Walkie Talkie: Final Year Project

I haven’t been writing much lately as I was busy with my final year project. The cricket world cup is also here and India has a good chance of topping their pool with three out of three wins already.

Moving on to the Walkie Talkie project!

So I started with my final year project along with five of my friends.

Walkie Talkie is basically a wireless communication device. It follows a half-duplex communication principle, which means you can either talk or listen at a time. In our model we will be designing a transmitter section, a receiver section and a switching unit. The switching unit will let the user decide whether he or she wants to listen or talk. We will be using a switch here and this will also act as a push to talk button. This means it will normally behave like a receiver and one will have to push the switch to talk.

The walkie talkie will work on a frequency modulation (FM) range (88 MHz to 108 MHz). The reason why we have chosen FM and not AM (Amplitude Modulation) is because of some advantages FM has over AM and I am not going to bore you all by writing those here.

To receive the FM signal we will use a FM receiver, which is normally known as the FM radio. As the FM range is very busy, there might be interference from strong signals like ‘Radio Mirchi’ (98.3 MHz), ‘Big FM’ (92.7 MHz) or any other signal produced by government services operating in the FM range. Thus our device will work only for a short range of 10 to 20 meters.

With increase in the distance between the transmitter and the receiver, signal strength will weaken and other stronger signals will be ‘locked in’ by the receiver.

We chose a smaller transmission range because one needs permission from Telecom Regulatory Authority of India (TRAI) to transmit signals over the range of 20 meters.Untitled

As in the above figure, we can see two identical handsets. We need to construct two identical handsets for the communication to complete. Here I am going to describe a bit about each of the sections individually. Starting with the components, first of all we need a condenser microphone and a speaker. The microphone will basically work as an input device and receive the voice signals from the user, whereas the speaker will act as the output device.

We will be constructing a transmitter which will modulate the input voice signal and transmit it through an antenna. The receiver on the other handset will be responsible for receiving this transmitted signal.

The voice signal will enter into the circuit through the condenser microphone and the input will get amplified as per the specifications of our transmitter. The transmitter will modulate the low frequency input and transmit it with the help of an antenna.

The antenna of the other handset will receive the transmitted signal provided it is tuned to the same frequency with which the original signal was transmitted from the first handset. After receiving the signal, the receiver section will decode the voice signal and amplify the received signal. Finally, the user on the receiving end will get to listen the original voice through the speaker.

As of now we have just designed a prototype. In the coming weeks we will be implementing the circuit on a veroboard. As we proceed we will test and rectify the circuit if required.

Akash Chaudhuri
Email Id: akashchaudhuri93@gmail.com
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