Abstract:
An antenna whip construction having a radiating or radiation receiving antenna element, and an isolation transformer electrically connected between the antenna element and the support fitting of the whip, and all of which is bound into a structural self supporting whip. The isolation transformer has a pair of input terminals for connection to a transmission line, and the isolation transformer allows feed through from one of the input terminals to the antenna element but effectively isolates the antenna element from the other of the input terminals.

Description:
TECHNICAL FIELD 
     The present invention relates to the construction of a whip antenna that does not require grounding. 
     BACKGROUND OF THE INVENTION 
     Conventional whip antennas of less than a half wave length must be connected to some kind of a ground, so that the portion of the wave that extends out of the whip can flow in and out of the ground. If the grounding connection breaks or its resistance becomes large, the efficacy of the antenna is impaired. Conventional whips when mounted on nonmetallic bodies require elaborate grounding systems to be used therewith. 
     It is an object of the present invention to produce a whip antenna which will operate satisfactorily without an external ground. 
     Further objects and advantages will become apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiments described with reference to the accompying drawing forming a part of this specification. 
     BRIEF SUMMARY OF THE INVENTION 
     According to principles of the present invention, a construction of whip antenna is provided wherein isolation of its radiating or receiving portion from one of its transmission line terminals takes place above its support fitting. In such an arrangement, any changes in the resistance of the connection between the support fitting and its support structure has no effect on radio transmission or reception. In those instances where the antenna is to be connected to a coaxial transmission line, the whip is fed by the center conductor, and a decoupling transformer is connected to the outside conductor of the coaxial cable, so that the reflected wave from the whip is decoupled from the outside conductor. By so doing the transmission line is prevented from radiating, and the wave reflection in the center conductor of the transmission line is shielded by the outside conductor of the transmission line. In the most preferred embodiment, the decoupling transformer is made by a bifilar winding at the base of the whip. The center conductor from the coaxial transmission line is fed up through one of the bifilar windings and then to the radiating or receiving portion of the whip. The other of the bifilar windings is fed from its tip down through the winding and then to the outside conductor of the coaxial transmission line. This arrangement effectively isolates the center conductor from the outside conductor, and the outside conductor does not need to be grounded adjacent the antenna. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     FIG. 1 is a schematic drawing of an antenna embodying principles of the present invention. 
     FIG. 2 is a side elevational view, partially sectioned, and with portions broken away so that the various elements of the embodiment can be seen in a single view. 
     FIG. 3 is a side elevational view, partially sectioned, and with portions broken away so that the various elements of a second embodiment can be seen in a single view. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 of the drawing is a schematic view of an antenna embodying principles of the present invention. The antenna comprises an electrically resonatable conductor A for transforming electrical pulsations into radio waves and vice versa. The conductor A may be a straight conductor, but is shown coiled so that its length can be made much shorter than if it were a straight conductor. The conductor A is in series with an isolation transformer B which in turn is connected to the two conductors of a coaxial transmission line C. The isolation transformer B may be variously constructed, but is shown as formed by a bifilar winding. One of the bifilar windings 10 is connected between the resonatable conductor A and the center conductor 12 of the coaxial tranmission line C. The other of the bifilar windings 14 has its upper end connected to the center conductor 12 by straight wire 16, and its lower end connected to the outside conductor 18 of the coaxial cable C. By so doing, electrical impulses flow between conductors 12 and 18 to produce opposing fields in the windings 10 and 14. Current flow in winding 14 helps current flow in winding 10, and resists or prevents current flow from winding 10 from entering the outside conductor 18. Therefore, a connection between the outside conductor 18 and ground adjacent the whip antenna is made unnecessary. 
