I'm glad to know that others are seeing this as well. I first started seeing it in 1998 for sure and possibly 1997. I thought it was coming from a nearby airport with a military base. The 10 second interval is unanimous. I am now seeing it at a location some 45 miles away from that first location. It has only done it for a couple of hours in the past few months that I am aware, but thats how it always worked. It will happen for a little while and then you won't see it again for some time.
This is CABL.com posting #119171. Tiny Link: cabl.co/mFah