Oskar Heil

Oskar Heil (1908, in Langwieden/Rhineland-Palatinate – 1994) was a German electrical engineer and inventor. He studied physics, chemistry, mathematics, and music at the Georg-August University of Göttingen and was awarded his PhD in 1933, for his work on molecular spectroscopy.

Figures from Heil's British patent of 1935. The insulated gates are shown as reference number 6, with connection terminals 7, 7', and 7"

Personal life

At the Georg-August University in Göttingen, Oskar Heil met Agnesa Arsenjewa (1901–1991), a promising young Russian physicist who also earned her PhD there. They married in Leningrad, the Soviet Union in 1934. Together they moved to the United Kingdom to work in the Cavendish Laboratory, University of Cambridge. While on a trip to Italy, they co-wrote a pioneering paper on the generation of microwaves which was published in Germany in 1935.^[1] Agnesa subsequently returned to Russia to pursue this work further at the Leningrad Physico-Chemical Institute with her husband. However, he then returned to the UK alone; Agnesa, working in what had by then become a highly-sensitive subject, was possibly not allowed to leave. Back in Britain, Oskar Heil worked for Standard Telephones and Cables until the onset of the Second World War, when he returned to Germany via Switzerland. After the war ended, he went to work in the United States and eventually died there in 1994. Agnesa remained in the Soviet Union until she died in 1991. ^[2]

Microwave vacuum tube

Oskar Heil and Agnesa Arsenjewa-Heil in their pioneering paper developed the concept of the velocity-modulated tube, in which a beam of electrons could be made to form into "bunches" and thereby generate with reasonable efficiency radio waves of considerably higher frequency and power than were possible with conventional vacuum tubes/thermionic valves. This resulted in production of the "Heil tube", the first truly-practicable microwave generator, which slightly predated the (independent) invention of the klystron and subsequently the reflex klystron based on the same operating principle. These devices were a significant milestone in the development of microwave technology (particularly radar), and velocity-modulated tubes are still very much in use at the present day.

Field-effect transistor

Heil is sometimes mentioned as an inventor of an early transistor-like device (see also History of the transistor), based on several patents that were issued to him.^[3][4]

JFETS: The New Frontier states:

"Field-effect transistors (FETs) have been around for a long time; in fact, they were invented, at least theoretically, before the bipolar transistors. The basic principle of the FET has been known since J.E. Lilienfeld’s US patent from 1930^[5], and Oscar Heil described the possibility of controlling the resistance in a semiconducting material with an electric field in a British patent in 1935."

Air Motion Transformer

Main article: Air Motion Transformer

He also invented the "Heil air motion transformer" audio speaker technology ^[6] made famous by the AMT-1A speakers of ESS Labs in the mid 1970s.^[7]

The Heil diaphragm is made of Mylar bonded with conductive aluminum strips. It is equivalent in surface area to a conventional eight-inch cone-type midrange driver, but is accordion-folded down to a compact one-inch band for better point-source dispersion. The low-mass diaphragm is suspended within a massive magnet concentrating an intense magnetic field around the diaphragm. When a signal current passes through the aluminum strips, the ensuing bellows-like motion of the folded "pleats" squeezes air out five times faster than with a conventional cone driver. This rapid acceleration of the air is claimed to provide enhanced sound reproduction, including high dynamic range.

References

1. ^ Zeits. f. Physik, 95, pp.752-762, 1935
2. ^ Thumm, Manfred (2006), "Historical German Contributions to Physics and Applications of Electromagnetic Oscillations and Waves", History of Wireless (John Wiley & Sons): 340–343, ISBN 0471783013, http://books.google.com/?id=NBLEAA6QKYkC&printsec=frontcover&dq=history+of+wireless  (A photo of Oskar Heil together with his wife can be found on p. 341.)
3. ^ GB 439457  Oskar Heil: "Improvements in or relating to electrical amplifiers and other control arrangements and devices" first filed in Germany March 2, 1934
4. ^ Robert G. Arns, "The other transistor: early history of the metal-oxide-semiconductor field-effect transistor," Engineering Science and Education Journal, October 1998.
5. ^ U.S. Patent 1,745,175 "Method and apparatus for controlling electric current" first filed in Canada on October 22, 1925, describing a device similar to a MESFET
6. ^ "Heil air motion transformer" audio speaker technology
7. ^ "Heil air motion transformer" , which may still be available in cached form.

• Agnes Arsenjewa, Über den Einfluß des Röntgenlichtes auf die Absorptionsspektra der Alkalihalogenidphosphore, PhD thesis, 1929.
• Oskar Heil, Auslöschung und Überführung von Resonanzserienspektren ins Bandenspektrum durch Gaszusatz, PhD thesis, 1932.
• A. Arsenjewa-Heil and O. Heil, Eine neue Methode zur Erzeugung kurzer, ungedämpfter, elektromagnetischer Wellen großer Intensität, Zeitschrift fur Physik, Vol. 95, Nos. 11-12 (November 1935), pp. 752–762.

External links

• Heil tube example (manufacturer STC)
• Oscar Heil Aulos Loudspeakers

Persondata
Name	Heil. Oskar
Alternative names
Short description
Date of birth	1908
Place of birth
Date of death	1994
Place of death