Q Bob, KC2DT, asks, “I have recently returned to the air after a long absence. I notice that the readability report on CW is sometimes followed by NN. For example, RST 5NN. What does NN mean?”
A“NN” is simply shorthand for “99.” So, 5NN is actually 599. You’ll often hear this used during contest and DX exchanges because it is easier (and faster) to send.
From QST April 2000
