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©2004-2022 F. Dörenberg, unless stated otherwise. All rights reserved worldwide. No part of this publication may be used without permission from the author.

Latest page updates: June-December 2022 (made into separate page; added ref. 210C; added section with info + images + references for all Kn stations)

Previous updates: January 2022 (inserted section on bombing); December 2021 (added ref. 230Q5, 230Q6, 230R13); 28 May 2021 (note: now about 800 literature references provided on the WW2 Rad Nav pages, almost all downloadable!); April 2020 (started complete overhaul & expansion of this page).

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Knickebein Large and Small

Fig. 0: The antenna systems of the Large and Small Knickebein - approximately to scale

(source: adapted from p. 9 in ref. 261L (Large Kn) and Fig. 37 in ref. 181 (Small Kn)

Early 1939, the Luftwaffe Signal Corps was instructed to build five rotatable VHF long-range radio navigation beacons ("Fernfunkfeuer drehbar", FFuFd) as soon as possible (ref. 230Q8):

  • Three high-power narrow-beam beacons, procured from the Telefunken company:
  • Range up to 1200 km - depending on altitude and the sensitivity & selectivity of the radio receivers.
  • High-power: 3 kW transmitter output.
  • These beacons were given the code name "Knickebein" (Kn). This translates into English as "crooked leg", or "knock-knees". Both are popular names for a medical condition called "angular limb deformity" (ALD). Another common translation is "dog leg". However, personnaly, I have never seen a dog lift a hind leg up about 165 degrees to urinate, at least not without first going to ballet school. The German code name simply refers to the "Knickung" ( = sharp bend, angular offset) between the left-hand and right-hand half of the antenna system, when looking down on it. So, it does not refer to a 19th century German fairy tale character (but who may have suffered from ALD). In English documents, it is persistently stated that the name refers to some "legendary raven of German mythology, with the ability see over long distances". However, there actually appears to be no trace of this in German mythology. Ravens are, however, common in Norse and Celtic mythology - but none were known for their optical farsightedness...
  • Two lower-power wider-beam beacons, procured from the Lorenz A.G. company:
  • Range of 300-600 km.
  • Using the standard 500 W Lorenz landing beam beacon transmitter model "Anflugführungssender 4" (AS 4). It had a power consumption of 5 kW and a tone modulation frequency of 1150 Hz. Note: this is the same transmitter that was later also used in the FuSAn 724 "Bernhard" beacon ground stations.
  • These beacons had the code name "Karussel".

The purpose of these beacons was "to facilitate long-range navigation of Luftwaffe aircraft operations over the North Sea", "to define specific approach and return paths" and "to delimit dangerous and neutral areas" (ref. 230Q8).

The general requirements for these beacon systems were (ref. 230Q8):

  • A guide beam system based on the civil 1932/33 Lorenz landing beacon system concept of Ernst Kramar. I.e., creating a narrow "equisignal" radio beam with two overlapping beams with interlocked Morse code "E" (= "dot ", "•") and "T" ( = "dash", "─") on-off keying. Tone frequency: 1000 Hz. Initially, tone frequencies of 1250 and 1850 Hz were considered (ref. 230Q7). However, they would have provided no advantage over standard landing beam tone frequency.
  • A guide beam (equi-signal beam) width of 0.2° (later to be improved to 0.1°), i.e., about 1/10 the width of the standard Lorenz landing beam system a that time.
  • Unrestricted interception and tracking of the "dots" and "dashes" sub-beams within ±12° of the center of the narrow equisignal beam. "Dot-only" and "dash-only" reception out to ±45° (±40° per ref. 230Q7).
  • Specific distance along the guide beam ( = target position) to be marked with a crossing beam from a second equisignal beam beacon station.
  • Antenna system ( = guide beam direction) to be adjustable/rotable over a range of ±45° (up to ±90° in exceptional cases) with respect to a predetermined central pointing direction.
  • Ground station to include a transmission-monitoring receiver, and cabling between that remote receiver and the transmitter station.
  • All beacons to be compatible with the Lorenz military Funklande Empfangsanlage Fu Bl 1 ("blind approach & landing receiver system"). This was standard equipment in Luftwaffe aircraft. It covered over 30 channels in the 30.0-31.5 MHz range, plus 33.33 MHz (ref. 32, 230Q5). No modifications to this receiver system should be required.
  • The first station of each beacon type was to be operational by mid-October 1939. The second station of each type by mid-November 1939. Note: the order dates from 10 September 1939! This implies that the Telefunken and Lorenz designs had already been completed at that time, and parts procured or manufactured...

Obviuously, there were also equirements regarding the location of the beacon (ref. 230Q8):

  • Unobstructed view of at least 1.5 km (≈1 mile) within the range of rotation, with 10° margin. I.e, within ±55° of the central pointing direction.
  • No terrain bumps higher than 4m (≈13 ft) within that range of rotation. If unavoidable, the antenna system has to be raised accordingly.
  • The terrain at the beacon site has to be flat to within ±1 m (≈3.3 ft).
  • The terrain at the beacon site has to support the 200 metric ton weight of the rotable antenna structure, without causing the concrete ring and track to tilt more than 2 cm (≈¾ inch).
  • Unobstructed view to defined reception control points at 1 km from the antenna, and preferably to the horizon beyond it.
  • No construction within a safety zone of 150 m (500 ft) from the antenna system. Transmitter barrack to be placed outside the range of rotation (in front & back direction)
  • Inside the range of rotation (with 10° margin), reflecting objects are to be avoided . E.g., houses taller than 4 m, wire fences, aircraft hangars, steel towers, low & high voltage power lines, etc.

The Telefunken company had already been tasked early 1939 to develop a simple beam system that was compatible with the Lorenz Funklande Empfangsanlage Fu Bl 1 ("blind approach & landing receiver system") that was standard equipment in Luftwaffe aircraft (ref. 32, 230Q5). The receivers of this set had much higher sensitivity than required for operation with a landing beacon. This enabled their use for long-range navigation. This new Telefunken system was also an E/T beam system, and also used two crossing marker-beam beacons. Telefunken's very rapid development was headed by Adalbert Lohmann, who was later also in charge of the development of the Bernhard/Bernhardine system. The new system operated in the 30-33.3 MHz band, i.e., a wavelength of 9 - 10 m. Obtaining a sufficiently narrow equi-signal beam at these frequencies required an antenna system with two large dipole arrays. The designator for the ground stations of this directional-beam system ("Richtfunkfeuer") was Funk-Sende-Anlage ("radio transmitter installation") FuSAn 721.

The location of the three Knickbein stations and the two Karussel stations was also specified, including their central pointing direction. Pairwise, the three Knickebein stations could provide crossing beams over any target point in Great Britain [note: Great Britain is not the same as the United Kingdom or the British Isles]:

Knickebein locations

Fig. 1: Location and beam-pointing direction ranges of the initial Knickebein stations and the Karussel stations

(source: adapted from ref. ref. 230Q8; the map was drawn September 1939)

By the end of 1939, two of the three Knickebein installations were operational along the western border of Germany. One was on Stollberg hill near Bredstedt - on the North Sea coast in the far north of Germany. This station was later named Kn-2. The second station was at Kleve, where the river Rhine crosses the eastern border of The Netherlands. This is the German town that is closest to London and the Midlands. This station was later named Kn-4. The third station was initially constructed on the southern edge of the Frisian isle of Borkum, off the North Sea coast in the northwest of Germany. This is right on the northermost border of The Netherlands,and, therefore also relatively close to Britain. It is unclear if construction of the station on Borkum was ever completed, and what its exact location was - allegedly south of the only surviving brick building of the installation, see here (Google Maps link). During the winter of 1939/1940, the Borkum station was moved to the village of Maulburg, in the far southwest of Germany, near the German/Swiss/French border. This became station Kn-12. See ref. 230Q7, 230Q8. The most likely reason for this relocation, is that the Borkum station was roughly half-way between Stollberg and Kleve, and too close to both. This means that the Borkum beam could not cross the beam of those other stations at a large enough angle to accurately identify bombing targets throughout Britain. Of course, this should not have come as a surprise... These three stations in Germany were the large Knickebein version ("Großanlage", "große Bauform").

After the invasion of their neighbor countries, the Germans installed another nine Knickebein stations along the coasts of southern Norway (1x), The Netherlands (2x), and France (6x, from the Channel coast down to Brittany). Construction of station Kn-13 on the isle of Sicily/Italy was advanced, but never completed. These were Small Knickebein systems ("kleine Bauform", "Kleinanlage"): about a quarter of the size of the Large Knickebein.

