US3268898A

US3268898A - Demountable variable length antenna

Info

Publication number: US3268898A
Application number: US244039A
Authority: US
Inventors: Charles G Colony
Original assignee: Avco Corp
Current assignee: Avco Corp
Priority date: 1962-12-12
Filing date: 1962-12-12
Publication date: 1966-08-23
Anticipated expiration: 1983-08-23

Description

CROSS REFERENCE SEARCH ROOM m gm Aug. 23, 1966 c. G. COLONY DEMOUN'IABLE VARIABLE LENGTH ANTENNA Filed Dec. 12. 1962 2 Sheets-Sheet 1 FIG. 1

CONTROL SIGNAL INVENTOR. CHARLES G. COLONY ATTORNE Y3 United States Patent 3,268 898 DEMOUNTABLE VARIAliLE LENGTH ANTENNA Charles G. Colony, Cincinnati, Qhio, assignor to Avco Corporation, Cincinnati, Ohio, a corporation of Delaware Filed Dec. 12, 1962. Ser. No. 244,039 '6 Claims. (Cl. 343723) The present invention relates to demountable variable length antennas and more particularly to a variable length antenna supported within a dieelectric mast formed of telescoping mast sections.

In a portable communication station the antenna is an important element. At the same time it is an element which presents inherent difficulties which, if not overcome, may counteract to a substantial extent the advantages possible in the use of miniaturization techniques in radio transmitters and receivers.

The prime requisite of an antenna is that it be an efficient radiator. Throughout this description and in the claims it will be understood that the antenna of the present invention is susceptible for use either as a transmitting or receiving antenna. An antenna which is a good radiator is inherently a good receiver as well, according to the well-known principle of reciprocity in the design of transmitting and receiving antennas. It is generally a requirement for efiicient radiation that the antenna be of substantial dimension. At the same time, it is re quired to be easily transported and erected, stable in service and quickly demountable for removal to another location. In military applications it should be as inconspicuous as possible.

In many antenna applications, and particularly in military applications, it is desirable that the antenna be suitable over a substantial range of frequencies with a minimum of time loss for antenna tuning, Ideally, any antenna tuning required should be carried out automatically in conjunction with the tuning of the transmitter or receiver.

In addition to providing the above described features and advantages, it is an object of the present invention to provide an antenna which is easily erectable or demountable and which includes the capability of very rapid antenna tuning by changing the effective length of the antenna radiator. It is another object of the invention to provide an antenna of the foregoing type in which the antenna mast is very compact when demounted by virtue of its telescopic construction.

It is still another object of the present invention to provide an antenna of the foregoing type wherein the radiator may be effectively lengthened or shortened in response to an electrical control signal supplied to a servomotor.

Other objects and advantages will be apparent from a consideration of the following description in conjunction with the appended drawings in which:

FIGURE 1 is an elevational view of an antenna according to the present invention;

FIGURE 2 is a fragmentary sectional view taken along the line 22 in FIGURE 1;

FIGURE 3 is a fragmentary sectional view of the top portion of the antenna structure illustrated in FIGURE 1;

FIGURE 4 is a sectional view taken along the line 4-4 in FIGURE 3;

FIGURE 5 is a partially sectional view taken along the line 55 in FIGURE 1;

FIGURE 6 is a sectional view taken along the line 3,2683% Patented August 23, 1966 graduated size supported end-to-end to form a mast structure.

A lowermost mast section 16 is rigidly secured to a base structure 13 which supports the antenna and houses reels for storing the flexible radiator element and support cord as will later be described.

A housing 14 at the top of the antenna mast contains a pulley and reel mechanism later to be described. The mast may be supported by guy ropes 15 if necessary or, in View of its light weight, may in some cases be supported by stakes securing the base 13 to the ground.

In addition to the antenna contained internally within the mast of antenna assembly 11, the assembly may be utilized to support additional independent antennas such as the corner reflector antenna 20 illustrated in dotted lines in FIGURE 1.

As will later be seen the antenna assembly 11 may be demounted by telescoping or nesting the mast sections 12 into the lowermost mast section 16. In this case the housing 14 occupies the position shown in dotted lines in FIGURE 1, and the antenna assembly is reduced to a relatively small dimension and is easily transportable. The various elements in FIGURE I particularly the base 13 and the housing 14 should not be considered to be drawn to scale as they may be considerably smaller relative to the antenna assembly 11. The size of the elements in FIGURE 1 and in the other figures is generally selected for clarity of illustration rather than as representative of optimum size in a practical device.

