500 kHz
The frequency of 500 kHz or wavelength 600 m has been the international distress frequency since the introduction of the marine radio service . The special choice of the frequency 500 kHz or 600 m wavelength from the frequency spectrum is based on the extraordinarily long, exclusive and specially protected use in marine radio services. For almost 80 years, the frequency was the international calling and distress frequency in maritime radio services.
overview
The use of the 500 kHz frequency was regulated in radio management conferences . This is where the rules were laid down that the contracting states had undertaken to observe and obey. In the ITU Radio Regulations (Radio Regulations, Eng. Radio Regulations) all the details were laid down to technology, traffic management, education and training of personnel of the sea and coast stations , the accounting procedures and much more.
The launch of the first Sputnik satellite on October 4, 1957 heralded a new era in maritime radio service. However, it took a few decades before an automated radio service was introduced via telecommunications satellites of the Inmarsat system at the end of the 1980s . The interests of ship safety and distress radio were taken into account in the GMDSS system . The further use of specially trained staff to operate the marine radio stations in tactile radio was thus superfluous.
Until then, the basis for signaling all stations with one another was telegraphy according to the Morse-Gerke code . The main means of communication in seafaring was the telegram . Ships of a certain size had to be equipped with medium wave radio systems. With these systems only a tactile radio was possible. The use of short and border waves in marine radio did not take place until many years later.
Former radio officers have been trying for a number of years (1995) to gain the memory of telegraphy and 500 kHz by including it on the list of UNESCO world cultural heritage sites of intangible goods.
German radio amateurs have been included on the UNESCO list.
Beginnings
In the fall of 1886, the existence of invisible, electromagnetic waves was proven by Heinrich Hertz at the University of Karlsruhe. At first one could not do anything useful with the new ether waves, as they were also called. In the absence of technical possibilities, it was not possible to cover distances greater than a few kilometers. It was only through the intensive attempts by Popow (from 1893), Marconi ( Villa Griffone , from 1895), Slaby (Berlin, AEG , 1897), Preece (England, 1897), Braun (Strasbourg, Siemens 1899) and others that it succeeded until Year 1900 to cover distances of up to 100 kilometers. With these distances one could "see" beyond the horizon. The great usefulness of this system for shipping became clear and was promoted primarily in England, Germany, the USA and Italy.
Long wave
At first one was only able to generate long waves with sufficient transmission energy and to detect them in mechanical receivers ( coherers according to Branly ). Extensive antenna systems are required to radiate long waves, and these are difficult to accommodate on a ship. The first transmitters generated strongly damped waves via spark gaps ( pop-spark transmitters ).
Channel
With the invention of the extinguishing spark transmitter by Max Wien (1905) it was possible to generate almost undamped waves. The frequency can be set more precisely according to this circuit and the operation with 500 Hz alternating current produces a singing tone of 1000 Hz. These transmitters are also called 'resounding sparks' and were quickly used in marine radio. Marconi developed a rotary spark gap in which a motor-driven wheel with many contacts formed the spark gap. Similar to the extinguishing spark transmitter, this device ensured that the spark in the spark gap was quickly torn off, thus causing a rapid and frequent series of flashovers.
Radio conferences
After the radio systems were able to bridge ever greater distances, intergovernmental regulation of radio operations was seen as necessary. In 1903, for example, the German government invited the first radio conference . At the second radio conference in Berlin in 1906, the 600 m wave was proposed as the international standard for maritime radio service. Some countries did not take part in the conference or did not fully consent to the agreements and pursued national, private-sector goals.
As a replacement for the previous distress signal CQD (also known as “come quick danger”), the later mandatory distress signal SOS (also called “save our souls”) was proposed. This suggestion was not based on the fact that it sounds so nice in plain text, but because the conversion in Morse code is more concise than with the CQ (general call to all stations). The CQ was used constantly by all radio stations and a CQD could easily be overheard.
