Patent Publication Number: US-6342861-B1

Title: Loop antenna assembly

Description:
This application is a continuation of application Ser. No. 08/051,573 filed on Apr. 22, 1993 now abandoned, which is a continuation of application Ser. No. 07/343,862 filed on Apr. 26, 1989 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to the field of antennas, and more particularly to loop antenna assemblies intended for use in the high frequency and very high frequency portions of the electromagnetic spectrum. 
     2. Discussion of the Prior Art 
     The full wave loop antenna is generally recognized as one of the best conventional antennae for use in the high frequency and very high frequency portions of the electromagnetic spectrum for several reasons. First, the loop configuration tends to reduce fading on both transmission and reception. In addition, the full wave loop antenna provides enhanced directivity, gain, and “capture area” in comparison to other conventional antennae. Lastly, the full wave loop antenna is a “quiet” receiving antenna and displays a reduced level of “static” interference when compared with other conventional antennae. 
     The two major types of full-wave loop antennae in wide use today in the high frequency and very high frequency spectrums are the “cubical quad” and the “delta quad”. The cubical quad antenna is readily identified by the shape of its elements, which are generally square and vertically oriented. Similarly, the delta quad antenna may be identified by its elements, which are vertically oriented and generally in the shape of an equalateral triangle with one apex pointing toward the ground. The cubical quad normally uses support arms for the elements which join the mast at a single point, or a single boom which is fastened to the support arms, while the delta quad typically has all of the weight of the elements carried by a single boom. 
     Both the cubical quad and the delta quad antenna, however, display a number of disadvantageous characteristics. 
     First, due to the structural configuration of the antennae, they generally must be partially or completely assembled on the ground, making them quite difficult to install. For example, a typical cubical quad for the twenty meter amateur radio band has two square elements, each of which is approximately 17 feet on a side, which must be installed in a vertical orientation on a support structure such as a mast or a tower. Obviously, it is very difficult to assemble such a structure on the ground and then mount it on a support structure. 
     Second, the geometries of the cubical quad and delta quad make the antennae mechanically unstable, leaving them quite susceptible to dammage or destruction due to adverse weather conditions, such as high winds and snow and ice loading, when made from materials commensurate with their sizes, and light enough in weight to avoid the necessity of an oversized support structure. 
     Third, the cubical and delta quad antennae typically include a parasitic element (reflector), which is tuned to a resonant frequency which is two and one-half to three percent below the resonant frequency of the driven element with which it is designed to operate. Consequently, as the operating frequency of the antenna drops too far below the resonant frequency of the driven element, the parasitic element will approach self-resonance, substantially deteriorating the performance of the antenna. Also, the lengths of the sides of both the cubical quad and the delta quad elements are of equal or nearly equal length, thereby limiting the domain of reflector lengths at which co-incidence, or near co-incidence, of maximum foreward gain, maximum front-to-back ratio, and minimum VSWR (voltage standing-wave ratio) occur, both the lengths of the sides of the reflector elements and their total lengths being critical for efficient operation, the spacings between the driven element and the reflector element being adjusted to maximize the foreward gain on these antennae. The cubical quad and the delta quad are, therefore, limited to a relatively narrow range of operation frequencies below the resonant frequency of their driven elements, when using a reflector element to enhance their directional characteristics. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved full-wave loop antenna assembly having enhanced structural stability and effective directional characteristics over a wider range of frequencies than other antennas of its type. The antenna assembly is rotatable, self-supporting, may be made from commercially available materials, and is capable of supporting multiple driven and parasitic elements, in a variety of configurations, for multi-band operation. In addition, the antenna has semi-rigid element members which may be made from materials which are lighter in weight than those that would be used in the construction of “Yagi”-type antennae designed for use on the same frequency or frequencies, and can be installed by a single individual in much the same fashion as a “Yagi” type antenna. 
     In brief summary, the antenna assembly includes two essentially horizontal booms which are attached to an essentially vertical support structure. Conductive members, each of which forms a portion of either a driven or parasitic loop antenna element are attached to, and insulated from, the lower boom. A length of wire is attached to each member, near each end. A draw line, made of flexible insulating material, is fastened to each wire at, or nearly at, its center, fed through a bore in the upper boom, and through an eyelet mounted near the junction of the upper boom and the support structure for the booms, and run down next to the support structure to the lower boom, where it may be secured. Holding the draw lines in tension creates the desired geometric shape of the antenna elements. 
     Due to the configuration of the antenna assembly, the upper boom must always carry at least part of the weight of the antenna elements, as there is always some contact between the draw lines fastened to the wire portions of the largest antenna element installed on the structure and the upper boom, or some component which is fastened to the upper boom. For this reason, the upper boom will be referred to as the “load-bearing upper boom.” If sufficient tension is supplied to the aforementioned draw lines, all of the weight of the antenna elements may be removed from the lower boom. Releasing part of the tension on the draw lines allows part of the weight of the antenna elements to be carried by the lower boom, while still maintaining the desired geometric shape of the loop elements. Thus, the lower boom may, or may not be load-bearing for any particular loop element or group of loop elements, depending on the tension in the draw lines, the geometric configuration of the loop or loops, and the type of materials used for the loop element or elements. For this reason, the lower boom will be referred to as simply the “lower boom”, although, with the exception of the test run on the embodiment depicted in FIG. 6, the lower boom was load-bearing in all embodiments disclosed. 
     The combination of each wire with its associated conductive member represents a loop-type driven or parasitic antenna element. Additional driven or parasitic elements may be added, and located either concentrically with other elements, or at different positions along the booms. In addition, a parasitic (reflector) element having a physical length substantially greater than those used by conventional loop parasitic reflector elements may be used to increase the effective operating bandwidth of the antenna, the optimum reflector length being a function of the separation (spacing) between the driven element and its associated parasitic reflector, a property not present in other full-wave loop antennas of this type. On all embodiments tested, the loop antenna elements were approximately one full wavelength in length at the frequencies being tested. No lumped circuit components, such as inductors or capacitors, or any other devices, were employed to electrically alter the lengths of the antenna elements. For brevity, the antenna elements will be referred to in this disclosure as simply the “driven element” and the “parasitic element”, it being understood that all the antenna elements described in this disclosure are loop elements which are approximately one full electrical and physical wavelength in length at the frequencies being tested. 
     Tests run on all parasitic embodiments disclosed indicated an estimated foreward gain of approximately 5-8 db or higher, a front-to-back ratio of approximately 10-25 db or higher, and a front-to-side ratio of approximately 20-45 db or higher. The VSWR bandwidths of 2/1 or lower measured approximately 350 khz. or more on all embodiments disclosed, the antennas using a separate transmission line connected to the driven element indicating a considerably wider VSWR bandwidth of 2/1 or lower in most embodiments. The above and all references to “db” refers to decibles in relation to a theoretical isotropic source. The antennas disclosed where mounted above a rooftop, with the lower boom at an elevation of approximately thirty-five feet. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and further advantages of the invention may be better understood by referring to the following descriptions when considered in connection with the following drawings, in which: 
     FIG. 1 is a perspective view of an antenna assembly designed for use on a single frequency band, constructed in accordance with the preferred embodiment of the present invention. 
