Build a FM radio transmitter

This is a guide to becoming a techno rebel: a guide to becoming a radio pirate and raiding the silent airwaves with your own content. This is a follow up to my recent call for relaxing the grip on radio broadcasting in the Maldives.

One of the easiest transmitters to build is a FM transmitter. A basic low power transmitter can be assembled in a few hours, using a minimal set of equipment and components and best of all, it can be done without denting the wallet too much. I am going to describe how to build a very low power FM transmitter. Do not expect this to cover the entire country, an atoll or even an island - it surely will not. However, it will be able to transmit around a block (maybe more with a good antenna) which is more than enough to tread into the world of radio and let yourself be heard.

Notes on construction:
- You need basic familiarity with electronics to undertake this project. If you studied GCE O' level Physics (or A? level Physics) then you should be familiar with the basic knowledge to go ahead with the construction.
- You can build this using a variety of construction techniques. The preferred method would be using strip board or perf board however point to point wiring would work too. Have a look here for a quick intro to circuit construction methods. Strip boards ARE available in Male'.
- The components given below can be interchanged for a equivalent and values can be approximated. So go ahead and scrounge around broken electronic items for the required components - chances are you will find most of them in broken TVs, Radios and even some toys.

- 100 Ohm resistor ( brown black brown )
- 100k Ohm resistor ( brown black yellow )
- 15pF ceramic disc capacitor
- 5pF ceramic disc capacitor
- .001uF ceramic disc capacitor
- 1uF electrolytic capacitor
- BC548 or BC108 or equivalent transistor
- Length of insulated copper wire
- Two 1.5 Volt AA size batteries
- Audio jack


Circuit diagram for FM transmitter

The tuning coil used is a length of the insulated copper wire wound around a small pencil about 6 times. The circuit can be tuned to the broadcast FM range by adjusting the coil appropriately. Turn on a FM radio and set it to the frequency you want this circuit to transmit at. Next, try squashing and/or spacing the coil turns until it is tuned to the desired frequency.

The audio can be fed to the transmitter via a tape player, a PC or even an Ipod. All that remains is for you to make your killer radio programs and broadcast it. Have fun! ;-)

The above circuit that I built on a small piece of strip board.


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