As has previously been explained, it is a feature of the present invention to provide an antenna which is not only readily demountable and transportable but also is rapidly tunable. The manner in which the antenna is tuned by changing the eifective length of the radiating element may be understood by reference to FIGURES 2, 3 and 4.

Referring to FIGURE 2, a conductive radiator element comprising a tape 17 is supported within the antenna assembly by a support cord 18 of dielectric material which may conveniently be a rope or cord of cotton, hemp, or of synthetic fiber such as nylon or the like. As viewed in FIGURE 3, the antenna element 17 and the cord or lanyard 18 comprise a two-sided continuum.

A pulley or hanger element 51 is provided at the top of the antenna assembly so that the tape 17 may be raised and lowered by means of cord 18 as will later be de scribed in more detail.

The tape 17 is conductive and may comprise a thin flexible metal tape. Alternatively, tape 17 may be formed of plastic sheet material such as polyethylene or polypropylene upon which is coated a film of conductive material such as aluminum, silver, or the like.

The unextended portion of tape 17 is stored on a reel 19. Suitable means is provided for making an electrical connection to the tape 17. In the particular embodiment illustrated, tape 17 is a metal tape making electrical contact to metal reel 19 and thence through a sliding contact 21 to the center conductor 23 of 'a coaxial cable 22 or other appropriate transmission line. The cable 22 would of course be connected to the transmitter and/ or the receiver associated with antenna assembly 11. The outer conductor of cable 22 may be grounded by a suitable electrical ground connection 24.

The tape 17 may alternatively be electrically isolated from ground potential by a radio frequency choke. The last few turns of thetape on reel 19 will provide such a choke if the turns are mutually insulated as in the case where the tape comprises a non-conductive base having a conductive film deposited thereon. With such a choke arrangement contact 21 should brush on tape 17 directly.

Reel 19 is supported on and keyed to a shaft 25 but is insulated therefrom in order to prevent electrical ground- 3 ing of reel 19. Shaft 25 is supported within base 13 by supports such as 26.

Shaft 25 and hence reel 19 are driven by an electrical servomotor 29 connected to shaft 25 through a suitable flexible coupling 28.

A reel 31 is provided for support cord 18 and is mounted on shaft 25 but is not keyed to the shaft. Reel 31 is coupled to shaft 25 by a clock-spring 32. Spring 32 provides a bias torque which maintains tension in cord 18 and tape 17. Cord 18 and tape 17 are wound respectively on

reels

31 and 19 in opposite senses so that upon rotation of the reels by servomotor 29, tape 17 is paid out while cord 18 is reeled in or vice versa. Any small difference in the rate of pay out between the two reels is accommodated by spring 32. In addition to, or in place of, the resilience provided by spring 32 the cord 18 may be resiliently stretchable. Preferably the tape 17 is not stretchable as the length of the antenna is measured and cantrolled by the pay out of tape 17.

Tape 17 is provided with holes 33 extending longitudinally of the tape which provide index marks for measuring the amount of extension of the tape. Obviously the tape could be provided with other index marks such as notches in the edge, corrugations or the like or imprinted index marks could be utilized in connection with a photoelectric sensing means.

The sprocket 34 engages the holes 33 and tape 17 and is connected by a shaft 35 to a multiple turn potentiometer and indicator 36. The multiple turn potentiometer 36 may be of conventional design and provides a feedback voltage to servomotor 29 proportional to the length of extension of tape 17. The potentiometer 36 may be of the indicating type and a window 37 may be provided for direct reading of the length of antenna extension. The length of antenna extension is substantially proportional to the tuning of the antenna in wavelengths so that the potentiometer 36 and other controls for the antenna tuning may he calibrated directly in terms of wavelength (or of frequency which is an inverse function of Wavelength).

The electrical feedback signal from potentiometer 36 is transmitted over leads 38 to servomotor 29 which is also provided with a control signal over leads 39. As is Well known, the function of a servomotor such as 29 is to operate to equalize the feedback signal provided over loads 38 with the control signal provided over leads 39. This is done by causing extension or retraction of tape 17, and thus the amount of extension of tape 17 is rendered directly responsive to the amplitude (or other parameter) of the control signal 39.

