US2617935A - Wireless aerial - Google Patents

Description

Nov. 11, 1952 Filed April 4, 1950 N. M. BE ST WIRELESS AERIAL 2' SHEE'ISSHEET 1' 62M ELM,

in a junction box Patented Nov. 11, 1952 z.

UN I T E AT T a v f ac maa I a f WIR EI IESS AERIALL a H Norman Maxwell Best, London, England, assignor to Antiference Limited, London, England, a?

British company Application April 4, 1950, Serial No. 153,905

. In Great Britain May 6,1949 'n 1 1 The present invention relates to an i mpr oved aerial such as may be used, for example, for the transmission or reception of wirel-ess waves, and

although not' limited exclusively thereto, partici larly useful for the reception of television signals.

A known form of aerial at present commonly horizontally plane polarised waves, the dipole comprises two similar, -hori zontal,, oolinear, spaced, electrically conductive rod-s having their adjacent ends gripped in an insulating junction box whichis held at one endyof a hollow horizontal supporting arm. The parasitic element, for

example a reflector, may be a single rod or tube or may comprise a pair of similar, horizontal,

, colinear, electrically conductive rods having their adjacentends connected together and gripped I h held at the other end of the supportin n H-formation all in the same horiea ive ln an A pair of insulated lea-dasuch as a concentric or twin cable, run from the adjacent ends of the dipole rods to the set.

Such a known aerial is illustrated diagrammatically and in plane view in the accompanying Figure 1, the dipolerods (12) being shown at 20,

" vide an-aerial which although of receptivity comparable with; or better than, known aerial-s, yet

i cheaper to manufacture. Another object is to jprovide an aerial of higher selectivity than those now'c-ommonly'in'use for the receptionof televisionsi'gnals, without increasing the cost of manufacture or decreasing the signal strength receivable by the aerial.

Preferred forms of the invention will now be described with reference to the accompanying drawing, in which 9* Claims. (01. 250-3351),

The dipole, reflector and supporting arm are arranged in Figure 1 shows the-known form of laerialIdescribedabove, 2

Fi-gure 2 is its polar diagram in a horizontal plane, .i 1 Figure 3 is a plan of one form of aerial,; constructed and arranged to operate in accordance with this invention, pl I k Figure 4 is the polardiagram given jlpy the e lcf Figure N H ,5 Figures 5 and dare respectively a plan and elevatio-n, on a more open scale, of the aerial'shown ri a U. a

Figure '7 is a perspective view, on a yet more open scale, of the junction box shown in Figures end6,an Figures -8 to 11 inclusive are plan views of various aerials, all of h which are modifications of the aerial of Figure 3, and all lying within the scope of the present invention. f a

The aerialillustratedin Figures 3, 5, 6 and 7 comprises a dipole D and parasitic member P in the form of two dipole rods 25, 26 and two parasitic rods 21, 28, arranged to extend radially in a horizontal plane, from an approximately common centre at equi-angular spacings of The four rods are gripped at their inner ends in an insulating junction box 29 formed withfour sockets forthis purpose.- I

The junction box is mounted in a bent hollow bracket 30 which is secured to a hollow-mast 3| nected to rod 26-via terminal 33.;

The parasitic rods 21 and Marc connected together by a yoke 36. 4

Twin cables may be used in place of the concentric ones shown; w J

When such an aerial is used to receive wireless waves polarised in a horizontal :plane, the rods are mounted so asto lie in a horizontal plane and the horizontal polar diagram givenbylone such aerial is shown in Figure 4. It will beseen that "the curve is of cardiac shape rough-1y similar-to that of Figure 2 but displaced by with respect thereto. Maximum sensitivity is thu's'given when the parasitic rods point towards the source and not, as in the case of the known H-aerlal, when the dipole rods point towards the source.

The polar diagram of Figure 4 applies when of each dipole rod may be about 5' 9" and of, each director rod about 5 3". The front to" back sensitivity ratio is thenabout 12/1.

With dipole rods 5' 3" and parasitic rods 5' 9" the latter act as a reflector-andthe-polar;-

diagram is reversed. The front'to back'ratio is with this arrangement about 1.5/1.

With an aerial of this kind onlyronejunction, box is required and no supporting cr.oss=arm..is;-

necessary.

Since its polar diagram is non-circular, l. e., it. has selective sensitivity, it is preferably arranged" with the directionofmaximumsensitivity pointing towards the source; if thereis no appreciable interference-to be taken intoaccount.