     FIG. 2 is a perspective view of an antenna assembly designed for use on three separate frequency bands. 
     FIG. 3 is an enlarged view of the driven element portion of the antenna assembly shown in FIG.  2 . 
     FIG. 4 is an enlarged view of the parasitic element portion of the antenna assembly shown in FIG.  2 . 
     FIG. 5 is a perspective view of an antenna assembly designed for use on three separate frequency bands, with the driven and parasitic elements for one band spaced wider apart than the driven and parasitic elements for the other two bands. 
     FIG. 6 is a perspective view of various combinations of antenna elements which may be used with the antenna assembly. 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS 
     In the following detailed descriptions of the illustrative embodiments, for enhanced clarity, certain components, such as “U” bolts, saddle brackets, eyelets, unused draw lines, etc., will not be shown. For simplicity and clarity, certain components shown in more than one drawing will be designated with the same reference numerals. 
     FIG. 1 shows a novel antenna assembly  42  which comprises a mast  2 , a load-bearing upper boom  4 , a lower boom  6 , a triangular-shaped driven element  8 , and a triangular-shaped parasitic element  10 . The load-bearing upper boom  4  is attached to the mast  2  by means of four “U” bolts  12   a,    12   b,    12   c,  and  12   d,  and four saddle brackets (not shown), which are used to secure them to a metal plate  16 . Similarly, the lower boom  6  is attached to the mast  2  by means of four “U” bolts  18   a,    18   b,    18   c,  and  18   d,  and four saddle brackets (not shown), used to secure them to a metal plate  22 . The metal plate  16  contains four eyelets (not shown) to which four guy wires  26   a,    26   b,    26   c,  and  26   d,  shown in phantom, are fastened. Two of the guy wires,  26   a  and  26   b,  are fastened to two turnbuckles  28   a  and  28   b  respectively, which are in turn fastened to eyelets  30   a  and  30   b  respectively, which are mounted on two saddle brackets  32   a  and  32   b  respectively, which are secured to the lower boom  6  by means of two “U” bolts  34   a  and  34   b  respectively. The outer two guy wires,  26   c  and  26   d  are fastened to two turnbuckles  28   c  and  28   d  respectively, which in turn are fastened to opposite ends of a strut  36 , which is mounted on metal plate  22 , and surrounds the mast  2 . Four lower guy wires,  38   a,    38   b,    38   c,  and  38   d,  are attached to a “floating” guy ring  40 , which is mounted on the mast  2  blow the lower boom  6 . The “floating” guy ring  40  allows the mast  2  to rotate freely so that a conventional antenna rotator  42  (partially shown) may be attached to the mast  2  blow the “floating” guy ring  40  to rotate the entire antenna assembly  42 . Insulators  44  are used to break up the electrical continuity of the lower guy wires  38   a,    38   b,    38   c,  and  38   d  in various places to prevent their resonance on any frequency intended for use by the antenna system installed on the structure. 
     The upper load-bearing boom  4  includes an outer sleeve  46  from which inner sleeves  48   a  and  48   b  extend. The inner sleeves  48   a  and  48   b  are held in place by means of two hose clamps  50   a  and  50   b  respectively. Two eyelets  52   a  and  52   b  are secured to two saddle brackets  54   a  and  54   b  respectively, which are secured to the upper boom  4  by two “U” bolts  56   a  and  56   b  respectively. 
     The mast  2  is in two sections, the upper portion fitting over an inner sleeve which is part of the lower section of the mast  2 . Two nut-and-bolt assemblies  58   a  and  58   b  secure the two sections together. 
     The semi-rigid portion of the driven element  8  includes an insulating plate  60  which is secured to the lower boom  6  by means of a “U” bolt  62  and a saddle bracket (not shown). Attached to the insulating plate  60  are two outer sleeves  66   a  and  66   b  by means of four nut-and-bolt assemblies  68   a,    68   b,    68   c  and  68   d  respectively. The outer sleeves  66   a  and  66   b  are separated from each other and do not make physical or electrical contact with each other. Two telescopic inner sleeves  70   a  and  70   b  are secured in the outboard ends of outer sleeves  66   a  and  66   b  respectively by means of two hose clamps  72   a  and  72   b  respectively. Outer sleeves  66   a  and  66   b,  in combination with inner sleeves  70   a  and  70   b  respectively, are refered to in this description as driven element member  74 . 
     The ends of a length of wire  76  are attached to and electrically connected to inner sleeves  70   a  and  70   b  respectively by means of two hose clamps  78   a  and  78   b  respectively. A non-conductive draw line  80   a  is attached to the wire  76  and fed upward through a bore  82   a  in inner sleeve  48   a.  The draw line  80   a  is fed through an eyelet  84   a  which is mounted on metal plate  16 , and runs down along the mast  2  where it is secured to an eyelet  86   a  which is mounted on metal plate  22 . The wire  76  and the driven element member  74  comprise the driven element  8 . 
     The parasitic element  10  includes an insulating plate  80  which is secured to the lower boom  6  by means of two “U” bolts  88   a  and  88   b  and two saddle brackets (not shown) respectively. Outer sleeves  92   a  and  92   b  are secured to insulating plate  86  by means of four nut-and-bolt assemblies  94   a,    94   b,    94   c,  and  94   d.  The inboard ends of outer sleeves  92   a  and  92   b  are spaced apart such that they are not in physical or electrical contact with each other. The ends of a single wire  96  are attached to nut-and-bolt assemblies  94   b  and  94   c  respectively, electrically connecting outer sleeves  92   a  and  92   b.  Telescopic inner sleeves  98   a  and  98   b  are secured in the outboard ends of outer sleeves  92   a  and  92   b  respectively by means of two hose clamps  100   a  and  100   b  respectively. Outer sleeves  92   a  and  92   b,  in combination with inner sleeves  98   a  and  98   b  respectively, and the single wire  96  are refered to in this description as parasitic element member  102 . The ends of a single piece of wire  104  are attached to and electrically connected to inner sleeves  98   a  and  98   b  respectively, by means of two hose clamps  99   a  and  99   b  respectively. A non-conductive draw line  80   b  is attached to the wire  104  and fed upwards through a bore  82   b  in inner sleeve  48   b.  The draw line  80   b  is fed through an eyelet  84   b,  which is mounted on metal plate  16 , and runs down along the mast  2  where it is secured to an eyelet  86   b  which is mounted on metal plate  22 . The wire  104  and the parasitic element member  102  comprise the parasitic element  10 . 
