[Elecraft] Strange RFI question

[Slava Baytalskiy]

Hello everyone!
I'm not sure if this is the correct forum for this sort of a question but i figured i'd give it a shot.
I've been going out of my mind with this strange signal pattern i've been seeing on my new panadapter connected to my new K3.
I first saw it on 20 meters. It seems to be the same signal pattern, spaced evenly, at 61 kHz intervals.
Something tells me that it could very well be outside of my shack. I've got the street power lines 15 feet in front of my house, with a big transformer on top of a pole.
I just took a video of the whole thing and you can also hear the sound of it, especially while i tune it up and down.
Here's a link to the video file in my DropBox: https://dl.dropboxusercontent.com/u/111549/rfi/strange_rfi.wmv
Sorry for the format. This screen capture program only does Windows Media Video.

I've gone to a point where i've disconnected everything in the shack. Literally. And i could still hear it.
My Yaesu 857D also hears it, with the same antenna hooked up to it, so that tells me its not my K3 or the panadapter (for that matter).
I also tried hooking up another antenna (i have a home made fan dipole) and i can still hear it. So its not the antenna (right?).

I'm very open to any suggestions as to what to do? How to narrow it down?

Thanks a bunch in advance!

Slava, W2RMS

P.S. I almost wish i didn't have the panadapter, so i wouldn't even know its there... :-(