TO BE ADDED/EXPANDED. Kn = simplified "X-System" (developed 1934, which was in practice too complicated beceause...?), could be considered as two long-range, high-accuracy, Lorenz landing beam systems (see below). Claims - by then - frequently not very usable over North Sea, due to British radio interference; crossing point of eg K3 and K4 used to release bombs, or as waypoint to an other target. Note: internal memo ( = ref. 230xxx) of the "Seekriegsleitung" ("Maritime Warfare Command", here 1.Skl to 2.Skl). Wotan.

TO BE ADDED/EXPANDED. Ref. 230Q19, other... : Kn used through October 1940; due to ineffectiveness, not used during the bombing raids on Coventry (major center of war production), ("Coventry Blitz"), on 14 November 1940 - a clear, moonlit night - no need for "blind" navigation guidance. Contrary to Allied propaganda, and general copy-and-paste publications, and - terefore - popular belief.

TO BE ADDED/EXPANDED. Note: some documents and publications use the letter "K" for Knickebein stations. I use "Kn", as this is consistenly used on Luftwaffe/Luftnachrichten maps (ref. 210A - 210AD).

TO BE ADDED/EXPANDED. Ref. 181 (p. 71; 1942): "Mechanically, the construction of the [small] Knickebein installations was a good exercise for the construction of the "Bernhard" station antenna system, as it encouraged designers to use a steel construction of size similar to the Knickebein, but for continuous rotation."

TO BE ADDED/EXPANDED. Around September of 1941,  the radio equipment of German aircraft transitioned from the EBl 1 receiver to the EBl 3. The latter did not have a simple switch for toggling between two pre-set frequencies. So, manually re-tuning was required to switch back & forth when (near)simultaneously tracking two radio navigation beacons such as "Knickebein" or "Bernhard". Quite a nuisance, and not at all conducive to accurately navigating to a target location!


The construction diagrams in the next three Figures are based on ref. 230Q8. This original 1939 German document was first published on this web page! It has construction diagrams with the official dimensions. Most values given in general publications are several meters different and without source reference. The rotable structure weighed about 200 metric tons (≈442000 lbs), ref. 230Q8. It spanned 99 m across (≈325 ft), had a height of 29 m (≈95 ft). The span is slightly larger than the length of a standard international soccer field or a US football field.

Knickebein large

Fig. 2: Front view, top view, and cross-sectional view of the Knickebein structure

(source: adapted from ref. 230Q8, 1 September 1939)

The system could be rotated in order to aim the guide-beam at a particular bombing target in Britain. The rotable structure had six sets of steel wheels: two sets underneath small outriggers below the vertical truss on the far left hand end, two on the far right hand, and two sets below long outriggers in the center. See just below cut A-B and C-D in Fig. 2 above. The wheels rolled on two circular steel rails. The outer rail circle had a diameter of 93 m (≈305 ft), the inner one of 17.6 m (≈58 tf). The antenna system could be rotated +/- 45° with respect to a central beam-pointing direction. Rotation was done with two winches: one on the front side and one on the rear side of the antenna system, just outside the large circular track. The winches pulled on a cable via a diversion pulley. Per ref. 2C3, the winches were powered electrically.

Knickebein large

Fig. 3: Top view of the Knickebein system

(source: adapted from ref. 230Q8, 1 September 1939)

Note that the large steel truss box frame is completely straight! Ref. 230Q8 (1939) specified that the left-hand and right-hand dipole arrays of the first three Knickebein stations (i.e., the Large type) were to have a 5° offset. I.e., a 175° V-angle when looking down on the structure. The construction drawings in the same reference (see Fig. 3 above) show that the dipole antenna arrays measured 35 m (≈115 ft) across. The dipoles were suspended from a horizontal steel cable that was strung between the outer and central vertical truss pylons. These pylons had a width of 5 m and were spaced by 45 m. This suggests a maximum achievable angular offset of ≈ 2 x 6.3°. See diagram A in Fig. 5 below. This is close to the commonly assumed 7.5°, i.e., a V-angle of 180 - (2x7.5) = 165°.

However, this angle is only possible if there is a single vertical plane of dipoles in each half of the antenna system. Fig. 4 below clearly shows two dipole planes per side: a front and a rear stacked-dipole array.

Knickebein large

Fig. 4: The Large Knickebein Kn-2 at Bredstedt/Germany - with a total of 64 vertical dipol antennas

(source: p. 9 in ref. 261L)

Front and rear of such a configuration are typically spaced by 1/4 of the wavelength. At a frequency around 30 MHz, that would be ≈ 1/4 x 10 m = 2½ m. This is consistent with the 2½ m dimension marked in the cut E-F in Fig. 2 above (also from ref. 230Q8). This reduces the maximum achievable left-right offset to ≈ 2x 3.2° = 6.4°. I.e., a minimum V-angle of 180 - 6.4 ≈173°. This is significantly larger than 165°. See diagram B in Fig. 5 below. The actual angle on the left-hand side is easy to see at the top left-hand corner of the dipole array of Knickebein Kn-2 at Bredstedt/Germany, Fig. 4 above.

Knickebein large

Fig. 5: Minimum possible V-angle between the left- and right-hand dipole arrays - without & with outriggers

(source: diagrams adapted from ref. 230Q8, 1 September 1939; photo: taken standing on the bottom truss of Kn-4 at Kleve)

Purportedly, the photo above was taken at Knickebein Kn-4 at Kleve/Germany. It clearly shows that at this station, outriggers were used to decrease the V-angle by about 12° to about 161°. See diagram C in Fig. 5 above.

As stated above, the large antenna superstructure could be rotated on two concentric circular tracks. See Fig. 2 and 3 above, and Figure 6 below. The outer concrete ring was 1.1 m wide (≈3.6 ft; measured at Kn-12, ref. 230Q1). I.e., just like the ring of the Small Knickebein! The width of the inner concrete ring is not known (to me). Unfortunately, the best photo available to me of the intact Large Knickebein track and rail is not particularly good:

Knickebein large

Fig. 6: Outer and inner concrete ring and rail of Large Knickebein Kn-2

(source: adapted from Fig. 36 in ref. 181 of 1942)

The photo suggests that, at least at Kn-2, the wheels of the rotating antenna system rode on a circular steel I-beam rail, and that the rail was neither embedded into the concrete ring, nor clamped onto wooden cross-ties laid across the ring. I.e., the bottom flange rested directly on the concrete, and was clamped down onto steel plates anchored in the ring.

TO BE ADDED: At Kn-12: about 0.9 m (3 ft) high (above ground), ref.?? 

TO BE ADDED: CH aerial photo of Kn-12, showing remnant of concrete support block at the center of the concrete ring. Photometrically: block 2x2 m (≈6.6 ft), vs 1.4 for Small Kn (link). TO BE ADDED: At least not at remaining ring of Kn-12: I-beam rail not embedded in concrete. No sign of fasteners in concrete ring  Suggest I-beam attached to wooden ties, simply sitting on the concret ring. Kn-12 ring shows evenly spaced shallow furrows in a separate top layer of concrete ring. They are dimensioned such that they would fit such raill ties (and keep them from moving around). REFER TO SMALL KN SECTIONS FOR BLOCK, TRACK.

Hein Lehmann logo

The antenna system of the Large Knickebein at Kleve ( = Kn-4) and the one "near Basel" (Switzerland), i.e., at Lörrach/Maulburg in Germany ( = Kn-12, moved there from Borkum isle) were manufactured and installed by a company in Berlin. Ref. 230Q21. No doubt, the third Large Knickebein, at Bredstedt ( = Kn-2), was as well. Most likely, it was the Hein, Lehmann & Co., Eisenkonstruktionen, Brücken- und Signalbau company (HL Co.). They were the standard antenna construction subcontractor of the Telefunken company, in particular of the Telefunken radio communication & navigation department ("Abt. Funknachrichten und Navigation"). It would make sense that the Small Knickebein structures were also made by HL Co. The HL company was founded in 1878 in Berlin-Reinickendorf by businessman Max Hein and engineer Anton Lehmann. It was founded as a factory of corrugated iron sheet (regular "Wellblech" and load-carrying "Trägerwellblech"). It added production of railway signalling systems in 1885, and incorporated in 1888 as Hein, Lehmann und Co. Aktiengesellschaft. They relocated to Düsseldorf-Oberbilk in 1889. Over the years, they expanded into steel constructions such as hangars for "Zeppelin" dirigibles, large bridges, and large antenna systems. Ref. 140. The company had an antenna construction department ("Abt. Funkbau"). They did design the construction of antenna masts and antenna turntables. Ref. 177A. It is highly unlikely that they also designed the type and dimensions of the actual antenna elements, as this requires very specialized radio-frequency knowledge. The antenna related activites of HL Co. resumed in 1946 in Berlin-Tempelhof and resided their until 1956. A small part of HL Co. is still in the metal products industry to this day.

