(the simplest walkie-talkie) is shown in Figure 1.
The radio intercom contains only three transistors. In the receiving mode, a supergenerative detector is implemented on VT1, and in the transmitting mode, the cascade on this serves as a master oscillator, emitting a carrier frequency into the antenna.
On transistors VT2, VT3 in the receiving mode serves as an amplifier of the low-frequency received signal, and in the transmitting mode it switches as an amplifier. DEM capsule, used as a microphone during transmission.
Details
Coil L1 is wound turn to turn on a frame with a diameter of 8 mm with an SCR core and has 9 turns of PEL wire with a diameter of 0.5 mm. Coil L2 is wound on top of it and has 3 turns of the same wire. Its diameter is 5 mm, it contains 60 turns of PEL wire with a diameter of 0.5 mm. The primary winding of the output transformer of a pocket transistor receiver can be used as inductor L4.
The radio is designed for operation in a car, boat or stationary environment. It requires a constant voltage source of 12 - 15 V with at least 1 A. The communication range with a similar radio station is about 2 - 5 km in the city, up to 15 km on the highway and up to 30 km when operating in a stationary mode on a full-size antenna located on mast. The radio station operates with an antenna having a characteristic impedance of 75 ohms.
TECHNICAL CHARACTERISTICS OF CAR SV RADIO STATION
- Operating range................................................... ........................... 27 MHz.
- Transmitter output power at voltage
- Frequency modulation with deviation.................................................... .......2.5 kHz.
- Transmission current consumption, no more................................................... ......0.6 A.
- Receive current consumption, no more................................................... ......0.015 A.
- The sensitivity of the receiver with a signal-to-noise ratio is no worse than................1 µV.
- Selectivity in the adjacent channel at a detuning of ±10 kHz is no worse....... 36 dB.
12V power supply at 75 Ohm load............................................... ....................3 W.
The circuit of a pocket radio station (see Fig. 1) does not contain scarce elements, is easy to configure and simple to build. However, despite its simplicity, it has good characteristics. Receiver sensitivity is no worse than 10 μV, transmitter power is 250 mW, operating frequency is 27.14 MHz, communication radius in open areas is up to 1 km.
The transistorized pocket radio receiver is super-regenerative (VT2) and aperiodic (VT1). A useful signal is released at resistor R5, but it is much smaller with the suppression frequency of the super-regenerator. To suppress unnecessary noise and highlight the useful signal, the C12R7C13L7C14 filter is installed in the receiver. From it, the signal is supplied to resistor R13, which is a volume control, and then to audio frequency, made on transistors VT8, VT10, VT11.]
The transmitter of the pocket radio station is assembled on five transistors VT3-VT7 and is a push-pull self-oscillator, the signal of which is fed to the antenna through the coupling coil L2 and the matching circuit L1C3. Parallel connection of VT3, VT6 and VT4, VT7 allows you to increase the power transmitted to the transmitter antenna.
The use of portable radio microphones is usually associated with power supply problems, due to the need to regularly recharge batteries or change batteries. At the same time, autonomous power supply is not always necessary. The proposed radio microphone is designed to be powered by a voltage of 220 V, but differs from conventional circuits containing a network transformer or a quenching capacitor. Due to the low current consumption, it was possible to use quenching resistors, which have significantly smaller dimensions. The principle of a “network” radio microphone is shown in the figure below:
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The full-wave rectifier is assembled using diodes VD2 and VD3, voltage is supplied to it through quenching resistors R4, R5, and VD1 (about 8 V) is stabilized from the output of the rectifier.
Thanks to cascode connection
However, the forum received fair comments and requests for a more detailed explanation of the operation and drawings of the circuit. Therefore, after delving into the archives, I present additional materials. In those distant 90s, one could only dream of the sPlan program, and indeed of a personal computer in general - on a PC costing 500 bucks you couldn’t really do much with a $5 stipend. So below are pictures of pages from the notebook (those who wish can convert them into a more readable form).
Here the walkie-talkie is divided into two completely independent units - a receiver and a transmitter, both broadcasting in the FM range of 88-108 megahertz. This frequency was not chosen by chance - many have a ready-made FM radio receiver, which makes it possible to simplify the manufacture of a walkie-talkie, making only the transmitting part. In addition, you can listen and speak at once if you separate the frequencies of the receiver and transmitter by 10-20 megahertz.
Naturally, you can and even need to assemble the receiver yourself, using the most common K174XA34 microcircuit or its foreign analogue. The microcircuit is very unpretentious in setting up and starts up almost immediately. See the drawing of the printed circuit board for the receiving part of the radio below.
The transmitter can be made using various schemes: with 3 transistors without frequency stabilization (like a simple FM bug) or with a quartz resonator. The second option is more difficult to set up, but also better.
