US3253279A

US3253279A - Bandwidth monopole antenna having low ground losses due to a circumferential ground ring

Info

Publication number: US3253279A
Application number: US255439A
Authority: US
Inventors: Robert L Tanner
Original assignee: TRG Inc
Current assignee: TRG Inc
Priority date: 1963-02-01
Filing date: 1963-02-01
Publication date: 1966-05-24
Anticipated expiration: 1983-05-24

Description

May 24, 1966 R. L TANNER 3,253,279

BANDWIDTH MONOPOLE ANTENNA HAVING LOW GROUND LOSSES DUE TO A CIRCUMFERENTIAL GROUND RING Filed Feb. 1, 1965 4 Sheets-Sheet 1 2055/27 L. T4 MvE/e INVENTOR.

d8 BY/M PRIOR ART A TTORNE) May 24, 1966 R. L TANNER BANDWIDTH MONOPOLE ANTENNA HAVING LOW GROUND LOSSES DU Filed FEb. 1, 1963 4 Sheets-Sheet 2 iii INVENTOR [9055/2 L. TA NNE Q A 7TORNEY May 24, 1966 R. 1.. TANNER BANDWIDTH MONOPOLE ANTENNA HAVING LOW GROUND LOSSES DUE TO A CIRCUMFERENTIAL GROUND RING 4 Sheets-Sheet 5 Filed Feb. 1, 1963 ROBERT A 774 lV/VER A 77'OR/ EV United States Patent Ofi Frce 3,253,279 Patented May 24, 1966 BANDWIDTH MONUPULE ANTENNA HAVING LUW GROUND LUSSES DUE TO A CIRCUMFER- ENTIAL GROUND RING Robert L. Tanner, Menlo Park, Calif, assiguor to TRG, Incorporated, Palo Alto, Calif., a corporation of New York Filed Feb. 1, 1963, Ser. No. 255,439 12 Claims. (Cl. 343849) This invention relates to antennas of the monopole type which are used for low frequencies and very low frequencies and more particularly to improvements there- This application is a continuation-in-part of application Serial No. 225,815, and now abandoned, for a Monopole Antenna by this inventor.

Radio waves at frequencies below 300 kc. are used for a number of specialized applications. They form the basis of long range radio navigation systems and long range communications systems because of the fact that they suffer relatively low propagation attenuation and are less affected by changes in ionospheric conditions than are waves or higher frequency. In addition, waves at very low frequencies (VLF)-in the vicinity of kc.have the useful property that they penetrate sea water to significant depths and are therefore useful for communication with submerged submarines.

A principal difficulty in the use of frequencies below 300 kc. is the expense of the antenna and ground systern required to reduce ground losses to acceptable values. Because the wave length is so large the antenna, even though it may be a very high tower, is still electrically small so that the radiation resistance is very low. The effective height is approximately /2 of the actual height if the antenna is a simple tower. If the antenna is top loaded the effective height may approach the actual height.

As an example, consider an antenna for operation at 15 kc. Assume the antenna to have an effective height of 200 meters which would require a tower 700 to 1000 feet high with substantial top loading. At this frequency the wave length equals kilometers (20,000 meters). It can be shown that for this wavelength an antenna having an effective height of 200 meters has a radiation resistance equal approximately to 0.16. Because the radiation resistance is so low, such an antenna can be obtained only if the loss resistance due to ground losses is reduced to a very low value. At the present time this is accomplished by i-mbedding in the ground a great number of copper ground wires which extend from the base of the antenna tower to a substantial distance from it. As a consequence, antennas for operating at this frequency range are very costly.

It is an object of the present invention to provide a novel monopole type antenna which effectuates a great reduction in cost while achieving a given efficiency.

Another object of the present invention is to provide a novel monopole antenna which has a substantially improved bandwidth characteristic without increasing the cost of said antenna.

Another object of the present invention is the provision of a novel structure for a monopole antenna.

Yet another object of the present invention is the provision of a monopole antenna having a unique structure whereby most of the ground losses and much of the cost of the installation of a ground system is eliminated.

These and other objects of the present invention may be achieved in an antenna arrangement utilizing a single tower supported by guy wires. Attached to the top of the tower are a plurality of radiating lines. Both guy wires and radiating lines are coupled to a large ring conductor so that the antenna effectively describes the shape of a circular cone. The ring is in contact with the earth. It may be either buried, laid out over the surface of the earth, or supported a very small distance above the surface. By installation of the ring and associated conductors in the manner to be described, the necessity for installation in the ground of wires radiating from the base of the tower to reduce ground losses is eliminated. Ground current density is considerably reduced by this arrangement, and ground losses minimized. In addition, the guy wires associated with the antenna support tower are connected in a manner to operate as large inductors which are excited and connected to the radiating wires to help resonate or tune the antenna, and to provide additional radiation from a loop radiation mode which augments the radiation from the normal electric dipole radiation mode of the antenna.

