Heard some chitterchatter recently on one of the repeaters regarding callsign structures. I thought I'd clear out some of the stuff in my mental attic, so here goes:
- By international treaty, the USA is allocated W, K, N, and AA-AL, technically WAA-WZZ, KAA-KZZ, NAA-NZZ, AAA-ALZ (AMA-AZZ being allocated to other nations).
- Internally, the FCC decides how to break up those allocations into the various services.
- Way back in the day, when their were true regional offices for the Department of Commerce (before the Federal Radio Commission or the Federal Communications Commission), each district office had a number. Oklahoma's licenses were handled out of the New Orleans office, which was #5. You see where this is going.
- Initially, US hams got a number (corresponding to the issuing office) and then letters assigned in sequence starting at AA. When they got to WZ, they started again at AAA (because for a while, if the first letter after the number was X, Y, or Z, it had a special meaning). There was also a period when some stations, usually a portable station operated by an amateur away from his usual address, that had 4 letters after the digit.
- After one of the international radio conferences, c.1923, everyone agreed that all callsigns should start with the letters that had already been assigned, so US hams all grew Ws ahead of the digit.
- For about 40 years now, more or less, in the Amateur Radio Service, callsigns have been grouped. Amateur Extra Class licensees were assigned calls from Group A, 1x2 or 2x1 starting with W (e.g., WE5Z, W5TC) . When those ran out (and in the 5th district they ran out about 1992 or so) they "refreshed" the group with calls starting at AA5AA. Advanced Class licensees (none issued since 2000) got calls from Group B, 2x2 starting with K (e.g., KK5IO). Technicians and Generals got assigned calls from Group C, 1x3 calls starting with N (e.g., N5ZZM). Remember, until 1987, the only difference between the test or Tech and General was the Morse code, so they got calls in the same group - the written exam was the same and if you passed the 13-WPM test, you got General, if not, you got Technician. Group C was exhausted in our district about 1992 as well (N5ZZM just squeaked in!) Novices (none issued since 2000) got calls from Group D, which were 2x3 calls starting with K. Once Group C was exhausted, instead of "refreshing" it with some other pool, the FCC started pulling from Group D, which is why all new Tech and Generals get 2x3 calls.
- Now, then. When it comes to vanity calls, you are still restricted to the group that corresponds to your license class. So Technicians and Generals can get any available 1x3 callsign (starting with an N, K, or W) or any available 2x3 call (starting with WA-WZ, KA-KZ, NA-NZ, or AA-AL) with some restrictions. To get a 1x2, a 2x1, or a 2x2, you have to hold an Amateur Extra license.
Edit: Looks like Group A in the 5th District was exhausted on 1987-06-02 from looking at QRZ's 1993 database causing the FCC to start at AA5AA after WZ5Z was issued.