I have noticed this signal for at least 6 months. I am guessing that it is some sort of sounding transmission. The signal seems to be on 24 hours / day and I don’t see much change in signal strength. It’s kind of pleasant to listen to; reminds me of musical rain drops plinking down.
There is a period, end of one cycle to end of the next cycle, of ~4 minutes, 3 seconds. As the end of a cycle approaches, the “plinks” get stronger, shorter, and occur at an increasing rate.
I don’t think it’s a local signal and surely someone else has heard / seen it but I didn’t find anything similar when I skimmed other postings in this section. I am going to post a screenshot here that was made 11oct17 at 181105 UTC and then I will reply to myself and post an mp3 recording made on 12oct17 at 150335 UTC on; this is the last 15 seconds or so of a cycle.