Theory of radio waves: educational program. What waves does the TV pick up? What waves does it pick up?
Analogue television signals are several megahertz wide, so the long, medium and short wave bands are too narrow for them. To transmit such signals, at least ultrashort waves are used. This situation did not change with the transition to digital television.
Instructions
The wave bands allocated for television broadcasting vary from country to country. In Russia, standard D has been adopted for analogue broadcasting on meter waves, providing 12 channels. The first of them corresponds to a frequency of 49.75 MHz for transmitting an image signal and 56.25 MHz for transmitting a sound signal. In the last of them, image and sound are transmitted, respectively, at frequencies of 223.25 and 229.75 MHz. Transmissions on UHF waves were previously not carried out in all cities, but today they are in almost every city. Channel frequencies in this range are established by the K standard. On the first of them, number 21, frequencies of 471.25 and 477.75 MHz are provided for image and sound signals. The last channel of the range was initially 41 (631.25 and 637.75 MHz), then 60 (783.25 and 789.75 MHz), and today it is channel number 69 (855.25 and 861.75 MHz). The image signal is amplitude modulated, the sound signal is frequency modulated. The attentive reader will assume that in all cases the difference between the frequencies for transmitting image and sound is 6.5 MHz. In other countries, this difference may be different, amounting to, for example, 5.5 MHz (standards B and G).
There are large gaps between channels 5 and 6, and 12 and 21. It is impossible to organize television broadcasting on air frequencies falling within these intervals - this may interfere with radio broadcasting and other types of communications. But they can be broadcast via cable, which is often practiced today. At first, televisions were unable to operate in these ranges; set-top boxes were required. Now, almost all TVs can receive these channels, numbered from S1 to S40, on their own. The frequency differences for transmitting image and sound signals on these channels also comply with the standards adopted in the country.
Digital television broadcasting is carried out at frequencies within the existing UHF range, so existing antennas can be used. Only between the antenna and the TV you need to place a set-top box-decoder, or use a TV with a built-in decoder. But thanks to compression in digital broadcasting, it is possible to introduce so-called multiplexes, when several television channels are broadcast on one frequency channel. In the DVB-T2 standard, compression is even more efficient than in DVB-T. Used for cable broadcasting DVB-C standards and DVB-C2.
Satellite television broadcasts use frequency ranges corresponding to units and tens of gigahertz. Previously, it was also analog, but frequency modulation was also used to transmit image signals. Now satellite broadcasting is carried out in the same bands, but using digital standards, in particular DVB-S and DVB-S2.
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Analogue television signals are several megahertz wide, so the long, medium and short wave bands are too narrow for them. To transmit such signals, at least ultrashort waves are used. This situation did not change with the transition to digital television.
Instructions
2. The principle of water supply system.
3. Natural form of inorganic substances.
4. Universal type of energy.
5. Capacity for storing electricity.
6. Infrared ray emitter.
7.What waves does the TV pick up?
8. What rays are reflected by the surface of the lemon?
9. What should a person’s economy be like?
1) The main source of protein food in the future.
2) What keeps the ship afloat.
3) The principle of water supply system.
4) Heavy, shiny, hard, plastic...
5) (Grandmother) of all engines.
6) Universal type of energy.
7) Does sound travel in space?
8) Infrared ray emitter.
9) What waves does the TV pick up?
10) What rays are reflected by the surface of the lemon?
11) What should a person’s economy be like?
fertility of the fields 3-
microclimate improving device 4-
main consumer in artificial ecosystems 5-
the main source of protein food in the future 6-
what helps lift the weight 7-
main part of land transport 8-
property of water that helps to wash 9-
what keeps the ship afloat 10-
principle of water supply system 11-
what warms a person in warm clothes 12-
air-supported device 13-
finely ground stone flour 14-
natural form of inorganic substances 15-
heavy, shiny, hard plastic... 16-
a property that a blacksmith uses 17-
raw materials for gasoline production 18-
"grandmother" of all engines 19-
universal form of energy 20-
capacity for storing electricity 21-
does sound travel through space? 22-
infrared emitter 23-
what waves does the TV pick up? 24-
what rays are reflected by the surface of the lemon? 25-
main computer part 26-
objects rotating around the earth 27-
what should a human economy be like?
a wave-polished pebble, while the vast ocean of truth lies before us, boundless, unexplored." How do you explain these words?
When sound waves appear, the auricle seems to collect them and direct them to...........(Insert the missing word). Having passed through the ear canal and hitting the eardrum, the sounds cause it ............... (Insert the missing word). The vibrations are amplified and transmitted through the sound ossicles (anvil, ...............) to the cochlea. The cochlea is filled with fluid, and its inner ............. (Insert the missing word) is covered with cells with tiny ............ (Insert the missing word) . Each hair is a “string” that ......... (Insert the missing word) transmits its sound to the brain. The brain collects all sounds, trying to understand what it hears.
Help please! This is the world around the ear
Radio waves with frequencies ranging from 3 kHz to 300 GHz belong to the electromagnetic spectrum. Other facts about radio waves are presented in this article.
Wave transmission!
In a significant discovery in the field of communication transmission, radio waves were discovered in 1867 by Scottish physicist James Maxwell.
Have you ever noticed that most of the devices we use in our lives are based on the concept of transmitting data through radio waves.
A television antenna receives electromagnetic waves from a television station and in turn transmits various channels. Whether it's a microwave oven or a telephone, almost all of our devices require radio waves to operate or transmit data. Radio waves are used mainly to transmit information in space. Their main function is to transmit data through modulation. They have an advantage over many other types of signals due to the fact that their speed is equal to the speed of light when traveling in a vacuum. High speeds transfers make the transfer process very efficient.
How do radio waves work?
Telecommunications in a wireless environment primarily use electromagnetic signals. A carrier signal is one such electromagnetic signal used to transmit information in space. The carrier signal is modulated to perform various types data. AM and FM are examples of such modulations used to broadcast radio waves. Let's look at an example to understand this concept better. A radio antenna is required to receive signals from AM and FM stations. This makes the radio capable of picking up a range of signals. The radio tuner is then used to tune to the desired frequency. The radio receiver converts the received signals into sound for the listener.
Some facts about radio waves.
◾The length of radio waves refers to the distance from one peak to another in the electric field of the wave. It ranges from 1 mm to 100 kilometers.
◾ The frequency of radio waves is the degree of proximity of these waves. The frequency of these types of waves ranges from 3 kHz to 300 GHz. Amplitude determines the height of radio waves.
◾ The length and frequency of radio waves are inversely proportional.
◾ The misconception that radio waves are sound waves, they are electromagnetic waves.
◾ Radio waves can travel long distances with minimal energy consumption.
◾ A radio wave travels from the Earth to the Sun in 8 minutes.
◾ FM has more high quality sound compared to AM.
◾ AM is cheaper than FM and can be transmitted over long distances without modification.
◾ A radio wave is almost 100,000 times longer than a visible light wave.
◾ Radio waves can travel at different frequencies.
◾ Radio waves can be generated naturally through the use of astronomical bodies or lightning.
◾ The use of radio waves is subject to various laws. This is done to avoid mutual interference between different frequencies.
◾ Radio waves are used in telescopes, radios, x-ray machines, cell phones, and radio-controlled toys.
◾ Astronauts use radio waves to communicate with the earth.
◾ Airplanes and large ships use a radio compass during navigation.
◾ Antennas and telescopes also use radio waves to transmit and receive data.
