US 3864686 A
An antenna particularly suited for Citizens Band frequency use, and is particularly designed for mounting upon the roof of vehicles. The antenna is of a U-shaped configuration having a base portion and parallel leg portions. The leg portions are adjustable in length, and the antenna is supported in spaced relation to the vehicle roof to reduce standing wave reflected frequencies. A gamma assembly is attached to the base region of the antenna constituting a tuning capacitor, and the spacing of the leg portions causes a reflection and multiplication of radio frequencies, during transmission, causing a vertical directional orientation of the transmitted signals resulting in superior transmitting characteristics.
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Description (OCR text may contain errors)
United States Patent [191 Owen [4 1 Feb. 4, 1975 ROOF MOUNTED VEHICLE ANTENNA  Inventor: William G. Owen, 7934 Napoleon Rd., Jackson, Mich. 49201  Filed: Nov. 14, 1973  Appl. No.: 415,538
 U.S. Cl 343/713, 343/809, 343/822,
 Int. Cl. ..1-101q 1/32  Field of Search 343/713, 802, 806, 809, 343/846, 822
 References Cited UNlTED STATES PATENTS 2,370,628 3/1945 Alford 343/809 2,416,246 2/1947 Wheeler.... 343/806 2,976,532 3/1961 Guest 343/802 3,696,431 10/1972 Holland 343/713 3,742,508 6/1973 Tomaszewski 343/713 Primary ExaminerEli Lieberman Attorney, Agent, or Firm-Beaman & Beaman  ABSTRACT An antenna particularly suited for Citizens Band frequency use, and is particularly designed for mounting upon the roof of vehicles. The antenna is of a U- shaped configuration having a base portion and parallel leg portions. The leg portions are adjustable in length, and the antenna is supported in spaced relation to the vehicle roof to reduce standing wave reflected frequencies. A gamma assembly is attached to the base region of the antenna constituting a tuning capacitor, and the spacing of the leg portions causes a reflection and multiplication of radio frequencies, during transmission, causing a vertical directional orientation of the transmitted signals resulting in superior transmitting characteristics.
5 Claims, 4 Drawing Figures ROOF MOUNTED VEHICLE ANTENNA BACKGROUND OF THE INVENTION The field of the invention pertains to vehicle mounted antennas exteriorly mounted on the upper regions of the vehicle.
It has long been recognized that the design and construction of a radio antenna is important with respect to the transmitting and receiving characteristics of the associated radio equipment, and the technology of radio antennas is highly developed. Basically, it is known that best transmitting and receiving characteristics are obtained when the antenna is located at as high an elevation as possible, and it is also well recognized that the configuration of the antenna dipoles, or other signal receiving elements, is important in achieving directional orientation. In recent years there has beenan increased use of private transmitters and receivers operating at Citizens Band frequencies as such radio equipment may be operated with a minimum of qualifications by the operator. Citizens Band equipment is widely used in industry, as well as for private recreational and convenience purposes, and many Citizens Band receiver and transmitter sets are vehicle mounted.
By law, the power output of a Citizens Band transmitter is limited, and thus the antenna design and construction becomes most important if a high quality signal is to be transmitted. Accordingly, Citizens Band base installations of a nonmobile type usually utilize relatively large antennas elevated as high as practical. However, the antennas used upon vehicles carrying Citizens Band transmitters and receivers are necessarily limited in size and configuration and do not have the range and clarity of signal as a nonmobile installation utilizing a large elevated antenna.
The deficiencies of vehicle mounted antennas have attempted to be overcome by utilizing long whip atennas mounted upon the vehicle bumpers, or other vehicle locations, and transformers, and other signal amplifying devices are used. Such high performance antennas are expensive, and highly susceptible to damage due to their length, and the vibrations imposed thereon. Further, antennas extending significantly beyond the configuration of the vehicle limit vehicle movement through confined areas, such as trails and single lane roads, and such antennas are often damaged by tree branches, garage doors, and other relatively low overhanging obstructions.
Vehicle radio antennas of such size and configuration as to have efficient signal transmitting or receiving characteristics, and which also conform to the configuration of the vehicle have attempted to be produced, as shown in U.S. Pat. Nos. 2,136,305; 2,196,369; 2,203,986 and 2,161,435. However, the devices of such patents have not met all of the requisites of an automobile antenna, particularly for use with radio transmitters which are vehicle mounted.
SUMMARY .OF THE INVENTION it is an object ofthe invention to provide a low profile radio antenna suitable for both transmitting and receiving radio signals which may be mounted upon a vehicle roof, and does not significantly extend above the vehicle roof configuration.
It is a further object of the invention to provide a vehicle radio antenna suitable for both transmitting and receiving purposes which is of a rugged construction and is firmly mounted upon the vehicle roof at several locations, and does not interfere with vehicle usage.
