US2149415A - Vertical antenna - Google Patents

Description

W. BERN DT VERTICAL ANTENNA March 7, 1939.

Filed July 24, 1937 m n m m T mm/om W A 15 coils and roof capacities.

Patented Mar. 7, 1939 PATENT OFFICE 2,149,415 VERTICAL ANTENNA Walter Berndt, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic in. b. 11., Berlin, Germany, a corporation of Germany Application July 24, 1937, Serial No. 155,447 In Germany August 1, 1936 6 Claims.

This invention is concerned with a broadcasting transmitting aerial designed toreduce the short range fading. With this end in view, it is known to employ vertical antennas whose elec- 5 trical length is over one-half wavelength /zk). i The dimensions of the electrical constants of these antennas are such that a current node will be produced a small distance above ground. It is upon the proper position or location of this 10 current node that the extent to which shortrange fading is diminished will depend. The fixing of the current node according to prior practice has mostly been effected by choosing suitable lengthsfor the aerials, say, by inserted 25 known in the prior art to usean extensible needle mounted upon the top of the mast. However, it has been ascertained in practice that the height above ground of the node will be but little altered by an extension'of the needle. Where 30 antennas with roof or top capacities are employed, a change in the diameter of the top ring is capable of insuring sufficient shift in the current node. But such a change cannot be brought about during actual operation for the reason that 35 the demounting of the old ring and the mounting of the new ring requires a good deal of time. In the case of antennas comp-rising built-in coils, it would finally be feasible to obtain shifts in the location of the current node by a variation in the number of turns in the coils. However, where large transmitter powers are involved, the tapping of encased or canned coils causes considerable difficulty, not to mention the fact that correct adjustment of the height of the node is 45 possible only with great difficulty.

In contrast with this prior art, the present invention is concerned with an arrangement adapted to secure a steady change in the height of the current node. According to the invention,

50 the radiating part of the antenna is furnished with means for altering the cross-section, and the point where such change in the cross-section is brought about may be shifted so as to vary its height above the ground.

Actual tests have shown that in the case of an However, this will antenna comprising two parts or members of dissimilar cross-section, the distribution of the current is a function of the point or place where a change of cross-section is effected. If this place is located below the current loop, there 5 results a comparatively great height in the location of the node (Fig. 1); but if the place where a change in the cross-section is elfected lies at the current loop, 1. e., at a voltage node (Fig. 2), then the position of the current node will be lower; while if the point of change of, crosssection is located above the current loop (Fig. 3),

this implies and results in the lowest position of the node. The greater the difference in cross section and thus of the characteristic impedance of the two halves of the antenna, the more will the node be displaced upon a shift of the point of cross-section.

The arrangement of the present invention offers the advantage that the same is not de zo pendent upon the provision of top or roof capacities and built-in coils, and that a change in the location of the node is accomplishable within a short time without the use of special accessories. The arrangement is useful also where 5 very large sending powers are involved, while an incidental merit of the present scheme is that it conduces to a decrease in the potential prevailing at the base end.

In the drawing:

Figs. 1, 2 and 3 are given merely for the purpose of exposition.

Figs. 4, 5 and 6 illustrate different embodiments of the present invention.

A few simple exemplified embodiments of the basic idea of the invention are illustrated in Figs. 4, 5 and 6. The antenna is suspended inside wooden tower T. The upper end consists of a single antenna cable or strand I. For the bottom part two, three or more atenna cables 2, with the same current or larger cross-sectional area, are used. For an expeditious shift of the current node, a third system 3 is provided which consists of two or more parallel Wires (indicated by dashed lines in the drawing), and these, above and below, are conductively connected with the fixed antenna conductors I and 2, if desired. The said third system may be raised or lowered, with a resultant shift in the point Where a change in the cross-section is occasioned. 5

A particularly great range of variation is obtained in Fig. 5, wherein the lower end or base of the antenna is in the form of an iron mast or girder M, and wherein the third system which conveniently consists of a great number of parallel wires 3 is so disposed that it is capable of being lowered into the interior of the mast or girder or else surrounds the mast. Also in this case, the said third system may be conductively associated with the iron girder and the antenna cable or strand l.

Another exemplified embodiment of the invention'is shown in Fig. 6, where the bottom or base end of the antenna tower consists of iron and serves as the lower antenna part. Erected upon this iron tower is a wooden framework T in'which the upper part of the antenna l is suspended.

The arrangement of this invention is not predicated upon the provision of. built-in coils and of roof or top capacities. But these means may be arranged as known in the art and as shown in Figs. 4-6. The general and broad idea underlying the invention is that a shiftable means to change the point of variation of cross-section is provided with a view to reducing short range fading effects, it being, fundamentally speaking, immaterial whether the upper part of the antenna has a smaller cross-section than the lower one, or vice versa. However, for electrical reasons it is recommendable to choose a form of antenna as shown in the drawing, that is, in which the cross-sectional area of the upper part is less than below.

What is claimed is:

1. Vertical antenna having an electrical length greater than one half the length of the operating wave and designed for reduced short-range fading, the radiant part of said antenna having a change of cross-section at one part of its length, and means for shifting the part where the change in cross-section takes place in its height above the ground.

2. Vertical sending antenna as claimed in claim 1, with the characteristic feature that the upper end consists of a single antenna conductor, the lower part of two or more conductors, and that a third parallel conductor arrangement is connected conductively with the others and, so disposed so as to be shiftable in height.

3. Vertical sending antenna as claimed in claim 1, with the characteristic feature that the top end consists of a single antenna conductor, and the lower end of an iron girder mast, and that a parallel conductor arrangement capable of being lowered in the bottom end is provided.

4. A vertical antenna having an electrical length greater than one-half the length of the communication wave, whereby a voltage nodal point exists in the length of said antenna, said antenna comprising two vertical sections of different cross-sectional areas arranged eifectively end to end, and means for effectively shifting the point in said antenna where a change of cross-section occurs, said means comprising an electrical conductor connected simultaneously to both of said Vertical sections and vertically adjustable in position over both said sections.

5. A vertical transmitting antenna having an electrical length greater than one-half the length of the communication wave, said antenna comprising two vertical sections of different crosssectional areas arranged effectively end to end, the upper section constituting a single wire, and means for effectively shifting the point in said antenna where a change of cross-section occurs;

said means comprising an electrical conductor connected simultaneously to both of said vertical sections and vertically adjustable in position over both said sections.

6. A vertical transmitting antenna having an" electrical length greater than one-half. the length of the communication wave, said antenna comprising two vertical sections of difierent crosssectional areas arranged effectively end to end,

connected simultaneously to both of said vertical sections, and vertically adjustable in position over both said sections.

WALTER BERNDT.

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