JP2015091104A - Mobile antenna system - Google Patents

Abstract

A mobile aerial device capable of providing a stable broadcasting service by using a minimum site suitable for broadcasting in an emergency.
A folded antenna (9) including a mobile crane jib (5), a hoisting rope (7), and a grounded vehicle body (3) and an audio signal are input and modulated by the audio signal. And a portable signal generator (15) that generates a high-frequency signal and supplies it to the folded antenna (9).
[Selection] Figure 1

Description

  The present invention relates to a mobile antenna device that can be suitably used in an emergency such as a disaster.

  AM radio broadcasting stations using the medium wave band have a large number of master stations that serve a wide area as service areas and relay stations that serve small and medium-sized areas throughout the country. The AM radio broadcast provided by such an AM radio broadcast station is a public broadcast media, and plays an important role in transmitting disaster information and the like particularly in the event of an earthquake.

By the way, when the transmitting station becomes unable to transmit in the event of an emergency such as a disaster, an alternative transmitting facility is required. Non-Patent Document 1 describes an example of a spare antenna used in such an alternative transmission facility.
However, most emergency standby antennas are installed in the master station class. That is, in the case of the relay station class, since there are many problems such as securing costs and land, most broadcasters do not have spare antennas.
Recently, the Ministry of Internal Affairs and Communications has been studying “technical conditions related to safety and reliability related to broadcasting” and “strengthening of broadcasting networks”. It is increasing.

Yasuo Odagiri, Sadanobu Machida, Kazuo Nakano, Shoichi Matsumura, Takashi Tsutsui: “Concentrated Insulation Medium Wave Preliminary Antenna and Its Multipurpose Use”, Broadcasting Technology, Kenrokukan Publishing, September 1975, pp. 77-81

  Conventional medium-wave broadcasting standby antennas are often installed in the premises of the head office, the master station transmitting station, or at another transmitting place as an alternative to the antenna of the master station. In a master station and a relay station, a branch-type base insulation type or base ground type antenna having an antenna height of λ / 4 to λ / 2 (λ is a wavelength of a used frequency) is generally used. If such an aerial is to be permanently installed as an emergency medium wave aerial, problems will arise in terms of construction costs and securing of land.

  Therefore, in general, a wire aerial wire or a folded grounded aerial wire using an existing steel tower in the transmitting station site of the master station or a steel tower on the head office roof is used as an emergency aerial line. However, in many cases, such an antenna cannot secure a sufficient antenna length suitable for the used frequency, and in that case, the performance is considerably inferior to an antenna that is always operated. In addition, since the broadcast area is small, it is difficult to cover the regular broadcast area of the transmitting station, and it is difficult to relocate because there are many permanent types.

  The present invention has been made in view of such circumstances, and its purpose is to provide a stable broadcasting service using a minimum site suitable for broadcasting in an emergency such as a disaster. It is to provide a possible mobile antenna device.

  In order to solve the above-described problems, the present invention inputs a folded antenna including a mobile crane jib, a hoisting rope, and a grounded vehicle, and an audio signal, and generates a high-frequency signal modulated by the audio signal. And a portable signal generator for supplying the folded antenna to the folded antenna.

For example, a rough terrain crane is used as the mobile crane. Also,
The portable signal generation device includes a matching unit that performs impedance matching with the folded antenna as necessary.

As the high-frequency signal supplied from the portable signal generation device, for example, an analog high-frequency signal or a digital high-frequency signal in the medium wave broadcasting band modulated by a predetermined method is used.
The mobile antenna apparatus according to the present invention may further include receiving means for receiving the radio wave transmitted from at least one of a broadcasting station, a performance station, and a relay station to generate the audio signal.

According to the present invention, since the components of the mobile crane are used as elements of the aerial line, it is possible to broadcast at the optimal location in the event of a disaster, such as in the vicinity of the transmitting station where transmission was impossible due to the disaster It becomes. Moreover, since the cost required for installing the aerial line is only the borrowing cost of the crane, the installation cost can be kept low.
In addition, since there are few tasks that involve danger such as work at high altitudes or work that requires skills, it can be handled only by station personnel and crane operators, so that broadcasting can be started quickly and with a small number of people. .

