Originally Posted by Rep
Yeah, I had gotten that too during my first playthrough. I'm just going through all missions again and writing down which ones that I have found.
Level 6 - After entering the mine and dodging the minecart, you will enter a large area with a few enemies. After killing the first group, you will head to your left and fight a few more. The radio is on top of some large boxes behind one of the enemies.
Level 7 - During the middle of the mission and after killing all of the enemies while controlling the turret, you will soon come to an area where there's another tank. You will notice it, then quickly run down into a dark area with a few enemies. At the end of that small hut, you will turn right facing a few more enemies. The radio is on top of a few boxes on the left.
Adding these and level 9 that I found.