US2489720A - Antenna - Google Patents

Description

' Nov. 29, 1949 Filed Sept. 25, 1948 H. A. NEWELL ET AL ANTENNA 4 She'ets-Sheet l INVENTORS. HAROLD A.NEWELL. ALBERT W. KRAMER.

I ATTK Filed Sept; 23, 1948 Nov. 29, 1949 H. A. NEWELL EI'AL 2,439,720

ANTENNA 4 Sheets-Sheet 2 IA. 18 H 39 4'0 4 INVENTORS. HAROLDANEWELL. If BY ALBERT w. KRAMER.

Nov. 29, 1949 glw ET 2,489,720

pu'rfim m v 4 sheets-sheep 5 Filed Sept. 25, 1948 g ss INVENTORS. HAROLD A NE WELL.

BY ALBERT W KRAMER.

ATTY.

Nov. 29, 1949 i-LA. uswzu. arm.

ANTENNA Filed Sept. 23, 1948 48heeis-Sheet 4 I INVENTORS. HAROLD A. .NEWELL. BY ALBERT w. KRAMER.

ATT).

' purpose of minimizing andinterference r and, such antenna, when a parasitic: array, should be provided with means whereby the critical distance between dipole and reflector is readily and; 1 easily adjusted. Third, such Patented Nov. 29, 1949 ANTENNA Harold A. Nowell, Dillsbo Kramer, Cincinnati, 0 -Mamiiactur ing Corporation,

hi0, assignors to Avco 1nd and Albert W.

Cincinnati, Ohio,

a corporation oizDelaware. Application September 23,1948; SeriaI'N'o. "50,1598

5 Claims.

The present invention relates generally to antennas and specificallyto an-an'tenna suitable for use with V. H. F-., U. 'H. television and FM broadcast bandreceiverspand of the type wherein physical length is preferably adjustable to approximate a half-wavelength or an integral multiple of a half wavelengthof the R. F. signals "to be received. For purposes of illustration the embodiments of the invention herein disclosed are shown and described as horizontally polarized half -wave dipoles.

The electrical characteristics of a tuned ha'lfwave dipole, sometimes referred to as'a 'halfwave Hertz or half-wave doublet arewell known to those skilled in the art. The simple; half-wavelength antenna is the most Widelyused because it involves the least length of *w-ire 'or tubing that can be made toresonate at a given frequency. For locations wherethe received-signals are Weak or where noise and interference have a greater distorting eflec-t, more elaborate arrays, possessing greater gain and direeti'vity,

' are employed. Additional gain is achieved-and directivity increased by mounting "close toand parallel tothe antenna a parasitic element such;

as a tuned half-wave reii'ec-tor. Whenahighantenna input impedance is desired, the simple dipole may be replaced by-a folded =d='ipole,-consisting essentially of two parallel closely spaced half-Wave conductors connected together at the 3' ends and connected to a transmission l ineat the center. The simple dipole, the dipole with reflector and the folded dipole with reflectorarethe most popular types for televisiona ndreception, to improvements in such antennas.

The ever-increasing popularity of television and FM-reception has created a'need'for an-antenna particularly adapted to the needs of television installations and possessing one or mre of the desirable characteristics enumerated abelow.

First, such antenna should be capable of asy handling and adjustment, since its position must be carefully chosen, not only from the standpoint of signal strength but also for the. ghosts, double-images, from undesired reflections; Secan-tenna should be capable of ready directional orientation. Fourth, such antenna should be so arranged that. it can be very quickly 'set up without any requirement for expensive assembly labor. Fifth thesantenna.

The present invention specifically relates elements should be capable of ready conversion irom dipole-to folded dipole. Sixth, the antenna should'be cap'ablebf-pakaging, storage'and shipment, while in assembled'conditic'm, in a space small a'scompared tothe cubic footage of clearance required when'the'antenna is in operating position.

The general objects of the present invention are to provide an antenna structure which satisfies all or "the aforementioned requirements.

The primary object of "the invention is to pro- -v-i'de "an antenna which is so constructed and arranged-that it "can be shipped in a relatively =srnall=cartonbut readilyand easily installed "and adjusted to provide "optimum reception.

Another object of the "invention is to provide an antenna structureoomprisirrg a central upright support orve rtioal mast', apair of spa-oer arms, 'r-neans ierael-justably swingably mounting the spacer arms on the mast, whereby they may be moved between depending positions substantially'paralleltothe 'mast and operating positions angular Withresp'ect-tothe mas-t, a pair of dipole elements, a pair'of "refiectrelements, and means for adjustably swingabl y mounting individual ones of said pairsm': elements on the spacer arms Wherebysaiddipol'e and reflector elements may be moved-between positions substantially parallel "to the associated -s'pacer arms and operating positions angular' withrespect toth'e spacer arms.

