Kurier was a
burst transmission
In telecommunication, a burst transmission or data burst is the broadcast of a relatively high-bandwidth transmission over a short period.
Burst transmission can be intentional, broadcasting a compressed message at a very high data signaling rate ...
system for
U-boat
U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare ro ...
communications that was first sea trialed by the
Kriegsmarine in 1943
and subsequently fitted to the
Type XXI submarine
Type XXI submarines were a class of German diesel–electric '' Elektroboot'' (German: "electric boat") submarines designed during the Second World War. One hundred and eighteen were completed, with four being combat-ready. During the war only t ...
.
Having learned of the success of the UK's
"huff-duff" systems in rapidly locating radio transmissions, Kurier was developed to dramatically reduce message transmission times from a typical 20 seconds to about 250 ms, and never longer than 450 ms (just under ½ a second). Due to the deteriorating position of Germany by that time, Kurier never became operationally effective before the war ended.
History
Prior to the opening of
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...
, the German ''
Kriegsmarine'' developed a system known as ''
kurzsignale'' for sending radio signals from
U-boat
U-boats were naval submarines operated by Germany, particularly in the First and Second World Wars. Although at times they were efficient fleet weapons against enemy naval warships, they were most effectively used in an economic warfare ro ...
s back to headquarters. At the time, it was possible to measure the bearing of a radio transmitter using a system known as a
Bellini–Tosi direction finder (B-T). A trained B-T operator could produce a reasonably accurate measurement in about a minute. To prevent this, kurzsignale encoded the message into a series of short codes that could be sent by a competent radio operator in about 20 seconds. While this could still be intercepted by a B-T operator, it would require considerable amounts of luck, and the resulting measurement would be inaccurate.
Unknown to the Kriegsmarine,
Robert Watson-Watt
Sir Robert Alexander Watson Watt (13 April 1892 – 5 December 1973) was a Scottish pioneer of radio direction finding and radar technology.
Watt began his career in radio physics with a job at the Met Office, where he began looking for accura ...
had developed a new system known as
huff-duff
High-frequency direction finding, usually known by its abbreviation HF/DF or nickname huff-duff, is a type of radio direction finder (RDF) introduced in World War II. High frequency (HF) refers to a radio band that can effectively communicate ov ...
that could take such measurements in a fraction of a second. He had originally developed the concept to allow the
Met Office to measure the fleeting signals from
lightning
Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an avera ...
, and had used it to provide thunderstorm warnings to pilots. In spite of the system being publically shown, even to the point of
newsreel
A newsreel is a form of short documentary film, containing news stories and items of topical interest, that was prevalent between the 1910s and the mid 1970s. Typically presented in a cinema, newsreels were a source of current affairs, inform ...
films of it being shown in the UK, the concept was largely ignored and development continued in secret. It is estimated that 24% of all U-boat sinkings were due in part to huff-duff intercepts.
In the spring of 1943, Dr. Bendt of
Telefunken
Telefunken was a German radio and television apparatus company, founded in Berlin in 1903, as a joint venture of Siemens & Halske and the ''Allgemeine Elektrizitäts-Gesellschaft'' (AEG) ('General electricity company').
The name "Telefunken" ap ...
came up with the Kurier concept. The first prototype was constructed under the direction of Baurat Vollmeyer, a Kriegsmarine official, and test messages were sent from
Holzkirchen in southern Germany to
Dannau, near
Oldenburg Oldenburg may also refer to:
Places
*Mount Oldenburg, Ellsworth Land, Antarctica
*Oldenburg (city), an independent city in Lower Saxony, Germany
**Oldenburg (district), a district historically in Oldenburg Free State and now in Lower Saxony
*Olde ...
on the Baltic coast. Having proved the concept, the team moved the receiver to
Bernau outside
Berlin
Berlin ( , ) is the capital and List of cities in Germany by population, largest city of Germany by both area and population. Its 3.7 million inhabitants make it the European Union's List of cities in the European Union by population within ci ...
for further testing. An improved model was available in early 1944, and tests were carried out on board a U-boat. These revealed the previously unseen problem that the electric motor driving the system, taken from a
windshield wiper
A windscreen wiper, windshield wiper, wiper blade (American English), or simply wiper, is a device used to remove rain, snow, ice, washer fluid, water, or debris from a vehicle's front window. Almost all motor vehicles, including cars, tru ...
