The Sainte-Assise transmitter (french: Émetteur de Sainte-Assise) is a very low frequency (VLF) radio transmitter and military installation located on the grounds of the in the communes of Seine-Port,

Boissise-la-Bertrand Boissise-la-Bertrand () is a commune in the Seine-et-Marne department in the Île-de-France region in north-central France. Demographics The inhabitants are called ''Boissisiens''. See also *Communes of the Seine-et-Marne department The foll ...

, and Cesson in the Seine-et-Marne

department Department may refer to: * Departmentalization, division of a larger organization into parts with specific responsibility Government and military *Department (administrative division), a geographical and administrative division within a country, ...

of the Île-de-France region of France. The transmitter's original equipment was inaugurated on 9 January 1921, at the time being the most powerful radio transmitter on Earth. On 26 November 1921 the first French radio program was transmitted from Sainte-Assise. In 1965 the transmitter was used to send VLF signals to

FR-1 The Ryan FR Fireball was an American mixed-power (Reciprocating engine, piston and jet aircraft, jet-powered) fighter aircraft designed by Ryan Aeronautical for the United States Navy during World War II. It was the Navy's first aircraft with a ...

, the first French satellite. Since 1998 the French Navy has used the transmitter to communicate with submerged

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

Design

Large spiral inductors in radio transmitter - France 1922

The original equipment of the Saint-Assise transmitter included large spiral "pancake" inductors in a high-power longwave alternator transmitter which served as a transatlantic wireless telegraphy station. These combinations of inductors and alternator transmitters were called "

oscillation transformer A variety of types of electrical transformer are made for different purposes. Despite their design differences, the various types employ the same basic principle as discovered in 1831 by Michael Faraday, and share several key functional part ...

s." The primary coil was connected to a large rotating radio frequency alternator which produced the radio signal. The secondary coil was connected to the overhead wire aerial system, over long, supported on sixteen high towers, which radiated the radio waves. The

inductance Inductance is the tendency of an electrical conductor to oppose a change in the electric current flowing through it. The flow of electric current creates a magnetic field around the conductor. The field strength depends on the magnitude of the ...

of the secondary coil resonated with the capacitance of the antenna to form the tank circuit of the transmitter in order to control the output frequency. It transmitted on a wavelength of , or 21 kHz. The station had two 500 kW

Alexanderson alternator An Alexanderson alternator is a rotating machine invented by Ernst Alexanderson in 1904 for the generation of high-frequency alternating current for use as a radio transmitter. It was one of the first devices capable of generating the continuou ...

transmitters and two 250 kW alternator transmitters. The station's transmitters were designed to handle telegram traffic at a rate of 100 words per minute, and all six of them had a combined capacity of 36,000 words per hour. The spiral shape of the coils reduced resistive losses at radio frequency due to proximity effect. The copper conductors are made in the form of wide strips to increase their surface area in order to reduce their resistance at radio frequencies, since radio frequency currents flow along the surface of conductors due to

skin effect Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor and decreases exponentially with greater depths in the co ...

History

The , a subsidiary of Compagnie générale de la télégraphie sans fil (CSF), built the Saint-Assise transmitter. The first

antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...

at Saint-Assise was supported by eleven pylons and five masts. When it opened on 9 January 1921, the transmitter was the most powerful on Earth, capable of broadcasting to the entire planet. On 26 November 1921 the first experimental French radio program was transmitted from Sainte-Assise using a 1 kW-long wave transmitter. As part of the broadcast, opera singer Yvonne Brothier performed La Marseillaise, a song from '' Mireille'', and an aria from '' The Barber of Seville''. Subsequently, the site was a center of early French experiments with television. In 1941, during World War II, the

Kriegsmarine The (, ) was the navy of Germany from 1935 to 1945. It superseded the Imperial German Navy of the German Empire (1871–1918) and the inter-war (1919–1935) of the Weimar Republic. The was one of three official branches, along with the a ...

requisitioned Sainte-Assise to allow communications between Berlin and U-boats. Despite this, Sainte-Assise was not targeted or damaged by Allied bombing and all of the antennas survived the war. The Saint-Assise transmitter played a key role in the 1965 launch of

, the first French satellite. FR-1's mission objective was to study the composition and structure of the

ionosphere The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an ...

, plasmasphere, and

magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior dynam ...

by measuring the propagation of VLF waves and the local electron density of

plasma Plasma or plasm may refer to: Science * Plasma (physics), one of the four fundamental states of matter * Plasma (mineral), a green translucent silica mineral * Quark–gluon plasma, a state of matter in quantum chromodynamics Biology * Blood pla ...

in those atmospheric layers. For the VLF wave experiments, the Sainte-Assise transmitter and another

ground station A ground station, Earth station, or Earth terminal is a terrestrial radio station designed for extraplanetary telecommunication with spacecraft (constituting part of the ground segment of the spacecraft system), or reception of radio waves fro ...

in Balboa, Panama, transmitted signals at 16.8 kHz and 24 kHz, respectively, while the satellite's magnetic and electric sensors orbiting about away analyzed the magnetic field of the received wave. In 1991 part of the station was sold by

France Télécom Orange S.A. (), formerly France Télécom S.A. (stylized as france telecom) is a French multinational corporation, multinational telecommunications corporation. It has 266 million customers worldwide and employs 89,000 people in France, and 5 ...

to the French Navy, to become the Sainte-Assise Marine Communications Center (french: Centre de transmissions marine; CTM). The CTM, inaugurated in 1998, is tasked with communicating with submerged

s. An entire company of Fusiliers marins patrols the grounds. In December 2000 three unused 180-meter pylons were dismantled. Globecast, an Orange S.A. subsidiary, owns and operates the Sainte-Assise teleport (located on a second site near the Saint-Assise transmitter) which supports multiple parabolic

satellite dish A satellite dish is a dish-shaped type of parabolic antenna designed to receive or transmit information by radio waves to or from a communication satellite A communications satellite is an artificial satellite that relays and amplifies radi ...

es measuring between and in diameter. This station ensures the transmission of up-link signals to communications satellites, in particular video and audio signals for the direct broadcasting of

satellite radio Satellite radio is defined by the International Telecommunication Union (ITU)'s ITU Radio Regulations (RR) as a ''broadcasting-satellite service''. The satellite's signals are broadcast nationwide, across a much wider geographical area than ter ...

and television.

References

{{DEFAULTSORT:Sainte-Assise transmitter Towers completed in 1921 Radio masts and towers in Europe Towers in France Transmitter sites in France Buildings and structures in Île-de-France French Navy technology 1921 establishments in France