JPH0642608B2 - Mid-wave broadcasting transmission antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION a. TECHNICAL FIELD The present invention relates to a transmission antenna used for medium-wave broadcasting.

b. Conventional technology Conventionally, a so-called tower antenna using a truss pillar or a steel tube pillar having a height corresponding to 1/4 wavelength or 1/2 wavelength of broadcast waves as a radiator has been widely used as a transmitting antenna for medium-wave broadcasting. . Moreover, in order to cover a deafness area in a remote area of a mountain, a small-scale antenna that is smaller than 1/4 wavelength of a transmitted wave may be used.

In recent years, there is a growing tendency to build skyscrapers in urban areas, but among the medium-wave broadcast waves, the radio waves of broadcasting stations that use the high frequency band tend to be more difficult to hear in urban areas with a large population. . Also, there are many cases of interference with broadcasting from overseas. On the other hand, in order to make broadcasts heard by residents living overseas from Japan, it is desired to develop a transmitting antenna for medium-wave broadcasting, which has a strong directivity especially in the high elevation direction at night.

c. DISCLOSURE OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION As a measure for solving the above problems, there is no method other than to use stronger transmission power or to use an antenna having a stronger radiation capability than in the past. . However, in order to increase the transmission power, not only a large amount of cost is required to manufacture the transmitter, but also the ordinary cost of power is increased. Therefore, the only solution is to develop a transmitting antenna with a stronger radiation capacity than before.

In addition, if it is desired to broadcast abroad in domestic airtime (for example, at midnight), switch the normal antenna configuration without constructing a directional antenna with a high elevation angle apart from the normal antenna. It is convenient if the operation can be changed to achieve the purpose.

In order to obtain a transmitting antenna with a strong radiation ability,
There is no alternative but to use a higher antenna than a conventional antenna (about 1/2 wavelength in height) or to place many conventional antennas on the ground. However, placing a large number of antennas on the ground requires a large amount of money, which is not realistic. Therefore, it is realistic to devise a method to increase the radiation capacity by using a high antenna. With technology, it is possible to construct an iron pillar with a height of about 500 m above the ground without much difficulty. By the way, broadcast wave 1000
For KHz radio waves, one wavelength is 300 m,
It is easy to build an iron pillar with a height corresponding to the wavelength.
Moreover, if the iron pillars are of the grounded type, the construction will be even easier.

The present invention has been made in consideration of such various circumstances, and an object thereof is to use one iron pole having a height corresponding to one wavelength of a broadcast wave and By attaching auxiliary conductors and switches that are relatively small in size with a height of two wavelengths, the radiating ability is strong and the vertical plane directivity is changed without changing the main structure of the grounded antenna. Another object of the present invention is to provide a transmitting antenna for medium-wave broadcasting that can be used for.

d. Means for Solving the Problems In order to achieve the above-mentioned object, in the present invention, (a) the height is equivalent to one wavelength of a broadcast wave, and the base is erected on the ground and grounded. An iron pole, and (b) a length 1/4 whose upper end is connected to a portion at a height of 1/4 wavelength from the base of the iron pole, and which is arranged to face the iron pole in parallel.
With a first conductor of a wavelength, (c) parallel to the iron pillar and on an upward extension line of the first conductor facing a portion from the base of the iron pillar to a height of 1/2 wavelength from a height of 1/4 wavelength. A second conductor having a length of 1/4 wavelength, which is arranged so as to match and is connected to the first conductor through an insulator, and (d) is insulated from the first conductor and the second conductor, and A third conductor having a length of 1/2 wavelength which is erected on the ground in parallel to the ground, and (e) a first switch which electrically connects the lower end of the second conductor and the iron pole and the first conductor, (f) a second switch that electrically connects the upper end of the second conductor and the upper end of the third conductor, and (g) one of the lower end of the first conductor and the lower end of the third conductor. To the ground to supply the transmission power to the other end, or a transmission circuit that selectively operates to supply the transmission power to the two lower ends thereof, respectively. Provided, (h) ground the lower end of the first conductor, and connect the lower end of the second conductor with the first switch to the height 1/4 wavelength portion of the iron pillar and the upper end of the first conductor, By connecting the upper ends of the second conductor and the third conductor to each other in the second switch, and feeding only to the lower end of the third conductor, as a low-angle radiation antenna, (i) in the first switch The lower end of the second conductor is connected to the height 1/4 wavelength portion of the iron pillar and the upper end of the first conductor, and the upper ends of the second conductor and the third conductor are connected to each other by the second switch, While grounding the lower end of the third conductor, power is supplied only to the lower end of the first conductor to form a high-angle radiation antenna, or (j) the first and second switches are both opened to open the first conductor. The two conductors are electrically separated from the iron pillar, the first conductor and the third conductor. A high elevation angle is obtained by supplying electric power from the respective lower ends of the first conductor and the third conductor, appropriately selecting the ratio of the electric power supplied to the first conductor and the third conductor, and supplying electric power to both of them. It is used as an anti-fading antenna that emits broadcast waves with suppressed radiation in the area.