     Two draw lines  106   a  and  106   b,  (not shown in FIG. 1) are fed through two eyelets  52   a  and  52   b  respectively. The draw lines  106   a  and  106   b  are then fed through the two eyelets  84   a  and  84   b  respectively which are mounted on metal plate  16 , and run down along the mast  2  and secured to eyelets  86   a  and  86   b  respectively. The other ends of the draw lines  106   a  and  106   b  are secured to the lower boom  6 . One end of an additional draw line  106   c  (not shown in FIG. 1) is secured to eyelet  86   b,  runs upward along the mast  2 , through eyelet  84   b,  and then back down along the mast  2 , where the other end is secured to eyelet  86   b.  The draw lines  106   a,    106   b,  and  106   c  are not used in this embodiment of the invention. 
     As shown in FIG. 1, the novel antenna assembly of the present invention operates to distribute the weight of the driven and parasitic elements  8  and  10  respectively, among the load-bearing upper boom  4 , the lower boom  6 , and the tension in the draw lines  80   a  and  80   b  respectively running between the top of bores  82   a  and  82   b  respectively and the eyelets  86   a  and  86   b  respectively. The tension in the draw lines  80   a  and  80   b  which is transfered to the wires  76  and  104  respectively, tends to reduce any significant downward movement of the driven and parasitic element members  74  and  102  respectively, as well as the lower boom  6 , such as would be caused by ice and snow loading. The use of draw lines  80   a  and  80   b,  as well as the wires  76  and  104  respectively, provide a certain measure of flexibility and resiliancy to the driven element  8  and the parasitic element  10 , partially accounting for the durability of this antenna assembly. Also, as the driven and parasitic element members  74  and  102  respectively are moved laterally by the wind, their ends are pulled upwards by the wire portions  76  and  104  of the driven, and parasitic elements  8  and  10  respectively, thereby reducing the liklihood of structural failure of the driven and parasitic element members  74  and  102  respectively. 
     Most of the aforementioned advantages could also be achieved by securing draw lines  80   a  and  80   b  to the inner sleeves  48   a  and  48   b  respectively. 
     Some or all of the advantages of this novel support arrangement may be obtained, even though booms or elements having different orientations or shapes are used, so long as the booms are arranged in a particular way with respect to the elements. More specifically, since any given loop element, (whether driven or parasitic) represents some particular closed geometric shape, or some nearly closed geometric shape which may be closed by the shortest geometric means possible, which has a centroid, it is possible to locate the booms at different elevations on the support structure in such a way that the centroid of the loop element or elements lies at an elevation which falls between the elevation of the junction of the upper load-bearing boom and the support structure and the elevation of the junction of the lower boom and the support structure on which the booms are mounted, in such a way that at least part of the weight load created by the loop element or elements may be distributed between the upper load-bearing boom and the lower boom, while maintaining the desired geometric configuration of the loop element or elements. (Obviously, the driven element member  74  and the parasitic element member  102  may be mounted above or below the lower boom  6 .) This characteristic may be seen in the embodiment depicted in FIG. 1, where the centroids of the loops lie at an elevation which lies between the elevation of the junction of the upper load-bearing boom  4  and the mast  2 , and the junction of the lower boom  6  and the mast  2 , and at least part of the weight of the loop elements  8  and  10  respectively may be distributed between the upper load-bearing boom  4  and the lower boom  6 , while maintaining the desired geometric configuration of the loop driven element  8  and the loop parasitic element  10 . Also, as may be seen in FIG. 1, and in all subsequent embodiments disclosed, the support structure for the booms does not lie in, or intersect, any plane substantially contained by any loop element, nor does it directly support any loop element. As may be sen in FIG. 1, each loop is contacted twice, at some distance from the support structure for the booms, at essentially two different elevations, for the maintenance of its geometric shape, support, and stability, each loop having a semi-rigid member comprising one side of the loop. The center of gravity of each loop element lies not only below a point which falls halfway between the uppermost extension of the loop element and the lowermost extension of the loop element, but considerably below the centroid of the loop element, a condition which is created by the weights of the driven element member  74  and the parasitic element member  102  respectively. 
     An antenna assembly, similar to the one depicted in FIG. 1, was constructed and tested. It should be understood that the specific dimensions and test results discussed below are representative of one particular embodiment of the present invention, but should not be constructed to limit or restrict the true scope of the invention. In addition, as one having ordinary skill in the art will recognize, the VSWR readings and observed directional characteristics of most antennae will vary somewhat in response to changes in a number of different factors, including the height of the antenna above ground (electrical), the proximity of surrounding objects, the method of matching or coupling (or connecting) the antenna to its transmission line, etc. It is also important to note that at the frequencies being tested, a considerable number of factors, such as the conditions of propogation, the polarization of the signals, the incident angle of the incoming or transmitted signal, the polarization of other antennas being used for testing or comparison, will affect the readings and measurements being taken, such that a significant number of tests under varying conditions of propagation are necessary to determine with a reasonable degree of accuracy the true performance of the antenna being tested. 
     The antenna assembly which was constructed and tested included an upper load-bearing boom that was approximately 13 feet 6 inches long, including the inner sleeve, and was constructed from a re-enforced one inch aluminum tube. The inner sleeves, made of wooden dowels, were initially intended to prevent electromagnetic coupling between the antenna element wires and the load-bearing upper boom, but subsequent testing on other embodiments has shown the wooden dowels to be unnecessary on all embodiments tested. The lower boom which was load-bearing in the above and, with the exception of the test run on the embodiment disclosed in connection with FIG. 6, in all embodiments disclosed, was approximately 13 feet 6 inches long, and was constructed from a one and one-quarter inch, 16 gage, steel tube. The driven and parasitic elements were separated apart by a distance of approximately 12 feet 11 inches, as measured along the lower boom. 
     The upper load-bearing boom and the lower boom were spaced apart on the support structure by a vertical distance of approximately 11 feet 11 inches (center to center). This particular distance was chosen as a result of the particular structural materials on hand or readily available, and as a conscious effort to avoid any lengths between the loop elements, either for the mast or for the upper guy wires, which would represent a one-quarter wavelength on any of the frequencies contemplated being tested. The mast was in two sections. The upper portion of the mast, approximately 7 feet 10 inches long to the upper load-bearing boom, was constructed from one and one-quarter inch aluminum tubing, fit over a sleeve on the lower portion of the mast, which was constructed from a one and one-quarter inch 16 gage steel tube, re-enforced on the inside with a one-inch steel pipe, extending from the bottom of the mast to just above the junction of the lower boom and the mast. The aluminum portion of the mast was used to reduce the weight in the upper portion of the mast, but since the aluminum was not of the structural variety, guying for the upper mast was deemed necessary. As will be obvious to one skilled in the art, the use of suitable materials for the mast, (e.g. 60-61 T6 structural aluminum tubing of suitable diameter and wall thickness) will make the use of the upper guy wires and the internal re-enforcement of the mast unnecessary for the above and greater separations between the upper load-bearing boom and the lower boom, as this is regularly done in the “stacking” of large antenna arrays. Also, suitable structural material (60-61 T6 aluminum, e.g.) can be used for the upper load-bearing boom and the lower boom as well. 
