The difference between a TV transmitter and a radio receiver is the same. The former has audio signals. With the laying of the foundation of electronic technology, radio and television have developed accordingly. In 1906, people used wireless to express their congratulations to mankind for a Merry Christmas, but it took ten years for this technology to achieve practical purposes. In 1916, the American Sarnov drew up a plan to receive music broadcasts from radio stations by answering machines. This is the first radio station in the world. In 1935, radio broadcasting was basically perfected after continuous improvement. At that time, there were as many as 1,550 radio broadcasting stations in the world.
Programs that use radio waves or wires to broadcast sounds and images to a wide area are collectively referred to as "broadcasts." Radio radios can be divided into tube radios, semiconductor radios, and solid-state circuit radios according to their structure; according to their volume, they can be divided into floor-standing, desktop, portable, pocket-sized, and miniature; according to bands, they can be divided into medium wave, medium short wave, short wave, ultra short wave, Long, medium and short wave, full band; according to the broadcasting system, it can be divided into amplitude modulation and frequency modulation; according to the program specifications can be divided into super and first, second, third, and fourth; according to the power supply, it can be divided into AC, DC, AC and DC use.
According to the special purpose and multi-purpose, it can be divided into automobile, AM rewind, FM rewind, rebroadcast, stand-up sound, record dual-use, expand dual-use, and other multi-purposes. No matter how complicated or incomprehensible a radio receiver is, it consists of four basic parts. This is very useful for us to understand the principle of radio. These four parts: antenna, ground wire system: it receives radio waves and reproduces them as currents of various frequencies. Tuner: It selects the current of a station that needs to be supplied, and suppresses the current of those stations that are not needed.
What is the difference between a TV transmitter and a radio receiver
Detector: It changes the current of the required radio station into a useful form that can be converted into sound. Speaker: It converts the current from the detector into a sound that can be perceived by human ears. These four parts are necessary for all kinds of receivers, whether it is the simplest mineral radio or complex television receivers, but the latter has been improved. The radio's ability to distinguish each station is just the choice of transmitting waves of different carrier frequencies. The transmitter combines the signal of the carrier and the audio signal, that is, the amplitude modulation or frequency modulation wave to transmit to all directions, and the rapidly oscillating electromagnetic wave is composed of electric and magnetic fields.
The electrons in the radio antenna move with the vibration of the electric field of all radio signals reaching the antenna. This tiny current is only equivalent to the current caused by a voltage of a few microvolts. The radio's "tuner" uses a resonant circuit to tune to the carrier frequency of a certain radio station you want to receive. Other carrier frequency signals are suppressed because they cannot get resonance. The radio amplifier amplifies the resonant signal, and then The detector circuit separates the carrier frequency from the sound and color signal, and the audio signal is amplified again and restored from the speaker to the music and voice that the human ear feels.
There are as many as 700 million radios. It is also mixed with the video signal. The TV has a radio component, in addition, the TV has its display circuit display corresponding to the video, and a picture tube. The basic structure and working principle of the superheterodyne receiver can be discussed from the antenna first. Suppose an 800 kHz radio signal enters from the antenna, the signal is enhanced after high-frequency amplification, and the enhanced signal is sent to the mixer. The oscillator of the receiver itself also sends a signal to the mixer at this time, and its frequency should be 1,255 kHz.
The two electrical signals are mixed in the mixer to form a "beat", and a new signal is obtained. The frequency of this signal is one thousand two hundred and fifty-five minus eight hundred which is equal to four hundred and fifty-five kilohertz. This frequency of four hundred and fifty-five hertz is called "intermediate frequency", which is abbreviated as "intermediate frequency" in radio technology. If the frequency of the electrical signal from the antenna is 900 kilohertz, then the receiver's own oscillator must also generate dry hertz. Electrical signal. After being sent to the mixer, the mixed beat still gets an intermediate frequency signal of 1355 minus 900 equal to four hundred and fifty-five kilohertz.
The intermediate frequency electrical signal is amplified in a special intermediate wave amplifier, and after passing through the demodulated detector, the audio signal can be restored. The audio signal is also called low frequency signal. After the audio signal is amplified again by the low frequency amplifier, the current can be sent to the speaker to emit sound.
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