The radio was first used in sailing, using the Morse telegraph to convey information between the ship and the land. Radio has a variety of applications, including wireless data networks, a variety of mobile communications and radio and so on.
The following are the main applications of some radio technologies:
The earliest form of sound broadcasting is the nautical radio telegraph. It uses a switch to control the transmission of a continuous wave, thereby generating an intermittent sound signal at the receiver, i.e., the Morse code.
* AM broadcasts can spread music and sound. AM broadcast using amplitude modulation technology, that is, the microphone to accept the greater the volume of the radio is also the greater the energy. Such signals are susceptible to interference such as lightning or other sources of interference.
* FM radio can spread music and sound more than fidelity broadcasts. For frequency modulation, the higher the volume received at the microphone, the higher the frequency of the transmitted signal. FM radio work in very high frequency (Very High Frequency, VHF). The higher the band, the greater the frequency bandwidth it has, and thus can accommodate more radio stations. At the same time, the shorter the wavelength of the radio waves spread closer to the light wave propagation characteristics.
* FM radio sidebath can be used to spread digital signals such as station identification, program name introduction, website, stock market information and so on. In some countries, when moved to a new area, the FM radio can automatically automatically find the original channel based on the sideband information.
* Nautical and aeronautical use of voice stations using VHF AM technology. This allows the use of light antennas on airplanes and ships.
* Government, fire, police and commercial use of radio stations are usually used in special frequency band narrowband FM technology. These applications typically use 5KHz of bandwidth. Relative to the FM radio or television sound 16KHz bandwidth, fidelity had to make sacrifices.
* Civil or military high frequency voice services use shortwave for communication between ships, airplanes or isolated locations. In most cases, single-sideband technology is used, which saves half the frequency band relative to AM technology and makes more efficient use of transmit power.
Terrestrial Trunked Radio (TETRA) is a digital trunking telephone system designed for special departments such as the military, police, and first aid.
* Cellular phones or mobile phones are the most commonly used wireless communication methods. The cell phone coverage area is usually divided into multiple cells. Each cell is covered by a base station transmitter. Theoretically, the shape of the cell is a honeycomb hexagon, which is also the source of the cell phone name. Currently widely used mobile phone system standards include: GSM, CDMA and TDMA. Operators have begun to provide the next generation of 3G mobile communications services, the dominant standards for UMTS and CDMA2000.
* Satellite phones exist in two forms: INMARSAT and Iridium systems. Both systems provide global coverage services. INMARSAT uses geostationary satellites that require directional high gain antennas. Iridium is a low-orbiting satellite system that uses mobile phone antennas directly
* The usual analog TV signal uses the image amplitude modulation, audio frequency modulation and synthesis in the same signal transmission.
* Digital TV using MPEG-2 image compression technology, which only need to simulate half of the bandwidth of the TV signal.
* The emergency position indicating radio beacons (EPIRBs), emergency positioning transmitters, or personal positioning beacons are small radio transmitters that are used to locate personnel or measure satellites in an emergency situation. Its role is to provide the exact location of the rescue personnel in order to provide timely rescue.
* Digital microwave transmission equipment, satellites and other commonly used quadrature amplitude modulation (Quadrature Amplitude Modulation, QAM). The QAM modulation mode simultaneously utilizes the amplitude and phase of the signal to load the information. In this way, you can deliver a larger amount of data on the same bandwidth.
* IEEE802.11 is the current wireless local area network (Wireless Local Area Network, WLAN) standards. It uses 2GHz or 5GHz band, the data transmission rate of 11 Mbps or 54 Mbps.
* Bluetooth is a short-range wireless communication technology.
* Use of active and passive radio equipment to identify and indicate the identity of the object. (See Radio Frequency Identification)
* Amateur radio is a radio communication that radio enthusiasts are involved in. Amateur radio stations can use many open bands on the entire spectrum. Fans use different forms of coding and technology. Some later commercial technologies, such as FM, on the side with amplitude modulation, digital packet radio and satellite signal transponders, are used by amateurs first.