Transmission IV is the fourth and final Transmission information service release (only available to subscribers) by British progressive rock band Porcupine Tree. It contains a complete improvisation of what would become the song "Moonloop", included on the 1995 release The Sky Moves Sideways.The 2006 reissue is an exact reproduction of the originally issued fan club edition, which was released 2001 and was limited to 500 copies. The reissue has also been remastered by Steven Wilson.