EP0649182A1 - Broadcasting assembly comprising a rotatable dipole antenna with rigid dipoles and rotary joint for this assembly - Google Patents

Abstract

The present invention relates to radio broadcasting with the aid of rotatable antennae with rigid dipoles. Two separate feed channels (G1, J, 1g, 2g, 3g, 4g - G2, J, 1d, 2d, 3d, 4d) each pass through the joint (J) which separates the fixed part from the moving part of the antenna, and rise vertically within the mast so as to arrive respectively at two separate vertical groups of dipoles; it is thus possible to carry out two simultaneous transmissions from the same rotatable antenna. Application to shortwave radio broadcasting. <IMAGE>

Description

The present invention relates to broadcasting assemblies comprising a rotary antenna with rigid dipoles and which are designed to work in HF.

Such assemblies exist, their rotary antenna comprises a fixed base surmounted by a vertical mast which, associated with horizontal beams, generally supports two parallel vertical curtains of rigid dipoles, separated by one or two vertical curtains of horizontal wires which play the role of wave reflectors; some antennas have only one curtain of dipoles associated with a curtain of wires. Each of the dipole curtains with its reflector constitutes an antenna proper of which, in certain applications, a part of the dipoles can, as desired, be or not be supplied and this thanks to switching assemblies. In what follows, the complete assembly with the dipole curtains and the reflective curtain (s) will be said to be a rotating antenna each time it is necessary to avoid confusion with the two antennas proper also called antenna faces. or dipole curtains or high range antenna and low range antenna. These latter denominations account for the fact that the two dipole curtains of a rotary antenna are designed to work one at high frequencies, for example in the bands 13/15/17/21 / 26MHz located between 13,600 and 26,100 MHz and the other at low frequencies, for example in the bands 6/7/9/11 MHz located between 5,950 and 12,050 MHz.

The dipoles of each of the two curtains are generally arranged in rows and columns, symmetrically with respect to the projection of the axis of the mast in the plane of the curtain. As for the supply of the dipoles, it is ensured using supply lines (feeders in the English literature) which, passing inside the mast, make connections between an emission source located at the ground level and one or the other of the two dipole curtains.

Rotary antennas in use today use only one source of emission at a time. This is the case, in particular, in high power broadcasting. However, given the price of a broadcasting antenna whose height reaches several tens of meters, it would be interesting to be able to use them in combination with two emission sources transmitting simultaneously. Broadcasting stations are now transmitting more and more in frequency duality in the same direction; that is to say that the same program is transmitted in the same direction on two different frequencies, for example 6 and 7 MHz; for this it is known to use two rotary antennas each with a transmitter. It is therefore an expensive solution to transmit the same program in frequency duality, since it requires two rotary antennas and that a rotary antenna is very expensive.

• deux émissions sur une face de l'antenne rotative respectivement selon deux fréquences différentes,
• une émission sur une face complète de l'antenne rotative selon une même fréquence,

et, en plus, dans le cas d'une antenne rotative à deux rideaux de dipôles, dans la configuration suivante
   - deux émissions : une sur une face de l'antenne rotative selon une première fréquence et une sur l'autre face selon une seconde fréquence différente de la première ; il est à noter que, lorsque les deux rideaux de dipôles sont séparés par deux rideaux réflecteurs distincts, l'un uniquement pour les fréquences hautes, l'autre uniquement pour les fréquences basses, les fréquences d'émission sur les deux faces peuvent être les mêmes sous réserve qu'au moins une bande de fréquences soit commune aux fréquences hautes et aux fréquences basses.The object of the present invention is to avoid this drawback by proposing a broadcasting assembly comprising a single rotary antenna with rigid dipoles, but capable of working in at least the following two configurations.

