US 2757370 A
Description (OCR text may contain errors)
y 31, 1956 M. w. SCHELDORF 2,757,370
TELEVISION TRANSMITTING ANTENNAS Filed July 27, 1951 2 Sheets-Sheet 1 y 31, 1956 M. w. SCHELDORF 2,757,370
TELEVISION TRANSMITTING ANTENNAS 2 Sheets-Sheet 2 Filed July 27, 1951 f j, 8 w S w w? W 2 M d w m Z 3 4w J d Z W w 9 2 2 MW a Q h [l F L J? A? W r J q x JP [III- M n y g g w United States Patent 9 2,757,370 TELEVISION TRANSMITTING ANTENNAS Marvel W. Scheldorf, Polos Heights, 11]., assignor to Andrew Corporation, a corporation of Illinois Application July 27, 1951, Serial No. 238,915 4 Claims. (Cl. 343-896) The present invention relates to antennas, and more particularly to an improved economical television transmitting antenna of the type having a plurality of bays.
In the television transmitting art, it has become customary to employ antenna structures utilizing a plurality of bays. Generally, such structures are comparatively complicated and extensive. It therefore is apparent that it would be desirable to provide an improved antenna structure which is more economical, and which requires a minimum of line balancing and tuning apparatus. In accordance with the present invention, certain advantages are obtained in economy, and also in simplification of tuning or impedance matching apparatus.
It is therefore an object of the present invention to provide an improved antenna having a single ended feed.
A further object of the present invention is to provide an improved antenna, having improved band width characteristics.
Still another object of the present invention is to provide an improved antenna having a radiating element, which has a shunt resonant circuit in parallel with the feed terminal.
A further object of the present invention is to provide a new and improved antenna having conical radiating elements, arranged in a horizontal frame, at an angle less than 90 therebetween.
Still another object of the invention is to provide an improved antenna arrangement, wherein the radiating elements are supported without insulation.
A still further object of the invention is to provide an improved antenna having a plurality of bays of radiating elements interconnected by shunt and series circuits.
Still another object of the invention is to provide an arrangement in antennas having a plurality of bays of radiating elements connected by means to the coaxial feed line, to obviate the use of matching devices.
Other and further objects of the present invention subsequently will become apparent by reference to the. following description taken in conjunction with the accompanying drawings, wherein:
Figure 1 is a perspective view of a multi-bay antenna constructed in accordance with the principles of the present invention;
Figure 2 is a partial top view of an antenna structure constructed in accordance with the principles of the present invention, when supported from an l-l-beam;
Figure 3 is a diagrammatic representation of the'circuits and components interconnecting a plurality of bays of radiating elements with a transmission feed line;
Figure 4 is a partial view showing certain details of the components used in Figure 3; and
Figure 5 is a diagrammatic representation of the manner of interconnecting a greater number of bays than those shown in Figure 3, with a transmission feed line.
Referring to Figure 1, there is shown one section of an antenna support, or tower structure, which has a triangular horizontal cross section. Preferably this is formed by the use of three vertical pipes 11 terminated at each of their ends by suitable interconnecting plates 12 having holes therein for receiving suitable bolts. The plurality of the sections therefore may be connected together in accordance with the requirements of height of the antenna and spacing between antenna bays. The three vertical pipes 11 are interconnected by transverse and angularly arranged struts or spacing members 13, secured thereto in a suitable manner such as by welding.
In Figure 1, the antenna tower supports two bays of radiating elements. Between two of the vertical pipes 11 there are supported, at suitable intervals, transversely arranged channel members 14. Each of the channel members 14 carries a bracket 15 provided with a plurality of angularly arranged sockets 16. The angularly arranged sockets 16 preferably are at acute angles to each other, or at least slightly less than therebetween Each of the sockets 16 supports a pipe or rod 17 which extends outwardly and is terminated by a clamp 18. Each rod 17 carries a radiating element which generally has a configuration corresponding to a frusto-conical portion 19 joined to a generally hemispherical portion 21. For a minimum of weight and wind-resistance, these hemispherical and frusto-conical portions are defined by a structure formed of a plurality of rods or tubes along the outer surfaces of these geometrical configurations.
In the arrangement illustrated in Figure 1 it has been found adequate to define the sides of the frusto-conical portion by six tubes or rods 22 having their ends connected to ring members 23 and 24. An equal number of rods 25 define the hemispherical portion and are' connected between the ring 24 and the cap 18 of the rod 17. The structure thus defined by the rods 22 and 25 and the rings 23 and 24 is supported from the cap 18 and the ring 26 having radially extending spokes 27 which engage the members 22 at intermediate points.
From this it will be appreciated that the end ring 23'- which is the smaller ring of the frusto-conical portion port member it is possible to space the input terminal ring from the ground point .and provide insulation byv air alone, thus achieving a minimum capacity.
Thus, .in Figure 1 a two-bay antenna has been illustrated, wherein the upper bayconsists of two cage-like elements 28 and 29 which constitute the radiating elements, each supported by axially arranged support rods 17 arranged in horizontal planes with an acute angle therebetween. The other bay consists of the cage members 31 and 32 having similar geometrical configurations and likewise supported by axially arranged rods 17 in ahorizontal plane, and an acute angle therebetween.
While the arrangement illustrated in Figure 1 shows an antenna supporting structure of fabricated structural steel composed of tube material, the radiating elements can be supported from an H-beam, as seen by the top view of Figure 2. It will be noted that the H-beam 33 is provided with suitable support members 34 and 35 on opposite sides thereof for the axial support 17 for the radiating elements 28 and 29. For the purpose of illustrating how the radiated elements are supported on a different support structure, these members have been given reference characters corresponding to those shown for similar elements in Figure l.
