Building a Radio When the Grid Is Gone
Three workshop notes on seeing a machine as parts simple enough to make by hand.
If the machines have taken the grid, the hardest knowledge to replace may be the kind that lets you build a radio from scratch. Tonight's three stories, all from Hackaday and all published on 1 October 2026, circle that problem from different angles: a purely mechanical transmitter, the physics of drying a material in a vacuum, and a tool that teaches you to see a receiver as a chain of simple parts.
Start with the most audacious. Hackaday writer Al Williams reported on a proposal by the maker known as [The Mike Stuff], who "asserts that ancient people like the Greeks could have built a form of radio that was purely mechanical." The scheme uses a waterwheel to compress air, which is then blown through a rotating disk with slots in it. A valve amplitude-modulates the airflow, and gramophone-style horns amplify the signal at both the sending and receiving ends. Demodulation, the article says, needs no power source at all.
Williams calls the idea buildable in theory but impractical. Controlling the speed of the slotted disk with water power would be a challenge, he writes, and Mike himself predicts listeners would mostly hear a 10 kHz buzz. Hackaday framed the piece as a fun idea rather than a working device, and no prototype was built. Still, the point survives: a signal is just something you can switch on and off and amplify, and none of that strictly requires electricity.
The second story is about heat, and it is more immediately useful. Maya Posch, continuing a series on drying materials, explains that moisture held inside a material rather than on its surface has to be driven out with heat, not just low pressure. In a vacuum there is no matter to carry that heat by conduction or convection, so radiation is the only route left. Her test rig fed power through banana-plug terminals sealed with silicone O-rings to a self-regulating PTC element rated to 70 °C on 5 V DC; it drew about 1 A at first and about 0.3 A at 60 °C. The sample was 3.25 grams of blue-to-pink desiccant in a plastic bag, inside a chamber a diaphragm pump pulled down to -0.8 bar. She adds that drying desiccant in a microwave is aggressive, citing reports of it going badly.
The third story names the mental habit that ties the others together. Hackaday's write-up of SDR, a software-defined radio program by developer Julian Haag, opens by noting that "it is often helpful to think of a radio as a series of interconnected functional blocks, hence the use of block diagrams to convey how a given radio operates." Haag gave the program the feel of a modular synthesizer: you drop in blocks such as a radio, a demodulator or a speaker and link them with patch cables. It decodes ADS-B, POCSAG, SSTV, DAB and RDS, and offers passive radar and direction finding.
The tool itself needs a computer, which is exactly what the premise takes away. But the idea underneath it does not. A receiver is a sequence of stages, each doing one job, that can be connected in different orders, and once you can see those blocks, you can start asking which of them you could coax out of air, water and a horn.
Sources
- A Mechanical Radio, Sort Of · Hackaday
- Vacuum Drying and Making Stuff Hot in a Vacuum · Hackaday
- SDR Lets You Patch Together Your Setup · Hackaday