• two transmissions on one side of the rotating antenna respectively at two different frequencies,
• an emission on a complete face of the rotary antenna according to the same frequency,

and, in addition, in the case of a rotary antenna with two dipole curtains, in the following configuration
- two transmissions: one on one side of the rotary antenna at a first frequency and one on the other side at a second frequency different from the first; it should be noted that, when the two dipole curtains are separated by two separate reflective curtains, one only for the high frequencies, the other only for the low frequencies, the emission frequencies on the two sides can be the same provided that at least one frequency band is common to the high frequencies and to the low frequencies.

This is obtained, in particular, by giving a vertical part of the rotary antenna a supply line independent of that intended for the other vertical part.

According to the invention this is obtained, in particular, with an antenna as described in claim 1 of this document.

According to the invention this is facilitated by the use of a seal as described in claim 6 of this document.

• - les figures 1 et 2, un ensemble de radiodiffusion pour la mise en oeuvre de l'invention,
• - la figure 3, des moyens pour la mise en oeuvre de l'invention dans l'ensemble selon les figures 1 et 2
• les figures 4 à 7 des vues de détail d'éléments de la figure 3.

The present invention will be better understood and other characteristics will appear from the following description and the figures relating thereto which represent:

• FIGS. 1 and 2, a broadcasting unit for implementing the invention,
• - Figure 3, means for implementing the invention as a whole according to Figures 1 and 2
• FIGS. 4 to 7 are detailed views of the elements of FIG. 3.

In the various figures, the corresponding elements are designated by the same references.

Figures 1 and 2 show a broadcasting set with a rotary, double, HF antenna, 82 meters high and 76 meters wide, which includes a support and two antennas proper: a low range antenna working in radio bands from 6 to 11 MHz and a high range antenna working in the radio bands from 11 to 26 MHz.

The support comprises a hollow base, in masonry, forming a room, L, inside which are placed transmitters and a mechanical assembly with a drive shaft which rotates a crown C arranged on the roof of the room. This crown is integral with the lower end of a vertical mast M on which are fixed four horizontal beams P1 to P4 arranged in the same vertical plane; forty beams such as b1 to b4 and B1 to B6 are fixed to these beams at one of their ends. Rigid bars constituting crutches, such as T1 and T2, or spacers, such as T3 are mounted at the ends of the beams P1 to P4, and are arranged substantially in the plane of these beams; the two spacers such as T3, allow the beam P2 to support the beam P1. Guy lines, such as H1 and H2, connect the beams to the mast at an oblique angle. The mast has three parts: a vertical cylindrical barrel with circular cross section, M1, surmounted by a vertical lattice beam, M2, itself surmounted by an assembly M3 formed by two bars welded at one of their ends for form an acute angle with point facing upwards.

The low range antenna is an antenna of the HR 4/4 / 0.5 type, that is to say that it comprises a curtain of rigid horizontal dipoles, H, at reflector, R, with 4 half-wave dipoles folded over per line and 4 per column in the curtain and with a height of the first line of dipoles from the ground equal to 0.5 times the average operating wavelength of this antenna. The dipole curtain of the low range antenna thus consists of 16 dipoles, d1 to d16, fixed on the free ends of 16 of the 40 beams, like the beams b1 to b4; these dipoles are arranged in the same vertical plane parallel to the vertical plane of the beams P1 to P4. It is between the vertical plane of the dipoles d1 to d16 and the vertical plane of the beams or, more exactly, in the plane of the front faces of the beams P1 to P4 that a third vertical plane, parallel to the first two, is arranged. 'a layer of horizontal wires and constituting the reflector Rb of the low range antenna; the horizontal wires of this reflector are held by an edge cable C1 which passes through the top of the mast and through the free ends of the bars constituting crutches such as T1 and T2; the spacing between the horizontal wires of the reflector Rb is kept using vertical cables such as K1, on which the horizontal wires are fixed at regular intervals. The reflector Rb of the low range antenna has not been drawn in its entirety in FIG. 1, so as to allow the high range antenna which is placed behind it to be seen, and, in FIG. 2, it has been represented schematically by a dashed line which symbolizes its trace in the plane of the figure.

