EP0649183A1 - Broadcoasting assembly comprising a rotatable antenna with dipoles in wire form and rotaty joint for this assembly - Google Patents

Abstract

The present invention relates to radio broadcasting with the aid of rotatable antennae with wire dipoles. Two separate feed channels (G1, J, G4, Sg, Qg, Khg, Kbg; G2, J, G3, Sd, Qd, KHd, Kbd) start respectively from two transmitters (E1, E2) pass through the joint (J) which separates the fixed part from the moving part of the rotatable antenna, then leave horizontally, on either side of the mast, bearing on the support structure of the rotatable antenna, and then again rise vertically to the feed points of the dipoles of two separate vertical groups of dipoles; it is thus possible to carry out two simultaneous transmissions from the same rotatable antenna. Application to shortwave broadcasting. <IMAGE>

Description

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

Such sets exist, their rotary antenna has a fixed base surmounted by a vertical mast which, associated with horizontal beams, generally supports two parallel vertical curtains of wire 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 frequency antenna and low frequency 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 61719111 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 by means of a supply line (feeder in Anglo-Saxon literature) which makes connections between an emission source located at ground level and one, either of the two curtains of wired dipoles; for this a power cable starts from the power source, crosses the rotary crown which separates the fixed base and the mast, is subdivided into two cables which run horizontally following two horizontal beams integral with the mast and is subdivided again to leave, vertically, supplying the different dipoles. It should be noted that it is known to use switches in this supply line to authorize or prohibit the supply of some of the dipoles of the antenna in order to use only one curtain when there are two, or to use only all or part of the dipoles a curtain in order to vary the angle of elevation of the curtain in question.

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, taking into account the price of a broadcasting antenna whose height reaches several tens of meters, it would be interesting to be able to use them in association with two emission sources emitting 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, respectivement, deux demi-faces d'une face de l'antenne rotative, selon deux fréquences différentes,
• une émission sur une face complète de l'antenne rotative selon une fréquence donnée,

   et, en plus, dans le cas d'une antenne rotative à deux rideaux de dipôles, dans la configuration suivante
   - une émission sur une face de l'antenne rotative selon une première fréquence et une émission 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 wire dipoles, but capable of working in at least the following two configurations.

• two transmissions on, respectively, two half-faces of one face of the rotary antenna, according to two different frequencies,
• an emission on a complete face of the rotary antenna according to a given frequency,

and, in addition, in the case of a rotary antenna with two dipole curtains, in the following configuration
- A transmission on one side of the rotary antenna according to a first frequency and a transmission on the other side according to 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 5 of this document.

• les figures 1 à 3, un ensemble de radiodiffusion pour la mise en oeuvre de l'invention,
• la figure 4, des moyens pour la mise en oeuvre de l'invention dans l'ensemble selon les figures 1 à 3
• les figures 5 à 10 des vues de détail pour préciser ou compléter la figure 4.

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 to 3, a broadcasting assembly for implementing the invention,
• Figure 4, means for implementing the invention as a whole according to Figures 1 to 3
• Figures 5 to 10 detailed views to clarify or supplement Figure 4.

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

• un premier rideau vertical formé de demi-dipôles horizontaux, d1 à d16, associés par paires telles que d1-d5 ; ce rideau de dipôles est vu de face sur la figure 1,
• une nappe verticale, N, de fils horizontaux,
• un second rideau vertical formé de demi-dipôles horizontaux, D1 à D16, associés par paires telles que D1-D5 ; ce rideau de dipôles est vu de face sur la figure 2.

Figures 1, 2 and 3 show a double rotary antenna, for HF, 85 meters high and 76 meters wide. This antenna comprises a support and two antennas proper. The support comprises a fixed mast foot, P, surmounted by a rotating crown C, itself surmounted by a vertical mast, M, to which are fixed three pairs of horizontal arms B1-B2, B3-B4 and b1-b2 . The mast and the six arms are used to support, in three parallel planes, using cables:

• a first vertical curtain formed by horizontal half-dipoles, d1 to d16, associated in pairs such as d1-d5; this dipole curtain is seen from the front in FIG. 1,
• a vertical sheet, N, of horizontal threads,
• a second vertical curtain formed by horizontal half-dipoles, D1 to D16, associated in pairs such as D1-D5; this dipole curtain is seen from the front in FIG. 2.

This double A antenna is an antenna of the HR 4/4 / 0.5 type for the face visible in FIG. 1, the half-dipoles d1 to d16 constituting, with the ribbon cable N, a low frequency antenna intended to work in the 6-7-9-11 MHz frequency bands, i.e. in frequencies ranging from 5,950 to 12,050 MHz.

