|Publication number||US3388400 A|
|Publication date||Jun 11, 1968|
|Filing date||May 28, 1965|
|Priority date||May 28, 1965|
|Publication number||US 3388400 A, US 3388400A, US-A-3388400, US3388400 A, US3388400A|
|Inventors||Veldhuis Albert C|
|Original Assignee||Trylon Inc|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (2), Referenced by (9), Classifications (9)|
|External Links: USPTO, USPTO Assignment, Espacenet|
June 11. 1968 A. c. VELDHUIS 3,388,400
BEOADBANDING ADAPTER FOR CIRCULARLY POLARIZED ANTENNA Filed May 28, 196E 3 Sheets-Sheet l I'IGEI- I N VEN TOR.
A 43 GLWGZJ June 11, 1968 A. c. VELDHUIS 3,388,400
BROADBANDING ADAPTER FOR CIRCULARLY POLARIZED ANTENNA Filed May 28, 1965 3 Sheets-Sheet 2 IN VENTUR.
# EA- GA) ATTOHNEYJ June 11, 1968 A. c. VELDHUIS ,3
BROADBANDING ADAPTER FOR CIRCULARLY POLARIZED ANTENNA Filed May 28, 1965 3 Sheets-Sheet 5 V5 WI? I40 I50- mspwslvzw Me I N VEN TOR.
QJM 62A United States Patent 3,388,400 BROADBANDENG ADAPTER FOR CIRCULARLY POLARIZED ANTENNA Albert C. Veldlruis, West Chester, Pa., assignor to Trylon Incorporated, Elverson, Pa., 21 corporation of Pennsylvania Filed May 28, 1965, Ser. No. 459,545 2 Claims. (Cl. 343--822) This invention relates to VHF (very high frequency) circularly polarized antennae of the type or types in use for airport ground to air communications.
There are in operation a large number of circularly polarized ground to air control tower antennae of the Federal Aviation Agency. One example is FA-S 301 which were made in accordance with Federal Aviation Agency Specification FAA-R-766b, Amendment No. 2 dated Apr. 27, 1960. These antennae utilize four half-wavelength dipoles spaced approximately one-third wavelength at the mid-band frequency of operation. The frequency range of the antenna is 118 to 135 megacycles. Each dipole is inclined 30 from the horizontal plane. The dipole elements of the four dipoles are connected to a central support body or hub by means of four parallel transmission lines of approximately 200 ohms impedance. The input receptacle at the base of the antenna is a type UG-S 8A/ U fitting for connection to RG8/U coaxial cable.
The object of the present invention is to provide broadbanding means which may be readily and easily installed in the field at the site of existing antenna type FA-530l, and similar type antennae, thereby to improve the impedance characteristics of the antenna over a wider range of frequencies. This object is achieved in accordance with the present invention by the provision and connection of a simple broadbanding stub.
In the drawing:
FIG. 1 is a perspective illustration of a VHF circularly polarized antenna, type FA-530l; included within the antenna mast 28, but not visible in FIG. 1, is the broadbanding adapter of the present invention;
FIG. 2 is a view in section along the line IIII of FIG. 1 showing the structural details of the broadbanding stub and the place and manner of its insertion into an existing antenna type FA-5301 to transform the antenna to broadband operation; and
FIG. 3 is a graphical representation which illustrates the improvement achieved by the broadband device of the present invention.
Referring now to FIG. 1, there is illustrated a circularly polarized antenna type FA-5301. This antenna has four half-wavelength dipoles 21, 22, 23 and 24 each of which is inclined 30 from the horizontal plane. Each dipole is comprised of two elements identified by the suffix a and b added to the reference numeral of the particular dipole. For example, dipole 21 is comprised of dipole elements 21a and 21b; dipole 22 is comprised of dipole elements 22a and 2212; etc. Each pair of dipole elements is connected to a central support hub 25 by a ZOO-ohm parallel transmission line. For example, dipole 21 is connected to the central hub 25 by parallel transmission line 121 comprised of conductor arms 121a and 121b connecting dipole elements 21a and 21b, respectively.
Central support hub 25 is comprised of an upper element 25a and a lower element 251) separated from each other by an insulating spacer 26. The a dipole elements 21a, 22a, 23a, 24a, are connected to and supported by the upper hub element 25a. The b dipole elements 21b, 22b, 23b and 24b are connected to and supported by the lower hub element 251;.
