In this article, radio receiver circuits will be considered, an analysis of the operation of the simplest structures will be carried out. All of you know that there are several ranges of radio waves. And all of them are divided into broadcast, for cellular communications, for official use and amateur radio. Broadcasting of radio stations is carried out in the range of medium (AM, MW), 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 beginner radio amateur. And even a child can assemble it, since there is nothing complicated in it. For manufacturing, you will need to acquire the following items:
- Variable capacitor.
- A permanent capacitor over 4700pF.
- Headphones with a winding resistance of more than 1500 ohms. TON-2 is perfect.
- Semiconductor silicon diode type D9. However, any more modern high-frequency will do.
- Copper wire and mandrelwith a minimum diameter of 40 mm.
The above circuit diagram of the radio allows you to understand how the connection of all elements is carried out. Particular attention should be paid to the design of the antenna, grounding, inductor. These elements need to be discussed separately. The detector radio can operate in the medium and long wave range, so a full-fledged antenna is needed for its operation.
Antenna, ground and coil design
In order for the radio receiver circuits given in the article to work in the MW, LW, HF bands, it is necessary to make an antenna. It is made from a piece of wire. You can use stranded in 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 web is calculated based on the frequency at which the radio will operate. The length of the canvas must be a multiple of the frequency value expressed in meters. If we are talking about the range of 90 meters (3200 kHz), then the length of the antenna must be at least 10 m. It must be suspended at a height of at least 3 meters and carefully isolated from walls, trees, poles.
Heating pipes can be used as grounding. 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 the possibilities. The coil is wound on a strong mandrel, the ends are securely fixed. Please note that you need a minimum90 turns to wind, so pick up the mandrel as long as possible. These radio receiver circuits are good only because they can be used to understand the principle of operation of such devices. But its sensitivity is extremely low, so you can only listen to powerful radio stations with it. Even connecting to an external bass amplifier will not save.
Chip radio
Above is a diagram of a radio receiver on a K174XA34 chip. This small element contains several nodes - a detector, a frequency converter, a signal amplifier. Of course, this chip is obsolete, but it is still being produced and its cost is very low. What else does a beginner radio amateur need? Even if such an element deteriorates, it is not a pity. There are also foreign analogues that make it possible to manufacture radio receivers for the VHF band, and their cost is also not very high. The above scheme is good in that it does not have scarce elements, but it allows you to receive radio stations in the broadcast range. One drawback - you will need to additionally make a low-frequency amplifier, since the output of the microcircuit has a very weak signal.
Conclusion
Having a little understanding of the design of radio receivers, you can begin to manufacture more complex devices. The modern element base allows you to independently make not only receivers, amplifiers, but also transmitters that will be useful during outdoor recreation, for construction work, as well as for driving a car. For example, forautomatic start. In other words, radio circuits are so functional that they are used everywhere today.
