Directable Multiband Antenna

Abstract

An electrically directable antenna having a plurality of radially extending dipole rods which may be selectively interconnected to provide various directivity patterns. In addition, various pairs of dipole rods within each directivity pattern may be selected such that optimum reception is obtained in each of a plurality of widely separated broadcast bands.

Description

The present invention relates to a television signal-receiving antenna having a plurality of directivity patterns which are individually selected by means of a switch unit located near the television receiver. In addition, the invention relates to an antenna wherein for each given directivity pattern, the operative elements of the antenna may be selected from among a plurality of pairs of dipole rods to thereby permit variation of the angular relationship of the operatively connected rods.

At the present time, conventional television signals are broadcast in one of three distinct and widely separated frequency bands, namely the low frequency VHF band (74-80 mc., Channels 2-6), the high frequency VHF band (174-216 mc., Channels 7-13), and the UHF band (470-890mc., Channels 14-83). Since a single antenna will not normally render equally satisfactory signal reception in all three bands, it is common practice to employ more than one antenna with separate feeder systems to the receiver for each band. Alternatively, a single antenna may include three separate elements with each of the elements being specifically designed to receive one of the bands.

It is also well known by those skilled in the art that the reception of television signals is greatly affected by the orientation of the receiving antenna with respect to the broadcast station. In the past, the desired orientation has usually been accomplished by mounting a motor on the mast to rotate the antenna in azimuth. Such arrangements, however, are expensive in that they require a weatherproof motor mounted on the mast, and also a relatively complex electrical control at the receiver.

In order to obtain directional orientation of an antenna without physical rotation thereof, a so-called electrically directable antenna has been proposed. Such an antenna comprises a plurality of fixed, variously directed dipole elements which are selectable by a selector switch located at the receiver to obtain directivity of reception. The directional switching devices of known design however are not capable of satisfactorily receiving all of the broadcast bands, and thus separate antennas are required in order to obtain proper reception in all three bands.

It is accordingly an object of the present invention to provide an electrically directable antenna adapted to receive at least three widely separated broadcast bands. More particularly, it is an object to provide a television antenna which can be adjusted for directional sensitivity without physical rotation thereof and which for each selected direction has a plurality of individually selectable pairs of signal receiving elements, each of which is specifically adapted to receive a predetermined broadcast band.

It is a further object of the present invention to provide an electrically directable antenna having a plurality of radially disposed dipole rods, and wherein various pairs may be operatively connected to the input terminals of the television receiver, with the nonselected or parasitic dipole rods serving as a signal reflector for the operatively connected or driven rods.

It is another object of this invention to provide an electrically directable antenna of the above type which is relatively simple in design, is collapsible for easy storage and handling, and wherein all the electrical connections are protected from the weather.

These and other objects and advantages of the present invention are achieved in the embodiment illustrated herein by the provision of an electrically directable antenna system having a plurality of individually selectable directivity patterns, as well as provision for receiving a plurality of widely separated broadcast bands in each of its selected directions. The system includes an antenna array comprising a plurality of dipole rods radially emanating from a central hub to define a plurality of directivity patterns. A plurality of pairs of the dipole rods are provided within each directivity pattern, with each pair defining an included angle which is substantially bisected by a line representing the directivity pattern of the antenna, and with each pair having a substantially different included angle from those of the remaining pairs. A control box, which is preferably positioned adjacent the television receiver, includes a first switch means for operatively selecting an individual directivity pattern, and a second switch means for operatively connecting an individual pair of dipole rods within the selected directivity pattern. Thus operation of the second switch permits variation of the angular relationship of the operatively connected pair of dipole rods within the preselected directivity pattern.

