US2175254A

US2175254A - Wide-band short-wave antenna and support therefor

Info

Publication number: US2175254A
Application number: US190939A
Authority: US
Inventors: Philip S Carter
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1938-02-17
Filing date: 1938-02-17
Publication date: 1939-10-10
Anticipated expiration: 1956-10-10

Description

Oct. 10, 1939.

P. s. CARTER WIDE-BAND SHORTWAVE ANTENNA AND SUPPORT THEREFOR 2 Sheets-Sheet 1 Filed Feb. 17, 1938 TOTAL C(IRRENT 25% 56% 68% 75 DISTANCE FROMAPEX m TERMS OF LENGTH TRANSMITTER 0R RECE/ VER INVENTOR. I 7% 11 s. CARTER KIN ATTORNEY.

P. S CARTER Oct. 10, 1939.

WIDE-BAND SHORT-WAVE ANTENNA AND SUPPORT THEREFOR Filed Feb. 17, 1938 2 Sheets-Sheet 2 INVENTOR.

PHIL/P5. CARTER BY w! ATTORNEY.

Patented Oct. 10, 1939 UNITED STATES PATENT OFFICE WIDE-BAND SHORT-WAVE ANTENNA AND SUPPORT THEREFOR of Delaware Application February l'i, 1938, Serial No. 190,939

9 Claims.

The present invention relates to short wave antennas, particularly to a short Wave antenna which will present negligible reactance and practically constant resistance at its terminals over a wide frequency range, such as may be used in television transmission or reception, and more specifically to a method of and means for supporting such an antenna.

The type of antenna to which this invention relates is described in my copending applications, Serial Nos. 147,817, filed June 12, 1937; 188,821, filed February 5, 1938; and 187,594, filed January 29, 1938, and is a structure comprising a pair of surfaces of revolution in the form of cones placed so that their apices are adjacent each other. These conical surfaces of revolution may comprise metallic sheeting, or a plurality of conductors regularly distributed around and lying in the conical surface of revolution.

I have found that, by means of an antenna of the type described above, which gives the appearance of an hour-glass, the antenna will act as a pure resistance of substantially constant magnitude over a wide range of frequencies.

Such an antenna has been found to be especially desirable when the length of the transmission line feeder to the antenna is relatively long with respect to the wavelength, such as five lengths and greater. Several advantages of this particular type of antenna are: (1) It provides a flat resistance versus frequency characteristic with negligible reactance over an extremely wide range of frequencies, and (2) the resistance of the antenna at its terminals can be made to have almost any desired value in order to match the impedance of the transmission line without the use of external impedance matching circuits. This value of antenna resistance may be changed by varying the angle of revolution of the conical surface. It has been found that the use of external impedance matching circuits, which the antenna with which the present invention is concerned may avoid, narrows the frequency range.

One of the objects of the present invention is to provide a method of and means for supporting the conical antenna structures without deleteriously affecting the flat resistance versus frequency characteristic.

Another object of the invention is to provide means for supporting each conical surface of revolution of the foregoing type of antenna intermediate the ends thereof without using insulators.

Other objects, together with-the associated feat tures and advantages of the present invention, will appear from a reading of the following description, which is accompanied by drawings wherein:

Fig. 1 graphically illustrates the current and 5 electric intensity along the length of each conical surface of the antenna from the apex to the end for a conical surface whose length is approximately 0.36 wavelength;

Figs. 2, 3 and 4 illustrate various methods of 10 supporting the conical antennas when said antenna structures are made of metallic sheeting;

Fig. 5 illustrates a method of supporting a conical antenna structure when each conical surface of the antenna is composed of a plurality of Wires regularly distributed around. and lying in the conical surface; and

Figs. 6 and 7 illustrate other methods of supportingconical antenna structures having enclosed bases. 20

Referring to Fig. 1, which is given to illustrate the theory behind the location for the particular supports for the antenna, in accordance with the invention, there are illustrated two curves 1 and E plotted against the distance along 25 the surface of each cone from the apex thereof, in terms of percentages of. the length, for a conl cal surface whose length along the surface is 0.36 wavelength at the mid-frequency of the band. The curve I represents the total current 30 in the surface of the cone at any distance from the apex. The curve E represents the intensity of the electric field in a direction perpendicular to the surface of the cone for any'position measured from the apex of the cone. 35

It will be noted from an inspection of Fig. 1 that the maximum current is obtained along the length of each cone at a distance about 25% from Y the base, i. e., the large end, while the minimum intensity of electric field is obtained at a distance 40 about 32% in length from the base (large end). Consequently, it will be appreciated that the position of the external support for the antenna should be in the vicinity of the point of minimum electric intensity, so that current induced in the 45 support by the antenna will be a minimum. 7

Fig. 2 shows one arrangement for supporting a short wave, Wide frequency conical antenna in accordance with the invention. The antenna of this figure comprises two conical surfaces l and 50 2, placed end to end with their longitudinal axes in the same straight line, the apices being adjacent each other. The cones l and 2 are shown made of a metallic sheet material, energized and supported at their adjacent apices by a. pair of 55 concentric transmission lines TL which extend to suitable transmitting or receiving apparatus 3, here shown conventionally in box form. The inner conductors of the transmission lines TL are preferably rods or pipes which serve the dual purpose of energizing and supporting the cones at their apices.

