• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar

Homemade Circuit Projects

Get free circuit help 24/7

  • +1000 Circuits
  • Hobby Circuits
  • Basic Circuits
  • Learn Arduino
  • Logic IC Pinouts
  • Disclaimer
You are here: Home / Transmitter Circuits / Make a Walkie Talkie Circuit using FM Radio

Make a Walkie Talkie Circuit using FM Radio

Last Updated on February 27, 2020 by Swagatam 32 Comments

In this post we learn how to make a simple homemade walkie talkie circuit using ordinary FM transmitters and FM radios. It's a perfectly tested design by me.

I could talk with my nephew who stays on first floor through a pair of these transmitters with crystal clear transmission.

walkie talkie using FM radio

Overview

In one of my earlier post we comprehensively learned the making of a compact walkie talkie design, however I found that many new hobbyists and school students found the design difficult to adjust and succeed due to its rather complex and the associated strict parameters,

In this post we try to design a walkie talkie using discrete transmitter modules and then tune them to different frequencies such that the units are able transmit and exchange the conversation across both the sides without interfering with their own receive modules.

For the FM transmitters we select the design which was earlier discussed in our wireless speaker circuit, the main reason being its ability to produce high power output, which enables the circuit to transmit the data over much longer distances compared to the other smaller FM transmitters designs.


Want to learn how to build a small transceiver circuit? The following post will walk you through all the details:

Mini Transceiver


High Range Design

As you can see the design is different from the usual single transistor concepts. Here the design incorporates a 3 transistor design along with a center tap antenna coil. This enhances the power output of the transmitter to a great extent, approximately 4 times more than the single transistor version.

With this special patented design you can enjoy communicating with your friends in your multistorey apartment, across the highest number of floors.

The minimum distance this unit can cover is 50 to 100 meters.

The range of a single transistor circuit cannot be over 30 meters. Check it yourself!

The main objective here is to get a reasonable distance of wireless communication facility.

Circuit Diagram

How the Transmitter Works.

The Transmitters: First you will have to construct two of these identical transmitter circuits as shown below:

The operating principle of this powerful little transmitter can be understood from the following points:

The MIC converts the voice signals into electrical signals which is further amplified into high amplitude low current signals by T1.

This amplified signal is fed to the base of T2 which basically forms a frequency generator stage with the help of L1, C4, C5 and C3. Together this stage forms a regenerative oscillator which resonates in the range of 50 to 200MHz depending on the setting of the relevant LC tank components settings and values.

The amplified voice signals from T1 collector gets effectively modulated over the T2 high frequency carriers waves and this modulated signal is applied to the base of T3 for enriching it with high current.

T3 basically ensures that the modulated voice signals become significantly powerful with current, and is able to be transmitted to much longer distances with the help of an appropriate antenna.

The antenna does not need to be anything special, rather an ordinary 2 feet long flexible wire will be quite enough to enable the transmission to reach over 200 meter distance.

Along with these two transmitters you will also need a couple of FM receiver units or simply FM radios, so that the transmitted signals can be received by the respective radios and a conversation over the two sides can be completed.

Thus we basically have two sets of transmitter/radio through which two individuals are able to exchange their thoughts by speaking over the respective MIC inputs.

Each of the Tx/Rx sets must have mismatched frequency while the opposite side Tx/Rx must have accurately matched frequency response, in other words the opposite side Rx/Tx must be optimally tuned with a given frequency value which must be sufficiently different from the tuned frequency value of the other opposite Tx/Rx pair.

For example if one opposite Tx/Rx pair is tuned at 90MHz, the other could be tuned at 100MHz frequency just to make sure that each of the walkie talkie unit doesn't interfere with their own set frequency value.

Using an FM Radio as the Walkie Talkie Receiver (Rx)

The radio could be any type depending on the user's choice, but preferably it must have a convenient frequency adjustment button such as a knob or a up/down keys.

Your smart phone FM radio would also work but the range would be significantly less than conventional radio having a telescopic antenna. If you intend to operate the units for a room to room conversation then probably your phone would do the job as the receiver,

How to Tune and Test The Walkie Talkie Pairs

First make sure that your transmitter is correctly built and is actually transmitting the signals. To do this keep an FM radio at around 2 meters away from the Tx circuit, switch ON the Tx and the radio, and start adjusting the frequency knob of the radio until you suddenly find a "dead" spot on the band.

Now tapping lightly on the MIC should generate a thudding sound on the radio speaker, confirming the transmission from the Tx unit.

After this, keep increasing the distance between the Tx and the radio and finally try finding the maximum possible distance that the units are able to interact optimally. This may be done by some trial and error and by some skillful fine tuning of the adjustments of the two counterparts.

Repeat the same for the other Tx/Radio pair and this will complete your homemade FM walkie talkie circuit.

Now it's just about keeping the oppositely tuned units across the two sides from where the conversation needs to be done, and then with some more adjustments you can finally get the conversation going with this simple homemade equipment.

