I'm a tad late with this but here you go - "Every hour, on the hour" An excerpt from this article, and matches the periods your radio starts up at. http://www.wired.com/magazine/2011/09/ff_uvb76/all/1 I think that the radio you found must be playing the UVB-76 style messages, as Il Bandito mentioned. Maybe it's part of a UVB transmission? Anyway, it was likely in the original game as an easter egg relating to Russia but it sure as hell adds suspense! :D Also Amnesty, you're correct about the Vanilla Sky reference, as in that film parts of UVB were played in the background of that film, my favourite film :)