Radio circuits: on a chip and the simplest detector

In this paper, we will consider the schemes of radio receivers and analyze the operation of the simplest structures. All of you know that there are several ranges of radio waves. And all of them are divided into broadcasting, for cellular communication, for official use and radio amateurs. Broadcasting of radio stations is carried out in the range of medium (AM, CB), long (DV, 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 each novice radio amateur. And the strength to collect it even to a child, because there is nothing complicated in it. For manufacturing you need to acquire the following elements:

1. Variable capacitor.
2. Constant capacitor with a capacity of more than 4700 pF.
3. Headphones with a winding resistance of more than 1500 ohms. Perfectly fit TON-2.
4. A semiconductor silicon diode of type D9. However, any more modern high-frequency one is suitable.
5. Copper wire and mandrel diameter of at least 40 mm.

The above schematic diagram of the radio receiver allows us to understand how the connection of all elements is carried out. Particular attention should be paid to the design of the antenna, grounding, coil inductance. About these elements need to talk separately. The detector radio receiver can work in the range of medium and long waves, so its operation requires a full antenna.

Antenna, ground and coil design

In order for the radio circuits described in the article to work in the range of SV, DV, KV, it is necessary to make 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 web is considered based on the frequency at which the radio will operate. The length of the web should be a multiple of the frequency expressed in meters. If we are talking about 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.

Heating pipes can be used as ground. But the ideal option will be a metal pin, driven in at least one meter into the ground. The coil is wound only with copper wire. Moreover, it should be a thickness of more than 0.75 mm, to expand the possibilities, one can make bends. The coil is wound on a strong mandrel, the ends are securely fixed. Please note that you need at least 90 turns to wind, so pick up the mandrel as long as possible. These schemes of radio receivers are good only in that they can understand the principle of operation of such devices. But its sensitivity is extremely low, therefore with its help it is possible to listen only to powerful radio stations. Even connection to an external amplifier will not save the LF.

Radio on chip

Above is a diagram of the radio receiver on the K174XA34 chip. In this small element, several nodes are assembled - a detector, a frequency converter, a signal amplifier. Of course, this chip is obsolete, but it is still manufactured, and its cost is very low. And what else is needed for a novice radio ham? Even if such an element is spoiled, it's not a pity. There are also foreign analogs, which make it possible to produce radio receivers for the VHF band, and their cost is also not very large. 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 disadvantage is that it will be necessary to make an additional low-frequency amplifier , since the output of the chip is a very weak signal.

Conclusion

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 that will be useful during outdoor recreation, for construction work, and for driving. For example, to perform an automatic start. In other words, the radios are so functional that they are used today everywhere.