Hein Lehmann logo

Fig. 7: Hein, Lehmann & Co. entries in the Berliner Stadtadressbuch / Branchen Adressbuch of 1946-1956

(source: Berlin Address Directories 1799-1970; entries for "Brückenbau" & "Funkturmbauten" = bridge & transmitter-tower construction)

As mentioned, HL constructed and installed (very) large antenna masts and towers ("Funkmaste, Funktürme"). One example is the famous Funkturm radio broadcast tower in Berlin-Charlottenburg. It was designed in 1924 by HL (except for the observation & restaurant decks, designed by H. Straumer) and construction finished in 1926. It was used for VHF TV broadcasts starting in 1929. It is still standing tall (147 m) to this date. HL presented the Messegesellschaft Berlin a bill for 203660 Reichsmark on 25 June 1926 (Kom.Nr. 431/24). This is equivalent to about €1.7 million in 2022 (ref. 177A/177B). Many other large antennas for shortwave and longwave transmitters were built by HL around the world, e.g., at Nauen/Germany ("Großfunkstation", 1906, 200 m tall), Pennant Hills/Sidney/Australia (1911, 120 m), Kootwijk/The Netherlands (1919, 1929; 210-266 m), Bandung/Indonesia, Annapolis/MD/USA (1919; US Navy), and Lahti/Finland (1927, 150 m tall). Also the huge antennas of the gigantic 1 megawatt Goliath VLF transmitter station of the Kriegsmarine and the large antenna system of the "Bernhard" rotating beam beacon system (≈28 x 35 m (HxW, 92x115 ft).

Hein Lehmann antennas

Fig. 8: Some examples of large broadcast antenna towers built by Hein, Lehmann & Co.


The 1939 specification for the Large Knickebein short-wave transmitter calls for an output power of 3 kW, and an associated power consumption of 20 kW. The latter was intended to be increased to 100 kW at some later date - possibly suggesting a similar 5x increase in transmitter power. Ref. 230Q8.

As the Knickebein was a Telefunken development, the transmitter was probably a Telefunken model as well.

Ref. 230Q28, 230Q29, 230Q30.

If you have any information about the 3 kW transmitter or any associated equipment, please contact me!

I also have no information about how the output of the single transmitter was toggled between the left-hand and right-hand half of the antenna system. Given that the Large and Small Knickebein were to great extent developed in parallel, there is no reason to assume that the switching scheme was different from that of the Small Knickebein - which was integral part of the latter's transmitter: the standard Telefunken AS 4 500 watt Lorenz landing beam beacon transmitter.


Performance of the beam system by itself, in terms of actual and specc'd

  • Usable range/altitude volume
  • Equisignal beam width - see discussion below on "perceived"


Fig. 9 "Knickebein" minimum and maximum aircraft altitude for sufficient beam signal reception vs. range

(source: adapted from ref. ref. 230Q7, dated May 1940; altitude limits are average values)

In the above graph, the shape of the useable altitude-vs-range region corresponds to the shape of the antenna system's radiation paterns. Ref. 230Q8 (Appendix 2) has actual long-term range measurements from July of 1939, made over open water, at an altitude of 4000 m (≈13k feet), with three radio configurations: 1) standard FuBl 1, 2) FuBL 1 with increased selectivity, and 3) an unspecified special receiver. Each receiver was tested with two antenna configurations: rod antenna, and trailing wire antenna. For the six radio/antenna combinations, average ranges varied from 400 to 1000 km (≈250-620 miles). Minimum and maximum observed ranges were 20% lower and higher, respectively. The ranges were expected to depend on air temperature and humidity, as well as seasonal radio propagation conditions.

The actual width of the Knickebein equisignal beam is generally stated as being 0.3° (see, e.g., the graph above). I.e., not the 0.2° of the original requirement stated above. But, of course, a requirement that does not state applicable conditions and definitions, is rather poor, to say the least - and entirely unacceptable by modern day aviation standards. Clearly, the perceived beam width (always remember - "perception is the truth!"), is affected by several major factors:

  • Ambient noise at the position of the radio operator or pilot, who listened to the beacon signals with a headset and interpreted the signals.
  • Broadband Radio Frequency Interference (RFI), both radiated and conducted.
  • Radio operator practice, experience, and concentration. The auditory cortex of the human brain has "audio filter" functionality that can be trained to focus on an aural bandwidth as narrow as 50-100 Hz! This frequency selectivity improves the discrimination between the target tone and so-called masker noise.
  • Radio operator age: the auditory discrimination ability and accuracy of human hearing gradually and continually decline with age, starting shortly after birth. It also depends on heredity.

Within the fuselage of airplanes of that era, very high noise levels existed due to spinning propellers (prop wash pulses pound the fuselage!), noise from running engines and engine exhausts, the effects of the slipstream on the thin walls of the fuselage, and vibrations in general. These effects depend on the aircraft type, engine type, airspeed, etc.

Broadband RFI is caused by build-up of static electrical charge (as much as 100 - 200 kV), and discharge thereof. The build-up is caused by friction between the air and the airplane in flight. Discharges take the form of arcing, corona, and streamering (no, not streaming!). Another form is "precipitation static". This is caused by particulates in the atmosphere that strike the aircraft surfaces - in particular radio antennas. Examples of such particulates are rain drops, snow, ice crystals, dust, volcanic ash, and ionized particles in the engine exhaust. Other sources of "static" are proximity to electrically charged clouds, and penetration of thunderstorms with electrical activity (lightning). Poor connections in the aircraft wiring, in particular power and ground/earth, cause both conducted noise and RFI. Finally, willful radio interference by the enemy can be broadband noise, and frequency specific narrow-band noise and/or specific waveforms. Not only can RFI overwhelm and distort the received signals of interest, they can also cause the radio receiver's Automatic Gain Control (AGC) to de-sensitize the receiver!

EXPAND/UPDATE/ADD: Human ear, fly not on the center of the beam but right on the edge, where it is easier to detect deviation (ref. ADIK???); 0.2-0.3 dB - but only in absence of background noise. UKW Fernfunkfeuer - VHF Long-Range Beacon. -------- Note that the "edge" of the equisignal beam is determined by the air crew's ability to distinguish between a constant tone, and a tone ever so slightly dominated by either the dot or dash component of the equisignal.  ---- The characteristics of human hearing acuity (intensity at which a tone is just audible) led experienced crews tTracking the beam on either edge of the equisignal beam, rather than constantly meandering between the left & right limit of that beam. Need ref! Tracking equisignal = flat max.

Note that "determining" position or direction is actually "estimating", based on measurements or observations. Estimations always have an "accuracy" and a "precision". These terms are often confused, and even used interchangeably - which they are not! Simply put, "accuracy" expresses how close estimates are to the true value. "Precision" expresses how close multiple estimates of the same true value are to each other, i.e., "repeatability".

Note that with a single RDF-beam beacon, only a direction ( = bearing angle) can be determined - not position. The result is basically a continuous straight (or great-circle) line of possible positions, emanating from the position of the beacon station, through the mobile receiver station (here: the aircraft antenna), and beyond. This is a linear Line of Position (LoP, a.k.a., "position line"; D: "Standlinie"). See the left-hand panel of Figure 10 below.

Important: without further information, the receiver's position on an LoP is not known! For a given position of the beacon transmitter station, the LoP can be drawn on a map ("chart" in navigation parlance). Note that the bearing from a ground station to the aircraft (or vice versa) should not be confused with the aircraft's heading ( = the way the nose is pointing), nor with the aircraft's course ( = direction of the ground track, which is affected by wind).

intersecting LoP's

Fig. 10: The effect of Linear LoP crossing angle on the uncertainty of a trilateration position estimate

(note: distance from Station A and from B to the LoP-intersection is the same in all three cases, as is the "beam" aperture)

EXPAND/UPDATE/ADD: Ref. 230Q6 (October 1940): claims accuracy 2 km over London, instead of the typ. published value of 150 m over target in England (also see handwritten note in the margin to that effect); Per the graph above (Fig. XX): Kleve-London = 432 km --> @ 0.3° beamwidth = 2¼ km, Stollberg-London = 688 km @ 0.3° = 3.6 km; Lörrach-London = 713 km @ 0.3° = 3.7 km.

EXPAND/UPDATE/ADD: Resulting bombing accuracy (combo of 2 beacons, beams crossing, also see error graph in RadNav page): delay in decision that a/c at beam crossing point + actuating bomb release + MANY other factors that are discussed in the "bomb trajectory" section of the "“Blind” aerial bombing" page.

