Describing someone who is extremely alert, possibly but not always from caffeine or an energy drink, especially after waking up from a good night's sleep. Comes from amateur radio where the signal strength goes from 1 to 9 and anything over is rated in decibels (dB). So 20 dB over S9 is a very good signal, you're really awake.
Saul: Don't be ridiculous, there's no way you can fight this Philistine!
David: Don't worry about a thing, I'm 20 dB over S9 and slept well last night.
David: Don't worry about a thing, I'm 20 dB over S9 and slept well last night.
by Wm Wallace The Freedom Fighter December 28, 2009