England Was Almost Destroyed By Radio Waves

Coventry After Bombing — Taylor (Lt) — War Office official photographer [Public domain]

In 1940, Britain had retreated back to their island fortress after being throttled in mainland Europe by invading Nazis. They would hide behind the sea and hope that their navy and air force could stop the possible German invasion of their island.

As the Battle of Britain raged on, the German and British air forces went head to head. Something strange happened, the Germans pulled of a series of highly effective night bombing raids. It’s strange because night bombing was incredibly ineffective for the most part.

Targets were dark, all the lights were off and there were no advanced navigation or GPS devices to guide bombs. Pilots and bombers in the Royal Air Force used astrodomes. These were domes in the top of the aircraft that allowed the flight crew to see the stars. A sextant was then used to figure out where to drop the bombs.

As you can imagine, old school sailing technology wasn’t exactly that effective in precision drops of ordinance.

This German bombing was much more effective than what the British could do at night. As a matter of fact, it was more accurate than what typical bombing could do in the day time.

The British city of Coventry would bear the brunt of this highly accurate night bombing on the 14th of November. 503 tons of high explosives were dropped on the city, nearly flattening the city center. Over 500 people died and over 800 were seriously wounded. It’s estimated that 41,000 homes were destroyed as well.

Mass Grave For Coventry’s Residents — From Historic Coventry / BBC

Joseph Goebbels would go on to create a new term, coventriert, after he learned of the destruction. To Coventry something was to utterly destroy it.

Coventry was targeted because of its industrial output. 71 factories in the city were hit and damaged. If the Germans could repeat this night bombing frequently, Britain might be done for. However, the English weren’t clueless about the German’s magical night bombing abilities. They had a good idea of what the Luftwaffe was doing.


German Experience With Radio Waves & Flight

Before the War, the German aviation industry spent a lot of money on safety systems. In particular, they worked hard to develop a blind landing aid. Eventually, Johannes Plendi developed the Lorenz system.

Diagram of the Lorenz System — Anders Dahnielson wikipedia creative commons

This system of overlapping radio waves would lead a pilot to a landing strip. If the pilot went too far to the left, they’d hear “dots”, short tones followed by long spaces. Too far to the right, they’d hear “dashes”, long tones followed by short spaces. As they got to the on target towards the center, the pilot would get a continuous signal.

This system enabled German pilots to land effectively in conditions where visibility was less than optimal. It also gave the Germans an idea.

If they could use radio waves to land, could they use radio waves to mark and bomb targets?

Knickebein

Example Of A Knickebein Style Antenna — Dahnielson Wikipedia Creative Commons

The step from Lorenz to a bomb-by-radio system wasn’t that dramatic. The Germans just needed to boost the radio signal to the planes. The current Lorenz system standardly equipped on the planes would be able to receive the signal.

Now, the signal would be able to guide a bomber to a target, but how would they know when to drop their bombs? The Germans accomplished this by adding another signal. The pilot would follow the original radio beam until they heard the second and that was the “bombs away” signal.

The Germans would code name this system knickebein — “crooked leg”. The Nazis would set up these radio transmitters across Europe, aiming these signals over Britain.

German Knickebein Sites Across Europe — Dahnielson Wikipedia Creative Commons

Advances To The System

Of course if you’re German, you never stop engineering. Knickebein was just the beginning. The English were able to figure out what this system was and put countermeasures in effect to block it. Two radio beams wasn’t the toughest thing in the world to deal with.

X-Gerät, the new and improved Knickebein, used multiple beams, along with synchronized watches in the planes. This advanced system, confused the British at first. X-Gerät was the radio system used to guide the German bombers to Coventry.

This new system used advanced radio equipment within the plane. It exceeded the standard Lorenz system and all planes couldn’t feasibly be equipped with it. The Germans would use lead planes to drop initial bombs, along with flares. The following planes could drop by sight, following the flares.

The British would eventually figure this one out too, after a German plane equipped with X-Gerät crashed and was recovered. The British would throw up false radio signals similar to those the system would use, confusing the German pilots.


One Beam To Rule Them All

Obviously, the Germans wouldn’t be outdone. They had an idea for a new-new radio system to conquer England. The Y-Gerät system would make use of one beam and be much more accurate than previous systems. This single modulated radio beam would hit a transponder on the plane and then be returned to the ground station.

The ground station would then be able to calculate where the plane was by the time it took the radio beam to return. The ground station could give accurate directions to the plane on where to fly and when to release its bombs. This eliminated the planes having to follow radio signals that could be jammed or confused.

Unfortunately for the Germans, the British had a secret weapon, the British Broadcasting Corporation (BBC). Starting from September 1, 1939, the BBC television tower had been silent for the duration of the war. However, the tower at Alexandra Palace (Ally Pally) would be cranked up again. Its final transmission in 1939 was a Mickey Mouse cartoon, it would now have another purpose.

Alexandra Palace Radio Tower — Picture From Alexandra Palace Website

The tower at Ally Pally was in planning to be used as a way to jam radio signals for Nazi invasions forces if they stormed the British Isles. But an odd bit of luck would prove it could have another valuable purpose. British intelligence had found the new German system would work at 40–50MHz.

Oddly enough, that was the same frequency the tower at Ally Pally operated at. You can see where this is going already.

Under Operation Domino, the British set up a listening station at Swains Lane to listen for the German single radio beam. Once this beam was heard, the team at Swains Lane could remotely turn on the transmitter at Ally Pally. Once the German radio beam was captured, the British would create a nasty surprise when their transmitter was kicked on.

BBC sound engineers would create a “howl round” effect in the German’s radio receiving device. In other words, they could blast the German pilots with a high pitch feedback sound in their headphones, nearly blowing out their eardrums.

The British use of the BBC tower was so effective that it’s believed that no more than 25% of German planes using the Y-Gerät system ever released their bombs. The BBC was so proficient at their jamming techniques, it’s thought that it went on from February till May in 1941 before the Germans realized what the British were doing.

As the Germans attempted to change the frequencies they were using, the British just changed along with them. By the end of June, the Germans changed their focus and moved their air force to attack Russia.


Conclusion

“The BBC transmitter can claim credit for undermining a crucial part of the technology which aimed to lay waste to many of our cities”
— Kurt Barling, BBC London

For a time in WWII, England’s ability to stave off German air bombardment relied upon their skills with radio waves. This odd portion of the war, called the “battle of the beams,” would eventually be won by the BBC. Talk about an odd victor in a war.

Without the work of the BBC and other scientists supporting them, the events in Coventry might have repeated widely in cities across Britain. The blitz could have been much worse, possibly bringing Britain to its knees — maybe even shifting the final outcome of the war.

You may associate the BBC in modern times with Dr. Who or Sherlock Holmes, but in this moment of time, they were Nazi slayers. If there was ever a possible unsung hero in a war, it might be a tower whose primary mission was sending television signals, many of which involved cartoons.

The tower’s first transmission after the war was over in 1945 — Mickey Mouse of course!

Thank you for reading my ramblings, if you’ve enjoyed what you’ve read please share and tune into the BBC to celebrate.