The servo control for the tuning of antenna assembly 11 is of course merely exemplary and any of many known forms of servo control may be substituted for that schematically illustrated and described for purposes of explanation.

Referring now to FIGURE 3, the reel housing 14 is supported at the top of the topmost 'mast section 12. Rings 41 may be provided on housing 14 to secure guy ropes such as 15 illustrated in FIGURE 1. A storage reel or spool 42 is rotatably mounted within housing 14 on a shaft 43 and is keyed for rotation therewith.

Shaft 43 is connected through a gear train comprising gears 44, 45, 46 and 47 to a clock spring 48 so that reel 42 is pro-loaded to cause tape 17 and cord 18 to be wound onto reel 42 as the antenna assembly 11 is collapsed by telescoping the mast sections 12 into one another and into the bottom mast section 16. The gear train 44, 45, 46 and 47 causes one turn of winding or unwinding of spring 48 to result in numerous turns of reel 42. The outer end of spring 48 is secured to housing 14 by pin 49. As will be seen from FIGURE 3 in conjunction with FIGURE 4, a pulley 51 is mounted on reel 42 for free rotation about shaft 52. When the antenna is arranged for operation as illustrated in FIGURE 1, the position of pulley 51 is as shown in FIGURES 3 and 4 allowing tape 17 readily to be raised by cord 18. When the antenna is demounted by telescoping mast sections 12, tape 17 and/ or cord 18 are reeled onto reel 42 by the action of spring 48. As shown in FIGURES 3 and 4, the spool 42 is formed with end flanges and an axially extending curvilinear cutout portion into which the pulley 51 partially extends (FIGURE 4).

Reels

19 and 31, for storage of

tapes

17 and 18 dur ing operation of the antenna, and reel 42, for demounted storage of cord 18 and tape 17, are, of course, merely illustrative storage and reeling means for tape 17 and cord 18 and various other arrangements to perform the same function may be devised by those skilled in the art. By way of example,

reels

19 and 31 need not be mounted coaxially but may be mounted on parallel axes and coupled for simultaneous rotation by gearing or other suitable means.

Thus far, the antenna assembly has been explained primarily with reference to its operative or extended position. FIGURES 5, 6 and 7 illustrate the construction of mast sections 12 which allows the antenna assembly to be readily telescoped for demounting and at the same time provide a strong and light mast structure for supporting the internal antenna radiator and such external antenna structures as the corner antenna illustrated in FIGURE 1.

Referring now to FIGURES 5, 6 and 7, intermediate mast sections 12 are shown which are of generally similar construction but of graduated size so that they fit one within the other. In the preferred form of the invention illustrated, each individual mast section is also tapered slightly so that it has a somewhat smaller dimension at the top than at the bottom.

In FIGURE 5 the topmost mast section 12 has a tubular body 60 with an enlarged bottom portion 61. At the bottom of the tube 60 are oppositely disposed lugs 62 and 63, the latter being shown in dashed lines in FIG- URE 5.

The middle mast section 12 in FIGURE 5 is formed of a tubular body 64 and is of similar construction to the upper mast section with an enlarged bottom portion 65 and lugs at the bottom end, only one of which, 66 is shown in dash line. The tubular body 64 is of larger diameter than the tubular body 60 so that the latter telescopes into the former.

At the top of tubular body 64 is a collet 67 which prevents over-travel of tubular body 60 with respect to tubular body 64 when the former is being extended and which also causes tubular body 60 to fit snugly within tubular body 64 to provide a substantially rigid upright mast.

Within tubular body 64 there are two

guide members

68 and 69. Guide member 68 extends substantially to the lower end of tubular body 64 and engages

lugs

62 and 63 on tubular body 60 to .prevent undesired rotational movement between tubular body 60 and tubular body 64.

Guide 69 is shown only in dotted lines in FIGURE 5 and does not extend to the lower end of tubular body 64 as only one guide is needed to restrain rotational movement between successive mast sections.

Guide members

68 and 69 are provided respectively with upwardly extending

stops

71 and 70 which allow relative movement of somewhat less than degrees between tubular body '60 and tubular body 64 when the former has been fully extended. After such rotation tubular body 60 is supported in extended position by the fact that lugs 62 and 63 rest respectively on

guide members

68 and 69.

