Sheet 5 · The lab
Things you
can operate
Explore the ideas and principles that underlie radio. Some ideas are easier to understand when you can turn the knobs yourself. Each page in the lab is a small, interactive machine that runs in your browser. There is nothing to install. Mess around until it starts to make sense.
- The Fourier transform
The Secret in the Sound
Every sound is a stack of pure tones. Pull one apart with your own hands, and find out how a receiver sees a whole band at once.
Open it - Modulation
Riding the Wave
How a voice gets onto a radio wave, and off again. Morse, AM, single sideband, FM and the digital modes, each one a thing you can play with.
Open it - Numbers stations
Numbers in the Night
A voice on shortwave reads out groups of five figures. Nobody says who it is for. What these stations are, and why the code cannot be broken.
Open it - The superheterodyne receiver
Meet Me at 455
A filter you tune gets wider as you tune up. So almost every radio keeps one sharp filter in one place and brings each station to it. Tune a crowded dial, multiply two waves, and chase the ghost station.
Open it - Multilateration
Who Heard It First?
One plane never says where it is. Rooftop receivers hear its radio burst a few millionths of a second apart, and that is enough to find it. Start with thunder, find the curve hidden in a gap, then borrow a clock from a passing plane.
Open it
Miscellaneous
Off the dial
Not necessarily about radio. Similar interactive guides exploring other complicated concepts.
Want to build something real?
The lab is for ideas. The written guides are for building a real station: what to buy, what to install, and how to connect it all.