It is a block diagram which shows schematic structure of the mobile antenna apparatus which concerns on this invention. It is a graph which shows the example of a frequency characteristic of the antenna feeding point impedance in case the length of the vertical part of a winding rope is set to 54 m. It is the graph which illustrated the horizontal surface directivity of the mobile antenna apparatus concerning the present invention. It is the graph which illustrated the vertical surface directivity of the mobile antenna apparatus concerning the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a mobile antenna apparatus according to an embodiment of the present invention. In FIG. 1, a rough terrain crane 1, which is one of mobile cranes, is parked by moving to a position suitable for broadcasting.
In the present embodiment, by grounding the vehicle body 3 of the rough terrain crane 1 to the ground, the telescopic jib 5 supported by the vehicle body 3 so as to be able to rise and fall and the tip of the telescopic jib 5 are suspended. The hoisting rope 7 is used as a base grounded folded antenna 9. The grounding of the vehicle body 3 can be performed by connecting the vehicle body 3 and several grounding rods (not shown) driven into the ground via a cable 11 such as a booster cable.
Note that an auxiliary jib (not shown) may be attached to the tip of the telescopic jib 5 (used to extend the jib length). When this auxiliary jib is used for the purpose of increasing the drooping length of the hoisting rope 7, it is also a component of the antenna 9.

In the hoisting rope 7, the hook 13 is held to the ground via an electrically insulating rope or the like (not shown) in order to stably maintain the hanging state. For this securing, for example, an anchor driven into the ground or a weight placed on the ground is used.
The folded antenna 9 can be operated as a vertically polarized antenna that emits omnidirectional radio waves in a horizontal plane by supplying high-frequency power to the tip of the winding rope 7.

The portable signal generation device 15 positioned in the vicinity of the rough terrain crane 1 has a configuration in which an audio mixer 17, a transmitter 19, and a matching unit 21 are mounted on an equipment vehicle.
Receivers 23 and 25 are connected to the audio mixer 17. The receiver 23 receives an AM radio broadcast wave (program broadcast wave) from a broadcast station different from the broadcast station that cannot be transmitted due to a disaster or the like via the antenna 27. As the antenna 27, a loop antenna or a simple wire antenna is used. On the other hand, the receiver 25 uses a signal (including an STL (Studio-Transmitter-Link) line signal) or wireless signal transmitted from a performance or relay station using radio waves in the VHF band or UHF band. A transmission signal from the microphone is received via the antenna 29. The audio mixer 17 inputs the audio signals output from the receivers 23 and 25 to the input terminals T1 and T2, respectively.

  A temporary line (line line such as NTT) 31 and a mobile phone 33 are also connected to the audio mixer 17 as necessary. The temporary line 31 transmits a program audio signal from a performance place or the like, and the mobile phone 33 receives the program signal from the performance place or the like via a mobile phone line network. The audio mixer 17 inputs audio signals output from the temporary line 31 and the mobile phone 33 to the input terminals T3 and T4, respectively.

The audio mixer 17 inputs an audio signal (program signal) based on any of the audio signals input to the terminals T1 to T4 to the transmitter 19 via an audio cable. The transmitter 19 generates an analog high frequency signal of a predetermined radio frequency (medium frequency broadcast band frequency) amplitude-modulated by the input audio signal, and outputs this high frequency signal to the matching unit 21. The matching unit 21 is connected to the tip of the winding rope 7 via a cable 35 such as a booster cable. Accordingly, the high-frequency signal is fed to the tip of the hoisting rope 7 through the matching unit 21 and the cable 35. As a result, the vertically polarized wave 37 having the predetermined radio frequency is radiated from the folded antenna 9.
The audio mixer 17 and the transmitter 19 are supplied with AC power (for example, 100 V) from the generator 39. The generator 39 may be mounted on the equipment vehicle.

By the way, since the length and inclination of the telescopic jib 5 are related to the length of the hoisting rope 7 that hangs down to the vicinity of the ground, the apparent efficiency and the feeding point impedance of the antenna 9 are affected. The table below shows an example of antenna feed point impedance and apparent efficiency when 50 ton and 25 ton cranes are used as the rough terrain crane 1.