The high range antenna is an antenna of the HR 4/6 / 0.75 type, that is to say that it comprises a curtain of rigid horizontal dipoles, H, with reflector, R, with 4 half-wave dipoles folded over by line and 6 per column in the curtain and with a height of the first line of dipoles from the ground equal to 0.75 times the average operating wavelength of this antenna. The dipole curtain of the high range antenna therefore consists of 24 dipoles, D1 to D24, fixed on the free ends of 24 of the 40 beams, like the beams B1 to B6; these dipoles are arranged in the same vertical plane parallel to the vertical plane of the beams P1 to P4. As for the reflector, Rh, of the high range antenna it is made of a vertical sheet of horizontal wires arranged in the plane of the rear faces of the beams P1 to P4, between the reflector Rb and the dipole network of the range antenna high. The horizontal wires of the Rh reflector are held in a frame delimited by the upper beam P1 and by border cables such that C2; these cables are held at their lower end by two crutches, such as T4, secured at one of their ends to the lower beam P4; the spacing between the horizontal wires of the reflector Rh is kept using vertical cables such as K2, on which the horizontal wires are fixed at regular intervals. Like the reflector Rb, the reflector Rh has not been shown in its entirety in FIG. 1 in order to reveal the dipole curtain of the high range antenna which is behind it, and, in FIG. 2, it has been represented schematically by a dashed line which symbolizes its trace in the plane of the figure.

FIG. 3 is the diagram of the supply of the dipoles of the rotary antenna of FIGS. 1 and 2 as it is produced within the framework of the invention. In this figure, the proportions have not been respected to facilitate representation and understanding.

The supply according to FIG. 3 is done from two transmitters E1, E2 arranged inside the room L which was discussed during the description of FIGS. 1 and 2. This supply comprises a fixed part, located in the room L and a rotating part located in the vertical mast of the antenna, these two parts being separated by a "double-coaxial" rotating joint, J, placed in the center of the crown C of the antenna and having the same axis of vertical rotation as this crown.

The transmitters E1, E2 each comprise an output circuit constituted by an impedance matching unit, A1, A2, and are each connected by a coaxial cable, G1, G2, to two coaxial inputs of the rotary joint J. In the coaxial cables G1, G2 are introduced measurement probes connected to a phase comparator, N; this phase comparator is used, when it is put into service, to control the transmitters E1, E2 so that they transmit in phase.

• aux points d'alimentation des dipôles D24, D23, D20, D19, D16, D15
• aux points d'alimentation des dipôles D24, D23, D20, D19, D16, D15, D12, D11
• aux points d'alimentation des dipôles D 24, D23, D20, D19, D16, D15, D12, D11, D8, D7, D4, D3,
• à la première extrémité d'une ligne bifilaire 3g.

The joint J is described below using FIGS. 4 and 5. It has two coaxial outputs connected respectively by two baluners 1d, 1g, to the common points of two high range double switches, with four positions, 2d, 2g. The high range switch 2g has two groups of three wafers and the four double positions of these switches are respectively connected by two-wire lines

• at the dipole supply points D24, D23, D20, D19, D16, D15
• at the dipole supply points D24, D23, D20, D19, D16, D15, D12, D11
• at the dipole supply points D 24, D23, D20, D19, D16, D15, D12, D11, D8, D7, D4, D3,
• at the first end of a 3g line.

The high range switch 2d is identical to the switch 2g and is symmetrically connected to the dipoles D21, D22, D17, D18, D13, D14, D9, D10, D5, D6, D1, D2 and to the first end of a 3d two-wire line.

• aux points d'alimentation des dipôles d13, d14, d9, d10,
• aux points d'alimentation des dipôles d13, d14, d9, d10,d5, d6,
• aux points d'alimentation des dipôles d13, d14, d9, d10, d5, d6, d1, d2.

