Prefix

Issued Prefixes

International Allocation — Currently JA-JS, 7J-7N and 8J-8N

• J after 1912 London Conference
• JA-JM preliminarily, to which reduced, at 1920 Washington Preliminary World Conference on Electrical Communications
• JN-JZ at 1927 Washington Conference
• EK, EM-EO, ER, EU-EY, HG, HL-HM at 1938 Cairo Conference
• JA-JS to which reduced, at 1947 Atlantic City Conference
• 7J, 8J by the Secretary-General in 1958, on a provisional bases (and confirmed by 1959 Geneva Conference)
• 7K-7N, 8K-8N at 1959 Geneva Conference

From Amateurs' View Point

• JB
  First of all, under ITU's Radio Regulations, call signs are structurally same for both amateur stations and experimental ones. In 1950s, the ministry allocated JB to KDD, an international telecom carrier (now KDDI). Especially, 2×1-2×3 calls in the JB block — i.e. JB#$, JB#$$ and JB#$$$ — belonged to KDD's international experimental stations. Due to the existence of such indigenous inhabitants, the ministry had to avoid the use of JB for amateurs.
  
  Details in Japnese:
  http://motobayashi.net/callsign/untold/jb.html
  
  
• JC
  Initially, JC was allocated to coast stations by Nippon Telegraph and Telephone Public Corporation, a domestic telecom carrier (now NTT, privatized). After a while, this block became the status of "reserved," probably for unexpected future use. (Don't worry, NTT still kept JD-JE.)
  "Reserved" — that explains why. JC wasn't allocated to any services, including amateurs, for decades. With regard to amateurs, JC isn't used yet.
  
  Details in Japnese:
  http://motobayashi.net/callsign/untold/jc.html

JD is reserved for Ogasawara. Only JD1 exists, no other numbers (i.e. JD2-JD0 don't exist).
8L have never been used.
8M appeared only twice for special events:
as 8M2000 (two thousand), one of the three 2000 AD commemoration stations, and
as 8M1C, one of the ten FIFA World Cup stations.
8K appeared only once for Expo 2025 Osaka, Kansai, Japan.

Assigned Order

The Japanese call signs have been assigned in the following order post war.

• JA#AA-ZZ (two-letter suffix) — i.e. old timers

 
About 30% are still valid. Complete listing is HERE for those interested.


• JA#AAA-XZZ
  Three-letter suffix call signs were first appeared as JA1AAY, JA1ABH and JA1ABS on Apr. 9, 1954.

  (JA1AAA is on July 26, 1954.
  This "out of sequence" comes from a wide variation of the elapsed time among applicants:
  (1) "Provisional License" for a test transmission included sequentially assigned his/her FUTURE call sign, but
  (2) "Inspection" was required during his/her preparation period which can be freely defined by each applicant, and only if he/she passed this,
  (3) proper "License" was issued.)

• JH#AAA-XZZ, JR#AAA-XZZ — 'H' for 'ham', 'R' for 'radio'?
  Because the JB-block is allocated to experimental stations of KDD (now KDDI), an international telecommunication career, in a similar call sign format, JH and then JR are selected for the following some reasons:
  (1) Not assigned for Experimental Station (JG, JJ, JO, JP and JR were used for them),
  (2) Easy to key, etc.
  JH1 is issued on Oct. 17, 1966; and JR1 is allocated on Feb. 20, 1969 and issued on Sept. 29, 1969.



• JE, JF, JG, JI, JJ, JK, JL, JM, JN, JO, JP, JQ, JS — alphabetical arrangement, skipping already used JH and JR.



• Continue to "Call Sign Shortage of Japan" below.

Call Sign Shortage of Japan

Call sign shortage of Japan was due to the increasing number of amateurs especially from 1980s to 1990s. This first occurred in Area 1 (Tokyo, Yokohama), followed by Area 3 (Osaka, Kyoto, Kobe), Area 2 (Nagoya) and Area 6 (Kyushu mainland).

Transition of Total Number of Amateur Stations in JA


Increment of the Lowest Class Operator Licensees — Telephone Class (1958-1990) or 4th Class (since 1990)

1ST STAGE — Recycle

• At first, the authority 'recycled' call signs which had been expired and unused (effective on Sept. 1, 1985). The Japanese licence is due for renewal after five years, but in reality, quite a few licensees quit radio at that moment and don't renew it (or just forget to renew).
• 'Recycling' was done in Area 1 and is being done in Area 2, 3 and 6, in the following purely alphabetical order, even for initially pre-empted JH and JR:
  JE, JF, JG, JH, JI, JJ, JK, JL, JM, JN, JO, JP, JQ, JR, JS.
• But Area 1 didn't resolve the shortage perfectly — recycle caught up original.
  For example, JS1 had been first issued Dec., 1984 - Dec., 1985, and would expire Dec., 1989 - Dec., 1990.
  In addition, we need a six-month guard time after their expirations.
  So JS1 would be reusable after June, 1990.
  Unfortunately, it was Apr., 1990 when the previous recycle block JR1 ran out.
  Anyway, only about 160 JS1 call signs were available to reuse, probably which have been cancelled, or moved into another call area before their expirations.
  (Continue to SECOND STAGE below.)
  Very Few Reused JS1s, in Callbook 1991 Edition
  
  
• By the same reason, the last parts of JQ1 was not able to be recycled enough.
• This "1st" stage is Dec. 1, 1985 (JE1 started) - Apr. 23, 1990 (JS1 ran out).
• NOTE:
  • Area 6 began its recycle from JA6, and even Area 1 did its second recycle from JA1. See "JA Recycle Opened" later.
  • In Nov., 2007, Area 2 happened to skip JR2 recycle: JS2AAA-JS2AAS were mistakenly issued once following JQ2, and replaced to JS2AAA-JS2AAP soon.

