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takyon writes:

Building a Time Machine for Radio

[Thomas] Witherspoon's time machine is The Radio Spectrum Archive. The technological advance that makes it possible is the proliferation in recent years of cheap software-defined radios (SDRs), which can digitize enormous swaths of radio spectrum. The SDR's software can be used to select individual transmissions and listen to them live. Or the swath of spectrum can be recorded and played back through the software later, letting listeners tune into broadcasts just as if they were live.

Shortwave listeners and amateur radio enthusiasts have been using SDRs mainly to find interesting signals, "but not a lot of people thought about saving the spectrum and archiving it. But there were those who had," says Witherspoon. Part of their motivation was to capture how radio has been evolving in the Internet era: "The AM broadcast band here in the States, the FM broadcast band, and...the shortwave broadcast band, are going through a lot of changes, especially the shortwave bands. A lot of stations are going off the air."

[...] It's the large size of the recordings that poses the biggest obstacle to Witherspoon's plan to gather more recordings and make them publicly accessible online. One way the team is tackling the problem is by focusing on preserving recordings associated with newsworthy events. For example, "when the North Korea talks were happening, we were doing AM broadcast-band recordings. But since the news didn't change a lot during the day, we chose to preserve only a 2-hour segment." Witherspoon estimates that they currently have about 150 terabytes of recordings "curated to the point that it's worth uploading them."

[...] The Radio Spectrum Archive is currently working with the nonprofit Internet Archive to host recordings and make them publicly available. One issue is the need to settle on a standardized spectrum-storage format. Once that is done, then it's hoped a Web-based interface can be created to browse and play back the recordings. Witherspoon is seeking volunteer developers to work on this interface.

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