The double A antenna is of the HR 4/4/1 type for the face visible in FIG. 2, the half-dipoles D1 to D16 constituting with the ribbon cable N, a high frequency antenna intended to work in the frequency bands of the 11 -13-15-17-21-26 MHz, i.e. in frequencies ranging from 11,650 to 26,100 MHz. In this high-frequency antenna, as it appears in FIGS. 2 and 3, the curtain of dipoles makes half-dipoles D1 to D16, is less than half as high and half as wide as the ribbon cable N and is partially supported by the auxiliary arms b1, b2.

The sheet N has two parts N 'and N' '; since the high frequency antenna of the double A antenna has a surface markedly smaller than the surface of the sheet N, this feature is taken advantage of, in order to give the wires of this sheet a small spacing only in the opposite part N ' the high frequency antenna; given that the part, N '', of the ribbon cable N, has a role to play only in the low frequency antenna, the spacing of its wires is twice as large as for the wires of part N ' .

The pair of lower arms B3-B4 constitutes a platform from which, in a conventional manner, supply cables (feeders in the Anglo-Saxon literature) run vertically to supply the dipoles; in the example described, these are cables forming vertical bundles which pass through the middle of the dipoles d4-d8, d12-d16, D4-D8, D12-D16 and then rise to the upper dipoles. The B3-B4 platform is wide, providing a passage for the antenna assembly and maintenance teams.

Figure 4 is the diagram of the dipole power supply of the rotary antenna of Figures 1 to 3 as it is produced in the context of the invention. In this figure, the proportions have not been respected to facilitate representation and understanding.

The supply, according to FIG. 4, is done from two transmitters E1, E2 arranged in a room, in the vicinity of the mast foot P which was discussed during the description of FIGS. 1 to 3. This supply comprises a fixed part which goes from the transmitters to a "double-coaxial" rotating joint, J, and a rotating part which goes from the joint J to the dipoles. Joint J is disposed in the center of the crown C shown in Figures 1 to 3; it has the same vertical axis of rotation as this crown.

The transmitters E1, E2 are each connected by a coaxial cable, G1, G2, to two coaxial inputs of the rotating 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.

The joint J is described below using FIGS. 5 and 6. It has two coaxial outputs connected, respectively by two coaxial cables G3, G4 followed by two baluns, Sd, Sg, at the common points of two band switches Qd and HQ. The band switches have two positions: a position in which they link with the common point of a high frequency switch Khd, Khg and a position in which they link with the common point of a low frequency switch Kbd , Kbg. The low frequency and high frequency switches include impedance transformers. The Kbg switch controls the supply of the dipoles d1-d5, d2-d6, d3-d7, d4-d8; the switch Kbd controls the supply of the dipoles d9-d13, d10-d14, d11-d15, d12-d16; the Khg switch controls the supply of dipoles D9-D13, D10-D14, D11-D15, D12-D16; the Khd switch controls the supply of dipoles D1-D5, D2-D6, D3-D7, D4-D8. Details on the making of these switches will be given using FIGS. 9 and 10.

Figures 5 and 6 are views of the seal J of Figure 3. The seal consists of two identical half-seals, each of them constituting a half-housing; the two half-housings are located on either side of a line XX in FIG. 5 and in sliding contact according to a circular zone situated in a plane perpendicular along XX to the plane of FIG. 5; that of the half-housings which is located below the line XX, is integral with the mast foot P shown in Figures 1 to 3, while it which is located above the line XX is integral with the rotating part of the rotating antenna. Figure 6 shows the half-joint integral with the mast foot, 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 is extended first vertically 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. 5: the socket J4 is hidden by the socket J3 since, in this figure, the half-housings are rotated 90 ° relative to each other. The position shown in FIG. 5 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. 7 represents a balun of known type as it is in particular described in French patent 2,556,508 filed on December 13, 1983 and as it is used to constitute the balancers Sd, Sg according to FIG. 4. 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. 4 the symmetrizers Sd, Sg are represented with the two elements of symmetrical two-wire line seen from above but slightly offset while in FIG. 7 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. 7, have each time been represented in the plane of the figure in order to prevent them from being confused with the output of the internal conductor of the coaxial cable section.

FIG. 8 schematically represents, in perspective and without again the proportions being respected, the mast M at the level of the beam B3 of the platform, the balun Sd which is held on the beam B3 by insulating spacers represented by broken lines, and the two-position switch, Qd, also fixed on beam B3. The two two-wire outputs of the Qd switch which are connected respectively at the switches Khd and Kbd, have been shown in strong lines, but these switches, which are also fixed on the beam B3, have not been shown; they will be described using FIGS. 9 and 10.

