The advent of the transistor in the mid-1950s meant people could carry their radios with them for the first time. One electronics manufacturer even made a name for itself building transistor radios -- Sony.
Unlike AM and FM receivers, shortwave radios, like this one from the 1950s, can receive signals over long distances. This made them very popular among those who wanted to know what was going on around the world. In the 21st century, however, shortwave stations are losing ground to higher-fidelity Internet radio.
Photo courtesy Pandora Media, Inc.
Pandora Radio is different from other Internet radio sites. Rather than relying simply on genre, user connections or ratings, it uses a Music Genome.
Photo courtesy Amazon
HD Radio is an all-digital form of radio that made its first appearance in the mid-2000s.
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Satellite radio took off -- pardon the pun -- in the 2000s when XM Radio and Sirius Satellite Radio began offering service. Financial concerns would cause them to merge a few years later.
Shock jock Howard Stern made waves in 2006 when he signed a seven-year, $220 million contract with Sirius Satellite Radio, leaving terrestrial radio behind. To learn more, read How Radio Works or watch the HowStuffWorks Satellite Radio Video.