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