Low-noise antenna amplifier of the 23rd UHF channel

Encyclopedia of radio electronics and electrical engineering / Antenna amplifiers

 Comments on the article

Gain 18 and 21 dB in voltage. Mounted on a mast near the antenna. Two outputs for coaxial drop cables for 2 TVs. Power must be supplied through both cables (for independent viewing) through a simple adapter and decoupling diodes. Loop and communication lines are made of tinned wire pieces approximately 1,5 mm in diameter (they are soldered from feed-through capacitors during their refinement in order to miniaturize). The output communication line is located close to the last contour line.

Structure:

Mounting of the amplifier is carried out by hinged method. The lower terminals of the KPM 2 / 7pF are completely cut off and the upper terminal is bent and soldered as in the figure. The board, made of double-sided foil fiberglass 1,5 mm, is wrapped with a strip of tinned sheet 20 mm wide and soldered along the seam on both sides. Parts that are not visible in the upper compartment are located in the pallet. Small circles are the ends of feed-through capacitors, on which the entire installation is hung. Above the board, the ends of the feedthroughs protrude by 0,5-1mm and are soldered in a circle on both sides of the board. The height of the contour lines above the board is determined by the height of the trimmer capacitors. The top compartment is divided in half by a screen with a small hole for the condenser at the bottom. On both sides, the amplifier is closed and sealed with tin covers in which holes are drilled above the trimmers. Finally, the amplifier is adjusted already with covers. At the cable connection points, the tin is pierced with an awl and unfolded with some kind of conical tool. Tubes made of tin are soldered into the holes according to the diameter of the cable. The cable cores are connected to the line on the support patches 3x3 mm from the scraps of the board soldered to it. The box is strong, but needs protection from corrosion.

I ask you to give some recommendations regarding the UHF amplifier for channel 23.

Questions:

1. Is it possible to use GT346A transistors in the amplifier and does it require any changes in the circuit or design of the amplifier?

2. How to properly set up this amplifier using the X1-50 device, what adapters, probes, etc. needed for proper setup?

Replies:

1. Yes, GT346A transistors can be used instead of KT3109A without any changes in the circuit. It is only necessary to make the output of the emitter VT1 and the base VT2 as short as possible, for soldering to feed-through capacitors. For planar transistors KT3109A, I shortened these conclusions to 2 mm, and since the conclusions are spatially spaced, they are easy to quickly solder. And yet, when replacing 2-3 dB of gain will be lost. If you make an amplifier with one output, then on the contrary, the gain will be 3 dB more.

2. I am not familiar with X1-50, I worked with X1-44, X1-55. From X1-44 I had only a generator unit and I used a homemade detector (described on the site) to a simple N.Ch. oscilloscope. I applied the signal to the input of the amplifier through two attenuators of 20 dB each, which made it possible to avoid overloading the amplifier and at the same time provided a large signal for monitoring and synchronizing the oscilloscope taken from the detector BEFORE these attenuators. The output included a load (2 pcs.) 75 Ohm and a self-made oscilloscope detector to it. Connected pairs of circuits at the input and output of the amplifier tuned to the operating frequency. By changing the distance between the lines of the contours, a flat top of the resonance curve was achieved at a given bandwidth (while adjusting the resonance). The distance between the lines is approximately 10 mm.

If you reduce the tap connection in the input circuit to 1/3 and increase the resistors R9 and R10 to 2 kOhm, then you can get the amplifier bandwidth of only 8-10 MHz, i.e. one channel and still get 24-26 dB of gain. This is useful for interference from adjacent frequency channels. But I limited myself to the 24 MHz band (3 channels), having somewhat lost the gain, but at the same time, large temperature differences, when the amplifier is installed outdoors, do not affect the gain in any way with a possible temperature mismatch of the circuits. Finally, the amplifier was adjusted with the covers closed and soldered, through the holes opposite the tuning capacitors, and then they were also soldered with patches for sealing. KPM type trimmers are the smallest I have ever had. According to this scheme, but with a single output, I made amplifiers for any UHF channel, changing only the contour settings and easily getting 24-26 dB of gain, which is a lot at these frequencies! The amplifiers were placed directly on the receiving antennas, and the power and signal went through one cable and received a big signal / noise gain on the TV. I did not use connectors at the input and output, soldering the cable directly to the amplifier.

Good luck and welcome!

Author: E.Shustikov, UO5OHX ex RO5OWG; Publication: shustikov.by.ru

See other articles Section Antenna amplifiers.

Read and write useful comments on this article.

<< Back

Latest news of science and technology, new electronics:

Energy from space for Starship 08.05.2024

Producing solar energy in space is becoming more feasible with the advent of new technologies and the development of space programs. The head of the startup Virtus Solis shared his vision of using SpaceX's Starship to create orbital power plants capable of powering the Earth. Startup Virtus Solis has unveiled an ambitious project to create orbital power plants using SpaceX's Starship. This idea could significantly change the field of solar energy production, making it more accessible and cheaper. The core of the startup's plan is to reduce the cost of launching satellites into space using Starship. This technological breakthrough is expected to make solar energy production in space more competitive with traditional energy sources. Virtual Solis plans to build large photovoltaic panels in orbit, using Starship to deliver the necessary equipment. However, one of the key challenges ... >>

New method for creating powerful batteries 08.05.2024

With the development of technology and the expanding use of electronics, the issue of creating efficient and safe energy sources is becoming increasingly urgent. Researchers at the University of Queensland have unveiled a new approach to creating high-power zinc-based batteries that could change the landscape of the energy industry. One of the main problems with traditional water-based rechargeable batteries was their low voltage, which limited their use in modern devices. But thanks to a new method developed by scientists, this drawback has been successfully overcome. As part of their research, scientists turned to a special organic compound - catechol. It turned out to be an important component that can improve battery stability and increase its efficiency. This approach has led to a significant increase in the voltage of zinc-ion batteries, making them more competitive. According to scientists, such batteries have several advantages. They have b ... >>

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, ... >>

Random news from the Archive Super flexible and fire resistant wood 29.01.2022 Chinese scientists have made a breakthrough in the creation of wood composites. They invented a technology that makes wood flexible while protecting it from the effects of fire and fungus.  Chinese researchers took samples of tropical balsa wood up to five millimeters thick. Then they were placed in a special alkaline solution at a certain temperature for 12 hours. After that, the wood samples were filled with a new sample hydrogel. It was he who led to the fact that the material did not get wet, protected from ignition in an open fire and at the same time had excellent flexibility.  According to Chinese scientists, a tree treated in this way can bend at a temperature of minus 50 degrees Celsius. And mold does not appear on it even if you leave such material in a room with a humidity of 90% for two and a half months.

Other interesting news:

▪ memory enhancing molecule

▪ Created a hormone of trust

▪ Silicon shortage for solar energy

▪ New principle of X-ray generation

▪ Prosthetic eye with night vision

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ site section Measuring equipment. Article selection

▪ article Promised Land. Popular expression

▪ article What is heredity? Detailed answer

▪ article Working with a blowtorch. Standard instruction on labor protection

▪ article Alternative energy in the country. Choosing your own power system. Encyclopedia of radio electronics and electrical engineering

▪ article Digital output voltage control for L200. 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