Some of the objects and advantages of the invention having been stated, others will appear as the description proceeds, when taken in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of the antenna array of the present invention;

FIG. 2 is a horizontal sectional view of the central hub of the antenna array;

FIG. 3 is a plan view of the hub as shown in FIG. 2 with the metal cover removed therefrom;

FIG. 4 is an exploded perspective view illustrating the terminal portion of one of the dipole rods and the manner of its assembly to the wall of the central hub;

FIG. 5 is a perspective view of the control box of the present invention;

FIG. 6 is a vertical sectional view of the control box taken substantially along the line 6--6 of FIG. 5;

FIG. 7 is a horizontal sectional view taken substantially along the line 7--7 of FIG. 6;

FIG. 8 is a horizontal sectional view taken substantially along the line 8--8 of FIG. 6;

FIG. 9 is a schematic representation of the control box contacts and the manner in which they are connected to the dipole rods of the antenna array and the television receiver lead-in line.

Referring to the drawings, an antenna array embodying the features of the present invention is illustrated generally at 10 in FIG. 1. The array is shown mounted on a mast 12, which in turn is secured to the roof top 14 in a conventional manner. The array comprises a central hub 16 and twelve radially emanating tubular signal-receiving elements in the form of dipole rods 18 which are seen to be evenly spaced about the circumference of the hub. The dipole rods are fabricated from conventional material such as 1/2 -inch aluminum tubing.

In the embodiment illustrated, each dipole rod carries a pair of diverging elements 20 fabricated from a material similar to that used in forming the dipole rods. The elements 20 lie generally in the plane of the dipole rods and are adjustably secured adjacent the inner end of the dipole rods by suitable clamps 22 such that the elements 20 extend radially outwardly on opposite sides of the associated dipole rods in a diverging manner. By releasing the clamps 22 and moving the elements 20 along the dipole rods 18, the maximum diameter of the array can be adjusted.

Each element 20 in turn carries a V-shaped wire whisker 24 at its remote end. The whiskers preferably each comprise a single length of aluminum wire which is looped in the middle to form the configuration shown, nd which is joined to its associated element by a suitable bolt (not shown). The two arms of each whisker 24 extend in a generally tangential direction and within a plane perpendicular to the element 20.

The various dimensions and other parameters for the various components of the array as shown will be determined by the desired operating characteristics, such as broadcast frequency and impedance, in a manner well known to those skilled in the art. However, the following specific dimensions have been found to be generally satisfactory for most operating conditions: length of each dipole rod--45 inches; length of each element--36 inches; length of whisker arms--9 inches. In addition, while twelve dipole rods are shown in the illustrated embodiment, it will be appreciated as the description proceeds that a somewhat greater or lesser number could be employed.

The hub 16 includes a cylindrical or tubular sidewall 26 constructed from a suitable dielectric material such as plastic, an upper cover 28 which may be metallic, nd a lower metallic bottom plate 29. One of the components of the hub may include a compass direction indicium to aid in properly orienting the array, such as the arrow N (for North) seen in FIG. 3 on the wall 26. The central portion of the bottom plate 29 includes an aperture 30, and a coaxial pipe flange 32 is welded or otherwise secured to the under surface of the plate 29. The pipe flange 32 is internally threaded and serves to secure the hub to the mast 12.

As best seen in FIG. 4, the sidewall 26 of the hub includes a plurality of key shaped apertures 34 which are adapted to receive and lock the radially inner or terminal portion of each dipole rod. The terminal portion includes a plug 36 having one end 37 frictionally or otherwise secured in the bore of the tubular dipole rod 18, and a flattened opposite end 38. The flattened end 38 of the plug is adapted to be received in the slot 39 of the stud 40 and is pivotally connected therein by a pin 41. A sleeve 42 is slidably mounted over the rod 18 and plug 36, and is designed to overlie the stud 40 such that the stud and rod are maintained in coaxial alignment. A setscrew 43 is provided in the sleeve to maintain its position. By this arrangement, each dipole rod 18 of the array may be pivoted in relation to the hub 16 as shown at the left side of FIG. 2, such that the entire array may be collapsed for easy handling and storage.

