Yeah, but something like that is sadly easy to locate. Radio DF gear is remarkably compact and rapid now.
Not if you are transmitting below the noise floor. See CDMA, UWB. You need a correlative receiver that is synchronized with the transmitter, and correct keys, to even see the signal.
“Yeah, but something like that is sadly easy to locate. Radio DF gear is remarkably compact and rapid now.”
I would assume then that something to find the DF gear would also be easy to produce. In the event of martial law, these become a target rich environment.