US 2716703 A
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Aug. 30, 1955 J. M. KANE TELEVISION ANTENNA Filed May l5, 1952 INVENTOR. dames /1/1, Kane 4 MEMBER 0F THE FYROM 2,716,703 Patented Aug. 30, 1955 United States Patent Olice 2,716,703 TELEVISION ANTENNA James M. Kane, Los Gatos, Calif. Application May 15, 1952, Serial No. 287,902 1 Claim. (Cl. Z50-33.51)
This invention relates to a parasitic array of the Yagi type. More particularly, it relates to an antenna which is suitable for use in fringe area television reception of a number of channels.
It is one object of the present invention to provide a multiple band antenna which signal strength making it suitable for use in television fringe areas.
i In the drawings forming a is illustrated nels 4, 5 and 7 as they are now designated by the Federal It will be obvious to those skilled in the art that the same principles may be em- K' bodied in antennas suitable for reception of any desired channels and that more than three channels may be combined in a single antenna. In the description of the invention frequent reference will be made to the receiving properties of the antenna but it is obvious that the same principles may be embodied in a transmitting antenna.
Turning now to the drawings which form a part of this application there is shown in Figure l a perspective View of my improved television antenna.
In Figures 2 there is shown a detailed view of the method of coupling the driven element on channels 4 and 5 to the transmission line.
gives a high gain and high all the parasitic elements and the driven element for channel 7 on the transmission line.
Referring now to the drawings by reference characters, there is shown in Figure l a television antenna having two parallel spaced bars designated 4 and 6 which serve both as a transmission line and as a support for the elements of the antenna. Bars 4 and 6 may be suitably made of thin `walled aluminum tubing having an outside diameter of l inch and spaced l2 inches. Other suitable dimensions may be used, such as 1.25 inch tubing spaced 7.75 inches on centers. With these particular dimensions, the bars v4 and 6 constitute a transmission line having an impedance of slightly over 400 ohms. Thus, the transmission line consisting of bars 4 and 6 provides a good impedance Wire transmission line 8 which has size 18 copper Wires spaced 1 inch between center.
Fastening means 10 are provided at one end of the transmission line for coupling to the open wire line 8. The impedance match is sufficiently close to permit ordinary plastic insulated line Twin Lead) to be used instead'of the air insulated line illustrated.
The bars 4 and 6 are supported and held in their spaced relationship by a center section 12 which is preferably antenna to a mast 13. of plastic or metal but Center section 12 may be made 1s suitably made with the center ter section 12 and for insulating the bars from the center section 12.
Both the driven and parasitic elements are supported at right angles to the bars 4 and 6 as is shown in the drawings.
ln the embodiment shown, the antenna has three driven 1/2 inch O. D. aluminum tubing, although other suitahle metals may be used.
The method of fastening these two driven elements to the bars 4 and 6 is shown in detail in Figure 2. The
- surrounded by a suitable insulator such as polyethylene ln Figure 3 is shown a detailed view of the method of coupling the driven element for channel 4 to the transmission line.
Figure 4 is a detailed view of the method of supporting The capacitance of such a coupling is about 10 mmfd.
A different method is used for fastening the driven element for channel 7 and also the channels to the transmission line.
consists of a metallic ring rial 42. Preferably the ring is made from attened tubing. The dimensions of this connection are so selected that a connector has a capacity of about element 32 is connected to the transmission line capacitatively only.
Having now described the driven elements of the array, the parasitic elements will be described. Located at the front ot' the antenna is the director 42 for channel 5. The director is 67 inches long and is spaced 29 inches (0.2 wave-length) from the channel driven element 16. It will be noted that the director 42 is mounted on the transmission line by means of wooden rods 44 and 46. These wooden rods serve as insulators for the element 42 and are 8 inches in length. This leaves 2l inches of the transmission lines 4 and 6 ahead of the driven element 16, said lengths acting as matching stubs to match the driven element 16 to the transmission line. The wooden rods 44 and 46 may be painted with aluminum paint, thereby constituting a resistance element. Such a resistance tends to swamp any currents traveling from the back to the front of the antenna. Without such a terminating resistance, any reflected waves picked up from the opposite direction would be reected back into the transmission line and cause a ghost image. 1n extreme fringe areas, the resistance may be omitted. Instead of painting the rods,` a resistor may be fastened across the front of bars 4 and 6. A valve of 200 to 400 ohms is suitable.
