History: Huff-Duff

While making my way through Ladislas Farago's "The Tenth Fleet", I have been truly fascinated by the ingenuity of great minds in the 1940's as well as the valor exhibited by the commercial vessels that transited the Atlantic.

One technical topic that has pages, rightfully from its importance, dedicated to it, is a product of the former mentioned above: Huff-duff, or HF-DF, or High Frequency Direction Finding.  This technology was brought to relevancy through precision by the Allies after the U-Boat Command dismissed inaccuracies at the beginning of the war as "no cause for anxiety"¹, leading to terrible COMSEC procedures which ultimately led to defeat.

The art of Huff-duffing didn't stop with the macro level outputs of the equipment, either, as is described by Ladislas Farago:

Huffduffing became an art in the hands of its British and American virtuosos.  After a while the form and nature of recurrent signals became familiar to the Allied monitors and they could add such information as "U-boats report sighting of convoy" or "U-boats going into attack," without actually breaking the German code.  Using an especially intricate method called "fingerprinting," which distinguished the touch on the Morse key of one operator from another, even the identity of given U-boats could be established.  The peculiarities of a signal transmitted on a wet aerial indicated that the U-boat had just surfaced.¹

And for your viewing pleasure, below is a video from the USS Slater museum, where a Huff-duff simulator is demonstrated and explained.  Enjoy!


References
Image: http://www.ussslater.org/tour/decks/main/emergencyradio/huffduff.html
¹ http://www.amazon.com/The-Tenth-Fleet-Phantom-Battling/dp/0931933374/