What's Hamradio?
Hamradio is a word for the legal radiohobby. People who have this hobby are called: 'Hams'.
A special license is required to transmit on frequencies that are free to use for radio-amateurs.
To get such a license with the required callsign, you have to make a special examination with good result. In most cases, this depends on the country that you live in.
Hamradio is a very wide ranged hobby, with a lot of possibilties for everybody's interest. For example, there are
radio-amateurs who build and/or modify their own transceivers, who have their own television transmitters (Amateur TeleVision), who are talking via special satellites,
who have their own wireless computer network (Packetradio), who are talking to far country's (DX) and even who make connections via the Moon!!! (EME, Moonbounce).
It's also possible to talk to the astronauts in the ISS (Internation Space Station) when it is in range. All these possibilities are the reason why I became a HAM in 1998, after being a CityBand-station (27 MHz) for about 3 years.
The CB-radio hobby is also legal in a lot of country's and it's a beautiful way to discover the 'strange' hobby called Hamradio without passing an examination.