From what has been said above, it will be appreciated that the desirable location for supporting each cone along its length is at a point of minimum intensity of electric field, which point occurs at a distance approximately onethird of the length of the cone'from the wide end thereof, for a length of cone along the surface equal to approximately 0.36 wavelength at the mid-band frequency. To achieve this support without the use of insulating material, I propose to placeinternally in each cone 2. metallic spacer 4 in the form of a wagon wheel at a location relatively near the point of external minimum electric intensity. This wagon wheel spacer should not be very near the end of the conical surface, which preferably is left open, inasmuch as it is desired that the location of the wagon wheel spacer be at a point of very low internal electric intensity. Spacer 4 is generally known in the construction field as a spider, and is formed with an aperture at its center. I have provided a pipe 5 of suitable dimensions in the interior of each cone which extends from the center of each spider 4 to the apex of the cone along the axis thereof. I have also provided at a point on the pipe 5 which is approximately at a distance from the base of one-third of the length of the cone, measured along the surface of the cone, a metallic pipe support 6 which extends through an aperture 1 of the cone to the roof or ground 8, as the case may be. It will thus be seen that each vertical pipe 6 supports its associated cone by virtue of its rigid connection to the horizontal pipe 5 along the axis of each cone, this pipe 5 in turn being firmly secured to the cone in its interior by reason of its connection at one end of a point near the apex of the cone, and at the other end to a metal spider 4. In actual practice, the apex of each cone is made of solid material so that the pipe 5 can be threaded into this solid portion.

In one construction actually tried out in practice, wherein an arrangement of the type illustrated in Fig. 2 was employed, the length of each vertical metallic pipe 6 was approximately onehalf wavelength at the mid-band frequency. The roof 8 was made of a metallic material. This particular height of the cones above the surface 8 was desired in order to cancel the vertical radiation. It will be understood, of course, that the invention is not limited to any particular height of antenna above ground or its supporting roof.

Fig. 3 illustrates another modification wherein the vertical metallic supports 6. electrically connect with the ends of the horizontal axial metallic pipes 5, in such manner that the overall distance of pipe 6 from ground, at the lower end of this pipe, to the point 9 on the wagon wheel or disc 4 is an odd multiple of one-quarter wavelength at the mid-band frequency, preferably three-quarters of a wavelength. It will be noted that the metallic pipe 5' which extends along the axis of each cone, projects out from the preferably open base a distance of one-eighth of a wavelength, at which point it is made fast to the vertical metallic pipe support 6, which extends vertically above the roof for a distance of about one-half wavelength. The wagon wheel or disc 4 is located in the interior of the cone at a distance approximately one-eighth of a wavelength from the base. Consequently, it will be evident that the total distance from the wagon Wheel 4 to ground or roof 8 is approximately three-quarters of a wavelength. This particular length, taken together with the fact that the effective diameter of the

supports

6, 5, is small compared to the radius of the base (i. e., widest portion) of the cone, tends to reduce current in the supporting metal to a low value. It will be appreciated, of course, that a connection between a radiating structure and ground, whose length is an odd multiple of one-quarter wavelength, presents extremely high impedance to the flow of energy over said connection at the frequency corresponding to this wavelength. It should be noted at this time that the length of each cone is approximately three-eighths of a wavelength at the mid-band frequency so that the distance of one-eighth of a wavelength from the spider 4 to the base of each cone is approximately one-third of the length of the cone.

Fig. 4 shows an arrangement which is similar to that of Fig. 2, except that the vertical support 6 is fastened at its upper end to the cone by means of a suitable flange l0 and bolts H. The horizontal pipe 5 and wagon wheel spider 4 shown in Fig. 2 is eliminated from the structure of Fig. 4. Because this particular arrangement produces a moderately detrimental effect upon the impedance frequency characteristic of the antenna, it is not preferred to use this particular structure.

Fig. '5 shows an arrangement wherein the cones of the antenna are made of a plurality of wires l2, l2 regularly distributed around a conical surface. The wires of each cone are maintained in suitable spaced relation by means of a metal spider 4 at each base, this spider in turn maintaining the horizontal axial pipe 5" in suitable position. Here again, the vertical metallic pipes 6 connect with the supports 5" at a location of minimum electric intensity along the cone.