The second ends of the 3d, 3g two-wire lines are respectively connected to the common points of two low range double switches with three positions, 4d, 4g. Each low range switch has two groups of three wafers and the three double positions of the 4g switch are connected by two-wire lines

• at the dipole supply points d13, d14, d9, d10,
• at the dipole supply points d13, d14, d9, d10, d5, d6,
• at the dipole supply points d13, d14, d9, d10, d5, d6, d1, d2.

The low range switch 4d is identical to the 4g switch and is symmetrically connected to the dipoles d16, d15, d12, d11, d8, d7, d4, d3.

A metal plate, 5, placed inside the mast of the rotary antenna provides electromagnetic shielding between the two parts of the power supply paths in the paths located in the mast M, above the joint J, it is that is, in the paths from the baluns, where the supply lines pass from coaxial to two-wire.

Figures 4 and 5 are views of the seal J of Figure 3. The seal consists of two identical half-seals, each of them constituting a half-housing; these half-housings are located on either side of a line XX in FIG. 4 and in sliding contact according to a circular zone situated in a plane perpendicular along XX to the plane of FIG. 4; that of the half-housings which is located below the line XX, is secured to the room L shown in Figures 1 and 2, while that which is located above the line XX is secured to the rotating part of the rotating antenna. FIG. 5 shows the half-joint integral with the room, that is to say the fixed half-joint; it is seen from above in this figure; it comprises a metal half-housing, J5, with two coaxial sockets J1, J2. The outer conductor of the coaxial sockets is soldered to the half-housing and the inner conductor extends first vertically and then horizontally by a crescent-shaped pallet, J1 ', in the half-housing; the pallet is intended to ensure sliding contact in the plane which already contains the sliding contact zone between the two half-housings. In the same way the upper half-joint comprises a metal half-housing J6 and two coaxial sockets J3, J4 with pallet J3 ', J4', but only the socket J3 appears in FIG. 4: the socket J4 is hidden by the socket J3 since, in this figure, the half-housings are tilted 90 ° relative to each other. The position shown in Figure 4 is that where the pallets of the outlet sockets, J3, J4, of the joint, exactly cover the pallets, J1, J2, of the inlet sockets; to facilitate understanding of the drawing, only the parts of the sockets J2, J3 contained in the housing J have been shown as seen by transparency.

FIG. 6 represents a balun of known type as it is in particular described in the French patent 2,556,508 filed on December 13, 1983 and as it is used to constitute the baluns 1d, 1g according to FIG. 3. It s 'Acts of a balun for coupling a coaxial line to a two-wire line and which comprises in series a section of coaxial cable 10 and a symmetrical two-wire line 12, with a conductor 13 in parallel on the section of coaxial cable. In this balun, the symmetrical line 12, of length L, is designed to have, between its ends, a variation in impedance, Z = f (x) with x between zero and the length of line 12, which, in coordinates straight planes, shaped like an S.

In FIG. 3, the baluns 1d, 1g are shown with the two symmetrical two-wire line elements seen from above but slightly offset while in FIG. 6 the two elements of the symmetrical two-wire line are shown from the side. On the other hand, in these two figures, the conductors, such as 13 in FIG. 6, have each time been represented in the plane of the figure in order to prevent them from merging with the output of the internal conductor of the section of coaxial cable.

Zo, alimente un premier groupe formé des dipôles D15, D16, D19, D20, D23, D24 ; la ligne L2, d'impédance caractéristique 2Zo, alimente le deuxième groupe formé des dipôles D11, D12 et la ligne L3, d'impédance caractéristique Zo, alimente le troisième groupe formé des dipôles D3, D4, D7, D8. Les lignes L1, L2, L3 aboutissent respectivement aux accès de répartition constitués par les bornes 1a, 2 et 3 du commutateur 2g, qui comporte neuf bornes, 1a, 1b, 2-8, et des liaisons fixes ou mobiles entre certaines de ces bornes. Ces liaisons sont destinées à permettre l'alimentation, soit de la seule ligne L1, soit des lignes L1 et L2, soit des lignes L1, L2 et L3, soit de la ligne 3g d'impédance $\frac{\text{2}}{\text{3}}$

