All ham radio call signs begin with letters (or numbers) taken from blocks assigned to each country of the world by the ITU - International Telecommunications Union.
ITU is the United Nations agency for information and communication technologies.
Each country's regulating agency will, in turn, allocate a unique call sign to each newly licensed ham radio operator.
For example, my call sign VE2DPE was taken from the block of prefixes VAA-VGZ allocated to Canada by the ITU.
My call sign, as every other amateur radio call sign in the world, is composed of three parts:
Canada's telecommunications regulating agency - Industry Canada - can also pick amateur radio call sign prefixes from the following blocks of letter prefixes: CYA-CZZ, VAA-VGZ, VOA-VOZ, VXA-VYZ, XJA-XOZ, CFA-CKZ.
(Canada's regulating agency used to be Communications Canada, but that's another story).
In the United States, ham call signs are allocated by the FCC from the following blocks of letters: AAA-ALZ, KAA-KZZ, NAA-NZZ, WAA-WZZ.
The complete updated list of country prefixes of international amateur radio call signs is available here.
73 de VE2DPE
7, Rue de la Rive, Notre-Dame-des-Prairies, Québec, Canada J6E 1M9
QTH Locator: FN36gb
Is a member
in good standing