Road to the introduction of a microd loan for beginners -radio waves used for the 8th microd loan

Micro drones are attracting attention because they are capable of capturing images that were difficult to achieve with conventional aerial drones, such as being able to get close to people and pass through narrow spaces. In this series, I will focus on the points that beginners are likely to stumble upon introduction.

Text ●Yusuke Aoyama/Composition ●Editorial Department

Lecturer ●Tetsuya Tagawa／A drone engineer whose main occupation is the design of I-PEX connectors, which are also used in drones. About six years ago, when he still called drones “multicopters,” he started building aerial drones. Since 2014, he has also been involved in the production of racing drones. Founder and administrator of the Facebook group "U199 Drone Club". 2016 Dubai international tournament Japan national team engineer. Currently DMM RAIDEN RACING team engineer.

You can't talk about micro drones without mentioning radio waves. Radio waves are used to radiate electrical energy into the air and transmit signals, using a transmitter that sends out radio waves and a receiver that receives them. Radio waves are used everywhere in our social life. For example, the smartphones and Wi-Fi routers you have are excellent transmitting and receiving devices.

In order to use radio waves in Japan, as a general rule, it is necessary to apply to the Telecommunications Bureau of the Ministry of Internal Affairs and Communications, which has jurisdiction over telecommunications, and obtain a license as a radio station. Also, to operate this radio station, a radio operator's license is required.

By the way, there are two main radio waves used in drones. Radio waves for controlling the aircraft with a radio and radio waves for transmitting images taken with a camera from the aircraft to goggles when flying with FPV. Radio waves for control mainly use the same 2.4 GHz band frequency as Wi-Fi. This radio wave is treated as a "low power data communication system" and can be used without a license if the wireless device has received technical standards conformity certification (Technical Conformity).

DJI's drone for aerial photography multiplexes the image data captured by the camera with the control radio wave and transmits it, so even if you fly with FPV, you do not need a license related to radio waves. However, radio-controlled transceiver systems such as Futaba used for micro drones cannot transmit images.

Therefore, the micro drone is equipped with a VTX (transmitter for video transmission) for video transmission. Most of the widely marketed VTXs use the frequency band around 5.7GHz, which corresponds to the 5.6GHz amateur band (5.650-5.850GHz) in Japan, so it is called "ATV ( Amateur TV)” was opened as an amateur radio station, and most of the people are using it. If you want to operate as an amateur radio station, you need to be qualified as an amateur radio engineer.

Of course, the VTX installed in the micro drone and the general-purpose VTX used in the self-made machine have not received technical standards conformity certification. However, in amateur radio, it is permitted to make your own radio equipment, and VTX is treated as "homemade radio equipment", and you can apply as an amateur radio station using the system of "guarantee" established by the Ministry of Internal Affairs and Communications. You can.

On the other hand, when using a micro drone for business purposes such as photography, using a VTX that has been opened as an amateur radio station is a violation of the Radio Law. Therefore, in Japan, a licensed dedicated VTX will be used as a radio station for the "unmanned mobile image transmission system" established in the 2.4 GHz band and 5.6 GHz band for drones and robots. In this case, a special land radio engineer or higher is required.

The frequencies used by drones are included in the international ISM (industrial, scientific and medical) bands such as the 920MHz band, 2.4GHz band and 5.6-5.8GHz band, and the same frequency or the immediately adjacent frequency is important used by social infrastructure. In addition, the frequency distribution of radio waves is different in each country.

For example, the 920MHz band is used overseas as a strong radio wave, and communication equipment is operated on the assumption that there is such a strong radio wave, but Japan does not have such a strong radio wave (so-called platinum band). Therefore, ISM band communication equipment communicates with weak radio waves. Just because there is no problem in using it overseas, it cannot be said that it will not cause problems in Japan.

For that reason, we absolutely do not use wireless devices whose output or radio wave quality may affect other devices, or use VTX for amateur radio for business purposes. Don't do it.

Main frequency bands of radio waves used by drones

▲ Examples of radio waves in the same frequency band as the main radio waves used by drones.

The 2.4GHz band is the mainstream for control signals

Until now, 27MHz, 40MHz, 72MHz, and 73MHz bands have been used for radio control, but recently more and more are adopting the 2.4GHz band. Most drones use the 2.4GHz band. Radio waves are used to control the aircraft and transfer images for FPV applications. Consumer products such as DJI mainly use the 2.4GHz band.

Devices that extend the reach of radio waves are not allowed

Overseas e-commerce sites and radio control shops sell propos that have not been certified as technical standards and "long range modules" that can extend the distance of control radio waves. can't. The 900MHz band used by these modules is also used in Japan as the ISM band (for industrial, scientific, and medical use), and its strong transmission output has a serious impact.

Video transmission requires a radio operator license and a radio station license

▲Radio waves used for hobby and business, required qualifications, and radio stations are different. The specific application method and procedure will be explained in the next section.

We asked the Ministry of Internal Affairs and Communications and the Kanto Bureau of Telecommunications! Current state of crackdown on illegal radio waves

In the Ministry of Internal Affairs and Communications, which has jurisdiction over radio administration in Japan, in addition to illegal citizen radio stations and illegal personal radio stations that interfere and interfere with important radio communications, illegal amateur radio stations and We are implementing measures such as monitoring, crackdowns, and guidance for illegal radio stations such as radios that conform to overseas standards.

The key to this is the radio wave monitoring system called DEURAS (DEtect Unlicensed Radio Stations). Using sensor stations installed in approximately 350 locations nationwide, including the buildings of the General Telecommunications Bureau and mobile phone base stations, the locations of illegal radio stations are identified. In addition, an illegal radio station search vehicle is dispatched near the illegal radio station to identify the source of the radio wave. Administrative guidance is given to the discovered illegal radio stations, and even more malicious ones are prosecuted.

DEURAS is the center station of the Kanto Bureau of Telecommunications and monitors the whole country 24 hours a day, 365 days a year. Furthermore, Article 80 of the Radio Law obliges licensees of radio stations to report to the Bureau of Telecommunications when they discover an illegal radio station. You can say that they are under constant surveillance.

It is natural to comply with the Radio Law when flying a drone. And don't forget that you're under these scrutiny.

Illegal radio waves are identified by the DEURAS system

There are "sensor stations" equipped with antennas that detect illegal radio waves in about 350 locations nationwide. Information of each sensor station is sent through the line. Search using a dedicated DEURAS terminal. The Kanto Bureau of Telecommunications constantly monitors late at night, early in the morning, and on holidays.

Illegal radio station search vehicle

It looks like a normal wagon, but it has an antenna on the ceiling that can detect illegal radio waves, and information on each sensor station in the back seat. It also has a large battery so that you can search even if the terminal and engine are stopped.

The site of the crackdown

Once we identify illegal radio waves, we will call attention to them, and if there is still no improvement, we will jointly carry out crackdowns with the police.

Reprinted from Video SALON September 2019 issue