by 
tozapeel
ANSWERS: 2
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The guts of a a transmitter or receiver is just a tuned circuit - an inductor and capacitor in a loop. The current and voltage occillate and some power leaks into the air as radio waves, or is absorbed from nearby radio waves. Just touching a battery across the loop and letting go will make a signal. To send more than just morse you need to make the occillations continuous, and modulate them. The following site has a circuit diagram: http://www.zen22142.zen.co.uk/Circuits/rf/amtx.htm (The inductor capacitor loop is at the top right)
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You want simple? Let's say you were stranded in a car, and there was no one around from whom to get help. What could you do without a cell phone or other manufactured transmitter? Well, in the old days, you could take the spark coil out of your Old Ford (or whatever), connect your battery to the ends with wires, one of which is broken in the middle, then take a bit of wire on one end of the coil for an antenna. Then, assuming you know some Morse Code, you could send out a message that WILL be heard if anyone is listening to a radio of some kind. This is called a Spark-Gap transmitter. It covers such a wide band of frequencies that it would be hard to go un-noticed. The emergency construction and use of one of these has actually brought help and saved lives in the past. That's simple (if your car is old enough ;)
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