There is ZERO "reasonable expectation of privacy" (unlike most situations, the COURTS define "reasonable" for 4th amendment purposes) for wireless broadcast.
I am pretty sure you are right, and OTA (over the air) broadcast like Nellie Ohr’s HAM channel is the same even if they were using a “French resistance” model with prearranged signals triggered by seemingly innocuous phrases that decode into the real plan. Even Q codes in the HAM lexicon have their own meanings, shorthand for established phrases like “your transmission is coming in strong” or other things. There is a whole list of established ones you can find on the Internet. Also those broadcasts from her station can be taken into the web and brought back out again elsewhere but they are still monitored and he call sign (license) is mandated by the agency providing it to be able to transmit legally.
We have it all....