The background noise is what I have referred to as wind in the past and I have always heard it, I haven't analysed it much but I have to say that it sounds a lot like the chirping you get from the sun when you are fuel scooping very close to it.
So perhaps could be worth to give that sound a bit of attention?
Only because it is a background noise, doesn't mean that it's not important, mostly because it seems "chirping" something, and repeating it in loop.
It's the only sound that is always present, every time you listen to the UA close enough, and disappears when you step back.
So it could be just its "reactor" noise, or a kind of cooling system it has. Or not. What I'm sure of, is that it comes from the UA, not from the environment.
This is the recording I invite you to check carefully:
https://soundcloud.com/azerusrtificial/sets/ratking-plague-ua-test (from 1:30)
The sound/noise is clearly audible starting from 1:30, when Ratking15 was very close to the UA. If you listen carefully it seems to have a pattern, obvious short and long dings, and pauses between some of them. Then it starts again, always the same. And it's the same in every recording I've listen to. so it is unique.
And here is the corresponding video where you can see how that sound disappear while you go far from the UA:
http://www.twitch.tv/ratking15/c/6958384 (from 5:00)
And this one, where no station is around
http://www.twitch.tv/ratking15/c/6951497 (from 3:00)
Could be the name of some unique system or its coordinates, encoded in some way?
Please, listen. I'm talking to the MORSE/Audio/Sound specialist here.
Remember that it's the only true hint we had.