e. Operation First, before describing the embodiments of the present invention, the operating characteristics of the antenna, which is the technical basis of the present invention, will be described.

FIGS. 1 (I) and (II) show a transmitting antenna (vertical antenna) 3 for medium-wave broadcasting, which is formed by stacking two linear conductors 1 and 2 on top of each other. Is 1/2 of one wavelength of the broadcast wave, and the height of the antenna 3 is set equal to one wavelength. That is, in FIG. 1, ▲ ▼ = ▲ '▼ = 1 / 2λ (λ: one wavelength of broadcast wave).

Here, the amplitude I is applied to the straight conductor 1 which is the upper half of the antenna 3.
_{When a} standing wave current having a sinusoidal distribution of _{1 and} a standing wave current having a sinusoidal distribution having an amplitude of I ₂ are generated in the lower half linear conductor 2, the angle θ is inclined from the root of the antenna 3 with respect to the vertical line. The electric field strength E (θ) generated at a distant point in the direction (the distance from the base of the antenna 3 is γ ₀ ) considers a mirror image of the ground, Given in.

However, γ ₀ and λ are expressed in meters I ₁ and I ₂ are expressed in amps When cos and sin are calculated, π is set to 180 °. Note that the function D (θ) of θ, which indicates directivity, is expressed by excluding K on the right side of the above equation (1). D
(Θ) is usually expressed by standardizing so that the value of the maximum directivity is 1.

Here, the directivity curve when I ₂ = kI ₁ and the value of k is changed between −2 and 2 is as shown in FIG. The horizontal axis in Fig. 3 is θ
Not π / 2−θ, that is, the elevation angle from the horizontal direction is graduated in degrees. Further, D (θ) is scaled on the vertical axis.

The directivity changes as follows depending on the value of k.

(i) In the case of k = 2 Radiation is mainly concentrated in the horizontal direction remarkably stronger than the conventional one, and radiation at high elevation angles of 50 ° to 60 ° is extremely small. Therefore, it becomes a fading prevention antenna.

(ii) When k = 0 Strong radiation is emitted near the horizontal direction and at an elevation angle of 40 °. However, when the elevation angle is 40 °, the electric field strength is about 70% in the horizontal direction. Listeners within the fading zone and listeners beyond the fading zone can be provided good service at night.

(iii) When k = -1 Radiation is concentrated mainly at an elevation angle of 30 °, and horizontal radiation is significantly suppressed. Suitable for use in overseas broadcasting at certain times.

(IV) When k = -2 Radiation is concentrated both in the horizontal direction and near an elevation angle of 30 °. Contrary to the case of (ii) above, in the horizontal direction, the electric field strength is higher than that at an elevation angle of around 30 °. It is about 60%.

By the way, since the apex A shown in FIG. 1 is at the ground height corresponding to one wavelength, this is the Yagi antenna for relay or
If you install a parabolic antenna and use it for outdoor broadcasting,
There are few opportunities for tall buildings to get in the way. However, because of this, the capacitance at the tip of the antenna is added, and the current distribution rises upward, and as shown in Fig. 2, there is a small CE portion of one wavelength left near the ground. Since the influence is not so large as shown in FIG. 4, it will not be described below.

Next, how to use one antenna to give various vertical plane directivities as shown in FIG. 3 will be discussed with reference to FIG.

In FIGS. 5 (I), (II) and (III), reference numeral 4 designates a base grounding iron pole having a height corresponding to one wavelength λ of the broadcast wave. The iron pillar 4 is appropriately grounded at the base point C at the lower end thereof and has the following dimensions.

