Switchable antenna BOX for 80 meters. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / HF antennas

 Comments on the article

The article describes the "Box" antenna for low bands, which has excellent characteristics for working with DX. The directivity of the antenna is such that it has gain in an azimuth angle greater than 180°. Having such a wide radiation pattern, it is possible only by switching it to two directions to block all azimuths.

The physical implementation of switching is very simple (Fig. 1). It is necessary to switch the feeder using a relay, disconnecting it from the active element (and turning it into a reflector) and connecting it through another gamma matcher to the reflector (and turning it into an active element).

Fig.1 (click to enlarge)

If you want the gain to be directed to the left, feed the left element; if to the right - power the right one. An unpowered element remains broken at the feed point. This is important because it is necessary that there is an electrical break between the coax cable and the reflector feed point. The analysis shows that shorting the power point of the passive element gamma-matcher requires an additional gamma-matcher wire to obtain the required reflector detuning. Naturally, in reality it is not very practical to change the feed point of a coaxial feeder when a direction change is necessary. However, the requirement to leave an unused power point open limits the range of possible switching devices. Recall that a shortened section of a quarter-wavelength transmission line looks like an open circuit from the other end and serves as a key in the development of a switching device.

In the middle between the two vertical drops of the "Box" antenna is a shielded box containing two switches and 50 ohm l/4 cables running from each gamma matcher to the box. One of the switches either connects this cable to the cable going to the transceiver, or, in the second position, shorts it to ground. The second switch does the same, but in reverse order. If these conditions are met, one gamma match will be powered while the other will be broken at the feed point. When switching, they change places, as well as the radiation pattern.

The control signals are fed through the antenna's coaxial power cable. Therefore, special isolation is required to separate the signals.

The vertical radiation pattern for the range of 40 m is shown in Fig. 2, and the azimuth - in Fig. 3. Both diagrams are superimposed on the diagram of an ordinary half-wave dipole.

Table 1 shows the geometric dimensions of the antenna for the low-frequency bands, and Table 2 shows the dependence of its parameters on the frequency in the 40 m range.

The "Box" antenna has relatively good performance at 40m, but in this range the dipole at 40 feet above the ground is already a worthy contender.

Already on this band, it has less gain compared to the 80 m version. The antenna requires a quality ground. A simple pair of opposite radials may not be enough.

As mentioned at the beginning of the article, the antenna is ineffective on the 20 m band and on higher frequencies. At 20 meters it loses about 3 dB to a typical 50-element Yagi at 10 feet. Designing it for two meters is a waste of time. However, for the 160, 80 and even 40 m ranges, its alternatives are much worse. Build it for one of the low bands and you are a "giant" DX!

Author: T.HULICK (W9QQ); 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 Samsung MMS 8 Gb 20.09.2006 Samsung announced the release of the most capacious MMC format cards in the industry. Created on the basis of technology MLC (Multi-Level Cell) 8-gigabyte cards should appear on the market in the third quarter of this year. They will be used in mobile phones, MP3 players and other devices.

Other interesting news:

▪ exhaust ink

▪ Video Glasses

▪ BMW Electric Vehicle Wireless Charging

▪ Camera with glasses

▪ New SPM Series Power Modules

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Clocks, timers, relays, load switches. Article selection

▪ Star Wars article. Popular expression

▪ What were the specific features of Europe in the Late Middle Ages (XVI-XVII centuries)? Detailed answer

▪ article Colds. Health care

▪ article Soft light. Encyclopedia of radio electronics and electrical engineering

▪ article Characteristics of asynchronous motors with combined windings. Encyclopedia of radio electronics and electrical engineering

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