1, -2000khz. 3500-3900khz. 7000-7200khz. 10100-10150khz (minor). 14000-14350khz. 18068-18168khz. 21000-21450 KHZ. 24890-24990khz.
2, China's amateur radio operators have a clear frequency range, according to the "People's Republic of China Radio frequency Division Regulations", these frequency packagesInclude: 1800-2000khz, 3500-3900khz, 7000-7200khz, 10100-10150khz (minor), 14000-14350khz, 18068-18168khz, 21000-21450khz and 24890-24990khz.
3, the frequency range of the GHz band is 5725MHz ~ 5850MHz, the TDD mode of time-division duplex is adopted, the maximum radiation power shall not exceed 500mW, and the base station needs to obtain a radio transmission license. hereonKHz) long wave disturbances, 10 km to 1 km wavelength, mainly ground wave propagation, suitable for transoceanic communications. Medium frequency (MF) 0.3-3 MHz (MHz) medium wave, 1 km to 100 m wavelength, ground wave combined with sky wave, used in Marine communications, amateur radio communications and mobile communications, as well as medium distance navigation.
3, in the field of communication, the frequency band refers to the frequency range of electromagnetic waves, the unit is Hz, according to the size of the frequency, can be divided into: very low frequency (VLF) 3 kHz~30 kHz, the wavelength of the corresponding electromagnetic wave is very long wave 100 km~10 km. The low frequency (LF) is 30 kHz ~300 kHz, and the corresponding wavelength of electromagnetic wave is 10 km~1 km.
4, radio waves are classified according to wavelength and frequency, the wavelength of long waves is more than 1000 meters, and the frequency is between 300 KHZ and 30 KHZ. The wavelength of the medium wave is between 100 and 1000 meters, and the frequency range is 300 kilohertz to 3000 kilohertz. The short wave has a wavelength between 100 and 10 meters and a frequency between 3 MHZ and 30 MHZ.
5, radio according to wavelength and frequency: longWave: Wavelength 1000, frequency 300KHz-30KHz. Medium wave: wavelength 100M-1000M, frequency 300KHz-3000KHz. Short wave: wavelength 100M-10M, frequency 3MHz ~ 30MHz. Ultrashort wave: wavelength 1M-10M, frequency 30MHz-300MHz, also known as very high frequency (VHF) wave, meter wave. Microwave: wavelength 1M-0.1MM, frequency 300MHz-3THz. Radio waves contain magnetic fields that vibrate rapidly.
6, the channel is a channel for transmitting information, and the wireless channel is wireless in spaceRadio wave transmission information channel, so the wireless communication protocol in addition to define the allowed use of frequency bands, but also accurately divided frequency range, frequency range is the channel, the channel can not overlap. If there are multiple overlapping channels in a space, channel interference occurs.
Transmission frequency is an extremely important technique in radio broadcastingThe technical parameter is the limited natural resource of radio spectrum, and it is one of the indexes to measure the quality of radio wave emitted by medium and short wave broadcasting station.
Transmission frequency is a very important technical parameter in radio broadcasting, is a limited natural resource of radio spectrum, and is one of the indicators to measure the quality of the radio wave emitted by the medium and short wave broadcasting station. The carrier frequency is in the process of signal transmission, not the signal is directly transmitted, but the signal load to a fixed frequency wave, this process is called loading, such a fixed frequency.
Carrier frequency refers to the base that carries the information signal used in communicationThe frequency of an oscillator waveform. In a general broadcast or television signal, the carrier frequency is usually between several hundred kHz and several hundred MHz, and different standards and application scenarios may have different carrier frequencies. In radio communication, carrier frequencies are usually generated by frequency modulation, amplitude modulation, and phase modulation techniques and can be selected and adjusted by a tuner or other device.
A carrier wave is a radio wave of a specific frequency, in Hz, that is modulated in frequency, amplitude modulation, or phase to transmit speech, music, images, or other signals. The carrier frequency is in the process of signal transmission, not the signalThe transmission is carried out directly, but the signal is loaded onto a wave of a fixed frequency, this process is called loading, such a fixed frequency.