A fu-rtherobj ect ofthe invention is to provide, in an antenna structure, the combinationof' a vertical support, aspacer tube, means for adjustably swingabl y mour-iting-the-spacer tube on the support whereby it may beturned between a depending position "substantially parallel to the support to an nperati ngposition angular with respect to the support, a pairot dipole elements,

and means :for ad j ustably "swingably mounting said dipole .elementson saidspacer tube, whereby said dipole elements -may be turned between a position substantially parallel to the spacertu-be and operative positions angular with respect to the spacer tub-e.

Itis: also an object ol' the invention to provide an antenna structure com-prising two spacer-elements ioldabl'e about a mast, dipole elements .foldable about 'the fire'e end of one spacer element, and parasitic elements foldab'l'e about" the tree end of the other spacer element, the direction of the folds of the dipole rods and parasitic elements being opposite to the direction of the fold of the: spacer elements, wherebythe total :length of the folded structure-is: determined sub- 1 stantially by the length of the mast and the in an antenna structure, means permitting rota-- tion of the spacer arms in a plane through longitudinal axes of the spacer arms for adjustably mounting the spacer arms to determine the spacing between dipole and reflector elements.

A further object of the invention is to provide,

in an antenna structure, means permitting rotation of the spacer rods about their own longitudinal axes for determining the angular relation-' ships between the dipole elements and the reflector elements.

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following description, to the claims appended hereto and to the accompanying drawings, in which there are illustrated preferred illustrative embodiments of antenna structures in accordance with the invention.

In the drawings: Fig. 1 is a top plan view of a preferred form of half-wave dipole with reflector in accordance with the invention; Fig. 2 is a front elevational view of the Fig. 1 embodiment; Fig. 3 is a right side elevational view of the Fig. 1 antenna, showing clearly the reflector elements; Figs. 4, 5, 6 and '7 are sectional views taken, respectively, on lines 4-4 of Fig. 2 and 5-5, 55, and 7-? of Fig. 1, looking in the direction of the arrows; Fig. 8 is a top plan view showing the dipole side of the Fig. l embodiment as converted to a folded dipole antenna. Fig. 9 is a front view of the folued dipole of Fig. 8; Fig. 10 is a sectional view taken on line Ill-H) of Fig. 8, looking in the direction of the arrows; Fig. 11 is a front elevational view showing a modified embodiment of the invention in the form of a simple dipole antenna; and Fig. 12 is a view, taken from the same point of observation as Fig. 2, showing a completely assembled half-wave dipole and reflector antenna structure in accordance with the invention, as it appears when packed and ready for shipment or storage. In certain views portions of the mast, spacer arms, dipole elements and reflector elements have been broken away, so that the inventive features may be more clearly illus trated and emphasized.

Referring now specifically to Figs. 1, 2, 3 and L 12 there is shown a complete dipole-and-reflector antenna structure in accordance with the invention. A central upright support or vertical metallic mast |5 is provided with a guy-wire clamp I6 and adapted to be held in position by a plurality of guy-wires l1, l8, l9 or the other suitable conventional expedient. The lower end of the mast is so mounted that the mast can be adjustably turned about its own longitudinal axis. Also, the mast can be adjusted to the vertical even when the foundation is not horizontal. Specifically, the antenna as a whole is supported by a base plate 28, having upturned sides 2|, 22 (Fig. 3)

which overlap the downwardly turned integral extensions 23, 24 of mounting clamp 25. Clamp 25 is of resilient metallic material and snugly embraces mast I5. Screw 25 and its complementary nut (not shown) are loosened rotatably to adjust mast I5. Each of bolts 27 and 23 passes laxed position shown in Fig. 12, in which position they are placed when the antenna is shipped (i. e. substantially parallel to the mast 5) to the 180 degree operating position shown in Fig. 2, or to any operating position wherein the side view (Fig. 2) simulates a V, whereby the spacing between dipole elements and reflector elements may be adjusted as required. In fact, the arrangement herein shown is so flexible that each spacer arm is mounted for adjustable rotation from the depending position shown in Fig. 12 to the opposite vertical position. This feature is provided by clamping-socket-shoulders 31, 38, which are adjustably swingable and are comprised in the means permitting rotation in a plane through the longitudinal aXes of the spacer rods to permit adjustment of the spacing between dipole and reflector.

