Re: EM noise
Strangely enough, they can turn the lights off if they think there's a threat.
Equally warships often operate on passive detection systems only, i.e. EMCON (emissions control). So if you're an aircraft carrier, the enemy know you're there somewhere, but the idea is not to let them narrow that down to a particular grid reference they can fire missiles at.
This is why you have AWACS aircraft on your carrier as well, so you can turn the radars on only when you're a decent distance from the carrier. Also because being higher up your radars can detect things further out, that would be over the horizon for the ship.
Strangely enough the admirals do tend to have thought of this basic stuff already...
Biting the hand that feeds IT
