Menu English Ukrainian russian Home

Free technical library for hobbyists and professionals Free technical library


ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
Free library / Schemes of radio-electronic and electrical devices

How to shorten a dipole. Encyclopedia of radio electronics and electrical engineering

Free technical library

Encyclopedia of radio electronics and electrical engineering / Antennas. Measurements, setup and matching

Comments on the article Comments on the article

If an ordinary half-wave vibrator does not fit between the suspension points, you can use a shortened antenna, the conductors of which are bent in the form of a broken line (Fig. 1, a) or a meander (Fig. 1.6).

How to shorten a dipole
Fig. 1

Studies have shown that with the same electrical length 2Le (for a conventional vibrator it is equal to the geometric length 2Lg, and for a "broken" one - the sum of the lengths of all its constituent segments), the "broken" antenna resonates (the input impedance becomes purely active) at a smaller size 2L,. Such an antenna with an electrical length of 2Le=0,58L and a size of l=0,0416L has an angle of half radiation power (in a plane perpendicular to the figure) of about ±41° (for a conventional half-wave dipole - ±39°).

The gain with respect to an isotropic radiator is 2 dB and the input impedance at resonance is 46 ohms with a geometric length of 2L = 0,38L. An increase in the value of 2Le to 0,67L (l= 0,0416L) leads to a slight expansion of the directivity pattern (up to ±42°) and a decrease in the gain to 1.95 dB, and the input impedance to 37 Ohm (at 2Le=0,33L).

Similar results were obtained for a vibrator bent in the form of a meander with a size l=0,0133l (2Le=0,7L). As can be seen from fig. 2. The active resistance of such an antenna at resonance (2Lg = 0,35L) is approximately 43 ohms. The directivity pattern and gain are approximately the same as those of a "broken" vibrator with an electrical length of 2Le=0,67L.

How to shorten a dipole
Fig. 2

The examples given show that the described method can reduce the size of the antenna by about 30% while maintaining the directional properties and reducing the input impedance to values ​​that allow using a coaxial cable with a characteristic impedance of 50 Ohms as a feeder.

Literature

  1. Radio No. 6 1986, p.64

Publication: N. Bolshakov, rf.atnn.ru

See other articles Section Antennas. Measurements, setup and matching.

Read and write useful comments on this article.

<< Back

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

CIA in the fight against global warming 04.08.2013

The US Central Intelligence Agency is studying several projects that can reverse or at least slow down the negative processes of global warming. But so far, there are many questions about the participation of intelligence officers in potentially destructive activities.

American intelligence officers, together with NASA and specialists from the US National Academy of Sciences (NAS), launched a project to study several options for geoengineering intervention in the global climate of the planet in order to reduce or "cancel" the dangerous side effects of the technogenic activities of our civilization. Apparently, the involvement of the CIA means that the US government is seriously concerned that global warming could adversely affect international security, including the national security of the United States itself. In particular, in some regions, ice and snow cover may melt, which can lead to conflicts over new territories and sea routes. First of all, this concerns Russia and Canada. Also, wars and humanitarian crises can start because some large regions receive more rainfall and others less.

Geoengineering is an activity aimed at changing the climate of the entire planet or a vast region. The current NAS project has no such plans, at least not yet, but scientists and the CIA will spend $630 and 000 months studying options for such an impact on the planet. In particular, we mean options with the release of particles into the atmosphere that reflect sunlight or the creation of installations that absorb excess carbon dioxide. In addition to studying ways to combat global warming, the aim of the project is to assess the possible negative consequences of global warming.

It should be noted that earlier the CIA was already interested in the problem of global warming and even had a research center dealing with this problem. However, the center was closed last year by members of the US Congress who objected to the involvement of intelligence officers in such activities. It is not yet known how American politicians will react to the new CIA initiative, and whether individuals, public organizations and the media will be interested in this issue.

It should be noted that the US military and intelligence agencies have the greatest experience in climate change. In particular, during the Vietnam War, the US Air Force, in accordance with the plan of the CIA, not without success, caused heavy rains that washed away the guerrilla trails. Recently, many more large-scale geoengineering projects have appeared. For example, it is proposed to sow part of the ocean off the coast of Canada with plankton, which will "suck" carbon dioxide from the air.

Unfortunately, it is still difficult to assess the consequences of such serious interventions in the climate and the probability of causing an ecological catastrophe is high. A case is already known when businessman Russ George from California, secretly from the world community and by deceiving local residents, poured "feeding" for plankton into the Pacific Ocean - 110 tons of ferrous sulfate. According to him, this led to the blooming of plankton on an area of ​​10 thousand square meters. km. While the consequences of this unauthorized experiment are being studied (only a year has passed), scientists fear that irreparable damage may be caused to the nearby richest ecosystem of the Queen Charlotte Islands.

Other interesting news:

▪ AMD Trinity APUs

▪ Luminous Wound Dressing

▪ Firefly Shine Synchronization

▪ Smart portable storage for potatoes and onions

▪ Innovative production of 3D nanochips

News feed of science and technology, new electronics

 

Interesting materials of the Free Technical Library:

▪ section of the site Car. Article selection

▪ article Get rich! Popular expression

▪ article Where can I see fish fights? Detailed answer

▪ article Japanese cinnamon. Legends, cultivation, methods of application

▪ article Connecting cords. Encyclopedia of radio electronics and electrical engineering

▪ article Thermostat for a low-voltage soldering iron. Encyclopedia of radio electronics and electrical engineering

Leave your comment on this article:

Name:


Email (optional):


A comment:





All languages ​​of this page

Home page | Library | Articles | Website map | Site Reviews

www.diagram.com.ua

www.diagram.com.ua
2000-2024