posted on Sep, 8 2013 @ 08:41 PM
The problem with this thread, well make that one of the problems, is that when does any country not have defense systems active. Rather, activity is a
level of degree (threatcon, defcon, etc.)
There is a difference between numbers stations and what the US calls EAMs (emergency action message). Numbers stations are used to communicate with
spys. EAMs are use to communicate with military personnel in a covert manner. Both are coded voice messages over shortwave, though EAMs are also
broadcast on other bands.
EAMs are often not about anything. You need to send them to keep the system going, keep the operators sharp, etc. In any one way communications
scheme, there is the problem of information assurance, i.e. you need to be sure the entity sending is the message is actually authorized to do so. So
there is an authentication built into the message. The "Hunt for Red October" shows the procedure.
The numbers stations have a long history. Go on Amazon and look up books from Keith Melton and Robert Wallace. They cover spy number stations. There
is a photograph in the book where the Soviets put a camera above the desk in the apartment of a suspected double agent and documented him using a
shortwave radio and one time pad. The US has busted a fair number of Cuban spies that used portable shortwave radios. Nothing fancy, just a Sony
world band radio.