No one's knowledge is less secure than your own. This idea seems to be perpetuated throughout the novel. Jack's own son Heinrich seems to grasp this idea. At the end of the section on the airborne toxic event Jack encounters a man with a television who notes that the crisis is not getting any media coverage on the television. However, most of the information that the people involved are getting is over the radio.
Radio seems to more tangible to the characters whereas television is just a distraction.
Later, we encounter the clock radio that is broken and is always on. This seems to contribute. On page 169, Jack and Murry are discussing the death of Murry's rival for an Elvis seminar. The dialogue is comical because they are more amazed that a man that large could be lost in the surf than with the fact that the man is in fact dead. Humor seems to be one of the ways that people cope with death in the novel.