Editing Karl Ferdinand Braun (section)

==Inventions and theories==

===Semiconductor===
In 1874, Braun discovered the asymmetric conduction properties of certain materials, which became the foundation for the point-contact rectifier. This discovery showed that certain metal-semiconductor junctions could conduct electricity more easily in one direction than the other, a crucial property for diodes.

His work with semiconductors led to the development of the first point-contact diode, often credited as a basic semiconductor device that allowed the rectification of alternating current (AC) into direct current (DC). This is important because it was one of the first real-world applications of semiconducting materials, paving the way for future semiconductor devices that would later evolve into modern diodes, transistors, and other semiconductor technology.

Braun's discoveries were instrumental in the early development of electronics and helped lay the groundwork for the semiconductor industry we know today.

===Braun Tube===
[[File:Braun cathode ray tube.jpg|220x220px|thumb|Braun's original cold-cathode CRT, the Braun tube, 1897]]
The enduring fame of Ferdinand Braun is largely due to his invention of the [[cathode-ray tube]], which is still commonly referred to as the "Braun tube." Today, the term typically refers to a high-vacuum tube in which an electron beam can be deflected in both horizontal and vertical directions. The first version, developed in Strasbourg in 1897, was far from perfect. It featured a cold cathode and a moderate vacuum, which required a 100,000 V acceleration voltage to produce a visible trace of the magnetically deflected beam. Furthermore, magnetic deflection affected only one direction, while the other was controlled by a rotating mirror placed in front of the phosphorescent screen. However, industry immediately recognized the potential of the invention, leading to its further development. By 1899, Braun's assistant [[Jonathan Zenneck]] introduced [[oscillations]] to magnetically control the Y deflection, and later improvements included the addition of a heated [[cathode]], a Wehnelt cylinder, and high-vacuum technology. This tube was not only used for oscilloscopes but also, for the first time in 1930 by [[Manfred von Ardenne]], became a fundamental component in the first fully electronic television transmission, as a picture tube for television sets, although Braun himself had considered it unsuitable for television.

===Radio Receiver===
[[File:Braun wireless receiving transformer 1905.jpg|thumb|An early resonant transformer invented by Braun used in the coherer radio receivers in wireless telegraphy radio systems made by the Telefunken company in 1903.]]

Following the invention of his tube, Braun also began researching in the field of wireless telegraphy. A key issue in early radio technology was the development of a reliable receiver. Braun, as a physicist, was accustomed to working under reproducible experimental conditions, which the commonly used coherer receivers at the time failed to meet. He replaced the coherer with a [[crystal detector]],<ref name="Seitz" /><ref>{{Citation |last=Braun |first=F. |author-link=Ferdinand Braun |year=1874 |url=https://books.google.com/books?id=YBJbAAAAYAAJ&pg=PA556 |title=Ueber die Stromleitung durch Schwefelmetalle |trans-title=On current conduction through metal sulfides |language=de |journal=Annalen der Physik und Chemie |volume=153 |issue=4 |pages=556–563 |doi=10.1002/andp.18752291207|bibcode=1875AnP...229..556B }}</ref> which greatly improved the sensitivity of the receiver, although the crystal detector required frequent re-adjustment. It was only later that the electron tube replaced the crystal detector, although devices like germanium diodes continued to be used in simpler receivers for some time. The first FM radar systems still employed a crystal detector.<ref>{{cite web | url=https://mwsherman.com/fmonly/fm_only_lowtech.html | title=FM only: Low Tech FM Radios }}</ref>

In late 1898, the technology was commercialized when the chocolate manufacturer from Cologne, [[Ludwig Stollwerck]], founded a consortium to exploit Braun's patents, contributing 560,000 marks in capital. After the successful transmission of signals over longer distances, the consortium was transformed into the "Professor Braun’s Telegraphy Company," which eventually became [[Telefunken|Telefunken AG]], set up the first world-wide network of communications<ref name="historyisnowmagazine.com">{{Cite web |date=2014-03-02 |title=The Scientist who World War I wrote out of history |url=http://www.historyisnowmagazine.com/blog/2014/3/2/the-scientist-who-world-war-i-wrote-out-of-history |access-date=2023-09-27 |website=History is Now Magazine, Podcasts, Blog and Books {{!}} Modern International and American history |language=en-US}}</ref> and was the first in the world to sell electronic televisions with [[cathode-ray tube]]s, in Germany in 1934.<ref name="etf"/><ref>[http://www.tvhistory.tv/1934-35-Telefunken-FEIII.JPG 1934–35 Telefunken], Television History: The First 75 Years.</ref> In 1900, Stollwerck facilitated contact with Professor August Raps, head of the Siemens & Halske Telegraph Construction Company, which later took over the development of the apparatus.

