People in the use of wireless walkie-talkie often hear the background noise, squelch, refers to the radio in order to solve the call quality and noise problems, and design of the squelch circuit or squelch function. Squelch function has a different squelch level, according to the actual situation to adjust themselves.
Wireless walkie-talkie and cable phone in the answer there is a big difference, that is, background noise. Under normal circumstances, the wired telephone is basically no background noise (regardless of communication distance), and wireless communication in the wireless radio will inevitably appear background noise, the background noise and the strength of the received signal, the distance between the communication distance and The quality of the walkie-talkie has a lot to do. We use the walkie-talkie have such an experience, when the received signal is strong, the noise is small, no noise, very clean; otherwise the signal is weak, the noise is large. In the use of the same radio to receive the other signal, the call distance, the received signal is strong, the noise is small; and call distance, the received signal is weak, the noise is large, or even hear the voice.
The mute function in the walkie-talkie or the design of the squelch circuit is to solve the problem of call quality and noise. The squelch function is to strictly filter out excessive background noise, eliminate or suppress the background noise when no signal is received, so that the loudspeaker remains silent when no signal is received, and the squelch circuit is turned off, Will hear the horn sound.
The purpose of squelch is to strictly suppress the noise, but if the suppression of excessive will make the weak call signal will be limited to receive. Especially in the long-distance call, the weak remote communication signal together with the noise suppressed, it is not desirable. Adjusting the squelch is to reduce, suppress, or eliminate unwanted noise, so that it does not pass through the speaker, but keeps the call signal (even in the case of a weak signal). Adjust the squelch is actually adjusted, select the size of the squelch circuit level. When the signal level to what extent to be able to open the squelch, when the signal level down to what extent when the squelch closed. The signal level is too high may not receive a useful weak signal, too low will be subject to noise and other useless signal interference. It can be said that the mute function is the basic function of the walkie-talkie.
The noise intensity in the received signal is inversely proportional to the signal. The higher the signal, the weaker the noise; the weaker the signal, the stronger the noise. In the mid-nineties of last century before the radio mute adjustment is from the largest to the smallest stepless adjustment. From the mid-nineties since the mid-1990s in the radio design will be the maximum noise and minimum noise is divided into several files, each file is called a level, with the number to represent, called the squelch level, also known as squelch level. The squelch level (level) of each model is different. Such as: Japan Trane’s DR435 car platform noise from 0-20, is divided into 21 levels. Japan Vitex VX160 handheld walkie-talkie from 0-12, divided into 13 levels. While the Japanese ICOM IC-F21 handheld walkie-talkie from 0-255, divided into 256 levels. Shenzhen good Autopass TC-368 handheld walkie-talkie from 0-9, divided into 10 levels. Japan’s Trane’s DR-C5 pocket-sized hand-held walkie-talkie only 5 levels. The higher the number here, the higher the level, the higher the level, the stronger the ability to suppress the noise, the noise or other irrelevant signal interference is also less, the less the noise, but also less likely to receive Need to receive useful weak signal. On the contrary, the smaller the number, the lower the level, the lower the level, the weaker the ability to suppress the noise, noise and other useless signal interference, the same easier to receive a weak and useful signal. The "0" level indicates that there is no squelch suppression function, the lowest level.
Set the principle
The principle of setting the squelch level is based on the user’s communication environment and communication requirements. When the user requests the communication distance farther, this time the receiving signal will become weak, which requires the receiving sensitivity higher, the squelting level will be smaller, or the silence adjustment shallow. When the user’s communication distance is close, the received signal is strong, the receiver sensitivity can be reduced, the squelting level will be higher, or that a little noise mute, the noise will be smaller. When the intermittent discovery in the call, said the receiver to receive the signal is weak, or in the call during the communication distance can not hear the voice, then reduce the squelch level to improve t