(Image credit: Element 14 via YouTube)
Engineers and makers have been repurposing, or upcycling, old electronics for decades. In the 1950s and 1960s, resourceful people would modify old military surplus electronics left over from WWII for everything from amateur radio to tube-based guitar amps. The upcycling trend is still in full-swing here in the 21st century, which is demonstrated by Clem from MAYER MAKES as he transforms a pair of vintage microphones into an emergency radio system.
Motivated by a recent flood, and a desire to repurpose old RF modules, Clem details how he utilized low-pass filters, amplifiers, and comparator circuits to modulate audio onto a carrier frequency. He started his build by retrofitting the microphone's housing, incorporating a 3D-printed extension ring using conductive PLA to handle modern components while trying to keep the device's original aesthetic.
For the emergency radio's antenna, Clem utilized tinned copper wire he straightened using a drill, which he then secured using custom 3D-printed inserts. Every engineer encounters challenges with project builds, and Clem is no different. His initial tests of the radio showed mixed results. Although the transmitter emits signals, they generate digital pulses rather than analog sine waves. The culprit turned out to be the RF modules, which are designed for digital communication and pump-out data as on/off pulses.
To overcome that challenge, Clem combined a PWM carrier signal with an amplified microphone input, which encoded the audio into a digital format. Despite his efforts, performance remained limited, providing a transmission range of just a few meters and poor audio quality. Regardless of the outcome, it provided Clem with invaluable insight into analog electronics and signal modulation. Watch the video above for more insight into his build.