US2167709A

US2167709A - Wireless aerial system

Info

Publication number: US2167709A
Application number: US130880A
Authority: US
Inventors: Cork Edward Cecil; Pawsey Joseph Lade
Original assignee: EMI Ltd
Current assignee: EMI Ltd; Electrical and Musical Industries Ltd
Priority date: 1936-03-17
Filing date: 1937-03-15
Publication date: 1939-08-01
Anticipated expiration: 1956-08-01
Also published as: GB475348A

Description

1939. E. c. CORK ET AL I 2,167,709

WIRELESS AERIAL SYSTEM iled March 15, 1937 IN VE N TORS EDWA ,QD CECIL C ORK JOSEPH LA DE P4 WSE Y A TTORNE Y Patented Aug. 1, 1939 I UNITED STATES PATENT OFFICE WIRELESS AERIAL SYSTEM Edward Cecil Cork, Ealing, London, and Joseph Lade Pawsey, Hillingdon, England, assignors, to Electric & Musical Industries Limited, Middlesex, England, a company of Great Britain Application March 15, 1937., Serial No. 130,880 In Great Britain March 1'7, 1936 5 Claims. (Cl. 250-33) The present invention relates to wireless aerial sheath of said feeder, while the other is consystems and more particularly to dipole aerials nected to the end of said auxiliary conductor. for operation at a relatively short wavelength. Ihe auxiliary conductor used in systems operat- In the design of a short wave aerial for haning in accordance with the invention may op- 5 dling a carrier wave and wide side bands such as erate in the manner set forth in the above men- 5 are required for television purposes, it is necestioned patent to W. S. Percival et al. sary to reduce the variation of reactance with In order that the invention may be more clearfrequency asmuch as possible. By using elely understood and readily carried into effect, two merits consisting of cylinders of large diameter methods of connecting a dipole aerial to a feeder or wide strips, the variation of reactance can be in accordance with the invention will now be 10 substantially reduced. In many cases, and pardescribed by way of example with reference to ticularly in cases where an auxiliary conductor of the accompanying drawing in which,

the type described in the specification of United Figure 1 shows diagrammatically in perspective States patent to W. S. Percival, et al., il -2,127,088, a dipole aerial and concentric feeder connected granted August 16, 1938, is associated with the in accordance with the invention, and 15 aerial end of a concentric feeder, a large amount Figures 2 and 3 show an alternative form of of reactance may be introduced in the connecconstruction. tions between the aerial elements and the feeder. Referring to Figure 1 of the drawing, a dipole This reactance may be considerably in excess of aerial comprises two hollow cylindrical members that of the aerial elements, in which case the l, 2 each provided at one end with a frusto- 20 frequency characteristic of the aerial will be 841- conical portion 3, 4. The diameter of the smaller versely afiected. end of each frusto-conical portion is about one It is an object of the present invention to prothird the diameter of the larger end and the vervide a new or improved arrangement for contical semi-angle of the cone is about 55. The necting a dipole aerial to a concentric feeder. larger ends of the frusto-conical portions have 25 QQQ t0 the s n i vent in. an i l the same diameter as, and are attached to, the system including a dipole aerial, a feeder and an cylindrical members. The two members I, 2 are auxiliary Conductor which SBTVBS 0 prevent the shown arranged one above the other, the frustoflow of Current at t frequency 130 e trans conical ends being adjacent one another and mitted r r eiv al ne h h h f h f r. separated from one another by a distance slightly 30 he ia Of the d e n s be n large greater than the diameter of the sheath of a n Orderto reduce variations in reactance of the concentric feeder 5 which is to be connected to serial With Variation in q y, a t n e the aerial. The feeder 5 extends in a straight troduced due to h i ns e w n h line for only a short distance from the end A ip e e ents and the feeder or the auxiliary connected to the dipole element l and it is bent 35 Conductor or both. is reduced by disposing the at the point B through a right angle in a horip ends of the feeder a auxiliary conductor zontal plane. Two further right angle bends are so that the connection of the central conductor of made t t i t 0 and D, the portion DH the feeder to the auxiliary conductor is as short being of indefinite length depending upon the as poss b e consistent with maintenance o d position of the transmitter. The points A, B, o, 40 quate insulation between h n of the 21mm D and H in the feeder all lie in a horizontal plane. iary conductor and Sheath- The dipole elements The distance AB is equal to the distance CD and may be cylindrical and in such a case their adthe length ABCD is arranged to be approximately jacent ends are formed as truncated cones equal to one quarter of the operating wavelength. nected to the opposed ends of the sheath and An auxiliary conductor 5 which also has a 45 auxiliar conductor. The ends of the feeder and auxiliarg conductor connected to the dipole eleiength r g y g ments may be chamfered in order that the dipole mg Wavelengt an 15 2 e i i e 1 m h elements may be disposed substantially coaxially. as the Sheath 9 t e feeder 1S hroug In a modified construction according to the ina nght'angle at pomts E and F and 15 connected vention, the adjacent ends of the dipole elements one end to the Sheath of the feeder at It are each connected to conducting surfaces, the arranged t Q= nd that width of which is substantially the same as the F =B u E d F be a the corners width of the dipole elements, one of said con- 01? a rectangle. The central conductor 1 of the ducting surfaces being connected to the end of the feeder projects beyond the end of the sheath and 55 is connected to the end of the auxiliary conductor B.

