Here is the full list of all 23 Alt-Frequencies achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
You stayed in the time loop.
Complete chapter five.
You left the time loop.
Reveal the new voice of resistance.
Spoil Ennis' new song.
Complete chapter four part two.
Confuse Ennis with the nature of your offer.
Complete chapter four part one.
You sent Jenni's list.
You sent Kaya's list.
Learn about the Landing Plane.
Complete chapter three.
You sent the RMB-1 scoop to Talk radio.
You sent the RMB-1 scoop to Fresh FM.
You sent the RMB-1 scoop to News One.
Disturb Fred with the voice of his manager Margot.
Shame Ennis with his past.
Complete chapter two.
Have Sadie be broadcasted on another frequency.
Complete chapter one.
Ask A. None a relevant (???) question.
Suggest a cure for Michelle's flu.
Complete the tutorial.