The presented radio bug with its own hands can transmit sound over a distance of up to 500 meters. You can also use it to make an FM tuner and transmit a signal from your phone to the radio.

Radio transmitter for KT368

DIY radio transmitter for KT368

In this article I want to talk about a radio transmitter using a single transistor.

It can be used both for wiretapping, and you can also use it to make a repeater, replacing the microphone with an audio signal input.

DIY radio transmitter on MC2833

Using the MC2833 chip you can make a fairly high-quality FM transmitter. This chip contains an oscillator, an RF amplifier, an audio amplifier and a modulator. Available in a miniature plastic housing with end leads for surface mounting and a standard housing.

DIY FM transmitter for 1 km and above

DIY FM transmitter for 1 km

This is a fairly powerful 2 W FM transmitter that will provide up to 10 km of range, naturally with a well-tuned full antenna and in good weather conditions, without interference. The scheme was found in the burzhunet and seemed interesting and original enough to be presented to your consideration))

DIY stereo radio transmitter circuit

DIY stereo radio transmitter

In a car, when it is not possible to turn on music from other sources like the radio, and at the same time you want to listen not only to what the radio presenters provide, but to your own music, as an option you can use the one made DIY FM stereo transmitter .

The radio transmitter is assembled in a standard plastic case from some device. The front panel has an audio jack input and a setup button. There is a power connector on the back surface. The filter output is connected to the +12V terminal, so the power cable is used as an antenna. The PCB is secured with only one screw inside the box.

Audio transmitter

DIY audio transmitter (music transmitter)

In this article I want to introduce music transmitter. I tried to assemble a radio transmitter using a varicap in the modulator. Since it was needed to transmit an audio signal and not a conversation, I installed a plug instead of a microphone. Coil of 9 turns of wire with a diameter of 1 mm, the middle tap is sealed. I pushed a small piece of foam rubber inside the coil and dripped it with paraffin (a candle) so that the coil would not bend when touched, because the frequency depends on this, and it is very easy to knock it down.

DIY stereo transmitter circuit diagram

Radio stereo audio transmitter circuit

For stereo transmitters there is specialized chip, BA1404.ABOUTfeature transmitter on BA1404 is high sound quality and improved stereo sound separation. This is achieved by using a 38 kHz crystal oscillator, which provides the pilot tone frequency for the stereo encoder.

A stereo transmitter can be used both at home and in a car to transmit sound from a storage device (phone, player, etc.), since it does not transmit stereo sound.

Such a small stereo transmitter will be a good replacement for an FM tuner.

DIY FM transmitter

FM radio transmitter

Do-it-yourself VHF-FM radio transmitter, operates in the non-traditional range of 175-190 MHz. This radio microphone is easy to assemble. In order to increase the frequency stability of the master oscillator, the base circuit of the power amplifier transistor is powered from a voltage stabilizer (R5, LED1).

Used SMD RED Light-emitting diode. The frequency shift when the power supply drops from 3 to 2.2 volts is no more than 100 KHz. When you touch the antenna with your hand, the frequency also deviates slightly. If you have a receiver with a good AFC, it tracks this change and the frequency shift does not occur at all during the operation of the transmitter.

Do-it-yourself powerful radio transmitter for 500 meters

DIY radio microphone for 500 meters

I want to present the design enough powerful radio bug, Range which amounts to 500 meters with line of sight. The device was assembled almost a year ago for my own needs. Beetle showed amazing results: The frequency hardly fluctuates (every 100 meters by only 0.1-0.3 MHz). The device does not respond to touches of the antenna and other parts (except for the circuit and the frequency-setting circuit) - this is a very important point, since almost all circuits from the Internet have such a problem.

In the practice of creating radio bugs, we often encounter the problem of the minimum possible size of a bug. Today we will talk about just such a bug: NEMESIS-2, as it was named. Nemesis was assembled on SMD components, due to which it became possible in a significant way downsize bug several times, the radio bug is so small that it will fit, for example, in one cigarette, lighter or mobile phone. A little about the parameters: frequency range within 88-108 megahertz, microphone sensitivity about 5 meters, in a quiet room you can hear the ticking of the wall clock. So this signal is easy to receive from this bug to the radio receiver, whether it’s on a phone or just a landline one. Let’s move on to the diagram and details.

This circuit of a shortwave radio station contains only three transistors. The simplest walkie talkie for beginner radio amateurs. The design was taken from an old magazine, but it has not lost a bit of its relevance. The only thing that is outdated is the radio components, which need to be replaced with modern analogues, as a result the characteristics of the radio intercom will improve.

