Call Sign Variations

New hams listening in on a repeater are likely to hear a wide variety of call signs.  They may be confused and question some of them.  Repeaters near an international border can get pretty interesting with call sign variations in both countries.   EchoLink and IRLP open many repeaters up to access from anywhere the internet can reach.  Call sign variations are even more evident on HF bands where communication distances can be much greater.  New ham KG5XYZ may wonder why not everybody else is a KG5 like them.

It is important for new hams to be familiar with call sign variations and legal call signs for logging, message handling and just scribbling down a call sign when communicating with another ham.  “Did I just hear KMG365?” Comment if you get this reference. 🙂


First it is essential to understand that ham radio call signs (AKA call letters or just plain call) have a prefix followed by a numeric digit followed by a suffix.  The prefix is determined by the country in which the license is granted, most always one or two alphabetic letters. The digit following the prefix has significance within individual countries, such as geographic zones.  The alphabetic suffix following the number is generally meaningless other than to distinguish between calls sharing the same prefix and number.

There are variations in prefixes, not only by country but often also in number of alpha characters.  The number in a call sign is almost always a single digit.  The suffix may legally be anywhere from one to five alpha characters, depending on governing authority.

This arrangement of prefix-number-suffix is referred to as its format and is useful for describing a call sign. The format system counts the number of characters in both the prefix and the suffix.  It is usually termed the “p by s” system or pxs in writing where p represents the number of characters in the prefix and s is the number of suffix characters.  Using USA example call signs, W3MRC is a 1×3 call while KF5ZFD is a 2×3.  KL7AA and AF5NP are both 2×2 call signs.  NA6M is a 2×1 and W1AW is a 1×2.  One by three (1×3) and two by three (2×3) are by far the most common call formats in the US, followed by 2×2 and then 1×2 and 2×1.  Because they are relatively uncommon, even seasoned hams sometimes pause at a 2×1 call to register with their brain as legitimate.

1×1 call signs are legal in the US but are assigned only to organizations for special events and only for a limited time.  Details on special event call signs can be found at this FCC site.


Valid prefixes in the USA are K, N, and W (one letter),  and AA-AL, KA-KZ, NA-NZ, and WA-WZ (two letters).  Complete details can be found here.

Below is a small sample of international prefixes a US ham might run across, mainly on HF bands: Continue reading