The inner end of the stud 40 includes a threaded portion 44 which is slotted at 45 to receive the transverse extension 46 of the key 48. When assembled, the stud 40 extends through the aperture 34 and is joined to the hub wall 26 by the nut 49 and washer 50 which are positioned outside the wall, and the nut 51 and washer 52 which are positioned on the inside of the wall. By design, the transverse extension 46 of the key 48 extends into the radial extensions of the opening 34 such that rotational movement of the key, and thus the stud 40 and dipole rod 18, is precluded.

The inner end of each key 48 mounts a first terminal connector 54 connected to one of the conductors 56 in the transmission cable 58, as well as a second terminal connector 60 for the purposes set forth below. It will be understood that the conductors comprise flexible insulated wires which are twisted together in forming the cable 58. If required, an impedance-matching transformer of conventional design (not shown) may be employed. The cable 58 is fed through the hollow mast 12, exits from the base thereof, and continues to a control box 62 which is preferably positioned adjacent the television receiver.

The interior of the hub 16 further includes a baffle means 63 which includes a plurality of radial spokes 64 (FIGS. 2 and 3) extending between but spaced from each of the terminal portions of the dipole rods. The outer ends of the radial spokes are secured to the hub wall by a suitable rivet or the like, and the inner ends are secured together by a central bolt 66. In the illustrated embodiment, the radial spokes 64 are flat metallic members which are electrically conductive, and they are connected via a conventional lightning arrester 68 and the terminal connector 60 to each of the keys 48. A ground wire 70 leads from the central bolt 68 to the metal plate 29. Since the mast 12 is suitably grounded, a lightning discharge path is thereby provided from the dipole rods of the antenna array to the ground.

The control box of the subject invention is illustrated generally at 62 in FIGS. 5-8. The box comprises a molded plastic cabinet 72 forming the top and sides of the box, and a metal bottom wall 73. The outer top surface of the cabinet may have various indicia 74, 75 imprinted thereon. Preferably, the indicia 74 represent the compass directions, and the indicia 75 represent the three broadcast bands, L for low-frequency VHF, H for high-frequency VHF, and U for UHF.

A dielectric panel 76 of plastic, Plexiglas, or other similar material, is fixedly secured within the cabinet and mounts twelve contacts 78 positioned in a circular arrangement. In the embodiment illustrated, each of the contacts comprises a flat-headed rivet secured in suitable apertures in the panel, and each is electrically connected to one of the conductors 56 in the transmission cable 58 as schematically illustrated in FIG. 9.

A control shaft 80 is rotatably mounted through the panel 76 along the vertical axis of the circular arrangement and extends upwardly through an aperture in the cabinet 72. A radially extending arm 82 of a similar dielectric material is secured to the shaft immediately above the panel, and a knob 84 is mounted at the upper end of the shaft on the outside of the cabinet. The outer periphery of the arm 82 is arcuate and generally conforms to the arc of the circle formed by the contacts 78. Six spring terminals 86 are attached to the arcuate periphery of the arm 82 and are adapted to engage six consecutive contacts. Thus by rotating the knob 84, various sequences of six consecutive contacts 78 will be engaged by the terminals 86. To prevent excessive rotation of the shaft in either direction, suitable stops (not shown) may be provided.

A second switch is provided in the control box and includes a drive shaft 88 which is also rotatably mounted in the panel 76. The drive shaft 88 carries an arm 90 which in turn mounts a first flexible terminal 92 for engaging one of a first set of three contacts 94, nd a second flexible terminal 96 for engaging one of a second set of three contacts 98. The terminals 92 and 96 are connected via lead lines 100 and 102 to the output terminals 104 of the cabinet. A knob 106 is mounted at the upper end of shaft 88. Here again, suitable stops (not shown) may be provided on the panel 76 to limit the rotation of shaft 88.