Radio station diagram

The scheme is simple, especially if you understand its operation. I suggest you immediately visually divide it into the left side with one transistor and the right side with two transistors. The transistor VT1 assembles a transmitter and a receiver at the same time. When the switch closes contacts “1”, the radio is in receive mode and this transistor operates in supergenerative detector mode. And when the contacts close to mode “2”, this is transmission and the transistor works as a master oscillator. With this, I think it’s clear. A simple low-frequency amplifier is assembled on transistor VT2, VT3, which, depending on the position of the switch, either amplifies the signal from the microphone and transmits it to the transmitter, or amplifies the signal from the supergenerative detector and transmits it to the loudspeaker. By the way, the loudspeaker and microphone are one and the same element - a high-impedance DEM telephone capsule.

Radio parts

Coil L1 is wound on a frame with a diameter of 8 mm with a ferrite core turn to turn and has 9 turns of PEL wire with a diameter of 0.5 mm. Coil L2 is wound on top of 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. The primary winding of the output transformer of the transistor receiver can be used as inductor L4.

Antenna design

The antenna was made by me from thick aluminum wire, with a piece of insulation, on top of which the L3 coil was wound.

My modernization

I made such a walkie-talkie back in school, but then I already changed all the transistors to more modern ones with a high gain. For example, I replaced VT1, VT2 with KT361, and VT3 with KT315.
Now, of course, I would change the polarity of the power supply and the polarity of the capacitors, replace all the transistors from the n-p-n structure to p-n-p, and p-n-p to n-p-n. Well, I would install modern transistors. There are no particular requirements for transistors, so absolutely any will do.
The author of the diagram says that the range of action of radiums of the same type in open areas is 100-200 meters. I accelerated such radios to 500 meters, for this I used modern transistors, increased the antenna to 900 mm, plus increased the generator current by replacing the 100 Ohm resistor with a 50 Ohm one. Someone will say that it’s all due to the increase in the antenna, with which I disagree and will say that with the “native” antenna I was able to communicate over 300 meters.

Settings

If you assembled the radio correctly and from serviceable parts, then the entire setup will come down to setting the L1 coil to a frequency of 27 MHz. This can be done with a subline core or a capacitor in the circuit.

Walkie-talkies are widely used in different areas of life. So, they can serve as a baby monitor in cases where there is not enough money for a special device for communicating with a child.

You can use a walkie-talkie for security guards or tourism enthusiasts to communicate with companions, but it is not at all necessary to set aside a tidy sum to purchase this equipment, because you can create a walkie-talkie with your own hands at home. Apart from getting the final product, it is a very interesting and fun activity.

So, what do you need to make a walkie-talkie?

To create a walkie-talkie you will need the following items:

4 MP-42 transistors and 3 P416B transistors;
Resistors. You will need a lot of them: two pieces each. 3K, 160K, 4.7K, one each – 22K, 36K, 100K, 120K, 270K, and six pcs. 6.8 K;
Capacitors: two 10 MK 10 V, 3300, 1000, 100, 6, 5-20, 22, 10 and one 5 MK 10 V – 4; 0, 0, 47 MK.
Telescopic antenna;
Microphones and speakers;
PCB boards - 2 pcs.
Soldering iron;
Socket;
Wire cutters.

Almost all of the above is included in the special kit for radio amateurs JC986A. The further algorithm will be based on this set.

It is worth considering that creating your own walkie-talkie requires skills in working with a soldering iron and knowledge of how to determine the values of the elements.

Algorithm for creating a 50 MHz walkie-talkie

If you purchased a ready-made kit for creating a walkie-talkie with your own hands, you will need the following diagram. The names of the elements must be indicated on your board and diagram attached to the device for making a simple walkie-talkie.

First, start installing resistors and forming the electrodes of this element. Using a soldering iron, the resistor must be soldered to the board, and the protruding electrodes must be cut off with wire cutters. Carefully and carefully install all components, relying on the drawn outline on the board.

Start soldering the extension coil L 1, and then the capacitors. The next step is to solder the electrolytic capacitors. Since they have a certain polarity, it is necessary to properly fit the negative electrode into the board.

Using a soldering iron, attach the contour coil T 1 and the body of the switching element S 1. Proceed to soldering the transistors, relying on the contour drawn on the board. You need to solder the cut parts of the electrodes remaining from step 1 to the board. Do this so that jumpers J 1 are formed.

