Hi John, The homing signals from uboat to uboat were transmitted (or supposed to be) between 350kcs and 450kcs. Various merchant ships in convoy were assigned a few kcs to monitor and in the event of hearing a signal take a bearing on it and communicate it by lamp to an escort or the Commodore. I remember going to one convoy conference prior to sailing from New York where someone played a phonograph record of a uboat. If I recall correctly it started with accented u in morse and a few letters. I listened at sea but never heard one. By the way there is a good photograph of the radio room in the u124 which you can see by going to that site. It also has a rough description of the radio gear. I found that picture interesting as u124 sank the ship I was on and itself was sunk a few hours later. 73\'s
Roy G3CAJ/AB6ND