Basically it depends on the radio god, have you worhipped and given tribute lately? Put your receiver on the floor, bow down facing Mecca and kiss it three times. If that doesn't help sacrificing your first born son is a sure fire hit.
Do you know what I'm saying? Basically it's out of your hands being a thing of nature. When a band is open you can receive signals on a crystal set and a wet noodle, when it's not it's not and that's that. Your local surroundings have nothing to do with it, sky waves are just that, they come down from the sky.
If all else fails try moving into a black hole, if it doesn't suck in signals I don't know what else to tell you. (;->)