The mysterious broadcast interruption of 1977

Television audio is transmitted over FM, which is subject to

https://en.wikipedia.org/wiki/Capture_effect

So it is easy to take over the audio channel of a broadcast.

(I've done it and can tell you so because the statue of limitations is expired many times over)

Assuming you're using a real TV transmitter and not just an FM transmitter tuned up on a TV channel you will wreck the picture, blow out the synchronization, etc.

You'd need to have 10x or more the power to take over the video signal.

(The thought of using a specialized FM transmitter to capture the audio seems like fun but boy do I feel like I have a lot to lose these days, including my ham radio license.)

No comment ;)

Less spectacular but highly entertaining is to take over the drive though boxes at fast food places.

Baby monitors. That can strike fear in parents and you might be able to do it with an off-the-shelf radio.

Filed under: Things that that aren't a meaningful threat to society but get government freakout anyway.

obligatory related tangent: https://en.wikipedia.org/wiki/Max_Headroom_signal_hijacking