The novel features that are considered characteristic of this invention are set forth with particularly in the appended claims. The invention itself, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawings, in which:

FIGURE 1 is a schematic drawing of a conventional top loaded monopole antenna;

FIGURE 2 is a diagram showing distribution of ground current at the base of a conventional monopole antenna;

FIGURE 3 is a diagram showing distribution of current at the base of an antenna built in accordance with this invention;

FIGURE 4 is an antenna built in accordance with the teachings of this invention;

FIGURE 5 is a diagram showing the manner in which the supporting tower guy wires are utilized in accordance with the teachings of the invention;

FIGURE 6 is similar to FIGURE 5 but shows the guy wires interconnected in a manner to permit operation at lower frequencies;

FIGURE 7 is a view of a portion of the antenna showing the arrangement of the ground current distribution bus and the current equalizing reactors;

FIGURE 8 is a diagram showing a tapered wave guide which is useful in explaining the improved broadband properties in antennas built in accordance with this invention;

FIGURE 9 is a view of another arrangement for ground current distribution in accordance with this invention.

Reference is now made to FIGURE 1 wherein there is shown a schematic drawing of a conventional toploaded or umbrella antenna commonly employed for radiating LP or VLF signals. The antenna comprises a tower 10 which is connected to a transmitter 12. Top loading conductors 14 are connected to the top of the tower. The purpose of these conductors is to increase the effective height and capacitance of the antenna. Radiating out from the base of the antenna and also connected to the ground terminal of the transmitter 12, are radial ground conductors 16.

Current enters the ground system at the center of the radial ground connectors 16. Although most of the current flows in these conductors, a significant portion is carried in the ground itself, and this portion increases as the wave travels out from the base of the tower. Beyond the ends of the ground conductors all current is carried in the ground.

FIGURE 2 represents with arrows 18, the radial currents which flow at the base of a conventional monopole antenna such as is represented in FIGURE 1. FIGURE 2 is an approximately quantitative representation inasmuch as the spatial density (number per unit of transverse length) of the arrows is a measure of the ground current density.

FIGURE 3 represents the ground currents which flow at the base of an antenna which is constructed in accordance with this invention. The large circle represents a ground conductor ring 20 which, as will be shown subsequently herein, is a part of the antenna system of this invention. The arrows 22, represent the near-zone ground current. The total current in the two cases is approximately the same, but it is evident that the current density in FIGURE 3 is many times smaller. This results in part from the fact that the current entering the ground on the large diameter ring 20 is spread over a much greater circumferential distance. In addition, the near-zone base current in FIGURE 3 divides with part flowing toward the center and part flowing away from the center, while in FIGURE 2 the current is constrained by the geometry to flow outward exclusively. This results in an additional reduction in current concentration. In fact, it can be shown that if the beneficial effect of ground radial conductors is not present the ground loss resistance, in the case represented by FIGURE 2, may be more than 100 times as great as in the case represented by FIGURE 3. Thus, a rudimentary ground system consisting of a ground conductor ring 20, which may be a single wire as shown, or two or more spaced wires, gives lower ground losses than even an expensive and elaborate ground radio system for a conventional antenna.

Reference is now made to FIGURE 4 which is a drawing of an embodiment of this invention. A support tower 24 is held insulated from the ground by an insulating support 26. The support tower is held in place by conventional guy system consisting of outer guys respectively 30A, 32A, 34A, 30B, 32B, 34B, 30C, 32C, 34C, and inner guys respectively 36A, 38A, 40A, 36B, 38B, 40B, and a third set of inner guys, which are not shown. Typically there are 3 groups of guys spaced around the tower at intervals of 120. Typically also, the guys are insulated from the tower and from the guy anchors by strain insulators. In the embodiment of the invention, guy wires 32A through 32C, 34A through 34C, 36A through 36C, 38A through 38C, 40A through 40C, are anchored in this fashion namely by using strain insulators 44 which insulate the guys from the tower and from the guy anchors.

