The article will talk about how to make a radio with your own hands. Simple radio receivers cannot pick up stations in the FM band. And in order to make a radio receiver that allows you to receive signals in the FM band, you need to use a large number of transistors or a microcircuit. But the simplest radio receivers that allow you to receive signals from distant stations operate in the AM band. In the article we will talk about the latter.
Radio Basics
This design is very simple, even a first grader can repeat it. The principle of operation of the device is quite simple, any diagram shows all the elements that are found in the design. When making such a radio with your own hands, you need to remember how the signal of the radio station is formed.
There are two types of signals that any radio station emits when operating on the AM band:
- Carrier - a certain frequency is set by the generator. This creates a kind of background.
- Modulation is a signal created by music, voice,any sounds.
These two signals overlap. And as a result, the listener, when tuned to the frequency of the station, can perceive the information that is being transmitted without unnecessary interference.
Antenna and grounding
For the normal operation of the detector receiver, you need a good antenna. A piece of wire or a telescopic design will not work, you don’t even have to try to connect it, you won’t achieve any effect. It will be required at a height of 3-5 meters above ground level to pull the wire at least 5 meters in length. From it you make a tap to the installation site of the radio receiver with a similar wire. The main condition is that this wire should not have electrical contact with structural elements of the building, with trees, poles. If you need to fix it, use special insulators.
Directly, the antenna web must be isolated from suspension points. You can mount the antenna on a house, outbuildings, trees or poles. It does not matter, the main thing - do not forget to isolate the canvas. Otherwise, the signal will simply start to go to the ground. As you can see, making a radio with your own hands at home is not difficult, but preparing everything for it to work is a lot of work. After all, you still need to do grounding. Of course, you do not need to do it according to all the rules of electrical work. It is enough to drive a metal pin about 1 meter long into the ground. But if there are metal water pipes nearby, you can use them as a ground.
Headphones orheadphones?
This design has earned popularity among beginner radio amateurs for a reason. It contains a minimum number of elements, but allows you to receive signals from powerful stations. Unfortunately, only on high-impedance headphones. Headphones with a 3.5 mm plug, which are used for computer equipment or telephones, are not suitable - you will not be able to listen to the signal. It is necessary to use headphones like TON-2. They have a winding resistance of about 1600 ohms.
But one feature should be noted - if there are computer speakers with an amplifier, they can be connected to the output of the receiver. Then you won't have to look for TON-2 headsets that have already become in short supply.
Receiver circuit
On the diagram you can see all the elements that are used in the design of the receiver:
- Inductor.
- Variable capacitor.
- Semiconductor diode.
- Permanent capacitor.
- Headphones.
The top of the circuit is connected to the antenna, the bottom to ground. Instead of a variable capacitor, you can use a trimmer, it has a slightly smaller size. And as practice shows, the choice of this element does not affect the work much.
Inductor
To make such a radio craft with your own hands, you will have to wind the inductor. The procedure is simple, you will need the following materials and tools:
- Cylindrical frame. Diameter 3-5 cm, height not less than 10 cm.
- Copper wire in lacquer insulation - diameter 0.5-1 mm. The thicker it is, the better.
- Alligator clips.
- Screwdriver and drills.
- Varnish for fixing the winding.
At the edges of the frame you need to make holes in which you fix the ends of the winding. Then tightly, coil to coil, lay the wire on the frame. To increase the range of received signals, you need to make taps from every 15th turn (not critical, you can tap from the 20th or 25th turn). In total, you will have to wind 100-150 turns in this way.
Fix the edge of the winding, clean and solder all the taps. By the way, to facilitate switching, you can install a multi-contact switch. But you can also use the crocodile clip, which is connected to the top output of the variable capacitor according to the circuit. The coil is done, now you can start assembling the structure.
Begin assembly
To make a simple radio with your own hands, it is enough to have basic skills. Soldering iron can not be used. But if you use it, then the installation of the structure will look better hinged. The largest element is the variable capacitor. Moreover, it is necessary to use those in which air acts as a dielectric. Modern film capacitors are not suitable for use in the construction of a detector receiver.
Choose the right case for the design. Due to the fact that the coil has large dimensions, the housing willcorresponding. But you can reduce the size of the coil, for this you will have to increase its inductance. This can be done very simply - wind the wire not on a thick frame, but on a ferrite core. Then the whole structure can fit in a small case, on which it is necessary to install jacks for connecting headphones, grounding and antenna.
Connecting elements and launching
And now let's look at the design in more detail and detail. It is not difficult to make a radio with your own hands, the main thing is to clearly follow the connection diagram of the elements.
Let's see how this is done:
- It is necessary to solder a semiconductor diode to the upper terminal of the variable capacitor according to the scheme. Instead, it is allowed to install a transistor, but only the p-n junction should work. Experienced experts recommend using silicon diodes such as D9B or KD350.
- Solder a constant capacitor to the second terminal of the diode. It is necessary to choose non-polar and with a large capacity (from 3300 pF). Be sure to pay attention to what material the element is made of. Better if it is a paper capacitor.
- Solder the second output of the capacitor to the lower contact of the variable according to the diagram.
- Headphones are connected in parallel with a constant capacitor.
- Connect the antenna to the top output of the inductor according to the diagram.
- Ground connect to bottom terminal.
That's all, if no errors are made, the receiver works without adjustment. He doesn't feedrequires.
Radio upgrade
As you can see, it is not difficult to make such a radio with your own hands, but it has a lot of drawbacks - low sensitivity, large dimensions, and can receive no more than two stations. One of the improvements discussed above was to replace the large coil with a more compact one with a ferrite core. But still there was one problem - sound reproduction. If desired, additional high and low frequency amplifiers can be made for this receiver.
In this case, the selectivity and sensitivity of the device will be significantly improved, and most importantly, you will be able to listen to radio programs through the speaker. By the way, you can assemble the entire structure in a case from computer speakers. In this case, there will be no need to manufacture an additional low-frequency amplifier. But on the other hand, why spoil such a device with a simple detector receiver?
Better assemble a quality FM receiver. For this purpose, you can use literally one chip and no more than 5 elements. It is worth paying attention to the fact that reception in this range is much better, and most importantly, a large number of stations work here.