Zo, à partir d'une ligne d'alimentation E d'impédance caractéristique $\frac{\text{2}}{\text{3}}$

Zo, aboutissant à l'accès commun que constitue la borne 7 ; cette ligne E est la ligne provenant du symétriseur 1g de la figure 3.Figure 7 will describe the operation of the switch 2g. This figure shows that the dipoles D3, D4, D7, D8, D11, D12, D15, D16, D19, D20, D23, D24 form three groups supplied respectively by three distinct lines L1, L2, L3. Line L1, of characteristic impedance $\frac{\text{2}}{\text{3}}$

Zo, feeds a first group made up of dipoles D15, D16, D19, D20, D23, D24; line L2, of characteristic impedance 2Zo, feeds the second group formed of dipoles D11, D12 and line L3, of characteristic impedance Zo, feeds the third group formed of dipoles D3, D4, D7, D8. Lines L1, L2, L3 lead respectively to the distribution accesses constituted by terminals 1a, 2 and 3 of switch 2g, which has nine terminals, 1a, 1b, 2-8, and fixed or mobile links between some of these terminals . These links are intended to allow the supply, either of the single line L1, or of the lines L1 and L2, or of the lines L1, L2 and L3, or of the line 3g of impedance $\frac{\text{2}}{\text{3}}$

Zo, from a supply line E of characteristic impedance $\frac{\text{2}}{\text{3}}$

Zo, culminating in the common access constituted by terminal 7; this line E is the line coming from the balun 1g of FIG. 3.

Terminal 7 is coupled to a mobile arm which, by pivoting, can take four positions, three of which are represented respectively by a series of crosses, by a series of lines and by a series of points; Similarly, terminal 2 is coupled to two movable arms which, by pivoting, can each take four positions, three of which are represented respectively by sequences of crosses, lines and dots.

The three mobile arms are mechanically linked so that they can only take one of four positions simultaneously: the three positions identified by crosses, by lines, or by dots and a fourth position where only the connection between the terminals 7 and 8 are provided in order to directly connect line E to line 3g.

Zo.Terminals 1a and 1b are connected by a very short line, H, of uniform characteristic impedance $\frac{\text{2}}{\text{3}}$

Zo.

In the first position, marked with crosses, terminal 7 is connected to terminal 1b and terminal 1a is not connected to terminal 2 so that only line L1 and, therefore, the dipoles D15, D16, D19 , D20, D23, D24 are supplied.

Zo et les lignes L1, L2, d'impédances caractéristiques respectives $\frac{\text{2}}{\text{3}}$

Zo et 2Zo. Comme les lignes L1 et L2 sont alimentées en parallèle, elles correspondent à une ligne unique, d'impédance caractéristique $$\frac{\frac{\text{2}}{\text{3}}\text{Zox2Zo}}{\frac{\text{2}}{\text{3}}\text{Zo + 2Zo}}\text{=}\frac{\text{Zo}}{\text{2}}$$

; le transformateur Tr1 est donc prévu pour assurer la transformation de $\frac{\text{2Zo}}{\text{3}}$

à $\frac{\text{Zo}}{\text{2}}$

.In the second position, marked by lines, terminal 7 is connected to terminal 5 and terminal 2 to terminals 1a and 4. As, between terminals 4 and 5, an impedance transformer Tr1, establishes a fixed link, the lines L1 and L2 and, therefore the dipoles D11, D12, D15, D16, D19, D20, D23, D24 are supplied while the dipoles D3, D4, D7, D8 are not supplied. The impedance transformer Tr1 is a broadband transformer, intended to ensure the impedance matching between the line E of characteristic impedance $\frac{\text{2}}{\text{3}}$