  Λ in Table 1 indicates the free space wavelength of the used frequency. FIG. 2 shows an example of frequency characteristics of the antenna feed point impedance when the length of the vertical portion of the hoisting rope 7 is set to 54 m. Characteristic a and characteristic b are for the high frequency resistance component and the reactance component, respectively. These components show values on a one-dot chain line when the frequency is 1116 kHz, for example. Although this impedance characteristic is relatively stable, when the length of the vertical portion of the hoisting rope 7 is shortened, the resonance peak moves in a higher frequency direction.

  As apparent from the above table, the apparent efficiency and antenna feed point impedance are adjusted by adjusting the length of the jib 5 or the sum of the length of the jib 5 and the auxiliary jib, the length of the vertical portion of the hoisting rope 7, and the inclination of the jib 5. Can be controlled by. Therefore, according to the mobile antenna apparatus according to the present embodiment, it is possible to realize an antenna feed point impedance that can be easily matched with a target apparent efficiency.

  The matching unit 21 is provided to match the antenna feed point impedance represented by Table 1 to the output impedance of the transmitter 19 (50Ω in the present embodiment), and a variable matching element for supporting a wide band. I have. The grounding terminal of the matching unit 21 is connected to the grounding rod used for grounding the vehicle body 3 of the rough terrain crane 1 using an IV (IndoorPVC) wire or the like.

  FIG. 3 shows the horizontal plane directivity (measured value) according to the length of the vertical portion of the hoisting rope 7, and FIG. 4 shows the same vertical plane directivity (calculated value). As is apparent from FIG. 3, the radiation pattern of the dynamic antenna apparatus of the present embodiment is almost omnidirectional. And the apparent efficiency tends to increase as the length of the vertical portion of the hoisting rope 7 increases.

  The dynamic aerial device according to the present embodiment configures the folded aerial 9 using the rough terrain crane 1 which is one of the mobile cranes. Can be performed. In addition, work from installation of the rough terrain crane 1 to on-air including alignment adjustment of the aerial can be completed in a short time (about 1 hour for 2 to 3 people). Become. Since the matching unit 21 of the portable signal generation device 15 has a variable matching element having a wide matching range, the time required for matching adjustment can be shortened.

The present invention is not limited to the configuration of the above-described embodiment, and may include modifications as exemplified below.
(A) In the above embodiment, the rough terrain crane 1 is used as the mobile crane, but a mobile crane having a jib that does not have a telescopic function can also be used.
(B) In the above embodiment, the transmitter 19 generates an analog high-frequency signal in the medium-wave broadcast band, but it is also possible to generate an analog high-frequency signal in the short-wave broadcast band.
(C) By changing the modulation method, the transmitter 19 can generate a digital high-frequency signal in the medium wave broadcast band or the short wave broadcast band.

DESCRIPTION OF SYMBOLS 1 Rough terrain crane 3 Car body 5 Telescopic jib 7 Winding rope 9 Folding antenna 11 Cable 13 Hook 15 Portable signal generator 17 Audio mixer 19 Transmitter 21 Matching device 23 Receiver 25 Receiver 27 Antenna 29 Antenna 31 Temporary line 33 Mobile Telephone 35 Cable 37 Vertical polarization 39 Generator

Claims (5)

A mobile antenna device using a mobile crane,
A folded antenna comprising the crane jib, hoisting rope and grounded vehicle body, and
A portable signal generator that inputs an audio signal, generates a high-frequency signal modulated by the audio signal, and supplies the high-frequency signal to the folded antenna;
A mobile antenna apparatus comprising:   The mobile antenna apparatus according to claim 1, wherein the mobile crane is a rough terrain crane.   The mobile antenna device according to claim 1, wherein the portable signal generation device includes a matching unit that performs impedance matching with the folded antenna.   The high-frequency signal supplied from the portable signal generation device is an analog high-frequency signal or a digital high-frequency signal in a medium wave broadcast band modulated by a predetermined method. Mobile antenna system.   5. The receiving apparatus according to claim 1, further comprising receiving means for receiving the radio wave transmitted from at least one of a broadcasting station, a performance station, and a relay station to generate the audio signal. Mobile antenna system.

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