     The upper guy wires  38   a,    38   b,    38   c,  and  38   d  were used in this installation for stability of the antenna assembly&#39;s base support, since the entire assembly was mounted on a chimney, using five chimney mounting brackets. A suitable mounting base for the antenna assembly would make this unnecessary. 
     The use of two “U” bolts and saddle brackets to secure the insulating plate  86  to the lower boom  6  was done to ensure the stability of the junction between the parasitic element member  102  and the lower boom  6 . Obviously, only one “U” bolt and saddle bracket are needed for this junction, since a single “U” bolt saddle bracket were successfully used to fasten the insulating plate  60  to the lower boom  6  in securing the driven element member  74  to the lower boom  6 . 
     The insulating plates  60  and  86  were constructed from bakelite composition material. They were used as a convenience in coupling the transmission line  85  to the driven element  8 , and for convenience in making various adjustments to the length of the parasitic element  10 . This could easily be done by varying the length of the wire  96  which was electrically connected between the outer sleeves  92   a  and  92   b.  In the embodiment depicted in FIG. 1, the parasitic element member  10  was intentionally electrically connected to the lower boom  6  as a test, with no noticable changes in the performance of the antenna. As will be obvious to one skilled in the art, the driven element  8  may also be electrically connected to the lower boom  6 , and a variety of different techniques, (a gamma match, e.g.) may be successfully used to couple the transmission line to the driven element  8 . 
     The outer and inner sleeves on the driven and parasitic element members  74  and  102  were made of ⅞ inch and ¾ inch, 0.058 inch wall 60-61 T6 structural aluminum tubing respectively. This is a conductive material standardly used in “Yagi” type antenna built for the frequencies tested. The metal plates  16  and  22  were made of ⅛ inch aluminum. The strut  36  was made from two, one-half inch threaded steel rods, each  36  inches long, joined near their ends with two steel plates which were secured by four sets of two nuts, threaded onto the steel rods. The wires  76  and  104  were made of stranded aluminum guy wire. The flexible insulating material called “draw lines” in the above and all embodiments was made of nylon string. The nut-and-bolt assemblies,  68   a,    68   b,    68   c,    68   d,    88   a,    88   b,    88   c,  and  88   d,  as well as all nut-and-bolt assemblies used on this and all other embodiments were made of brass or stainless steel. 
     It is well known in the art that the length of the electrical conductor or conductors comprising an antenna element operating at high frequencies substantially determines the resonant frequency of the antenna element, the relationship between element length and resonant frequency being essentially linear. Accordingly, the lengths of the driven and parasitic element loops in the above and all other embodiments disclosed were adjusted for maximum co-incidence of minimum VSWR (voltage standing wave ratio), maximum estimated foreward gain, maximum front-to-back ratio, and maximum front-to-side ratio. This shall be referred to in this disclosure as “optimum” tuning for the antenna or antennas under discussion. When turned to optimum tuning, the driven element member  74  was approximately 30 feet 6 inches long. The wire  76  was approximately 39 feet 8 inches long. When combined with the division in the coaxial cable connected to nut-and-bolt assemblies  68   b  and  68   c  respectively, the total length of the loop driven element  8  was approximately 70 feet 4 inches. 
     The parasitic element member  102  was approximately 35 feet long, including the wire  96 . The wire  104  was approximately 42 feet long, making the total length of the loop parasitic element  10 , used as a reflector, approximately 77 feet long. A ¼ electrical wavelength of 70 ohm coaxial cable  85  was used as an impedence matching device between the driven element  74  and the 50 ohm coaxial cable which was coupled (connected) to the two-way radio equipment used for testing this and all embodiments listed in this disclosure. As will be obvious to one skilled in the art, other types of transmission lines, ballanced or unballanced, can be used successfully with the above and all other embodiments disclosed. The VSWR at the center (resonant) frequency of the antenna measured approximately 1.1/1 at 14.2 MHz. Extrapolations from measurements taken at various frequencies in the 20 meter amateur radio band indicated a projected bandwidth of more than 800 khz., having a VSWR of 2/1 or lower. Tests run on the antenna indicated an estimated foreward gain of approximately 5-8 db or higher, a front-to-back ratio of approximately 15-25 db or higher, and a front-to-side ratio of approximately 20-45 db or higher. Decreasing the spacing between the the driven element  8  and the parasitic element  10 , without changing the lengths of the antenna elements, from approximately 12 feet 11 inches to approximately 8 feet, yielded a broader foreward gain pattern, and a somewhat increased front-to-back ratio. Later tests indicate that this was the result of the reflector being too long for optimum performance at that spacing. 
     The total length of the driven element  8  was approximately one full wavelength at 14.2 Mhz. The reflector element  10  was measured to be approximately 9.4 percent longer than the length of the driven element  8 . This is in sharp contrast to conventional parasitic reflectors used on antennas of this type, which are typically two and one-half to three percent longer than the driven element with which they are designed to operate. 
     The optimum length of the reflector element was determined by the use of a remotely-controlled, motor driven, reversable stub shorting bar, substituted for wire  46 , and allowing for continuous variance in the length of the reflector element while running tests in position at the radio equipment. This device was designed and constructed because of the great difficulty encountered in achieving any appreciable directivity for the antenna through numerous adjustments in the reflector length corresponding to the reflector length having its proper adjustment length approximately two and one-half to three percent longer than the length of the driven element, which is the length that typically corresponds to the optimum reflector length for antennas of this type. In addition, when the difference between the reflector length and that of the driven element was varied between approximately 7 and 11 percent, by varying the reflector length, very little deviation from optimum performance was noted, indicating that the reflector length in the antenna is not nearly as critical as those used in conventional antennas of this type. This feature was also confirmed by measurements taken over a wide range of frequencies on both transmitted and received signals on other embodiments of the present invention using additional frequency bands, and partially accounts for the improved directional characteristics over a wider range of frequencies than those achieved by conventional antennas of this type. 
     Obviously, other proportions of the particular geometric shape used, as well as other geometric shapes, such as squares, rectangles, trapezoids, or other symetrical or non-symetrical shapes, may be chosen to meet the desired structural and operational parameters of the antenna, and this and the subsequent embodiments of the present invention are offered merely as examples of the present invention. Also, the unique operational parameters disclosed may be utilized by installing the desired antenna elements on a variety of structures, rotatable and non-rotatable, such as fixed supporting members, using a variety of conductive materials for the antenna elements. 
     The above and all embodiments disclosed were tested at various transmitting power levels, ranging from less than 100 watts PEP to greater than 1000 watts PEP, with no adverse effects at the higher power levels. 