The figure shows that the microphone amplifier is a UD1208 op-amp. Next, the signal goes to the modulator (varicap and quartz), the quartz frequency is several times lower than the FM and the output transistor selects the desired harmonic.
Initially, the output stage circuit included a KT610 transistor, but after it burned out and there was no similar one, I installed a microwave transistor from a television to replace it - it worked even better (only the hole remained). Photos of circuits and boards are not of high quality. For a more detailed study, download the archive.
Installation of the entire transceiver unit on a fiberglass board. The receiver and the radio transmitter are assembled as a separate unit.
By the way, you may ask: Why not use a regular mobile phone as a walkie-talkie? Firstly, harmful radiation (2 GHz half a watt, versus 0.1 GHz 0.05 watts). Secondly, the power supply - a mobile battery will not last long, but here, using good banks, you can talk continuously for at least a day. And finally, mobile cellular stations are not available everywhere.
How to make a radio body. There are a lot of options, but it is best to bend it from sheet aluminum or use a ready-made shielded box. Especially if you do not have a quartz transmitter. Paint the outside of the body or cover it with self-adhesive tape.
The photo shows an option with two regulators - one is responsible for the volume, and the other is for setting the receiver frequency. After all, ours is not quartz-coated, so a little maintenance is possible in case of shocks or vibrations. On the other hand, it’s even better - you’ll listen to music on it :)
You can power your homemade walkie-talkie from anything. Voltage is 5-12 V. Naturally, with less power, the range will be shorter, although performance remains the same at 5 V.
In order to save space and current consumption, the speaker can be replaced with security-type headphones. Or provide a socket for connecting them, with automatic switching off of the loudspeaker. In general, the result is a good, personally tested design of an FM radio, which can be repeated even by not very experienced radio amateurs.
Even though in our age of portable gadgets, walkie-talkies are not so relevant, it is still sometimes interesting, and sometimes necessary, to use them. Here we will look at how to make the simplest models of these devices, as well as related issues related to them.
Homemade walkie-talkie: materials
Before you make a walkie-talkie with your own hands, prepare the simple components necessary for it:
- Two aluminum/tin cans, and paper cups as a last resort.
- Fishing line, thread 5-10 m long.
- Nail.
- Hammer.
Now you can get to work.
Making a walkie-talkie with your own hands
Let's take a closer look at how to make a walkie-talkie at home:
- Using a hammer and nail, poke holes in the bottom of each jar and cup. The hole should be large enough for the fishing line to pass through.
- Pass the line through both holes. Tie it inside the cans or cups with a voluminous knot so that it cannot be pulled out or pulled out.
- In order for your interlocutor to hear your voice, the fishing line must be as stretched as possible - after all, sound waves will pass through it.
- A conversation on this improvised walkie-talkie looks like this: one person speaks into a cup, and the other holds his jar near his ear.
Application "Zello-walkie-talkie"
The most convenient and easiest way to experience the beauty of talking on a walkie-talkie is to install an application with this function on your smartphone. The leader among them is Zello, which can also be installed on a laptop or PC. The program is completely free for all existing operating systems. Zello is often used by mobile software developers - it allows them to add the function of communicating via walkie-talkie to their applications.
Zello uses Wi-Fi or mobile Internet to transmit voice. The application also supports Bluetooth headset. Your voice message is first saved by the system and then sent to the recipient. Zello supports communication between 800 interlocutors, displays their connection status, stores voice message histories, and creates special password-protected channels.
Voxer walkie-talkie
Another way to answer the question “How to make a walkie-talkie from a smartphone?” is a Voxer application, absolutely free for iPhone and Android owners. Transferring data via mobile Internet or Wi-Fi will also not bring you additional waste. The application can be called a walkie-talkie conditionally - it does not provide the ability to talk in real time, but quickly sends voice messages from user to user.
Some of the features of this walkie talkie app include the following:
- The ability to record a voice message and save it inside the program at times when the gadget is not connected to the Internet.
- Reproduction of the interlocutor's voice in two or three times acceleration.
- Storing the history of voice messages.
- The ability to indicate your location to your interlocutors.
- In addition to the walkie-talkie mode, this application can be used as a convenient messenger - through it you can send text messages, video, audio or photos.
A similar app to Voxer would be HeyTell. It is also absolutely free and works in all data transfer modes. It is distinguished by more flexible settings and the presence of three privacy categories for your conversations.
iPTT - walkie-talkie for iOS
Even a small child can figure out how to make a walkie-talkie on an iPhone or iPad using this application - it’s so easy to use. By the way, iPTT is the first application of its kind in the AppStore, and it’s completely free.
Using this program, you can create a direct communication channel with both an individual recipient and a group of people. You can also select the "whisper" mode - confidentially communicate with one person from the group.