If you have any doubts, please feel free to share them through your comments.

Parts List for the above shown transmitter

  • R1 =1M,
  • R2 = 2K2,
  • R3 = 470 Ohms,
  • R4 = 39K,
  • R5 = 470 Ohms,
  • R6 = 4k7
  • C1 = 0.1 uF,
  • C2 = 4.7 uF,
  • C3, C6 = 0.001uF,
  • C4 = 3.3pF,
  • C5 = 10pF,
  • L1 = It is a 7 turn coil made using 1 mm super enameled copper wire, having 6 mm diameter. The center tap is taken from 1st turn as shown below.
  • T1, T2 = BC547B,
  • T3 = 2N2907B
  • MIC= electret MIC

L1 Coil Design

If you are having any confusions regarding the construction of this project contact me immediately, I'll help you through until your project is completed.

PCB Design

The PCB design for the proposed FM radio based walkie talkie circuit can be witnessed below:

single transistor walkie talkie circuit

As you can see, the antenna coil is designed on the PCB itself, through a spirally laid track layout, having the exact required embedded inductance. Thus the circuit becomes truly compact as it does not depend on the traditional, cumbersome, manually wound copper coil.

The supply being 9V, it works with extra power ensuring that the conversation is distinctly clear even at distances over 150 meters, which other similar transmitter would simply fail to accomplish.

Make sure to use a 1 meter long flexible wire for the antenna, to get a distortion free walkie talkie experience.

SHARING IS CARING!



Previous: 60 Watt Stereo Amplifier using Gainclone Concept
Next: How Blocking Oscillator Works

About Swagatam

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials.
If you have any circuit related query, you may interact through comments, I'll be most happy to help!

You'll also like:

  • 1.  How to Make a Light Communicator Circuit [using InfraRed]
  • 2.  1.5 watt Transmitter Circuit
  • 3.  Simple Walkie Talkie Circuit
  • 4.  Cell Phone Controlled Door Lock Circuit
  • 5.  Bluetooth Function Generator Circuit
  • 6.  Simple TV Transmitter Circuit

Please Subscribe (Only if you are Genuinely Interested in our Newsletters)


 

Reader Interactions

Comments

    Your Comments are too Valuable! But please see that they are related to the above article, and are not off-topic! Cancel reply

    Your email address will not be published. Required fields are marked *

  1. Search Related Posts for Commenting

  2. Ramanan.V says

    Can I get PCB for this transmitter? Pls mention cost & How to order?. Thanks &Regards.

    Reply
    • Swag says

      Sorry, we don’t sell PCBs or electronic materials from this website!

      Reply
  3. Sarwana says

    Hello Mr.Swag my question ,can i use variabel capacitor for change C5?

    Reply
    • Swagatam says

      Hi Sarwana, yes you can do it

      Reply
      • Sarwana says

        Mr.Swag , T3 = 2N2907B can change with bc557 ? Thanks

        Reply
        • Swagatam says

          yes you can try that!

          Reply
  4. Alyssa says

    Hi do you have the computations on how you have come up with this design? If yes I hope you could share them 🙂

    Reply
    • Swagatam says

      Hi, sorry, I do not have the calculations for this project!

      Reply
  5. mefiko says

    Dear inventor. .. thank you so much for your tutorials and help… my question is …is it possible to change some components to convert it to work on HAM range? Or can it be converted to a portable HAM?

    Reply
    • Swagatam says

      Hello, sorry that’s not possible, however I have a few good HAM radio circuits which I’ll be publishing soon…so please stay tuned.

      Reply
  6. Sunshine says

    Good day sir…engineer I made this circuit is working but is not going far as I need….I want it go upto 10km pls help me sir thanks

    Reply
    • Swagatam says

      Thanks Sunshine, I am glad its working for you, however it is meant for just around 500 meters, for 10km you will need a more sophisticated design such as as this:

      https://www.homemade-circuits.com/27-mhz-am-fm-transmitter-circuit-for-citizen-band-communication/

      Reply
  7. NimrA says

    Is there any alternative for L1 and centre tape capacitor??

    Reply
    • Swagatam says

      What is so difficult in it? It is a straightforward coil. You can try the PCB track embedded coil otherwise…

      Reply
      • Nimra says

        Actually, I have to make schematic of this circuit for project report and proteus doesn’t allow to connect wires in the middle of any component.(L1)

        Reply
        • Swagatam says

          In that case you can remove the entire T3 stage and its associated components…but this may cause the range to become quite less.

          Reply
  8. Francisco says

    Lista de peças diferentes da placa PCB. Diferenças nos transistores, capacitores com outros valores?

    Reply
  9. howtooz says

    Can you please make video for the connection of L1 and its center tapping?…its critical part

    Reply
    • Swagatam says

      It is already shown in the L1 coil design, you will have to do it exactly in the same way

      Reply
  10. Annes says

    Hello Swatagam,
    I’ve tried to build your circuit, but I’m having problems.
    The microphone doesn’t work at all (even when I replace it bij a stereo microphone), so I’ve connected a tone generator to the transmitter. This way I do get something of a transmission, but it is very dependant of the orientation of the antenna, and quite weak. The signal is also very much disturbed by regular radio transmissions.
    Do you have an idea what could be wrong?
    Thank you in advance from the Netherlands!