Zo and lines L1, L2, of respective characteristic impedances $\frac{\text{2}}{\text{3}}$

Zo and 2Zo. As lines L1 and L2 are supplied in parallel, they correspond to a single line, of characteristic impedance $$\frac{\frac{\text{2}}{\text{3}}\text{<figure-callout id="2" label="Zox2Zo" filenames="imgf0004.png" state="{{state}}">Zox2Zo</figure-callout>}}{\frac{\text{2}}{\text{3}}\text{Zo + 2Zo}}\text{=}\frac{\text{<figure-callout id="2" label="Zo" filenames="imgf0004.png" state="{{state}}">Zo</figure-callout>}}{\text{2}}$$

; the transformer Tr1 is therefore provided to ensure the transformation of $\frac{\text{<figure-callout id="3" label="2Zo" filenames="imgf0004.png" state="{{state}}">2Zo</figure-callout>}}{\text{3}}$

at $\frac{\text{<figure-callout id="2" label="Zo" filenames="imgf0004.png" state="{{state}}">Zo</figure-callout>}}{\text{2}}$

.

Zo et les lignes L1, L2, L3 d'impédances caractéristiques respectives $\frac{\text{2}}{\text{3}}$

Zo, 2Zo et Zo. Comme les lignes L1, L2, L3 sont alimentées en parallèle, elles correspondent à une ligne unique, d'impédance caractéristique $$\frac{\frac{\text{2}}{\text{3}}\text{Zox2ZoxZo}}{\frac{\text{2}}{\text{3}}\text{Zox2Zo +}\frac{\text{2}}{\text{3}}\text{ZoxZo + 2ZoxZo}}\text{=}\frac{\text{Zo}}{\text{3}}\text{;}$$

le transformateur Tr2 est donc prévu pour assurer la transformation de $\frac{\text{2}}{\text{3}}$

Zo à $\frac{\text{Zo}}{\text{3}}$

.In the third position, marked with dots, terminal 7 is connected to terminal 6 and terminal 2 to terminals 1a and 3. As between terminals 3 and 6, an impedance transformer, Tr2, establishes a fixed link , the three lines L1, L2, L3 and, therefore, the eight dipoles are supplied. The transformer Tr2 is also a broadband impedance transformer, intended to ensure the impedance matching between the line E of characteristic impedance $\frac{\text{2}}{\text{3}}$

Zo and the lines L1, L2, L3 of respective characteristic impedances $\frac{\text{2}}{\text{3}}$

Zo, 2Zo and Zo. As lines L1, L2, L3 are supplied in parallel, they correspond to a single line, of characteristic impedance $$\frac{\frac{\text{2}}{\text{3}}\text{<figure-callout id="2" label="Zox2ZoxZo" filenames="imgf0004.png" state="{{state}}">Zox2ZoxZo</figure-callout>}}{\frac{\text{2}}{\text{3}}\text{Zox2Zo +}\frac{\text{2}}{\text{3}}\text{ZoxZo + 2ZoxZo}}\text{=}\frac{\text{<figure-callout id="3" label="Zo" filenames="imgf0004.png" state="{{state}}">Zo</figure-callout>}}{\text{3}}\text{;}$$

the transformer Tr2 is therefore provided to ensure the transformation of $\frac{\text{2}}{\text{3}}$

Zo to $\frac{\text{<figure-callout id="3" label="Zo" filenames="imgf0004.png" state="{{state}}">Zo</figure-callout>}}{\text{3}}$

.

Switch 2d is identical to switch 2g and switches 4d, 4g are wired to ensure the HR 2/2, HR 2/3 and HR 2/4 configurations respectively in their three positions; these three switches will therefore not be described in more detail.

