Mobile ham radio is the practice of amateur enthusiasts engaging in two-way radio communications. It usually uses low-powered broadcasting over shortwave frequencies. There is a long-established community of ham radio users, complete with customs and traditions. Most countries specifically allocate frequencies for use by ham radio.
In most countries, a license is needed to use mobile ham radio. In some cases this is merely an administrative process, while in others there must be a display of technical expertise. At one time it was common for licensees to demonstrate an ability with Morse code, but this is rarely required today.
A licensed mobile ham radio user will often have much more flexibility than other forms of licensed broadcasting. For example, while a television or radio station has a fixed frequency, a ham radio user is normally allowed to use any frequency they like within a designated band. This gives them much more control over the distance over which they communicate, making it possible to talk to users in the same city or on another continent.
Mobile ham radio can often serve as a fallback form of communications in an emergency. This can be particularly useful as ham radio tends to use a wide variety of frequencies, while professional set-ups are usually restricted to particular bands. This can mean it is more likely to find ham radios in operation after a natural disaster has brought down more established lines of communications.
It can be argued that mobile ham radio's appeal has been greatly diminished by the growth of other forms of communication, most notably the Internet. For example, online chatrooms could fulfill a similar role. This is not necessarily the case, however, as in many cases the technology side of ham radio is as important as the communication itself. The Internet can also benefit the hobby as it makes it easier to share and find information about producing or repairing equipment.
The origin of the term "ham radio" is most commonly believed to have been a term of abuse from professionals to amateur, similar to calling somebody a "ham actor." It was quickly adopted by mobile ham radio users as a more positive term. There are several other theories that state that HAM is an abbreviation, for example for a radio station call sign, the name of a magazine or even the names of radio pioneers. None of these theories stand up to close examination.