    Reply
    • Swagatam says

      Hello Annes, The mic should be an electret mucrophone, as given here:
      https://www.homemade-circuits.com/how-electret-microphone-works/
      this circuit has been thoroughly tested by me and for me it worked very nicely. Make sure the coil is built exactly as shown. I could transmit music upto 3rd floor using this circuit in my building. And when music is transmitted this circuit becomes even more powerful and long distant.

      If possible I’ll try to post a video soon.

      Reply
  11. Sunshine says

    Engr. Swagatam,thanks so much. Pls I need to build a multi dual tone frequency circuit.,..or any similar circuit.
    2..I need a circuit that can record voice and replay it at any time… Pleas help thanks

    Reply
    • Swagatam says

      For a multitone circuit, use a IC 555 astable and adjust it frequency through sa pot, or the same can be done using a 4060 IC.

      second circuit is given here:
      https://www.homemade-circuits.com/?s=voice+record

      Reply
  12. Smile says

    how many volts are the capacitors?

    Reply
    • Swagatam says

      normal rating, that you get in the market for the respective categories!

      Reply
      • Swagatam says

        …it should be higher than 12V

        Reply
        • Smile says

          Ok thank you, and also, what is L1 please?

          Reply
          • Swagatam says

            I have updated the details of L1 in the article, please check it out.

            Reply
  13. Shaikh Saad says

    Is the circuit tested?

    Reply
    • Swagatam says

      tested!

      Reply
  14. Batuhan KOC says

    How do we have to connect c7? the connection is not shown in diagram :/

    Reply
    • Swag says

      please ignore it, it’s not there

      Reply



Primary Sidebar

Electronic Projects Categories

  • 3-Phase Power (15)
  • 324 IC Circuits (19)
  • 4017 IC Circuits (51)
  • 4060 IC Circuits (25)
  • 555 IC Circuits (94)
  • 741 IC Circuits (18)
  • Amplifiers (49)
  • Arduino Engineering Projects (82)
  • Audio Projects (85)
  • Battery Chargers (76)
  • Car and Motorcycle (88)
  • Datasheets (45)
  • Decorative Lighting (Diwali, Christmas) (32)
  • DIY LED Projects (82)
  • Electronic Components (97)
  • Electronic Devices and Circuit Theory (35)
  • Electronics Tutorial (99)
  • Fish Aquarium (5)
  • Free Energy (34)
  • Games (2)
  • GSM Projects (9)
  • Health Related (17)
  • Heater Controllers (24)
  • Home Electrical Circuits (98)
  • Incubator Related (6)
  • Industrial Electronics (27)
  • Infrared (IR) (39)
  • Inverter Circuits (94)
  • Laser Projects (10)
  • LM317/LM338 (21)
  • LM3915 IC (24)
  • Meters and Testers (55)
  • Mini Projects (153)
  • Motor Controller (65)
  • MPPT (7)
  • Oscillator Circuits (15)
  • PIR (Passive Infrared) (8)
  • Power Electronics (33)
  • Power Supply Circuits (65)
  • Radio Circuits (9)
  • Remote Control (46)
  • Security and Alarm (56)
  • Sensors and Detectors (116)
  • SG3525 IC (5)
  • Simple Circuits (72)
  • SMPS (29)
  • Solar Controllers (60)
  • Timer and Delay Relay (51)
  • TL494 IC (5)
  • Transformerless Power Supply (8)
  • Transmitter Circuits (39)
  • Ultrasonic Projects (12)
  • Water Level Controller (46)

Follow Homemade Circuits

Facebook
Twitter
YouTube
Instagram
My Facebook-Page
Quora

Feeds

Post RSS
Comment RSS

Circuit Calculators

  • AWG to Millimeter Converter
  • Battery Back up Time Calculator
  • Capacitance Reactance Calculator
  • IC 555 Astable Calculator
  • IC 555 Monostable Calculator
  • Inductance Calculator
  • LC Resonance Calculator
  • LM317, LM338, LM396 Calculator
  • Ohm’s Law Calculator
  • Phase Angle Phase Shift Calculator
  • Power Factor (PF) Calculator
  • Reactance Calculator
  • Small Signal Transistor(BJT) and Diode Quick Datasheet
  • Transistor Astable Calculator
  • Transistor base Resistor Calculator
  • Voltage Divider Calculator
  • Wire Current Calculator
  • Zener Diode Calculator
  • Privacy Policy
  • About Us
  • Contact
  • Disclaimer
  • Videos – Circuit Test Results

© 2021 · Swagatam Innovations

We use cookies to ensure that we give you the best experience on our website. If you continue to use this site we will assume that you are happy with it.Ok