     As will be obvious to one skilled in the art, various techniques, such as the use of inductances, capacitances, coupling stubs, etc., may be used to electrically alter the lengths and dimensions of the antenna elements. Also, the loops may be physically or electrically open, by the use of “traps”, e.g., to allow for operation on different or multiple frequency bands. Other devices, such as a balun transformer, may be used in place of the ¼ wave matching section of 70 ohm coaxial cable used in the above and other embodiments disclosed. 
     The embodiment of the antenna assembly disclosed above, as well as the other embodiments disclosed may be installed by a single individual positioned in one location, such as on a rooftop or the top of an antenna tower according to the following procedure. First, the upper load-bearing boom  4  is attached to the mast  2 . The various draw lines are installed in their proper bores and eyelets, and both ends of all draw lines are temporarily secured at a point on the mast  2  near its bottom end. The upper guy wires  26   a,    26   b,    26   c,  and  26   d  are secured to their respective eyelets on the metal plate  16 , and temporarily secured to the mast  2  near its bottom end. The assembly is raised and installed in the base support for the antenna assembly. 
     The metal plate  22  is installed on the mast  2 , and upper guys  26   c  and  26   d  are secured to the strut  36 . The lower boom  6  is fed through “U” bolts  18   c  and  18   d,  which are not tightened. The lower boom  6  may then be slid back and forth to allow for installation of the driven element  8  and the coaxial cable  85  on the lower boom  6 . The draw line  80   a  is fastened to wire  76  and the lower boom is slid over to allow for the installation of the parasitic element  10 . Draw line  80   b  is fastened to wire  104 , and the lower boom is slid to its desired operating position and secured. Eyelets  28   a  and  28   b  are installed on the lower boom  6 , each about 18 inches from the mast  2 , and upper guy lines  26   a  and  26   b  are secured to eyelets  28   a  and  28   b  respectively. The draw lines  80   a  and  80   b  are put in tension and secured. Thus, in addition to providing tension for maintaining the elements in their desired geometric configuration, draw lines  80   a  and  80   b,  as well as the other draw lines used on the other embodiments disclosed, aid significantly in the installation of the antenna assembly. Obviously, other means, such as pulleys, can be used to raise and lower the wires  76  and  104 , as well as the wire portions of the other embodiments disclosed. 
     To further examine the potential of the antenna system, several other embodiments of the present invention were constructed and tested. In the embodiment depicted in FIG. 2,  125 , for clarity certain components (e.g. “U” bolts, saddle brackets) are omitted from FIG. 2, and shown in the enlarged views of the composite antenna elements in FIG.  3  and FIG.  4 . Other components are shown in phantom. 
     In the embodiment depicted in FIG. 2, two additional wire antenna driven elements  124  and  126  respectively, were suspended inside the driven element  8  depicted in FIG. 1, and two additional wire parasitic elements,  177  and  179  respectively, were suspended inside the parasitic element  10  depicted in FIG. 1, all wires being disposed essentially concentrically. 
     Referring to FIG. 2, an insulating plate  116 , was mounted on lower boom  6  by fastening it to a saddle bracket ( 118  of FIG. 3) which was secured to lower boom  6  with a “U” bolt ( 120  FIG.  3 ). four nut-and-bolt assemblies  122   a,    122   b,    122   c,  and  122   d  were installed on the insulating plate  116 . The ends of a separate driven element wire  124  were secured to nut-and-bolt assemblies  122   a  and  122   b  respectively. The ends of a separate driven element wire  120  were secured to nut-and-bolt assemblies  122   c  and  122   d  respectively. Three lengths of flexible insulating line,  128 ,  130 , and  132  respectively, were used to fasten each of the three corners of wire driven elements  124  and  126  respectively to the three corners of the driven element  8 . The driven element wires  124  and  126  comprise the driven elements  124  and  126  respectively. Driven elements  8 ,  124 , and  126  comprise composite driven element  172 . 
     In the same fashion, insulating plate  134  was installed on the lower boom  6  by fastening it to a saddle bracket ( 136 FIG. 4) and securing it to the lower boom  6  with a “U” bolt ( 138  FIG.  4 ). Two nut-and-bolt assemblies  140   a  and  140   b  respectively, were installed on the insulating plate  134 . A flexible insulating line  142  was fastened to the top apex of parasitic element  10  and fastened to a separate insulating plate  146  through a bore  147  near the top of insulating plate  146 . Two nut-and-bolt assemblies  140   c  and  140   d  respectively were installed on the insulating plate  146 . The ends of a length of wire  156  were fastened to nut-and-bolt assemblies  140   a  and  140   b  respectively. The ends of a separate length of wire  158  were secured to nut-and-bolt assemblies  140   c  and  140   d  respectively. One end of a length of flexible insulating line  150  was secured through a bore  151  near the top of insulating plate  134 . The other end of the flexible insulating line  150  was secured through a bore  152  near the bottom of insulating plate  146 . The wires  156  and  158  were secured essentially concentrically inside parasitic element  10  by means of three flexible insulating lines  164 ,  142 , and  166 . The ends of a single piece of wire  168  were secured to nut-and-bolt assemblies  140   c  and  140   d  respectively. The wire  156 , in combination with wire  170  comprise parasitic element  177 . The wire  158  in combination with wire  168  comprise parasitic element  179 . Driven elements  124 ,  126 , and  8  comprise composite driven element  172 . Parasitic elements  177 ,  179 , and  10  comprise composite parasitic element  181 . Driven elements wire  126  and parasitic element wire  166  were made of 16 gate copperclad stranded steel wire. Driven element wire  124  and parasitic element wire  158  were made of 16 gage stranded copper wire. The various “jumper” wires used in this and other embodiments disclosed were made of solid copper wire in various gages ranging from 14 to 20 gage. 
     Driven element wire  76  was fastened to draw lines  106   a  and  80   a.  Parasitic element wire  104  was fastened to draw lines  106   b  and  106   c.  Draw lines  106   a,    106   b,  and  106   c  were put in tension. Draw lines  106   a  and  80   a  were secured to eyelet  86   a.  Draw lines  106   b  and  106   c  were secured to eyelet  86   b.  The separation between composite driven element  172  and composite parasitic element  181  was approximately 5 feet 8 inches as measured along the lower boom. The end of draw line  80   b  was secured near the outboard end of lower boom  6  with all the tension on the draw line removed. 
     A 50 ohm coaxial transmission line  184  was connected to nut-and-bolt assemblies  68   b  and  68   c.  The ends of a single wire  178  were fastened is nut-and-bolt assembly  68   b  and  122   d  respectively. The ends of another single piece of wire  180  were fastened to nut-and-bolt assembly  68   c  and  122   c  respectively and positioned in such a way to avoid any significant electromagnetic coupling between them. One end of a quarter electrical wavelength of 70 ohm coaxial cable  102 , used as an impedance transformer, was connected to nut-and-bolt assemblies  122   a  and  122   b.  The other end of coaxial cable  182  was connected directly to a 50 ohm coaxial transmission line (not shown). The insulating plates  116 ,  134 , and  146  were made of plexiglass. 