▲ ▼ = λ / 2 ▲ ▼ = λ / 4 ▲ ▼ = λ / 4 Further, 5 is a first arm bar horizontally attached to the D point of the iron pillar 4, and 6 is a tip E of the first arm bar 5. It is a first conducting wire of length λ / 4 that is connected and pulled down to the ground in parallel with the iron pillar 4, and the length of the above-mentioned first arm 5 is configured to be extremely shorter than one wavelength λ. There is. The lower end G of the first conducting wire 6
May be grounded or may be supplied with power from here.

In the case of FIG. 5 (I), the first arm 5 is attached to the point B of the iron pillar 4.
A second armpiece (not shown in FIG. 5), which is slightly longer than this, is attached horizontally, and both ends are insulated with an insulator between the middle part of this second armpiece and the tip E of the first armpiece 5. EF so that the second conducting wire 8 having a length of λ / 4 is aligned with the upward extension of the first conducting wire 6.
It is stretched between them. Then, from the tip of the second arm, a third conductor 9 of length λ / 2 with an insulator inserted at the upper end is pulled to the ground in parallel with the iron pillar 4, the first and second conductors 6 and 8. It has been lowered. The lower end H of the third conducting wire 9 may be grounded or may be supplied with electric power.

The operation of the antenna having the above components will be described in detail for each case shown in FIGS. 5 (I), (II) and (III).

In the case of FIG. 5 (I) (a) The lower end G of the first conducting wire 6 is grounded (b) The lower end E of the second conducting wire 8 is connected to the upper end of the first conducting wire (c) The upper end F of the second conducting wire 8 is Connected to the upper end of the third conductor 9 (d) Power is supplied from the lower end H of the third conductor 9 by the transmitter T. In the case of such a configuration, the power supplied from the transmitter T to the lower end H of the third conductor 9. Flows upward along the third conductor 9 and then from the point F along the second conductor downwards to E
Although it reaches the point, since the G point is grounded at ▲ ▼ = λ / 4, the impedance is ∞ as seen from the E point to the G point.
Similarly, for the lower end portion DC of the iron pole 4, the impedance from the point D to the point C is also ∞. Therefore, the electric power travels upward from point D through point B to point A, and reverses along the original electric path even if reflected at point A. As a result, a standing wave is generated, and at the moment when a sinusoidal current is generated in the AB portion of the iron column 4 in the arrow direction, the BDEF portion (length λ
Currents in opposite directions are generated as indicated by the arrow in / 2).
Therefore, there is no radiation from this part. On the other hand, the third conductor 9
A current having a sinusoidal distribution in the same direction as that of the AB portion flows through each of them.

Thus, the case where k in I ₂ = kI _{1 in} the case of FIG. 1 (I) is 1 is realized by the configuration shown in FIG. 5 (I).

In the case of FIG. 5 (II) (a) Power is supplied from the lower end G of the first conducting wire 6 by the transmitter T. (ii) The lower end of the second conducting wire 8 is the upper end of the first conducting wire 6 and the tip of the first arm 5 Connected to E. (C) The upper end of the second conductor 8 is connected to the upper end F of the third conductor (D) The lower end H of the third conductor 9 is grounded. The electric power supplied to the lower end G of the electric current flows upward along the first conducting wire 6. However, since the tip of the EFH (length 3 / 4λ) is grounded, the impedance when looking from the point E to the point F is ∞, so that power is not supplied to the EFH portion. Moreover, since the length of the DC portion of the iron pillar 4 is λ / 4 and the lower end C thereof is grounded, no electric power is supplied to the DC portion. Therefore, the electric power proceeds to the point A through the points D and B, and reversely travels in the original electric path reflected even at the point A,
As a result, a standing wave with a sinusoidal distribution is generated in the AB and BDEG portions. The current directions are opposite to each other as indicated by the arrow.

Thus, k in I ₂ = kI _{1 in} the case of FIG. 1 (II) is −1.
The above case is realized by the configuration shown in FIG.

