“…you can donate one or all of your vital organs to the Aperture Science Self Esteem Fund for Girls? It’s true!”
Portal received a couple of updates this year, but I had not checked what. The ending now differs slightly (story, not gameplay). There is also a new achievement, “Transmission Received,” which is a sort of mini-game in which you take radios scattered throughout the levels to unmarked points for coded messages. You can tell that you are close because the radio starts getting static; when the light turns green, you’re there. Veteran players will notice far more radios than before in the game.
The radio in the starting chamber is one of them. Just carry it with you until you hear static. That will get you started. Do you know Morse code?