The EK prefix was used for special event callsigns throughout the USSR from the early 1980s until the early 1990s.
Inspection of the Club Log QSO database, after allowing for busted calls, results in the conclusion that EK calls were not QRV from the USSR after 1992.
The first general use of the EK prefix from Armenia was in January, 1994.
There are a couple of known exceptions to the above rules:
a) EK4AA was QRV from Armenia from September 1989 to September 1992. This probably was not a special event callsign. The same operator was issued with the EK4AA call in 1998, and was QRV until 2011 or later.
b) EK7DX has been QRV from Armenia since 1992. This is the only EK callsign known to have been QRV from Armenia in 1993.
The reasons for the use of EK4AA and EK7DX before 1994 have not yet been determined.
Mapping of the EK prefix to Armenia in Club Log
The EK prefix is mapped to Armenia from 1994-01-01.
EK4AA and EK7DX operations before 1994 are mapped by callsign exceptions.
Mapping of the EK prefix in 1993
The various USSR EK prefixes are mapped up to 1992-12-31, and the Armenia EK prefix is mapped from 1994-01-01.
There is no EK prefix mapping in Club Log for the period 1993-01-01 to 1993-12-31, resulting in any EK callsigns (which are all busted) being mapped to INVALID. Note: The term INVALID in Club Log only means that the QSO is not valid for DXCC.