The Gallant Hours (1960)
The scene shifts to a call between Admirals Nimitz and King. Nimitz states that Halsey is in the air and does not have coding equipment.
If Halsey did not have coding equipment on board the transport plane, the radio operator would not have been able to 'decode' the message he'd just handed to Halsey? Minimal communication was transmitted "in the clear" (i.e., not encoded). A message indicating unusual radio traffic between specific 'enemy' bases would certainly not have been transmitted in the clear.