This achievement was added on to the original list of achievements and was meant to hype up people for the release of Portal 2.
First you need to complete the main game once, then you need to replay it and will be able to find radios scattered all throughout the game where you'll have to bring to special locations to get a signal that seems to be just static.
lonerunner on Steam wrote up a awesome guide for all the locations of the radios which I for the most part used by itself. One problem is they use the map names as opposed to the testchamber numbers.
http://steamcommunity.com/sharedfiles/filedetails/?id=213131...There's also this video where someone shows where they found the all the radios and where they brought it but due to clipping it down to ten minutes they cut out where they really show where things exactly are and it did help me for like one radio but maybe you can find it more useful.
I plan to to come back to this and make a much clearer walkthrough than the stuff posted above.