At this point it should be noted that another feature of this invention is a ground distribution bus ring 46 which circles the base of the antenna. Typically, this ground distribution bus ring is installed at a distance above the ground which is high enough to provide adequate ground clearance for personnel and equipment but low enough to be easily accessible for maintenance. The bus ring 46 may be a single conductor as shown but preferably is made of parallel multiple spaced conductors to reduce its inductance and increase its capacitance to ground as well as to reduce resistive losses. The bus ring may be supported directly from radiator support cables 52, to which it is connected, or it may be supported from a ring of auxiliary support poles.

At the top of the tower there is shown a radiator support insulator 48. This insulator has the purpose of providing mechanical support for radiator wires 50 and

upper guy wires

30A, 30B, and 30C, while electrically insulating them from the tower. All of the wires supported by the insulator are attached to a common con nection 49 at the top of the insulator, and are thus conductively connected together at that point. The radiator wires 50 are anchored to the ground by means of support cables -2. These support cables are insulated from the radiator wires 50 by strain insulators 44. The lower end of each one of the

guy wires

30A, 30B, 300, is mechanically connected to ground through a strain insulator 44 the other side of which is connected to the ground distribution bus ring 46 and also to current equalizer reactor 54. Similarly, each one of the radiator support cables 52 is connected to the ground distribution bus ring 46 and then to ground through a current equalizer reactor 54. It should be noted that ground connection is made to the ground conductor ring 20, which is buried in the ground at a distance which should not exceed a fraction of the skin depth at the frequency of excitation of the antenna. Preferably, the depth should be on the order of 0.2 the skin depth. In order to improve the performance of the ground conductor ring in reducing the ground losses by reducing the current density in the ground, additional short radial conductors 56 may be evenly spaced around the ground conductor ring 20, and are connected thereto at their centers. These short radial conductors are also positioned at each location at which a connection is made to the ground conductor ring by either one of the current equalizing inductances 54 or by the anchors for the guy wires. Connections between the ground distribution bus ring 46 and the ground conductor ring 20 should be made at intervals of two or three times the skin depth, and each connection should employ a current equalizing reactor of the proper value.

One terminal of the transmitter 58 is connected to the ground distribution bus ring 46, and the other terminal is connected to the guy wire 32A. A conductive connection is made between the guy wire 30A via conductor 60A to the guy wire A. Guy wire 40A is connected to the upper end of guy wire 32A by a conductor 62A. Effectively a one and one half turn inductance has been formed between connection point 49 and the transmitter 58 made up of guy wire 30A conductor 60A, guy wire 40A, conductor 62A guy wire 32A. The remaining guy wire sets are interconnected in a similar manner by conductors for forming inductors between connection point 49 and the ground current distribution bus 46. In this connection the

respective guy wires

32B and 32C are connected to the ring 46 by

conductors

65A, 65B.

Conductors

62A, 62B are respectively employed for connecting guy wire 40A to guy wire 32A, guy wire 40B to guy wire 32B. Not shown is a conductor for connecting guy wire 40C to guy wire 42C. FIGURE 5 is an elevation view of FIGURE 4 showing only the guy wires just described. For further simplifying FIGURE 5 the connections of the various guy wires on the ground side of the strain insulators 44 are all shown as being made directly to ground. Only two sets of guy wires are shown, the third set is similar in configuration to those shown.

Consider now FIGURE 4 together with FIGURE 5. It will be noted that the radiator wires are excited from the common connection with the guy wire 30A at point 49. At one instant in the radio frequency cycle of operation, charge which is stored on radiator wires 50 is a maximum. The antenna voltage is maximum and current flow in the antenna system is zero. As time goes on the charge stored on the antenna starts to flow ofif resulting in a current flow in the conducting paths to ground. FIGURE 5 shows two of the existing three paths along which currents represented by the

arrows

64, 64A, must flow. Tracing through these paths, it is seen that each one consists of a large one-and-one-half turn loop inductor consisting of

upper guy wire

30A, 30B respectively in series with conductive jumpers A, 60B respectively in series with

lower guy wires

40A, 40B, respectively in series with

conductive jumpers

62A, 62B, respectively in series with

upper guy wires

32A, 32B, and in the case of guy wire 32B a connection is made through the jumper 65A to the ground distribution bus ring 46 and therefrom to ground. The guy wire 32A is connected to the transmitter 58.

The large inductances so formed tune the antenna to operate at a relatively low frequency. Typically such an arrangement can be designed to tune a 600-foot antenna to a frequency of between 50 and 60 kilocycles. The tuning inductor achieved in this way has several distinct advantages. It utilizes necessary structure to achieve a tuning system of high efiiciency and virtually unlimited power rating. In addition, the arrangement described contributes to the radiation from the antenna. The inductors composed as described from the guy wires form loop antennas having large enough areas to have appreciable radiation resistance. Furthermore, it will be evident to those well skilled in the art that the three loops so formed, having their planes vertical but spaced in azimuth by 120 provide a composite radiation pattern identical to the electric dipole radiation pattern of the antenna. Radiation from the loops therefore augment the radiation from the dipole mode, thereby increasing both the efiiciency and the bandwidth of the antenna.