500 kHz became standard
Following the investigation into the sinking of the RMS Titanic on April 14, 1912, essential regulations were introduced at the third radio conference in London in July 1912. It was agreed that all radio stations, regardless of the system used, would communicate with each other. So far it was z. B. regulated so that radio stations with Marconi equipment only communicate with each other, usually recognizable by a call sign that began with the letter M. It was also stipulated that in future a permanent listening watch at 500 kHz should be observed.
Radio staff
The manufacturers of radio systems equipped the ships with the devices and at the same time made the trained personnel available. The radio officers were employees of these companies and were rented to the shipping companies together with the systems. The focus was on equipping the passenger ships, as the large number of people on board meant that a large number of telegrams were to be expected, which resulted in good earning opportunities for the companies. The equipping of the other merchant ships, however, was slow because it was not mandatory to have a radio system on board. In England and Italy and also on ships of other nations, systems from the Marconi companies were installed. In Germany, the 'German operating company for wireless telegraphy' DEBEG , founded in 1907, took on these tasks. It was founded at the insistence of Kaiser Wilhelm II and brought together the activities of the rival companies AEG , Siemens , Telefunken and C. Lorenz .
The radio officers took part in the public exchange of messages and were obliged to observe the secrecy of telecommunications , since their activities provided them with knowledge of the contents of the news. They were not allowed to pass on the information they had obtained to any third party under threat of imprisonment. A radio officer on a merchant ship recently worked eight hours in a two-hour watch, two-hour off-watch system, until eight hours had been completed. The car alarm was on during the free watch and during an absence from the radio room. This involved a receiver that was permanently tuned to 500 kHz and was able to evaluate the car alarm signal, which consists of a sequence of 12 transmitter keystrokes each lasting four seconds. After the fourth signal it had to trigger an alarm in the radio officer's living room and on the bridge. The training of radio officers after 1950 in Germany was carried out at seafaring schools . After passing an examination at the telecommunications authorities, they were issued a patent with which they could seek employment with shipping companies.
As in other professions, the radio officer was given all sorts of nicknames, such as: Sparks, Marconista, Funkenpuster, radio operator, Telgraphista. The reference to radio goes back to the early days of technology, when the pop and extinguishing spark transmitters used were actually large spark generators.
In many cases, the radio officer also took on the administrative work, carried out clearing in foreign ports, etc.
business
The starting point for operation in marine radio was the shared use of the 500 kHz frequency. Coastal radio stations were obliged to be ready to transmit and receive at all times. Each participant in the radio communication called other stations when the frequency was free. If you wanted to establish contact with a station, you called them on 500 kHz and agreed on an alternate frequency to handle the following traffic. Coastal radio stations announced special broadcasts such as weather reports, nautical warnings, ice reports and collection lists on 500 kHz, in order to then transmit them on a different operating frequency. All transmissions were then interrupted for three minutes during the emergency breaks in order to enable the marine radio stations to eavesdrop on the 500 kHz. Depending on the transmission power, ranges of 500 nautical miles were achieved. Coast stations with higher transmission power were also heard at distances of more than 1500 nautical miles.
In order to overcome language barriers, there was a system of standardized abbreviations. It was possible to communicate with these Q groups in relation to radio traffic and operational management. In the course of time, other abbreviations that were not laid down in the Executive Code (e.g. gm for "Good Morning") that were generally used were established.
Distress break
The silence period (SP) was introduced at later radio conferences. Every half hour between the 15th and 18th as well as the 45th and 48th minute, all other radio communications must be stopped and the receiver can be heard on 500 kHz to determine whether there is an emergency at sea. A distress at sea is generally initiated with the car alarm signal, followed by the alarm message. Only the captain reserves the right to explain the distress at sea and to request appropriate alarms.
Marine radio in Germany
In 1897 the lecturer at the Technical University of Berlin-Charlottenburg, Slaby, traveled to England and was an eyewitness to Marconi's radio tests on May 15, 1897 between Lavernock Point and the island of Flatholm on the Bristol Channel. Slaby continued to work on improving the technology in Berlin and was close to the AEG company. None of the pioneers had managed to cover 100 kilometers or more until 1900.