     The three separate driven elements  8 ,  126 , and  124 , and the three separate parasitic elements  10 ,  177 , and  179  were tuned by adjusting their respective lengths for optimum performance in the 20, 15, and 10 meter amateur radio bands respectively. The 20 and 10 meter antennas demonstrated a VSWR bandwidth of 2/1 or less of approximately 350 khz. or more. The 10 meter antenna, connected to a separate feedline, demonstrated a VSWR bandwidth of 2/1 or lower of more than 800 khz. The directional characteristics of all the antennas fell within the parameters as described earlier in this disclosure. 
     When tuned for optimum performance at this element spacing, the reflectors were approximately 5.2 per cent longer than the driven element on 20 meters, 6.2 per cent longer than the driven element on 15 meters, and 8.6 per cent longer than the driven element on 10 meters, respectively. This demonstrates a unique feature for an antenna of this type, which is that the optimum reflector length for any particular antenna increases as the spacing between the driven element and its associated parasitic reflector increases, which means that optimum performance for any particular antenna may be achieved at a variety of element spacings, the lengths of the driven element and its associated parasitic reflector being selected to achieve the desired operating parameters of the antenna at the desired spacing between the driven element and its associated parasitic reflector. It also demonstrates that multiple, substantially concentric elements may be used effectively on the antenna system, while taking advantage of the unique structural and electrical properties of the antenna system. As will be obvious to one skilled in the art, further increasing the spacing between the driven element(s) and their associated parasitic reflectors will further increase the difference in length between the driven element and that of its associated parasitic reflector, when the driven element and its associated parasitic reflector are tuned for optimum performance at that spacing. Connecting the single wire  178  between nut-and-bolt assemblies  88   b  and  122   c,  and connecting the single wire  180  between nut-and-bolt assemblies  88   c  and  122   d  necessitated lengthening the 15 meter driven element by approximately 12 inches in order to return it to the resonant frequency to which it had previously been set. 
     Removing coaxial cable  182  from nut-and-bolt assemblies  122   a  and  122   b,  and connecting the ends of a single piece of wire to nut-and-bolt assemblies  122   b  and  122   d  respectively, and connecting the ends of another single piece of wire to nut-and-bolt assemblies  122   a  and  122   c  respectively, thus having all three driven elements fed by the single transmission line, coaxial cable  164 , resulted in a considerable reduction i VSWR bandwidth of 2/1 or lower on 10 meters, and demonstrated some loss of circuitivity on 10 meters, although all operational parameters remained within the parameters as described earlier in this disclosure. As will be obvious to one skilled in the art, various matching and coupling devices, such as a balun transformer, may be used to improve the VSWR bandwidth and directional characteristics of the antennas in this arrangement. 
     This antenna assembly was tested for mechanical stability and durability with respect to adverse weather conditions. The antenna assembly was subjected to winter weather conditions such as those found in the northeastern United States, including repeated instances of high winds combined with heavy snow and ice loading. The antenna assembly was observed to remain quite stable and operable throughout all such weather conditions, exhibiting considerably more stability and durability then other antennas of its type. Close examination showed no noticeable dammage to tha antenna assembly had occurred as a result of the exposure. The departure from symmetry of the various antenna elements caused by these conditions had no appreciable effect on the operation of the antenna, nor did the variations in symmetry introduced during tuning and testing of the various embodiments described in this disclosure. 
     Since using a single transmission line for each band showed improved VSWH bandwidths for the bands used, the antenna system was then tasted using three separate transmission lines, one connected to each of the three antennas being tested, to determine the full capabilities of this embodiment. 
     Single wires  178  and  100  were removed from the antenna, and a separate 50 ohm coaxial transmission line was connected to nut-and-bolt assemblies  122   c  and  122   d,  there being now a separate transmission line connected to each of the three driven antenna elements on the antenna assembly. Elements were retuned for optimal performance. This yielded a considerably wider VSWR bandwidth of 2/1 or lower an 15 meters, and increased the optimum parasitic reflector length to approximately 7.0 per cent longer than that of the 15 meter driven element, and the optimum parasitic reflector length of the 10 meter parasitic reflector to approximately 9.1 per cent longer than that of the 10 meter driven element. No significant changes in directional charactistics of the antennas were noted, when compared with the embodiment listed above which used two separate transmission lines to feed the three driven elements. 
     By utilizing draw line  106   a  in combination withdraw line  80   a,  and draw line  106   b  in combination with draw line  106   c,  the antenna elements were than spaced at approximately 7 feet 10 inches, and subsequently at approximately 8 feet. The lengths of the driven and parasitic elements were left intentionally the same. The VSWR bandwidth of 2/1 or lower on 20 meters improved substantially, and the VSWR bandwidths of 2/1 or lower on 15 and 10 meters respectively remained approximately the same. Again, the directional characteristics of the antenna remained within the previously defined parameters, further demonstrating the wide effective range of variance from optimum reflector length. 
     Due to the unique operational properties of the embodiments of the antennas tested, it was not clear whether an additional antenna, or antennas, could be installed on the structure between the driven and parasitic elements depicted in FIG. 1, without causing significant interactive deterioration in the performance of one or more antennas installed on the structure. It was also not clear if mounting the lower horizontal portions of the internally mounted antenna elements in the same plane described by the lower horizontal portions of the antenna elements depicted in FIG. 1 would contribute to any deterioration in performance, as full-wave antennas of this type which utilize separate antennas for different frequency bands mounted on the same structure at different spacings either have the loop elements arranged so that the centroids of the various loop elements of different sizes lie approximately in a straight line, having the lower horizontal portions of the elements for different frequency bands at different elevations, (as in the “cubical quad”, e.g.), or the upper horizontal portions of the elements for different frequency bands lie at different elevations, (as in the “delta” quad, e.g.). 
     It was also deemed necessary to test the assembly for the additional weight and wind loads introduced by the additional antenna elements. 
     To examine these questions, an embodiment of the antenna system  211 , as depicted in FIG. 5 was constructed and tested. The 20 meter elements  8  and  10  respectively were returned to the spacings and positions, and their lengths adjusted as depicted in the embodiment shown in FIG. 1. A 15 meter driven element  192 , comprising element member  205  and wire  206 , and a parasitic element  194 , comprising element member  207  and wire  208 , were constructed in approximately the same fashion, and is approximately the same geometric proportions as the driven element  8  and the parasitic element  10  depicted in connection with the embodiment which was shown in FIG. 1, and installed on the lower boom  6 , using draw lines  106   a,  and  108   b  and  106   c  in combination, to space the elements approximately 5 feet 9 inches apart, the 15 meter parasitic element being secured to the lower boom  6  with a single “U” bolt  202  and saddle bracket (not shown). The 15 meter driven element  192  was secured to the lower boom  6  with a single “U” bolt  201  and saddle bracket (not shown), and was fad directly with a 50 ohm coaxial transmission line  195 . To further test the domain of effective parasitic frequency deviation from the optimum, the length of the parasitic element (reflector)  194  was set at approximately 8 per cent longer then the length of the driven element  192 . 