The upper hub element 25a, the four upper transmission lines 121a, 122a, etc., and the four a dipole elements, are all part of a one-piece solid aluminum alloy #43 cast- Patented June 11, 1968 ice ing. Similarly, the lower hub element 25b, the four lower transmission lines 121b, 122b, etc., and the four b dipole elements, are all part of a one-piece solid aluminum alloy #43 casting.
The lower hub casting also includes a depending cylindrical skirt portion 27 adapted to fit over the antenna mast 28 and to be secured thereto as by set screws 29. The lower hub casting includes, within the depending cylindrical skirt portion 27 a depending tubular hub portion 31.
As already indicated, the upper hub casting is separated from the lower hub casting by an insulating spacer 26, preferably plastic. The upper hub casting is secured to the lower hub casting by four nylon studs 35 each equipped with suitable O-ring 36, lock washer 34, and cap nut 37.
An antenna lead-in connecting rod 39 is threaded into a hole in the upper hub casting and extends downwardly along the center axis of the lower hub casting, within the depending tubular hub portion 31 from which it is insulated by an acrylic tube 38.
Rod 39 terminates at its lower end in a pin connector which projects beyond the lower end of tubular hub 31 and is adapted to be received by the center conductor socket of a coaxial-cable connector 42 (42). Secured to the lower end of the tubular hub 31 by screws 32 is a coaxial cable receptacle 41 type UG-58/A/U having a depending cylindrical flange portion externally threaded for receiving the internally-threaded outer-conductor collar of the coaxial-cable connector 42 (42). The rod 39 and its pin connector are suitably insulated from the receptacle 41.
In the existing antennae, type FA-530l, the connector 41 is normally connected to the cable connector 42 (42') of the coaxial input cable. However, to transform the existing antenna type FA5301 from narrow to broadband characteristics, the coaxial input cable is, in accordance with my present invention, disconnected from the receptacle 41 and a broadband adapter 60 is interposed between receptacle 41 and the input end of the coaxial input cable. The structure of the broadband adapter and the manner in which it is connected will now be described.
To add the broadband adapter 60 to an existing antenna type FA-5301, the set screws 29 are loosened and the entire antenna mast assembly is carefully lifted from the antenna mast 28, pulling and pushing the coaxial input cable 49 up along with the antenna. Mast 28 will ordi narily be 0 2 /2 standard weight galvanized pipe with a nominal CD. of 2.875". The collar portion of the connector, identified by the reference designation 42 (42), is uncoupled from the receptacle 41 and the pin of the antenna rod 39 is pulled out of the female socket portion of the connector.
The broadbander device, identified comprehensively by reference numeral 60, is now connected between the receptacle 41 and the connector, and the connector becomes relocated lower down the mast 28. This connector is seen at the bottom of the drawing in FIG. 2, and is identified as 42'.
The broadbander device comprises a straight section of coaxial cable 61 about which is coiled a length of helical coaxial cable 50 which function as the stub. The coaxial cable section 61 and the helical stub 50 are located within the bore of a section of tubing 131 of suitable material, such as brass, copper, silvered brass, etc. Tubing 131 has a diameter which allows it to be inserted into the antenna mast 28 and to abut against the lower end of the tubular hub 31 of the antenna lower hub casting.
The upper end of the section of coaxial cable 61 is provided with a connector 42 (similar to connector 42' referred to above) and adapted to couple the center conductor of coaxial cable 61 to the antenna lead-in rod 39 3 and to connect the outer conductor of coaxial cable 61 to the tubular hub 31.
The lower end of the broadbander device 60 is provided with a receptacle 141 similar to that of receptacle 41 located at the lower end of tubular hub 31. Receptacle 141 is secured to the lower end of the tubing 131 by screws 132. The center conductor of coaxial cable section 61 terminates at its lower end in a pin 161 which couples to the female inner portion of connector 42' of coaxial input cable 49.
At the lower end of helical coaxial stub 50, the center conductor of the stub is connected to the center conductor of the coaxial section 61, and the outer conductor of the helical coaxial stub 50 is connected to a brass grounding ring 51. Ring 51 is secured to the tubing 131 by a set screw 52. Thus, the outer conductor of the helical coaxial stub is in good electrical contact with the brass tubing 131.
