Effective antenna for five bands. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / HF antennas

 Comments on the article

How to improve the performance of the Ground Plane vertical antenna? If the antinode of the current is removed from the roof, that is, the sections of the vertical pin and horizontal beams, through which the largest currents flow, are raised higher, then the heating losses of close objects will decrease.

Since the losses will decrease, the number of horizontal beams of such an antenna can be reduced to two.

Fig. 1

An inverted Ground Plane for one range is shown in fig. 1. The section of the antenna cord that forms the rays is stretched with a nylon fishing line with a diameter of 0,9-1 mm.

The inner conductor of the coaxial cable is connected to the middle of the segment. The sheath remains loose and must be well insulated. The cable is led vertically down or obliquely in a plane perpendicular to the segment. At a distance of a quarter of a wave from the upper end of the cable, a “plug” is turned on, blocking the path of high-frequency currents on the outer surface of the cable sheath. . For the “plug” device, the cable is passed once or twice through a large-diameter ferrite ring (best of all, K32X16X8 from 30VCh-2 ferrite), on which a loop coil connected to the capacitor is also wound.

A loop coil can also be made in the form of a round frame of two or three tightly compressed turns of well-insulated wire (a thin coaxial cable with polyethylene outer insulation is suitable). The feeder in the right place is rolled into a coil of the same diameter as the loop coil. The coil and the contour coil are applied close to each other and fastened with insulating tape.

The circuit capacitor must be sufficiently high-voltage and good quality: with a transmitter power of 100 W, the voltage across it can reach 400-500 V.

Approximate data for loop coils made of stranded wire with a diameter of 2 mm are given in the table.

The "cork" does not affect the characteristics of the cable, since it is outside the field of internal conductors. Below the cork, the surface of the cable is practically neutral, so the length of the feeder is not limited and it can lie on the roof, touch the wall of the house, etc.

It is not difficult to move from a single-band antenna to a multi-band one. To do this, in the right places along the length of the beams and the cable, install "plugs" on the appropriate ranges. It is also possible to replace the system of plugs with a system of beams of different lengths connected at the antinodes of the current. The author preferred a combination - a horizontal part in the form of rays of different lengths, and a vertical one with a set of "plugs". A diagram of such an antenna for five bands is shown in Fig. 2.

Fig. 2

As can be seen from the figure, the horizontal part consists of three pairs of beams 10, 5 and 2,5 m long each (the total antenna span is 20 m). The first pair is for the 7 and 21 MHz bands, the second for 14 MHz and the third for 28 MHz. "Plugs" are located on the feeder at distances (from the upper end): 7,5 m - for 28 MHz (the length of the vertical part is 0,75l, which gives an additional gain); 3,5 or (better) 10,5 m - for 21 MHz; 5 m - for 14 MHz, 10 m - for 7 MHz. These dimensions are indicative and should be adjusted during setup. To work at 3,5 MHz, the cable braid is grounded immediately after the bottom plug - connected to a metal fence or reinforced concrete reinforcement.

The input impedance of the antenna on four high-frequency bands is close to fifty ohms, so it is best to use a cable with the same impedance as a feeder. Input impedance in the 3,5 MHz band is highly dependent on local factors and can exceed 100 ohms.

Antenna tuning is reduced to determining the minimum SWR in each band. Then you should move the plugs by a distance proportional to the shift of the minima and check the SWR again. Tuning to 3,5 MHz can be done either by shifting the ground point or by adding a lumped inductance or capacitance to the ground circuit.

Author: Y. Medinets (UB5UG), Kiev; Publication: N. Bolshakov, rf.atnn.ru

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 Metal improved with ceramics 09.01.2016 Researchers at the University of California, Los Angeles (UCLA) have succeeded in improving the properties of a metal using ceramic nanoparticles. The resulting ceramic-metal composite turned out to be very strong and light. It contains magnesium and silicon carbide (86% and 14% respectively), and applications include aircraft and spacecraft, automobiles and mobile electronic devices. It was possible to increase the specific strength and the modulus of longitudinal elasticity due to the introduction of silicon carbide nanoparticles into the metal. The illustration shows the deformation of a metal microparticle (left) and a composite in which such a particle is surrounded by ceramic nanoparticles (right). The diameter of the metal column is about 4 µm. The idea of ​​improving the structural qualities of a metal by adding ceramics is not new, but its implementation is associated with solving the problem of a uniform distribution of nanoparticles that tend to form "lumps". Scientists from UCLA have developed a new method that ensures uniform distribution of nanoparticles in the melt. It is built on the use of the kinetic energy of particles. To further increase the strength, compression of the material by means of severe plastic deformation is used. Scientists note that the method they have developed can be transferred to industrial production, and the results obtained are only the first steps in mastering a new class of materials.

Other interesting news:

▪ Affordable Antec Power Supplies with 80 PLUS Platinum certification

▪ Prospects for the development of smart watches

▪ Molecular sensor for smartphones

▪ Singapore launches iPhone 4S without camera

▪ Cats watch their owners without even seeing them

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Lightning protection. Article selection

▪ article Words and illusions perish, facts remain. Popular expression

▪ article The wife of which Roman emperor kept a brothel and worked there herself as a prostitute? Detailed answer

▪ article St. John's wort perforatum. Legends, cultivation, methods of application

▪ article Multiband speaker systems. 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