In the spring of 1899, Prof. F. Braun and his close colleagues Cantor and Zenneck continued the radio tests that had been started in Strasbourg on the North Sea in Cuxhaven. The trials dragged on until autumn 1900. The North Sea Line's Sylvana seaside resort ship , which operated between Cuxhaven and Helgoland, served as the experimental vehicle. The land station was initially located at the lighthouse on Alte Liebe . The system for the Kugelbake was later relocated to Döse. Here, on September 24, 1900, the safe bridging of 62 kilometers to the island of Helgoland was achieved. The lightships in the Elbe estuary were equipped with radio systems and participated in a ship reporting service. In October 1900, the emergency at sea of the stranded Bremer full-rigged ship Bischoff was signaled to Cuxhaven and help was brought in.
In May 1900 the first commercially operated radio link between Borkum and the lightship Borkum Riff was put into operation. The devices were supplied by Marconi, built and operated by the waterways and shipping administration and paid for by the shipping company Norddeutscher Lloyd . Your express steamer Kaiser Wilhelm der Große was also equipped with a Marconi system and initially manned by a Marconi radio operator.
In 1907, after several years of preparation by the Reich Postal Administration , the coastal radio station Norddeich Radio was put into operation for public transport with ships in the North Sea. This coastal radio station with the last callsign DAN has become one of the largest radio stations in the world over the years. The major radio stations Nauen, Königs Wusterhausen and Eilvese near Hanover were also involved in the maritime radio service at times. In the eastern part of Germany, which was divided until 1989, the coast radio station Rügen Radio perceived the radio service.
At the end of the 1990s, in the countries that operated maritime radio, tactile radio based on the Morse-Gerke code was completely set to medium and short waves for shipping. The once famous coastal radio station callsigns and their ether waves in telegraphy are forever mute. There was also a shortwave radio network that worked according to an automatic method, via which telex and e-mail could be exchanged.
The marine radio itself lives on and the technical revolution has freed the seafarers from their centuries of isolation.
500 kHz today
The 500 kHz frequency is still used as a calling and emergency radio frequency. The characteristic clocks with the marked listening times are still hanging on the bridges of many ships. Antenna systems for the frequency of 500 kHz are complex to implement (half a wavelength = 300 m). Other systems are now in use and prescribed for alerting in emergencies at sea. GMDSS systems are now mandatory on all larger ships. Depending on the sea area, a DSC watch receiver and transmitter is required for at least VHF channel 70, outside the sea area A1 also on other specified frequencies in the border or shortwave range or in satellite radio.
Aural watch on 500 kHz by coastal radio stations has also become rare; an exception is e.g. B. Constanța Radio , which also broadcasts storm warnings and maritime safety information for the western Black Sea on the nearby frequency 446.5 kHz, also in tactile radio .
Web links
- Berlin, 1906 Preliminary conference concerning wireless telegraphy
- 100 years of marine radio history
literature
- F. Fuchs: Outline of the spark telegraphy. R. Oldenbourg, Munich / Berlin 1922.
- A. Fürst: In the Bannkreis von Nauen, The conquest of the earth by wireless telegraphy. German publishing company, Stuttgart / Berlin 1922.
- G. Ulsamner: Lightship Borkumriff: The interesting history of communications on the coast. 5th edition. Self-published, Emden 2004, ISBN 3-00-014964-3 .
- Bulletin of the Marine Radio Comradeship Bremen. Association of radio officers at the Bremen Seafaring School, booklets since the 1950s
- Heinrich Hertz School: Heinrich Hertz, Thoughts and Documents . H. Hertz School, Hamburg.
- G. Canzler: Norddeich Radio, 1905–1998 . Risius, Weener (Ems), 2004, ISBN 3-88761-091-1 .
- F. Kurylo: Ferdinand Braun, life and work of the inventor of the Braun tube, Nobel Prize 1909 . Heinz Moos, Munich 1965.
- H. Lehmann: International marine radio service. Cuxhaven 1983, ISBN 3-920709-02-0