Steve Foley wrote:
Can you picture the radar screen in Boston/New York/Chicago/LAX when all the
planes on the ground are showing up? The radar sweeps by and shows 23 planes
lines up for the departure runway, superimposed on whoever is flying
overhead.

Irrelavant. The radar computer has software that will not show any
target within the user specified distance from the radar antenna. We
set ours to 1 mile. There are also altitude filters that can be set.
There is no good reason to ever turn your transponder off or to STBY
unless ATC asks you to or you somehow know it's not working properly.