US 3123826 A
Description (OCR text may contain errors)
March 3, 1964 J. D. DURHAM 3,123,826
ULTRA HIGH FREQUENCY TELEVISION ANTENNA Filed Aug. 17, 1960 INVENTOR JOSEPH D. DURHAM ATTORNEY? United States Patent 3,123,826 ULTRA HIGH FREQUENCY TELEVISION ANTENNA Joseph D. Durham, Lakeview, Tex., assignor to Lakewood This invention relates to antennas and more particu larly to receiving type antennas primarily intended for use in television channels that are allocated for use with ultra high frequency signals.
It is the general object of the present invention to provide a novel and improved television receiving antenna of improved electrical and mechanical characteristics.
More particularly it is an object of the invention to provide an antenna of the dipole type which shows superior reduction in unwanted signal pick-up without any loss in elliciency in receiving the direct desired signal.
An important feature of the invention consists in the arrangement of a double dipole antenna, which may be referred to as of the dumb-bell shape, which is capable of greater gain than the conventional dipole using thin rods.
Another important object of the invention is to provide an antenna using two circular dipoles so designed that by changing the circumference of each of the dipoles and maintaining the stacking bars at onehalf of the desired reception wave length the two circular dipoles are maintained in phase for maximum energy delivered.
A further important feature of the antenna is its high sensitivity to circularly polarized waves and, hence, it has superior characteristics for ultra high frequency reception of television signals, for with its use stronger directive signals are received which are less subject to interference.
Still another important feature of the invention resides in its ability to provide a remarkable reduction in signal pick-up from ground level and from reflected waves from above, thus eliminating unwanted signals which produce a ghosting effect on the picture. This result is achieved. since wave fronts of signals striking the circular antenna from above or below induce voltages in opposite sides of the dipole circles which are in phase and because of the additional half wave of travel in the stacking bars which the signal must undergo before it reaches the top circle from the lower one or viceversa the unwanted signal noise is cancelled at the feed point of the transmission line.
The antenna as illustrated is designed primarily for use in the so-called translator frequencies which are channels 70 through 83 as allocated by the Federal Communications Commission. The design is such, however, that by changing the circumference of the circles and maintaining the stacking bars at one-half of the wanted wave-length it is particularly effective, but the dimensions are not highly critical so that a reasonably broad spectrum may be received, eliminating the necessity of more than one antenna to take care of the present allotted ultra high frequency translator channels for television.
Other and further features and objects of the present invention will be more apparent to those skilled in the art upon a consideration of the following specification and the accompanying drawings wherein is disclosed a single exemplary embodiment of the invention with the understanding that such changes and modifications may be made therein as Well within the scope of the appended 3,123,825 Patented Mar. 3, 1964 claims without departing from the spirit of the invention.
In said drawings:
FIGURE 1 is an elevation of the dumb-bell antenna constructed in accordance with the present invention shown mounted on a suitable pole and spaced appropriately in front of a reflector element;
FIGURE 2 is a side elevation thereof; and
FIGURE 3 is a sectional view on an enlarged scale taken on line 33 of FIGURE 1 showing the adjustable feed points connector for the transmission line.
As illustrated in the drawings the antenna is designed for mounting on a single pole which may be a metal tube of appropriate height intended to be positioned vertically. Near its upper end the tube is horizontally drilled with a pair of spaced holes for passing suitable machine screws 11 adapted to mount all of the components of the antenna thereon. The screws are first passed through suitable washers and then through openings in the reflector 12 formed as a flat rectangle of mesh screen, then through additional washers as shown so that the screen is spaced from the post after the screws are extended through the holes in the post. Thereafter they pass through the splayed feet 14 of an insulating bracket 15 which is generally of V-shape as illustrated and may be formed of a suitable plastic. its height plus the diameter of the pole should be of the order of onequarter wave-length of the average of the wave-lengths of the channels intended to be received if the antenna is designed to have a relatively broad spectrum. Otherwise if intended for single channel use it is preferred that the parts be dimensioned to space the antenna onequarter wave-length from the reflector screen for best results. Screen is used for the reflector since it is substantially as effective as a solid plate and offers an enormous reduction in wind resistance and a considerable reduction in weight. The remote end of the insulator has a flat portion 16 against which the stacking bars of the antenna itself are secured by means of a through bolt 17, an insulating clip 18 for the stacking bars and a suitable nut 19.
The antenna proper is as previously mentioned of dumbbell shape including two nearly complete rings 21 and 22 formed of aluminum rod or tube having a diameter of the order of of an inch. The circles are joined together and maintained in the same plane by two integral stacking bars 2d, 25 of the same material which are spaced apart, a distance of the order of one-half inch.
Preferably the whole dumb-bell antenna is made from a single length of aluminum wire and the ends are abutted and welded forming a closed loop.
For mounting purposes it is preferred to have a pair of appropriate half cylindrical vertical grooves in the flat end piece 16 of the insulator 15 appropriately spaced to receive the stacking wires and similar grooves may be provided in the insulating block 18. This prevents any tendency towards rotation away from the vertical position of the antenna.