Predicting the real point-mass trajectory of a released bomb is very far from trivial. The following are primary factors that affect this trajectory, and the resulting "target miss distance" (a.k.a. "stores delivery accuracy"):

  • Bomb release altitude.
  • Aircraft conditions in terms of position (altitude error) and motion (angle, rate, and acceleration of pitch, roll, and yaw; airspeed error) at the time of bomb release.
  • Bomb release method.
  • Bomb-aircraft separation effects.
  • Physical and geometric characteristics of the bomb, including aerodynamic drag.
  • Non-standard atmospheric conditions, in terms of temperature, absolute pressure, density, dynamic viscosity.
  • Variation in wind velocity and direction vs. altitude (gradual and turbulent).
  • Coriolis force (a.k.a. Euler force, centrifugal force), resulting from rotation of the earth (primarily a factor during high-altitude bombing).
  • The earth's gravity acceleration "g". This is location and altitude dependent (the earth is not homogeneous and not perfectly spherical - more like a lumpy roundish potato)


The Small Knickebein systems ("kleine Bauform", "Kleinanlage"). The rotable antenna system had a width of about 45 m, and a track diameter of a little over 31 m. The Small Knickebein was rotated with two manual winches, which required a crew of 3-4 men (ref. 230Q12).

Oddly, the Small Knickebein ground station installation was referred to as FuSAn 721, just like the large Knickebein...


Fig. 11: Close-up of Small Knickebein Kn-8

(source: unknown; possibly attributable to Abbé Delacotte, probably 1944)

Apparently, the initial construction had some weaknesses: a diagonal support arm was added to the lower left- and right-hand cantilevers, and the dipole feed wires were supported at the mid-point between adjacent dipoles. Compare the photo above and below.

Knickebein klein

Fig. 12: Small Knickebein without additional supports - date and Kn-location unknown

(source: adapted from Fig. 37 in ref. 181 (1942); the X-shaped object in the right-hand background may be a monitoring antenna)

The outermost dipoles - as well as the dipole feed wires - may have swayed and bobbed too much. This could have led to undesirable variations in the electrical properties and in the radiation-pattern of the antenna system. Based on available photos, at least Kn-1, -8, -9, -11, and -13 had such additional supports.

Knickebein klein

Fig. 13: Small Knickebein without and with additional structural supports

UPDATE/EXPAND The antenna system comprised a single row of 4 dipoles plus "reflectors" per sub-beam, instead of 2x8 of the Large Knickebein. I.e., only one quarter the overall size of the Large Knickebein. As a result, the width of the equi-beam was about twice as large: ≈0.6º instead of ≈0.3º. ***** TBC Ref. 2A ; ****** The side-lobes were also stronger ****SEE PATTERN SECTION ****. However, the small Knickebein stations were installed closer to their targets in Britain than the large Kn-2, Kn-4, and Kn-12 stations in Germany. So, over the target location, the width of the equi-beam was still acceptable. Small stations were used both as main guide-beam and as crossing-beam beacon.

The concrete ring was ca. 110 cm wide (≈3.5 ft) and had an outer diameter of 31.3 m OD (≈103 ft). Ref. 230Q19.

The Figure below shows three types of Small Knickebein circular track:

  • a curved steel I-beam, almost fully embedded in the concrete ring (i.e, not flush with the concrete),
  • a curved steel I-beam, clamped directly onto the top of the concrete ring.
  • a curved steel I-beam, attached with simple rail-chairs onto wooden ties (a.k.a. crossties, UK: "sleepers") on a track bed of crushed rock or coarse gravel. The track bed on top of an embedded concrete ring foundation. ****** mounting plates only on the outside of the ring, see below and Kn-1.

The top flange of the I-beam is 18 cm wide (≈6 inch; at least at Kn-6; ref. 230Q19).

Knickebein klein

Fig. 14: I-beam rail almost fully embedded in the concrete ring and jointed heads of two rail sections

(source: adapted from ref. 230Q26)

Knickebein klein

Fig. 15: trace of I-beam rail clamped onto top of the ring and rail clamped to wooden ties on track bed on the ring

(source left-hand image: adapted from ref. 230Q1); right-hand iamge: ref. 90B , p.21)

UPDATE/EXPAND Kn-13 photo above & Kn-9 (via Fig. Kn-9-G): at least these Small Kn had track bed with ties.

The right-hand photo above shows that the small support wheels were spoked. From available photos, it is difficult to ascertained if the wheels had a flange, like train wheels. Flanged wheels would have kept the rotable superstructure centered on the track. The photos in the next Figure suggest that they were not flanged (see green circle), and narrower than the flat steel track they rode on. I.e., the wheels were like small spoked cart (wagon) wheels, with a flat rim. 

Those same photos also suggest that brackets where suspended onto the inside of the wheels, against the rail (see orange ovals). Like wheel flanges, this could have kept the wheels centered on the I-beam rail. On the other hand, these brackets may have been clamped onto the top flange of the rail, to immobilize the system when not being rotated. I.e., like parking brakes. This could also explain why the top flange of the embedded rail was not flush with the top of the concrete ring...

Knickebein klein

Fig. 16: The wheels of Small Knickebein Kn-13 at Noto/Italy (summer 1943)

(source left-hand image: 230Q24; right-hand image: ref. 90B, p. 21)

There was a large cubical concrete block at the center of the ring - just like at the Large Knickebein. It has two functions:

  • To pass one or more cables from the transmitter to the rotable antenna system. The transmitter was located outside the ring, in a nearby barrack.
  • To keep the four wheels centered on the track. See the discussion below.

The block was not needed to help support the weight of the rotable superstructure and prevent it from sagging:

  • The truss cage below the antenna system spanned about 30 m (≈100 ft). Note that the lower truss of the Large Knickebein was much larger: it spanned about 2x45 m - so at least 45 m (≈150 ft) without any support!
  • There was a steel pivot mounted on top of the center of the concrete block, see further below. The pivot mated with a bearing that was mounted at the center of the bottom of the truss cage below the antenna system. The mating bearing was either a very simple "2 concentric tubes" slide bearing (a.k.a. "journal bearing", as used in train wheels), or a ball bearing. By design, these bearing types are only designed to handle radial forces ( = perpendicular to the axis of rotation), not axial forces ( = in the direction of the axis of rotation). Significant axial forces will damage or destroy a ball bearing, and will simply cause a slide bearing to slide axially - without that bearing providing any support.
  • The Large Knickebein had not one but two rings, with two pairs of support wheels per ring. So, its inner ring also supported part of the large weight. The central concrete block of neither the Large nor the Smal Knickebein supported any weight of the rotable superstructure.

Knickebein klein

Fig. 17: The concrete block at the center of Kn-8

(source: unknown; adapted from a photo that is possibly attributable to Abbé Delacotte, probably from 1944)

The standard concrete block measured 1.4 x 1.4 m (≈4.6x4.6 ft; measured at Kn-8, ref. 230Q1), compared to ca. 2x2 m for the Large Knickebein. Photogrammatic analysis of available photos suggests that 1) the top of the concrete block of the Small Knickebein was ca. 80 cm higher than the top of the concrete ring, and 2) the bottom of the truss cage was ca. 30 cm higher than the top of the concrete block.

Knickebein klein

Fig. 18: Cross section of the concrete ring and central concrete block

Knickebein klein

Fig. 19: The concrete cube at the center of several Small Knickebein rings in France

(source: Kn-6 - ref. 230Q26; Kn-8/9/10 - adapted from ref. 230Q1, retrieved Sept.2022, used with permission)

Remember that the Knickebein system never rotated continously - it was only rotated very slowly (with the help of winches) when it was necessary to change the normally static pointing direction of the beam. Without wheel flanges, or equivalent thereof, the central pivot on the concrete support block at the center of the concrete ring (see below) had to be quite sturdy, in ordetr to withstand large side forces.

An adjustable hollow steel pivot was mounted on top of the concrete block. It is mounted at the center of a heavy octogonal steel plate. Possibly, it is threaded into that plate. The height (and possibly the levelness to a small extent) of this plate was adjustable with vertical bolts. The adjustment bolts are threaded into a large heavy reactangular steel plate. There is small thin rectangular steel plate directly on top of the large plate. The hollow steel pivot is mounted on a 33 cm square steel plate (≈13 inch). The lower part of the pivot has a diameter of 14 cm (≈5.5 inch) and a wall thickness of 4 mm. The top part 11 cm (≈4.3 inch). The small plate is mounted onto a large heavy steel plate. This plate is rectangular (84x60 cm, ≈33x23.6 inch) and 3 cm thick (≈1.2 inch). Ref. 230Q1.

Knickebein klein

Fig. 20: Fixed pivot base with adjustable pivot plate (left) and with adjustable plate removed (right)

(source: Kn-6 - ref. 230Q26; Kn-8 - adapted from ref. 230Q1, retrieved Sept.2022, used with permission)

Knickebein klein

Fig. 21: Best-estimate sectional drawing - based on available photos, measured & derived dimensions

As stated above, the pivots are hollow. They had to be hollow, because they are the conduit for the cables from the transmitter (located outside the concrete ring) to the rotable antenna system. The steel plates have a hole at the center. The cable(s) entered the concrete block at the bottom or one of the side (above or below the original ground level). Remember that the Knickebein installation was only rotable over a limited angular range. So, there was no need for a rotating antenna cable coupler (e.g., slip rings). The pivot mated with a bearing that was mounted at the center of the bottom of the truss cage below the antenna system. The mating bearing was either a very simple "hollow tube" slide bearing (a.k.a. "journal bearing"), or a ball bearing.