The switches Khd, Kbd, Khg, Kbg are all produced on the same model and are distinguished only by the impedance transformers which they comprise and which are different in the high frequency switches from those in the low frequency switches; thus only the switch Kbd which controls the supply of the dipoles d9-d13, d10-d14, d11-d15, d12-d16 and which is represented in FIGS. 9 and 10, will be described.

Figure 9 shows that the dipoles d9-d13, d10-d14, d11-d15, d12-d16 form three groups fed respectively by three distinct lines L1, L2, L3. Line L1, of characteristic impedance Zo, supplies a first group consisting of the two dipoles d11-d15 and d12-d16; line L2, of characteristic impedance 2Zo, feeds the second group made up of the dipole d10-d14 and line L3, also of characteristic impedance 2Zo, feeds the third group made up of the dipole d9-d13. Lines L1, L2, L3 lead respectively to the distribution accesses constituted by terminals 1a, 2 and 3 of the switch Kbd, which has eight terminals, 1a, 1b, 2-7, 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, from a supply line E of characteristic impedance Zo, leading the common access provided by terminal 7; this line E is the line coming from the balun Sd of FIGS. 4 and 8.

Terminal 7 is coupled to a mobile arm which, by pivoting, can take three positions 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 mobile arms which, by pivoting, can each take three positions also represented by sequences of crosses, lines and dots.

The three movable arms are mechanically linked in such a way that they can only assume simultaneously the three positions identified by crosses, or that those identified by lines, or that those identified by dots.

The terminals 1a and 1b are connected by a very short line, H, of uniform characteristic impedance 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 two dipoles d11-d15 and d12-d16 are powered.

le transformateur T1 est donc prévu pour assurer la transformation de $\frac{\text{2Zo}}{\text{3}}$

à Zo.In the second position, marked with 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, T1, establishes a fixed link , lines L1 and L2 and, therefore, the dipoles d10-d14, d11-d15, d12-d16 are supplied while the dipole d9-d13 is not supplied. The impedance transformer T1 is a broadband transformer, intended to ensure the impedance matching between the line E of characteristic impedance Zo and the lines L1, L2, of respective characteristic impedances Zo and 2Zo. As lines L1 and L2 are supplied in parallel, they correspond to a single line, of characteristic impedance $$\frac{\text{Zo x 2Zo}}{\text{Zo + 2Zo}}\text{=}\frac{\text{<figure-callout id="3" label="2Zo" filenames="imgf0006.png" state="{{state}}">2Zo</figure-callout>}}{\text{3}}\text{;}$$

the transformer T1 is therefore provided to ensure the transformation of $\frac{\text{<figure-callout id="3" label="2Zo" filenames="imgf0006.png" state="{{state}}">2Zo</figure-callout>}}{\text{3}}$

to Zo.

le transformateur T2 est donc prévu pour assurer la transformation de $\frac{\text{Zo}}{\text{2}}$

à Zo.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, T2, establishes a fixed link , the three lines L1, L2, L3 and, therefore, the four dipoles are supplied. The transformer T2 is also a broadband impedance transformer, intended to ensure the impedance matching between the line E of characteristic impedance Zo and the lines L1, L2, L3 of respective characteristic impedances Zo, 2Zo and 2Zo. As lines L1, L2, L3 are supplied in parallel, they correspond to a single line, of characteristic impedance $$\frac{\text{Zox2Zox2Zo}}{\text{Zox2Zo + Zox2Zo + 2Zox2Zo}}\text{=}\frac{\text{<figure-callout id="2" label="Zo" filenames="imgf0006.png" state="{{state}}">Zo</figure-callout>}}{\text{2}}\text{;}$$

the transformer T2 is therefore provided to ensure the transformation of $\frac{\text{<figure-callout id="2" label="Zo" filenames="imgf0006.png" state="{{state}}">Zo</figure-callout>}}{\text{2}}$

to Zo.

FIG. 10 shows, in a perspective view, how the switch Kbd of FIGS. 4 and 9 was made. The switch Kbd comprises a metal box B shown as if it were transparent; this box has the shape of a right prism whose section is constituted by a large equilateral triangle which is truncated, according to the same small equilateral triangle, at each of its three vertices. The different terminals, 1a, 1b, 2-7, of the switch Kbd are carried by the wall of the box.

The switch Kbd has, inside the box, three double arms, G ', G' ', G, mobile, mounted on an insulating axis, common, R, arranged on the right, not shown, which passes through the point center of the straight sections of the prism. The double arms G 'and G' 'rotate in two same planes parallel to the bases of the prism; they are 120 ° from each other and are integral with the axis R by means of hubs a1, a2 each comprising a disc situated outside the planes in which the arms G 'and G' 'rotate; a fixed, double cursor, which rubs on the discs a1 and a2, makes it possible to connect the terminal 2 to the arms G 'and G' '; arms G ', G' 'can make a full turn around the axis R.

