Abstract: The antenna comprises a metal excitation loop (B1) to be positioned at a height (h) of at least about 1 above the surface (SM) of a conducting medium (M) and a supply means (A, L1n) to be connected to the conducting medium. The perimeter of the loop is about one half of the operating wavelength, namely ?/2, in length. The loop comprises two approximately parallel portions (I1p-I1n, S1) which are at most about ?/50 apart and are capable of extending approximately parallel to said surface in a plane approximately perpendicular to said surface, currents of opposite direction flowing through said portions. The closest portion to said surface includes an aperture between ends (E1p, E1n) of the loop that are connected to the supply means. The antenna is better protected from space waves and it can be reduced in size by being folded up.

Abstract: To broadcast synchronized radio waves in at least one frequency band in a predetermined territory, antennas (AS, ATI, AE) emit waves to respective coverage areas in which receivers (RQ, RB) measure characteristics of the emitted waves and transmit to a central server (SC) . The server analyzes the characteristics (CO) as a function of prediction models for broadcasting waves in the territory in order to determine adjustment parameters for the antennas. The server transmits the adjustment parameters to the antennas to control them in order to offer a greater diversity of radio broadcasting services and to optimize coverage areas according to different wave propagation modes.

Abstract: To broadcast synchronized radio waves in at least one frequency band in a predetermined territory, antennas (AS, ATI, AE) emit waves to respective coverage areas in which receivers (RQ, RB) measure characteristics of the emitted waves and transmit to a central server (SC) . The server analyzes the characteristics (CO) as a function of prediction models for broadcasting waves in the territory in order to determine adjustment parameters for the antennas. The server transmits the adjustment parameters to the antennas to control them in order to offer a greater diversity of radio broadcasting services and to optimize coverage areas according to different wave propagation modes.

Abstract: To avoid searching for a new location for very high hectometric wave antennas, an antenna according to the invention comprises an existing vertical structure having a height of at least approximately ten meters and including at least one electrically conductive element connected to the ground, and an excitation conductor wire (4a) that is essentially electrically conductive, disposed at least in part in the vicinity of and outside the structure and connected to a emitter (E) so that the structure radiates substantially hectometric waves. The existing structure may be a broadcasting tower, a water tower, a chimney, a lighthouse or a lamp standard, wherein the excitation wire merges visually. The wire can be replaced by a conductive loop a few meters long, magnetically coupled to the structure.

Abstract: To avoid searching for a new location for very high hectometric wave antennas, an antenna according to the invention comprises an existing vertical structure having a height of at least approximately ten meters and including at least one electrically conductive element connected to the ground, and an excitation conductor wire (4a) that is essentially electrically conductive, disposed at least in part in the vicinity of and outside the structure and connected to a emitter (E) so that the structure radiates substantially hectometric waves. The existing structure may be a broadcasting tower, a water tower, a chimney, a lighthouse or a lamp standard, wherein the excitation wire merges visually. The wire can be replaced by a conductive loop a few meters long, magnetically coupled to the structure.

Abstract: A variable helical antenna comprises coaxial conductive first and second helices extending in the same direction. The helices have first portions interleaved with each other without being in mechanical contact. A fixed protection member made in insulative material contains at least a portion of the first helix. A second member made in insulative material is screwed to the first member and contains at least a portion of the second helix. The second helix is attached to the second member. On screwing/unscrewing, the second helix is moved helically, by sliding on itself, relative to the first helix in order to tune the antenna to a required frequency indicated on a graduation on the fixed protection member.

Abstract: An antenna comprises a quarter-wavelength skirt antenna adapted to be disposed over an artificial ground and comprising a vertical cylindrical tube closed at the upper end and a coaxial feed inside the tube. The radiation pattern of the skirt antenna is essentially omnidirectional with a low elevation angle. The skirt antenna is combined with a helical antenna disposed vertically above the skirt antenna and coaxially therewith. The surface closing the upper part of the tube of the skirt antenna constitutes a reflective plane for the helical antenna favoring a hybrid radiation mode specific to the latter, partially axial and partially radial, by lowering the receive lobe of the radiation pattern towards an elevation angle suitable for receiving signals transmitted via satellite. A coupling device combines the signals received by each of the two antennas and feeds them to a common coaxial line.

Abstract: A resonant loop current disturbing probe. This probe comprises a conductive loop closed on a photoresistor, a light-emitting diode optically coupled to the photoresistor by an optical fiber and a diode control circuit. This probe is characterized in that it also comprises a variable capacitor connected in parallel to the loop. The loop-capacitor assembly forms a resonant circuit, the capacitor being adjusted in such a way that said circuit resonates at the frequency of the current to be disturbed. Application is to the measurement of the current in antennas.

Abstract: Circuit for analyzing an amplitude-modulated electric signal. This circuit comprises a quartz oscillator operating at a frequency fq, a frequency transposer making it possible to transpose the spectrum of the incident signal about fq, a narrow filter centered on one of the side bands, a detector receiving said side band and the reference signal at frequency fq and two processing channels, one being an amplitude channel and the other a phase channel.Application of the measurement of the current in an antenna, to the characteristics of quadripoles, impedances, etc.