In FIGURE 4 the tower 24 is shown as being insulated from ground by a base insulator 26. In addition radiators 50 are connected to each other at the top but are shown insulated from the tower by support insulator 48. This is a preferred construction and yields the highest performance. It is possible however, to eliminate one or the other of the insulators in the interest of convenience and economy. For example, by eliminating insulator 26 the tower is grounded. This permits access to the tower by personnel even when the antenna is in operation. It simplifies installation of obstruction lights, eliminates need for a lightning arrestor gap at the base and provides lightning protection to the antenna system as a whole by enabling a grounded lightning rod to be installed so as to project substantially higher than any other part of the structure. In addition, the grounded tower arrangement enables the tower to be used for the installation of other antennas and equipment such as microwave or UHF relay equipment without in any way interfering with the opera tion of either the LP or of the additional equipment.

Grounding the tower by elimination of insulator 26 reduces the performance of the antenna somewhat however. The principal effect is a reduction of approximately in the available bandwidth, although ground losses are increased slightly also.

Alternatively, radiators 50 can be connected directly to the tower, eliminating insulator 48. This also reduces the performance of the antenna, but not as much as grounding the tower. In this case, however, there are not the compensating advantages of the grounded tower.

Each one of the current equalizer reactors 54 which separate the lower ends of the radial support cables 52 from ground are shown on the drawing as being inductors. They may also be capacitors, provided the values of the capacitors are properly chosen. If the operation of the antenna is limited to a relatively narrow frequency range, the capacitors are preferred. If the antenna is to operate over a very broad frequency range, there are some advantages to the use of inductors. One convenient way to achieve these inductors is to slip high permeability ferrite sleeves over the lower end of the cables 52. Alternatively, the cables can be broken by low voltage strain insulators and a separate equalizing reactor can be connected across each one of the insulators.

Reference is now made to FIGURE 6 which is similar to FIGURE 5 except that it shows an arrangement of interconnecting conductors between the guy wires in a manner to form, together with the guy wires, inductors having two and one-half turns. Such an arrangement permits operation at still lower frequencies with the same beneficial effect. It will be seen that there is a conductor 66A which connects the lower end of guy wire 30A to the lower end of guy wire 38A. A conductor 66B connects the lower end of guy wire 30B to the lower end of guy wire 38B. A conductor 68A connects the lower end of guy wire 32A to the lower end of guy wire 40A. A conductor 68B connects the lower end of guy wire 32B to the lower end of guy wire 403. A conductor 70A connects the upper end of guy wire 40A to the upper end of guy Wire 34A. A conductor 70B connects the upper end of guy wire 40B to the upper end of guy wire 34B. A conductor 72A connects the upper end of guy wire 38A to the upper end of guy wire 32A and a conductor 72B connects the upper end of guy wire 38B to the upper end of guy wire 32B. The two and a half turn loop inductors should be readily visible in FIGURE 6. The third set of upper and lower guy wires sets, not shown, are similarly interconnected.

In addition to the inductance provided by interconnected guy wires, additional inductance can be added in series with the connections 65, 65A, 658, which are used to connect the

respective guy wires

32B, 32C, to the bus, ring conductor. Also additional inductance can be added in series with the transmitter 58. Normally, it is sufiicient to add inductance in series with just one of these, most conveniently the transmitter, to achieve a desired measure of fine tuning control. It also is evident that if operation at higher frequencies is desired the

grounding connectors

65A, 65B, and the transmitter 58 can be connected di rectly in series with upper guy wires respectively 30A, 30B, 30C, to achieve one-half turn inductors with lower inductance. Still lower inductance can be achieved by disconnecting jumpers 66, 68, 70, 72, and connecting guy wires 30, 32, 34, in parallel by suitable interconnecting jumpers at their upper and lower ends.

In FIGURE 7 there is seen a view of a portion of the antenna showing one major segment 46A. of the ground distribution bus ring 46 and the associated structures. Currents represented by dashed

arrows

64 and 64A enter the ground distribution bus ring 46 at connection points respectively 74 and 76. At point 74, slightly less than half of the current flows to the left as current 64L, and an equal amount flows to the right as current 64R. A smaller amount of current 64G flows into the ground conductor 20 and thence into the ground. Part of the current 64R flows into the ground through the next succeeding current equalizing inductance 54 as current 64G thus the remaining current 64R flows on the bus ring to the succeeding connection of the next current equalizing inductance where still more current can flow into the ground. The remaining current continues on and some of it flows into the ground at the next equalizing inductance. Thus, the manner of current flow around the ring and into the ground through the equalizing inductances is seen.

