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Antennas. Schemes, articles, descriptions

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Antennas

We recommend reading in our Free Technical Library:

Homemade wind turbine. Introduction



Section Alternative energy sources. In those rural areas where there is no electricity to directly power the radios, and there is no way to charge the batteries, you have to resort to powering the receiver from dry cells and batteries. Such cells and batteries are relatively expensive and usually expire after 3-4 months. they are out of order. It is much more expedient in such cases to acquire a low-power wind-electric charging installation, which, if necessary, can be made by one's own forces and means. ... >>

Ultra low frequency metal detector



Section Metal detectors. This metal detector is built on the principle of changing the beat frequency of two generators. The scheme of its operation is simple: the signals from the search and reference generators enter the mixer, which generates a difference frequency signal at the output. When metal approaches the coil of the search generator, its frequency changes, and as a result, the difference frequency relative to the reference generator, which, as a rule, lies in the audio range. At first glance, it seems obvious that the sensitivity of a metal detector is greater, the higher the frequency of its generators. Actually it is not. With increasing frequency, the absorption of electromagnetic waves by the soil increases. Therefore, it becomes more difficult to get rid of unwanted self-synchronization of generators due to communication through power circuits and parasitic mounting capacitances. ... >>

modem for package



Section Nodes of amateur radio equipment. In my previous article [1], a packet modem scheme was published for operating in the VHF band at a speed of 1200 baud. Somewhat later, the circuit was successfully tested for operation in the KB range at a speed of 300 Baud. which allowed the development of a universal 1200/300 baud modem. characterized by simplicity and reliability ... >>

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Antenna Articles

 


 

HF antennas

Articles on HF antennas; HF antenna circuits; descriptions of HF antennas: 170 articles

 


 

VHF antennas

Articles on VHF antennas; VHF antenna schemes; descriptions of VHF antennas: 114 articles

 


 

Television antennas

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

 


 

Antenna amplifiers

Articles on antenna amplifiers; antenna amplifier circuits; descriptions of antenna amplifiers: 31 articles

 


 

Antennas. Measurements, setup and matching

Articles on adjustment of antennas; schemes for setting up antennas; antenna adjustment descriptions: 28 articles

 


 

Antennas. Theory

Articles on antenna theory; descriptions on antenna theory: 19 articles

 


 

Antennas. Technology

Articles on antenna technology; antenna technology descriptions: 11 articles

 


 

Latest news of science and technology, new electronics:

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 ... >>

Electron spin for quantum information transfer 18.05.2024

The transfer of quantum information remains one of the key tasks of modern science. Recent advances in the use of electron spin to expand the capabilities of information transfer in quantum systems have become very important. Researchers at Lawrence Berkeley National Laboratory are pushing the frontiers of quantum information science by experimenting with the possibilities of electron spin. Electron spin, a natural quantum bit, is a potentially powerful means for storing and transmitting information in quantum systems. Magnon wave packets, collective excitations of electron spin, have revealed their potential to transmit quantum information over significant distances. The work of Berkeley Lab researchers has revolutionized the way such excitations propagate in antiferromagnets, opening up new prospects for quantum technologies. Using pairs of laser pulses, scientists disrupted antiferromagnetic order in one place and simultaneously studied it in another, creating ... >>

Sound-absorbing silk 17.05.2024

In a world where noise is becoming increasingly intrusive, the emergence of innovative materials that can reduce its impact is of great interest. MIT researchers have unveiled a new sound-absorbing silk fabric that promises to revolutionize quiet spaces. The Massachusetts Institute of Technology (MIT) has made significant breakthroughs in the field of sound absorption. Researchers have developed a special silk fabric that can effectively absorb sound and create cozy, quiet environments. The fabric, thinner than a human hair, contains a unique vibrating fiber that is activated when voltage is applied to it. This feature allows the fabric to be used to suppress sound waves in two different ways. The first method uses fabric vibrations to generate sound waves that cover and cancel out unwanted noise, similar to noise-canceling headphones. This p ... >>

Random news from the Archive

Ultraviolet for myopia 12.12.2016

Scientists from JAMA Ophthalmology compared the medical history of more than three thousand people living in various European countries, from Norway to Greece. All of them were on average 65 years old, and several hundred of them suffered from myopia.

The researchers asked everyone about their diet, income level, past illnesses and a host of other things - among other things, the respondents were asked to indicate how much time per day (more precisely, from 9 am to 5 pm) they spent outside the home starting at the age of 14. At the same time, their blood was taken to analyze the level of vitamin D (which, as we know, is synthesized in skin cells under the influence of ultraviolet radiation).

Knowing, at least approximately, how much time a person spends outdoors, and knowing in which geographical area he lives, it is possible to calculate the amount of ultraviolet radiation that he received on average every day throughout his life.

It turned out that those who received large doses of ultraviolet radiation in their youth were less likely to have myopia - by the age of 65 they saw better than others who had not received UV radiation at one time. It would be logical to assume that the whole point is in that very vitamin D, especially since, according to some sources, the higher its level, the lower the likelihood of myopia. However, this time, no such pattern could be found: the level of vitamin D did not correspond in any way to whether the person’s eyes were healthy or not.

It can be assumed that UV rays act differently; some of the earlier research suggests that ultraviolet light specifically activates eye cells and regulates the growth of the eye so that it becomes resistant to myopia. However, no matter how tempting the "ultraviolet prophylaxis" of myopia may look, all these dependencies and regularities need to be repeatedly rechecked.

One cannot speak of a causal relationship between one and the other, all we know is that the two parameters - the amount of ultraviolet light and the likelihood of myopia - are somehow related to each other. It is also worth noting that the authors of the work judged by the dose of ultraviolet radiation, based on the memories of the study participants, how much time they spent in the sun forty years ago, and such data still cannot be called accurate enough.

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