1/ TV stations aren't part of the SETI programme.

2/ The entire globe isn't shutting down at the same time - even if we had full international cooperation, it's between the hours of 20:00-21:00, which varies according to which time zone you're in. So only one time zone would be shut down at any one time.

3/ If an alien species were really determined to make contact then I'm sure that they would be transmitting for more than just 1 hour!