The orientation of the spacer rods is also adjustable in azimuth so that the antenna may be adjusted for desired directivity characteristics. This feature is provided by clamping-sockethead 39.

Referring now specifically to Figs. 2, 3 and 4, the head comprises two complementary metallic members 45, 4| grooved interiorly to form a socket which receives in embrace the top end of mast 5. The members 45, 4| converge above the mast and terminate in integral extensions 42, 43, suitably apertured to receive a bolt 44. The sides of the members 45, 4| have flat contact portions 45, 43 (Fig. 4), apertured to receive a plurality of bolts such as 41, 48, each provided with a threaded nut 49, 55, 5|, 52 (Fig. 2). When nuts 49-52 are tightened down, the abutting flat inside surfaces of extensions 42, 43 and sides 43, 45 are in close tight contact and head 39 securely embraces mast l5 to prevent rotation of the head and the parts it carries. When nuts 49-52 are loosened, the head and spacer arms can 'be rotated to provide for orientation of the spacer arms in azimuth, whereby the antenna is adjusted for desired directivity characteristics.

The clamping shoulders 3'1 and 38 are alike, and it will be understood that the following description of shoulder 37 is equally applicable to shoulder 38.

As shown in Figs. 2 and 4, shoulder 31 comprises two main parts, a flat inner member or plate 53 and an outer member 54, bulged out to form an interior groove which embraces the inner end of spacer arm 3|. The side and inner end marginal portions 55, 55, and 5'! of the outer member have interior flat surfaces which fractionally abut the interior fiat surface of inner member 53. These marginal surfaces and inner member 53 are apertured to receive a plurality of bolts such as 58, 59, 60, which have cooperating nuts 6|, 52, 63 and 64. When nuts 6|54 are tightened down, the inner end of spacer arm 3| .is tightly compressed between members 53 and .the spacer arm 3| can be rotated about its own longitudinal axis for the purpose of adjusting the polarization of the dipole or determining the angle between the dipole and reflector elements. Similarly, spacer arm 32 is rotatably adjustable on shoulder 38.

As seen in Fig. 2, the inner and outer shoulder members 53, 54 have an overall ninety-degree arcuate shape and terminate inwardly in extended flat portions such as 51 to receive bolt 44. A washer 65 is interposed between member 54 and the head of bolt 44 and a spring lock washer 66 is interposed between member 53 and the extension 43 of head 39 (Fig. 4).

Shoulder 38 is arranged with its flat inner member on the side toward the inner member 53 of shoulder 31 and it provides a socket and clamp for spacer arm 32 (Fig. 2). A spring lock washer is provided between extension 42 and the inner member of shoulder 38.

Bolt 44 and nut 61 are loosened to permit the spacer arms to depend (Fig. 12) or to be set at an operating position (Fig. 2) at which the desired spacing between dipole and reflector elements is achieved. When the proper operating position of the spacer arms is attained, then bolt 44 and nut 61 are tightened to secure the spacer arms in position.

With the exception of the transmission line 80 and connecting links 95, 96 presently to be described spacer arm 3| and the dipole elements and mounting means it supports are the same as spacer arm 32 and the reflector elements supported by it. Therefore, for purposes of simplicity and brevity, the specific description will be confined to the dipole subassembly (left-hand Figs. 1 and 2) for the present.

The outer end of spacer arm 3| is flattened at 68 to provide an extension to which clampingbrackets 69, 18 are adjustably swingably secured. These clamping brackets are alike and further specific description will presently be confined to bracket 69. It comprises a pair of generally arcuate-sectional clamp members 12, having abutting side portions and end portions, the side portions being clamped together by a plurality of rivets 13, I4, 15 and 18 (Fig. 1). The interior of the brackets defines a tubular chamber tightly embracing an insulating sleeve 11, which in turn tightly embraces the dipole element 33, the latter being a conductive metallic tube having a concentric adjustable extension 91. As clearly shown in Fig. 1, brackets 89, 19 are ninety-degree-angle brackets and terminate in flattened ends (Fig. 2) adjacent the flattened extension 68 of spacer arm 3|.

Brackets and 69 are similar, bracket 19 having two members 18 and 19 corresponding to members 12 and II, respectively, of bracket 69. Members 18 and 12 are of lesser length than members H and 19 (Fig. 1), to permit individual connection of the two conductors of transmission line 89 to the inner ends of dipole elements 33, 34. Such connections are made in a conventional manner.

