When we think of a spark gap radio transmitter, most of us immediately imagine an early twentieth century ship’s radio room or similar. Most of us know these transmitters as the first radio systems, ...

When one thinks of portable consumer electronics that are now largely obsolete, portable CD players, minidisc players, and portable cassette tape players are products that immediately come to mind.

The squat, bland, concrete-block building on a side street in St. Louis Park looks like it could be a meat locker, an auto parts warehouse or a CIA safe house hidden in plain sight. But step inside, ...