Restricted Callsigns

Amateur radio has 4 classes of licenses issued by the FCC. These are labeled as A, B, C and D. However the FCC does have one more class, "Class X". This class does not create more callsigns. It removes some callsigns for the other four classes. In addition, the FCC has a super secret list of callsign postfixes (the letters after the number) that they will skip when auto assigning new callsigns.

"Class X" Callsigns

Please note that some of the following text was copied from the referenced web sites.
Class X does not add more callsigns. Instead it removes certain groups of callsigns from the other callsign classes (A,B,C,D) for special purposes and are not available for vanity callsigns. These are the "restricted" callsigns included in the Restricted count.
The following call signs are not available for assignment (from FCC site, click on "Vanity Call Signs" tab):
** These have not been included in any counts on this site
The following lists some of the special uses (from the ARRL newsletter 11/12/2009):
The FCC once issued call signs to hams who lived in the Caroline Islands and the Marshall Islands. Even though these entities -- former United Nations Trust Territories -- now have their own sovereignty (and DXCC prefixes), the FCC will not issue call signs in the following blocks:

You may still see some of these restricted callsigns still in use. For a period of time the FCC ULS had a bug that allowed hams to request those callsigns. This has since been fixed. Because of this the counts on this site have a number of these restricted callsigns included in several of the license statuses listed in the Call Counts section (the top section). These restricted licenses are only included in the "All" counts, never in the "Available" counts. For more information about these callsigns see the ARRL bulletin 22 ARLB022 (2004).

Super Secret List of Unassigned Callsigns

When you first get you license the FCC automatically assigns a callsign from the Sequential Call Sign System. When applying for a new callsign you can designate if you want a new callsign from this system. This will assign the next available callsign from a sequential list maintained by the FCC. Actually there isn't a list. What the FCC does is keep track of the last callsign assigned using this method. The last callsign for each callsign area and class is used to determine the next available callsign. Currently sequential callsigns are only used from Class B (2x2) and D (2X3) since Class A and C do not have any large sections of unused callsigns left.

If you look closely you may be able to detect where in the the unused callsigns the FCC is currently pulling new callsigns. If you look even closer you will notice certain callsigns are skipped. The FCC maintains a super secret list of callsign suffixes that it won't assign. Using your imagination you can most likely guess why they would skip these callsigns. If you really want one of these callsigns (wash your mouth out!!!) you might be able to request it. I don't know if they will accept it or not. My guess is they will but just in case your request gets denied you have been warned.

You may want to have some fun looking for these callsigns. Get the callsign from a new ham and try looking for similar callsigns. For example, someone you know just got their license. Say, KP4XYZ. Now search for "KP4***" (or select to search for just 2x3 callsigns with "KP4*??". Look for the holes. Do note where the available list starts listing callsigns sequentially. This will be where the FCC is currently pulling new callsigns. Have Fun!! BTW, KP4XYZ is a reserved callsign and is not available for vanity assignment. In fact all 2x3 callsigns with a suffix beginning with "X" are reserved. (See rules in previous section.)