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VHF antennas. Schemes, articles, descriptions

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VHF antennas

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Economic receiver for CB radio station

Section Civil radio communications. The ability of a portable radio station to be ready to receive a call from a correspondent at any time depends on its power consumption in standby mode. Usually this is only 10...30 hours of work. Next is replacing the power source. This autonomy extremely limits the scope of application of this technology. In Fig. Figure 7 shows a schematic diagram of an economical receiver for a single-channel CB radio station. Transistors VT1 and VT2 are included in a radio frequency amplifier (RFA), its circuits L2C3 and L3C4 are tuned to fк - the frequency of one of the communication channels allowed in this range (today there are about 160 of them). The balanced mixer and local oscillator are made on the DA1 chip ... >>

Advantages of fluorescent lamps

Section Fluorescent lamps. The widespread use of LLs is due to the fact that they have a number of significant advantages over classic incandescent lamps: firstly, they are high efficiency, the efficiency is 20-25% (for incandescent lamps about 7%), and the light output (i.e. the amount of emitted lumens per unit of power consumption) lies in the range of 70-105 lm/W (for incandescent lamps 7-12 lm/W), secondly, a long service life - up to 20000 hours (for incandescent lamps -1000 hours and strongly depends on voltage food). It is known that optical radiation (ultraviolet, visible, infrared) has a significant physiological and psychological effect on a person (his endocrine, autonomic, nervous systems and the entire body as a whole), mostly beneficial. Daylight is the most beneficial. It affects many life processes, metabolism in the body, physical development and health. But active human activity continues even when the sun disappears behind the horizon. Daylight is being replaced by artificial lighting ... >>

Determining the intercom configuration

Electrical section. Delivery of intercoms to the consumer is carried out, as a rule, in the form of separate blocks, from which intercom systems of various configurations can be built, and the use of microprocessor technology and modern technologies gives intercoms wide functionality. It is very difficult to understand all this diversity and offer an acceptable option to the customer (in most cases, unfamiliar with this technique). It is recommended to start acquaintance with a certain intercom model by clarifying the following details: the maximum number of subscribers that the intercom can serve (it must be greater than or equal to the actual number of subscribers served), the required number of subscriber units (several units can be installed at the request of the subscriber), device type identification of the landlord. It can be the following miracles of technology: a code, a regular key, an optical or magnetic card, a Touch memory electronic key, the maximum number of codes, which must exceed the maximum number of subscribers served ... >>

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Articles on VHF antennas

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

Nanotube switch 13.01.2006

French researchers have made a switch from a nanotube. Scientists from the research division of the French Commissariat for Nuclear Energy have made an interesting electromechanical device out of a carbon nanotube.

A successful experiment was preceded by an accurate calculation. He showed that if both ends of a nanotube are fixed, suspended above a conductor, and an electrical voltage is applied to it, the nanotube will bend under the action of an electrostatic force.

The magnitude of this bend can be influenced by changing the length or type of the nanotube, the potential difference, and many other parameters. Scientists have made such a device and found that the nanotube really bends. And bending over, it can touch the electrode and become a switch, that is, close the electrical network - after all, carbon is a good conductor.

Moreover, after touching the electrode, Van der Waals forces begin to act, which do not allow the nanotube to straighten out, even if the voltage in the conductor that attracted it is very small. It is this feature that allows us to hope that on the basis of such devices it is possible to create storage devices that require very little energy to store a record.

Nanoswitches will also be useful for creating ultra-low force sensors, oscillators and ultra-fast switches in communications.

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