In the case of FIG. 5 (III) (a) Both upper and lower ends of the second conductor 8 are opened (a) Currents of opposite phases are applied from the transmission circuit 10 to the lower end G of the first conductor 6 and the lower end H of the third conductor 9. Supply (c) Transmitter circuit 10 is a coil excited by transmitter T
L ₁ and a coil L _2, which is electromagnetically coupled to the coil L _1, a capacitor C ₁ for alignment, C ₂ and the configuration should be noted that by grounding the middle portion of the coil L ₂ 2 single coil L _3, L ₄ And eggplant

In the case of such a configuration, a current flows through the ABC portion of the iron pillar 4 and the first conducting wire 6 in the arrow direction, and a standing wave is generated. In this case, since the point C is grounded and ▲ ▼ = λ / 4, the impedance looking at the point C from the point D is ∞. Therefore, no current flows in the lower portion of the iron pillar 4, that is, the DC portion.

Since the second conductor 8 is open at both ends and has a length of λ / 4,
Very little current is induced in this second conductor 8,
This existence can be ignored.

When a current is generated downward in the BDEG portion (length λ / 2) as indicated by an arrow, a current flows upward in the third conductor 9 as indicated by an arrow, and a standing wave having a sinusoidal distribution as indicated by a dotted line is generated. .

By changing the position of the ground tap of the coil L ₂ , the number of turns of the coil L ₄ is made larger than that of the coil L ₃ , and the power supplied to the third conductor 9 is made smaller than the power supplied to the first conductor 6. It can be increased, for example, I ₂ −I ₁ ′ = 2I ₁ (corresponding to I ₂ = 2I ₁ in FIG. 1 (I)), where I ₁ ′ is the amplitude of the standing wave current flowing in the BDEG portion. It is possible to

Thus, the case where k of I ₂ = kI ₁ is 2 is shown in FIG.
It is realized by the configuration shown in I).

e. Embodiment Next, a first embodiment of the present invention will be described with reference to FIGS. In these figures, the same members and parts as those in FIG. 5 are designated by the same reference numerals.

FIG. 6 shows the structure of the transmitting antenna for medium-wave broadcasting of this embodiment, in which the iron pillar 4 having a height corresponding to one wavelength of the broadcasting wave is erected vertically on the foundation 11. The base portion (lower end) C of the iron pillar 4 is grounded. And it is supported by this iron pillar 4 and many branch lines 12. In addition, each branch line 12
A plurality of branch line insulators 13 are respectively inserted and arranged so as not to disturb the radiation of the iron columns 4 and a group of lines to be described later, and the lower ends of the respective branch lines 12 are held to the ground by anchor blocks 14.

Further, the first arm 5 which is extremely shorter than 1λ is attached to the portion D having a height of λ / 4 from the lower end C of the iron pillar 4, and the first arm 5 is horizontally fixed by the arm support strut 15. ing. Further, the second arm 7 is attached to the portion B at a height of λ / 2 from the lower end C of the iron pillar 4, and the second arm 7 is attached by the arm support support 17.
Is fixed horizontally.

At the tip E of the first arm 5 described above, the first conducting wire 6 having a length of λ / 4 is provided.
The upper end of is connected, and the first conducting wire 6 is pulled down in parallel to the iron pole 4 and its lower end G is guided into the switch / matching box 18 of the transmitting circuit 10 described later.

Further, between the tip E of the first arm 5 and the center J of the second arm 7, a second conductor 8 having a length λ / 4, whose both ends are insulated by insulators 19 and 20 for retaining conductors, is used as an iron pillar. It is stretched so as to be parallel to 4 and to coincide with the upward extension line of the first conducting wire 6. Further, the upper end of the third conductor 9 is attached to the tip F of the second arm 7 via the insulator 21, and pulled down to the ground so as to be parallel to the iron pillar 4 and the first and second conductors 6 and 8. The lower end H is a switch. It is guided into the matching box 18.

Further, the lower end of the second conductor 8 is provided with a first switch as needed.
It is configured to be electrically connected to the iron pillar 4 through the first arm 5 by S _1, and the upper ends of the second conducting wire 8 and the third conducting wire 9 are connected to the second switch S if necessary. ₂ is configured to be electrically connected. That is, the first switch S ₁ and the second switch S ₂ are composed of movable pieces 22 and 23 and expandable insulators 24 and 25, as clearly shown in FIG. They are attached to 5 and 7, respectively. The expandable insulators 24 and 25 are driven by switch drive devices 26 and 27 which are remotely operated from the ground station. As the metal fitting 28 for retaining the second and third conductors 8 and 9 on the insulators 19, 20 and 21, a crimp terminal or other known material is used.

