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Summary

Description
English: Large copper antenna loading coil used at the Tuckerton, New Jersey, USA transatlantic wireless telegraphy station built by the German Telefunken Co. in 1912. This station transmitted with a power of about 200 kW at 60 kHz with a Goldschmidt alternator, and communicated 4000 mi. to Eilvese, Germany, one of the most powerful radio stations in America at the time. It fed an umbrella antenna consisting of a vertical radiating tower 825 ft (250 m) high with radial wires extending from the top to 40 ft. poles in a circle at a distance of 1500 ft from the tower. These types of VLF antennas were very electrically short (.05 wavelength) and the radial wires served as a "capacity hat" to increase the efficiency of the antenna. The above loading coil was mounted at the antenna's base and served to tune out the high capacitance, making the antenna resonant so it could be fed energy efficiently.
Because of the low radiation resistance, the antenna and coil acted as a huge high Q tuned circuit and was very finicky to adjust. The coil had to have very low resistance at radio frequencies, and to reduce proximity effect losses it was made of very large size, of large diameter tubing to reduce skin effect losses. The antenna had a very narrow bandwidth and also had a variometer coil to adjust it to resonance. If the variometer was misadjusted, the antenna power would be reflected back into the rotating Goldschmidt generator, overheating it and causing the rotor to expand and grind to a halt.

Deutsch: Große Kupfer-Verlängerungsspule einer Antenne der Sendestation Tuckerton, New Jersey, USA für transatlantische Funktelegrafie, erbaut 1912 von Telefunken. Der Sender hatte eine Leistung von 200 kW bei 60 kHz, erzeugt von einem Goldschmidt-Alternator, und sendete 4000 Meilen weit nach Eilvese in Deutschland. Es war seinerzeit eine der leistungsstärksten Radiostationen Amerikas. Der Sender speiste eine Schirmantenne aus einem 250 m hohen zentralen Mast und Radialen, die von der Mastspitze zu 12 m hohen Pfosten in einem Kreis von 450 m Radius um den Mast gespannt waren. Diese Bauart von Längstwellenantennen war elektrisch sehr kurz (ein Zwanzigstel der Wellenlänge), die Radiale erhöhten als Dachkapazität den Wirkungsgrad der Antenne. Die Verlängerungsspule war am Fuß der Antenne montiert und glich die hohe Kapazität aus, um die Antenne für eine effiziente Speisung in Resonanz zu bringen.
Wegen des geringen Strahlungswiderstandes wirkten Antenne und Spule als Schwingkreis hoher Güte, der schwierig abzustimmen war. Die Spule musste auf der Sendefrequenz einen sehr niedrigen Widerstand aufweisen. Um Verluste durch den Proximity-Effekt zu minimieren, musste sie sehr groß ausgeführt werden, mit einem großen Leiterdurchmesser zur Reduzierung des Skineffekts. Die Antenne arbeitete sehr schmalbandig und wurde mit einer zusätzlichen verstellbaren Spule auf Resonanz abgestimmt. Wenn diese Spule verstellt war, wurde die Sendeleistung in den Goldschmidt-Alternator reflektiert, der sich dadurch erwärmte, bis der Rotor durch Ausdehnung festsaß.
Date
Source Emil E. Mayer, The Goldschmidt System of Radio Telegraphy, Proc. of the Institute of Radio Engineers, New York, Vol. 2, No. 1, March 1914, p. 81, fig. 10. A copy also appears in John Ambrose Fleming (1916) The Principles of Electric Wave Telegraphy and Telephony, 3rd Ed., Longmans Green & Co., London, p.763, fig.30
Author Emil A. Mayer
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  • 2012-03-17 14:51 Spinningspark 1176×866× (250273 bytes) {{Information |Description=Large antenna loading coil |Source=''Proceedings of the IRE'' |Date=March 1914 |Author=Unknown |other_versions= }} == Licensing == {{PD-US}} {{KeepLocal}} Note for patrolling admins: a similar image is on Flickr licensed CC ...

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current13:20, 1 September 2012Thumbnail for version as of 13:20, 1 September 20121,176 × 866 (244 KB)File Upload Bot (Magnus Manske)Transfered from en.wikipedia by User:wdwd using CommonsHelper
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