Apparently, anchoring the four corners of the base plate with a steel reinforcement bar (rebar) in the concrete was not sufficient to adequately immobilize the plate. In Fig. 20 above, it is clearly visible that - at least at Kn-6 and Kn-8 - additional concrete was poured around the base plate.


Per ref. 230Q8 (1939), the transmitter was that of the Lorenz aerodrome "blind" approach-beacon system: the standard 500 watt "Anflugführungssender" model AS 4:

TFK AS 4 transmitter

Fig. 22: The standard Telefunken landing beacon transmitter AS 4 and associated power supply NA 500

(source: adapted from Fig. 3 and Fig. 4 in ref. 39C)

The AS 4 transmitter has the following characteristics (ref. 39C):

  • Output power:
  • 500 watt at nominal primary supply voltage (220 or 380 volt AC, 3-phase, 50 Hz).
  • 300 watt for primary supply voltage 10% below nominal.
  • Modulation:
  • Amplitude modulation (AM).
  • Modulation index: 90% ( = modulation depth = ratio of modulation signal amplitude and carrier amplitude), adjustable.
  • High-frequency (HF) : crystal oscillator, first frequency multiplier (2x), second frequency multiplier (2x), first push-pull amplifier, and the final push-pull power amplifier.
  • Internal power supply (with forced-air cooling):
  • Input: 24 volt DC from the external power supply NA 500 (which also provides four anode/plate and bias voltages) - see below.
  • Output: 4, 8, and 23 volt DC (heater voltages for tubes/valves and oscillator crystal oven).
  • Tone generator: built-in, 1150 Hz .
  • Crystal oscillator:
  • The crystal was placed in a small enclosure with a heating element and thermostat. This is referred to as a "crystal oven". Its purpose is to keep the temperature of the crystal near the point where the slope of the crystal's frequency vs. temperature curve is zero. The crystals of the standard AS 4 transmitter were made by the Loewe company (probably the Radio Frequenz G.m.b.H subsidiary of Loewe-Opta, frmr. "Radio A.G. D.S. Loewe"; ref. 221). The Loewe crystal oven had a temperature setpoint of 58 °C (136 °F), ref. 39C.
  • The transmitter has two frequency-doublers after the crystal oscillator. Hence, the crystal oscillator operated at 30-33.3 / (2x2) = 7.5 - 8.33 MHz. It is unknown if the oscillator operated at (or near) the fundamental crystal resonance frequency, or at an overtone frequency (i.e., near an odd integer multiple (typ. 3, 5, or 7) of the fundamental crystal frequency).
  • Antenna-reflector keying unit unit:
  • 20 volt synchronous AC motor The motor turned continuously. Its output shaft drove four notched disks (two for when the beacon was using the front course, the other two when using the back course = with left/right sub-beams swapped). Their switch contacts controlled relays for switching the two reflector rods of the antenna system.
  • Power-up time:
  • 70 sec (time delay relay), to ensure that the cathode of each tubes is sufficiently heated to produce full electron emission, prior to applying the anode voltage.
  • An additional ≈3 minutes for achieving stable frequency.
  • The transmitter channel-frequency could be changed in 3-5 min, depending on the number of operators and their qualifications (ref. 183). This requires adjustment of five anode- and antenna-currents, and eliminating keying-clicks by adjusting the tone-pulse shape (Section III in ref. 39C).
  • Size: without the feet -114x121x70.6 cm (WxHxD; 4x4x2.3 ft)
  • Weight: 402 kg (900 lbs)
  • Housing: "Silumin" die-cast. Silumin was an aluminium-silicon alloy of the Metallbank und Metallurgische Gesellschaft in Frankfurt/Main. It was also marketed in the USA as "Alpax", dating back to the early 1920s.

The associated external power supply of the AS 4 is "Netzanschlußgerät" model NA 500. It has the following characteristics (ref. 39C):

  • Input power: separate inputs for 220 and 380 volt 50 Hz 3-phase AC ("Drehstrom"), 5 kVA.
  • Output voltages: -24, -100, +400, +1000, and +2000 volt DC; 20, 220, and 4 volt 50 Hz AC.
  • The input step-down transformer was connected to either 220 or 380 volt 3-phase 50 Hz AC.
  • The voltage of one of the three output phases of this transformer was regulated with an 8 amp "carbon pile regulator" (a.k.a. "Kohledruckregler", "Pintsch-Regler"). This is a fast electro-mechanical voltage regulator, comprising a stack of several dozen carbon discs or rings ("Kohlescheibensäule"). Ref. 208A, 208B, 208C. The resistance of the carbon stack depends on the pressure that is applied to it. This pressure is applied by an electromagnet, whose DC control-current is derived from the controlled voltage with a separate transformer-rectifier. This control-current depends on the load, as well as on the primary 3-phase voltage. This closed-loop control keeps the regulated voltage constant to within ±3% for ±10% input voltage variation. In case of over-voltage of the primary 3-phase power, the regulator mechanism reaches its extreme position. This actuates a contact that shuts down the anode voltages, after a persistence delay of about 10 sec.
  • The input transformer fed three separate single-phase transformers, each followed by a selenium rectifier bridge and a filter, to generate -24, +400, and +1000 volt DC. The 24 volt DC was reduced to 4, 8, and 23 volt DC by the internal power supply of the transmitter.
  • The -100 and +200 volt DC were generated with a similar scheme, but with two separate 3-phase transformers.
  • The 20 volt AC was used by a motor in the timing-unit of the AS 4. See above.
  • Cooling: forced-air ( = fan).
  • Size: 183x67x50 cm (WxHxD, 6x2.2x1.6 ft).
  • Weight: 340 kg (752 lbs).

The tone pulses were modulated with a 1000 Hz tone per ref. 230Q7 ***TBC****; but 1150 Hz per ref. 39C (i.e., the standard off-the-shelf model AS 4), and ref. 230D1 (RV Jones, measured); 230Q6 states landing beam 1000 Hz, but Kn 1250 or 1850 Hz; p. 109 & 129 in ref. 2C4; = standard Lorenz approach beacon transmitter]. The "E" dots were 1/8 sec wide, the "T" dashes 7/8 sec - the same 1:7 rythm as the standard Lorenz blind landing system.

The transmitter had a single output to the antenna system. For use in the Lorenz landing beam system, the interface to the antenna system was straightforward. This antenna system comprised three parallel vertical dipole elements. The center element was continously energized by the transmitter. The other two dipoles were passive, i..e, not connected to the transmitter. These passive dipoles had a relay across their feedpoint. With its relay closed, a passive dipole acted as a reflector for the driven dipole. With the relay open, the two disconnected dipole halves were too short to have any effect. The AS 4 included a control relay that was energized in a 1/8-second "on", 7/8-second off manner. The associated relay contacts connected 24 Vdc to the small reflector control-relays. Special circuitry (based on capacitor charge-time via a resistor) was used to ensure a 5 msec pause between one reflector being deactivated and the opposite one being activated. Of course, the antenna system was tuned, such that both sub-beams of the beacon had the same field strength at a predefined position of the control receiver. This was verified during monthly maintenance of the AS 4 transmitter (ref. 39C). With the center dipole always transmitting, these measures ensured a "click-free" beam signal being received in the aircraft. A simple-but-effective refinement that the British countermeasures did not have, which made them recognizable.

The Knickebein antenna system comprised a left-hand and a right-hand antenna array. These two arrays had to be energized alternatingly by the transmitter. I.e., not like the Lorenz Beam antena system, where the center dipole was always energized by the transmitter, and the two passive ( = never energized by the transmitter) reflector dipoles were activated alternatingly. As the AS 4 was re-used for the Small Knickebein, there were several options

  • use two separate feedline cables to the Knickebein antenna system, alternatingly connected to the single output of the TX, with additional power-relays at the transmitter.
  • use one feedline cable, permanently connected to the single transmitter output, plus separate wires for passing two relay-control voltages to two relays at the antenna system, to alternatingly connect the two arrays to the feedline.
  • use one feedline cable, permanently connected to the single transmitter output, and pass two relay-control voltages via that same cable to two relays at the antenna system. This requires simple "Bias-T" circuitry at the both ends of the feedline cable, to inject and recover the relay-control voltages - without these voltages interfering with the transmitter signal - or with the transmitted signal interfering with the relay control. See the inset in the Figure below.
  • This technique of passing DC voltage via a radio-frequency cable is still commonly used in modern times. E.g., to provide DC supply voltage to the LNA receiver-amplifier mounted on all satellite TV dishes, or to control the motor of a tuner a the feedpoint of a transmitter antenna.