Extension 38 and the end portions of the mounting brackets 69, '10 are suitably apertured to receive a bolt 8|, provided with a nut 82 (Fig. 5) and suitable washers 83, 84. It will be seen that the structure illustrated in Fig. 5 provides means whereby the dipole elements 33, 34 are foldable about the free end of the spacer arm 3|, the direction of the fold (Fig. 12) being opposite to the direction of the fold of the spacer arms 3|, 32, whereby the total length of the folded structure is determined substantially by the length of the mast and the other dimensions are small relative to those of the structure in unfolded cond-l tion (Figs. 1, 2, 3). Referring to Fig. 1, element 33 folds clockwise and element 34 folds counterclockwise when nut 82 (Fig. 5 is loosened. Nut 82 is tightened to maintain the dipole elements in operating position. Suitable depressions on extension 68 and projections (not shown) are provided on adjacent surfaces of members 12, 98 and I8, 68 to prevent turning of the element 33 in a counterclockwise direction and element 34 in a clockwise direction, relative to each other, once they are in line.

Suitable insulating supports 85, 86, for suspending and spacing transmission line 89 from spacer arm 3|, are provided.

It will, of course, be understood that shoulder 38, arm 32 and the reflector elements may be removed, in which case the remaining parts may be used as a simple dipole.

Referring now specifically to Figs. 6 and 7, it will be seen that the mounting of the reflector elements 35, 36 on spacer arm 32 is the same as the mounting arrangement for the dipole elements, and consists of a flattened extension 81 on arm 32, a clamp bracket 88, a clamp bracket 89, a nut 92 and a bolt 9|, with suitable washers and depressions and projections on adjacent frictionally contacting surfaces to hold the reflector elements in the operating position shown in Fig. l.

Toprovide for adjustments of the lengths of the dipole and reflector elements each such element, such as reflector element 35 (Fig. 7), for example, comprises an outer main tube having an inner contacting concentric tubular extension 93, slidably axially adjustable in relation to the outer tube. A circular knurled adjusting compression nut 94 having tapered threads is screwed on to the split tapered threaded outer end of the main tube in such a way that the inner tube is compressed and securely held when the nut is tightened down but is free to slide when the nut is loosened. This compression nut arrangement for adjusting the length of dipoles and reflectors is conventional and need not be further described herein.

As shown in Figs. 5, 6 and '7 suitable conventional arrangements are made for connecting the transmission line conductors to the dipole elements and conductive links 95, 96 are provided for connecting the reflector elements 36, 35 to the brackets 88, 89 and effectively to each other. It will be seen that the above-described embodiment of Figs. l-'7, 12 has the following adjustments:

Three additional adjustments are provided. Spacer arms 3| and 32 can be maintained substantially colinear but turned in unison to positlons not at right angles to the mast, as indi' cated by the dashed lines in Fig. 2. Dipole elements 33, 34 can be likewise adjusted so that they are colinear but are not at right angles to spacer arm 35. Similarly, reflector elements 35, 36 can be adjusted relative to arm 32. Each dipole and reflector element and spacer arm is capable of independent adjustment.

This construction not only provides sufficient flexibility to meet the varying requirements of individual installations but it can be packed and shipped fully assembled in a very conveniently handled container and installed in a few minutes of time. The dashed line (Fig. 12) indicates the proportions of length to width of the packing container required.

' Figs. 8, 9 and 10 show a modified form of the invention, wherein there are substituted for the dipole extensions 9?, 98 (Fig. 1) a trombone device comprising two U-shaped tubular metallic sliders 99-4529 and an outer tube lfll, fitted at-both ends with the usual knurled adjusting compression nuts. The Fig. 8 embodiment constitutes a folded dipole wherein elements 99, I may be slidably adjusted to vary the length of the two dipoles of the folded dipole. Parts 99; I58, IEH are installed after dipole elements 33, 34 are lined up. Tube IEH is fitted within an insulating sleeve I62, clamped by the curled end of a link H33, secured in place by nut 82 (Fig. 10).

"Fig. 11 shows a simple subcombination in accordance with the invention, wherein dipole ele--' ments are provided, without reflector. Here the inast i is flattened at its upper end, in like manner as portion 68 of spacer arm 3|, Fig. 1 and the subassembly of brackets :39, iii, dipole elements 3'3; 3 dipole extensions 91, ea, nut 82, bolt 8| and washers 83, 8d are mounted on that flattened end.

