Today, Valve Software published an update to Portal through Steam. The only patch note:

• Changed radio transmission frequency to comply with federal and state spectrum management regulations

Along with this cryptic change, is a new achievement, titled "Transmission Received - .. ?", which Shacker ghost in my shell reported unlocking after he "put the radio on the red button on the first stage." At this point it "started spitting out Morse code."

We're still unsure what is actually going on here, but mysterious things appear to be afoot. At the very least, I'd recommend getting this achievement.

I've reached out to Valve Software for comment and I'll keep you updated of any new information.

Update: The following is reportedly a sound made by an in-game radio when thrown into a force field: "Dinosaur_Fizzle" noise.

Update 2: Steam users have found 26 new sound files containing around 17 minutes of Morse code. The first file has been translated to read: "interior transmission active external data line active message digest active". Something big is going on.

Gallery

Update 2: Portal has been updated with a new different ending!

Yes please. This kinda stuff is so cool.

This is way too badass. Also, it's way past time for something Episode 3 related. If it were Left 4 Dead 3 related, that would be pretty funny though. I kinda hope it's not a Portal 2 thing. I loved Portal but... I don't know.

What the christ is going on?!?!

Sound cool. Does the xbox version get an update too?

OH MY GOD!!! THE SECOND OF COMING OF JESUS THROUGH A PORTAL PORTAL SHOT THROUGH A PORTAL GUN IN THE PORTAL LAB!!!

And then it turns out to be an announcement for Portal 2. I'll be here. Laughing.

No but seriously a episode 3 announcement would be so good right about now

It's things like these why I love Valve. <3

Valve rocks for many reasons, including this one.

Portal 2 and Episode 3 tie-in announcement.

Meh.

So in the game there are hidden new radios that trigger the progress bar for the new achievement, 26 hidden radios that activates in different places..  I got two so far.

I'm scared.

Don't really want to get my hopes up....too late :(

Apparently there are pictures hidden inside of the code frequencies: 
 
 http://direct.z-95.com:8888/pics/dinosaur2bad.jpg
 
http://forums.steampowered.com/forums/showthread.php?t=1169218

" I'm scared. "

" @Vito_Raliffe said:

" I'm scared. "

Seriously. I'm staying up all night now til whatever happens happens. "

I'm pumped. I really hope this turns out to be something.

This sounds awesome.
 
Wait. Steam users know how to read morse code?

hold on to you hats, something big is going on.

" This sounds awesome.  Wait. Steam users know how to read morse code?

Sitting here in giddy anticipation.

what the hell... wat

Damn. I love reading the Steam forum, threads getting posted on trying to decode this faster then you can read them.

Spectrograms are never not cool. This is all very exciting.

"  http://babel-research.eu/ "

" Stuck on Chamber 15's second radio, anyone got it? "

Apparently that link I posted is bullshit, I think it was linked to one of those City 17 student films, sorry guys.

This an awesome idea from Valve, I hope its an announcement for episode 3.

Picture with a skull in it.  Adrian Shepard.  Confirmed.

my guess is that it is some transmission from the Borealis (a Episode 3 tease) or some new company in Portal 2 (from the website that was posted earlier    http://babel-research.eu/)

I'd love for this to be the message from Dr Mossman from the Borealis. The ship did have Apature Science crates on it.

" Picture with a skull in it.  Adrian Shepard.  Confirmed. "

" No but seriously a episode 3 announcement would be so good right about now "

HOLY SHIT! the steam forum cracked the code from the pictures, turns out it is a BBS number (ask your parents kids). Using an old dial up terminal they got a response asking for a Glados login and password.
 
What the hell Valve?

This is the most interesting marketing stunt I've ever seen.

"

" HOLY SHIT! the steam forum cracked the code from the pictures, turns out it is a BBS number (ask your parents kids). Using an old dial up terminal they got a response asking for a Glados login and password.  What the hell Valve? "

Well that made me play about a half hour of Portal. And I got one achievement so yippee. 
 
As for the hidden message, let someone else figure it out. I'll be awaiting the results.