The lower edge 62a of lug 62 and the upper edge 68a of guide member 68 are sloped toward stop 71 so that the weight of the mast sections tends to maintain them in the locked position so that they do not inadvertently become unlocked in the presence of vibration or shock due to Wind or the like. Of course, guide member 69 and lug 63 have similarly sloped edges. If necessary or desired the slope could be made greater than that illustrated in FIGURE 5 or could be replaced by a step to provide positive locking.

As previously noted the various mast sections have similar construction and it may be noted for example that the lower end of guide member 72 for hollow tubular body 60 is seen in the sectional View of FIGURE 6.

Wide latitude is possible in selection of materials for construction of mast sections 12. A light dielectric material is preferable, for example fiber glass roving laminated with polyester resin. The tube sections may be further overwrapped with a spiral wrap of laminated fiber glass roving and epoxy resin. Strength and durability will be enhanced if at least 60 percent of the laminate by volume consists of fiber glass roving.

The lug and guide members forming a part of the mast sections may also be formed of laminated fiber glass and may be secured in place by an epoxy resin adhesive.

Virtually any dielectric material of suitable physical strength may be utilized to form the mast sections and they may .be formed by laminating on a mandrel or they may alternatively be formed of a plastic material such as polyethylene .or polypropylene and cast or molded in a single unitary piece.

From the foregoing explanation it will be appreciated that an antenna is provided which occupies a relatively small volume for storage and transportation and which is readily erected to form an antenna of substantial height eg from 30 to 50 feet high. The mast structure height is generally fixed and constant in operation, but the internal radiating element is of adjustable length to provide a wide range of antenna tuning. The adjustment of the radiator length may be accomplished by a servomotor synchronized with the receiver or transmitter tuning adjustment.

Although the antenna particularly described is a monopole antenna, the invention may be adapted to dipole antennas by utilizing the techniques described in copending application Serial No. 244,184, tiled December 12, 1962 for Extendible Dipole Antenna in the names of John A. Kuecken and Charles Gordon Colony.

In addition to the various modifications of the embodiment of the invention herein described or suggested, numerous other variations and modifications may be devised by those skilled in the art. Accordingly it is desired that the scope of the invention not be limited to those particu lar embodiments and modifications shown or suggested but that the scope of the invention be determined by reference to the appended claims.

1 claims 1. A demountable antenna with radiator of adjustable eflective length comprising a plurality of elongated hollow tapered dielectric mast sections arranged to form a telescoping dielectric mast, means for locking said mast sections in an extended position, means for supporting said mast sections in an extended upright position, a freely rotatable pulley positioned in the top of the topmost mast section, a conductive flexible tape having indexing apertures, a nonconductive elongated flexible support within said mast sections extending over said pulley and secured to said tape, respective storage reels for said support means and for said tape positioned at the bottom of said rnast sections, said reels being coupled together to pay out one of said tape and support means while the other of said tape and support means is being taken in, means for biasing said reels with respect to one another to maintain tension in said tape and support means, sensing means engaging the indexing apertures of said tape for generating an electric signal in response to the displacement of said tape, a servo-motor electrically connected to be responsive to said sensing means and mechanically connected to drive said reels to cause the displacement of said tape to substantially correspond to an independent 6 control signal supplied to said servomotor, and means for reeling in said tape and said flexible support in conjunction with telescoping of said mast sections.

2. A demountable antenna with radiator of adjustable effective length comprising a plurality of elongated hollow tapered dielectric mast sections arranged to form a telescoping dielectric ma-st, means for looking said mast sections in an extended position, means for supporting said mast sections in an extended upright position, a freely rotatable pulley positioned in the top of the topmost mast section, a conductive flexible tape having indexing apertures, a nonconductive elongated flexible support Within said mast sections extending over said pulley and secured to said tape, respective storage reels for said support means and for said tape positioned at the bottom of said m'ast sections, said reels being coupled together to pay out one of said tape and support means while the other of said tape and support means is being taken in, means for biasing said reels with respect to one another to maintain tension in said tape and support means, sensing means engaging the indexing apertures of said tape for generating an electric signal in response to the displacement of said tape, and a servo-motor electrically connected to be responsive to said sensing means and mechanically connected to drive said reels to cause the displacement of said tape to substantially correspond to an independent control signal supp-lied to said servo-motor.