The rotary antenna which has just been described therefore makes it possible to emit according to several configurations of half-curtains and to choose from the four right or left half-curtains, the one which will be connected to the emitter E1 shown in Figure 3 and the one that will be connected to the transmitter E2. It is understood that a transmitter can just as easily be connected to a right half-curtain as to a left half-curtain, the connection being a function of the position of the mobile part of the rotary antenna relative to the fixed part. and that, for a given position of the rotary antenna, the transmitter E1, for example, can be connected either to the left half-curtain high range or to the right half-curtain low range.

• deux émissions dirigées dans des directions azimutales à 180 degrés l'une de l'autre, l'émetteur E1 émettant sur une fréquence F1 et étant relié, par exemple, au demi-rideau gauche gamme haute, l'émetteur E2 étant alors relié au demi-rideau gauche gamme basse ou gamme haute et émettant sur une fréquence F2 avec un écart suffisant entre F1 et F2 pour éviter les perturbations, par exemple |F1-F2| ≧ 0,1(F1+F2),
• deux émissions dirigées dans des directions azimutales à 180° l'une de l'autre, les deux émetteurs E1, E2 émettant sur la même fréquence ; dans ce cas un fort découplage entre les deux rideaux de dipôles doit être assuré ce qui nécessite que les deux réflecteurs Rb, Rh aient une hauteur et une largeur suffisantes vis-à-vis respectivement des rideaux de dipôles gamme basse et gamme haute et aient un pas entre les fils horizontaux qui les constituent suffisamment faible vis-à-vis respectivement des longueurs d'onde de la gamme basse et de la gamme haute.
• deux émissions dirigées dans une même direction azimutale, l'émetteur E1 émettant sur une fréquence F1 et étant relié, par exemple, au demi-rideau gauche gamme basse, l'émetteur E2 étant alors relié au demi-rideau droit gamme basse et émettant sur une fréquence F2 avec, là encore, un écart de fréquence suffisant pour éviter les perturbations, par exemple |F1-F2| ≧ 0,1(F1+F2),
• une même émission sur un rideau complet de l'antenne rotative, c'est-à-dire sur tout le rideau gamme haute ou tout le rideau gamme basse, l'émetteur E1 alimentant par exemple le demi-rideau gauche gamme basse et l'émetteur E2 le demi-rideau droit gamme basse ; pour ce type d'émission les puissances de sortie des deux émetteurs doivent être ajustées à la même valeur et les signaux de sortie de ces émetteurs doivent être en phase ; cette identité de phase est obtenue à l'aide du comparateur de phase N selon la figure 3 qui, de manière classique règle les phases respectives des émetteurs E1, E2 de manière à rendre nul l'écart de phase entre les signaux qu'il mesure à l'aide de ses deux sondes.

Given these possibilities offered by the rotary antenna which has just been described, four types of transmissions can be carried out:

• two transmissions directed in azimuthal directions 180 degrees from each other, the transmitter E1 transmitting on a frequency F1 and being connected, for example, to the left half-curtain high range, the transmitter E2 being then connected to the half-curtain left low range or high range and emitting on a frequency F2 with a sufficient gap between F1 and F2 to avoid disturbances, for example | F1-F2 | ≧ 0.1 (F1 + F2),
• two transmissions directed in azimuthal directions at 180 ° from each other, the two transmitters E1, E2 transmitting on the same frequency; in this case a strong decoupling between the two dipole curtains must be ensured which requires that the two reflectors Rb, Rh have a sufficient height and width vis-à-vis the low range and high range dipole curtains and have a not between the horizontal wires which constitute them sufficiently weak vis-à-vis the wavelengths of the low range and the high range respectively.
• two emissions directed in the same azimuthal direction, the transmitter E1 transmitting on a frequency F1 and being connected, for example, to the left half curtain of low range, the transmitter E2 being then connected to the right half curtain of low range and transmitting on a frequency F2 with, here again, a frequency difference sufficient to avoid disturbances, for example | F1-F2 | ≧ 0.1 (F1 + F2),
• the same emission on a complete curtain of the rotary antenna, that is to say on all the curtain high range or all the curtain low range, the transmitter E1 supplying for example the left half curtain of low range and the transmitter E2 the low range right half curtain; for this type of transmission, the output powers of the two transmitters must be adjusted to the same value and the output signals of these transmitters must be in phase; this phase identity is obtained using the phase comparator N according to FIG. 3 which conventionally adjusts the respective phases of the emitters E1, E2 so as to make the phase difference between the signals which it measures zero using its two probes.