By proper choice of the values of the reactive elements 54 or equalizing inductances, the currents flowing through these reactive elements can be equalized. As pointed out previously, the best performance may be obtained at a given frequency by the use of capacitors for elements 54 rather than the inductors which are shown. The values of these capacitors can be equal and should be chosen in conjunction with the inductance of the ground distribution bus ring 46 so as to make the length of the conductor 46 between connection points '74, 76, approximate a lumped-loaded transmission line of one-half wavelength effective electrical length. As mentioned previously, connections between bus ring 46 and ground conductor 20 should be on the .order of two or three times the skin depth preferably, but may be as great as four times the skin depth in the earth without seriously impairing the operation of the antenna.

Reference is now made to FIGURE 8 where there is shown a section of a tapered waveguide for the purpose of explaining the broadband properties of antennas built in accordance with this invention. It is common knowledge among those familiar with the properties of electromagnetic waves, that a common rectangular waveguide mode propagates freely in waveguidesin which the major dimension is greater than one-half wavelength but is cut off or strongly attenuated in waveguides which are smaller than this. This attenuation increases as the waveguide becomes progressively smaller than one-half wavelength.

4 In view of this fact it is evident that a wave having a wavelength will propagate freely to the right of the crosssectional area designated by the letters a, b, c, d, where Moreover, all frequencies higher than this will propagate freely and it may be said that when suitably excited the waveguide is infinitely broadband at frequencies above the frequency A ab. However, if the same range of frequencies is transmitted from cross section a'b'cd', those frequencies having wavelengths greater than Za'b will be quite strongly attenuated. Because the attenuation is reactive it can be compensated for, and essentially perfect transmission can be achieved by means of suitable tuning adjustments in the exciting structure. However, good transmission is attained at only a small range of frequencies, so that the structure is narrow band.

If the exciting structure is moved still further to the left to cross-sectional area a"b"c"d and the attempt is made to transmit frequencies whose wavelengths are the same as previously, the length of cut-off waveguide, through which these waves must pass, is greater and the attenuation, at least in the section from ab"cd" to a'bcd is even more severe. Again, transmission at a limited range of frequencies can be attained by tuning the exciting structure, but the available bandwidth is even narrower.

From the foregoing, it is evident that if we are faced with the problem of transmitting waves to the right in the Waveguide but restricted to that part of the guide to the left of section abcd in which to place our exciting structure, both bandwidth and efliciency will be greatest if we apply our excitation as far to the right in the guide as possible. Improved efficiency as Well as bandwidth results from the fact that energy transmitted through a waveguide below cut-oft" is accompanied by very large currents in the waveguide walls, resulting in excessive resistive power loss. The further below cut-off in the guide, the greater are the wall currents and the higher the loss.

To those acquainted with the principles of electromagnetic theory, the concept of free space as a sharply tapered waveguide is readily comprehensible. Wave modes closely analogous to the wave modes in the waveguide exist in free space. The free space waveguide might be said to taper out from the point where the transmitting voltage is applied with a solid angle of taper equal to 21r steradians, beyond the radius and hemispherical crosssection related to the wavelength in a manner not identical but closely analogous to the manner in which cross-section ab is related to the wavelength, the waves propagate freely. At smaller radii, corresponding to sections ab' and a"b in the waveguide the waves do not propagate freely and can be transmitted effectively only by the use of auxiliary tuning. As in the case of the waveguide, bandwidth and efiiciency are both maximized if the excitation is applied as close as possible to the cross-section corresponding to section ab in FIGURE 8 at which the waves begin to propagate freely. In terms of LF antennas, this means applying the excitation at maximum radius.

It is evident from the foregoing description that the present invention accomplishes exactly this, since by means of the circular ground distribution bus and ground ring, together with the loop inductances formed by the guy wires, the exciting currents and voltages are applied at the perimeter of the antenna (corresponding to crosssection a'b'c'd' in the tapered waveguide) rather than at the base of the tower (corresponding to cross-section a"b"cd"). In the ground area between the tower base and the antenna perimeter, which corresponds to the section of waveguide wall between sections a"b"c"d" and ab'c'd', current flow and attendant ground losses are drastically reduced.

