In broadcasting and radio communications, a callsign  (also known as a call sign or call letters, or abbreviated as a call) is a unique designation for a transmitting station.

In Australia, all radio stations are issued with a callsign by the Australian Communications and Media Authority (ACMA). A broadcast station can nominate call letters of preference, or have them allocated.

All Australian radio callsigns feature a numerical prefix with the number relating to the state or territory in which the station is based, as follows:

1 = Australian Capital Territory (new designation) 
2 = New South Wales (and ACT)
3 = Victoria
4 = Queensland
5 = South Australia
6 = Western Australia
7 = Tasmania
8 = Northern Territory

After the numerical designation, there is a two-letter suffix for AM stations in the form nXX (eg: 3LO, 4KQ, 5AA) or a three-letter suffix for FM stations in the form of nXXX (eg: 3MMM, 2DAY, 6RTR) .

There are occasional exceptions to this rule, such as 3RPH Melbourne which broadcasts on the AM band, and 5UV Adelaide, which is now an FM station.

A callsign may: There is no legal obligation  for a broadcast station to identify itself with its official two or three letter callsign, so many stations have a separate "on-air identification", for instance 2SYD = "Nova 96.9"; 3EE = "Magic 1278" and 2XXX = "NXFM". Some stations choose to shorten their on-air name for ease-of-use, such as 3FOX = "Fox FM" and 5MMM = "Triple M".

Some FM callsigns reflect the origins of the station as an AM broadcaster. In many cases when AM stations converted to FM, they merely added a letter to their callsign (eg: 3KZ Melbourne became 3KKZ; 5SA Adelaide, SA. became 5SSA and 4TO Townsville, Qld., became 4TOO).

If you want a complete list of Australian callsigns, you can download the current ACMA Radio and Television Broadcasting Stations Book here.

Alternatively, you can search the Register of Radiocommunications Licences.