What era is it now? Mobile phones are so easy to use, why do people still use walkie-talkies?
That's because walkie-talkies have no phone bills, do not rely on the Internet, and can be connected as soon as they are called, so walkie-talkies always have a place in short-distance wireless communication scenarios. And they will still be widely used in various industries and fields, such as emergency communications, transportation, etc.
Ⅰ. Composition of walkie-talkies
From the outside,, bulky and old-fashioned. The working principle of this "antique" is actually similar to that of mobile phones. We can simply describe walkie-talkies as consisting of transmitters, receivers, antennas and other parts. Among them, the transmitter is used to modulate voice signals into radio waves or other electromagnetic waves and send them out through the antenna; the receiver is used to receive radio waves or other electromagnetic waves and convert them into voice signals.
Ⅱ. The principle process of intercom speaking
- Microphone: The intercom converts sound signals into electrical signals through the microphone. There is a diaphragm inside the microphone. When sound enters, it causes the diaphragm to vibrate slightly, thereby generating a changing current signal.
- Audio amplifier: The function of the audio amplifier is to amplify the weak electrical signal output by the microphone so that it can be processed by the modulator.
- Modulator: The function of the modulator is to modulate the audio signal into radio waves or other electromagnetic waves. In analog intercoms, the modulator superimposes the audio signal on a high-frequency carrier to form an RF signal; in digital intercoms, the modulator digitally modulates the audio signal to form a digital RF signal.
- RF power amplifier: The function of the RF power amplifier is to amplify the RF signal output by the modulator so that it can be transmitted by the antenna.
- Antenna: The antenna is a component used to transmit radio waves or other electromagnetic waves. The antenna of the intercom is usually a whip antenna or a spiral antenna, which can convert the RF signal into radio waves or other electromagnetic waves for transmission.
Ⅲ. The principle and process of answering a call on a walkie-talkie
- Antenna: It can receive radio waves or other electromagnetic waves.
- RF filter: The function of the RF filter is to filter out the stray signals received by the antenna and only allow signals of a specific frequency to pass through.
- RF amplifier: The function of the RF amplifier is to amplify the weak signal output by the filter so that it can be processed in the next step.
- Demodulator: The function of the demodulator is to demodulate radio waves or other electromagnetic waves into audio signals. In analog walkie-talkies, the demodulator demodulates the RF signal into an audio signal; in digital walkie-talkies, the demodulator demodulates the digital RF signal into a digital audio signal.
- Audio amplifier: The function of the audio amplifier is to amplify the audio signal output by the demodulator so that it can drive the speaker or headphones to make sound.
- Speaker or headphone: Speakers or headphones are components used to convert audio signals into sound. When audio signals pass through speakers or headphones, they vibrate, thereby producing sound.
Ⅳ. Classification of walkie-talkies
It has been nearly a hundred years since the invention of walkie-talkies. Now walkie-talkies are mainly divided into three categories: analog walkie-talkies, digital walkie-talkies, and IP walkie-talkies.
- Analog walkie-talkies
Analog walkie-talkies are the earliest and most widely used walkie-talkies. They modulate analog signals to the communication frequency band of walkie-talkies, which can restore sound signals to the greatest extent and sound very natural, pleasant, and real. Two walkie-talkies need to use the same communication channel within the call range to successfully communicate.
- Digital walkie-talkies
Digital walkie-talkies use digital signals to convert voice into digital signal encoding for transmission, which can avoid noise, distortion, and other problems during the call process, and have a certain degree of confidentiality.
- IP walkie-talkies (public network walkie-talkies)
IP walkie-talkies, also known as public network walkie-talkies, are walkie-talkies that connect to our existing communication network to achieve the expansion of the call distance. IP walkie-talkies use existing communication networks to make calls, which are essentially no different from mobile phones.
Ⅴ. Why are there still people using walkie-talkies?
The unprepossessing walkie-talkies actually rely on these "seven characteristics" to gain a firm foothold in short-distance wireless communication scenarios:
- Working frequency band
According to regulations, the working frequency bands of professional walkie-talkies usually use the VHF band 136 MHz~174 MHz and the UHF band 400 MHz~470 MHz.
- Communication channel
The walkie-talkie provides a channel selection function: two walkie-talkies can communicate immediately by adjusting to the same channel.
- Transmitting power
The greater the power of the walkie-talkie, the farther the call distance between the two walkie-talkies. According to the data, walkie-talkies with a power of less than 0.5 watts are classified as "civilian walkie-talkies", walkie-talkies between 0.5W and 5W are classified as "amateur walkie-talkies", and those exceeding 5W must apply for a radio license, otherwise it will be considered illegal use. The power of a handheld walkie-talkie is generally within 5 watts, and the power of a vehicle-mounted or ship-mounted radio is relatively large, ranging from 25 watts to 50 watts, and even 100 watts.
- Call range
The call of the walkie-talkie is completely dependent on the walkie-talkie itself. The call distance between two walkie-talkies is affected by many factors such as transmission power and obstacles. Generally, the call range of a handheld walkie-talkie is within 3 kilometers, and the call quality can be maintained clear. In the environment of high-rise buildings in the city, the call range will be affected by obstacles.
- Antenna
We know that the higher the frequency of the radio wave, the shorter the wavelength, and the shorter the corresponding antenna for receiving the radio wave. Since the walkie-talkie uses a lower working frequency band, the length of the antenna is relatively long in order to receive the radio wave, so the general walkie-talkie is a "long ear".
- Battery
The walkie-talkie is generally equipped with a large-capacity removable battery. And if the walkie-talkie does not send a signal for a long time, it will automatically "sleep" to save power until it receives a new signal or a key operation, it will "wake up".
- Structure
The walkie-talkie has a simple structure and is easy to carry. In order to facilitate the use in complex outdoor environments, it has also specially strengthened the functional structure such as waterproof and dustproof, anti-fall and anti-shock.