The third option was used (ref. 39C-39E). This required no modification of the AS 4 transmitter and no additional circuitry. The only change compared to the standard Lorenz Beam system, was the need for heavier relays at the antenna system: they now had to switch full transmitter output power (500 W), instead of the much lower power level induced in the reflector dipoles.

Knickbein AS 4

Fig. 23A: interconnect scheme of the AS 4 for the Lorenz beam - with remote control of the two reflector control-relays

(source: adapted from ref. 39C- 39E)

Knickbein AS 4

Fig. 23B: Opened front of the AS 4 - Tone-generator/keying drawer and power supply drawer (with fan) pulled out

(source: adapted from Fig. 5 and Appendix 1 in ref. 39C)

Knickbein AS 4

Fig. 24: Interconnect scheme of the AS 4 for the Small Knickebein - with remote left/right sub-beam switching

(source: adapted from ref. 39C- 39E)

The single feedline cable approach is confirmed by the cable stub that emanates from the top of the concrete central support block of Kn-10. It has an estimated diameter of 7-8 cm (≈3 inch):


Fig. 25: Antenna feed cable - emanating from the top of the concrete block of Kn-10

(source: adapted from ref. 230Q1; strands of heavy copper wire, copper inner-shielding, lead outer-shielding; insulation material disintegrated)

The standard transmitter-to-antenna antenna feedline cable ("Energieleitung") consisted of a shielded two-wire transmission line (TL), a.k.a. shielded two-wire TL, shielded balanced TL, shielded pair; German: "(ab)geschirmte symmetrische Bandleitung", "(ab)geschirmte Zweidrahtleitung", "(ab)geschirmte symmetrische Doppelleitung", "zweiadriges abgeschirmtes Kabel"). This type of cable was also used in the mobile Lorenz landing beam system (ref. 39E) and, e.g., in the antenna system of the "Bernhard/Bernhardine" beacon system (ref. 181, pp. 110, 111). This cable is basically two parallel wires in metal tubing or braiding, with a dielectric material between the wires, and a round or oblong metal conduit. See Fig. 26 below. In modern times, we refer to this type of cable as "twinax" (as opposed to single-center-conductor "coax").

Bernhard antenna system

Fig. 26: "symmetrische Hochfrequenzleiting mit Abschirmung" - shielded balanced transmission line (radio frequency cable)

(source: Fig. 28 in ref. 197)

TBD: diameter of the cable at Kn-10. NOTE: the wire strands of the cable at Kn-10 (see Fig .25) are significantly heavier than what would be required for connecting a 500 watt transmitter to an antenna system. Likewise, for carrying 24 volt DC to control the reflector relays (one at a time). However, as stated before, the structure of the Small Knickebein was rotated electrically. This implies that one or more motors where installed in the truss cage below the antenna system - either at one or more of the wheels, or at the central pivot of the concrete block below that truss cage. Note that the small wooden cabin installed inside that truss cage is not centered - see, e.g., Fig. 12 above. This suggests that there was no motor there, but at one or more of the wheels. The electrical power for the motor(s) would also have to be supplied via the antenna feed cable, inserted at the transmitter end of that cable, just like the control voltage for the reflector relays. Of course, such a motor would require a high current, and, hence, a heavy gauge cable. The Figure below show a box above one or more wheels of several Small Kn's. Possibly, these are motor hoods. A shaft seems to decend straight down from these boxes and then horizontally to the wheel shafts. These could be drive shafts...

Small Knickebein

Fig. XX: Small Knickebein - box with motor above some of the wheels, with angled drive shaft ?

(source: (left, Kn-8), unknown; (top  Kn) unknown, Fig. 37 in ref. 181; (right Kn) unknown; (bottom Kn): Kn-13, ref. 98B)


The Large Knickebein installations Kn-2, Kn-4, and Kn-12 had an enormous rectangular antenna system, see Figure 4 above. Its rectangular steel truss frame measured 93 x 29 m (WxH, ≈310 x 95 ft). The center vertical truss divided the antenna system into two sides - one to generate the "E" sub-beam and one for the "T" sub-beam:

  • Each sub-beam was created with a large array ("Gruppenantenne") of vertical dipoles. All dipoles had the same 1λ length. For the operating frequency of 30-33.3 MHz, the wavelength λ is about 9.5 m.
  • Each array comprised two rows of eight vertical dipoles, one row right above the other. I.e., a "stacked array". These parallel dipoles were spaced horizontally by a standard ½λ.
  • Each of these dipoles had another dipole right behind, at a distance of ≈¼λ. These were not passive reflector rods, but active dipoles, driven by the single transmitter. This makes for more effective side-lobe reduction (see, e.g., p. 71 in ref. 137A).
  • The dipoles and reflectors were made of wire ropes. The material is unknown: steel wire strands, or bronze wire strands around a steel ( = strain resistant) core.

The Small Knickebein installations (Kn-1, Kn-3, Kn5-Kn11, and Kn-13) also had a symmetrical antenna system with a 165°/15° angle, but a lot fewer dipoles:

  • Again, each sub-beam was created with an array of parallel vertical 1λ dipoles, with ½λ horizontal spacing.
  • But now, there were only four dipoles per side, not eight!
  • Also, each array comprised only a single row of dipoles, not two vertically stacked rows.
  • Here too, each dipole had another dipole right behind it, again at a distance of ≈¼λ.
  • As a result, the frontal area of this antenna system was only one quarter the size of that of the Large Knickebein.
  • The dipoles and reflectors were made of large-diameter metal tubes instead of wires, see Fig. 10 and 11. A larger radiator diameter makes an antenna more broadband ( = usable over a wider frequency range, without the need for "re-tuning" the system).

The diagram below shows the configurations of the Large and Small Knickebein antenna systems:

Knickebein antenna configurations

Fig. 27: Dipole array configurations of the Large and Small Knickebein antenna systems

(both systems are drawn to the same scale; rear dipoles are not visible in the front views)

There is a minor difference between the Large and the Small Knickebein regarding how the feedline from the transmitter is connected to the arrays. The arrays of the Large Knickebein are fed at one end of the array. The arrays of the Small Knickebein are fed mid-array.

Knickebein antenna feed configurations

Fig. 28: Feedline configurations of the Large and Small Knickebein antenna systems

(note: the rear dipoles are not visible in these front views; associated connections to transmitter not shown)

Per ref. 230Q8 (1939), a later Knickebein version was to use an electrical phase shift between the left and right dipole arrays instead of a mechanical V-angle, to obtain the desired overlap between left-hand and right-hand beams. A variable phase shift greatly simplifies precise adjustment of the beam overlap, hence, of the width of the equi-signal guide beam.


There are several Knickebein-beam radiation pattern diagrams floating around in various publications, without reference to any reputable source. As always: trust, but verify! This is why I decided to create a simple model of the large Knickebein antenna array myself. I always use the fabulous 4NEC2 antenna modeling freeware tool. The complete antenna system comprises two independent identical arrays side-by-side (one for the dash-beam, one for the dot-beam), but only one beam transmits at a time. So, I only modeled one sub-beam. The results are shown below. Note that, as is standard for radiation pattern diagrams, a logarithmic scale (decibel, dB) is used for the signal-strength (see far left side of the two figures below).

Knickebein pattern

Fig. 29: Top, oblique, and side view of the radiation pattern of a Large Knickebein sub-beam ("E" or "T") - in free space

(the NEC file of my 4NEC2 model is here - it is not optimized)

The views above are actually quite similar to the generic patterns shown in other publications. However, they are only valid for an antenna in so-called "free space". I.e., without any objects anywhere near, or ground below, the antenna. This is unrealistic, in particular for an antenna system close to the ground (in terms of the number of wavelengths λ of the transmitted signals), as is the case with Knickebein (with λ ≈ 9.5 m). The figure below shows the impact of ground reflections (assuming conductivity and dielectric constant of standard "real ground"), clearly beyond the modeling capabilities of the era. My model does not include the steel trusses around the Knickebein arrays, which could cause some pattern distortions. In practice, this was "not disturbing" (pdf p. 4 in ref. 184F1).

Knickebein pattern

Fig. 30: Top, oblique, and side view of the radiation pattern of a Large Knickebein sub-beam ("E" or "T") - over ground

(the NEC file of my 4NEC2 model is here)

As illustrated above, the antenne array of the Large Knickebein comprises two stacked rows of vertical dipole antennas. The second row does not significantly change the radiation pattern. However, the overall transmitter power is divided 50/50 between the two rows. I.e., each row only gets half the transmitter power. This is not the case with the Small Knickebein: the full transmitter power goes to a single row of dipoles. That row comprises only half the number of dipoles of its Large counterpart, which concentrates less radiated power into the forward lobe of the pattern: less directivity. This makes the resulting sub-beam and equi-signal beam about twice as wide as those of the Large Knickebein. For the installation locations of the Small Knickebein stations, this reduced performance was still sufficient, at much reduced cost, size, and construction time.

