Valdemar Poulsen (23 November 1869 – 23 July 1942) was a Danish

engineer Engineers, as practitioners of engineering, are professionals who Invention, invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considerin ...

who made significant contributions to early radio technology. He developed a magnetic wire recorder called the telegraphone in 1898 and the first

continuous wave A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency, typically a sine wave, that for mathematical analysis is considered to be of infinite duration. It may refer to e.g. a laser or partic ...

radio transmitter, the

Poulsen arc The arc converter, sometimes called the arc transmitter, or Poulsen arc after Danish engineer Valdemar Poulsen who invented it in 1903, was a variety of spark transmitter used in early wireless telegraphy. The arc converter used an electric arc t ...

transmitter, in 1903, which was used in some of the first broadcasting stations until the early 1920s.

Early life

Poulsen was born on 23 November 1869 in

Copenhagen Copenhagen ( or .; da, København ) is the capital and most populous city of Denmark, with a proper population of around 815.000 in the last quarter of 2022; and some 1.370,000 in the urban area; and the wider Copenhagen metropolitan a ...

. He was the son of the Supreme Court judge Jonas Nicolai Johannes Poulsen and Rebekka Magdalene (

née A birth name is the name of a person given upon birth. The term may be applied to the surname, the given name, or the entire name. Where births are required to be officially registered, the entire name entered onto a birth certificate or birth re ...

Brandt).

Recording innovations

The magnetic recording was demonstrated in principle as early as 1898 by Poulsen in his telegraphone. Magnetic

wire recording Wire recording or magnetic wire recording was the first magnetic recording technology, an analog type of audio storage in which a magnetic recording is made on a thin steel wire. The first crude magnetic recorder was invented in 1898 by Va ...

, and its successor, magnetic tape recording, involve the use of a magnetizable medium which moves past a recording head. An

electrical signal In signal processing, a signal is a function that conveys information about a phenomenon. Any quantity that can vary over space or time can be used as a signal to share messages between observers. The '' IEEE Transactions on Signal Processing ...

, which is analogous to the

sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by ...

that is to be recorded, is fed to the recording head, inducing a pattern of magnetization similar to the signal. A playback head (which may be the same as the recording head) can then pick up the changes in the magnetic field from the tape and convert them into an electrical signal. Poulsen obtained a Telegraphone patent in 1898, and with his assistant, Peder Oluf Pedersen, later developed other magnetic recorders that recorded on steel wire, tape, or disks. None of these devices had electronic amplification, but the recorded signal was easily strong enough to be heard through a headset or even transmitted on telephone wires. At the

1900 World's Fair The Exposition Universelle of 1900, better known in English as the 1900 Paris Exposition, was a world's fair held in Paris, France, from 14 April to 12 November 1900, to celebrate the achievements of the past century and to accelerate developme ...

Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. Si ...

, Poulsen had the chance to record the voice of Emperor Franz Josef of Austria which is believed to be the oldest surviving magnetic audio recording today. Poulsen developed an arc converter in 1908, referred to as the "Poulsen Arc Transmitter", which was widely used in radio before the advent of

vacuum tube A vacuum tube, electron tube, valve (British usage), or tube (North America), is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied. The type known as ...

technology. The system was able to communicate between Lyngby and Newcastle with a 100-foot mast.

Death and legacy

Poulsen died on 23 July 1942. A stamp was issued in honour of Poulsen in 1969. The Valdemar Poulsen Gold Medal was awarded each year for outstanding research in the field of radio techniques and related fields by the . The award was presented on 23 November, the anniversary of his birth, and Poulsen himself received the inaugural award in 1939. The award was discontinued in 1993. On 23 November 2018 he was honoured with a Google Doodle for his 149th birthday.Valdemar Poulsen’s 149th Birthday
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References

External links

* "

'". 100 years of magnetic recording. * . * Katz, Eugenii, . Biosensors & Bioelectronics. * Poulsen, Valdemar, "'' Method of Recordings and Reproducing Sounds or Signals''". Magnetic Tape Recorder. * by means of Poulsen's telegraphone. {{DEFAULTSORT:Poulsen, Valdemar Engineers from Copenhagen Danish engineers 19th-century Danish inventors Valdemar Poulsen Gold Medal recipients 1869 births 1942 deaths 20th-century Danish inventors