Many of the prefixes are historical anomalies that reflect political realities at the time of the first international radio-telegraphic convention in 1912 and the limited number of countries that participated. For example, the V series was reserved for the British Empire (V=Victoria, even though she was no longer the monarch). This is why VO
was assigned to the then Dominion of Newfoundland, but is now administered by Canada which otherwise has the prefixes CF-CK. Canada also retains VA-VG and VX
-VY from its colonial days. VR
was assigned to Hong Kong and is now administered by the PRC
The U.S. was represented by the military and thus acquired A (Army) and N (Navy). When letters were required for civilian stations, the solution was to add morse dashes to the code for A and N - thus A ( . - ) became W ( . - - ) and N ( - . ) became K ( - . - ).
I don't know why the Netherlands was assigned PA-PI and its then colonies were assigned PJ
(Antilles) and PK
-PO (Indonesia), but something in Dutch history/politics will give you the answer.
[Edited 2012-11-08 10:08:32]
Empty vessels make the most noise.