|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Alteration of the Len radio station for receiving information from satellites in the 137 MHz band. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Modernization of radio stations At present, it is possible to find at an affordable price a faulty radio station of the "LEN" type, decommissioned, as they used to say, "from the national economy." In most cases, the transmitter boards fail (sometimes even burn out) in them, while the receiver boards remain intact. The difficulty lies in the fact that the receivers used specialized "hybrid" microcircuits, which are currently almost impossible to find. But, if you're lucky, you can find a "LEN" with a working receiver operating at frequencies of 39 ... 46 MHz. The sensitivity of the receiver in a radio station is usually about 0,5 ... 1 μV. By adding a frequency converter board to it, we get ...
In the existing copy of the radio station, the receiver operated at a frequency of 40 MHz. It was necessary to assemble a converter in order to lower the frequency of the input signal to the frequency of receiving "Flax" (converters work in a similar way, converting the signal from "their" FM band to "our" VHF). The main requirement for the converter circuit was simplicity, the absence of scarce parts and ease of setup. After trying out various options for circuits, burning out a bunch of details and sleepless nights, this is what happened: The first transistor is a UHF cascade according to a common base circuit. This part of the circuit is borrowed from the previous circuit (to the details of which there were no analogues). The UHF load is an oscillatory circuit, the signal from which is fed to the input of the mixer. The mixer is assembled on a K174PS1 chip. At present, it is inexpensive, it can be borrowed from any receiver. It operates at frequencies up to 200 MHz (although there were descriptions of converters supposedly capable of operating at frequencies up to 900 MHz). The local oscillator is assembled on two transistors of the KT363A type. They work great at high frequencies, in this circuit they are included according to the symmetrical multivibrator circuit. In the emitter of one of them, the circuit on the coil L2 is included. In the local oscillator circuit, not a trimmer, but a constant capacitor is installed (to increase frequency stability). In principle, a tuning capacitor can also be installed, but it must be with an air dielectric. Frequency adjustment is performed by changing the voltage on the varicap type KV109V. The varicap is connected to the local oscillator circuit through a small capacitor (by selecting the value of this capacitance, you can change the limits for tuning the receive frequency). The generation frequency will depend on the operating frequency of the Flax receiver - for example, if the receiver operates at a frequency of 40 MHz, and the input signal has a frequency of 137 MHz, the local oscillator frequency should be Fg = 137 - 40 = 97 MHz. Of course, you can use another option: 137 + 40 = 177 MHz, but in this case it will be difficult to ensure the required stability of the generator frequency. If desired, you can assemble the local oscillator according to a different scheme (even use a frequency synthesizer). The output of the converter is loaded on the oscillatory circuit, the signal is fed to the board of the "Lna" receiver through a transition capacitor of a small capacitance. The circuit was soldered from the transmitter board - it was the last before the power amplifier, i.e. tuned to the operating frequency of the radio. In the original version, two capacitors were installed in it, they can be replaced with one of the appropriate capacity. When soldering the circuit from the board, care must be taken, since the polystyrene frame of the coil melts very easily. The fragility of the tuning core used in this circuit can also be considered a disadvantage - at the factory, after tuning, it is fixed with mastic, which is not very easy to remove. The frequency converter can be powered from the 9V voltage regulator output located on the transmitter board. In the "author's" copy of the radio station, the transmitter board was dismantled, so I had to install an integral voltage regulator - "KREN"ku.
Machine for thinning flowers in gardens
02.05.2024 Advanced Infrared Microscope
02.05.2024 Air trap for insects
01.05.2024
▪ Smartphone Honor View 10 with artificial intelligence ▪ NXP Opens Design Center in Singapore to Develop W-USB Technology ▪ The doctor who is always with you
▪ section of the site Winged words, phraseological units. Selection of articles ▪ article by George Orwell. Famous aphorisms ▪ article Which European country has been at war with Japan for over a century? Detailed answer ▪ article Modernization of the MMVZ-3115 engine. Personal transport
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page