Abstract:
An antenna and mounting device assembly fits on opposite sides of an aircraft to handle radio signals during flight. The antenna has a boom and radiating elements extending normal to the boom. The mounting device includes a first clamping bracket that attaches to the exterior of the aircraft, a pair of spaced arms that are twisted relative to the longitudinal axis of the first clamping bracket to orient the antenna relative to the horizontal and a second clamping bracket that attaches to the antenna.

Description:
TECHNICAL FIELD 
     This invention in general relates to handling radio signals on an aircraft and more particularly an antenna and mounting device assembly and a signal handling system using two of said assemblies preferably to receive radio signals remote from the aircraft. 
     BACKGROUND ART 
     One of the most efficient methods for radio tracking far ranging animals equipped with radio beacons is to use an aircraft. To perform aerial tracking the aircraft must be equipped with one or more antennas fitted to the airplane in such a manner as to comply with FAA airworthiness standards. It is important to comply with the regulations to avoid grounding of the aircraft by the FAA, to avoid violation and possible cancellation of insurance policies to both personnel and aircraft and to release liability obligations. Any externally mounted structure on an aircraft must be tested to ensure that the device does not interfere with aircraft controls, reduce the strength of the aircraft or adversely affect flight characteristics. 
     An antenna mounted externally of an aircraft is disclosed in Bolljahn Ser. No. 2,505,751 having an antenna made of thin, flat, metal strips affixed to the ground plane by four angle pieces. Ganz Ser. No. 4,336,543 discloses an electronically scanned antenna system having a linear array of Yagi type endfire elements on the wing of an aircraft. 
     DISCLOSURE OF THE INVENTION 
     In accordance with the present invention, there is provided an antenna and a mounting device assembly that will fit on both the left and right sides of an aircraft, particularly an aircraft with a strut such as the Model 172 Cessna to handle and particularly receive signals transmitted remote from the aircraft. The antenna disclosed is of the Yagi type having a boom and suitable radiating elements fastened to the boom so as to provide a desirable signal reception pattern during flight. The mounting device includes a first clamping bracket that fits against the wing strut and has a plurality of spaced straps that encircle the first clamping bracket and the strut for releasably gripping the strut. Spaced first and second arms extend from the first clamping bracket and are twisted relative to the longitudinal axis of each arm at a selected angle to orient the antenna relative to the horizontal and carry second clamping means including first and second antenna clamping brackets that clamp to the antenna 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Details of this invention are described in connection with the accompanying drawings which like parts bear similar reference numerals in which: 
     FIG. 1 is a front elevation showing a signal reception system including left and right side assemblies on an aircraft embodying features of the present invention. 
     FIG. 2 is a top plan view as seen along line 2--2 of FIG. 1 of the left side assembly. 
     FIG. 3 is a front elevation view of the left side assembly as seen along line 3--3 of FIG. 2. 
     FIG. 4 is an end elevational view of the folded dipole element mounted to the boom as seen along line 4--4 of FIG. 3. 
     FIG. 5 is a sectional view taken along line 5--5 of FIG. 2. 
     FIG. 6 is a sectional view taken along line 6--6 of FIG. 2. 
     FIG. 7 is a sectional view taken along line 7--7 of FIG. 2. 
     FIG. 8 is a sectional view taken along line 8--8 of FIG. 7. 
     FIG. 9 is a sectional view taken along line 9--9 of FIG. 2. 
     FIG. 10 is a sectional view taken along line 10--10 of FIG. 9. 
     FIG. 11 is a top plan view of the mounting device without the antenna and strut shown. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIG. 1 there is shown a signal handling system for an aircraft 12 shown in schematic form as having a left side strut 13 and a right side strut 14. The signal handling system shown includes a left side antenna and mounting device assembly 15 and a right side antenna and mounting device assembly 16. The antenna and mounting device assemblies 15 and 16 are of the same construction and differ only in being constructed for left and right side mountings, respectively. A detailed description will now be made of the left side antenna and mounting device assembly 15. 
     The antenna 21 shown is of the Yagi type and comprises a boom 22 (FIGS. 2, 3 and 5) made of a preselected length of preferably aluminum tubing. There are three active elements mounted to the boom 22. The first active element 24 (FIGS. 1, 2 and 4) is the driven element, the second active element 25 is the director element and the third active element 26 is the reflector element. The driven element 24 is a folded dipole including two parallel spaced conductive rods, 28, 29, preferably aluminum, connected at the ends by two curved end sections 31 and 32. There is a gap or space 36 between the ends 34 and 35 midway between the ends of rod 29 which are the feed ends of the driven element 24. Feed ends 34 and 35 are connected to feed terminals 34a and 35a, respectively. 
     The folded dipole is matched for a 50 ohm receiving system by means of a half-wave balun phasing section 33 (FIG. 2) connected to the feed terminals. The folded dipole construction takes advantage of the additional mechanical strength and rigidity provided by having two parallel spaced rods. 
     The driven element 24 is mounted to the boom 22 by means of a first boom mounting device 37 (FIGS. 2 and 5) made of a nonconductive material. The mounting device 37 includes a front mounting member 41 and a rear mounting member 42 (FIGS. 4 and 5) each of which are a single, solid, molded, plastic body. The front mounting member 41 has an oblong base 44 with a semicircular recess 45 along a rear face to fit against and conform to the exterior surface of about half of the cross section of the boom 22. A raised portion 46 is offset to one side and projects forwardly of base 44. A hole 47 (FIG. 6) in the raised portion 46 and base 44 is provided through which the rod 29 extends and is rigidly fastened as by molding the rod in the molded body. A hole 48 extends through the center of the base and a bolt fastener 49 extends through the hole 48 and an aligned hole 50 in the boom. 