An additional object of the invention is to provide a vehicle mounted radio antenna suitable for transmitting and receiving purposes, particularly at Citizens Band frequencies, which tends to multiply the transmitted radio signal, and although the antenna is substantially horizontally disposed, many of the reflected radio frequency signals are oriented in a vertical direction producing increased transmitting ranges.
In the practice of the invention the antenna is of a U- shaped configuration having a base portion and leg portions in spaced parallel relationship. A gamma assembly attached to the base portion is utilized as a tuning capacitor and the radio signals are transmitted to the gamma and hence to the antenna components wherein the radio signal is reflected between the leg portions of the antenna, multiplied and reflected, the reflected radio signals particularly being oriented in a vertical direction.
, The leg portions of the antenna are adjustable in length, and the antenna body is supported above the roof of the vehicle a sufficient distance -to prevent adverse effects from the standing wave reflected power effect.
The spacing between the leg portions of the antenna is one-seventh to one-eighth of the transmitted wave length, and as the signal is bounced between the leg portion elements the resultant repelling forces tend to reflect the signal upwardly in a vertical manner. Also, as the antenna is normally mounted upon the metal roof of the vehicle, radio signals are reflected from the roof as long as the roof is grounded to the vehicle frame. It has been found that an antenna constructed in accord with the invention is particularly suitable with recreational vehicles, which normally have large flat metal roofs, and as the antenna components are horizontally disposed relative to the roof, and are usually spaced approximately 8 inches from the roof, a low profile is produced wherein the antenna does not restrict vehicle usage because of low overhanging obstructions, and the antenna is not likely to be damaged.
BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned objects and advantages of the invention will be appreciated from the following description and accompanying drawings wherein:
FIG. 1 is a perspective view of an antenna constructed in accord with the invention as mounted upon a vehicle roof,
FIG. 2 is an enlarged, plan, detail view of the antenna base portion and gamma assembly, a portion of the gamma assembly being sectioned,
FIG. 3 is an elevational, sectional view as taken along section IIIIII of FIG. 2, and
FIG. 4 is a detail, elevational, enlarged view as taken along section IV-IV of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT An antenna in accord with the invention is particularly suitable for use with Citizens Band radios which operate in the 26.995 27.325 MHz frequency range and also at 10 meters, and is particularly designed for vehicle mounting, although, of course, the antenna could be used as a nonportable base section antenna. Because of the antennas low profile, light weight, and excellent transmitting and receiving characteristics its use with vehicles is highly desirable in view of the improved performance obtained as compared with conventional vehicle mounted antennas. However, as the antenna is of a U-configuration, and of a relatively large size, a commercial embodiment having a width of approximately 5, and a length of approximately 4', it finds particular usage as mounted upon recreational vehicles, pickup truck box covers, and similar vehicles having relatively large flat roofs. The antenna of the invention may be mounted upon the roof of automobiles, but its presence is more noticeable than when mounted upon a recreational vehicle having a large flat roof.
The antenna body, generally indicated at is of a U-shaped configuration and is mounted upon the substantially flat vehicle roof, generally indicated at 12, in a horizontal manner wherein the plane of the antenna is substantially parallel to the plane of the vehicle roof. The antenna body is supported in spaced relationship to the vehicle roof byinsulated brackets 14, and a metallic Z bracket 16 is also interposed between the antenna and the vehicle roof. A capacitance relationship to the antenna is produced by the gamma assembly 18 which is connected to the antenna lead of a radio, such as a Citizens Band transmitting and receiving set, not shown, within the vehicle.
The antenna body 10 consists ofa plurality of tubular members, usually formed of aluminum tubing, interconnected together. The base portion 20 consists of a pair of tubular L-shaped portions 22 interconnected at their long ends by a tubular sleeve 24. A pair of bolts 26 extending through the sleeve 24, also extend through holes defined adjacent the long ends of the portions 22 to affix the portions 22 to the sleeve. The short end of the portions 22 are connected to the antenna leg portions 28 which include tubes 30, which are received within the base portions 22 and attached thereto by screws 32, FIG. 1. The ends of the leg portions 28 consist of smaller diameter tubes 34 telescopically received within the leg portion tubes 30, and are adjustable within the tubes 30 in an axial direction. The axial length of the leg portions 34 is fixed, once adjusted, by circumferential clamps 36, such as of the worm screw type, circumscribing the free ends of the tubes 30. The free ends of the tubes 30 are slotted so as to permit compression by the clamps 36 on the leg tube portions 34.
The antenna body, including leg portions 28, are maintained in spaced relationship to the vehicle roof 12 by a plurality of dielectric brackets 14 preferably formed ofa synthetic plastic material. The antenna leg portions are attached to the brackets 14 by a clamp 38, FIG. 4, and screws 40 extending through the base of the brackets affix the brackets to the vehicle roof.