I If,- however, there --is a-source or sources of in-' "terference to be taken into consideration,-then a compromise position is adopted with the source of interferenceas near-aspossible on th'e direction of minimum signal strength" and the source to-bereceived on the directionof maximum sig- -nal'- strength, but as the relative strengths of the two sources afiect the final position-the latter,-- would usually lee-arrived. at by trial and I error.-

In Figure 8 is shown an aerial similar in all respects to that of Figures 3 to 7"except that the parasitic rods 38 and 39-are-connected to one of thedipole rods, namely, the-lower rodli).

The advantage or a-know-n-foldeddipolebr ofa-k-nown double v -shaped dipolemay be'applied" to'the novel aerial described above; with reference to Figures *3 to '7.

Thus; asshown in Figure 9, the parasiticrods and 2 6 of Figure-3. have 2 been replaced by--a'-- pair -oi'ifolded, but inclined, rods-43 and 444 In-the arrangement of Figure 10'both'th'e dipole rods, 45 and 46, and'the parasitic rods, 4 and, are folded.

InFig'ure ll the dipole rods 25 and-'26: offFigure 3 are each replaced by a pair oi-V-shaped rods '49 or '50- respectively. If f desired,- both the dlpole andparasitic-rods may each be replaced The modifications described with: reference =-to Figures "'8 to 11 as a-zgeneral rule: do -not giveas high sensitivity asthe:v arrangement of Figures 3.:to 7; but: insome respects have. better: polar diagrams, so that-theymay :be used: with advantagein special circumstances:

The word rod as used herein-is intended: to cover tube-likeras well as rod-dike members Wide variations of the propertiessofiall such aerials cantbe maderby varying-:thelengths of the rods. and-ithei angles: betweenithem- ,and.1byr

placingthe: rods out 10f i a; common plane- Good-reception can :be robtainedlby .placingethe 1 rodssin ,.a, common plane: parallel to.:;th'e: plane ofzpolarisationzrof .theavaves to: be received, and at. 9Ilangular intervals about. the common centre;

It has been found, however, that the angle a (Figure 3) between the dipole rods or the angle a between the parasitic rods, may be between 60 and without seriously affecting reception, and that the rods can be placed out of the plane of polarisation without serious diminution of ithezsiginalkstrength: i

What I'claim is:

1. An aerial comprising four rods extending radially from a common centre, two being electrically; insulated from each other at their inner, ends, and the other two being in electric connectionr atitheir inner ends.

2...An1.a.erial comprising four rods supported so that they lie in a common plane and extend radially-:fromacommon centre, two of the rods being electrically insulated from each other and theother. two being electrically connected together.

3. An aerial comprisinga .pair of electrically insulated dipole' rods" inclined obliquely one to the other and apair of electrically connected parasitic: rods also obliquely; inclined" one to the other;-;thefO'LlIjIOdS being supporte'd' so' that they-liein a common plane-and -extendradially from a common centre.

4': aerial'asclaimed in claim- 1', wherein theangle between" the electrically connected-rods lies between fio and "120 5; Anaerial-- as claimed-"in claim 1; wherein the angle between the electrically insulated rods lies between 60" and 120.

6i-An aerial as claimed" in claim 1; wherein the four rods are equiang-ularlyspaced in-a cornmon plane;

7 An aerial asclai-med inclaim*=3 wherein the parasitic rods areconnected electrically to 'one of the dipole -rods.

8 A' wireless aerial comprising-four electricallyconductive elements'mounted so that they extend-radially away from acommon center in a common flatplane,- two adjacent ones being electrically insulated from eachotherand-forming a dipole and the other twobeing "electrically connected andform-ing parasitic elements.-

9. A wireless l aerial" comprising four electrically conductive elements held at theirinner ends-ina commonsupport so that they extend radially away from thesupport in a commonfiat plane, angles between any two adjacent elements being between-"60 'and 120} one pair of 'adjacent elements b'eing electrically:insulatedfrom eachother 'so' as to constituteabent '-'dipo1"' and the-other= pair: being electrically connected together so as to form a- -pa'rasiticelen' entn- NORMAN- MZAXWELL BEST.

REFERENCES CITED? I The followingreferences are of -record in" the file iof ithispatentg" I uNIT'EUs'rATEs-PATENTsT Number. I Name. Date-= 1,988,434- Bohnet .al. Jan. 22,1935 2204175 Carter -Junell, 1940 21368286 Carlson .Jan. 30,-.1945 2;4-19";55'2 1 'Himmel-"etar Apr. 29; .1947

7 452,073 I Schivlyet. al. ..Oct; 26, 1948

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