Make a simple AM transmitter that will cost you less than $5.
Step 1: Stuff you need
A crystal whos frequency is between .9000 and 1.2000 MHz.
A male headphone jack
A breadboard or experimental circuit board (optional)
Step 2: Wire it up
The crystal should have a little black dot on it. This is the only pin that we will not use on the crystal. We will connect the red wire of the headphone jack to the pin above the black dot. The white wire can also connect here if it is a stereo jack. We will connect the black wire or the ground to the pin to the right of the dot.
Step 3: Connect an antenna to it
Connect the last pin (the pin opposite of the dot) to an antenna. I used a really long telephone wire for my antenna (25 feet or so). I got it to play through my whole nieghborhood. Any sort of insulated wire will work for an antenna.
Step 4: Tune your radio
You now have to tune your radio to whatever your crystal says. The crystal will show the frequency in MHz and the radio will show it in KHz. If you used a 1.0000MHz crystal then you will tune your radio to 1000. 1.2000MHz crystal will give you 1200 on the radio and so on.
It may take a little time to find your station but it should work.
The louder you turn your music up, the louder it will be on your radio.
-I also found a better version of this. It uses a modulator. This improves the system a ton. Check out the second picture to see this with the modulator.