I have 2 airplanes and I would like completely hide the communications between them.
There is a possible way that this communications would not be detected by our radio receivers around the world? Would be possible to simple hide it?
What alternative technology can be used achieve this? And why we would not detect this alternative technology?
Anyone with Telecom background? :) I found this interesting answer that can give some context: Alternatives to electromagnetism for communication?
One does not have to step outside normal rf communications technology to find ways of communication that would not be apparent. The field of encryption is replete with possibilities.
One normally thinks of encryption as a method of hiding the informational content of a message without hiding the actual existence of the message, but this is not always the case. I'll give just one of many possible examples.
Any rf reciever is plagued by noise from many possible sources including the cosmic microwave background which permeates the entire universe. It is possible to generate an rf signal that resembles noise but that is actually deterministic (the field of non-linear dynamics offers many possibilities). Suppose one designs an rf generator that can superpose an information packet on a segment of deterministic noise generated by a specific non-linear algorithm. The signal would appear to be noise to anyone with an rf receiver not designed in line with this particular algorithm.