Knickebein pattern

Fig. 31: Comparison of a Large & Small Knickebein sub-beam ("E" or "T") - in free-space & over ground

EXPAND: radiation pattern is dependent on the operating frequency = wavelength vs dimensions and spacing of the antenna elements w.r.t each other, grond, objects. This is shown in the radiation pattern below for the Small Kn for a 10% freq change (30 vs 33 MHz).

As mentioned above, the antenna elements of the Small Kn were made of metal tubes (ca. 10 cm Ø) instead of heavy wires. This made the antenna system of the Small Kn broadband, such that little or no re-tuning was required when changing operating frequency within the 30-33.3 MHz range = wavelength λ of 9-10 m. Of course, the length and diameter of the antenne elements, and the distances between the elements, were fixed in absolute terms. But they varied when expressed as a fraction of the operating wavelength. The shape of the radiation pattern depends on the latter, as illustrated below:


Fig. 32: The radiation pattern of the Small Knickebein for 30 and 33 MHz

(Source: ref. 2C3, p. 108)

ADD/EXPAND (MOVE???): audio.

Knickebein beams Knickebein beams

Fig. 33: The alternating "E" (dot) and "T" (dash) beams of the Knickebein beacon

Knickebein E/T sound - audio file still to be created...

Simulated sound of "Knickebein" meandering across the E-beam, Equi-Signal, and T-beam

(source: ©2023 Frank Dörenberg)

The radiation pattern of the Kn-stations was checked by extensive measurements. Ref. 230Q5 provides maps for the large Kn-4 station at Kleve-Materborn. Some 300 field-strength measurements were taken on the western side of this station ( = direction England), at a distance of 3.6 - 18 km, and on lines close to perpendicular to this station's central pointing direction of 270° (i.e., due west). Most measurements are spaced by only 40-50 m (≈130-165 ft). For measurments at a distance of 3.6 - 18 km, this implies an angular resolution of about 0.15 - 0.72 degrees. Some of these verification measurements were taken as late as 20 January of 1942! Measurements were done with a "Leistrahl-Kontrollwagen" - a model Kfz.72 radio truck, adapted to guide-beam verification. See ref. 230Q10 (1942) for more details on the selection of the geodetic and radio-electrical measurement points. The measurement data was entered in a "Kontrollbuch" register for the specific Knickebein. In particular, the position of the edges of the "dot" ( = "E") and "dash ( = "T") sub-beams was checked. Ref. 230Q9.

Knickebein check points

Fig. 34: Some radiation pattern check points for Kn-4 (marked with red dots) and a beacon measurement vehicle at Kn-2

(source: map - adapted from ref. 230Q5, photo: deutschesatlantikwallarchiv.de, retrieved April 2022)

The measurement points, typically right next to country roads, were marked with concrete "Einstellmarken" - lit. adjustment markers. The markers were painted white and had a  recessed "+" in the top surface. To hide their purpose, the identification number on the side was a running number. It was not linked to the bearing from the beacon to the marker.

Knickebein check points

Fig. 35: Specification of the concrete markers for the calibration measurement points.

(source: adapted from ref. 230Q9)

Ref. 230Q10 states that antenna azimuth correction values were marked on the large concrete ring of the Kn-4 station (which suggests that the same was done at the other two Large Knickebeins). It also states that, due to the terrain situation west of the Kleve station, not the entire azimuthal pointing range was covered by measurements. Several small azimuthal sectors were skipped. However, corrections for beam-pointing directions in the skipped sectors could be interpolated from special markings on the concrete ring. It is unclear where and how these corrections were marked on the concrete ring...


As described above, the three large Knickebein stations were built first. A that time, they were referred to by their location, not a number. When the small Knickebein stations were planned and built, all stations got a number - including the large stations. The numbering scheme is basically north-to-south, see the map below. This is why the "old" large stations are numbered Kn-2, Kn-4, and Kn-12 instead of Kn-1, Kn-2, and Kn-3.

6-minute video - zooming into each of the 13 Kn locations (2017-2020 aerial and satelite images)

The video clip has no sound track. If the player controls are not visible: move mouse cursor over the image

The exact map coordinates of all Knickebein stations are provided in each Kn-section below. You can also open my kml file with the Google Earth web app (or with the desktop app).

A full-size interactive Google Maps version of this map is available here. It has the same station locations markers. As in the above video, in most cases you can fully zoom-in the satellite image map, and see the actual remains of the station structures.You can click-and-drag the map with your mouse, and zoom in & out with your mouse-wheel (or use the buttons in the bottom left-hand corner of the map). Note: you must have maps.googleapis.com enabled in your browser.

Knickebein locations

Fig. 37: Table with the location of all Knickebein stations

Knickebein locations

Fig. 38: Kn-stations marked on various 1944 maps of the Luftwaffe Signal Corps (Luftnachrichten)

(source: adapted from ref. 210A-210F; note: Kn-2, -6, -7, -12 and -13 do not appear on these June-October 1944 maps)


  • Location: the village of Kleppe (part of the Klepp municipality) is located on Jæren - the large flat lowland area in the southern tip of Norway, that stretches from the Stavanger Peninsula southward. Kleppe is  about 23 km (14 miles) southwest of the city of Stavanger. It is a high point in the part of coastal Norway that is nearest Great Britain: about 255 km (283 mi) to the northeastern coast of Aberdeenshire/Scotland.
  • Map coordinates (DMS / DD): 58°46'12.9"N, 5°37'12.3"E / 58.770250, 5.620083 (Google Maps, OpenTopoMap).
  • Notes: On 23 June 1940, a large group of German officers came to Kleppe. The group went up to the highest point at Haugabakka, just outside the village, on the southwestern side. This mound is some 60-70 m above sea level. From there, they had a clear view in all directions, in particular across the North Sea towards Britain. A few days later, a hectic construction operation started. After a short time, a fully metal "skeleton" was erected that could be rotated on a track, using winches operated by 3-4 men at each end. Ref. 230Q4, 230Q11, 230Q12.

Knickebein station

Fig. Kn-1-A: Knickebein Kn-1 on the hill at Haugabakka/Kleppe

(source: ref. 230Q11)

Knickebein station

Fig. Kn-1-B: 1950s aerial photo of Haugabakka/Kleppe with old schoolhouse, and Knickebein track on the hill in the background

(source: Klepp Kommune Bildearkiv (ref. 230Q11); viewed from opposite direction of the hill vs. Fig. XXXXXX above)

Knickebein station

Fig. Kn-1-C: 1953 overhead aerial photo of the Knickebein at Haugabakka/Kleppe

(source: www.norgbilder.no, retrieved June 2022)

Knickebein station

Fig. Kn-1-D: The ring of Knickebein Kn-1 at Haugabakka/Kleppe - ca. 2000-2004

(source: ref. 230Q13; far right photo shows top of the steel track, with remnants of unidentied fasteners next to it)

Knickebein station

Fig. Kn-1-E: The ring of Knickebein Kn-1 at Haugabakka/Kleppe - June 2019

(source: Google Maps - Street View; note the North Sea barely visible on the horizon, to the right of the ring)


  • Location: Stollberg hill, about 3 km (2 miles) north-northwest of the town of Bredstedt in the far north of Germany (in the in the then-Prussian province of Schleswig-Holstein), next to the B5 Bundesstraße highway (Reichsstraße R5 at that time). With 44 m above sea level, it is one of the highest points in the area. This is ca. 32 km (20 miles) southwest of Flensburg.
  • There were several Lufwaffe airfields in the general area, with fighter and/or night-fighter units.The aerodrome of Leck, 16 km to to the north, was a Luftwaffe Fliegerhorst. It was constructed in 1939/40. Husum, about 11 km to the south, had a small civil aerodrome, Narrenthal, that was built in 1931. In September of 1939, it was expanded into a Luftwaffe Einsatzhafen (E-Hafen, operating base): Husum-Schauendahl. Luftwaffe fighters were stationed here full-time, starting May 1942. Nearby Husum-Schwesing was a decoy airfield ("Scheinflugplatz", ref. 119). Fliegerhorst Schleswig (a.k.a. Schleswig-Jagel) lies 44 km to the southeast, and became operational in 1937. Flensburg-Weiche airfield (a.k.a. Flensburg-Schäferhaus) lies 30 km to the northeast, and Westerland on the isle of Sylt about 50 km to the northwest. The latter was built in 1919 as Friesenhain-Westerland airfield. In 1935 it became a Luftwaffe  Fliegerhorst and in 1938 a Luftwaffe Einsatzhafen. Einsatzhäfen had a minimum field size (1x1 km), rail and road access, electrified, telephone, a large underground fuel depot, and ammunition depots.
  • Map coordinates (DMS / DD): 54°38'36.93"N 8°56'41.2"E / 54.643591, 8.944779 (Google Maps, OpenTopoMap).
  • Notes: large Knickebein version. Operating frequency: 30.5 MHz. Pointing direction range: 279° ± 45°. It was built in 1939 and operational in 1940. This "Knickebein" station was only active for about a year, until British jamming and spoofing became too effective. It was abandoned before mid-1941, at which time the site was guarded by civilians.

