Why is it difficult to receive medium-wave and short-wave programs on the radio now?

I am a radio interpreter, and I will answer!

I often see older fans leave me messages complaining. They claimed that they could clearly receive a local medium-wave radio station or an international radio station through the radio several decades ago, but now when they turn on the radio, they can only receive rustling noise in most cases, and the reception quality is not as good as before. So they come to the conclusion that the quality of the current radio is worrying, and it is not as good as the old machine they used before!

In this regard, I want to say that this is a misunderstanding. The reason why there are few medium-wave or short-wave radio stations received now is not that the performance of contemporary radios is not as good as that of the old ones, but that there are other reasons!

Specifically, there are two main reasons: First, the rise of cement forests has seriously hindered the transmission of short-wave signals, and reinforced concrete has shielded indoor radios, so the number of shortwave radio received is far less than in the past. Many radio lovers find that the use of the same radio indoors and outdoors is completely different, which is why.

Secondly, the electromagnetic interference in the living environment is more and more serious than before, which also affects the reception of medium and short waves. Fluorescent lamp, computer power supply, mobile phone charger and electric car charger are all ubiquitous and ever-present electromagnetic interference sources. Especially in electric car charger, as long as it is in working condition, the medium and short wave reception on the upper and lower floors will be completely abolished.

This is the main reason why I think there are few shortwave radio now. In fact, any qualified radio in the past may be a wonderful machine with excellent performance!

Do you agree with me? Please leave a comment!

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Compared with FM, medium wave and short wave have relatively complicated lines. Medium wave should have a built-in magnetic rod antenna. Many plug-in radios have only one FM. If it is a full-band cassette radio, it will be relatively expensive. For example, plug-in radios, one in 30 yuan, then, all-band plug-in radios, just fifty or sixty yuan each. Besides, FM is received at close range, which is very clear. Short wave and medium wave are not very clear. The reception of the radio is not good. Therefore, I don't think it is necessary to mass-produce full-band radios. Because it is not easy to sell when it is produced. I sell plug-in radios. Some high-end radios with recording, remote control and remote control.

The controller has many functions and no one buys it. In the end, they all sold at a loss. So there is no medium wave and short wave, because the production cost is high and it is not easy to sell.

Medium-wave and short-wave broadcasting is easily disturbed by chaotic electromagnetic waves. With the increase of all kinds of electronic communication equipment and all kinds of electrical equipment, the electromagnetic environment becomes extremely bad, which will seriously interfere with medium and short wave broadcasting. In addition, there are many high-rise buildings, mainly reinforced concrete buildings, which also have a strong shielding effect on medium and short wave broadcasting. All these have greatly reduced the quality of medium and short wave broadcasting.

The good quality of urban FM broadcasting is related to the use of higher frequency carriers and modulation methods. Different from the low-frequency carrier and amplitude modulation which are easily interfered by electromagnetic waves, FM broadcasting adopts high-frequency carrier and frequency modulation which are not easily interfered by electromagnetic waves, which greatly improves the quality of FM broadcasting.

However, FM broadcasting also has disadvantages. Because of its high carrier frequency, its propagation is linear and its transmission distance is short. Medium wave mainly propagates in the form of ground wave, which can travel a long distance around obstacles. Short waves can also be reflected back to the ground through the ionosphere, so they can travel longer distances. The disadvantage is that short-wave signals with long propagation distance are also unstable due to the instability of ionosphere.

In the early 1980s, my father bought a "Ying Ge" semiconductor single-band (medium-wave) radio, which was powered by three 1 dry batteries, tuned manually, and displayed the pointer frequency, with high sensitivity and loud sound.

The most popular program is the medium wave program of Shanghai People's Broadcasting Station, which is more than 50 kilometers away from the local/kloc-0. Liu Lanfang ballads The Biography of Yue Fei and Yang Jiajiang, etc. In the afternoon, there is a story-telling program "Nezha" and so on. These wonderful programs are still fresh in my memory.

Radio can be divided into pocket, portable and desktop. According to the size, it can be divided into manual tuning of pointer display frequency, manual tuning of LCD display frequency and digital automatic tuning of LCD display frequency. According to the receiving frequency range, it can be divided into frequency modulation (FM) 87- 108 MHz. Its radio waves travel in a straight line and have strong anti-interference ability, but the propagation distance is short (called the sound of the city).

FM radio stations in China rose in the early 1990s, when cassette tapes were popular, and song-ordering programs were very popular.

Popular plug-in cards (USB flash drive, TF card), portable radios, Bluetooth speakers, car audio systems, etc. Generally, they have FM reception function, and the reception effect is good in the city (poor in mountainous areas), but several FM stations with high transmission power or adjacent frequencies will interfere with each other, making the reception effect worse. The telescopic antenna can be shortened, the antenna direction can be changed, and the listening position can be changed, which can effectively reduce the interference degree and improve the listening effect.