The spacing between the end G of the auxiliary conductor and the end A of the sheath of the feeder, is made as small as possible in order to keep the reactance of the connections to the members of the aerial as small as po'ssible,but must be sufficiently great to prevent sparking.

In one particular case the variation of aerial reactance with a certain change of frequency was 5 ohms due to the reactance of the aerial itself, and the increase when connected to the feeder due to the reactance of the necessary connections was found to be small compared with 5 ohms. It will be seen that a system of this type is symmetrical about the vertical plane through H, D and A and also about the plane of the feeder.

In a modification of the arrangement described with reference to Fig. 1 of the drawings, the feeder is bent at B but, instead of being bent at C and D, extends away from the aerial in a straight line BCH. The auxiliary conductor is bent as before at E and F and extends to and is connected to the sheath of the feeder at C. The lengths ABC and GFEC require to be slightly different from the value of these lengths in the previously described arrangement.

The form of connection shown in Figure 2 differs from that shown in Figure 1 in that the dipole elements are enabled to be arranged coaxially one above the other by chamfering the ends of the feeder and auxiliary conductor respectively. In other respects the details of Figure 2 are as shown in Figure 1. It will be seen that the construction shown in Figure 2 permits the ends of the feeder and auxiliary conductor to be brought close together, thereby keeping to a low value any reactance introduced by the connection between the central conductor of the feeder and the auxiliary conductor.

Referring to Figure 3 of the drawing, the connection between a concentric feeder provided with an auxiliary conductor and a dipole aerial is shown effected by means of a length of open line. The aerial comprises two cylindrical members 2 mounted one above the other and coaxially with one another, their adjacent ends being close together and each having a wide copper strip 8, 9 attached thereto. The strips may have a width equal to the diameter of the cylinders, for example, one or two feet. The strips extend, parallel with one another, horizontally away from the aerial and have their other ends connected respectively to the sheath of the feeder 5 and to the end of the auxiliary conductor 6 to which the central conductor 1 is also connected.

The auxiliary conductor 6 is of the same external dimension as the sheath of the feeder and has a length approximately equal to one quarter of the operating wavelength. It is disposed substantially parallel to the feeder and the end not connected to the dipole element 2 is connected to the sheath of the feeder.

The two strips form a line of low characteristic impedance between the feeder and the aerial. The distance between the strips is preferably just suflicient to prevent sparking and may be of the order of 1 inch.

Arrangements according to the present invention are of particular use as transmitting aerials but they may also be used for reception. It will be understood that although particular shapes of dipole elements have been described, any desired practical shape presenting a large surface may be used.

