“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. 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.
Here is the schematic.
Motivation
A friend of mine had an idea: He wanted to build a guitar FX pedal that is essentially a short wave radio receiver. It should use the guitar cable as an antenna and it should be very straightforward to build. No weird coils, no exotic rotary capacitors, no Russian voodoo detector diodes. And it would be okay (or even desirable) if it’d be LoFi. He had some weird sound experiments in mind, probably in combination with synthesizers and funny effects.
So he asked me if I had an opinion on how to build such a thing. I answered that I am not the “radio type” of tinkerer. I had never built anything resembling a ham radio and had never played with a software defined radio receiver. But I said that “at least I think I understand the general working principle of AM radio“.
So, long story short, my friend had me “nerd-sniped” and I found myself doing some LTspice simulations … modulating/multiplying sine waves, etc. Let’s sum up the rules (“dogmas”) again that I set for myself:
No coils and no transformers -> No tuned LC circuits
No (mechanically) variable capacitors -> No tuned LC circuits
No special/exotic diodes
Must receive short wave broadcasts
KISS (Keep It Simple, Stupid)
So essentially to build a radio from scratch with no radio parts … but at the same time as simple as possible.”