FIGURE 9 shows another arrangement for reducing ground current losses while keeping the cost of the antenna installation down. The antenna, with which the ground current distribution structure shown in FIGURE 9 is used, is the same as that shown in FIGURE 4. To preserve simplicity in drawing and explanation, only so much of the antenna structure of FIGURE 4 is shown as to enable one to easily see the connections of the antenna structure to the ground current distributing structure.

Instead of using a bus ring 46 and equalizing reactances 54 as shown in FIGURE 4 to obtain current distribution and to reduce ground current density, a ground conductor ring is used consisting of multiple insulated conductors illustrated by the three

conductors

80, 82, 84, respectively, which are buried in the ground. These conductors each includes a central conductor respectively C, 82C, 84C, surrounded by dielectric material respectively 80D, 82D, 84D. The conductors form three concentric rings, and are placed in the ground substantially in the same horizontal plane. The ring is placed in the ground about at the same position with respect to the antenna tower as the position of the bus ring 46, that is just inside the circle defined by the anchored upper guy wires.

As shown in the drawing, the transmitter 58 has the terminal previously connected to the distributor ring 46, connected to the conductors 80C, 82C, 84C. The dielectric insulating

material

80D, 82D, and 84D, between the respective inner conductors and ground acts as the dielectric for capacitors with the inner conductors and ground as the capacitive plates. The capacitance thus established distributes the current into the ground equally all around the large circle at the periphery of the antenna whereby the ground current density is minimized, as was described in connection with FIGURE 3. Since the conductors 80C, 82C, 84C, replace the current distribution bus 46, and the capacitance between the conductor, which is insulated, and the surrounding earth, replace the equalizing reactances 54, both of these are eliminated. Thus, effectively, instead of inductors coupling a distributing bus to ground, the c oupling is made capacitive by this embodiment of the invention.

While the description herein refers to radiating conductors supported by a single tower and thereby describing a cone, the invention is not to be construed as being limited thereby since it is evident to those skilled in the art that other means or arrangements of support might be used. For example, multiple towers at the corners of a regular polygon might be used to support radiating conductors thereby describing a surface which resembles a conic frustum. Alternatively, the conductors might be supported from a rubber or plastic membrane inflated to form a hemisphere.

There has accordingly been described a novel, useful, antenna of the monopole type which has a construction and excitation such that the current concentration losses in the ground are minimized while the cost of construction of the antenna is minimized. In addition, the bandwidth of the antenna is improved by the use of the guy wires as radiating loops along with the usual radiating conductors.

I claim:

11. In a monopole antenna of the type having a plurality of radiators said radiators having one end connected to the top of a tower and extending outwardly therefrom and each of the other ends being supported from the ground at a distance from said tower by means of a strain insulator and a support cable, the improvement comprising a grounded closed loop conductor, means for connecting each of said support cables at spaced points around said conductor to be grounded thereby, means for exciting said plurality of radiators and means coupling said grounded loop conductor to said means for exciting said plurality of radiators for obtaining a ground current distribution pattern which emanates from. said ground loop conductor instead of from the base of said tower.

2. In a monopole antenna of the type wherein the antenna radiators are supported from a tower which is maintained vertical by means of a plurality of guy wires connected thereto, the improvement comprising means connecting said guy wires to form an inductance winding, means connecting one end of said inductance winding to said radiators, and means for applying excitation to the other end of said inductance winding.

3. A monopole antenna comprising a plurality of radiating wires, means for supporting said plurality of radiating wires above the earth to describe the surface of a cone with its apex pointed away from the earth, said supporting means including a plurality of guy wires, means for connecting said plurality of :guy wires in the form of an inductance winding, means connecting one end of the inductance winding formed by said plurality of guy wires to one end of each one of the radiating wires, and means for applying excitation to the other end of said inductance winding formed by said guy wires.

4. A monopole antenna comprising a plurality of radiating wires, means for supporting said plurality of radiating wires above the earth to describe the surface of a cone with its apex pointed away from the earth, said supporting means including a plurality of guy wires, means for connecting said plurality of guy wires in the form of an inductance winding, means connecting one end of the inductance winding formed by said plurality of guy wires to one end of all of the radiating wires, means for applying excitation to the other end of said inductance winding formed by said guy wires, and means conductively coupled to said means for exciting said plurality of radiating conductors and insulatingly coupled to all of said radiating conductors for securing a ground current distribution pattern which emanates from the periphery of said cone on the surface of the earth.