On the other hand, the relay parabolic antenna 29 (see FIG. 6) attached to the upper end A of the iron pole 4 can freely remote-control the beam direction from the ground station.

FIG. 8 shows the internal structure of the switch / matching box 18, in which S ₃ and S ₄ are double-pole double-throw switches, and S ₅ is a single pole and has any of three contact points. , M ₁ , M ₂ , M ₃ are matching switches, L ₁ , L ₂ ,
L ₃ and L ₄ are coils, C ₁ and C ₂ are matching capacitors, T is a transmitter, and 30 is a feeder line.

Then, depending on the operation of the switches S _{1 to} S ₄ , the following 3
It can be switched to two different states (i) to (iii).

(I) The switches S ₁ , S ₂ are closed, and the switches S ₃ , S ₄ and S ₅ are closed.
8 is switched as shown by the solid line in FIG. 8, the output of the transmitter T is supplied to the lower end H of the third conductor 9 through the feeder line 30 and the matching unit M ₁ . On the other hand, the lower end G of the first conducting wire 6 is grounded.

Thus, the state shown in FIG. 5 (I) is obtained. In this case, a radio wave having a strong vertical plane directivity is emitted in the low elevation angle region.

(Ii) to close the switches S _1, S _2, the switch S ₃ tilted to the left as indicated by the solid line in FIG. 8, tilted to the right to indicate the switch S ₄ by the one-dot chain line, and the switch S ₅ Is connected to the terminal on the left side as shown by the alternate long and short dash line, the output of the transmitter T passes through the feeding line 30 and the matching unit M ₂ and the lower end G of the first conducting wire 6 is connected.
Is supplied to. On the other hand, the lower end H of the third conducting wire 9 is grounded.

Thus, the state shown in FIG. 5 (II) is obtained. In this case, a radio wave having a strong vertical plane directivity is emitted in the high elevation angle region.

(Iii) Open the switches S ₁ and S ₂ , tilt the switches S ₃ and S ₄ to the right side as shown by the chain line in FIG. 8, and
When the switch S ₅ is connected to the right terminal as shown by the broken line, the output of the transmitter T is supplied to the coil L ₁ through the feeder line 30 and the matching unit M ₃ . On the other hand, it is connected to the coil L _3, L ₄ and the lower end H of the lower end G and the third conductor 9 of the first conductor 6 respectively via the capacitors C _2, C _1. In this case, the ground tap point of the coil L ₂ is grounded, but by changing this position, the ratio of the inductances of the coils L ₃ and L ₄ and thus the power supplied to the first and third conductors 6 and 9 can be changed. You can adjust the ratio.
The second conductor wire 8 is open at both ends and its length is 1 /
Since it is 4λ, the current induced in it is negligible.

Thus, if adjustment is made so that k = 2, it will be as shown in FIG.
In the state of I), the broadcast wave is emitted in which the radiation in the high elevation region is suppressed. As a result, it operates as a fading prevention antenna.

According to the medium-wave broadcasting transmission antenna configured as described above,
By switching the switches S _{1 to} S ₅ , it is possible to obtain three types of vertical plane directivity even with one antenna, and it is possible to use for multiple purposes.

Further, FIG. 9 shows a second embodiment of the present invention, and this embodiment is replaced with the first, second and third conducting wires 6, 8 and 9 in the above-mentioned first embodiment. It is designed to use iron columns.

That is, in this case, instead of the first conducting wire 6 in FIG.
A first iron pole 32 of length λ / 4 whose lower end is insulated by an iron pole insulator 31
This first iron pillar 32 is erected vertically on the ground via an insulator 31. Further, instead of the second conducting wire 8 in FIG. 6, second iron pillars having a length λ / 4 with insulators 33 and 34 at both upper and lower ends.
35 is used, and the second iron pillars 35 are stacked so as to coincide with the upward extension line of the first iron pillars 32 via the insulators 34. Further, in place of the third conducting wire 9 in FIG. 6, a third iron pillar 38 of length λ / 2 with insulators 36 and 37 attached to the upper and lower ends is used,
The third iron pillar 38 is erected vertically on the ground via the insulator 37. Further, instead of the lower half BC of the iron pillar 4 in FIG. 6, a fourth iron pillar 39 whose lower end C is grounded is used.

