Transmitter with narrowband frequency modulation 140-150 MHz. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Transmitters
Comments on the article
The radio transmitter, the circuit of which is shown in the figure, operates in the range of 140-150 MHz with narrow-band frequency modulation. Frequency deviation - 3 kHz. The frequency of the master oscillator is stabilized by a quartz resonator. An M1 electret microphone with an MKE-3, Sosna, MEK-1, etc. type amplifier is used as an acoustic transducer. The microphone is powered through an RC filter consisting of a resistor R1 and a capacitor C1. The audio frequency voltage from the output of the microphone M1 through the coupling capacitor C2 is fed to the input of the audio frequency amplifier (the base of the transistor VT1).
The audio frequency amplifier is assembled according to a two-stage circuit with active elements based on transistors VT1 and VT2 of the KT315 type. It amplifies and limits the audio signal to the required amplitude. The operating modes of transistors VT1, VT2 for direct current are set by selecting the resistance of resistor R3. The specified mode is further maintained automatically using feedback between transistors VT1 and VT2.
The amplified and limited audio frequency signal through a low-frequency RC filter, made on resistors K6, K8 and capacitor C4, is fed to the VD1 varicap of the KV109 type. Under the action of an alternating voltage, the capacitance of the varicap VD1 changes, thereby carrying out frequency modulation.
The constant voltage taken from the collector of the transistor VT2 sets the initial bias on the varicap VD1. The master oscillator is made on a transistor VT3 type KT368, KT3101. The DC mode of the transistor VT3 determines the resistor K9 in its base circuit. The ZQ1 quartz resonator is used at a frequency of 47-49 MHz. The circuit in the collector circuit of the transistor VT3 is tuned to the frequency of the third harmonic of the used quartz resonator.
The high-frequency signal enters the antenna through a small capacitor C8. A piece of wire 40-50 cm long is used as an antenna. Coil L1 is wound with a 0,6 mm PEV wire on the body of the tuning capacitor C7 and contains 3-4 turns. The coil leads are soldered to the capacitor leads.
Setting the audio frequency amplifier consists in selecting the resistance of the short circuit resistor so as to obtain a voltage on the collector of the transistor VT2 equal to approximately half the voltage of the power source. The circuit L1, C7 is adjusted to the maximum radiated power by adjusting the capacitor C7.
Author: V.Adrianov
See other articles Section Transmitters.
Read and write useful comments on this article.
<< 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 Artificial skin for diabetes treatment
08.08.2017
Skin grafts made using CRISPR gene-editing technology prevent mice from developing diabetes, and scientists say these properties of artificial skin could also be useful in humans.
In a proof-of-concept study, scientists at the University of Chicago edited neonatal mouse stem cells to control the production of glucagon-like peptide 1 (GLP-1). This hormone stimulates the synthesis of insulin by the pancreas while maintaining the required level of glucose in the blood. The genetically modified skin grafts were then transplanted into mice fed a high-fat diet to induce obesity. These mice reversed insulin resistance and were half the weight of mice without skin grafts.
Obesity is one of the major risk factors that can cause type 2 diabetes with high insulin resistance. According to the head of the study, artificial human skin made from stem cells could be used to treat people with the disease.
Artificial skin has been used to treat burn patients for decades. But as technology has advanced to the point where it is now possible to grow skin in the lab, researchers have turned to finding ways to use it to treat other diseases. The researchers say they now have the ability to explore the use of various modified gene transplants to treat various diseases.
|
Other interesting news:
▪ Tesla will create its own drone
▪ flu breath
▪ The physical theory of superconductivity is called into question
▪ cockroach cure
▪ Men and women see differently
News feed of science and technology, new electronics
Interesting materials of the Free Technical Library:
▪ section of the site Life of remarkable physicists. Article selection
▪ article We are Kalutsky, it will not reach us. Popular expression
▪ article What do tonsils do? Detailed answer
▪ article Japanese wax tree. Legends, cultivation, methods of application
▪ article High voltage transformer. Encyclopedia of radio electronics and electrical engineering
▪ article Starting induction motors. 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