Doomsday Defense Topic
Navigation & Signals
Radio & Communications
NOAA weather radio, FRS/GMRS, CB and amateur (ham) radio: what each can do in an emergency and who can use it.
Field notes
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FRS and GMRS Radios: Talking When Cell Networks Fail
FRS walkie-talkies need no license; GMRS radios share the channels but allow more power and repeaters, with an FCC license. Plus NOAA weather radio.
In the library
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Visual Signaling (Signal Corps Manual No. 6)
The 1910 Army manual on signaling by flag, heliograph, lantern and semaphore, with codes and procedures for sending messages by sight.