3. A demountable antenna with radiator of adjustable effective length comprising a plurality of elongated hollow tapered dielectric mast sections arranged to form a telescoping dielectric mast, means for locking said mast sections in an extended position, means for supporting said mast sections in an extended upright position, .a freely rotatable pulley positioned at the top of the topmost mast section, a conductive flexible tape having indexing apertures, a nonconductive elongated flexible support extending over said pulley and secured to said tape, respective storage reels for said support means and for said tape positioned at the bottom of said mast sections, said reels being coupled together to pay out one of said tape and support means while the other of said tape and support means is being taken in, means for biasing said reels with respect to one another to maintain tension in said tape and support means, and sensing means engaging the indexing apertures of said tape for sensing the displacement of said tape.

4. An antenna with radiator of adjustable effective length comprising a plurality of elongated hollow dielectric mast sections adapted to nest one within another in a demou-nted position and to engage end-to-end in an operative position, means for supporting said mast sections in an upright position engaged end to end, and a radiator element of adjustable effective length supportable in an upright position by said end-to-end engaged mast sections, said element comprising an elongated flexible conductive element, elongated flexible nonconductive support means secured to said conductive element for controllably positioning said conductive element longitudinally of said end-to-end engaged rnast sections means including an idler pulley for drawing in and for extending said support means and means including a spool on which the idler pulley is mounted for storing the unextended portions of said support means and said conductive element.

5. A collapsible antenna comprising:

a plurality of hollow dielectric telescoping mast sections including a top section and a bottom section and adapted to be extended as an elongated antenna support or to be nested;

first and second storage reels positioned at the bottom of said rnast sections;

a spool mounted for rotation at the top of the top mas-t section, said spool being formed with end flanges and an axially extending curvilinear cutout portion;

an idler pulley rotatably mounted on said flange and disposed at least in part within said cutout portion;

a flexible antenna and a flexible halyard joined to form a continuum looped around said pulley, the antenna being reeled or unreeled by the other of said storage reels;

and spring means for biasing said spool so that, as the dielectric mast is collapsed, the spool is turned and the axis of the pulley rotates about the axis of the spool, whereby the continuum is Wound up.

6. A collapsible antenna comprising:

a hanger element mounted at the top of the top mast section;

a flexible antenna and a flexible halyard joined to form a two-sided continuum looped around said hanger element;

means for reeling in and out said antenna and halyard;

and spring-urged means for simultaneously reeling in both sides of said continuum in the same direction as the mast sections are nested.

References Cited by the Examiner UNITED STATES PATENTS 2,119,692 6/1938 Voigt 343-723 X 2,283,524 5/1942 White 343-723 X 2,366,634 1/1945 Ludwig 343-883 2,424,598 7/1947 Willough'by 343-723 2,522,222 9/1950 Haller 343-723 X 2,834,012 5/1958 Allen 343-723 FOREIGN PATENTS 903,839 8/1962 Great Britain. 175,483 7/ 1935 Switzerland.

ELI LIEBERMAN, Primaly Examiner.

Claims

4. AN ANTENNA WITH RADIATOR OF ADJUSTABLE EFFECTIVE LENGTH COMPRISING A PLURALITY OF ELONGATED HOLLOW DIELECTRIC MAST SECTIONS ADAPTED TO NEST ONE WITHIN ANOTHER IN A DEMOUNTED POSITION AND TO ENGAGE END-TO-END IN AN OPERATIVE POSITION, MEANS FOR SUPPORTING SAID MAST SECTIONS IN AN UPRIGHT POSITION ENGAGED END TO END, AND A RADIATOR ELEMENT OF ADJUSTABLE EFFECTIVE LENGTH SUPPORTABLE IN AN UPRIGHT POSITION BY SAID END TO END ENGAGED MAST SECTIONS, SAID ELEMENTS COMPRISING AN ELONGATED FLEXIBLE CONDUCTIVE ELEMENT, ELONGATED FLEXIBLE NONCONDUCTIVE SUPPORT MEANS SECURED TO SAID CONDUCTIVE ELEMENT FOR CONTROLLABLY POSITIONING SAID CONDUCTIVE ELEMENT LONGITUDINALLY OF SAID END-TO-END ENGAGED MAST SECTIONS MEANS INCLUDING AN IDLER PULLEY OF DRAWING IN AND FOR EXTENDING SAID SUPPORT MEANS AND MEANS INCLUDING A SPOOL ON WHICH THE IDLER PULLEY IS MOUNTED FOR STORING THE UNEXTENDED PORTIONS OF SAID SUPPORT MEANS AND SAID CONDUCTIVE ELEMENT.