I know how frustrating it is to get just a literature reference which is not conveniently accessible. Just briefly, some comments on Lee lights and Huff-Duff.

The Lee light was a high power searchlight invented by Mr. Lee (sp) which was mounted on bombers used to hunt surfaced U-boats at night. Once the target had been picked up on radar by the plane, it would fly toward the target, turn on the light at the last moment and bomb the illuminated target. The light was needed because the radar was not accurate enough for bombing.

Huff-Duff, really HF-DF (high frequency-direction finding) was used to get a long range bearing on a short wave radio transmitter, usually on a U-boat. The Allies had a whole ring of HF-DF stations around the Atlantic and could thus get a good idea of a U-boat's location by triangulating several bearings. Once the approximate location was known, air or surface ASW assets could be dispatched to the scene to find and sink the U-boat. The German countermeasure was a high speed transmitting device based on playing a magnetic tape rapidly which was supposed to send the message out so fast that getting a bearing was not possible. Depending on the shortness of the message and the state of the art of the DF equipment, this either worked or did not.

In combination with Ultra intercepts and, of course radar and ASDIC, these methods basically wiped out the U-boat fleet late in the war. The only countermeasure was the Type XXI. Without looking them up, the losses sound about right.

Regards,
SuperKraut