Now you can check the quality of the work performed. If necessary, wipe the board with an alcohol solution, and later install the on/off button. Attach the finished board to the case using self-tapping screws.

Now you can install one of the main elements of the walkie-talkie - the antenna. On top of it there should be a small plastic cap, on the other side you need to solder a conductor that will connect the antenna to the board. Using the remaining pieces from the conductors, attach the S 2 switch to the board and check its functionality.

Place the terminals in the battery compartment. Now you need to solder the conductors responsible for the speaker and power supply system. If you have no doubt that you did everything correctly, connect a battery to the mechanism and check it. The finished device should make a hissing sound.

Assemble the second radio in the same way as the first. To ensure that the devices operate with the same cleanliness, remove one board from the fastener. We hope that these detailed instructions for creating a walkie-talkie with your own hands helped you understand the creation of this mechanism.

Debugging a homemade walkie-talkie

Even if you carefully followed the specified algorithm, the equipment may not work properly. In order to get the mechanism working, use a variable resistor and wait until the radio hiss is at its maximum volume.

Using a tuning core, change the inductance level until the signal is correct. After this, do not forget to return the original resistor and adjust its resistance.

If your voice emitted by the second walkie-talkie is severely distorted, select other resistors and start creating a wave meter, the diagram of which you can find on the Internet along with photos of homemade walkie-talkies. By the way, you need to check the quality of communication at a distance of 5, then 10 and 20 meters; it is better to do this in an open space.

We have described a step-by-step algorithm on how to make a walkie-talkie with your own hands. It should help you create your own mechanism to ensure communication with family or friends during a hike, tourism, fishing or contact with a child.

Remember to take precautions when operating this equipment to avoid the risk of injury such as burns or electric shock.

Photos of walkie-talkies with your own hands

You will need

Transistor P416
Variable resistor 47 kOhm
Resistor 10 kOhm
2 capacitors 0.022 mF
Capacitor 0.033 mF
Capacitor 4700 pF
Capacitor 100 pF
33 pF capacitor
51 pF capacitor
2 tuning capacitors 4-15 pF
Throttle (L2) 20-60 µG
Carbon microphone
High impedance phones (headphones)
Telescopic antenna
40 cm of copper wire with a cross section of 0.5 mm
9-12 V battery
Switch (SA1) - 2 positions for 2 groups of contacts (double toggle switch possible)
A piece of getinax or textolite for the mounting panel
Mounting wire
Power switch (not shown in diagram)
Toy radio transmitter
Tools
Soldering iron
Wire cutters
Pliers
Tweezers
Drill
Drill

Instructions

Assemble the parts according to the diagram. Set coil L1 to the range 27-30 MHz. Its winding data is as follows: 11 turns of a 0.5 mm drive are wound on a blank with a diameter of 10 mm. Accurate adjustment to the range is carried out by trimming capacitors C1 (receive mode) and C2 (mode), taking into account that in the circuit SA1 is in receive mode. Adjustment based on a control receiver (for example, a factory-made children's radio). The easiest way to do this is in transfer mode. Having switched the switch to receive mode, achieve a loud hiss in the headphones by adjusting the transistor mode with a variable resistor.

Without touching coil L1, use tuning capacitor C1 to achieve stable reception of the signal from the control transmitter (the same children's radio intercom). If you are making a walkie-talkie to replace a damaged one, configure it according to the existing one.

The design of the housing can be anything, it depends on the dimensions of the parts. If the housing is metal, then the antenna must be protected from contact with the housing by a reliable insulator. Plexiglas can be used as an insulator.

note

Part numbers are indicated on the diagram

It is advisable to collect 2 similar radios at once.

Sometimes, for reliable operation of a radio station, it is necessary to select a transistor by replacing it.

Helpful advice

Instead of a telescopic antenna, you can use a piece of rigid copper wire or copper tubing. The length of the wire or tube is 0.5 m.

The radio is mounted on a board made of dielectric material. It can be either printed or mounted. It is possible to use volumetric installation.

The radio is configured with the antenna connected and fully extended. During setup and operation of the radio, do not touch the antenna with your hands.

The circuit uses a high-frequency p-n-p transistor, but it can be replaced with any other low-power high-frequency transistor, including n-p-n structures, for example KT315. In this case, it is necessary to reverse the polarity of the power supply.