As seen in FIG. 2, the helical coaxial stub 50 does not occupy the full length of the coaxial cable section 61 and the annular space above the helical stub is mostly occupied by a fiber insulator tube 63. The space between the lower end of the fiber tube 63 and the upper end of the helical stub 50 is filled with an insulating compound 64, such as Dow Corning Compound DC-S.
The length of the coaxial section 61 is 8 inches. The point of connection of the helical stub 50 to the coaxial section 61 is 12 inches from the dipole terminals at the location of the spacer 26. This is equal to .124 wavelength at 120 megacycles. The helical stub 50 is 34 /2 inches long, which is equivalent to .350 wavelength at 120 megacycles.
I have discovered by the relatively simple expediency of inserting the broadbanding device 60 just described to an existing circularly polarized antenna type FA-5301, the antenna may be transformed from a relatively narrow band into a broadband antenna having a voltage standing wave ratio versus frequency characteristic such as is illustrated in FIG. 3 by curve B.
Referring now to FIG. 3, curve A represents the voltage standing wave ratio (VSWR) versus frequency of the existing antenna type FA5301 prior to insertion of the broadbander device 60. This antenna has a voltage standing wave ratio of 1.7:1 measured at the end of a 50-foot length of RG-8/ U coaxial cable. The frequency range is 118-135 megacycles.
I have found that the voltage standing wave ratio versus frequency characteristic of the existing antenna FA-5301 can be substantially improved by the insertion of the broadbanding device 60. When the device 60 is connected, the voltage standing wave ratio versus frequency characteristic becomes that shown by curve B in FIG. 3. Curve B, as will be seen, represents a substantial improvement over curve A. In its improved form, the modified antenna has a voltage standing wave ratio of 13:1 and a frequency range of from 118 to 144 megacycles.
Having described my invention, I claim:
1. A broadbanding adapter for modifying existing VHF circularly polarized antenna operating in a frequency range which includes 120 megacycles, said adapter comprising a straight length of coaxial cable having a coaxial open-end stub wound helically thereabout and connected thereto near one end, and connector means for interposing said straight length of coaxial cable and its helical coaxial open-end stub between the input receptacle of the antenna to be modified and the connector at the input end of the coaxial input cable, the length of said helical coaxial open-end stub being substantially .350 wavelength at 120 megacycles and its point of connection being substantially .124 wavelength from the antenna terminals.
2. A broadbanding adapter for modifying existing mastmounted VHF circularly polarized antenna operating in a frequency range which includes 120 megacycles, said adapter comprising a length of conductive tubing adapted to fit within said antenna mast, and having within said tubing a straight length of coaxial cable having a coaxial shunt open-end stub wound helically thereabout and having the lower end of said stub connected to said straight length of coaxial cable near the lower end thereof, connector means for connecting the upper end of said straight length of coaxial cable to the input receptacle of the antenna to be modified, and connector means for connecting the lower end of said traight length of coaxial cable to the input end of the coaxial input cable, the length of said helical coaxial open-end stub being substantially .350 wavelength at 120 megacycles and its point of connection being substantiallly .124 wavelength from the antenna terminals.
References Cited UNITED STATES PATENTS ELI LIEBERMAN, Primary Examiner.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3487414 *||Jul 19, 1967||Dec 30, 1969||Booker Aylwin R||Omnidirectional antenna|
|US3518692 *||Aug 25, 1967||Jun 30, 1970||Gen Dynamics Corp||Orthogonal antenna system with multiple-channels|
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|US6441796 *||Jun 5, 2001||Aug 27, 2002||Spx Corporation||High power quadrapole FM ring antenna for broadband multiplexing|
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|US8618998||Jul 21, 2009||Dec 31, 2013||Applied Wireless Identifications Group, Inc.||Compact circular polarized antenna with cavity for additional devices|
|U.S. Classification||343/822, 343/864, 343/797|
|International Classification||H01Q21/26, H01Q21/24|
|Cooperative Classification||H01Q21/26, H01Q21/24|
|European Classification||H01Q21/26, H01Q21/24|