5. A monopole antenna as recited in claim 4 wherein said means conductively coupled to said means for exciting said plurality of radiating conductors and insulatingly coupled to all of said radiating conductors for securing a ground current distribution pattern comprises an insulated conductor ring buried in the earth at substantially the location of the base of said cone, said insulated conductor ring comprising a central conductor and a dielectric sheath, said means for exciting said plurality of radiating conductors being connected to said central conductor.

6. An antenna .as recited in claim 4 wherein said means for securing a ground current pattern which emanates from the periphery of said cone comprises a closed loop conductor buried in the earth and substantially conforming to the periphery of said cone, a current distribution bus, means connecting each one of said radiating wires insulatingly to said current distribution bus, means connecting said exciting means to said current distribution bus, and a plurality of reactance means a different one of which is connected between the point to which a different one of said radiating conductors is insulatingly connected on said current distribution bus and an adjacent point on said closed loop conductor buried in said ground.

7. The improvement in an umbrella antenna of the type having a plurality of radiators having one end supported from the top of a tower, each of said radiators extending outwardly from said tower and having its other end connected to a strain insulator and then through a support cable to ground, said improvement comprising a plurality of insulated conductor rings buried in'the earth, said insulated conductor rings being concentrically disposed with said tower at the axis and being placed at the periphery of the base of a cone described by said plurality of radiators and support cables, each said insulated conductor ring including a central conductor and a dielectric sheath, a source of excitation for said radiators, and means for connecting said source between said radiators and the central conductors of all of said conductor rings.

8. The improvement in an umbrella antenna of the type having a plurality of radiators having one end supported from the top of a tower, each of said radiators extending outwardly from said tower and having its other end connected to a strain insulator and then through a support cable to ground, said improvement comprising a circular ground current distribution bus mechanically supported from each one of the support cables, a source of excitation for said plurality of radiators, means for connecting said source between said radiators and said ground current distribution bus, and a plurality of impedance means connected between spaced points around said ground current distribution bus and ground, each of said impedance means having its values selected for equalizing the flow of current between said ground current distribution bus and ground.

9. An umbrella type antenna comprising a plurality of radiating conductors, means for supporting said plurality of radiating conductors above the earth in the surface of a cone having its apex pointed away from the earth, said means including a support tower, means for holding said support tower erect including at least one set of upper guy wires and one set of lower guy wires, said support tower having an upper end means at the upper end of said support tower for connecting together an upper end of each one of said radiating wires and one end of a first of said upper guy wires, a separate insulator attached to the other end of each of said radiating wires, a separate support cable connected between each one of said insulators and ground, means for insulatingly connecting one end of each of said guy wires except said first of said upper guy wires to said antenna support tower at spaced points between its top and bottom, means for insulatingly connecting the other end of said upper set of guy wires to ground at the periphery of said cone, means for insulatingly connecting the other end of said lower set of said guy wires to ground, a first conductor connecting the other end of said first of said upper set of guy wires which is closest to ground to other end of a first of said lower set of guy wires which is closest to ground, a second conductor connected between the other end of said first of said lower set of guy wires and the end of a second of said upper set of guy wires which is closest to said antenna support tower, and means for applying excitation to the other end of said second one of said upper set of guy wires which is closest to ground.

10. An umbrella type antenna comprising a plurality of radiating conductors, means for supporting said plurality of radiating conductors above the earth in the surface of a cone having its apex pointed away from the earth, said means including a support tower, means for holding said support tower erect including at least one set of upper guy wires and lower guy wires, said support tower having an upper end, means at the upper end of said support tower for connecting together an upper end of all of said radiating wires and one end of a first of said upper guy wires, a separate insulator attached to the other end of each of said radiating wires, a separate support cable connected between each one of said insulators and ground, means for insulatingly connecting each of said guy Wires except said first of said guy wires to said antenna at spaced points between its top and bottom, means for insulatingly connecting said upper set of guy wires to ground at the periphery of said cone, means for insulatingly connecting the lower set of said guy wires to ground, a first conductor connecting the end of said first of said upper set of guy wires which is closest to ground to the end of a first of said lower set of guy wires which is closest to ground, a second conductor connected between the other end of said first of said lower set of guy wires and the end of a second of said upper set of guy wires which is closeset to said antenna, means for applying excitation to the end of said second one of said upper set of guy wires which is closest to ground, and means connected to said antenna for securing a ground current distribution which emanates from the periphery of said cone at the surface of the earth, said means including a ground current distribution bus in the form of a closed loop conductor connected to each one of said support cables substantially at the periphery of said cone, means connecting said means for applying excitation to said ground current distribution bus, a second conductor in the form of a closed loop which is buried in the ground at the periphery of said cone, and a plurality of reactance means a different one of which couples said current distribution bus to said closed loop conductor buried in said earth at the location at which attachment is made to said support cables.