An application similar in functionality to iPTT will be TiKL Touch Talk Walkie Talkie. It is available for free not only for gadgets on iOS, but also on Android.
How to make an antenna for a walkie-talkie
If you are the owner of a walkie-talkie, then it will be no secret to you that homemade antennas for these devices are more effective than factory ones. The size of the homemade product, by the way, can be set within 9-25 cm. You will need:
- connector suitable for your walkie-talkie;
- a piece of any thick cable (only insulation is needed from it);
- PEV wire 0.25-0.7 mm;
- heat shrink;
- glue.
The manufacturing process looks like this:
- Pull all contents out of the cable without damaging the outer tube of insulating material.
- At this stage, check how well this tube fits into the connector - ideally it should fit into it.
- On the tube, 4-5 mm away from the level of the connector, you need to make a hole for the wire, where the latter should be placed - inside the pipe.
- Solder the central pin of the connector to the end of the wire, and then glue the tube into the last one.
- The PEV wire protruding from the tube should be wound in equal turns from the connector outward. The winding length is 10-25 cm. The thicker the cable, the longer the winding.
- Secure the skeins with glue to prevent them from unwinding.
- Test the device - trim the winding if necessary.
How to make a walkie-talkie effect
If you need to convert any voice recording into something like a walkie-talkie conversation, you can do the following:
- Use the Adobe Audition program and the Wave4 plugin. The Old Radio effect will help you achieve what you want.
- In the same Adobe Audition 3.0, follow the path Effects - Filter and EQ - FFT Filter. Next is the preset Telephone - Receiver or Telephone - Voice Mail.
- AudioEase Speakerphone plugin, which, in addition to a walkie-talkie, allows you to apply the effect of a loudspeaker, megaphone, poor telephone connection, etc.
- Through presets of the FabFilter - Saturn program.
How to make a walkie-talkie at home and on your smartphone? The process is quite simple and fun. Moreover, today many instant messengers for phones and PCs provide users with the ability to voice and video communicate in real time over the Internet. However, in the absence of mobile and landline communications in the area, portable radios remain indispensable.
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
- Drills
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 the fact that in the circuit SA1 is in receive mode. Adjustment by 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.
Please 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.
Useful 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.
Are you tired of paying for mobile communications all the time? Do you want to upgrade to a free plan? Or do you want to have constant, free communication with your boys in the area? Then this walkie-talkie circuit, which you can assemble with your own hands, is for you.
To make one radio you need:
- Transistors: P416B (3pcs) and MP42 (4pcs);
- Resistors: 3K (2 pieces), 160K (2 pieces), 4.7K (2 pieces), 22K, 36K, 100K, 120K, 270K, 6.8K (6 pieces);
- Capacitors: 10MK*10V (2pcs), 3300MK (2pcs), 1000MK (2pcs), 100MK (2pcs), 6MK (2pcs), 5-20MK (2pcs), 22MK, 10MK, 0.047MK, 5MK*10V (4pcs);
- Antenna;
- Microphone, speaker;
- Switch, switch;
- DC source;
- Textolite boards (2 pcs);
- Wires;
- Wire with a diameter of 0.1 mm. and 0.5 mm.
Diagram of a simple homemade walkie-talkie:
How to make a walkie-talkie with your own hands
The common antenna for receiving and sending the signal is A1.
Power switch – SA1.
The switch connecting the homemade radio station with the current source, while sending the signal to the transmitter and receiver upon receipt - SA2.
Number of turns:
Coils L1 and L5 – 10 turns.
Coil L2 has 4 turns and is located between the halves of the winding of coil L3 containing 8 turns and having a wire outlet in the middle.
Coils L4 and L6 – 200 turns, 0.1 mm wire around the MLE-0.5 resistor with min. resistance 1Mohm.
Well, the coils for the radio are ready.
If you still have the desire to make DIY walkie-talkies, then you probably understand at least something in electronics, and that means it won’t be difficult for you to place the parts on two boards (one of which has a master oscillator, and the other with a receiver and a low-frequency amplifier) on one side and connect them with an insulated wire ( diameter 0.2-0.3mm) on the other. Then connect it to the battery using a stranded wire insulated with vinyl chloride.
Printed installation can be done if you have foil getinaks, and for the frame of a homemade walkie-talkie, centimeter-sized pieces of wire driven into holes with a diameter of 1 mm are suitable.
The windings of the coils and chokes should be mutually perpendicular, and the C15 handle should be on the front panel of the radio. The generator must be separated from other parts by a tin screen.
Configuring and debugging the radio
Debugging begins with improving the reception quality; to do this, you need to replace R10 with a variable one with a resistance of 33-47 kOhm and wait for the maximum noise volume. Next, using a tuning core, we change the inductance L5, achieving the highest quality signal. After this, we return the previous resistor.
