Electromagnetic radiation sources can be divided into the following categories:
(1) Broadcasting and television transmission equipment?
Short wave, medium wave broadcasting, high-frequency broadcasting, television broadcasting, etc. The main departments are broadcasting and television bureaus in various regions: the radiation characteristics are high-power timed omnidirectional transmission; The transmission signal is sent to the antenna for radiation.
(2) Communication, radar, and navigation transmission equipment
Communication is the fastest developing industry in China, especially mobile communication. This category includes shortwave transmitting stations, microwave communication stations, ground satellite communication stations, mobile communication base stations, professional communication websites, paging communication base stations, various radar equipment and navigation equipment, etc.
Radar and navigation are mostly directionally and irregularly transmitted, and the transmitted signals are also radiated out through antennas.
Due to improper media promotion, in recent years, the vast majority of radio electromagnetic radiation disputes among urban and rural residents have been directed towards mobile communication base stations.
(3) Industrial, scientific research, and medical high-frequency equipment
This type of equipment converts electrical energy into heat or other energy for utilization, but is accompanied by electromagnetic radiation generation and leakage, causing environmental pollution in the workplace.
Industrial electromagnetic radiation equipment: mainly includes high-frequency furnaces (including high-frequency induction furnaces, high-frequency quenching furnaces, high-frequency melting furnaces, high-frequency welding furnaces and electronic tube exhaust, quenching, annealing, sealing, brazing, semiconductor epitaxy, zone melting, single crystal pulling, etc.), plastic heat sealing machines (including high-frequency heat sealing machines, plastic welding machines, etc.), high-frequency medium heating machines, high-frequency drying machines, high-frequency wood drying machines, high-frequency sterilization equipment, high-frequency quenching equipment, microwave crushers, discharge machining machines, various types of electrical discharge machining equipment (including high-frequency molding machines, wire cutting machines, and multi head spot welding machines), etc.
Medical electromagnetic radiation equipment: mainly including high-frequency physiotherapy machine, ultrashort wave physiotherapy machine, ultraviolet ray physiotherapy machine, high-frequency diathermy machine, microwave electrotherapy machine, high-frequency cautery, microwave acupuncture and moxibustion equipment, etc.
Electromagnetic radiation equipment for scientific research and other purposes: mainly including electron accelerators, various ultrasonic devices, electromagnetic stoves, etc.
(4) Electromagnetic radiation in power systems
High voltage transmission lines include overhead transmission lines and underground cables. Generally, high voltage refers to those with a working voltage above 110kV; The substation includes a power plant (step-up station) and a transformer power station (step-down station).
(5) Electromagnetic radiation interference in transportation systems
Including: electrified railways, light rail and electrified railways, trams, trolleybuses, maglev trains, ignition systems for automobiles, etc.
Natural electromagnetic radiation has been with us humans for millions of years. It can even be said that without a natural electromagnetic radiation environment, there may not be humans; Even with humans, it may not be the way it is now. Because the Earth we live on is 4.6 billion years old, it is itself a huge magnetic field and also a huge electric field. The radiation frequency of the sun ranges from 10MHz to tens of GHz. The frequency spectrum of lightning is distributed around 50MHz, while the energy distribution is concentrated around 100kHz. There is a potential difference of 360000 volts between the ionosphere and the ground, resulting in an electric field strength of 130-140 V/m (volts/meter) near the ground. Every second, 1800 Coulombs of positive charge flow from the Earth's atmosphere to the earth. The sun and stars in space are constantly sending electromagnetic waves to Earth, and lightning, typhoons, and various underground mineral deposits in nature also send electromagnetic waves to the ground. Throughout millions of years of long evolutionary history, we humans have long adapted to and become accustomed to the electromagnetic radiation in nature. If natural electromagnetic radiation is gone, modern humans may fall ill, such as restricted growth processes, loss of direction, and possible precipitation of calcium ions in bones.