     The embodiment shown in FIG. 2 corresponds to the schematic drawing of FIG. 1 and those portions thereof which correspond are so numbered. The embodiment of FIG. 2 has a nonmetallic support rod 20 whose lower end is cemented into a metal sleeve 22. The lower end of metal sleeve 22 has a reduced diameter threaded boss 24, which is threaded into the upper end of an internally threaded coupling 26. The lower end of coupling 26 is in turn threaded onto the center conducting pin 28 of a coaxial cable connector D. The center conducting pin 28 extends through an opening 30 in the horizontal leg 32 of an angle bracket 34, and an anular insulating washer 36 is positioned around the pin 28, and is clamped between the leg 32 and the coupling 26. The cable connector D also includes an externally threaded sleeve 38 which is bonded to the lower end of center pin 28 by a body 40 of nylon or other hard plastic. The upper end of sleeve 38 bears against the under side of leg 32 to support the whip structure from the angle bracket 34. The lower end of pin 28 is tubular and serrated to receive the conventional center pin (not shown) of a coaxial cable connector (not shown) which threads onto the outside of sleeve 38. The lower leg 42 of angle bracket 34 has a hat-shaped clamp 44 and a pair of bolts 46 for confining a support (not shown) between clamp 44 and leg 42. 
     The nonmetallic support rod 20 has wire 16 embedded therein, with its lower end pulled out and soldered to the upper end of sleeve 22. The upper end of wire 16 is pulled out and soldered to the upper end of bifilar winding 14. The lower end of winding 14 extends down to a transmission line terminal 48 that is connected to one of the bolts 46. The lower end of bifilar winding 10 is also soldered to the upper end of metal sleeve 22. The same wire that forms bifilar winding 10 continues upwardly and is wrapped in tight coils 50 to form the resonatable conductor A for transforming electrical pulses into radio waves and vice versa. The bifilar windings 10 and 14, and the resonatable conductor A, are tightly wound around the support rod 20 and are cemented thereto by a plastic film not shown. 
     The embodiment shown in FIG. 3 corresponds generally to the embodiment shown in FIG. 2 to utilize the structure of FIG. 1 but differs therefrom in that its bifilar windings are wound around a permeable core 52. Those portions of FIG. 3 which correspond to portions of FIG. 2 are designated by a like reference numeral, characterized further in that a suffix &#34;a&#34; is affixed thereto. The permeable core 52 is housed axially within a fiber glass support tube 54, the upper end of which is reinforced and cemented into the lower end of a metal sleeve 56. The upper end of sleeve 56 is internally threaded to receive the threaded boss 24a of metal sleeve 22a. The lower end of fiber glass support tube 54 abuts the top surface of sleeve 38a, and is cemented to a section of thin walled tubing 58 that is slipped over the outside of sleeve 38a, and crimped thereto to lock the assembly together. The antenna of FIG. 3 can be supported by clamping tube 58 to a suitable vertical support structure. The upper end of winding 10a is extended and soldered to the inside of metal sleeve 56. The bottom end of winding 10a is soldered to pin 28a, and the lower end of winding 14a is soldered to sleeve 38a. The top of conductor 14a is bent down and soldered to the bottom of winding 10a adjacent pin 28a. 
     It will be seen that the principles of the present invention can be utilized in a whip antenna for any broadcast band. For the 27 mHZ band, conductor 16 may be approximately 28 inches long, the bifilar windings 10 and 14 each may have a length of approximately 48 inches, and the radiating or radiation absorbing portion A may have a length of approximately 24 feet. 
     Whip antennas utilizing the above principles may be made for practically any broadcast band providing the length is within reason. The radiating or radiation absorption portion A should be at least a one quarter wave length and preferrably at least a half wave length so that the radiation pattern will be horizontal and slightly downwardly instead of upwardly. Practical antennas of at least a half wave length may be made for the 30 mHZ band, the 6 meter (50 mHZ) band, the 2 meter (144 mHZ) band, and the VHF (150 mHZ) band. The portion of the reflected wave which extends downwardly from portion A is decoupled from the outside conductor 18 of the transmission line by winding 14. Electrical flow through winding 10 induces a voltage in winding 14 which effectively decouples element A from conductor 18. Where a ferrite core 52 is utilized as shown in FIG. 3, the length of the bifilar windings 10a and 14a may be shortened to as little as approximately 8 turns around a 5/8 inch ferrite core 52 to achieve decoupling. 
     While the invention has been described in considerable detail, I do not wish to be limited to the particular embodiments shown and described, and it is my intention to cover hereby all novel adaptations, modifications, and arrangements thereof which come within the practice of those skilled in the art to which the invention relates, and which come within the purview of the following claims.