Having looked through many topics, I saw methods for assembling various receivers, including detector ones.
But what if after a power supply or in another extreme situation you need to send a signal, for example for help, or something else. But that’s not the point. This method has been tested by me, because I assembled it and everything works.
Making a simple walkie-talkie with your own hands is much more difficult than buying a ready-made version in a store, but still.
Here are all the materials that will be needed to assemble a homemade walkie-talkie, the signal radius of which is approximately 1.5 km:
3 transistors P416B, 4 transistors MP42

Resistors for 3K, 160K and 4.7K 2 pieces each, 22K, 36K, 100K, 120K and 270K 1 piece each and as many as 6 resistors of the 6.8K type

Capacitors type 10MK*10V, 3300, 1000, 100, 6, 5-20 2 pieces each, 22, 10 and 0.047MK 1 piece each and as many as 4 capacitors type 5MK*10V
and

Antenna, microphone, speaker, switch, switch, DC source, 2 PCB boards, connecting wires and wire with a diameter of 0.5 and 0.1 mm;
multiplied by the number of homemade walkie-talkies that you are going to make with your own hands.

Diagram of a simple homemade walkie-talkie:

Where, A1 is one common antenna for sending and receiving a signal, SA1 is a power switch, and switch SA2 will connect a homemade radio station to a current source: while sending a signal to the transmitter, and accordingly to the receiver while receiving.

The following figure clearly shows the winding diagram of the coils, the basis for which will be plexiglass, polystyrene or, in extreme cases, cardboard cylinders with a diameter of 0.8 cm and a height of 2 cm, and as a winding - 1 layer of copper wire with a diameter of 0.5 mm, laid in what is called turn to turn . Coils L5 and L1 of your simple homemade walkie-talkie with your own hands should have ten turns each, coil L2 should consist of four turns and is located between the halves of winding L3, consisting of eight turns and having a wire tap in the middle. For those who don’t understand simple radio circuits with their own hands, coils L3 and L2 are wound on the same base.

L4 and L6 are a 200-turn winding of 0.1 mm wire around a housing of MLT-0.5 type resistors with a minimum resistance of 1 MOhm.

If you have read to these lines, then you probably understand at least something about electrical engineering, and therefore place the parts on textolite boards (one of them will be with a master oscillator, and the other with a low-frequency amplifier and receiver) on one side and connect them on on the other side with an insulated wire with a diameter of 0.2-0.3 mm, it should not be difficult for you, as well as connecting the batteries using a stranded wire insulated with vinyl chloride. You can make a printed circuit if you have a foil getinax, and the frame of your simple homemade walkie-talkie can be done with centimeter-long scraps of copper wire driven into holes one millimeter in diameter.

It remains to make sure that the windings of the chokes and coils are mutually perpendicular, the handle of the capacitor C15 is located on the front panel of the radio station, and the master oscillator is separated from other parts of your simple homemade walkie-talkie with your own hands by a tin screen, which in turn is connected to the “+” power supply.

The absence of a microphone can be successfully corrected by having a pair of high-impedance headphones, and instead of a telescopic antenna from a radio, you can use a meter-long brass tube with a diameter of 0.5 cm.

Setting up and debugging a homemade walkie-talkie

Even if you regularly attended all the classes of the circle of young radio amateurs, it is not a fact that your simple do-it-yourself walkie-talkie will immediately work as it should.

Debugging a homemade walkie-talkie begins with improving the quality of signal reception, for which replace R10 with a variable resistor of 33-47 kOhm and wait until the noise becomes as loud as possible. Now change the level of inductance L5 with a tuning core, achieving better signal quality, and finally change the variable resistor back to a constant one with the desired resistance.

If the timbre of your voice is greatly distorted when transmitting a signal, select resistors R1 and R3 more carefully, and to debug the generator and antenna, assemble a wave meter, the electronic circuit of which is shown below. The basis for a coil L of ten turns of 1.2 mm wire will be a frame with a diameter of 2.2 cm, where the third turn from the bottom is a tap. Capacitor C1 needs to be made tuning, with an air dielectric, and its handle should be placed opposite the current frequency of the signal transmitter of your homemade walkie-talkie, making sure that its coil L3 is located next to the L coil of the wave meter, thereby making it a kind of indicator. Now, instead of C9, trying capacitors of different capacities, you need to achieve the maximum deviation of the needle on the wavemeter division scale, and, bringing the latter directly to the antenna itself and rotating the tuning core L1, adjust the antenna to the resonance frequency of the circuit L3C8C9 until the needle on the wavemeter scale shows the maximum deviation.