Michael Wiebusch Builds a Shortwave Receiver with a Difference: It's Driven by 74xx Logic

Michael Wiebusch has built a shortwave radio with a difference, boasting no coils, variable capacitors, or "exotic diodes" whatsoever: Instead, it's based around 74xx logic chips, creating what Weibusch describes as a "74xx-defined radio."

"I built a shortwave radio receiver from scratch using only cheap and easily available components, i.e. standard transistors, op-amps and 74xx logic chips," Wiebusch writes of his project. "No typical radio parts – no coils, no variable capacitors, no exotic diodes. This project is easy to build and gives you a hands-on experience with radio technology which you won’t get from a fully integrated SDR [Software-Defined Radio]."

To make things interesting, after having been challenged by a friend to build a guitar effects pedal based on shortwave radio technology but "very straightforward to build," Wiebusch set out a series of rules for the project: No coils or transformers, no mechanically-variable capacitors, no special or otherwise exotic diode types, that it must be able to receive shortwave radio broadcasts, and to "Keep It Simple, Stupid."

The solution Wiebusch found was in a heterodyne receiver, but with a twist: The radio-frequency mixer was replaced with a 74HC4051 analog multiplexer, a local oscillator with a 74HC4046 phase-locked loop (PLL), a custom op-amp bypass for filtering and amplification, and another op-amp circuit as a demodulator. Wiebusch even found time for a pair of optional upgrades: A replacement local oscillator in the form of a ready-made high-frequency clock generator from Adafruit with Arduino control, and a better RF input amplifier.

Weibusch's full write-up is now available on his website.