In Ham Radio, SK has a dual meaning. When you see it placed after a callsign, SK stands for “silent key,” signifying the operator is deceased. SK is also a CW “prosign” that means “end of contact.” It is used at the end of a QSO before the callsign.
From the ARRL’s glossary of terms: “In the Western Union company’s ‘92 code’ used even before the American Civil War, the number 30 meant ‘the end. No more.’ It also meant ‘good night’. In Landline Morse, 30 is sent didididahdit daaah, the zero being a long dash. Run the 30 together and it has the same sound as SK.”
The rich legacy of Hams is preserved in the National Silent Key Archive. The searchable digital library was established to “collect and preserve photographs, life event narratives, and data artifacts of deceased Amateur Radio operators.”
