Parts and components required for FM Radio

Following components are used :

 Resistors–Resistors are needed to protect the more delicate components in the circuit and provide the required current to a component.

 Capacitors–Capacitors are used to get rid of the disturbances due to static current and some times convert minor a/c current in the circuit to DC.

Transistor - Helps in amplifying the sound and one transistor is use to convert radio waves to sound waves.

The Making

I built my radio on the breadboard. A breadboard is a way to do a circuit for temporary use- it is used to make up temporary circuits for testing or to try out an idea. No soldering is required so it is easy to change connections and replace components. Parts will not be damaged so they will be available to re-use afterwards. A sample breadboard circuit is shown below in figure 1.

Figure 1 - Breadboard Connection 

Amplification system - as you see on the schematic below the battery snap is connected to their corresponding terminals (+ and -). Then connect the electrolytic capacitor to the positive and negative terminals (see figure 2 below). Take the 470R resistor and connect one end of the resistor to the negative terminal and the other end to the transistor 9014’s (Lets call it Transistor 1) emitter. Connect the collector of Transistor 1 to a resistor (4.7k) and then connect the other end of the resistor to the positive terminal.

Next take transistor 9014 (Transistor 2) and connect it’s emitter to the negative terminal and then take it collector and connect it to a lead of resistor 10K, take the other lead of the resistor and connect it to the +ve terminal. Next connect the 470P capacitor’s lead to the base of transistor 1 and the other lead to transistor 2 collector. After that, take resistor 390K and connect those leads to capacitor 470P’s leads. Then take the one lead of capacitor 0.1uf to resistor 390K and leave the other lead of capacitor 0.1uf about 2 rows ahead.

FM tuner- Connect the black wire of the tuner assembly to the – terminal, the red wire to the + terminal, the blue wire to capacitor 0.1uf capacitor. Connect the antennae to the 0.1 Microfarads capacitor. I suggest using jumper wires to make the connections easier. RADIO READY!!

Troubleshooting

Try 1: The circuit connections did not work: I suspect poor or improper antennae connections.

Try 2: I rewired the circuit, but no good.

Try 3: I used my electronic lab (200 in 1 nextech Electronic Lab) to test whether my transistors were working or not. I found that the Transistors were in good condition.

Try 4: I ordered for another sets of the electronic components of the radio through the web from Cana kit.

Try 5: I assembled the radio with spring terminals: the sound was very feeble with the leads of components sticking out that caused static and disturbances.

Try 6: Then I built the same radio on a breadboard (see procedure) it worked really great, because the lead of components does not stick out and other disturbances where reduced to minimal amount.

Summary

I found out that in a radio there are 2 parts, the receiver and the transmitter. My hypothesis was partly right. The answer is that the antenna picks up a signal. That signal is a signal transmitted by a radio station. Then a tuner (variable capacitor and RFC combination) tunes it so that you only receive 1 frequency. Then the signal goes through an amplification system so that we can hear our favourite programs. I learned about electrical components such as resistors (that resists the flow of electricity), capacitors (capacitors are electrical components can hold electrical charge), transistors (the modern age technology is the transistor- which have 3 leads instead of 2, and can do many tasks, such as amplification).

Now I have two new questions those are:

1.      Now we have a pretty impressive technology called satellite radio so what will a radio look like in the future?

2.      Can we use other types of waves- Infrared for example-to take the place of the radio wave?

Limitations

-  The problem with radios is that you can only hear the station 30 –40 miles from it’s source so when going for long trips your favourite music fades into static. But that problem has been solved by the satellite radio

-  Because we can only have limited range of frequency now due to our technology and since a lot of other items are using the space radio frequency space is very limited and also companies will compete for getting their station on air.

-  If you are at your house and you call someone who is traveling in a C-train the signal might just get cut if the train suddenly goes underground. 

I thoroughly enjoyed learning about the basics of electronics and the radio. Now after reading this I hope that you have learned and had fun as much as I did from doing this science fair project!!

Acknowledgements

I thank my parents and my uncle (S. Sivakumar) for helping me understanding the basics of electronics and also for guiding me for my project.

I also thank my class teacher Ms. Emily Brown and 6th grade teacher Ms. Cathy Kurio for supporting me for the CYSF and to publish this in the virtual science fair.