Radio waves cannot be seen or touched. For wireless charge modulation frequency let the listener who is not familiar with radio knowledge understand what is the wavelength of radio waves, what is the frequency of radio waves, We may wish to compare radio waves to the gradual outward diffusion of a circle of water waves caused by a stone falling into the water: the stone entering the water point is the center of the water wave, noneThe line electric transmitting antenna is the center of the radio wave, so the distance between the two adjacent water waves or radio waves is called the wavelength.
High-frequency carrier: needs to be understood separately. Carrier: Radio communication uses a carrier for the purpose of reception. If the carrier is not used, many transmitted signals sent into the air at the same time will produce superposition, interference with each other, not conducive to reception, after the use of a specific frequency of the carrier, the signal that needs to be transmitted is loaded onto the carrier, the receiving end only needs to use the same frequency of LC oscillation circuit (resonance), you can receive the required signal (AM: amplitude modulation).
2, signal modulation can move the spectrum of the signal to any position, so as to facilitate the transmission of the signal, and make full use of the spectrum resources. For example, the antenna must be one-tenth the size of the signal or larger in order for the signal to be radiated effectively. For voice signals, the corresponding antenna size should be more than tens of kilometers, which is practically impossible to achieve. This requires the modulation process to move the signal spectrum to a higher frequency range.
3, the modulation technology is to change the baseband signalThe technology to transmit the signal. In order to ensure the communication effect and overcome the problem of long-distance signal transmission, the signal spectrum must be transferred to the high-frequency channel through modulation. Baseband signal is the original electrical signal, generally refers to the basic signal waveform, in digital communication refers to the corresponding electrical pulse.
4, these different modulation, is a different method, the signal and carrier synthesis technology. The reverse process of modulation, called demodulation, is used to decode the original signal. The role of modulation in the communication system: to allow multiple baseband signals to be transmitted simultaneously on the wired channel after modulation, but also suitable for non-modulationThe transmission of frequency band signal is realized in line channel. Enhance the anti-noise capability of the signal. The transmission bandwidth and signal-to-noise ratio can also be exchanged.
5, the role of modulation in the communication system is to reduce interference, improve the anti-interference ability of the system, and also realize the exchange between the transmission bandwidth and the signal-to-noise ratio. Signal modulation is the process or treatment of making certain characteristics of one waveform vary according to another waveform or signal. In radio communication, electromagnetic wave is used as the carrier of information.
6, so people introduce modem data communication, that is, low-speed data after modulation through the radio skyAfter the line is transmitted out and the other side is received by the antenna, the original data is restored by demodulation. This method is also suitable for ADSL modems with telephone line Internet access. Due to the modem, ADSL signals can be superimposed on the analog phone line, rather than having to lay a separate dedicated Internet connection line.
1, IEEE 8011b is a wireless local area network standard. Its carrier frequency is 4GHz and can provide up to 5 and 11Mbit/sRetransfer speed. IEEE 8011g was adopted in July 2003. Its carrier frequency is 4GHz (the same as the 8011b), the original transmission speed is 54Mbit/s, and the net transmission speed is about 27Mbit/s (the same as the 8011a).
2, IEEE8011a works in the 5GHz U-NII band, thus avoiding the crowded 4GHz band, so there is almost no interference compared with 8011b. The speed of the physical layer can reach 54Mbps, and the transmission layer can reach 25Mbps.
3, wireless networkThere are six standards, namely: 8011a high-speed WLAN protocol, using 5G Hertz band. The maximum speed is 54Mbps, and the actual usage rate is about 22-26Mbps. Incompatibility with the 8011b is its biggest drawback. 8011b The most popular WLAN protocol, using the 4G Hertz band.
4, there are six wireless network standards, as follows: 8011a is a high-speed WLAN protocol, it uses 5GHz band. The standard can reach a maximum speed of 54Mbps, and the actual use rate is about 22-26 MBPS. itIt is incompatible with the 8011b, which is one of its biggest disadvantages. 8011b is the most popular WLAN protocol and it operates in the 4GHz band.