The base portion 20 of the antenna body is attached to a metal Z bracket 16, FIG. 3, mounted upon the vehicle roof by screws 42, and the portion 44 of the Z bracket includes holes receiving the bolts 26. The bracket 16 thereby grounds the antenna body to the roof. An insulated plate 46 is affixed to the lower side of the Z bracket portion 44 by bolts 26 and extends away from the base portion 20, as apparent from'the drawing.
The radio signals are imposed upon the antenna body 10 by a gamma assembly 18 attached to the plate 46. The gamma assembly includes a tube 48 having a flattened end 50 having a hole defined therein for receiving the terminal bolt 52. The terminal bolt simultaneously attaches the tube 48 to the insulated plate 46, and affixes the antenna lead 54 to the tube, as apparent in FIG. 3.
A dielectric sleeve 56 is closely received and fixed within the tube 48 and is flattened at end 50 and extends from the open end of the tube, as apparent in FIG. 2. The gamma rod 58 is slidably received within the sleeve 56, extending within the confines of the tube, as apparent in FIG. 2. The gamma rod 58 includes a right angle band, and the portion 60 is electrically connected to a base portion 22 by the attachment block 62, which, uses set screws to affix the portion 22 within a hole defined therein, and the rod 58 within a hole defined therein.
Tuning of the gamma assembly to the antenna body is accomplished by axially positioning the rod 58 within the tube 48 to achieve the desired capacitance, and such adjustment is accomplished upon unloosening of the screw 64 to permit the block 62 to slide along the antenna tube portion 22. Once the desired adjustment is accomplished the screw 64 is tightened, and a clamping band 66 is tightened about the dielectric sleeve 56 to compress the sleeve upon the rod 58.
The spacing between the leg portions 28 is approximately one-seventh to one-eighth the Citizens Band frequencies to be transmitted, and this spacing permits a most effective bouncing" of the transmitted radio signal between the leg portions to multiply the signal and repel the signal in an upward vertical manner in a direction perpendicular to the general plane of the antenna.
In order to prevent reduction of the magnitude oflhe transmitted signals due to standing wave reflected power effects, the height of the brackets 14 and 16 is such that the antenna body 10 is supported approximately 8 to 8% inches from the roof 12 of the vehicle, and this spacing has been determined to be sufficient to eliminate substantially all of the standing wave reflected power losses, and still maintain a low antenna profile.
Best transmitting results are achieved with vehicles having metal roofs that are grounded to the vehicle frame. However, the antenna functions efficiently upon a nonmetallic roof or support if the antenna is properly DC grounded at the midpoint of the base portion 20, as by ground wire 68. With a metal roofed vehicle the best results are obtained as the grounded roof tends to bleed off excess radio frequency signals to assure a low standing wave ratio.
The leg tubes 34 are adjusted within the leg tube portions 30 such that the length of the leg portions 28 is substantially a half wave length with respect to the desired range of radio frequencies to be transmitted, and thus it will be appreciated that the antenna may be readily tuned" to handle those frequencies being transmitted, and received, and yet the construction of the antenna from aluminum tubular members results in a low cost and easily installed construction.
It will be appreciated that various modifications to the inventive concept may be apparent to those skilled in the art without departing from the spirit and scope of the invention.
1. An antenna particularly suitable for vehicle roof mounting and Citizen Band frequency usage comprising, in combination, a U-shaped tubular antenna body having a base portion and substantially parallel leg portions, the spacing between said leg portions being oneseventh to one-eighth the wavelength of the radio frequency being transmitted, a plurality of supports connected to said leg portions for supporting said antenna body in spaced relation to a supporting surface, a base support connected to said base portion, a gamma tube assembly connected to said base support positioned in parallel spaced relationship to said base portion, an antenna conductor connected to said gamma tube, and grounding means connected to said antenna body.
2. In an antenna as in claim 1, adjusting means mounted upon said leg portions for adjusting the length thereof.
3. In an antenna as in claim 2 wherein said leg portions each comprise a large tubular element adjacent said base portion and a small tubular element telescopically received within a large'element and axially adjustable therein and retaining means fixing said small elements within its associated large element.
4. in an antenna as in claim 1 wherein said gamma tube assembly includes a tube, said antenna conductor being attached to said tube, a tubular dielectric sleeve within said tube and fixed relative thereto, and a gamma rod within said sleeve having an end electrically connected to said antenna body base portion.
5. In an antenna as in claim 4 wherein said dielectric sleeve extends from said tube, and a band clamp circumscribing said sleeve exteriorly of said tube clamping said sleeve upon said gamma rod.