Then, the iron pole connecting sheet metal 40 is attached to the upper surface of the upper insulator 33 of the second iron pillar 35, the upper surface of the upper insulator 36 of the third iron pillar 38, and the upper surface of the fourth iron pillar 39, and from the first iron pillar 32 and the second iron pillar 35. One post consisting of, and one post consisting of the third iron pillar 38,
A triangular prism is formed by the post composed of the fourth iron pillar 39. Further, the upper half A of the iron pillar 4 of FIG. 6 is attached to the central portion of the upper surface of the connecting sheet metal 40 arranged on the tops of these posts.
B is upright.

Further, the upper end E of the first iron pillar 32 and the central portion D of the fourth iron pillar 39 are mechanically and electrically connected by a horizontal member 41. Then, the central portion M of the third iron pillar 38 is connected to the upper end E of the first iron pillar 32 and the central portion D of the fourth iron pillar 39 through the horizontal members 44 and 45 in which the insulators 42 and 43 are inserted, respectively. This ensures mechanical stability.

On the other hand, the upper end E of the first iron pillar 32 and the lower end N of the second iron pillar 35 are configured to be connectable by the first switch S ₁ , and the upper end F of the second iron pillar 35 and the upper end P of the third iron pillar 38 are connected. Is the second switch S ₂
It is configured to be connectable with. Further, the lower end G of the first iron pillar 32 and the lower end H of the third iron pillar 38 are led into the switch / matching box 18 as in the case of the above-described first embodiment.
Although FIG. 9 does not show a group of branch lines that support each iron pillar for the sake of simplification of the drawing, this may be a known one.

Even in the case of such a configuration, the same operational effect as in the case of the above-described first embodiment can be obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications and changes can be made based on the technical idea of the present invention.

For example, in the above-described embodiments, the first, second, and third conducting wires or iron columns are used as the first, second, and third conductors, but the present invention is not limited to this, and any conductive long member may be used. Anything may be used instead.

f. EFFECTS OF THE INVENTION As described above, according to the present invention, since the iron pole having a higher ground clearance than the conventional case (the iron pole having a height equivalent to one wavelength of the broadcast wave) is used, the directivity of the vertical plane becomes sharp. , You can get big radiation ability. Also, it is not necessary to change the main structure of the grounded iron pillar with a height equivalent to one wavelength, and a relatively small structure consisting of a conductor group and a switch group with a height equivalent to 1/2 wavelength is attached. All that is required is easy and cheap to construct.

In addition, it is possible to obtain three types of vertical directivity by switching the switch group even with one antenna, which enables versatile use.

That is, (i) the lower end of the first conductor is grounded, the lower end of the second conductor is connected to the height 1/4 wavelength portion of the iron pole and the upper end of the first conductor by the first switch, and the second switch is used. By connecting the upper ends of the second conductor and the third conductor to each other and supplying power (single power supply) from the lower end of the third conductor (see FIG. 5 (I)), a strong vertical plane directivity is obtained in the low elevation angle region. You can launch the broadcast wave you have.

(Ii) Use the first switch to attach the lower end of the second conductor to the height of the iron pole 1 /
While connecting to the four wavelength part and the upper end of the first conductor, the second switch connects the upper ends of the second conductor and the third conductor to each other, and the lower end of the third conductor is grounded, while the power is supplied from the lower end of the first conductor. (Fig. 5 (I
See I)), which can emit a broadcast wave having a strong vertical plane directivity in the high elevation angle region.

(Iii) Both the first and second switches are opened to electrically separate the second conductor from the iron pole, the first conductor and the third conductor, and the power is supplied from the lower ends of the first conductor and the third conductor (double Power supply)
(See Fig. 5 (III)), and by appropriately selecting the ratio of the power supplied to the first conductor and the third conductor, it is possible to emit a broadcast wave that suppresses radiation especially in the high elevation angle region, It can be operated as a ding prevention antenna.

Further, in the present invention, since the iron column to be used is of the grounding type at the base, it does not matter, so there is no great difficulty in construction even if the height of the iron column itself is quite high.

Further, if a relay antenna (parabolic antenna or the like) is installed on the top of the iron pole, the height of the iron pole is high, which has the advantage of facilitating relay to a distant point.

