[Boatanchors] Enigma intercept

[Radioman390 at cs.com]

Stephen Budiansky's book, "Battle of Wits" has an image of the ULTRA (Enigma) decode of the radio message to all U-boats announcing Hitler's death "in the heroic battle for Germany in Berlin with his men."
The translation shows the actual HF frequency used, 4200 KCs.
With technology available in those days, where there other frequencies also used? The time shown is 0032 Zulu