We announced ourselves to the galaxy in 1945 to the early seventies. Nuclear explosions send a burst of gamma rays into space. An intelligent species would pick this up and know what it is. The first atomic test was in 1945. Thus our signal to the galaxy is about 79 light years. The diameter of our galaxy is about 100,000 light years.
I’d go with radio, and artificial lighting, which hit about the same time, 1870s-ish. But it’s an insignificant percentage of the Milky Way who could possibly know we’re here. And of the Milky Way is an insignificant percentage of the universe.