Two antennas on one cable. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Телевидение
Comments on the article
Often in practice there is a problem of combining two antennas of different channels on one feeder. To do this, you can apply the typical scheme shown in Fig.1.
Ris.1
Coils L1 ... L5 can be wound with enameled wire with a diameter of 0,5 ... 0,6 mm on one frame, turn to turn. In this case, it should be taken into account that the distance between the ends of adjacent coils must be at least 8 mm. Frameless winding can also be used.
If there are no 12 and 20 pF capacitors at your disposal, you can get by with foil getinax or textolite. According to Fig. 2a, contact pads are cut out. The slots are 1 mm wide (according to the thickness of the cutter). According to Fig. 26, c, plates are cut out of aluminum, duralumin or brass with a thickness of 1,5 ... 2,0 mm.
Ris.2
These plates are applied from the side of the foil to the foil material, having previously placed polyethylene gaskets 0,1 mm thick. Suitable polyethylene from a conventional plastic bag. In Fig. 2a, dotted lines indicate the location of the plates on the foil. The plate according to Fig. 26 forms capacitors C3, C4, C5, the plate (Fig. 2c) forms capacitors C1 and C2. It remains to solder the coils L1 ... L5 in accordance with the diagram. Under the M4 screws for this purpose, you need to put washers made of tinned sheet, to which it is convenient to solder the coils. To protect against atmospheric moisture, it is necessary to cover the entire structure with varnish or place it in a sealed enclosure. The holes for the M4 screws on the side of the foil should be slightly countersunk so that the capacitors do not close through the plate fixing screws.
If a radio amateur needs to make capacitors for other purposes in the same way, then you need to be guided by the formula:
C=(8,85*10-3*ES)/d
where C is the capacitance of the capacitor in pF;
S is the area of the capacitor plate in mm2;
d is the thickness of the dielectric layer in mm;
E is the permittivity of the dielectric.
Ris.3
There is another option for connecting receiving TV antennas to one feeder (Fig. 3). A1 - the place of connection of the active vibrator of the antenna tuned to the X1 wave. The vibrator of the second antenna tuned to the L2 wave is connected to the A2 points. l2, l4 - balancing quarter-wave cable segments, the length of which is determined by the formula:
l=K(L/4),
where l is the length of the balancing segment;
L is the wavelength;
K - coefficient of cable shortening.
For cables with polyethylene insulation K=0,67.
Both antennas are connected to a common feeder at distances from the vibrators, which are determined from the system of equations:
where n is any integer.
It is based on the following principles:
- a quarter-wave segment of the line, loaded with resistance less than the wave resistance, transforms it into a resistance greater than the wave resistance;
- if a resistance much greater than the wave resistance is connected to the line, it practically does not load the line.
Author: A. Zherdev, Gomel; Publication: N. Bolshakov, rf.atnn.ru
See other articles Section Телевидение.
Read and write useful comments on this article.
<< Back
Latest news of science and technology, new electronics:
Alcohol content of warm beer
07.05.2024
Beer, as one of the most common alcoholic drinks, has its own unique taste, which can change depending on the temperature of consumption. A new study by an international team of scientists has found that beer temperature has a significant impact on the perception of alcoholic taste. The study, led by materials scientist Lei Jiang, found that at different temperatures, ethanol and water molecules form different types of clusters, which affects the perception of alcoholic taste. At low temperatures, more pyramid-like clusters form, which reduces the pungency of the "ethanol" taste and makes the drink taste less alcoholic. On the contrary, as the temperature increases, the clusters become more chain-like, resulting in a more pronounced alcoholic taste. This explains why the taste of some alcoholic drinks, such as baijiu, can change depending on temperature. The data obtained opens up new prospects for beverage manufacturers, ... >>
Major risk factor for gambling addiction
07.05.2024
Computer games are becoming an increasingly popular form of entertainment among teenagers, but the associated risk of gaming addiction remains a significant problem. American scientists conducted a study to determine the main factors contributing to this addiction and offer recommendations for its prevention. Over the course of six years, 385 teenagers were followed to find out what factors may predispose them to gambling addiction. The results showed that 90% of study participants were not at risk of addiction, while 10% became gambling addicts. It turned out that the key factor in the onset of gambling addiction is a low level of prosocial behavior. Teenagers with a low level of prosocial behavior do not show interest in the help and support of others, which can lead to a loss of contact with the real world and a deepening dependence on virtual reality offered by computer games. Based on these results, scientists ... >>
Traffic noise delays the growth of chicks
06.05.2024
The sounds that surround us in modern cities are becoming increasingly piercing. However, few people think about how this noise affects the animal world, especially such delicate creatures as chicks that have not yet hatched from their eggs. Recent research is shedding light on this issue, indicating serious consequences for their development and survival. Scientists have found that exposure of zebra diamondback chicks to traffic noise can cause serious disruption to their development. Experiments have shown that noise pollution can significantly delay their hatching, and those chicks that do emerge face a number of health-promoting problems. The researchers also found that the negative effects of noise pollution extend into the adult birds. Reduced chances of reproduction and decreased fertility indicate the long-term effects that traffic noise has on wildlife. The study results highlight the need ... >>
| Random news from the Archive Collision of protons is simulated
02.05.2022
Scientists from the National Laboratory. The Berkeleys used the IBM Q quantum computer to do part of the calculation for the collision of two protons. To do this, they split the effective field theory into several parts and developed an algorithm that allows certain calculations to be performed on a quantum computer.
Berkeley Lab is engaged in the study of particle physics by observing the collision of high-energy particles in the laboratory, for example, using the Large Hadron Collider in Switzerland. Scientists compare theoretical calculations of these collisions with real-life experimental results.
“One of the main challenges of this kind of calculation is that we want to describe a wide range of energies,” said Benjamin Nachman, one of the researchers. “We want to describe processes from the highest energy to the lowest energy by analyzing the corresponding particles that fall into our detector.” .
Using a purely quantum computer to solve this kind of problem would require too many qubits - modern quantum machines do not have such power. Scientists can perform these calculations on classical computers using approximations, but in this case, important quantum effects fall out of focus. Therefore, the team of physicists decided to divide the calculations between different systems, classical and quantum. Quantum calculations were carried out on an IBM Q operating with hundreds of qubits.
In the future, scientists plan to add new dimensions to the problem, break it down into more components and increase the scale of the problem. Ultimately, they expect to perform calculations on a quantum computer that are not possible with classical ones.
|
Other interesting news:
▪ A New Type of RF Power Amplifier for Mobile Phones
▪ Birds are becoming more aggressive due to global warming
▪ Brother PocketJet 7 Mobile Printer
▪ Navigation module TESEO-LIV3F
▪ New DVD recording format proposed
News feed of science and technology, new electronics
Interesting materials of the Free Technical Library:
▪ section of the website Basics of First Medical Aid (BFA). Selection of articles
▪ article Rules of behavior and actions of the population in the territory subject to radioactive contamination. Basics of safe life
▪ article Why do we wear wedding rings on the ring finger? Detailed answer
▪ article Machinist extruder. Job description
▪ article Light switch with remote control. Encyclopedia of radio electronics and electrical engineering
▪ article A simple VHF-FM radio station. Encyclopedia of radio electronics and electrical engineering
Leave your comment on this article:
All languages of this page
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua
2000-2024
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese