First of all a tree is only nature's antenna tower, spotting an antenna is easy once you know where to look. You know where to look when you have it triangulated, the FCC is no smarter than a ham on a fox hunt.
Good hip-hop? What is so good about it? Anyway the bit is it's all in the programming, acting like a moron is the easiest way to get caught and they most certainly proved it in very short order. Another way is using a crap transmitter, harmonics and spurs causing harmful interference alerted authorities to WILD, an AM pirate in my home town back in the 60s. Unlike these potty mouths the now defunct Elizabeth (NJ) Daily Journal published a parody article about having kids Dancing In The Streets, just one clever use of several popular song titles.
What do you mean by "nowadays"? Since the early days of radio it's been super easy to cobble together studio and transmitting equipment, all you need is a bit of tech savvy and junk box parts scrounged from here and there. Whaaa, da ya tink we BOUGHT r stuff dere matey? AAARRR! We izzn't just a bunch of cut throats on th' high seas, summavus gots sum smAAARRRts.
Anyways it's illegal, we had our fun and took the advice of the FCC field engineer who shut our station down after 6 years of broadcasting, we studied a bit more and got ham licenses. Heh, like a doctor once told me "We have the best drugs... and they're legal."