Amateur radio ("ham radio") is a pastime in which you communicate with other amateurs around the world. You might not think it has much place in the 21st century, with near-instant communication anywhere in the world via the Internet, but amateur radio has never been so popular. There is a certain joy in making contact with a person on another continent using less power than a light bulb takes!
Radio is a technical pastime in that you are at liberty to build your own aerials ("antennas"), while more experienced amateurs are also allowed to build their own radios. Amateurs are also active in exploring new encoding schemes for communication, especially in the low-frequency bands that are starting to become available.
You might be surprised to learn that amateur radio is intensely competitive. There are competitions most weekends, and amateurs of all grades can take part in them. These mostly consist of making contact with as many other people as possible in a fixed time period, though there are exceptions.
Amateur radio is ideally suited to those days when you have free time but can't get out to do sport because of the weather. But it's not just an indoor pastime for the winter months: there is a tradition of (and awards for) operating radios from the top of mountains, from islands, lighthouses, railways, and so on.
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