A suitable transmission line not shown in Figure 2 is connected to a balun 36 which interconnects the line with a plurality of line sections 37 and 38. The inner conductors of the line sections 37 and 38 are each pro vided with terminals connected by a plurality of conductive straps to the ring 23. One strap 39 is connected to the top of the ring 23 and anothrs'trap' 41 is c'orineared to the bottom of the ring 23. The arran ement shown in Figure 2 also illustrates the manner in which the radiating elements of Figure 1' are connected to a suitable transmission feed tine.
A diagrammatic representation of these circuits and co'rtipenents interconnecting a plurality of days or radiatiri'g elements with a tran's'missio'n feed line is shownin Figure 3 From this figure it is noted that the balun 36 is connected to' a transmission reed linen-3'. rue balun 36 is connected to the line sections 37 and 38 which respeetivery are connected to the radiatingelcmerits 2'8 and 29. Similar line sections 44 and 45 are connectedrespectively to the radiating elements 32 and 31. A series connection 46 extends between the outer conductor of the transmission feed line 43 and the inner conductor of the line sections 37 and 45. Another series connection 47 extends between the balun 36 and the inner conductor of the line sections 38 and 44. Thus it will be noted that the connections 46 and 47 extend to shunt connections 48 and 49 respectively. Suitable capa'citors 51 and 52 are provided within the balun 36 between the outer conductor thereof and the inner conductor portion, to maintain a matched condition through the junctions.
Further details of the construction of the arrangement shown in Figure 1 may be obtained by examining Figure 4. Herein it will be noticed that the coaxial feed line 43 has an inner conductor 53 and an outer conductor 54; The outer conductor 54 extends up into the balun 36 so as to be concentric with the outer conductor 55 thereof. The inner conductor 53 of the line 43 is connected to a coaxial inner conductor 56 in the top half of the balun, where it is of a diameter substan-, tially equal to the outer diameter of the outer conductor of the transmission line 43. The outer conductor 54 of the transmission line 43 is maintained in coaxial relation to the outer conductor 55 of the balun 36 by a plurality of plates 58 and 59. The one plate 58 is at the end of the Outer conductor 55 and the balun 36 and the other plate 59 is placed a short distance inwardly. A similar arrangement is provided at the other end of the balun 36 where two plates 61 and 62 are provided, one being at the end to hold the conductor 56 in coaxial relation, and the other plate 6?. being placed inwardly a short disiance.
The various line sections 37, 38, 44 and 45 are similar. Line section 37, for example, is composed of a coaxial conductor, hai'ing an outer conductor 63 and. an inner conductor 64. A portion of the space between the inner conductor 64 and the outei-conductor 63 is filled with a plurality of basic beads 65 to provide an impedance matching section. Just above the impedance matching section formed by the beads 65, the inner conductor 64 is' connected to a smaller coaxial conductor 66 which extends through the end seal insulator 67. The inner conductor 66 therefore is connected to the conductive strap 41 leading to the radiating element 28. From the foreoing it will lie appreciated that between the radiating elements and the transmission line there has been providcd a symmetrical balun with two shunt and two series circuits; thereby avoiding the necessity of matching at the interconnections.
In order to overcome certain reactive characteristics of a simple antenna of this type which is to be operated over a broad band an electrical correction must be introduced. This has been accomplished in the present instance by the use of a single half-wave line.- The connection between the radiating elements and the balun includes this line section.
While the principles of the present invention have been illustrated by the arrangement shownin Figures 3 and 4 for a two-bay antenna, the arrangement shown in Figure" 5' illustrates how an 8=bay antenna is intercom nected with a transmission feed line by a symmetrical balun. Thus, in Figure 5 there is represented a feed transmission line 71 connected to a balun 72. A transmission line section 73 extends from the balun to the first two bays, represented by the rectangle 74. Another transmission line section 75 extends to' the bays 3 and 4, represented by the rectangle 76. Similarly another transmission line 77 extends to the rectangle 78 which represents bays 5 and 6. Still another transmission line 79 extends to the rectangle 81, representingbays 7 and 8. It is believed that this will indicate to those skilled in the art that the principles of the present invention are readily applicable to antenna arrangements having one or more bays. I
While for the purpose of illustrating and describing the present invention, certain specific embodiments have been shown, it is to be understood that the invention is not to be limited thereby since such other embodiments are contemplated as may be commensurate with the spirit and scope of the invention as set forth in the accornp anying claims.
1. An antenna radiating element comprising a metal cage having a frusto conical configuration terminating at its largestdiar'neter in a hemispherical end, said element having an axial support connected only to said hemispherical end and to an intermediate part of said frusto conical portion, a plurality of radially arranged rods interconnecting said intermediate part and said support.
2. A very high frequency antenna radiating element having a generally frusto conical configuration terminating at its largest diameter in a generally hemispherical end, said element having an unins'ulated axial support rod connected only to said hemispherical end and to an intermediate partof said frusto conical portion, the smaller end of said 'frusto conical portion being an unsupported ring arranged to be connected to a source of radiant energy.
3. A very high frequency antenna radiating element having a generally frusto conical configuration terminating at its largest diameter in a generally hemispherical end, said element having an axial support rod connected only to said hemispherical end and to an intermediate part of said frusto conical portion, a plurality of radially arranged rods interconnecting said intermediate part and said support rod, the smaller end of said frusto conical portion being an unsupported ring and comprising a shunt resonant circuit which is off resonance relative to the frequency to be radiated.
4. A very high frequency antenna radiating element having a frusto conical configuration terminating at its largest end in a hemispherical member, a conductive vertical support for said element, said element having an uninsulated conductive metal axial support mounted perpendicular to and conductively on said vertical support, said axial support being connected only to said hemispherical member and to an intermediate part of said frusto conical portion.
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