Saturday, August 11, 2012

Simple FM Walkie Talkie

Here a simple method for making a walkie talkie is illustrated. The principle behind this walkie talkie is by using two pairs of fm transmitter and receivers are combined together to form a walkie talkie.
That is each device contains one receiver and one transmitter. Transmitter of one device will be set in a low fm range (88-95mhz) and the other will be tuned in high fm range (103-108mhz).




FM Transmitter
Description.
With a matching antenna, the FM transmitter circuit shown here can transmit signals up to a range of 2 kilo meters. The transistor Q1 and Q2 forms a classic high sensitive preamplifier stage. The audio signal to be transmitted is coupled to the base of Q1 through capacitor C2. R1, R3, R4, R6, R5 and R9 are the biasing resistors for the preamplifier stage comprising of Q1 and Q2. Transistor Q3 performs the collective job of oscillator, mixer and final power amplifier.C9 and L1 forms the tank circuit which is essential for creating oscillations. Inductor L2 couples the FM signal to the antenna.

Circuit diagram.



Notes.

    Assemble the circuit on a good quality PCB.
    The circuit can be powered from anything between 9 to 24V DC.
    Inductor L3 can be a VK220J type RFC.
    For L1 make 3 turns of 1mm enamelled copper wire on a 10mm diameter plastic former. On the same core make 2 turns of 1 mm enamelled copper wire close to L1 and that will be L2.
    Frequency can be adjusted by varying C9.
    R9 can be used to adjust the gain.
    For optimum performance, value of C8 must be also adjusted.
    Using a battery for powering the circuit will reduce noise.




FM Receiver


This is the most simple fm radio receiver with good performances that works great even if the sensitivity is not too high. The working principle of this fm receiver may seem a little unusual. It is made of an oscillator (T2 and T3) that is synchronized with the received frequency of T1. This transistor works as a broadband preamplifier in VHF range.

The oscillator is adjusted between 87 … 108 MHz with C5. Because of the synchronization, the oscillator output will have the same frequency deviation as the received signal from the fm antenna. This deviations are caused by the broadcasted audio informations. The frequency modulated signal show up on P1 + R5. Low pass filter R6/C6 extracts the audio signal and then is amplifier by T4 … T6 and transmitted at the output through C9 capacitor.
FM Receiver Circuit Diagram



The coil details are presented in the fm receiver circuit diagram. The radio receiver is adjusted on different stations with the help of C5. P1 potentiometer is adjusted untill the best reception is obtained. If we attach an audio amplifier and a speaker then this fm receiver can be made very compact as a pocket radio.


Make 2 pairs of transmitter and receiver. 



Arrange boards in two cases as shown in figure
Tune both transmitters in different  frequencies.
Attach antenna, speaker and mic to the respective boars.



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40 comments:

Sultan Allawati said...

Hi
Is this circuit ready to use,
Is it been tested??

ANUP JOSE said...

I hav given more importance to the concept than the circuit

MayurSinh Parmar said...

Hi i am gonna make this project but
1.what is the 'audio in' in fm tx circuit..?
Can i use microphone.?

2.should we use two saperate antennas for tx and rx in one set or only one antenna....and how...??

ANUP JOSE said...

ya sure you can use it. you should use two antennas in one single system
#Admin

rocky said...

how to connect speaker form AF ?
can i connect directly

Lj Sagun said...

do i need to add LM386 pre amp to AF or just connect it directly??

Jeaneth Arandilla said...

can i ask if the value of the transistor is available in the Philippine market?? thanks

Mohammad Zohaib said...

How can we produce 88-95 MHZ and 103-108 MHZ?
And what frequency this circuit is producing?

ANUP JOSE said...

@mohammed: by varying the capacitance you can produce 2 variable requencies

ANUP JOSE said...

@Lj:not necessary

ANUP JOSE said...

@rocky: you can connect it directly

ANUP JOSE said...

@Jeaneth Arandilla : Sorry i dont know about Philipine market

ANUP JOSE said...

@MayurSinh Parmar : Yes you can use a microphone
For better clarity you should use two separate antenna's

ganesh said...




Report Bugs Topic tells about the bug reports of this blogs....



Walkie Talkie in Jaipur

Vincent Schotel said...

Can this system be built on one freqeuntie so more walkie talkies can communicate with another?

john ocharive said...

Hi i like your circuit design but I see it cover only 2kilometres. So how can I make it to cover up to at least 5kilometres?

Jun Cabera said...

Hi i like your circuit too, but im thinking if the list of materials is available in philippines? Do you have some circuit for transmit or receive only? Can you please help for my prototype "any wireless communication " Thankyou so much..

priyansh agrawal said...

Hi i like your circuit is any one tested the circuit..!!

mohd raqib Amirudin said...

how do we know that the circuit give out 87 … 108 MHz?

Debojit said...

Hi,
Thanks for your idea. I am planning to build exactly the same thing, but my concern is to make it a little bit smaller and to run the entire thing on 3-5v input.
Also as per fm receiver i am using TEA5757 PLL controllable board, which will help me reducing the size of the system.
Could you tell me if i can run the circuit on 5v and if it can't be directly run with 5v battery, what values should get changed in the transmitter side?

Unknown said...

Hi am if I tune the frequency in 97mhz then will it work with my cellphone radio

Supritam Choudhury said...

Hi am if I tune the frequency in 97mhz then will it work with my cellphone radio

Unknown said...

i wants to make it now

Unknown said...

what are the components required for the implementation of the same?

utkarsh verma said...

variable capacitors are not available in my city......Please suggest any other component which can be used in its place.

veeru royal said...

Where we have to connect speaker in reciver u have not specified any where

Aricc Herat said...

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Ahmed Khan said...

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Jack Waeger said...

is their somewhere i can get a list of parts for this circuit without having to go through the pictures and doing it my self, just so i don't get the wrong component

Jack Waeger said...

is their somewhere i can get a list of parts for this circuit without having to go through the pictures and doing it my self, just so i don't get the wrong component

Unknown said...

I need the abstract for the project walkie talkie..can u pls tell me where can I find that?

madhu raj said...

I need the abstract for the project walkie talkie..can u pls tell me where can I find that?

Unknown said...

can any one can give a correct diagram of a walkie talkie

Lekha Rajendran said...

can any one can give a correct diagram of a walkie talkie

Ritik Ranjan said...
This comment has been removed by the author.
Yaseen Shaik said...

Is same circuit is used for transmission and receiver

sky light said...

Can any one give me the pcb print for this circuit

sky light said...

OR
At least can anyone can give me the perfect list of components with its type and all ?

Mark Jason Ong said...

Where is the speaker in the fm receiver circuit?

sarah kupal said...

anybody already make this? is it working? please let us know. thank you.

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