The lead-in or transmission line is preferably of the conventional parallel wire type, the wires being at the edges of a plastic tape and spaced to provide the most appropriate resistance at the median frequency of the signals for which the antenna is designed. Such an antenna lead-in is illustrated at 26 and is appropriately attached to the pole 10 below the reflector screen by an insulating clip 27 or by the use of ordinary friction tape.
The two transmission line conductors are connected respectively and individually to the stacking bars 24 and 25 between the antenna loops and the arrangement here is shown in the enlarged view of FIGURE 3 where the conductors 29 and 36 from the lead-in 26 are bared near their ends and secured by screws 31 each to a metal clip 32 and 33 individually mounted on the inner face of one of the two plastic strips 34 which span the vertical bars laterally and are applied one on the front and one on the back of the pair of bars and held together by a central belt or screw 35. The metal strips and plastic strips may be grooved to lie over the surfaces of the bars to provide satisfactory contact therewith and the strips each have an edge tab turned backwardly as indicated at 36 in FIG- URE 3 in which the screws 31 are threaded for attaching the conductors.
The construction just described permits adjustment of the connecting points for the lead-in wires along the lengths of the bars connecting the antenna loops and permits a degree of choice of the maximum response of the antenna to a particular wave length. In this manner if several stations are available the antenna may be adjusted by the means just described to give its maximum response to the weakest signals. If it is desired to attach the leadin exactly at the center of the vertical bars the antenna may be moved up or down in respect to the attachment point to the standoff insulator to permit the lead-inc0nnector to be applied exactly at the centers of the bars.
The present antenna was designed primarily for use in the ultra high frequency transmission television channels that are primarily allocated to UHF translators which are allotted channels 70 through 83. In order to illustrate the design factors in connection with the antenna the figures are given for one designed primarily for channel 75 which has been found to respond to a sufiiciently broad band to give both a good picture and excellent Voice reception on channels 70 through 83. The antenna is constructed with a reflector screen 12 approximately 12 inches wide and 18 inches long and the dipole-dipole antenna is made of inch aluminum rod consisting of two loops 21, 22 each 14.1 inches in circumference joined together in a vertical plane by two bars of the same material. Since the spacing between the bars is one-half inch or of the order of one tenth of loop diameter the overall circumference of each circle is 14.6 inches, just slightly more than the wave length of the frequency of channel 75. The stacking bars 24-, 25 are each approximately 6 /2 inches long which is closely of the order of /2 wave length, which serves to provide an excellent phasing for the two circle dipoles. The plastic stand-off insulator 15 is about 2 /8 inches high.
Two of these dipole-dipole antennas may be stacked vertically to deliver more gain if needed and four dipoles can be stacked, two on each side where maximum gain is desired. The means for achieving this relationship with transposition of the stacking bars follows well known and standard procedure.
The antenna disclosed is intended for circular as well as horizontal or vertical polarized waves as used in the UHF translator channels and is most effective when its plane is at right angles to the direction of signal wave travel.
1. An antenna comprising two substantially complete, identical, circular one wave length dipole loops of rigid conducting material lying in the same plane, each loop having an opening therein of the order of one tenth the loop diameter facing the opening in the other, a pair of parallel conductors spaced in said plane to the order of the loop opening width and each having its ends conductively connected to the free ends of the loops on its side of said gaps, said conductors being constructed of such length as to phase the circular dipoles, and means to connect the wires of a transmission line separately to said conductors.
2. The antenna as defined in claim 1 in which a standoff insulator is secured to said parallel conductors intermediate the dipoles and forms the sole support for the antenna and means supporting said insulator to mount the antenna in a substantially vertical plane directly from a pole.
3. The antenna as defined in claim 2 in which said means supports the antenna with the dipoles one above the other in substantially the vertical plane in which each lies.
4. The antenna as defined in claim 2 in which said support means also mounts a reflector in a plane parallel to that of the loops.
5. An antenna for the reception of circularly polarized, ultra high frequency television signals comprising two circular dipole loops each formed of rigid conductor material all lying in a single plane and, each having a small gap spaced from and facing the gap in the other loop, the circumference of each loop substantially matching the wave length of the wanted signal, a pair of rigid parallel conductors lying in said plane spaced the width of said gaps and joining the loops into a continuous closed dumbbell shaped figure, each of said parallel conductors being of the order of half a wave-length long to properly phase the circular dipoles, insulator means secured to said conductors for mounting the antenna with the dipoles in a substantially vertical plane one above the other, and means intermediate the length of said conductors to connect them to the conductors of a transmission line.
6. The antenna as claimed in claim 5 in which the connector means for the transmission line is adjustable along the length of the parallel conductors to achieve improved reception of signals of wave-lengths differing from those for which the antenna is specifically sized.
References Cited in the file of this patent UNITED STATES PATENTS 2,755,465 Ramsay July 17, 1956 2,827,628 Swinehart et a1 Mar. 18, 1958 2,884,631 OHare et a1. Apr. 28, 1959 OTHER REFERENCES Television and FM Antenna Guide, by Noll and Mandl, The MacMillan Co., 1951, pages 78 and 215.