Viewing FIG. 9, it will be seen that the contacts 78 on the panel 76 are connected to correspondingly positioned dipole rods 18. Also, the six spring terminals 86 of the arm 82 are connected via suitable lead lines to the six contacts in the sets 94 and 98 in the manner shown. By design, the six consecutive contacts 78 engaged by the terminals 86 will define three pairs of dipole rods, each of which has an included angle which is substantially bisected by a common line representing the directivity of the antenna. Thus as shown, the antenna is directed for reception of a station located to the north, and a first pair of dipole rods A--A (FIG. 9) has an included angle of approximately 150.degree. which is bisected by a line from the north. A second pair of dipole rods B--B has an included angle of approximately 90.degree. which is bisected by a line from the north, and a third pair of dipole rods C--C with an included angle of about 30.degree. is similarly bisected by a line from the north. Thus upon rotation of the knob 84 to any of its 12 positions, there will always be three pairs of dipole rods which have an included angle substantially bisected by a line representing the operatively connected directivity pattern of the antenna.

The second switch, represented by knob 106, is effective to select the particular pair of dipole rods to be operatively connected to the television receiver. In particular, rotation of the knob 106 translates the terminals 92 and 96 in unison across the contacts 94 and 98. At the position shown, the pair A--A of dipole rods are connected. At the mid position of the terminals 92 and 96, the pair B--B will be connected, and at the right end position the pair C--C will be connected.

In operation, the first switch (i.e., knob 84) is rotated to direct the operative dipole rods toward the desired broadcasting station. The second switch (i.e., knob 106) is then positioned at the particular broadcast band being received such that a single pair of dipole rods will be operatively connected to the receiver.

It has been found that when the knob 106 is positioned as shown (i.e., directed at L) such that the dipole rods A--A are operatively connected to the receiver, improved reception in the frequency VHF band is obtained. When the knob 106 is rotated to its midposition (to H) such that the dipole rods B--B are operatively connected, improved reception in the high frequency VHF band is obtained, and finally, when the knob 106 is positioned toward the right (at U) such that the dipole rods C--C are operatively connected, improved reception in the UHF band is obtained. It is believed that these surprising results are achieved by reason of the fact that the three pairs of dipole rods present differing effective dipole dimensions in the direction of the broadcasting station. Thus the extended pair A--A is more effective for lower broadcast frequencies having longer wave lengths, the intermediate pair B--B is more effective for the intermediate frequencies having somewhat shorter wave lengths, and similarly, the contiguous pair C--C is more effective for the higher frequencies. However, the operability and advantages of the antenna described herein are not predicated upon any particular theoretical explanation of operation, but rather are based on the actual operation of the antenna combination.

As a further aspect of the present invention, it has been found that the radial spokes 64 of the baffle means 62 act to proximately connect the oppositely directed dipole rods to permit the effective transmission of the broadcast signals therebetween. Thus the pair of dipole rods immediately behind the operatively connected or driven pair will serve as reflectors to increase the gain of the driven pair. For example, if the pair B--B is connected, the pair A--A serve as a reflector.

In the drawings and specification, there has been set forth a preferred embodiment of the invention, and although specific terms are employed, they are used in a generic and description sense only and not for purposes of limitation.

Claims

I claim:

1. An electrically directable signal-receiving antenna system having provision to obtain optimum reception from a plurality of widely separated broadcast bands and comprising,

a plurality of radially arranged signal-receiving elements defining a plurality of directivity patterns with a plurality of pairs of said signal-receiving elements within each directivity pattern, each of said pairs of signal-receiving elements defining an included angle which is substantially bisected by a line representing the directivity pattern of the antenna and with each of said pairs having a substantially different included angle from those of the remaining pairs,

first switch means for operatively selecting and individual directivity pattern, and

second switch means for operatively connecting an individual pair of signal-receiving elements within the selected directivity pattern to hereby permit variation of the angular relationship of the operatively connected pair of signal-receiving elements.

2. The antenna system as defined in claim 1 wherein there are at least twelve signal-receiving elements which are evenly disposed in the radial arrangement, and wherein there are three pairs of signal-receiving elements within each directivity pattern.

