US 2771604 A
Description (OCR text may contain errors)
Nov. 20, 1956 s. E. GOLDSTEIN 2,771,604
VEHICULAR SHORT-WAVE ANTENNA Filed April 3, 1951 Jamafl/ 69/4 3757,
INVENTOR ATTORNEY United States Patent VEI-HCULAR SHORT-WAVE ANTENNA Samuel E. Goldstein, Los Angeles, Calif.
Application April 3, 1951, Serial No. 219,044
1 Claim. (Cl. 343-749) This invention relates broadly to the field of radio transmission and reception, and more particularly to a transmitting and receiving antenna of the type preferably, though not necessarily, used in connection with radioequipped vehicles or other mobile craft.
It is a principal object of this invention to provide an antenna adapted foruse in short wave transmission and reception and comprising a plurality of electrically conducting sections and simplified means for detachably connecting a loading coil of selected inductance intermediate said sections, whereby the transmitting and/or receiving bands from to 80 meters may be utilized, with the antenna resonated for optimum efiiciency in all bands.
It is customary to mount an antenna at the rear of a mobile craft for police radio communication or other short wave communication. Such antenna generally comprises a tubular electrically conducting structure approximately ten feet in height, and a loading impedance for improving the radiating and/or receiving characteristics at any one frequency. To cover the desired band of frequcncies, it is usual to provide means for adjusting the impedance of the loading coil whereby the antenna is made approximately resonant at a particular frequency. This is a somewhat cumbersome and time-consuming operation, as the radiating or receiving frequency may have to be varied over a wide band, or even between difierent bands, and therefore adjustments necessarily have to be made frequently.
Instead of adjusting the loading coil, it is also common to provide a plurality of coils for use with each antenna, each coil being designed for use with particular frequencies in a band. However, in using this method for covering several entire bands, for example those from 10 to 80 meters, it has been found difiicult to substitute one coil for another for the reason that detaching the coil from the tubular structure is also quite a cumbersome and time-consuming operation. In accordance with the present invention, the antenna is constructed to permit simplified and time saving substitutions of loading coils whereby any frequency lying in the 10 to 80 meter bands may be received or transmitted efiiciently.
It is a further object of the invention to provide an antenna comprising only three essential parts, namely an upper and lower tubular section and a loading coil unit mounted therebetween.
A still further object of the invention is to provide such an antenna wherein the loading coil is mounted about the periphery of an insulating tube having metallic ring members mounted thereon and connected to the loading coil and detachably connected to the upper and lower tubular sections of the antenna.
Another object is to provide an antenna for use in short wave transmission and reception having a loading coil detachably secured to upper and lower tubular sections whereby said coil, when mounted, is intermediate said sections.
Yet another object of the invention is to provide an antenna having means attached to the lower tubular section for mounting the antenna upon or adjacent the rear end of a vehicle or the like or other mobile craft, said means yieldingly supporting said antenna whereby physical shock is minimized.
The above and other objects and advantages of this invention will best be understood by referring to the following detailed specification of a preferred embodiment thereof, and to the accompanying drawings, in which:
Figure 1 is a view in elevation of the antenna shown mounted on a part of a mobile craft,
Figure 2 is a side view partly in section, and
Figure 3 is an enlarged sectional view of the loading coil shown in Figure 2, and its supporting structure.
Referring in detail to the drawings, and particularly to Figures 1 and 2, the antenna is generally represented by numeral 1. The upper current radiator or receiver 2 and the lower current radiator or receiver 3 may be of heights desired to attain optimum transmitting and/or receiving characteristics, but, for purposes of illustration, are shown broken away as at 3. Both sections are hollow tubular structures preferably of stainless steel, but it is to be understood that any suitable material may be used.
Upper section 2 is tapered and has a-flixed to its lower end an enlarged member 4, preferably of the same material, provided with a threaded end portion (not shown). At the top and bottom of lower section 3 are afiixed enlarged knurled members 5 having screw threaded portions, such as at 6, extending therefrom. Member 4 and the member 5 at the top of section 3 are primarily for attaching the loading coil unit 30 to the sections while the member 5 at the bottom of section 3 is to provide a connection to the mount generally represented by numeral 7. It is to be understood that the shape and size of member 4 and knurled members 5 may be of any form and are essential to the invention only in the sense that they provide a rigid and durable connection to the loading unit 30 and mount 7.
Mount 7 comprises a metal spring 8 having metal cap members 9 and 10 secured at each end thereof, the cap members having extensions 11.
Electrically conducting cap member 9 is adapted to receive electrically conducting screw connection 6 of lower antenna section 3 and an electrically conducting wire 12 connects caps 9 and 10. The bottom portion 13 of cap 10 is part of a joint 14, portion 13 being rotatably adjustable by means of locking screw 15. The base 16 of joint 14 is detachably connected to washers 17 and 18 of insulating material and to metal base plate member 19 by means of screws 21 which are adapted to secure the entire mount to a section 22 of a mobile craft or vehicle. Base 16 has an extension (not shown) which passes through members 17, 18, 19, and 22 to the terminal 23 connected with the transmitting or receiving equipment. It can be seen that current passes from lower section 3 to cap 9 and from thence through wire 12 to cap 10 and thus to connection 23.
The above described mount provides, due to the rotatable joint 14, means for swinging the entire antenna to the desired position such as that shown in Figure 1, or to a substantially vertical position. Also, due to spring 8, the antenna is yielding mounted to permit absorption of physical shocks caused by striking overhead obstructions or the like.