Consumption of Prefixes in Area 1

2ND STAGE — 7K1-7N1

• Something more serious shortage occurred soon in Area 1 in 1990. They've got no call signs to reuse! As it is impossible to use four-letter suffixes at that time — NOTE: At WRC-03, ITU permitted a four-letter suffix for amateurs — they decided to use other prefixes.
• They started to assign 7K1, 7L1, 7M1 and 7N1 prefixes, in this order, for Area 1. But unfortunately, less than two years was necessary for these four prefixes to have gone. They only prolonged the sold out from Apr. 23, 1990 to Oct. 14, 1991.

3RD STAGE — 7K2-7N4

• So Administration made an extraordinary decision, which must be luckless for amateurs. Next they started to use 7K2, 7L2, 7M2 and 7N2, then 7K3, 7L3, 7M3, 7N3, 7K4, 7L4, 7M4 and 7N4 for Area 1.
• So PLEASE NOTE that 7K2-7N2, 7K3-7N3 and 7K4-7N4 are not for Area 2, 3 and 4, but they are all for Area 1 (Kanto-district including Tokyo and Yokohama).
• This attention-getting block is allocated on July 23, 1991; and issued Oct. 14, 1991 - June 20, 2003.

4TH STAGE — Recycle, again

• After the run out of 7K-7N series in Area 1, the second recycle — from not JE1 but JA1, see "JA Recycle Opened" below — began on June 20, 2003.
• The Area 1 case is summarized as follows:

  Original	(1952-1985):	JA1, JH1, JR1, JE1, JF1, JG1, JI1, JJ1, JK1, JL1, JM1, JN1, JO1, JP1, JQ1, JS1,
  1st Recycle	(1985-1990):	JE1, JF1, JG1, JH1, JI1, JJ1, JK1, JL1, JM1, JN1, JO1, JP1, JQ1(partially) , JR1, JS1(slightly),
  7K1-7N1	(1990-1991):	7K1, 7L1, 7M1, 7N1,
  7K2-7N4	(1991-2003):	7K2, 7L2, 7M2, 7N2, 7K3, 7L3, 7M3, 7N3, 7K4, 7L4, 7M4, 7N4,
  2nd Recycle	(since 2003):	JA1, JE1, JF1, JG1, JH1, JI1, ....

• i.e. A call sign with a prefix JE1 and after may have maximum three historical licensees. The below is an example. JE1AAT is given for (1) Mr. Matsumoto in Zama-town, and then (2) Mr. Kato in Miura-city, and currently (3) Mr. Kazama in Iruma-city.
  
  

  Historical Licensees of JE1AAT, as an Example

  Generation	Issued	Licensee	Extracted Callbook
  1st	1971		1972
  2nd	1985		1991
  3rd	2004		2006-2007

"JA" Recycle Opened

• Expired JA prefix call signs (both two and three letters suffixes) had set aside, because
  (1) to prepare — just in case — a new call sign assignment system in accord with the licensee's operator class;
  (2) to avoid the confusion that a lot of amateurs eager to change their call signs to respectable JA prefixes; and
  (3) little vacancy in JA blocks
  — the JARL had said.
  
  
• But on May 28, 1999, just before Area 6 mainland's running into the recycle, this has been changed. The authority has started to reissue JA's three-letter suffix series as well as others. So currently, newbie JA's are only heard in the Area 6 mainland (as JA6 since Aug. 10, 1999) and Area 1 (as JA1 June 20, 2003 - Dec. 17, 2004).

i.e.	Area 1	started the first recycle	with JE1	in 1985,
		and the second recycle	with JA1	in 2003,
	Area 2	started the recycle	with JE2	in 1992,
	Area 3	started the recycle	with JE3	in 1991 and
	Area 6 mainland	started the recycle	with JA6	in 1999.

Special Rules for Okinawa — Two Parts of JR6 and All of JS6

Formerly known as Ryukyu Islands (KR6 for Americans, and KR8 for the Japanese), Okinawa is a semi-tropical island group located in the south-west of Japan. It is now one of 47 prefectures of Japan since May 15, 1972. US hams in military bases may use the KA6 prefix as AMRS (Auxiliary Military Radio Station), but we are not allowed to communicate with them.

Assigned Order

Call signs (for individuals) have been assigned in the following order:

• JR6AA-NZ (fairly old timers, licenced since June 22, 1961, in the US age. Actually JR6AA-ME exist, which were changed from KR8AA-ME all together in 1972.)
• JR6QUA-XZZ (licensed after the reversion)
• JS6AAA-XZZ (Nov. 26, 1983 onwards)

JR6AAA-QQZ — NOT Okinawa

Exception — What happened for the JR6 JS6 licensees who moved between Okinawa and Kyushu Mainland

Club Stations in the US Age — KR8YAA-YAU

Special Rules for Ogasawara — All of JD1

Ogasawara is a semi-tropical small island group located about 600 miles south of Tokyo, but it is one of the parts of the Metropolis (or Prefecture) of Tokyo (i.e. Area 1). Special prefix JD1 is assigned for here in 1969, to keep status as a separated country (now "entity") even after the handover from the US in 1968.

Breach of DXCC Criteria

JD1AAA-XZZ is allocated for individuals, JD1YAA-ZZZ for clubs.

In the argument on a call area, "Ogasawara" consists of (1) strictly defined Ogasawara Is., (2) Kazan (or Iwo) Is., (3) Okino-torishima I. and (4) Minami-torishima I.

Prefix Ranking

The following table shows a ranking of prefixes as of Dec. 24, 2025, according to individual stations' call signs.