Note: Bless the radio
I don't know exactly what unlocked it eventually. I quit to the main menu and restarted the day, crafting the radio again. Then I fiddled with the stations knob repeatedly for a long time.

Note: Malik on Duty
This was one of the most frustrating ones I've encountered. I tried everything and what eventually worked for me is the following:
1. I had a backup of the save game folder %AppData%\11bitstudios\This War Of Mine on the day you receive the last transmission.
2. I finished the story.
3. I replaced iPhoneDefUser\storiessavedgames and iPhoneDefUser\storiessavedgames.alt with the backup copies.
4. I listened for the transmission again and broadcast it again.

P.S. - Diary: The Janitor unlocks when you stop the truck for a chat. Also, you can steal and give away items, but apparently you need to go the fence route.

Thanks a lot for your solution for Note: Malik on Duty. I couldn't get it to work even though I broadcasted and received all news. It's worth noting that you can use this strategy to save and restart from Day 20, and quickly get the 4 endings of Fading Embers for Epilogue: All the way.

About Note: Bless the radio, I unlocked this achievement the second day after building it. What I did was that I turned the knob both days to get information from the radio. From what I understand, it's not so much "Build a radio" as "Build a radio and use it to get information about the war".

Thanks. Actually just posted for advice on Malik on Duty. Send out all 26 transmissions but no dice. Will try your method.