11. An antenna as recited in claim 10 wherein there are a plurality of upper and lower sets of guy wires, said plurality of upper and lower sets of guy wires being spaced around said antenna tower for maintaining it erect, means for connecting one end of a first guy wire in each of said upper sets to said means at the top of said antenna tower for interconnecting with said ends of said radiating wires, means for insulatingly connecting one end of all of said guy wires in said upper and lower sets except said first guy wires to said support tower, means for insulatingly connecting the other end of all said guy wires in said upper and lower sets to ground, a first connecting conductor for each upper and lower set of guy wires for connecting the lower end of each said first guy wire in each said upper set to the lower end of a first guy wire in each said lower set, a second connecting conductor connected between the upper end of each said first guy wire in said lower set and the upper end of a second guy wire in each said upper set, and means for connecting the lower end of each said second guy wire in said upper set to said current distribution bus.

12. An umbrella ty-pe antenna comprising a plurality of radiating conductors, means for supporting said plurality of radiating conductors above the earth in the surface of a cone having its apex pointed away from the earth, said means including a support tower, means for holding said support tower erect including at least one set of upper guy wires and lower guy wires, said support tower having an upper end, means at the upper end of 40 said support tower for connecting together an upper end of all of said radiating wires and one end of a first of said upper guy wires, a separate insulator attached to the other end of each of said radiating Wires, a separate support cable connected between each one of said insulators and ground, means for insulatingly connecting one end of each of said guy wires except said first of said guy wires to said support tower at spaced points between its top and bottom, means for insulatingly connecting the other ends of each of said upper set of guy wires to ground at the periphery of said cone, means for insulatingly connecting the other ends of the set of lower guy wires to ground, a first conductor connecting the end of said first of said upper set of guy wires which is closest to ground to the end of a first of said lower set of guy wires which is closest to ground, a second conductor connected between the other end of said first of said lower set of guy wires and the end of a second of said upper set of guy wires which is closest to said antenna, means for applying excitation to the end of said second one of said upper set of guy wires which is closest to ground, and means connected to said antenna for securing a ground current distribution which emanates from the periphery of said cone at the surface of the earth including a plurality of conductor rings being concentrically disposed with said tower at the axis and being at the periphery of the base of said cone, each said conductor ring including a central conductor and a dielectric sheath, and means connecting said means for applying excitation to the central conductors of said conductor rings.

References Cited by the Examiner UNITED STATES PATENTS 768,005 8/1904 Stone 343-890 945,475 1/1910 Pfund 343-849 958,209 5/1910 Arco 343-847 1,214,591 2/1917 Reuthe 343-847 1,595,166 8/1926 Scheller 343-845 2,263,460 11/1941 Gerth et a1, 343-875 2,473,377 6/1949 Koch 343-849 2,527,609 10/1950 Willoughby 343-860 2,746,040 5/1956 Martin 343-846 2,998,604 8/1961 Seeley 343-874 FOREIGN PATENTS 299,766 12/ 1920 Germany. 176,803 7/1923 Great Britain.

HERMAN KARL SAALBACH, Primary Examiner.

45 W. K. TAYLOR, P. L. GENSLER, Assistant Examiners.

Claims

1. IN A MONOPOLE ANTENNA OF THE TYPE HAVING A PLURALITY OF RADIATORS SAID RADIATORS HAVING ONE END CONNECTED TO THE TOP OF A TOWER AND EXTENDING OUTWARDLY THEREFROM AND EACH OF THE OTHER ENDS BEING SUPPORTED FROM THE GROUND AT A DISTANCE FROM SAID TOWER BY MEANS OF A STRAIN INSULATOR AND A SUPPORT CABLE, THE IMPROVEMENT COMPRISING A GROUND CLOSED LOOP CONDUCTOR, MEANS FOR CNNECTING EACH OF SAID SUPPORT CABLES AT SPACED POINTS AROUND SAID CONDUCTOR TO BE GROUNDED THEREBY, MEANS FOR EXCITING SAID PLURALITY OF RADIATORS AND MEANS COUPLING SAID GROUNDED LOOP CONDUCTOR TO SAID MEANS FOR EXCITING SAID PLURALITY OF RADIATORS FOR OBTAINING A GROUND CURRENT DISTRIBUTION PATTERN WHICH EMANATES FROM SAID GROUND LOOP CONDUCTOR INSTEAD OF FROM THE BASE OF SAID TOWER.