In this article, radio receiver circuits will be considered, the analysis of the operation of the simplest structures will be conducted. You all know that there are several ranges of radio waves. And they are all divided into broadcasting, for cellular communications, for official use and amateur radio. Broadcasting of radio stations is made in the range of medium (AM, CB), long (LW, LW), ultrashort (VHF, FM) waves. And now you will learn how to make the simplest devices for receiving radio stations.
Detector radio
This design is made by every novice radio amateur. And even a child is able to collect it, since there is nothing complicated in it. For the manufacture you will need to acquire the following elements:
- Variable capacitor.
- Permanent capacitor with capacitance over 4700 pF.
- Headphones with a winding resistance of more than 1,500 ohms. Perfectly suitable TON-2.
- Semiconductor silicon diode type D9. However, any more modern high-frequency will do.
- Copper wire and mandrel with a diameter of at least 40 mm.
The above schematic diagram of the radio allows you to understand how to connect all the elements. Particular attention should be paid to the design of the antenna, grounding, inductor. You need to talk about these elements separately. The detector radio can operate in the medium and long wavelength range, therefore, for its functioning, a full-fledged antenna is needed.
Antenna, Ground, and Coil Design
In order for the radio circuits described in the article to work in the range of CB, LW, HF, it is necessary to manufacture an antenna. It is made from a piece of wire. You can use stranded insulation, the main thing is that its cross section is more than 0.75 square meters. mm But too thick should not be used. The length of the antenna blade is considered based on the frequency at which the radio will work. The length of the web should be a multiple of the frequency value, expressed in meters. If it is a range of 90 meters (3200 kHz), then the length of the antenna should be at least 10 m. It must be suspended at a height of at least 3 meters and carefully insulated from walls, trees, poles.
As grounding, you can use heating pipes. But the ideal option would be a metal pin, driven at least one meter into the ground. The coil is wound only with copper wire. Moreover, it should be more than 0.75 mm thick; bends can be made to expand capabilities. The coil is wound on a strong mandrel, the ends are securely fixed. Please note that you need to wind at least 90 turns, so select the mandrel as long as possible. These radio circuits are good only in that they can understand the principle of operation of such devices. But its sensitivity is extremely low, so with it you can only listen to powerful radio stations. Even connecting to an external bass amplifier will not save.
Chip Radio
Above is a diagram of a radio receiver on a K174XA34 chip. In this small element, several nodes are assembled - a detector, a frequency converter, a signal amplifier. Of course, this chip is outdated, but it is still being produced, and its cost is very low. And what else is needed for a beginner radio amateur? Even if such an element deteriorates, it is not a pity. There are also foreign analogues that make it possible to manufacture radios for the VHF band, and their cost is also not very large. The above scheme is good in that there are no scarce elements in it, but it allows you to receive radio stations in the broadcast range. One drawback - you will need to additionally manufacture a low-frequency amplifier , since the output of the chip is a very weak signal.
Conclusion
Having a little understanding of the design of radios, you can begin to manufacture more complex devices. The modern element base allows you to independently make not only receivers, amplifiers, but also transmitters, which will be useful during outdoor recreation, for construction work, as well as for driving a car. For example, to implement an automatic start. In other words, radio circuits are so functional that they are used everywhere today.