• deux émissions dirigées dans une même direction azimutale,
• une émission sur le rideau complet.

The present invention is not limited to the example described. It is thus, in particular that it is possible to simultaneously transmit the entire high range curtain in one direction and the entire low range curtain in the opposite direction by adding, in FIG. 3, a first switch at the input of the switch 2g in order to derive part of the signal from the transmitter E1 to the input of the switch 2d, and a second switch at the input of the switch 2d in order to allow the connection between the transmitter E2 and the switch 2d to be interrupted and replace it with a link between the transmitter E2 and the inputs of switches 4d and 4g.
The invention can also be applied to a rotary antenna comprising only a single curtain of dipoles in order to allow two types of emission:

• two programs directed in the same azimuth direction,
• a show on the full curtain.

Likewise the dipole switches can be deleted, this is how in the described embodiment the switches 4d, 4g can be deleted and the switches 2d, 2g replaced by a two-position switch to choose between the high range curtain and the curtain low range.

Claims (6)

Broadcasting assembly constituted by transmission means associated with a rotary antenna comprising a support with a fixed base (L), a vertical mast (M) and a rotary joint (J) disposed between the base and the mast, and n, with n positive integer less than 3, parallel vertical curtains of rigid dipoles (d1-d16, D1-D24) integral with the mast, each associated with a reflective curtain (Rb, Rh), in which supply means, part of which of the path passes through the joint and the mast, are provided to supply the dipoles of the dipole curtains, characterized in that the emission means comprise two transmitters (E1, E2) each with an impedance adaptation unit at the output (A1, A2), in that the supply means comprise two separate channels (G1, J, 1g, 2g, 3g, 4g - G2, J, 1d, 2d, 3d, 4d), which start respectively from the two transmitters , cross the joint and go up inside the mast up to the level of the dipoles, to supply respective at least some of the dipoles of two separate vertical portions of the n dipole curtains and which, in their passage through the mast, each include a balun (1g, 1d) and in that the joint (J) is a bi-coaxial joint . Broadcasting assembly according to claim 1, characterized in that a metal partition (5) separates the two channels when they pass through the mast. Broadcasting unit according to one of the preceding claims, in which n is equal to 2, characterized in that the channels include a channel switch (4d, 4g) in order to allow to choose, for each channel, if the distinct vertical portion will belong to one or the other of the two dipole curtains. Broadcasting assembly according to one of the preceding claims, characterized in that the channels include connection means (2d, 2g, 4d, 4g) to allow, in the separate vertical portions where the two channels terminate, to connect only part of the dipoles. Broadcasting assembly according to one of the preceding claims, characterized in that it comprises a control circuit (N) for measuring the phase difference between the output signals of the two transmitters (E1, E2) and control the two transmitters so that this phase difference is canceled. Rotary joint designed for a broadcasting assembly equipped with a rotary antenna with rigid dipoles and comprising a metal housing made of two half-housings in contact in a circular planar area, one (J5) of the half-housings being fixed, l other (J6) which can rotate while maintaining the contact according to the circular zone, characterized in that it comprises two coaxial ports (J1, J2) per half-housing, these ports each having an external conductor in electrical contact with its half -box and an inner conductor which penetrates into its half-box and in that at least two of the four inner conductors of the four accesses of the box are extended in the box by sliding contacts (J1 ', J2', J3 '), parallel to the flat area, to provide two electrical connections starting respectively on the two ports of one of the half-boxes and ending respectively on the two ports of the other of the half-boxes.

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