We claim:

1. An aerial system comprising a dipole aerial the elements of which have a large surface area, a feeder for said aerial including a conductor and a conducting sheath surrounding said conductor, an auxiliary conductor associated with said sheath for preventing currents of the operating frequency from flowing over the outer surface of said sheath, said auxiliary conductor being arranged for the greatest portion of its length parallel to said sheath and having a length substantially an odd integral multiple of a quarter of the Wave length at which the system is arranged to operate, one end of said auxiliary conductor being connected to said first mentioned conductor and positioned closely adjacent the end of said sheath and opposed thereto, the other end being directly connected to the outer surface of said sheath; the adjoining ends of said dipole elements being connected to the opposed ends of said sheath and said auxiliary conductor.

2. An aerial system comprising a dipole aerial the elements of which comprise cylinders of large diameter to reduce variations in reactance of the aerial with variation in frequency, a feeder for said aerial including a conductor and a 'condut ing sheath surrounding said conductor, an auxiliary conductor associated with said sheath for preventing currents of the operating frequency from flowing over the outer surface of said sheath, said auxiliary conductor being arranged for the greatest portion of its length parallel to said sheath and having a length substantially an odd integral multiple of a quarter of the wave length at which the system is arranged to operate, one end of said auxiliary conductor being directly connected to the outer surface of said sheath, the other end of said auxiliary conductor being positioned closely adjacent the end of said sheath and opposed thereto, said end being connected to said first mentioned conductor, the adjacent ends of said dipole elements being connected to opposed ends of said sheath and said auxiliary conductor,

said adjacent ends being formed as truncated cones whereby the reactance introduced due to the connections is reduced.

3. An aerial system comprising a dipole aerial the elements of which comprise cylinders of large diameter to reduce variations in reactance of the aerial with variation in frequency, each of said cylinders having a length equal to one-quarter of the length of the operating wave, a feeder for said aerial including a conductor and a conducting auxiliary conductor being directly connected to the outer surface of said sheath, the other end of said auxiliary conductor being positioned adjacent the end of said sheath and connected to said first mentioned conductor and means for coupling said feeder to the elements of said dipole comprising a pair of closely spaced parallel conducting plates, the widths of which are substantially the same as the width of the dipole elements, one of said plates being connected to the end of said sheath and the other to the end of said auxiliary conductor said pair of plates forming a low impedance connecting line between said feeder and said aerial.

4. An aerial system comprising a half wave dipole aerial the elements of which have a large surface area, a feeder for said aerial including a conductor and a conducting sheath surrounding said conductor, an auxiliary conductor associated with said sheath for preventing currents of the operating frequency from flowing over the outer surface of said sheath, said auxiliary conductor being arranged for the greatest portion of its length parallel to said sheath and having a length substantially an odd integral multiple of a quarter of the wave length at which the system is arranged to operate, one end of said auxiliary conductor being connected to said first mentioned conductor and positioned closely adjacent the end of said sheath and in opposed relationship thereto, the other end being directly connected to the outer surface of said sheath, the adjoining ends of said dipole elements being connected to the opposed ends of said sheath and said auxiliary conductor, the opposed ends of said sheath and auxiliary conductor being chamfered whereby said dipole aerial elements may be coaxially arranged.

5. An aerial system comprising a half wave dipole aerial the elements of which comprise cylinders of large diameter to reduce variations in reactance of the aerial with variation in frequency, a feeder for said aerial including a conductor and a conducting sheath surrounding said conductor, an auxiliary conductor associated with said sheath for preventing currents of the operating frequency from flowing over the outer surface of said sheath, said auxiliary conductor being arranged for the greatest portion of its length parallel to said sheath and having a length substantially an odd integral multiple of a quarter of the wave length at which the system is arranged to operate, one end of said auxiliary conductor being directly connected to the outer surface of said sheath, the other end of said auxiliary conductor being positioned closely adjacent the end of said sheath and opposed thereto, said end being connected to said first mentioned conductor, the adjacent ends of said dipole elements being connected to opposed ends of said sheath and said auxiliary conductor, said adjacent ends being formed as truncated cones whereby the reactance introduced due to the connections is reduced, the opposed ends of said sheath and auxiliary conductor being chamfered whereby said dipole aerial elements may be coaxially arranged.

EDWARD CECIL CORK. JOSEPH LADE PAWSEY.