Simple radio on three transistors

This is a shortwave radio station contains only three transistors. The simplest walkie-talkie for recurring beginners. The design was taken from an old magazine, but its relevance is not a bit lost. The only thing that is out of date is the radio components, which need to be replaced by modern analogues, as a result, the characteristics of the radio intercom device will improve.

Radio station layout


Simple radio on three transistors

The scheme is simple, especially if you understand its work. I suggest you immediately visually divide it to the left with one transistor and the right with two transistors. On the transistor VT1, the transmitter and receiver are assembled simultaneously. When the switch closes the contacts "1", the radio is in receive mode and this transistor operates in the supergenerative detector mode. And when the contacts are closed in the “2” mode, this is the transmission and the transistor works as a master oscillator. With this, I think it is understandable.A simple low-frequency amplifier is assembled on the transistor VT2, VT3, which, depending on the switch position, either amplifies the signal from the microphone and transmits it to the transmitter, or amplifies the signal of the super-generator detector and transmits it to the loudspeaker. By the way, loudspeaker and microphone is one and the same element - high-resistance phone capsule DEM.

Details for the radio station


The coil L1 is wound on a frame with a diameter of 8 mm with a ferrite core turn to the turn and has 9 turns of a PEL wire with a diameter of 0.5 mm. The coil L2 is wound over the coil L1 and has 3 turns of the same wire. Coil L3 has a diameter of 5 mm and contains 60 turns of PEL wire with a diameter of 0.5 mm. As the choke L4, you can use the primary winding of the output transformer of the transistor receiver.

Antenna design


Simple radio on three transistors

The antenna is made of thick aluminum wire, with a piece of insulation, over which the coil L3 is wound.

My modernization


I did this radio in school, but then I changed all the transistors to more modern and with a high gain. For example, I replaced VT1, VT2 with KT361, and VT3 with KT315.
Now, I would certainly change the polarity of the power supply and the polarity of the capacitors, replaced all the transistors from the structure of n-p-n to p-n-p, and p-n-p to n-p-n. Well, I would install modern transistors.There are no special requirements for transistors, so absolutely any will do.
The author of the scheme says that the radius of action of radium of the same type in open areas is 100-200 meters. I also overclocked such radios to 500 meters, for this I used modern transistors, I increased the antenna to 900 mm, plus I increased the generator current, replacing the 100 Ohm resistor with 50 Ohm. Someone will say that all because of the increase in the antenna, with which I do not agree, and I will say that with the "native" antenna I was able to connect to 300 meters.

Customize


If you have assembled the radio correctly and from intact parts, then the entire setup will be reduced to tuning the coil L1 to a frequency of 27 MHz. You can do this subscript core, or a capacitor in the circuit.

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