See more: [[Crystal detector]]

===Radio Transmitter===
[[File:Braunsche Telegraphiesystem 1898.jpg|thumb|left|Braun's two circuits to send and receive]]
[[Image:KF Braun.png|thumb|right|24 September 1900: Bargman, Braun and telegraphist at wireless station in [[Heligoland]]]]

Braun also made significant contributions to [[Wireless telegraphy|radio transmission technology]]. While Guglielmo Marconi had developed his transmitter primarily through empirical methods, Braun was able to improve it by focusing on the underlying physics. Originally, the resonant and antenna circuits were combined, but Braun separated them into two parts: a primary circuit consisting of a capacitor and spark gap, and an antenna circuit inductively coupled to it.<ref>{{cite book | chapter-url=https://link.springer.com/chapter/10.1007/978-3-030-17685-3_3 | doi=10.1007/978-3-030-17685-3_3 | chapter=The Strasbourg Period: Radio-engineering | title=L.I. Mandelstam and His School in Physics | date=2019 | last1=Pechenkin | first1=Alexander | pages=31–53 | isbn=978-3-030-17684-6 }}</ref> This innovation allowed for greater energy transmission in the system.

By 1898, the resulting powerful systems made the term "long-distance telegraphy" more appropriate, as the maximum range, previously limited to 20&nbsp;km, steadily increased. On 24 September 1900, a radio link was successfully established between Cuxhaven and Helgoland over a distance of 62&nbsp;km.<ref>Ferdinand Braun: ''Drahtlose Telegraphie durch Wasser und Luft.'' Veit & Comp., Leipzig 1901. Reprint: Severus-Verlag, Hamburg 2010, ISBN 978-3-942382-02-1.</ref> On 12 December 1901, Marconi received radio signals at his station in Poldhu, Cornwall, at Signal Hill in St. Johns, Newfoundland, using a transmitter designed in Braun's circuit. Whether this reception actually occurred remains debated in the literature.

Meanwhile, Braun attempted to replace the spark-gap transmitter, which produced damped oscillations, with AC generators that generated undamped oscillations, though he was unable to implement a feedback loop using electron tubes at the time.

[[File:FerdinandBraun drahtlose Station Telegraphie crop.jpg|thumb|A Braun mobile station (1903)]]

Together with [[Georg Graf von Arco]] and [[Adolf Slaby]], Braun was part of the team that developed the concept for "mobile stations for wireless telegraphy for military purposes," which in 1903 led to a practical implementation by AEG and Siemens & Halske. The system consisted of two horse-drawn wagons: one with all the transmitting and receiving equipment, including a battery, and the other with auxiliary and reserve supplies. This allowed the wagons to be separated in difficult terrain, as the station could still operate with just the front wagon.<ref>{{ANNO|zfe|||1903|296|Die drahtlose Telegraphie im Armeedienste|NAME=Elektrotechnik und Maschinenbau|anno-plus=ja}}</ref>

See more:[[Wireless telegraphy]]

=== Antennas ===
Braun also focused on early problems in directional radio—the alignment of transmitting and receiving antennas. He was among the first to achieve directed radiation and optimized antenna performance through calculations.<ref>{{ANNO|emb|||1914|781|Funkentelegraphie und -telephonie. Über den Ersatz offener Strombahnen durch geschlossene in der drahtlosen Telegraphie|NAME=Elektrotechnik und Maschinenbau|anno-plus=ja}}</ref><ref>{{ANNO|emb|04|00|1915|149|Funkentelegraphie und -telephonie. Zur Berechnung von Antennen|NAME=Elektrotechnik und Maschinenbau|anno-plus=ja}}</ref>

Braun's Electroscope
Braun is also credited with the invention of the pointer electroscope, which was named after him.<ref>Sven H. Pfleger: ''Aus dem Physiksaal: Grundlagen und Experimente der klassischen Schulphysik'', p. 172. Partially available online at Google Books</ref>