Valve has released a new patch for Portal on Steam, and the patch notes say only that it has "changed radio transmission frequency to comply with federal and state spectrum management regulations." A curious note, especially since Portal, as a computer game, doesn't actually transmit anything over the radio. That got the forum train a'moving on the Steam boards, and they eventually discovered that radios have been added to each level of the game which, when carried to the correct spots in each level, will tune in a series of coded messages. Connecting to all (or any, according to some reports) of the 26 messages in the game will supposedly unlock a new hidden achievement called "Transmission Received." At least, we think so -- as of this writing, no one seems to have unlocked it yet.
Some of the messages are morse codes that range from the technical ("External data line active") to the silly ("Beep beep beep beep"), and some are encoded images of numbers and equations ("B.dA=3"), but the whole thing appears to be hinting that AI antagonist GLaDOS may have transmitted information or part of herself out of the Aperture Science facility before the first game ended. Which would probably mean that a sequel reveal is imminent. We'll stay tuned for more information -- we didn't really expect to hear from Valve at GDC next week, but a Portal 2 reveal would make our San Francisco visit that much nicer.