3. An electrically directable signal-receiving antenna system comprising,

an antenna array comprising a central hub and a plurality of signal-receiving elements radially emanating therefrom in an evenly spaced configuration to define a plurality of directivity patterns for the antenna, the radially inner ends of said signal-receiving elements extending into said hub with each end being electrically insulated from the remaining ends,

switch means for operatively interconnecting selected pairs of said signal-receiving elements to permit selection of an individual directivity pattern, and

electrically conductive baffle means positioned within the hub and having radial spokes extending between and spaced from the inner ends of adjacent signal-receiving elements for proximately connecting oppositely directed signal-receiving elements whereby the same serve as signal reflectors for the operatively interconnected pair of signal-receiving elements.

4. The antenna system as defined in claim 3 wherein said radial spokes of the baffle means are electrically connected to the adjacent inner ends of the signal-receiving elements across a lightning arrester, and wherein said baffle means is grounded.

5. An electrically directable signal-receiving antenna system having a plurality of individually selectable directivity patterns and provisions for receiving signals from three distinct and widely separated broadcast bands in each of the directivity patterns and comprising,

an antenna array comprising a central hub and a plurality of dipole rods radially emanating therefrom in an evenly spaced configuration,

a control box having a plurality of consecutively aligned contacts corresponding in number to the number of dipole rods, and a pair of outlet terminals adapted to be connected to the lead-in line of a television receiver,

means for electrically interconnecting each dipole rod with one of said contacts such that consecutive dipole rods are connected to consecutive contacts,

first switch means for orienting the directivity pattern of the antenna and comprising six terminals for engaging size of the contacts, said terminals being arranged such that the six engaged contacts will be connected to three pairs of dipole rods with all three pairs having an included angle bisected by a common line representing the directivity of the antenna, and

second switch means for operatively connecting one of said three pairs to said control box outlet terminals.

6. The antenna system as defined in claim 5 wherein the central hub comprises a tubular wall having a plurality of radially directed, evenly spaced holes therethrough, said dipole rods including a terminal portion extending through respective ones of said holes and being secured to said tubular wall.

7. The antenna system as defined in claim 6 wherein said central hub further includes baffle means having radial spokes extending between he terminal portions of the dipole rods for proximately connecting radially opposed dipole rods to thereby serve as a signal reflector for the operatively connected pair of dipole rods.

8. The antenna system as defined in claim 6 wherein said electrical connecting means includes a transmission cable having a plurality of individual conductors therein corresponding in number to the number of dipole rods, one end of each conductor being electrically connected to one of said dipole rod terminal portions and the other end of each conductor being electrically connected to one of the contacts in said control box.

9. The antenna system as defined in claim 8 wherein said first switch means comprises a panel mounting said contacts in a circular arrangement, a control shaft and knob rotatably mounted to said panel, along the vertical axis of the circular arrangement, a radially directed dielectric arm fixedly mounted to said shaft immediately above the panel, and six spring terminals mounted to said dielectric arm for engaging six of the contacts.

10. The antenna system as defined in claim 9 wherein said second switch means comprises a first set of three contacts and a second set of three contacts, each of the contacts in the first and second sets being electrically connected to a different one of the six spring terminals, a rotatable drive shaft and knob, a first arm fixedly mounted to said drive shaft and adapted to rotate with said drive shaft for selective engagement with one of the contacts in said first set, and a second arm fixedly mounted to said drive shaft and adapted to rotate with said drive shaft for selective engagement with one of said contacts in said second set, said first and second arms being electrically connected to said pair of outlet terminals.

11. The antenna system as defined in claim 10 further including a pair of diverging elements adjustably secured adjacent the inner end of each dipole rod, said elements lying substantially in the plane of said dipole rods and extending radially outwardly on opposite sides of the associated dipole rod.

12. The antenna system as defined in claim 11 further including a V-shaped wire whisker attached at the outer extremity of each diverging element, each whisker extending in a tangential direction and lying a plane substantially perpendicular to the associated diverging element.

13. The antenna system as defined in claim 12 wherein each dipole rod includes a pivotal joint immediately adjacent the hub such that the dipole rods may be folded into a generally parallel arrangement for easy handling and storage.