If you pay close enough attention to this blog, you probably have a pretty good guess as to who was behind the R.P.* for last night's A block.Not being among the Wilco fans who caught the reference right away, I was left to poke through the google while listening to the album (give it a few songs, it warms up), looking for a broader explanation. YHF? WTF?The short explanation is that Yankee Hotel Foxtrot is code used by spies on short wave radio.The longer explanation, told here by the Washington Post in 2004, is that spies around the world use short wave radio to communicate instructions by code and one guy became obsessed with tracking and recording these mysterious transmissions. That guy released the recordings as a collection for sale, and a sample from that collection, of a woman reading the code phrase, "Yankee Hotel Foxtrot," was used by Wilco in the song above (listen in the fourth minute), and became the name of the album containing that song.*R.P. = Rear Projection. It's the image projected on the screen behind Rachel.