • First radio-controlled wristwatches in the world

  • digital:
    Junghans MEGA 1

  • analog: Junghans Mega

In 1990 Junghans presented the first radio-controlled wristwatch, the MEGA 1 . This development is mainly due to the promotion of this technology by Karl Diehl , the owner of the Diehl Group at the time , and is rated by experts as one of the most important events of all time in watch technology ("one of the most momentous horological events ever").

First marketable radio-controlled solar wristwatch

This development led to the world's first radio-controlled solar wristwatch, also developed and manufactured by Junghans, in 1992, which was launched on the market in 1995. For the first time, the entire dial was used to generate electricity.

Advantages of the current technology

In addition to the display of a highly precise time, whereby the display of the calendar including the day of the week, changeover between summer and winter time, combined with a dark period of up to 2 years is possible, manufacturers are increasingly integrating further functions in such wristwatches, For example, to determine your location using GPS , cell phone intercoms or internet connections.

The radio-controlled clock has expanded its regional area of ​​application, among other things, with the ability to switch to different transmission frequencies or codes, so that it can be radio-synchronized on almost all continents.

In addition, radio-controlled solar wristwatches have now become the subject of aesthetic designs and are being tapped by the ever-increasing number of interested parties around the world.

Other radio services

Especially in the pre- digital era (until the 1970s), the carrier frequencies of some radio stations were also evaluated as frequency standards. The transmitters broadcast a normal radio program, the time receiver only synchronized to this carrier frequency. The vibrations then had to be counted on site. An example of such a standard frequency transmitter was Radio Hilversum in the Netherlands.

Further electronically evaluable sources for time information are now available in the radio data system of VHF radio stations (as information accompanying the normal radio program) and in the teletext and EPG data of television stations. However, their accuracy is much lower, for example the teletext time display of a television station received via DVB-T lags behind by up to several seconds due to the complex coding on the transmitter side and decoding on the receiver side.

The global navigation satellite systems can also be viewed as a time signal radio service , which primarily send a time signal with atomic clock accuracy , from which the geographic position is then derived in the normal case. The time information can of course also be used directly.

See also

Individual evidence

  1. ^ Time measurement in Hamburg ( Memento from June 11, 2007 in the Internet Archive ), Gudrun Wolfschmidt , Institute for the History of Natural Sciences, Mathematics and Technology at the University of Hamburg
  2. ^ Jochen Schramm: Stars over Hamburg
  3. ↑ a b c d e f g h i j k l Michael A. Lombardi: Radio Controlled Clocks , 2003 NCSL International Workshop and Symposium. (pdf, English; 1.0 MB)
  4. ^ AV Simcock: Sir Howard Grubb's proposals for radio control of clocks and watches , Radio Time, Volume 4, Issue 10, Fall 1992, pages 18-22
  5. ↑ Sir H. Grubb: "Proposal for the Utilization of the 'Marconi' System of Wireless Telegraphy for the Control of Public and Other Clocks", Scientific Proceedings for the Royal Dublin Society, Volume X, Part I, No. 7, 1899, Pages 46-49
  6. ↑ a b c d e f g h David J. Boullin: Radio clocks for domestic use , in: Old watches and modern time measurement, Callwey, Munich 1989, ISSN  0343-7140 (issue 4, p. 49ff)
  7. ↑ a b c d e f Dr.-Ing. Edgar Müller: About the most common clock comparisons without registration for astronomical-geodetic purposes , series of publications by the Society for Time Measurement and Clock Technology, Volume 11, Berlin 1941, p. 5ff
  8. ^ Michael Mott: Ferdinand Schneider 1866–1955. Fulda entrepreneur, inventor and engineer ( memento from November 15, 2009 in the Internet Archive ), Fuldaer Zeitung, March 30, 2005
  9. ↑ St. Mollenhauer (Ed.): Ferdinand Schneider. Memories of a Fulda inventor and pioneer of "wireless telegraphy" . Verlag Parzeller, Fulda, 2005. ISBN 3-7900-0378-6
  10. ↑ Dr. A. Repsold: Transmission of the Nauen time signal by radio , series of publications by the Society for Time Measurement and Clock Technology, Volume 4, Berlin 1932, pages 31 ff
  11. ↑ a b F.G. Gauss : Five-digit complete logarithmic and trigonometric tables . Konrad Wittwer, Stuttgart 1949 (reprint of the 1934 edition).
  12. ↑ Dr. Heinrich Gockel: The errors in the recording of the wireless time signals and suggestions for improvement , series of publications of the society for time measurement and clock technology, Volume 9, Berlin 1938, p. 81ff
  13. ↑ Dr. A. Repsold: Die Zeitzeichengeber der Deutsche Seewarte , series of publications by the Society for Time Measurement and Clock Technology, Volume 8, Berlin 1937, p. 25ff
  14. ↑ Dr. A. Repsold: Supplement to the signal generator system of the Nauen time signal , series of publications by the Society for Time Measurement and Clock Technology, Volume 10, Berlin 1939, pages 107 ff
  15. ↑ These further developments in the signaling and transmission of time signals via the German time transmitters were made by members of the Society of Time Measurement and Clock Technology and are documented in the Society's series of publications from 1932 to 1941. This series of publications is now in the library of the German Chronometry Society in Nuremberg.
  16. ↑ German Patent No. 188 425 of September 17, 1907
  17. ↑ German Patent No. 237 428 of August 17, 1911
  18. ↑ German Patent No. 260 093 from May 19, 1913
  19. ↑ German Patent No. 266 861 of November 11, 1913
  20. ↑ German Patent No. 269 324 of January 16, 1914
  21. ↑ German Patent No. 431 834 of July 17, 1926
  22. ↑ German Patent No. 431 835 of July 16, 1926
  23. ↑ German Patent No. 432 096 of July 31, 1926
  24. ↑ German Patent No. 423 847 of January 12, 1926
  25. ↑ German Patent No. 490 241 of January 27, 1930
  26. ↑ German Patent No. 479 900 from July 31, 1929
  27. ↑ German Patent No. 481 728 from August 28, 1929
  28. ↑ The Onogo-AM , published in "Electrical Journal" 1935, page 439
  29. ↑ United States Patent 2824218 of February 18, 1958
  30. ↑ Nuremberg daily newspaper of January 11, 1973
  31. ↑ German Offenlegungsschrift 1673793 of December 23, 1970
  32. ^ Frankfurter Allgemeine Zeitung of March 14, 2006, page T 2
  33. ↑ Prof. Dr.-Ing. Wolfgang Hilberg (ed.): Radio clocks. Fourth Darmstadt Colloquium . R. Oldenbourg, Munich and Vienna, 1983, p. 254