     The rear mounting member 42 is substantially a mirror image of the front mounting member 41 having an oblong base 54 with a semi-circular recess 55 in the front face of the base that conforms to the exterior surface of the boom 22, a raised portion 56 offset to one side with a hole 57 through which the rod 28 extends and is rigidly fastened by molding. A hole 58 in the base 54 is aligned with bolt hole 48 and the boom hole 50 through which the bolt fastener 49 extends. A nut 61 and washer 62 are on the end of fastener 49 with the nut threading on external threads of the bolt to firmly clamp the front and rear mounting members 41 and 42 (FIG. 4) against the boom by forces applied from opposite directions toward the center of the boom with the mounting device 37 functioning to electrically insulate the driven element 24 from the boom. The ends 34 and 35 of the element are shown clamped between the front and rear mounting members 41 and 42 with the feed terminals 34a and 35a (FIG. 4) being on the outer side of member 41. 
     The director element 25 (FIGS. 2, 3 and 6) and the reflector element 26 are each a single, straight aluminum rod and each are mounted to the boom and electrically insulated therefrom as is element 24. Element 25 is mounted to the boom by a nonconductive mounting member 65. Element 26 is mounted to the boom by a nonconductive mounting member 66. Members 65 and 66 are of the same construction so a description of one applies to both. Referring to member 65 it is a single, solid, molded, plastic body and shown to have an oblong base 67 with a semi-circular recess 68 on the rear face that fits against the boom 22 and encompasses about one half the cross section of the boom. An offset raised portion 69 is offset to one side and extends forwardly of the base 67. A hole 71 in the raised portion and base is provided through which element 25 extends and is rigidly fastened as by molding. A base hole 72 extends through the center of the base. A bolt fastener 73 extends through the base hole 72 and a hole 74 in the boom and is fastened thereto by a nut 75 threading on the fastener 73 with a washer 76 on the fastener between the nut and boom. 
     A coaxial cable connector 77 of the BNC type (FIG. 2) fits on a plastic (PVC) cap 79 that is mounted on the end of the boom 22 and a coaxial cable 78 extends from the connector 77 to the cab of the airplane for electrically connecting the boom to equipment inside the airplane cab. The connector 77 is electrically connected by an internal wire inside the boom (not shown) that connects to the feed terminals 34a and 35a (FIG. 4) so that energy transmitted through antenna element 24 is coupled to suitable equipment inside the cab. 
     Each mounting device 81 has a generally channel shaped strut clamping bracket 82 having a base 83 and spaced side walls 84 and 85 (FIGS. 2 and 7) extending away from the opposite sides of the base 83 with a cross section that is shaped to conform to and fit around the portion of the cross section of the strut 13 on which it is mounted. The side walls 84 and 85 extend through an arc greater than 180 degrees so the bracket 82 has substantial frictional engagement with the strut. The bracket 82 has three sets of aligned slots 86, 87 and 88 in the top edges of the side walls 84 and 85. These sets of slots are spaced from one another along the side walls, one at each end and one at an intermediate position midway between the ends. The mounting device is made from a flat plate, preferably rigid metal, having a rectangular body with the sets of slots 86, 87 and 88 formed in opposite side edges and the arms 94 and 95 described hereafter extending out in opposite directions at opposite ends, the plate being bent or shaped into the channel-shaped form shown particularly in FIG. 11 with the side walls 84 and 85 being parallel to one another. 
     A fastening strap 91 (FIGS. 2, 3, 7 and 8) fits in each set of slots, extends around the clamping bracket 82 and strut 13 and a clamp 92 at the ends of the strap is tightened to draw the strap down to firmly clamp the clamping bracket 82 to the strut 13. The mounting device has a pair of parallel spaced arms 94 and 95 (FIGS. 2, 3 and 11) that are twisted about their longitudinal axis in opposite directions so that they face in opposite directions. The angle of twist of each arm 94 and 95 designated W is about 47 degrees. A rectangular cushion or pad 89 (FIGS. 3, 7 and 8) is shown fitted between the clamping bracket 82 and strut 13. 
     Each of arms 94 and 95 carries a boom clamping bracket 96 (FIGS. 9 and 11) which is a generally U-shaped member having a base 97 and a pair of parallel spaced side walls 98 and 99 extending away from opposite sides of the base 97 with a pair of aligned, semi-circular notches 101 (FIG. 9) in the top edge of each of the side walls to receive and conform to about one half of the cross section of the boom 22. The base 97 is fastened to the arm 95 by two, spaced side bolts 103 on each side of the center of the bracket 96. A nut 104 is threaded on each side bolt 103 with a washer 105 between the nut and base 97. A center bolt 107 extends through a hole 108 in the boom, and holes in the center of the base 97 and arm 95. A nut 109 threads on the center bolt with a washer 111 between the nut 109 and arm 95 so that each clamping bracket 96 is firmly clamped to the antenna boom 22. 
     The active elements 24, 25 and 26 are disposed substantially vertically or upright at an angle of 75 degrees to the horizontal. In particular, the arms are rotated along a longitudinal axis through a selected angle to compensate for the angle of the boom designated E (about 30 degrees) and positions the boom at a selected angle D (about 15 degrees) relative to the horizontal. This supports the antenna rearwardly of the strut on the aircraft. 
     The equation for the calculation of the separation distance designated S for the arms of the mounting device 81 relative to the angle and thickness parameters shown in FIG. 3 is as follows: ##EQU1## where, 
     T--thickness of strut 13 
     B--diameter of antenna boom 22 
     E--elevation angle of strut 13 
     D--depression angle of boom 22 
     S--separation distance for arms 94 and 95 
     Although the present invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made by way of example and that changes in details of structure may be made without departing from the spirit thereof.