Raspberry Pi Pico AM Transmitter

Listening to AM, or amplitude modulated radio may not be as common as it once was, with other options (e.g. FM, satellite, Internet) long since taking over much of society’s listening attention. At the same time, it’s a brilliantly simple wireless transmission protocol, so much so that as shown here, it’s possible to make an AM transmitter with a Raspberry Pi Pico, a wire antenna, and a few discrete components.

The build is explained on this GitHub page, which provices the Arduino-C code that runs the device. As noted there, the Raspberry Pi generates a 1557kHz PWM signal as the carrier wave. The frequency stays the same, but the pulse width is varied as the amplitude signal. Audio input is taken in on the right side of the breadboard setup, with circuitry that cleans up the signal before it reaches the Pico. Even this bit of circuitry isn’t technically needed, but “you reeeally should have it.”

This particular configuration uses a two-meter antenna to transmit signals around about half of creator TudbuT's room. While the Pi doesn’t emit enough power to cause significant disruptions, with a long enough antenna it can cause interference. It's probably best to keep it at that length or less.

Although a simple project, it's pushing the Pico’s limits and overclocks the board to 200MHz in order to generate a high and accurate enough PWM signal. This will reportedly be fine 99.9% of the time, but if you want to be extra cautious, you could always add a cooling fan and/or keep it on a non-flammable plate. As for the Pico, at $4 you aren’t risking too much hardware-wise!