, changed its speed based on the temperature and humidity, which were very different on a U-boat. This was addressed by replacing it with a
synchronous motor
A synchronous electric motor is an AC electric motor in which, at steady state,
the rotation of the shaft is synchronized with the frequency of the supply current; the rotation period is exactly equal to an integral number of AC cycles. Syn ...
that accurately maintained the proper speed.
[
The final version was not available until early 1945, late in the war. A total of four sets are known to have been fit to U-boats in ]Kiel
Kiel () is the capital and most populous city in the northern German state of Schleswig-Holstein, with a population of 246,243 (2021).
Kiel lies approximately north of Hamburg. Due to its geographic location in the southeast of the Jutland ...
. By this time the Soviet
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nation ...
forces had reached Kuestrin and Bernau was evacuated. A new receiver station was set up on 27 April in Bokel, north of Hamburg
(male), (female) en, Hamburger(s),
Hamburgian(s)
, timezone1 = Central (CET)
, utc_offset1 = +1
, timezone1_DST = Central (CEST)
, utc_offset1_DST = +2
, postal ...
.[ The war ended days later.
]
Description
Sending a message using Kurier started as before, the message was prepared using the Navy's '' kurzsignale'' encoding method that reduced messages to a short series of four-letter codes, and then encrypted using the Naval Enigma machine. Conventional transmission of the ''kurzsignale'' would then continue in Morse code.
Kurier was a simple system largely consisting of the KZG 44/2, the "Gerber". The main component was an aluminium disk with 85 small iron bars along the outer edge, connected on a small hinge that allowed them to be rotated flat along the edge of the disk or at an angle out from it. The kurzsignale Morse code was entered onto the disk by encoding dots with one bar pushed in and dashes with two adjacent bars. There was a gap between the bars equal to three times the length of the bar. After one entire letter was encoded, one position was skipped to produce a longer pause and indicate the end of the letter. The first 25 bars on the disk were always set to the dot pattern, to provide a timing signal, followed by another five unset positions.
Once the message was encoded onto the disk, it was connected to the radio and activated. The system had a magnetic transducer
A transducer is a device that converts energy from one form to another. Usually a transducer converts a signal in one form of energy to a signal in another.
Transducers are often employed at the boundaries of automation, measurement, and cont ...
similar to a tape head
A tape head is a type of transducer used in tape recorders to convert electrical signals to magnetic fluctuations and vice versa. They can also be used to read credit/debit/gift cards because the strip of magnetic tape on the back of a credit card ...
positioned over the outer edge of the disk over the bars. The disk was motorized to spin when activated. As any of the pushed-in bars passed the transducer, a small electrical current was induced. This was then filtered and amplified before being sent to the radio, producing an output otherwise identical to a telegraph key
A telegraph key is a specialized electrical switch used by a trained operator to transmit text messages in Morse code in a telegraphy system. Keys are used in all forms of electrical telegraph systems, including landline (also called wire) ...
being used to send Morse. A small box allowed adjustment so that the output of the Gerber would match the inputs of the radio found in that U-boat. The motion was timed so that each bar produced a 1 ms long signal followed by a 3 ms pause. The result was a 250 Hz signal with a duty cycle of 25%.[ The longest possible message was thus 97 (timing pulses) + 20 (pause) + 337 (dots and dashes) = 454 ms, less than half a second.
The signal was received at ground stations equipped with three Philips CR101 radio receivers connected to their own antennas and output to a small oscilloscope. The antennas were positioned about apart so that at least one of them was always able to receive the signal even in the presence of fading. A ]thyratron
A thyratron is a type of gas-filled tube used as a high-power electrical switch and controlled rectifier. Thyratrons can handle much greater currents than similar hard-vacuum tubes. Electron multiplication occurs when the gas becomes ionized, p ...
was used to trigger the oscilloscope's brightness channel when the signal was received, and the horizontal scanning rate set so that the complete signal was about the width of the display. The oscilloscope's brightness was normally set low so that the trace was not visible, and when a signal came in, it brightened up to visibility. A camera
A camera is an optical instrument that can capture an image. Most cameras can capture 2D images, with some more advanced models being able to capture 3D images. At a basic level, most cameras consist of sealed boxes (the camera body), with a ...
was positioned in front of the display, capturing the signal in a photograph. The photograph was removed and developed for reading. The thyratron had to be reset before another signal could be received, ensuring the photograph captured only one burst.[
]
Notes
References
{{reflist
Radio communications
History of telecommunications in Germany