Fig. 6 shows an arrangement wherein each cone is terminated in a hemisphere l2 for the purpose of decreasing wind resistance and for mechanical considerations, such as aiding in supporting the structure and in preventing snow, ice and water from entering the open base or large end of the cone. When such a hemisphere is used, then the overall dimensions along the surface of the cone and sphere will be somewhat greater than the previously indicated preferred value for each cone. In such a case, the support 6 may be connected directly to the associated hemisphere.

Fig. '7 shows another modification, wherein each cone is enclosed at its large end by another conical surface or dished-in portion l 3. Support 6 may be directly connected to the portion IE, or, if desired, to a spider located within the cone, in the manner indicated in Fig. 3, or to both.

It will be understood, of course, that the conical surfaces of revolution and the supporting structures therefor may take other forms without departing from the spirit and scope of the invention. For example, the base of each cone can be enclosed by a flat surface, instead of a hemisphere or a dished-in portion as shown in Figs. 6 and 7.

It will also be understood that the conical surfaces of revolution of my antenna may vary to some extent above and below the preferred 0.36 wavelength, in the manner described in my copending application Serial No. 187,594, filed January 29, 1938, and consequently the term approximately 0.36 wavelength is intended to cover a range of about 40% above and below 0.36 wavelength.

What is claimed is:

1. A short wave antenna having a substantially flat resistance versus frequency characteristic over a wide range of frequencies, comprising a conductive structure in the form of a conical surface of revolution, and means connected to the interior of said surface for supporting said structure intermediate the ends thereof at a point of substantially minimum intensity of electric field.

2. A short wave antenna having a substantially flat resistance versus frequency characteristic over a wide range of frequencies, comprising a conductive structure in the form of a conical surface of revolution, the length of said surface from apex to base being approximately 0.36 wavelength at the mid-band frequency, and means connected to the interior of said surface supporting said structure at a distance from the base along said surface approximately one-third of the length of said surface.

3. An antenna system in accordance with claim 2, characterized in this that said structure is composed of a metallic sheet of material.

4. An antenna system in accordance with claim 2, characterized in this that said structure is composed of a plurality of wires regularly distributed around and lying in said conical surface of revolution.

5. A short wave antenna having a flat resistance versus frequency characteristic over a wide range of frequencies, comprising two surfaces of revolution in the form of cones symmetrically located with respect to a common axis passing through their apices, said apices being adjacent one another, and having means connected to the interior of each of said surfaces for supporting each of said conical surfaces of revolution and passing through said surfaces at a point of substantially minimum intensity of electric field along said surfaces.

6. An antenna system in accordance with claim 5, characterized in this that said supporting means for each conical surface of revolution passes through said surface at a distance of approximately one-third the length of each conical surface along said surface from the base thereof.

7. A short wave antenna system having a flat impedance versus frequency characteristic over a wide range of frequencies, comprising two conductive structures forming radiator elements supported in insulated relation one to the other, and having the form of similar opposed conical surfaces, said elements having their axes in the same straight line in the horizontal plane, said axes being located a distance approximately one-half wavelength at the mid-band frequency above a conducting substantially planar surface, each of said elements having a length along the conical surface approximately 0.36 wavelength at the mid-band frequency, and means connected to the interior of each of said conical surfaces for supporting each of said conical surfaces and passing through said surfaces at a distance from the base thereof along the length of said surface approximately one-third of the length of said surfaces.

8. An antenna system in accordance with claim 7, characterized in this that said means includes a metallic spacer in the interior of said conical surface of revolution, and a metallic support from said spacer to said substantially planar surface, said support having an overall length from spacer to planar surface of approximately an odd multiple of one-quarter wavelength at the mid-band frequency.

9. A short wave antenna system having a flat impedance versus frequency characteristic over a Wide range of frequencies comprising two conductive structures forming radiator elements supported in insulated relation one to the other and having the form of similar opposed conical surfaces, said elements having their axes in the same straight line in the horizontal plane, said axes being located at a distance approximately one-half wavelength at the mid-band frequency above a conducting substantially planar surface, each of the said elements having a length along the conical surface approximately 0.36 wavelength at the mid-band frequency, and means including a metallic spacer in the interior of said conical surface of revolution and a metallic support from said spacer to said substantially planar surface for supporting each of said conical surfaces at a distance from the base thereof along the length of said surface approximately onethird of the length of said surfaces, said metallic support having an overall length from spacer to planar surface of approximately an odd multiple of one-quarter wavelength at the mid-band frequency.

. PHILIP S. CARTER.