     The VSWR bandwidth of 2/1 or lower was projected (extrapolated) to be more than 800 khz. on 15 meters, and the VSWR bandwidth of the 20 meter antenna of 2/1 or lower remained approximately as described in connection with the embodiment depicted in FIG. 1, as did its directional characteristics. The 15 meter antenna supplied similar directional characteristics to the 20 meter antenna, well within the parameters as described in the connection with the other embodiments disclosed in this application. There was no noticable interactive interference detracting from the performance of the 20 meter antenna caused by the introduction of the 15 meter antenna to the system. No difficulties were observed as a result of the additional weight and wind loads introduced by the driven element  192  and the parasitic element  194 . 
     As a further test, the 10 meter driven element  124  and the 10 meter parasitic element  158 , both shown in phantom, which were described in connection with the embodiment depicted in FIG. 2, were suspended, essentially concentrically, inside the 15 meter driven element  192  and the 15 meter parasitic element  194  respectively, both elements being insulated from the lower boom  6 , and mounted in the same fashion as they were in connection with the embodiment described and shown in FIG. 2. A ¼ electrical wavelength of 70 ohm coaxial cable  196  was used to couple the 10 meter driven element  124  to its 50 ohm transmission line, as was described in connection with the embodiment described in FIG.  2 . Although alight shifts in resonant frequency were noted on the 15 and 20 meter antennas, the VSWR bandwidth of 2/1 or lower remained substantially the same on both antennas. The VSWR bandwidth of 2/1 or lower on the 10 meter band was measured to be more than 900 khz. The directional characteristics remained within the parameters described in connection with the other embodiments disclosed. 
     In the embodiment depicted in FIG. 6,  215 , the 15 meter antenna as disclosed in connection with the embodiment depicted in FIG. 5 was installed alone on the structure with the same element spacing as disclosed in connection with FIG. 5, with the driven element member  205  and the parasitic element member  207  respectively installed on the upper side of the lower boom  6 . The ends of the draw lines  80   a  and  80   b  respectively were secured near the ends of the lower boom  6  with all tension removed. Removing “U” bolts  201  and  202  respectively, and supplying sufficient tension to draw lines  106   a,  and  106   b  in combination with draw line  106   c  respectively, it was possible to lift the driven element  192  and the parasitic element  194  completely up off the lower boom  6 . Although there was some upward bending of the element members  205  and  207  respectively, this demonstrated that the lower boom does not need to be load-bearing while maintaining the desired geometric shape of the loop elements  192  and  194  respectively. (Obviously, the degree of upward bending, or “sag” of the semi-rigid element members on this and all other embodiments disclosed is a function of the geometries of the loop elements, the materials of which they are constructed, etc.). Re-securing the driven element member  205  and the parasitic element member  207  respectively to the lower boom  6 , and testing the VSWR on the antenna, it was observed that the resonant frequency of the antenna had dropped from approximately 21.300 Mhz. to approximately 21.000 Mhz., a significant shift in frequency. The VSWR at resonance was almost identical at both frequencies. This is in sharp contrast to comparisons taken with the 20 meter antenna mounted alone, and with the 15 meter antenna mounted on the same boom, as in FIG. 5, since on the 20 meter antenna, the resonant frequency remained approximately the same at approximately 14.2 Mhz., and the VSWR was only slightly higher when the two antennas were mounted on the structure. 
     This indicates, however, that although the internally mounted antenna did not interfere with the externally mounted antenna, the reverse was not the case, although, as stated above, no significant deterioration in performance was noted in the 15 meter antenna, when mounted on the same booms with the 20 meter antenna, and the 15 meter antenna did not perform noticably better when mounted alone on the structure. It may, however, be necessary to “touch up” the tuning of some antennas when other wider-spaced antennas are added to the structure. 
     The lengths of the driven element  192  and the parasitic element  194  (shown in phantom) were then adjusted to make the parasitic element  194  act as a full-wave loop director element, rather than a reflector. When the elements were tuned for optimum performance, the length of the parasitic director corresponded closely to approximately one full wavelength at the resonant frequency of the antenna at approximately 21.3 Mhz. The length of the driven element  192  corresponded to a frequency which was approximately 7.5 per cent lower than that of the parasitic director, or, stated conversely, the length of the parasitic director corresponded to a frequency which was approximately 7 per cent higher than that of the driven element. The VSWR bandwidth of 2/1 or lower was approximately the same as, and tests indicate that the directional charactistics corresponded quite closely to the performance of the antenna when the parasitic element  194  was tuned as a reflector, the directional pattern being reversed approximately 180 degrees. 
     Removing parasitic element  194  from the structure, and using driven element  192  alone on the structure, with a ¼ electrical wavelength of 70 ohm coaxial transmission line (not shown) used as an impedance matching device between the 50 ohm coaxial transmission line  195  and the driven element  192 , the antenna was tested and compared with a reference half-wave dipole at approximately the same elevation. The VSWR bandwidth of 2/1 or lower was somewhat less than when the antenna was used with a parasitic element, and the minimum VSWR was somewhat higher, due to the increased feedpoint impedance of the driven element used alone. The antenna displayed slightly better directional characteristics and slightly improved gain when compared with the reference dipole. 
     On all embodiments disclosed, the antennas were tuned for optimum performances near the centers of the 20, 15, and 10 meter amateur radio frequency bands. In the tests run on all parasitic embodiments disclosed, a good ballance between maximum foreward gain, maximum front-to-back ratio, maximum front-to-side ratio, and minimum VSWR was achieved. As is common to parasitic antennas, changing the resonant frequency of either a driven element or its associated parasitic element, will effect the optimum tuning of the other element with which it is operating. Also, when concentric elements were added to existing elements, both driven and parasitic, a certain ammount of interaction occurred, necessitating re-adjustment of the various element lengths to re-establish optimum tuning. 
     The stated correlations between parasitic element lengths and their resonant frequencies were based on the standard formula, velocity equals frequency times wavelength, and comparative length measurements of each parasitic element and its associated driven element. Some variations in this correlation may have occurred due to variations in geometric shape and the presence of other antenna elements installed on the structure. The term “a ¼ electrical wavelength of 70 ohm coaxial cable” refers to an impedance matching section which was approximately ¼ electrical wavelengths long at the desired (center) operating frequency of the antenna being tested. The abbreviations khz., and Mhz. refer to kilohertz and Megahertz respectively. 
     As will be obvious to one skilled in the art, the unique operational parameters disclosed need not be confined to any particular frequency, or band of frequencies. When used on frequencies in the upper regions of the Very high frequency portion of the electromagnetic spectrum, (above 150 Mhz., e.g.) and frequencies in the Ultra high frequency portion of the electromagnetic spectrum and above, certain considerations may need to be given to the physical properties of the antenna elements, such as the element diameter/element length ratio, the resistance of the conductive members comprising the elements, etc., as well as the usual types of feeding, coupling, and matching techniques that are employed at these frequencies. 
