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#万能生活指南#
Hello, everyone, this is Ye Dada, BD4SJY. Two days ago, I just released an introduction to amateur radio, about how to get an operating certificate and apply for a license and other details, I saw a lot of friends also left messages. Today, I will share another article on the basics of radio, and I will try not to use technical jargon as much as possible, so that you can understand the meaning more easily. Below I will share some relevant knowledge with you in need from the following points.
(1) About frequency
Radiocommunication is a communication method that modulates the electrical signals such as sound, text, data, and images that need to be transmitted on radio waves (3Hz-3000GHz) to each other through space and the ground, and uses radio electromagnetic waves to transmit information in space. The specific band division is shown in the table below.
Table of frequency bands for radio communications
(2) Frequency bands commonly used by amateur radio
Since we are amateur radio, this article only shares the frequency bands about amateur radio. If you only have obtained a Class A operation certificate, then usually we use the allowable transmission frequency range: 144-148MHz (V-band), 430-440MHz (U-band), so when we choose the entry machine, we need to pay attention to its allowable transmission and can only listen to the frequency configuration that can not transmit, some machines are with 56-108MHz (FM broadcasting) frequency band, and the 108-136MHz (AM aviation) frequency band, which everyone is more interested in, both of which can only be listened to and cannot be transmitted. So when buying a machine, please pay attention to the selection of the above frequency.
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(3) What is direct frequency
As the name suggests, there is direct contact between the two devices, take the common amateur radio direct frequency frequency as an example 438.500MHz, then the two machines set the transmitting frequency and receiving frequency at 438.500 at the same time, and can shout to each other within the distance that can be connected, of course, the frequency under the analog signal is the public frequency, if someone listens to this frequency in the surrounding range, then others can also hear our conversation.
438.500 direct frequency communication
(4) Communication distance
Many novice friends will ask, how far is the communication distance of the walkie-talkie, in fact, this can not be covered by a bias, because the communication distance is affected by many factors, the most critical of which is the power of the radio itself, the antenna and the location and height, so if two people are in a city with high-rise buildings, shouting to each other with a walkie-talkie at the height of the ground, it may only be 1-2KM, the distance, after all, the building is easy to block the signal, if we do not change the equipment at this time, we need to communicate farther, After all, there is not as much interference in the air as there is on the ground, and if you can't change the altitude, you can only increase the power of the device, or replace the antenna with higher gain, adjust your own transmitting position, and so on. Therefore, the communication distance of the walkie-talkie is affected by many factors.
My radio cabinet
(5) What is a relay
We mentioned the communication distance just now, and the communication distance of direct frequency is very limited, because it depends on many factors, so is there any way to extend the communication range? The answer is yes, and here we have to mention the repeater. As the name suggests, the relay receives your signal and forwards your signal again. Therefore, the relay station will generally choose to be erected at a high point in the city, such as the roof of a high-rise building, or the top of a mountain, take Wuxi relay as an example, Wuxi relay is erected on the top of Sanmaofeng in Huishan, with an altitude of more than 300 meters, because no matter in the process of relay reception or transmission, there is almost no obstruction that can interfere with the strength of the signal. In this way, we can expand the original limited communication distance a lot, and the normal distance of 50 or 60 KM in Wuxi urban area can also be connected normally through the relay.
Motorola Digital Relay
(6) What is frequency difference and subtone
When it comes to relays, we have to talk about frequency difference, because when our handset is working, it either transmits or receives, and it will not transmit and receive at the same time. But the relay is not the same, it will immediately forward the received signal after receiving our signal, if the relay is also a direct frequency at this time, then its own signal will also be received, so it is contradictory, this is similar to us holding the microphone to the speaker will howl, so the relay acceptance and transmission frequency is not the same, the same take Wuxi relay as an example, Wuxi relay parameter reception frequency 438.550, lower difference (-) 6.2, transmission subtone 88.5. Many novice friends don't understand, let's interpret it, the receiving frequency 438.550 is easy to understand, the transmitting frequency is 438.550-6.2 = 432.350 If it is the upper difference, then it is how much frequency is added, and here is the lower difference, then it is subtracted. If we set up the 438.550 direct frequency now, we can only hear the signal of the relay, but the signal transmitted will not be received by the friend station on the relay. What is a subtone? The main role is to control the noise suppression system in radio communications through specific low-frequency signals, ensuring that the receiver is only turned on to allow sound to pass through when a specific sub-audio signal is received. Such a system helps to reduce interference in radio communications, especially when communicating through repeaters. Sub-audio signals are not visible to human hearing, so they do not interfere with normal voice communication, but machines can recognize and process these signals for precise communication controlYou can also think of it as encryption or filtering. The subtone has a fixed value (67Hz-254.1Hz) instead of us entering it manually. Therefore, as long as you pass the WeChat public account or the information published by the local association, you can learn about the frequency of the local relay, look at the manual of your machine, adjust the relevant parameters according to the requirements, and you can communicate with the friendly station on the frequency.
Hytera HM780 Wuxi relay setup
Written at the end, first of all, it is a cliché, whether you have a certificate or not, please abide by laws and regulations, regulate listening or communication, and do not spread it. The above is some sharing of the new HAM, I hope to help you get started with the walkie-talkie as soon as possible, about the amateur radio series, I will do more sharing in the future, so that you can avoid the detours I have taken before. Later, I will talk to you about what is a digital machine, and the difference between digital signals between various brands, and even talk about shortwave communication, etc., if there are any questions, you can leave a message, you must know everything, and welcome the old HAM to exchange guidance, thank you! It's not easy to code words, ladies and gentlemen, I think it's useful to you, please give a thumbs up!
Motorola SL2M
The author declares that there is no interest in this article, and friends are welcome to communicate rationally and discuss harmoniously~