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Subchannel Stations: The Radio Broadcasts You Didn't Know Were There
Analog radio broadcasts are pretty simple, right? Tune into a given frequency on the AM or FM bands, and what you hear is what you get. Or at least, that used to be the way, before smart engineers …
Long before Wi-Fi, streaming, and digital multiplexing, these hidden signals beamed anything from elevator music and stock tickers to specialized content for medical professionals. The technology was used to deliver things like weather reports and stock prices to early smartwatches and coffee makers in the days before WiFi and celluar internet were cheap and everywhere. Some hobbyists rigged up surplus SCA receivers—often stuff found at flea markets or hamfests—to get free background music, weather reports, or any niche audio that happened to be riding along.
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