The double G arm is integral with two hubs a3, a4 each comprising a disc; a fixed cursor, double rubs, at one of its ends, on the discs of the hubs, and, at the other of its ends, is connected to terminal 7; the arm G can thus also make a complete revolution around the axis R.

In Figure 10 the arms G ', G' ', G are shown in the position where they respectively connect the terminals 4 and 2, la and 2, 5 and 7. By rotation of the axis R the arms G', G '' and G can be brought into two other positions: a position where they connect terminals 3 and 2, 1a and 2, 6 and 7 respectively and a position where they respectively connect terminals 3 and 2, 4 and 2, 1b and 7.

The transformers T1 and T2 and the line H associated with the switch Kbd in FIG. 10 are respectively connected between the terminals 4 and 5, 3 and 6, 1a and 1b.

The rotary antenna which has just been described therefore makes it possible to emit in several configurations of half-curtains and to choose, from among the four right or left half-curtains, the one which will be connected to the emitter E1 represented in FIG. 4 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 frequencies or to the right half-curtain low frequencies.

• 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 fréquences hautes, l'émetteur E2 étant alors relié au demi-rideau gauche fréquences basses ou fréquences hautes 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 une même direction azimutale, l'émetteur E1 émettant sur une fréquence F1 et étant relié, par exemple, au demi-rideau gauche fréquences basses, l'émetteur E2 étant alors relié au demi-rideau droit fréquences basses 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),
• 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.
• une même émission sur un rideau complet de l'antenne rotative, c'est-à-dire sur tout le rideau fréquences hautes ou tout le rideau fréquences basses, l'émetteur E1 alimentant par exemple le demi-rideau gauche fréquences basses et l'émetteur E2 le demi-rideau droit fréquences basses ; 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 4 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 emissions 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 frequencies, the transmitter E2 being then connected to the half-curtain left low frequencies or high frequencies 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 the same azimuthal direction, the transmitter E1 transmitting on a frequency F1 and being connected, for example, to the left half-curtain of low frequencies, the transmitter E2 being then connected to the right half-curtain of low frequencies and transmitting on a frequency F2 with, again, a frequency difference sufficient 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.
• the same emission on a complete curtain of the rotary antenna, that is to say on all the curtain high frequencies or all the curtain low frequencies, the transmitter E1 supplying for example the left half-curtain low frequencies and the transmitter E2 the right half-curtain low frequencies; 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. 4 which, conventionally regulates the respective phases of the transmitters E1, E2 so as to render zero phase difference between the signals it measures 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 can in particular 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, thus in the embodiment described the switches Khg, Kbg, Khd, Kbd can be deleted.

It is also possible to simultaneously transmit the entire high frequency curtain in one direction and the entire low frequency curtain in the opposite direction, for example by connecting to each of the two outputs of the joint J not only a "balun-switches" assembly as in Figure 4, but two sets: one for each vertical half of the antenna.

Claims (5)

Broadcasting assembly consisting of 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, n, with n positive integer less than 3, parallel vertical curtains of wire dipoles (d1-d16, D1-D16), each associated with a reflective curtain (N, N ') and pairs of horizontal beams (B1-B2, B3-B4, b1-b2) fixed to the mast at different levels, the lower pair (B3, B4) constituting a platform on either side of the mast, in which supply means, part of the path of which passes through the joint and the mast, are provided for supplying the dipoles of the dipole curtains, characterized in that the transmission means comprise two transmitters (E1, E2), in that the supply means comprise two separate channels (G1, J, G4, Sg, Qg, Khg, Kbg - G2, J, G3, Sd, Qd, Khd, Kbd) which start from the two transmitters respectively, remon tent by the joint and inside the bottom of the mast to the platform where they separate, each following one of the beams of the platform on which they are fixed, then go up vertically from the dipoles to supply respectively at least some of the dipoles of two separate vertical portions of the n dipole curtains, in that these separate paths each include a balun (Sg, Sd) in the part of their path where they follow the platform and in this that the joint (J) is a bi-coaxial joint. Broadcasting assembly according to claim 1, in which n is equal to 2, characterized in that the channels include a band switch (Qd, Qg) in order to allow to choose, for each channel, if the distinct vertical portion will belong to the either of the two dipole curtains. Broadcasting assembly according to one of the preceding claims, characterized in that the channels include connection means (Khg, Kbg, Khd, Kbd), associated with impedance transformers, to allow, in the separate vertical portions where the end the two channels, 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 measure 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 wire dipoles and comprising a metal case 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 for ensuring 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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