In addition, since the steel pole is of the ground type, special filters and insulation are required when installing control lines for switch switching, direction control of relay antenna, blinking operation of aviation obstruction lights (necessary for high buildings), etc. There is also an advantage that it is not necessary to use a transformer or the like, and therefore the antenna construction cost is low.

[Brief description of drawings]

FIGS. 1 (I) and (II) are schematic diagrams showing the operating state of a vertical antenna composed of two conductors, and FIG. 2 is a schematic diagram showing the operating state when a relay antenna is attached to the top of the antenna. FIG. 3 is a characteristic diagram showing the vertical plane directivity of the antenna shown in FIG. 1, FIG. 4 is a characteristic diagram showing the vertical plane directivity in the case of the antenna shown in FIG. 2, and FIGS. 5 (I) and (II). ) And (II
I) is a schematic view for explaining the operation of the present invention, FIG.
FIG. 8 shows a first embodiment of the present invention,
The figure is a front view showing the configuration of a transmitting antenna for medium-wave broadcasting,
FIG. 8 is an enlarged view of a main part of a transmitting antenna for medium wave broadcasting, FIG. 8 is a schematic diagram showing a circuit configuration of a transmitting antenna for medium wave broadcasting and a transmission circuit, and FIG. 9 shows a second embodiment of the present invention. It is a front view similar to FIG. 3 ... Medium-wave broadcasting transmitting antenna, 4 ... Iron column, 5 ... First armband, 6 ... First conductor wire as first conductor, 7 ... Second armband, 8 ... As second conductor Second conductor, 9 ... Third conductor as third conductor, 10 ... Transmission circuit, 19, 20, 21 ... Insulator, 29 ... Parabolic antenna, 32 ... First iron pole as first conductor, 31, 33, 34, 36, 37 ... Insulator, 35 ... Second iron pillar as second conductor, 38 ... Third iron pillar as third conductor, 39 ... Fourth iron pillar, which is the lower half of the iron pillar, 40 …… Sheet metal for connecting steel poles, S ₁ …… First switch, S ₂ …… Second switch, S _{3 to} S ₅ …… Switch.

Claims (1)

[Claims] 1. An iron pole having (a) a height corresponding to one wavelength of a broadcast wave, and which is erected on the ground and whose base is grounded, and (b) an upper end is 1 / base from the base of the iron pillar. Length 1/4 connected to the height of 4 wavelengths and facing parallel to the iron column
With a first conductor of a wavelength, (c) parallel to the iron pillar and on an upward extension line of the first conductor facing a portion from the base of the iron pillar to a height of 1/2 wavelength from a height of 1/4 wavelength. A second conductor having a length of 1/4 wavelength, which is arranged so as to match and is connected to the first conductor through an insulator, and (d) is insulated from the first conductor and the second conductor, and A third conductor having a length of 1/2 wavelength which is erected on the ground in parallel to the ground, and (e) a first switch which electrically connects the lower end of the second conductor and the iron pole and the first conductor, (f) a second switch that electrically connects the upper end of the second conductor and the upper end of the third conductor, and (g) one of the lower end of the first conductor and the lower end of the third conductor. To the ground to supply the transmission power to the other end, or a transmission circuit that selectively operates to supply the transmission power to the two lower ends thereof, respectively. Provided, (h) ground the lower end of the first conductor, and connect the lower end of the second conductor with the first switch to the height 1/4 wavelength portion of the iron pillar and the upper end of the first conductor, By connecting the upper ends of the second conductor and the third conductor to each other in the second switch, and feeding only to the lower end of the third conductor, as a low-angle radiation antenna, (i) in the first switch The lower end of the second conductor is connected to the height 1/4 wavelength portion of the iron pillar and the upper end of the first conductor, and the upper ends of the second conductor and the third conductor are connected to each other by the second switch, While grounding the lower end of the third conductor, power is supplied only to the lower end of the first conductor to form a high-angle radiation antenna, or (j) the first and second switches are both opened to open the first conductor. The two conductors are electrically separated from the iron pillar, the first conductor and the third conductor. A high elevation angle is obtained by supplying electric power from the respective lower ends of the first conductor and the third conductor, appropriately selecting the ratio of the electric power supplied to the first conductor and the third conductor, and supplying electric power to both of them. A transmission antenna for medium-wave broadcasting, characterized in that it is an anti-fading antenna that emits a broadcast wave that suppresses area radiation.