The receiving frequency range of AM MW radio is 520- 16 10 KHz. Its radio wave propagation path mainly depends on ground waves (radio waves propagating along the space near the earth's surface), and only a part of it propagates in the form of sky waves (radio waves propagating through ionosphere reflection), and the propagation distance is very long. Usually, more radio stations are received at night than during the day. Radio stations in the province can generally receive radio waves normally (local FM and MW signal stations will generally broadcast at the same time, and the corresponding frequency will be informed when the program is broadcast), and the reception effect is better in mountainous areas, with built-in magnetic rod antenna. The receiving effect of this antenna with large size or high circuit power supply voltage is generally better than that of a radio with small bar antenna and low power supply voltage.

Generally, car audio equipment only has a metal rod antenna, but no magnetic rod antenna. Even if it has the medium wave (MW) function, it is still a decoration, with serious interference, and basically no broadcast can be received, but the general FM reception effect is better.

If you receive a medium wave (MW) radio for a long time, you need to choose a portable or desktop radio with a large volume, and its electrical performance (sensitivity, etc.). ) it will be relatively better.

The receiving frequency range of short wave (SW) radio is 1.6-30 MHz, and its radio wave transmission mode is mainly sky wave (ionospheric reflection), which can be transmitted over a long distance. Many countries use short-wave frequency to promote global broadcast transmission. When my children went to college, they told me that they needed to bring a short-wave (SW) radio when they started school, so they bought one specially.

The short-wave frequency is generally divided into several "meter bands", and each "meter band" contains a frequency range, which is represented by SW 1, SW2, etc. The International Radio Commission (CCIR) stipulates that civil broadcasting uses frequencies within the meter band, while frequencies outside the meter band are mostly used for military and other civil communications. Only in the frequency range of the meter band can you hear civil radio programs.

The effect of listening to short-wave broadcasting depends on the transmitting power of the radio, the sensitivity of the radio and the environmental factors of the receiving place. The propagation of short-wave signals is influenced by objective changes in the atmosphere and ionosphere. Not all the signals in the frequency band will be good, some are better during the day, some are better at night, sometimes the sound will be louder or louder, and the noise will be louder, especially around noon, which will be greatly affected by ionospheric changes, and usually the listening effect will be better at night.

Reinforced concrete buildings and other structures will attenuate the received signals. In order to improve the reception effect, an external antenna can be used, but the height and length of the antenna need to be adjusted several times. Sometimes if the antenna is too high and too long, it will also introduce interference signals, which is counterproductive and needs patient and repeated adjustment.

For radio lovers, you can also buy a professional multi-band, secondary frequency conversion, high sensitivity and other excellent performance, ultra-long-distance reception radio. These radios are beautifully designed and well-made, but the receiving environment is much worse now than it was decades ago, and all kinds of radio interference are inevitable.

Although it is the Internet age, television, radio and paper media will not die out and will be greatly impacted, but they may not be able to replace them.

Now all fake radio stations in society use fm, which explains the problem well. The medium wave signal is seriously interfered, and the existence of a remote controller around various interference sources will interfere with the medium wave signal. The possible source of short-wave transmission is changed to satellite transmission, and China Radio International is changed to satellite transmission. Voice of America changed to satellite transmission. Provincial radio stations stopped broadcasting medium wave transmission, and other local stations did not know that Yunnan People's Broadcasting Station stopped broadcasting medium wave news channels.

The crystal receiver, which was widely used in the early 1950s, has a simple structure and he can make one himself. The effect is very good, and it is even better to use diode detection later. There are many other radios now, but the listening effect is not good. There were few radio waves in the air at that time, so it was easy to receive. There are so many radio waves in the air now that it is difficult to detect them. It is not that the high-end radio at that time was not as good as a crystal receiver. This is my shallow opinion, just take it for granted.

I think there are fewer relay stations now. In the past, because there were no TV, mobile phones, computers and other entertainment carriers, there were many people listening to the radio, so the country built short-wave relay stations all over the country, so the programs broadcast to china national radio and provincial and municipal radio stations were more and clearer. Now that there are fewer listeners and fewer relay stations, it is difficult to listen to short-wave programs everywhere. Now I mainly listen to FM programs.

You are wrong! Now the radio can still receive short-wave programs. If you go to an open area far from home, you will know.

You can't get it because the current household appliances and lighting lamps all use switching power supply, which interferes with the medium and short wave segments.

Strong harmonic interference, just in the range of long wave, medium wave and short wave. Long waves are not used in radios, so we don't feel interference. Ultra-short wave FM broadcasting itself has anti-interference ability, and it is far away from the frequency of interference sources and can still be listened to normally.

Using the secondary frequency conversion radio can improve the listening effect. But the interference nearby is generally strong, which may still disappoint you.

Nowadays, there are high-rise buildings everywhere in China, and it is difficult for radio waves to penetrate buildings, reinforced concrete walls and industrial electrical equipment to form interference. In the last century, low-rise buildings were everywhere, and radio stations could be received far away, and short-wave radio stations from Japan, the Soviet Union and the United States could be received.

According to my practical experience in using radio, there are many reasons for radio signal attenuation. Every radio