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Did Luftwaffe bombers use an interference-node counting guidance system?


Did Luftwaffe bombers use an interference-node counting guidance system?

I'm a science teacher doing a talk on storytelling in science and got some awesome crazy historical stories over on /r/physics. I'm having trouble verifying one about the guidance systems for WWII Luftwaffe bombers.

Someone reported this:

Don't give your military secrets cute code names.

One of the stranger battles of WWII was the Battle of the Beams, fought invisibly in the skies over England. German pilots relied on navigation signals sent from the European mainland to navigate and decide when and where to drop their bomb loads. Dr. R. V. Jones, director of the scientific investigation arm of British Military Intelligence (ADI Science) was tasked with understanding the system. He found the receivers hidden in normal radio equipment in shot down bombers (they were disguised for exactly this reason) and with help, figured out how the system worked. He also engineered a counter system that, rather than jamming the signal, instructed the German bombers to unload early, minimizing damage.

I've verified the above (the Knickebein system). This is the part that I can't find:

The Germans caught on and introduced a new system. This one was proving devilishly difficult to figure out. That is, until Dr. Jones was looking at Enigma traffic discussing the new system. The Germans had given it the name 'Wotan'. Jones went to ask around about the term and soon found all about the German one-eyed god. And that was enough to unravel the system.

Working from the code name, Jones deduced the nature of the system. Two beams were sent from one site, creating interference nodes along the beam's length. Radio equipment on the German bombers counted the nodes. When the correct number had been counted, bombs away. Jones began devising counters. He also began cataloging the locations for 'special' visits from RAF Mosquitoes. He also, according to some versions of the story, instructed all British code names to be drawn randomly from a pool of words. No special names were allowed.

I can't track this down anywhere, I think the user is talking about the Y-Gerat system, described on wikipedia here:

Y-Gerät used a single narrow beam pointed over the target, similar to earlier beam systems, transmitting a modulated radio signal. The system used a new piece of equipment that received the signal from the beam and immediately re-transmitted it back to the ground station. The ground station listened for the return signal and compared the phase of its modulation to the transmitted signal. This is an accurate way of measuring the transit time of the signal, and hence the distance to the aircraft. Coupled with the direction of the beam (adjusted for a maximum return signal), the bomber's position could be established with considerable accuracy. The bombers did not have to track the beam, instead the ground controllers could calculate it and then give radio instructions to the pilot to correct the flight path.

But the system isn't the same. Does anyone know if the interference node-based system the user described existed? It is such a beautiful example of the application of a simple physics principle if so. Help me /r/physics!

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