I'll start by saying that I live in a very restrictive building. They will not even allow us to put something above the height of the railing. Incredibly, they do not even allow Christmas lights or trees on the balcony. Admittedly, I constantly fight both restrictions. However, on the antenna side, even if they did let me, the building is HF-hateful. Every day, my building wakes up with a single purpose in life, to negate any of my attempts to send or receive an HF signal. On VHF/UHF, because I live at elevation, I am the King of the Plains. However, when it comes to HF, I have tried everything. On the balcony, outside the balcony at night when the building police are tucked away, I've tried loops, wires dangling, you name it. My noise is always at ±S9 and I just can't get a signal out or in. If I get into my car, park 100-feet away from the building and transmit, then all is good. And yes, I've tried multiple forms of grounding to no avail.
In short, I am a frustrated ham. The good news is that this experience has forced me to focus on my portable and mobile work. In fact, this very week, I am installing a 400W linear into the car!!