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