It will be seen that the Figs. 1-7 embodiment is not confined to use as a half-wave antenna. The dipole elements 33, 34 and extensions 97, 98 may be so proportioned that the antenna approximates in length a desired multiple of one-half wavelength. Further, by providing a transmis-, sion line and omitting the connecting links 95, 9 6 (Fig. 5) the reflector elements may be used as another dipole. In such case the two dipoles may be placed at any desired angle to each o her,

' The operating principles of half-wave antennas are well known and need not be stated herein. The length of each quarter-wave section of the dipole varies with frequency and should be ad-.

justed to the middle of the frequency band to be received. Each dipole element (including extension) is generally adjusted to a length slightly lessthan one-quarter wavelength, free space, according to a well-known formula.

Since the dipole has, in addition, the wellknown directivity feature and also has comparatively small physical dimensions in the- FM and television range of frequencies, it can be turned into a position for maximum reception of a desired station. It can also be turned to a position in space that weakens appreciably an undesired signal with respect to the desired signal. With present-day FM and television transmission, a dipole that can be rotated around a,.-vertical axis so as to keep the colinear dipole always horizontal is very satisfactory for most cases. However, it often happens that a dipole inclined direction toward ground and at the same time capable of rotation about a vertical-axis may give even better reception effects.

The directivity is increased when a reflector is used behind and parallel to the receiver dipole.

In practice, the spacing between the dipole elements and the reflector elements is generally adjusted to be from 0.1 to 0.25 wavelength free space spacing at the middle of the frequency band to be received.

At resonance the impedance of a half-wave simple dipole antenna isolated in free space is approximately 73 ohms at the center, while the impedance of a folded dipole is approximately 300 ohms. Nonresonant, current fed transmission lines are preferably employed and suitably matched to the antenna, according to wellknown principles.

The parasitic element or reflector is preferably slightly longer than the dipole. It absorbs power and reradiates it with such a phase relation to the original radiation that the fields of antenna and reflector add in one direction, whereby gain and directivity are increased. It will of course be appreciated that the parasitic elements 35, 36 and their extensions can also be used as a director, in which case the director is preferably slightly shorter than the dipole.

It will be understood that the Figs. 1-7 embodiment is also of utility as a transmitting antenna.

In one successful commercial embodiment of television receiving antenna in accordance with the invention, aluminum spacer arms, brackets, clamps, dipole elements and reflector elements were employed.

While there have been shown and described what are at present considered to be the preferred embodiments of the invention, it will be obvious to those skilled in the art that various modifications, changes and substitutions of equivalents may be made without departing from the invention as defined by the appended claims.

Havin clearly disclosed and fully described our invention, we claim:

1. A dipole antenna in combination with a reflector, comprising a foldable frame having a pair of angularly adjustable members comprising a crossbeam, a clamp for securing said members to a mast, a pair of rigid conductors, means for pivotally mounting said conductors on one end of said crossbeam, said conductors constituting said dipole, another pair of rigid conductors, means for pivotally mounting the other pair of conductors upon the other end of said crossbeam, the last named conductors constituting said reflector when disposed parallel to said dipole, means for locking said pairs of conductors in position in which the conductors constituting the dipole are parallel to the corresponding conductors constituting the reflector, and dielectric means for isolatingeach of said dipoleconductors from its mounting means.

2. The combination as set forth in claim 1 wherein the means for pivotally mounting the pair of conductors constituting the dipole on one end of the crossbeam comprises a flattened said end of said crossbeam and a pair of generally L- shaped clamping brackets pivotally mounted on said. flattened end portion.

3. The combination set forth in claim 1 where-- in the dielectric means for isolating each of said dipole conductors from its mounting means comprises an insulating sleeve mounted on each of said dipole conductors and within its said mount ing means.

4. The combination set forth in claim 1 wherein the clamp for securing said crossbeam members to said mast comprises a pair of generally L- shaped brackets pivotally mounted on said mast, each of said crossbeam members being pivotally mounted in one of said brackets. Number 5. The combination set forth in claim 1 includ- ,1 ing dielectric means for isolating each of said 5 2,230,738

reflector conductors from its mounting means and 5 conductive means for electrically connecting said 1 reflector conductors to each other and to said frame.

HAROLD A. NEWELL. 10 Number ALBERT W. KRAMER.

REFERENCES CITED The following references are of record in the file of this patent: 5 1948,

OTHER REFERENCES Hi-Gain Television and F. M. Antennas, Channel Master 00., Ellenville, New York, received July

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