'''Amateur Radio''', also called by some "ham radio", is a hobby
pass-time followed by people in most countries of the world, using internationally coordinated, specifically designated, frequency bands. Each country or jurisdiction separately allocates the frequencies and licenses its operators to use specific power levels or modes of communication. They are issued a personal callsign that has letters reflecting their country's international callsign area, a number reflecting the state or region, and letters that particularise the callsign to them. See examples below.
Operators set up their stations normally in their homes, and use antenna systems suitable for their domestic situation. This may limit the frequency bands on which they can operate, as longer wavelength transmissions normally require larger antenna. Also, larger aerial arrays are needed to achieve higher transmission gain on higher frequencies. Vehicle mounted radios and antennas can also be used.