Having valid excuses would be good if one character is trying to rationalize the whole thing. He might be delaying the eeriness for a chapter or two, building up to some more unsettling scenario.
If your on a boat and the radio goes dead you still don't wake up the entire crew (mainly because the night watch would be rather pissed at you).
You sooner think to yourself "well maybe the radios gone bad"
*check radio, it works fine*
"or maybe theres some interference"
*scan channels, nothing else broadcasting*
"or maybe..." *gets near harbor, sees mushroom cloud rising from city* "...yea, that might be it"