Elwell-Poulsen Arc Generator 350 Kw

• alternative name: Kolster Radio Corporation

The 350 kW Elwell-Poulsen Arc Generator was a powerful, low-frequency wireless transmitter engineered and built by the Federal Telegraph Company under the guidance of its founder, Cyril Elwell. The generator's core function was to produce continuous, undamped waves for long-distance, transoceanic telegraphy.

Technical Description
The generator operated in the very low frequency (VLF) band, typically in the range of 20 to 30 kilohertz, with some units operating at 24.3 kHz (corresponding to wavelengths over 12,000 meters). Its continuous waves were generated by sustaining an electric arc in a hydrogen atmosphere and applying a strong transverse magnetic field. The specific output frequency was precisely controlled by a tuned LC circuit.

Applications and Advantages
The choice of the VLF band was crucial for its purpose. These low-frequency continuous waves were ideal for long-distance communication because they were less susceptible to atmospheric and solar interference, ensuring a more reliable signal over vast distances. The long wavelengths also allowed for efficient radiation by the massive antenna systems required for transoceanic links.

Manufacturing and Installation
As the holder of the Poulsen arc patents, the Federal Telegraph Company was responsible for the complete lifecycle of its products. It both manufactured these large generators and installed them at major international stations. The famous Lyons, France, installation was a prime example, built by Federal's engineers as part of a network of high-power arc transmitters designed for long-haul, point-to-point communication between Europe and the Americas in the early 1920s.

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Elenco delle radio e altri apparecchi della Federal Telegraph Company; Palo Alto, CA