I would like to suggest giving the Radio towers in the game a purpose acting similar to the power and water but, it stays on a little longer due to at the start of the game having a small army force stationed at all of them. This could have a range of possibilities with the people (Npc’s) stationed there staying or deserting their post making it random on how long radio communication or at least how long far range communication continues. eventually another choice for the people still there after the exclusion zone and military break down could be to just dig in and stay near the radio towers or leaving to somewhere else. Adding military remnants scattered on the map. Also rare ham towers at houses for ham radios possibly. Also they could be used as a way to leverage power against npc groups that have a dependence on the need for radio communication.