This is a very old circuit, we built it in the late 70s, high school electronics, but it was called TV Jammer. Works, but lucky to get 30 feet. Our biggest challenge was to make the smallest working version, and of course many failed attempts to boost the range. Doubt of much use any more, too many alternatives to broadcast entertainment.
Have to agree though, deliberately interfering with any signal, is illegal, regardless of power or range. Just unlikely the FCC is going to hunt you down over such a low power toy.