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How to choose marine radio ?

Spectrum is a physical quantity that exists in nature and cannot be increased or decreased, making it extremely valuable. According to the definition of the International Telecommunication Union, the frequency range of electromagnetic wave is from 3kHz to 300GHz when human beings can recognize the use of the frequency range. for the convenience of expression, the frequency band from 3kHz to 300GHz is divided into eight parts according to the frequency level, namely, VLH (Very Low Frequency), LF (Low Frequency), MF (Medium Frequency), HF (High Frequency), VHF (Very High Frequency), UHF (Ultra High Frequency), EHF (Extremely High Frequency) and THF (Terahertz Radiation). THF (terahertz radiation) for a total of eight parts. In general, the higher the frequency, the worse the penetration. The lower the frequency, the smaller the bandwidth available.

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Medium Frequency MF (300KHz~3MHz) – the lifeblood of broadcasting and radio navigation

If you often listen to the radio, you will certainly find that many radio stations will say that the medium wave XXX such frequency, here the so-called medium wave, in fact, is the meaning of medium frequency. After mankind successfully mastered and used VLF and LF, it was discovered that radio waves can also transmit sound and other information. So IF became the preferred frequency band for the initial regional radio stations. Our country stipulates that the frequency band for medium wave broadcasting is 525-1605KHz with 9KHz interval, and all medium wave radio stations must comply with this regulation.

In addition to broadcasting, medium wave is also used in many navigation systems. NDB, the process navigation system used in civil aviation today, is also based on this frequency range.

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High Frequency HF (3MHz~30MHz) – The Starting Point of Global Communications

In the field of radio broadcasting, HF is referred to as shortwave. Since HF can realize ultra-long-distance transmission through ionospheric reflection without the need for a very high strategy of the transmitting station, the first broadcasting station covering the whole world and the first telecommunication station covering the whole world have been realized in the HF frequency range. It is no exaggeration to say that from the high frequency, mankind has the first global radio communication ability.

 

VHF Very High Frequency (30MHz-300MHz)

From low frequency to high frequency, we have mastered the method of transmitting sound and information across the globe, and the next step, of course, is to be able to communicate in both directions, and ideally, to be able to see the picture as well. So VHF VHF was developed and utilized. In this band, FM radio, walkie-talkie, BP pager, cordless phone, wireless TV have debuted, so that the general public for the first time felt the charm of wireless communication, the popularity of these products also profoundly affect the development of society.

In addition to the radio and television known to the general public, VHF is also responsible for international maritime communications, aviation navigation, aviation ground ATC communications.

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UHF (300MHz~3GHz) – the backbone of digital communication

①Frequency Use

VHF amateur frequency is 144-148MHz (dedicated), UHF amateur is 430-440MHz (shared). In terms of frequency usage, the VHF amateur frequency band is much less than UHF, so the signal in the VHF band is often congested. So what is the difference between the two in our practical use? As an example, when you go hiking, VHF radios would be more appropriate. Because the radio wave of VHF walkie-talkie is round-shot, it can avoid the obstruction of the mountain and maximize its advantages.

②Radio Wave Propagation

Wireless communication is a long-distance transmission, so the ability of radio wave propagation is very important. Since the propagation loss of high-frequency signals in the air is larger than that of low-frequency, the propagation effect of VHF is better than that of UHF in long-distance communication. And when in the same position, the same antenna height, UHF channel received signals often appear unstable situation, easy to jam, copying is not clear; in the VHF channel, even if the signal will appear slight fluctuations, but the copying is stable and clear and no jamming.

In this way, the UHF band seems to have been in the downside? Doesn’t it have any advantages? Of course not!

With the development of modern cities, the application of walkie-talkie in fact, in the service industry, construction industry, administrative departments and institutions and other fields have been widely used. In this kind of environment where there are more buildings, the advantage of UHF band is highlighted. the ability of UHF band to penetrate the wall is far better than VHF signal.

In summary, how should we choose UV radios? Two suggestions:

First, in the open mountains and plains, it is recommended to use VHF band walkie-talkie, which can give full play to the long-distance propagation characteristics; in the city with dense high-rise buildings, it is recommended to use UHF band walkie-talkie.

 

Marine VHF radio box

 

 

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