The element 48 is 77 inches long and is mounted 33 inches (0.2 wavelength) from the elements 16 and 18. The element 48 serves as a director for driven element 18 and as a recctor for driven element 16. The element 16 also serves as a director for driven element 18. Mounted at the rear of the antenna is element 50 which is 84 inches long and spaced 33 inches from the element 18. The element 50 acts as a reector for driven element 18.
Thus, the channel 5 driven element 16 has a director 42 and a reector 43 and is provided with a matching open stub which is 2l inches long to match it to the transmission line. The channel 4 driven element 18 has two director elements 16 and 48 and one reector 50. That portion of the transmission lines 4 and 6 lying in front of the driven element 18 constitutes about 1/2 wave length at the channel 4 frequency and assists in matching the channel 4 driven element to the line.
The channel 7 elements are preferably mounted on the opposite side of the bars 4 and 6 from the elements for channels 4 and 5, as shown. The channel 7 driven element 32 is 31.2 inches long and is insulated from the transmission line as shown; it has three director elements 52, S25 and 54 each of which is 30 inches long. The director clement 52 is mounted 13 inches (0.2 wavelength) from the element 32 and in turn the element 53 is mounted 13 inches in front of element 52 and element S4 is mounted 13 inches in front of element 53. The reflector for channel '7 is the element 56 which is 33 inches long and mounted 13 inches behind the driven element 32.
40 covered with a plastic mate-y mmfd; the
As has been previously mentioned, the driven element 32 is insulated from the transmission lines 4 and 6 at its point of support and is coupled to the transmission line by the matching lines 36 and 38 which in turn are capaci- 5 tatively coupled to the transmission lines. The elements 36 and 38 are about 28 inches long. The length of the electrical path from the channel 7 driven element 32 through the connecting lines 36 and 38 to the channel 4 driven element 18 is about 45 inches. This constitutes about 1A wave length for channel 4 andan odd multiple of a l/i wave length, i. e. 3A wave length, for channel 7. This prevents there being interaction between the two elements which would result in one driven element shorting out the other.
Ey capacitatively coupling the driven elements to the transmission lines there is a minimum interference between the various driven elements which are coupled to the transmission lines. Further, the capacity coupling is such that it orcrs little resistance to the passage of the high frequency television signal but oiers a high resistance to the passage of lower frequencies, such as ignition noise. Thus, by capacitatively coupling the elements to the line one secures a high signal strength together with a high attenuation of lower frequency noise.
it will be noted that the spacing between any driven element and its parasitic elements is about 0.2 wavelength. By using this separation the Q of the antenna is kept low, giving a broad response to pass on entire television channel.
The antenna of the present invention is a system or method whereby multiple complete antennas may be coupled through capacitances to a common transmission line.
An antenna for high frequency use having in combination a spaced rigid transmission line, said transmission line having at right angles thereto more than one driven element, each of said driven elements being loosely coupled to the transmission line and parasitic elements insulated from said transmission line, said rigid transmission line .U furnishing the sole support for the driven and parasitic elements, and wherein the spacing of one of said driven elements on the transmission line acts as a shorted matching stub for another of said driven elements on said transmission line.
References Cited in the tileof this patent UNITED STATES PATENTS 2,175,363 Roberts Oct. l0, 1939 2,290,371 Katzin July 21, 1942 2,292,791 Minis Aug. 1l, 1942 2,297,329 Scheldorf S pt. 29, 1942 2,477,647 Pickles et al. Aug. 2, 1949 2,624,001 Woodward Dec. 30, 1952