Again referring to Figure 1, there is supported between the lower part of loading coil unit 30 and member 5 at the top of lower section 2 a spacer member 25 of any suitable insulating material. The purpose of member 25 is to space a metallic hood and shield 26 from loading coil unit 30. Shield 26 is obviously held in position by the pressure exerted by the screw-threaded connection between the upper section 2 and loading coil unit 30, there being an opening in the top of the shield through which the screw threaded extension of member 4 extends.
It will be appreciated that the inductance coil 30, located intermediate the ends of the antenna, is exposed to rain and other weather conditions, as well as to substantial physical shocks which would not be the case if it were disposed at the bottom of the antenna structure. For this reason, it is necessary to provide adequate mechanical protection, and by means which will not shortcircuit the loading coil or inductance. The construction shown accomplishes this end in a very efiicacious manner, the metallic shield 26 being held rigidly in a fixed position about inductance 30 because of the pressure ex-- erted downward upon its bell-shaped upper end when it is clamped against the top of the inductance coil form when the upper section 2 of the antenna is threaded into the end of said form. The lower end of the shield is held in its proper position by the insulating member 25 which is dimensioned to be received snugly within the lower open end of shield 26, and is in turn clamped against the bottom end of inductance 30 (or, rather, its supporting form) when said form and the screw threaded member are threaded together.
As shown in the enlarged sectional view of Figure 3, the loading coil unit generally represented by numeral 30 comprises an inductor or coil 31 having a plurality of helically Wound turns upon the outer periphery of hollow tube 32 of insulating material. Tube 32 may be made of any suitable insulating material, and the turns of inductor 31 may either be spaced from each other for insulation purposes or they may be insulated from each other by any suitable coating, such as varnish, and wound close together.
At each end of tube 32, and securely held within the bore thereof, is a metallic ring member 33 provided with openings 34 to receive the screw-threaded extensions of sections 2 and 3. The upper and lower ends of coil 31 are electrically detachably-connected to members 33 by means of screws 35 which pass through the wall of tube 32, and are threaded into rings 33. Bonded to the exterior of tube 32, at its upper and lower end, is a metallic ring member 36. The purpose of ring members 33 and screws 35 is to provide a current path from the upper section 2 through coil 31 to lower section 3 and thence to the intake or outlet 23 of the mobile radio equipment. Screws 35 operate additionally to maintain the collars 33 mechanically in position within the ends of form tube 32. Rings 36 are merely to protect the ends of tube 33 and to provide seats for the upper 'cap portion of shield 26 and the spacer 25 when the parts are assembled.
From the above description, it can be seen that a compact antenna construction is provided, having simplified means for connecting sections 2 and 3 and a loading coil intermediate thereof. It has been found that placement of the loading coil intermediate of the sections greatly improves and increases the efliciency of the radiating and/or receiving characteristics. Each loading coil is designed to operate at maximum efiiciency at a certain band, say 20, 40, or meters. To change bands, it is merely necessary to disconnect upper section 2, remove shield 26, unscrew the loading coil unit in use and replace the loading coil unit with a unit having a coil designed for the selected band. The fact that each loading coil unit is provided with ring or collar members 33, and means connecting the loading coil to the rings, necessitates connecting only the screw threaded extensions of sections 2 and 3 to the selected unit to completely secure sections 2 and 3 and the loading coil unit together, mechanically and electrically. No terminal changes or the like are needed.
If desirable, the loading characteristics of the antenna at a particular frequency in a band may be adjusted to a predetermined value by loosening a screw 35 and changing the number of turns of the coil 31 being used. The impedance or loading characteristics of the coil 31 in use 1 may also be varied, together with the radiation characteristics of the antenna structure, by altering the space between turns of the coil. A set of coils is then available for optimum antenna efiiciency at each of several specific frequencies.
While there has been disclosed herein a preferred construction in accordance with the general principles of this invention, it is to be understood that many changes and modifications in the details of the apparatus may be made by those skilled in this general field, without departing from the scope of the invention as defined in the following claim.
A short-wave antenna of the linear radiator type comprising a pair of relatively lengthy colinear conductive radiator elements having their proximate ends formed to provide threaded studs, and an inductance coil assembly connecting the proximate ends of said elements to constitute the sole mechanical and electrical connection therebetween, said inductance assembly comprising an insulating cylindrical form, an internally threaded metallic collar within each end of said form, an inductance coil wound upon the outside of said form and having each of its opposite ends secured by a conductive screw passing radially through the form and threaded into the respective metallic collar thereof, whereby said screws serve to connect the ends of the coil to the respective collars and to maintain said collars mechanically in position within the ends of said form, a cylindrical metallic shield open at one end and bell-shaped at the other, said shield encompassing said form and coil with the. threaded stud of one of said radiator elements passing through an aperture in the bell shaped end of the shield and threaded into one of said collars, an insulating spacer disc disposed snugly within the other and open end of said shield, and the threaded stud of the other of said radiator elements passing through an aperture in said spacer disc and threaded into the other of said collars.
References Cited in the file of this patent UNITED STATES PATENTS 2,240,298 Heindel et a1 Apr. 29, 1941 2,311,472 Roosenstein Feb. 16, 1943 2,329,200 Hefele Sept. 14, 1943 2,419,611 Walsh Apr. 29, 1947