You are going to build an AM radio transmitter AND you will be shown how it works. When you finish your radio, it will look something like mine in the picture above.
I have attached the PDF file in the last step to this Inst'able for those without a pro membership.
Step 1: Parts and Prep
These are the small components you will need
- 555 timer chip
- NPN transistor
- two #103 capacitors (0.01 microfarads or 10,000 picofarads)
- #102 capacitor (0.001 microfarads or 1,000 picofarads)
- some short wires
- two 1 Kilohm resistors
- 10 Kilohm resistor
- 1/8 inch (3.5 millimeter) female audio jack (yours may have more or less than three
- wires, but it must have at least two)
- 5 Kilohm potentiometer
These are the Bigger components you will need
Step 2: Schematic Diagram
- 1/8 inch (3.5 millimeter) male audio cable
- AM radio receiver
- Antenna. Yours doesn't have to be made out of a pop can, but the pop can works
- Breadboard
Step 3: Test your radio
To test the AM radio transmitter, simply set the antenna next to your AM radio receiver (Alarm clock) tuned to approximately 600 KHz. Then play with the potentiometer until you can hear your music on your radio. The frequency generated by this devise will be anywhere from 100-480 Kilohertz if you used all the correct component values.If you hear weird sounds when you turn the potentiometer (and do not hear the audio signal) That means that your radio is working, but your audio signal needs to be configured. try turning the volumed of your audio signal up.
How does this work?
The audio signal is controlling when the radio signal is being transmitted. this is called amplitude modulation (See picture above).
You are transmitting at a low frequency that can be heard at higher AM frequencies. Lets say I transmit music at a base frequency of 300 Kilohertz (KHz) This music can be heard at the frequencies of 300KHz, 600KHz, 900KHz, 1200KHz. (etc...) This is called harmonics.
When the radio receiver's picks up a 300KHz signal on a 900KHz band, the signal is weaker than if you were to pick it up on the 600KHz band. This is why harmonics are only useful to a degree.
