Encyclopedia of radio electronics and electrical engineering / Civil radio communications

 Comments on the article

When conducting radio communications through amateur radio satellites operating on the 144/430 MHz bands for receiving and transmitting, separate antennas are usually used for these bands. When using directional antennas, it becomes necessary to move (rotate) them in elevation and azimuth, which is not easy to implement, and when using omnidirectional antennas, reception is not always satisfactory due to their relatively low efficiency. You can improve reception quality by installing an amplifier in close proximity to the antenna.

A diagram of such an amplifier is shown in Fig. 1. Its gain is 12 ... 20 dB (depending on the type of transistor), the bandwidth at the level of 3 dB is about 10 MHz, the SWR at the input at the center frequency of the range does not exceed 1,3. At the input and output of the amplifier, selective LC circuits L1C1C2 and L3C9C10 are installed, and to protect the transistor from a powerful transmitter signal at the input and output, diodes VD1VD2 and VD3VD4, respectively. The DC transistor mode is provided by the resistor R1, the supply voltage is stabilized by the integral stabilizer DA1. The amplifier is fed through the drop cable through the L4 inductor, the VD5 diode protects the device from reverse polarity of the supply voltage.

Field-effect transistors AP325A-2, ZP344A-2, AP344A-2, ZP602A-2 are applicable in the amplifier. Better results can be obtained by using an ATF-10136 low-noise field-effect transistor, designed for operation in the frequency range of 0,5 ... 12 GHz and having a gain of about 20 dB. Diode VD5 - any small-sized rectifier, trimmer capacitors - KT4-25, constant - K10-17V (without leads), resistors - P1-12, MLT or P1-4 with leads of the minimum length. Coils L1 and L3 are wound with PEV-2 0,8 wire on a mandrel with a diameter of 4 mm and contain 1,5 turns, the winding length is 5 mm. Coils L2 and L4 are wound turn to turn on a mandrel with a diameter of 2,5 mm and contain 12 ... 14 turns of wire PEV-2 0,2.

Almost all parts of the amplifier are located on one side of a printed circuit board made of double-sided foil fiberglass 1 ... 1,5 mm thick, a sketch of which is shown in fig. 2. The second side of the board does not have printed conductors, but is left metallized and connected along the contour to a common wire. Also, a plate of double-sided foil fiberglass with dimensions of 2x20 mm is soldered to it, which is used as a reference contact and diodes VD1 and VD2, capacitors C1 and C2, coil L1 are soldered to it, and through a hole in the board - the gate of the field effect transistor / T1.

The design of the amplifier is shown in fig. 3. Board 1 is soldered on both sides in a metal frame 2 made of tinned sheet or similar material. The frame has HF coaxial sockets 3 and 4 for connecting the antenna and feeder. Capacitor C1 is installed between socket XS1 and plate 5, capacitor C2 is placed on socket XS10, and C9 and L4 are placed between XS2 and the board.

The amplifier is closed on both sides with covers that are soldered to the frame. After sealing, the device must be covered with moisture-resistant paint or varnish, placed on the antenna - nests down so that water does not flow into it, and, preferably, placed under a small canopy. After connecting the cables, the connectors must be sealed with an elastic sealant.

To power the amplifier through the feeder, a power supply is installed next to the transceiver, the circuit of which is shown in Fig. 4. Coil L1 in it is similar to the coil L4 of the amplifier, capacitors C1, C2 - K10-17V. All interconnections must be of a minimum length, and for the manufacture of the device, you can use a piece of double-sided foil fiberglass, placing parts on it and soldering RF cables to it, while one of the sides must be used as a common conductor.

Setting up the device comes down to setting the drain current to 1 mA by selecting the resistance of the resistor R25. After that, a drain-source voltage of 2 V is set with a resistor R2. By building capacitors, maximum gain is achieved at the required frequency, while achieving the minimum SWR at the input with capacitors C1C2. This setting can be carried out by ear - for the best quality of weak signal reception.

To increase the stability of the amplifier to excitation, it is recommended to put a ferrite bead on the drain terminal of the transistor or include a small-sized resistor P1-4, P1-12 with a resistance of 5 ... 10 Ohm in the drain circuit.

Author: I. Nechaev (UA3WIA), Kursk

See other articles Section Civil radio communications.

Read and write useful comments on this article.

<< Back

<< Back

Latest news of science and technology, new electronics:

The world's tallest astronomical observatory opened 04.05.2024

Exploring space and its mysteries is a task that attracts the attention of astronomers from all over the world. In the fresh air of the high mountains, far from city light pollution, the stars and planets reveal their secrets with greater clarity. A new page is opening in the history of astronomy with the opening of the world's highest astronomical observatory - the Atacama Observatory of the University of Tokyo. The Atacama Observatory, located at an altitude of 5640 meters above sea level, opens up new opportunities for astronomers in the study of space. This site has become the highest location for a ground-based telescope, providing researchers with a unique tool for studying infrared waves in the Universe. Although the high altitude location provides clearer skies and less interference from the atmosphere, building an observatory on a high mountain poses enormous difficulties and challenges. However, despite the difficulties, the new observatory opens up broad research prospects for astronomers. ... >>

Controlling objects using air currents 04.05.2024

The development of robotics continues to open up new prospects for us in the field of automation and control of various objects. Recently, Finnish scientists presented an innovative approach to controlling humanoid robots using air currents. This method promises to revolutionize the way objects are manipulated and open new horizons in the field of robotics. The idea of ​​controlling objects using air currents is not new, but until recently, implementing such concepts remained a challenge. Finnish researchers have developed an innovative method that allows robots to manipulate objects using special air jets as "air fingers". The air flow control algorithm, developed by a team of specialists, is based on a thorough study of the movement of objects in the air flow. The air jet control system, carried out using special motors, allows you to direct objects without resorting to physical ... >>

Purebred dogs get sick no more often than purebred dogs 03.05.2024

Caring for the health of our pets is an important aspect of the life of every dog ​​owner. However, there is a common assumption that purebred dogs are more susceptible to diseases compared to mixed dogs. New research led by researchers at the Texas School of Veterinary Medicine and Biomedical Sciences brings new perspective to this question. A study conducted by the Dog Aging Project (DAP) of more than 27 companion dogs found that purebred and mixed dogs were generally equally likely to experience various diseases. Although some breeds may be more susceptible to certain diseases, the overall diagnosis rate is virtually the same between both groups. The Dog Aging Project's chief veterinarian, Dr. Keith Creevy, notes that there are several well-known diseases that are more common in certain breeds of dogs, which supports the notion that purebred dogs are more susceptible to disease. ... >>

Random news from the Archive AUP ESD Logic Series 27.03.2006 PHILIPS SEMICONDUCTOR Corporation has developed a series of ESD protected AUP logic circuits with a voltage of 5 kV, which is twice as high as the circuits available on the market (2,5 kV). It is pointed out that in modern devices with very low power consumption, electrostatic protection becomes a very important factor.

Other interesting news:

▪ Waterproof AC-DC adapters Mean Well OWA-90E

▪ Helioboat

▪ Laser cooler for electronics

▪ Child mode for the speedy customization of an adult

▪ Nanowires for silicon photonics

News feed of science and technology, new electronics

Interesting materials of the Free Technical Library:

▪ section of the site Application of microcircuits. Article selection

▪ article Sacred Stones of Europe. Popular expression

▪ article What animals, except for the cuckoo, are engaged in nest parasitism? Detailed answer

▪ article Wagonmaker. Job description

▪ article Artificial fruit essences. Simple recipes and tips

▪ Article Lord of the Snake. 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