Single-band fast deployment antenna. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / HF antennas

Comments on the article

Most often, in forest clearings, variations on the theme of the "Inverted V" dipole or the usual dipole with two suspension points, for example, between trees, are seen. It is difficult to pull the antenna well. For field conditions, as well as in many cases for stationary installation, antennas with two attachment points are convenient: one near the transmitter (on the ground, on a window), and the second, for example, on a tree or a neighboring building. To be able to feed a half-wave dipole from one end, a quarter-wave transformer is used. Once on short waves, a quarter-wave symmetrical line (Zeppelin antenna) was used for this. Then, a metal quarter-wave glass or an all-metal two-wire line (J-antenna) began to be used on VHF. Today, for a KB antenna, it is convenient to make a matching device from a coaxial cable.

The author used a half-wave continuous vibrator with its power supply from the end in the antinode of the voltage with the help of a matching device in the form of a short-circuited quarter-wave coaxial transformer. This design allows you to place the radiating and supply-matching part of the antenna on the same straight line and suspend the antenna by pulling it at the opposite end with the help of a nylon cord previously thrown over the block.

The antenna is shown schematically in the figure.

The length of the radiating part is equal to half the wavelength in the middle of the selected range, taking into account the shortening factor (approximately 0,95). This length does not need to be changed during antenna tuning. The calculated total length of the matching loop (section A plus section B) is equal to a quarter of the wavelength multiplied by the shortening factor of the cable used, which for many brands is approximately 0,66. For a 50 ohm cable A=0,214λk, B=0,036λk, where λ is the wavelength (m), k is the cable shortening factor. For 75 ohm cable A=0,206λk, B=0,044λk.

The transceiver can be connected directly to the loop to a point at some distance from the short-circuited end. In this case, there is no need to carefully select the connection point, the antenna tuner will perform the task of optimal matching itself. If there is a need to connect a coaxial line, then in this case the proposed antenna will facilitate the matching process. The fact that the junction with the power cable is located at some distance from the radiating part of the antenna, being "in the hands" of the radio amateur, will also help here, which helps to more carefully select the resistance at the feed point, corresponding to the characteristic impedance of the feeder used.

In urban conditions, it is sometimes possible to coordinate such an antenna without leaving the apartment, in a comfortable home environment. Setting up the system consists in selecting the length of the matching cable and determining the location of the cut for connecting the power supply. This work is greatly facilitated by the use of a coaxial cable with PTFE insulation. It can be easily extended by soldering the junction over the screen braid and without fear of shorting it to the center conductor. It is advisable to use a cable with a wave impedance of 50 ohms, since the devices necessary for tuning are mainly designed for such a load. Please note that the above formulas are valid if cables with the same characteristic impedance are used for the matching loop and feeder.

The exact adjustment of the length of the loop is carried out using an RF generator and an RF voltmeter, which is connected to the output of the generator through a 1 pF capacitor. A piece of cable short-circuited at the opposite end is connected to the generator output. By gradually shortening it, they achieve maximum voltage at the operating frequency.

After specifying the length of the stub transformer, the junction of the cable with the antenna is mounted. The end of the cable is freed from the upper insulation and braid and, at a distance of about 5 cm, is tightly pulled together with a nylon fishing line with a Plexiglas insulator. Then, the antenna wire is soldered to the central conductor of the cable, which is also pulled together with an insulator using a fishing line. The junction is wrapped with electrical tape and impregnated with BF glue for the purpose of waterproofing.

To remove the mechanical load from the cable, the antenna is stretched in the direction of the source using a synthetic cord attached at one end to a hole in the insulator, and at the other, for example, to a peg in the ground. Such a semi-finished product of the antenna is hung out in space at a maximum distance from conductive objects, but in such a way that the matching cable is available for further manipulations with it.

The cable must be cut in the proportions indicated in the figure, cut the resulting parts, put them together and reconnect by soldering. At the junction, through the SWR meter, it is necessary to apply a low-power signal from the transceiver, after setting the P-loop or antenna tuner to a 50-ohm equivalent. By changing the ratio of the lengths of both pieces of cable within certain limits, it is necessary to achieve the minimum power of the reverse wave. After completing the settings, you should check the reliability of all solders and seal them.

The operating frequency band of such an antenna system on the ten-meter range was about 500 kHz, and on forty meters - 120 kHz at an SWR level of 1,5.