     Although various materials have been listed in the embodiments disclosed, as will be obvious to one skilled in the art, other suitable materials may be substituted for any or all of the materials listed. For example, the 60-61 structural aluminum tubing used for the semi-regid element members may be replaced with standard aluminum tubing of suitable strength. The various types of wire used in the antenna elements and for the upper guy wires may be interchanged using solid or stranded wire of suitable strength and conductivity, or they may be replaced with other conductive wires, such as steel or various alloys. The bakelite insulators may be replaced with textalite, or with a metal plate using stand-off type insulators. The plexiglass plates may also be replaced with textalite or other suitable insulating materials. The nylon line may be replaced with cotton twine of suitable strength, or a variety of synthetic plastic-type insulating lines. The various hose clamps may be replaced with nut-and-bolt assemblies. The aluminum plates may be replaced with steel plates. The wooden dowels may be replaced with PVC tubing. The upper guy wires may be replaced with aluminum guy wire. The various jumper wires, used to join the lower sections of the various parasitic elements, which were made from various types of copper wire, may be made from aluminum wire. The various nut-and-bolt assemblies used in all embodiments disclosed, may be made of other electrically conductive materials, such as steel, e.g. The wire portions of the various elements could be replaced with conductive tubing, although in some instances this might detract from the flexibility and durability of the antenna assembly. Some portions of the nylon string could be replaced with semi-rigid insulating material, such as PVC. 
     Obviously, a single draw line could be used in place of draw lines  106   a  and  80   a,  and  106   b  and  106   c  respectively, in the embodiment described in connection with FIG. 2, with an eyelet suitably placed above the composite driven element  172  and the composite parasitic element  181  respectively, or one continuous draw line could be used to raise and lower two or more wire portions of loop elements of the types disclosed. The novel draw line arrangements disclosed may be used in many ways to allow for continuous variations in the spacings between two or more antenna elements installed on the antenna assembly. With the correct placement of eyelets on the upper load-bearing boom, the elements may be placed at, or nearly at, the ends of the booms in all embodiments disclosed, the boom lengths being adjusted to accomodate the desired spacings for the elements. Also, a “clip”-type of arrangement could be used to affix the various draw lines to their respective eyelets or bores once the elements are put into their desired geometric configurations, thus securing the various draw lines to the load-bearing upper boom  4 . The junctions of the element wires with their associated semi-rigid element members do not need to be at, or nearly at, the outboard ends of the semi-rigid members to enjoy some or all of the advantages of the present invention. As has been mentioned earlier, the concentricity of the elements is not a critical factor in the operation of the embodiments disclosed. Obviously, only one eyelet is needed on metal plate  16  and metal plate  22  respectively for the various draw lines used in the system. Also, a single rod or pipe of suitable strength could be used for the strut  36 . 
     In all embodiments disclosed, the loop elements were essentially triangular in shape, the triangles being essentially symmetrical, and contacted at approximately the centers of their respective bases. All parasitic elements disclosed were electrically closed. As will be obvious to one skilled in the art, any suitable types of equipment for transmitting or receiving electromagnetic energy, or signals, may be used with any or all of the embodiments disclosed. 
     In all embodiments listed, the VSWR measurements were taken with a commercially manufactured meter listed as having an accuracy of plus or minus 10 per cent of full scale. 
     Although the embodiments listed have utilized single element and two element parasitic antennas only, as will be obvious to one skilled in the art, the overall structural design, as well as the unique operational parameters disclosed, can be enjoyed by using additional parasitic elements, or antennas which are not of the parasitic type, such as antennas using “double-driven” elements. 
     In all embodiments disclosed, the heights of the triangular elements were substantially less than those that would be necessary if the triangular shapes were equilateral. (The height of an equalateral triangular-shaped full-wave loop antenna element for use on the 20 meter amateur radio band would be approximately 20 feet.) The reduction in the vertical spacing between the upper load-bearing boom and the lower boom has contributed significantly to the structural stability and durability of the antenna assembly, as well as introducing very favorable operational characteristics to the antennas. Although the current data on full-wave loop antennas of the types disclosed indicates that effective operation of the parasitic array is not possible unless the sides of the elements are of equal length, or very nearly so, the extensive tests run, and the information disclosed indicates that this is not the case, and that very significant departures from the conventional proportions recommended are not only possible, but highly advantageous. As will be obvious to one skilled in the art, the particular base-to-height ratios disclosed are intended merely as examples of the present invention, and wide variances from these ratios can be successfully employed to achieve the desired structural and operational parameters of the antenna being designed. It is also interesting to note, that the feedpoint impedances of all the antennas disclosed in the embodiments listed correspond quite closely to the theoretical, and widely accepted impedance data that is listed for full-wave loop parasitic antennas having sides of equal or nearly equal length. 
     The base-to-height ratio used in the embodiment disclosed ranged from approximately 2.4/1 is 3/1, which is in sharp contrast to the base-to-height ratio of an equalateral triangle, which is approximately 1.15/1. The base-to-height ratio used in the embodiment described in connection with FIG. 2 was approximately 2.7/1 for all embodiments disclosed. 
     This variance in the proportions of the various embodiments disclosed introduced only slight effects in the various tuning parameters of the antennas disclosed, as well as various other antennas tested. Also, an certain of the embodiments of the 20 meter antennas elements disclosed, a certain ammount of “sag” existed, or was allowed to exist, in the semi-rigid lower portions of the elements, as well as a slight ammount of “sag” in the aluminum guy wire portions of the 20 meter antenna elements, such that the triangular shapes were not “perfectly” triangular. In earlier embodiments tested, and in other of the embodiments disclosed, the bottoms of the elements were configured absent of any “sag”, and the wire portions of the elements were essentially straight. This slight difference in configuration introduced no noticeable differences in the performance of the antennas tested. Also, although there had been some concern that the presence of the support structure for the booms traversing the entire height of all loop elements tested would cause some degenerative interaction to the performances of the antennas, there was no evidence that this was the case on any of the embodiments tested. 
     In all embodiments disclosed, each loop antenna element essentially described a single plane, all such planes being disposed in an essentially vertical orientation, and all loop antenna elements being disposed essentially orthagonally to the upper and lower booms, the booms being essentially parallel, the lower members of all loop antenna elements being disposed essentially horizontally. Small variations in these orientations and dispositions introduced during testing and adjustments caused no noticable changes in the operation of any of the embodiments disclosed. 
     The foregoing descriptions have been limited to specific embodiments of the invention. It will be aparant, however, that variations and modifications may be made to the invention, with the attainment of some or all of the advantages of the invention. Therefore, it is the object of the appended claims to cover all such modifications and variations as come within the true spirit and scope of the invention.