The car / handstand is a radio station. The radio that everyone usually talks about is actually a radio station. There are usually many misunderstandings in terms of the name. For example, many people think that the "intercom" is used in pairs, or that the "radio" What a profound thing it is, it is actually very easy to understand-including the radio part of the stereo installed on your car, the radio of the Walkman, is actually a big class of things, translated into English, these are called RADIO, but we just said A radio station is usually a conventional communication tool that has both receiving and transmitting functions and can be used to transmit radio signals to communicate with others.
As for the radio, I did n’t say much, and I did n’t understand.
1. What is a radio station?
For the frequency / frequency point / channel, you can simply talk about the 97.4 103.9MHz that you usually listen to, which is the frequency. The frequency point may also be right. The channel is a bit far-fetched, but often it says "channel 103.9, Channel 97.4 "is really a bit misleading.
In fact, the radio we listen to every day is radio, only that it is transmitted by a "radio station". The power of the radio station is crazy, the location of the transmitting antenna is crazy good, and the coverage is crazy wide. So the receiver within its coverage (that is, the radio ) Can receive its signal and convert it into sound to play.
Now imagine that you and your friend each have a radio receiver (radio transmitter) in the car / hand, that is, the radio station (Radio Tranciver) you are discussing may be misspelled, anyway, the word is also Made). At the same time, it has both transmitting and receiving functions, so you can talk to each other.
2. Frequency / frequency point / frequency band 102. 9MHz is the frequency point of music station 89.7MHz is the frequency point of traffic station 438.550MHz is the transmission and reception frequency point that Qingdao amateur radio enthusiasts can legally use (400MHz frequency band, then other frequency bands) There are also legal frequencies for amateur HAM, so I won't say more here). Obviously everyone ’s FM radio does not support more than 430 MHz reception (it seems that the FM part is between 86 ~ 107MHZ), so if you want to transmit and receive signals on the 438.500MHZ frequency, you must have dedicated equipment , That is, what you usually need to say, "car / handstand / base station supporting amateur bands", etc.
If 438.550 is a frequency point, then it belongs to the 430MHZ band at the same time, we probably call 430.000-439.999 as the amateur 400M band, also known as the amateur 70CM (cm) band (the wavelength statement), because this band is mainly allocated to Used by amateur radio enthusiasts.
There may be more primary HAM contacts. The "2 meter band" or "140 megahertz amateur band" that people often say is between 144.000-145.999MHZ, which is also the frequency range that HAM can use.
3. The difference and simple concept of amateur radio / professional radio / radio is not much to say. Radio is used to listen to the signals emitted by other transmitters. The usual radio and frequency modulation (FB) / amplitude modulation (AM) are two parts. Two different modulation methods, correspondingly, there are also these two modulation methods in the radio. Everyone commonly uses FM radio stations that support the 430MHZ segment, while the air traffic control uses the frequency between 110MHZ-130MHZ. AM modulation method.
Let ’s talk about some simple differences between “amateur stations†and “professional stationsâ€. There is a layer of meaning that amateur stations are stations that support the amateur band—support (including) 430-440 bands, and professional stations support some other Radio stations in specific frequency bands
Another layer of meaning is that the functional aspects of amateur radios focus on "playing", and the adjustment of various related parameters, including adjusting the transmission power / searching for frequency points with signals / storing multiple different frequency points / can be manually changed at any time. Frequency points / adjust different squelch values ​​/ signal strength tables, etc. Professional radios pay more attention to the stability of use, so the complexity of operation is relatively low, and the battery durability / stable power stability and other performance The requirements are higher.
In comparison, professional stations usually cannot adjust the transmission power at will / there is no function to search for frequency points / can store a small number of frequency points and can only display the channel number but not the frequency point value / need to use a computer and special software and connection to adjust each The frequency and related functions stored in each channel / there is usually no signal strength meter display, and professional radio stations may also add some confidential measures such as FM, or support cluster functions (I do n’t know much) .
4, Repeater (Repeater) / difference frequency (OFFSET) and direct transmission
Some people may ask what "relay" is. If it is more detailed, it may be about the diffraction of waves. I am also a bit faint. I have already returned it to the physics teacher. Let ’s say there is such a high altitude or A pair of antennas and special transceiver stations are responsible for forwarding the signal received on one frequency point to another frequency point, so that all stations within its coverage area can contact it, that is, communicate with other people through it.
So to speak, due to the obstruction of buildings / terrain, etc., the signal between the two stations on the ground may not be able to reach each other, but the two people and this very high, well-positioned repeater can be very good Through the relay station, everyone will achieve a wider coverage through the relay station to help the small power equipment expand the purpose of the signal.
The usual relay station needs to use a pair of frequency points, one to receive the signal from the user's hand or vehicle platform (upstream signal, such as 433.550 used by everyone in Qingdao), and when received, broadcast on another frequency point ( Downlink signals, such as 438.550 in Beijing). Since the relay station must occupy a relatively good geographic location and may have relatively large transmit power, more people can be reached through the relay station.
Difference Frequency (OFFSET)
The difference between the 439.750 (the frequency that the user listens to, the downstream frequency) and 434.750 (the frequency that the user transmits, the upstream frequency) just mentioned is the difference frequency. We can see that the transmitted frequency is the received frequency. Points minus 5MHZ (-5MHZ), so it is called "lower difference 5MHZ". For some radio stations, you can directly set the uplink frequency point and the downlink frequency point and save it to a channel for easy use. For some radio stations, the setting method is to first set the receiving frequency, then set the difference frequency value and direction, and save it to a certain channel. .
Straight hair
Usually the radio station transmits and receives on the same frequency point. The user switches the radio station's receiving / transmitting state through the PTT (PUSH TO TALK) key, presses the button to speak, and releases to listen. Receiving and sending at a frequency point is called "straight hair". For example, 438.500 438.550MHZ is a relatively commonly used amateur radio direct frequency in Beijing.
Of course, on the same frequency point, only one device can transmit at the same time, and other devices receive it. If two people are transmitting at the same time, their signals will interfere with each other and they will be inaudible.
4. Main points for buying amateur radio stations
Don't be superstitious about MOTO 6200C and some foreign-made FRS (FAMILY RADIO SERVICE) household small walkie-talkies, it is simply a toy!
In order to avoid the interference of transmitting equipment to other frequencies, the power of these products must be less than 0.5 watts, and the direct transmission distance may be 2 kilometers without blocking. If it is in the urban area, 1 kilometers is already good. The only advantage is that it does not require any license and inspection machine, and it can be bought and used. Of course, these small hands are fixed channel fixed frequency transceiver equipment, which can be understood as "low-power / non-adjustable frequency professional radio (home)", of course, their frequency is fixed at 409. ??? (domestic) 462 .? ? ? / 467. ? ? ? The MHZ (import) range usually has only 16 fixed frequency points and cannot be changed. If your other amateur radio stations support these frequencies, you can communicate with them directly, but obviously, these small toys cannot communicate with HAM.
If you want to select a radio station, you must meet the following conditions:
★ The frequency range covered must support (inclusive) 430-440MHz
★ Must have the difference frequency function ★ It is recommended to choose a machine that can set the frequency manually (that is, you can directly select the frequency point and freely store it in the channel without using the computer to write the frequency)
★ It is recommended that the power should be above 25W (carriage) / support a maximum of 5W (hand platform) to ensure the connection distance.
★ Should have the function of "Yin Yin".
With the above conditions, you can enter the ranks of amateur radio enthusiasts (HAM) (of course, you must also go through the relevant legal procedures)
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