Author: S.Makarkin (RX3AKT), Moscow

See other articles Section HF antennas.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Machine for thinning flowers in gardens 02.05.2024

In modern agriculture, technological progress is developing aimed at increasing the efficiency of plant care processes. The innovative Florix flower thinning machine was presented in Italy, designed to optimize the harvesting stage. This tool is equipped with mobile arms, allowing it to be easily adapted to the needs of the garden. The operator can adjust the speed of the thin wires by controlling them from the tractor cab using a joystick. This approach significantly increases the efficiency of the flower thinning process, providing the possibility of individual adjustment to the specific conditions of the garden, as well as the variety and type of fruit grown in it. After testing the Florix machine for two years on various types of fruit, the results were very encouraging. Farmers such as Filiberto Montanari, who has used a Florix machine for several years, have reported a significant reduction in the time and labor required to thin flowers. ... >>

Advanced Infrared Microscope 02.05.2024

Microscopes play an important role in scientific research, allowing scientists to delve into structures and processes invisible to the eye. However, various microscopy methods have their limitations, and among them was the limitation of resolution when using the infrared range. But the latest achievements of Japanese researchers from the University of Tokyo open up new prospects for studying the microworld. Scientists from the University of Tokyo have unveiled a new microscope that will revolutionize the capabilities of infrared microscopy. This advanced instrument allows you to see the internal structures of living bacteria with amazing clarity on the nanometer scale. Typically, mid-infrared microscopes are limited by low resolution, but the latest development from Japanese researchers overcomes these limitations. According to scientists, the developed microscope allows creating images with a resolution of up to 120 nanometers, which is 30 times higher than the resolution of traditional microscopes. ... >>

Air trap for insects 01.05.2024

Agriculture is one of the key sectors of the economy, and pest control is an integral part of this process. A team of scientists from the Indian Council of Agricultural Research-Central Potato Research Institute (ICAR-CPRI), Shimla, has come up with an innovative solution to this problem - a wind-powered insect air trap. This device addresses the shortcomings of traditional pest control methods by providing real-time insect population data. The trap is powered entirely by wind energy, making it an environmentally friendly solution that requires no power. Its unique design allows monitoring of both harmful and beneficial insects, providing a complete overview of the population in any agricultural area. “By assessing target pests at the right time, we can take necessary measures to control both pests and diseases,” says Kapil ... >>

Random news from the Archive The influence of microbes on the geological processes of the Earth 08.05.2019 Microbiologists from the University of Tennessee (USA) have found that microbes play a big role - almost the same as volcanoes - in geological processes, as a result of which carbon is transported from the surface of the earth to depth. The earth contains a huge amount of carbon - even more than in the atmosphere or in the oceans, according to scientists. Some of this carbon is slowly released from rocks as CO2 (carbon dioxide) via volcanoes and hot springs, and is an important part of the natural carbon cycle. At the same time, volcanoes emit even more carbon dioxide into the atmosphere than humans. Microbes, as it turned out, can slightly delay this release. The researchers were able to draw this conclusion by studying the Costa Rica subduction zone - the place where the ocean floor (otherwise: oceanic crust) sinks under the continental plate. The results showed that microbes absorb and trap a small but measurable amount of carbon sinking in a trench off the Pacific coast of Costa Rica. Microbes can also participate in chemical processes that draw out even more carbon, leaving cement-like "veins" of the mineral calcite in the crust. The unexpected results are important for estimating how much carbon moves from the Earth's surface to its interior, especially on geologic time scales. The study is part of the Deep Carbon Meets Biological Observatory's Subduction project.

Other interesting news:

▪ Mechanical hand can feel

▪ Acer SpatialLabs View Pro 3 27D monitor

▪ Selenide phonon

▪ wine allergy

▪ Intelligent ATM Fujitsu

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Electrician's tool. Article selection

▪ article Change of milestones. Popular expression

▪ article What is the earth made of? Detailed answer

▪ article Buten fragrant. Legends, cultivation, methods of application

▪ article Parallel connection of circuit elements. Encyclopedia of radio electronics and electrical engineering

▪ couples reunion article. Focus secret

Leave your comment on this article:

All languages ​​of this page

Arabic	Hebrew	Polish
Bengali	Hindi	Portuguese
Chinese	Italian	Spanish
English	Japanese	Turkish
French	Korean	Ukrainian
German	Malay	Vietnamese

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

www.diagram.com.ua
2000-2024