A Prusa Printer Heatbed Picked Up Stereo FM Radio
Jeff Geerling and his father received a strong local station through a printer heater that was never designed as an antenna.
A printer’s heatbed got a radio reception test, which is a fairly ambitious way to find something to listen to while waiting for a print.
Geerling and his father connected a Prusa PCB heatbed to a NanoVNA. The instrument showed several rough dips in its standing-wave-ratio plot. The traces were designed to turn low-resistance DC power into heat. Geerling calls them “not at all optimized” for radio use.
Then came the listenable result: stereo reception near KYKY-FM in St. Louis, a station Geerling describes as transmitting at more than 30 kilowatts. His May 28 write-up is the first-person record of the experiment.
Play the video on YouTubeThe experiment began with a visiting maker’s question. Geerling credits Pooch from Repkord with asking whether the board could act as an antenna. A PCB already carries conductive traces, and PCB antennas exist elsewhere. The resemblance gives the question somewhere to start without establishing that this pattern of traces is a useful radio design.
The heatbed’s normal job sets an awkward requirement for that comparison. It is designed around low resistance and DC heating. Radio operation asks different things of the conductor, its geometry and its connection. The same physical board can participate in both experiments while being deliberately optimized for only the job printed on its box.
The instrument supplied an observation before the listening test. Geerling reports rough notches around 1 GHz, 130 MHz and 43 MHz on the NanoVNA’s standing-wave-ratio chart. He also says those notches weren’t well-defined. Recording where the plot changes gives another experimenter something to investigate; turning every dip into a claim of good performance would go beyond his account.
The listenable result then arrived under generous conditions. Geerling places the setup within a mile of KYKY-FM’s high-power transmitter. That is useful evidence that this conductor can receive something in that setting, while leaving its sensitivity and usefulness at other locations unmeasured. A kitchen spoon can pick up plenty of sauce when it is standing in the pot; judging it from across the room would be a different experiment.
For someone with a printer part on the bench, the sensible comparison would keep the receiver, station and location fixed, then change the receiving conductor. That could distinguish an amusing local success from a repeatable advantage over a simpler antenna. The reported test gives the idea a starting point without supplying that comparison.
Geerling calls the result “clear enough for stereo reception!” The proximity qualifier belongs beside that success every time it gets repeated.
A distance test would be a useful next experiment, with a conventional antenna alongside the printer part as the receiver moves away from KYKY-FM. That would show where the nearby tower stops compensating for this particular choice of conductor.