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Television antennas. Schemes, articles, descriptions

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Television antennas

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144 MHz transmitter on a 74HC00 chip



Section Civil radio communications. Digital microcircuits of the 74HC series can operate at frequencies up to 150 MHz and higher. This allows you to build on their basis low-power transmitter circuits operating at frequencies of the 2-meter range (144 MHz) ... >>

Small-sized frequency meter



Section Measuring technology. The frequency meter measures the frequency of the input signal in the range of 10 Hz...50 MHz with a counting time of 0,1 s and 1 s, frequency deviation within ±10 MHz, and also counts pulses with display of the counting interval (up to 99 s). The input impedance is 50 ... 100 ohms at a frequency of 50 MHz and increases to several kilo-ohms at the lowest frequency of the range. The frequency meter circuit is shown in fig. 1. The main element is the PIC12F629 (DD1) microcontroller, working according to the program, the codes of which are given in the table. Frequency measurement is carried out by counting the number of pulses in a fixed time interval. Two intervals are used - 0,1 si 1 s. In the first case, to obtain the frequency, the number of pulses is multiplied by 10, in the second, the values ​​of the number of pulses and frequency are the same ... >>

Adjustable voltage stabilizers on the chip KR142EN19, 2,5-30 volts



Section Voltage stabilizers. The scheme of a low-power adjustable voltage regulator is shown in the figure. It is implemented on the KR142EN19 microcircuit, which is a parallel voltage regulator, with a stabilization current of 1 ... 100 mA and an output voltage range of 2,5 to 30 V. The maximum power dissipated by the microcircuit is 0.4 W, the differential resistance is not more than 0.5 Ohm. The control input current of the microcircuit can be 5 μA, so it is advisable to choose a current through the resistive divider of at least 0.5 mA. The resistance of the ballast resistor R1 can be calculated by the formula: R1 \u1d (Uin. - Uout.) / (Ist. min.. + Idel. + In. max.). Where Ist. min.. - can be taken equal to 2.5 mA. The stabilization coefficient is calculated in the same way as for parametric stabilizers on zener diodes. The output voltage of the stabilizer is determined by the formula: Uout.=1•(2+R3/RXNUMX) ... >>

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Articles on television antennas

Articles on television antennas; schemes of television antennas; descriptions of television antennas: 64 articles

 


 

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Latest news of science and technology, new electronics:

Blinking of the magician and his audience 19.05.2024

Magic and illusions have always captured the attention of the public, but what happens behind the scenes of the magician and in the brains of his audience? Scientists from the UK decided to solve this mystery by conducting a new study involving ten illusionists of varying experience. Illusionists, some of whom had been practicing magic for more than half a century, others for only six months, were invited to demonstrate the same trick - the popular coin trick. Recordings of their performances during training and on stage showed that each of them began to blink significantly more often at the moment of performing the trick. The study's findings indicate that magicians' blink rate may be related to unconscious aspects of their performance. At the same time, as scientists have found, spectators also begin to blink more often, following the movements of the illusionist. This observation supports the idea that magicians may be catalysts for blinking in audiences. Additional research has shown that magicians blink more often during ... >>

Ultrasonic coffee machine 19.05.2024

Iced coffee has become an integral part of coffee culture in recent years. Therefore, engineers from the University of New South Wales decided to improve its preparation. They have developed an ultrasonic coffee machine that reduces the cold brew time for ground coffee beans from 12-24 hours to significantly less time. Iced coffee, or "Cold brew", is popular due to its smoothness, low acidity and low bitterness. It is prepared by steeping ground coffee in cold water for a long time. Unlike traditional hot brewing, which often imparts bitterness to coffee, cold brewing extracts more delicate and complex flavors from the coffee beans. The innovative system, presented by a team of engineers, introduces ultrasonic technology into the coffee preparation process. The system uses ultrasonic waves to speed up the process of extracting oils, flavor and aroma from ground coffee. This allows you to significantly reduce the time ... >>

The speech of sperm whales is similar to that of humans 18.05.2024

In the world of the ocean, where the mysterious and unknown coexists with the studied, sperm whales, with their huge brains, are of particular interest to science. Researchers, working with a huge array of audio recordings collected during the Dominica Sperm Whale Project (DSWP) - more than 8000 recordings, seek to unravel the secrets of their communication and understand the structure and complexity of the language of these mysterious creatures. By studying in detail the recordings of 60 sperm whales in the eastern Caribbean, scientists have revealed surprising features of their communication, revealing the complexity of their language. "Our observations indicate that these whales have a highly developed combinatorial communication system, including rubato and ornaments, which indicates their ability to quickly adapt and vary during communication. Despite significant differences in evolution, sperm whales have elements in their communication that are characteristic of human communication," says Shane Gero, a biologist at Carleton University and director of the CETI project. Issl ... >>

Random news from the Archive

Heart beats to conception 02.06.2017

The menstrual cycle is associated with the periodic maturation of eggs in the ovaries: the egg matures in a special structure of the ovary called the follicle, then it leaves the ovary and moves towards the uterus - ovulation occurs, and it is at this moment that the reproductive system is especially ready for conception.

At the same time, the level of hormones that control reproduction (estrogen, progesterone, etc.) changes in the body: some of them are synthesized in the brain, some in the reproductive system itself; and it would be strange to believe that they do not affect anything other than the reproductive system.

For example, not so long ago we wrote that regular fluctuations in estrogen in the body of women are accompanied by changes in the brain, namely, in the hippocampus, one of the main centers of memory. Some experts believe that women's sexual preferences also change depending on the stage of the menstrual cycle, although according to other sources there is no connection. And here is another example of how the female body reacts to the hormonal cycle. Employees at the Zurich University Hospital, along with colleagues from the biomedical company Ava AG, report that the female heart beats faster during ovulation.

In fact, similar studies have been done before, and the conclusions from them were the same - that the heart rate rises at the time most favorable for conception. However, women in such cases were usually observed in clinical laboratories and not for very long, and only during one menstrual cycle; moreover, the observations were limited only to the daytime, when the heart generally beats very differently.

The authors of the new work tried to avoid all these disadvantages by using bracelets with medical sensors that track heart rate. The experiment involved about a hundred women aged 22 to 42 who never got pregnant; they all wore the bracelet every night before bed for three menstrual cycles. They also had urinalysis done so that they could accurately assess what stage of their cycle they were in.

It turned out that the heart rate at rest in the five days before ovulation increases by 2,1 beats per minute. The rhythm continued to grow even after ovulation, at the stage of the corpus luteum (this is the name given to the gland into which the part of the ovary turns after the egg leaves it), increasing eventually by three and a half beats per minute.

Then, during menstruation, the heart rate became less frequent. Of course, the work of the heart changes under the influence of many reasons, up to whether you ate a heavy meal before bedtime and whether you did any physical exercises, but the researchers assure that they took into account all such factors and that an increase in the rhythm by 2,1-3,5, XNUMX strokes - quite reliable "ovulatory" increase.

Perhaps with the help of sensors that record the work of the heart, women will be able to better determine the time to conceive (or more accurately protect themselves). However, more research is still needed here with a large number of volunteers to finally make sure that such a relationship between heart rate and the phases of the menstrual cycle really takes place.

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