1, the TV display is not clear.
The function of tuner is to amplify weak video signal and deal with image distortion and interference caused by unstable transmission. The video processing chip determines the resolution of the image, while the tuner determines the stability of the image. However, the tuner itself is very vulnerable to electromagnetic interference, so the built-in TV card usually wraps a metal layer outside the tuner to shield electromagnetic interference, so once it is broken, it will not be clear or even have an image.
2. High-frequency digital signals cannot be mediated.
After demodulation of high-frequency digital signal, the output digital signal is TS(Transport Stream) stream, also called transport stream, which is a digital signal transport stream with "frame" as the unit. Each frame of digital signal includes synchronization header, data, end and other signals. If it is damaged, channel selection, high-frequency signal amplification and frequency conversion cannot be performed.
3. High frequency signals cannot be down-converted.
The main task of tuner is channel selection, and the other task is frequency reduction, which reduces the received high-frequency signal to a fixed frequency. This fixed frequency signal is an intermediate frequency signal, and its frequency is generally 38MHz. If the signal is still a high-frequency video signal, it needs to be further amplified before it can be demodulated and processed. If it is damaged, it will affect the signal frequency reduction.
Extended data:
Working principle of tuner.
Most of the receiving circuits in the tuner are arranged in a micro-motion mode, and all components are surface mounted. Because of its high efficiency at microwave frequency, micro-motion design is adopted. The width and length of wear are directly related to the frequency of use. The basic function of the tuner is to pick up the weak signal reflected by the dish antenna and then transmit the signal to the receiver.
The problem encountered here is that the dish antenna and receiver are usually separated by a certain distance, and the loss is quite high at microwave frequency. In order to overcome the difficulties, the tuner converts the UHF SHF signal from the dish antenna to a lower intermediate frequency band, and then transmits the signal to the receiver through the cable, which is relatively efficient.
Baidu Encyclopedia-Andhadhun