The following aerial photos shows Kn-2, looking in southeasterly direction. The tree-lined Reichsstraße 5 (R5) road to/from Bredstedt crosses behind it. Note the observation tower of the Flugwache (FluWa, "flight watch") in the foreground. The photo in Fig. Kn-2-C was taken from that tower. This FluWa probably started its activities in 1933, subordinate to the German navy "flight watch", and was moved to a nearby hill when the Knickebein was constructed (ref. 231). It reported aircraft activity to the Flugwachekommando (Fluko) at the nearby Husum aerodrome.

Knickebein large

Fig. Kn-2-A: Large Knickebein Kn-2 at Bredstedt/Germany - looking in southeasterly direction

(source: ref. 2C4, erroneously referring to it as "Kleve", which is Kn-4; vertical dipole wires added manually by ref. 2C4 author - one of his habits)

Knickebein large

Fig. Kn-2-B: Higher-quality image of part of Fig. Kn-1-A

(source: ref. 5B; no vertical dipole wires, implying this is part of the original image taken during construction)

The next photo was taken from the top of the mast that is visible at the bottom/center of the two photos above:

Knickebein large

Fig. Kn-2-C: Large Knickebein Kn-2 at Bredstedt/Germany - under construction in 1939

(source: Fig. 36 in ref. 181 of 1942; the red circle shows the size of a man)

Knickebein large

Fig. Kn-2-D: The fenced-in Large Knickebein Kn-2 at Bredstedt/Germany - dipole antennas not (yet) installed

(source: ref. 230Q14)

Knickebein large

Fig. Kn-2-E: Same view, but with the 32 vertical dipole antennas installed

(source: p. 9 in ref. 261L)

Knickebein Kn-2

Fig. Kn-2-F: A "Meßfahrzeug" radio van for measurement & calibration of the radiation pattern - on the south side of Kn-2

(source: deutschesatlantikwallarchiv.de, retrieved March 2020)

Mid-1944, the installation was still there (ref. 120), though obviously not operational. Sometime later, the installation was replaced by "Bernhard" station Be-9. The concrete ring of this rotating-beam beacon was built between the defunct outer and inner circular track of the "Knickebein", see the Figure below. The barracks outside the "Knickebein" were retained for the "Bernhard" station. Two brick building were added inside the "Knickebein" circle, to support the operation of the "Bernhard" station.

This "Knickebein" station was only active for about a year, until British jamming and spoofing became too effective. It was abandoned before mid-1941, at which time the site was guarded by civilians. Mid-1944, the Knickebein installation was still there (ref. 120), though not operational. Sometime later the installation was replaced by "Bernhard" station Be-9. Luftwaffe Signal Corps maps of 15-June-1944 are marked with an estimated completion date of 1 August 1944 (ref. 201A, 210E). The concrete ring of the Bernhard beacon was built inside the defunct "Knickebein" circle, off-center. The barracks outside the "Knickebein" circle were all put in place for the "Knickebein". Two brick building were added inside that circle, to support the operation of the "Bernhard" station. After the war, the barracks were used for German refugees from eastern Europe (ref. 120).

Stollberg Bredstedt Knickebein Bernhard site

Fig. Kn-2-G: Aerial photo of the Stollberg/Bredstedt site - March 1945

(source: unknown)

Berhard station

Fig. Kn-2-H: Annotated satellite image (2022) of the Stollberg site

(at the 10 o'clock position of the circle: modern transmitter tower (TV, FM radio, cell phone); dashed blue lines show where the road used to be)

There were living quarters on the north side of the "Knickebein" ring (officers may have been quartered in the town/village). There was also a guard house and a "Wirtschaftsbaracke" (canteen, possibly laundry and washroom facilities) to the northeast. There was an electric power barrack ("Generatorbaracke") about 25 meters to the east of the Knickebein ring. The concrete foundation for the generator is still visible in recent (2022) satellite images - as is the large "Knickebein" ring (see just inside the bottom part of the large yellow circle). Between the "Wirtschaftsbaracke" and the "Generatorbaracke", there was a light air-raid shelter ("Luftschutzunterstand"), dug out into the ground, and reinforced with a fence  made of wooden poles.

Berhard station

Fig. Kn-2-J: Wooden barracks on the east side of the Knickebein ring, behind a wooden fence

(source: R. Grzywatz, used with permission)

After World War II, these barracks were used for housing German refugees from eastern Europe (ref. 120).

Knickebein large

Fig. Kn-2-K: Name of the concrete construction company on the remnants of one of the concrete buildings

(source photo: bunkerratten.de, retrieved July 2022; source business register: entry in the 1921 Berliner Handels-Register)


  • Location: in the dunes of the North Sea shore, outside/XXXX side of Julianadorp / The Netherlands (6 km SSW of Den Helder, 60 km NNW of Amsterdam). Kn-3 is located at about 19 m above sea level in the dunes along the North Sea shoreline of the Netherlands, about 60 km northwest of down-town Amsterdam. More precisely: about 2 km northwest of Julianadorp village, 7 km southwest of the Navy port of Den Helder, and ca. 4 km west-southwest of De Kooy airfield. The latter started in 1918 as a Royal Netherlands Navy Air Service field. In the 1980s, it became shared with civiil aviation activities. The associated part of the airfield is called Den Helder Airport. 365 km NW of down-town London and 450 km east of Birmingham.
  • Map coordinates (DMS / DD): 52°54'47.81"N 4°43'00.5"E / 52.913280, 4.716807 (Google Maps, OpenTopoMap).
  • Notes: small Knickebein version. Per Luftwaffe/Luftnachrichten maps (ref. 210C), Kn-3 was being dismantled ("im Abbau") early September 1944.



Fig. Kn-3-A: Aerial photo from RAF Photographic Reconnaissance Unit (P.R.U.) Sortie H/175 No. 906 of 10 March 1941

(source: ref. 252T)


Fig. Kn-3-B: Site map based on RAF Photographic Reconnaissance Unit (P.R.U.) Sortie H/175 No. 906 of 3 Nov. 1941

(source: adapted from ref. 252T)


Fig. Kn-3-C: The remnants of the Kn-3 ring are still visible in a 2008 satellite image

(source satellite image: toporeis.nl)


Fig. Kn-3-D: German officers in the dunes with Knickebein in the background - allegedly Kn-3, date unknown

(source: eBay)


Fig. Kn-3-E: Track of the Kn-3 - ca. 2014

(source: bunkerinfo.nl, retrieved September 2022)


  • Location: Kleve-Materborn (62 km NW Duisburg); about 8 km south of where the river Rhine enters The Netherlands. This is the German town that is closest to London: 430 km, ≈265 miles). Cleve is spelled Kleve since a German spelling reform of July 1935, and is spelled Cleves in English. Located 4.3 km to the northwest of the site of the large Telefunken (Meißner) "Kompass" stepwise rotating beam beacon (1917-1918) at Bedburg-Hau.
  • Map coordinates (DMS / DD): 51°47'18.88"N 6°6'11.50"E / 51.788579, 6.103070 (Google Maps, OpenTopoMap).
  • Notes: large Knickebein version. Frequency 31.0 MHz. Pointing direction range of 270° ± 45°.


Construction activities started in September of 1939. Ref. 230Q21. In December of 1939, once the inner and outer concrete foundation rings were finished, workers of the Berlin-based antenna manufacturer (Hein, Lehmann & Co.) starting building the rotable antenna structure. These were the same workers who had earlier built the Knickebein structure at Stollberg hill near Bredstedt (Kn-2). Construction of the Kleve station was completed early March of 1940. On the 9th of that month, the antenna workers moved on to the Knickebein construction site "near Basel" ( = the nearest large city), i.e., at Kn-12. The Kleve Knickebein was operational ( = tested & calibrated) by mid-March of 1940. In April of 1940, the structure was painted in camouflage gray colors. The station was staffed by about 30 station military, incl.  female technical staff. It was destroyed by a German demolition squad in January of 1945

Not first Kn to be intercepted by the British?

Ref. 230Q8 (1939, Knickebein & Karussel)

Knickebein large

Fig. Kn-4-A: Looking along the suspended dipoles, standing on top of the bottom truss of Kn-4

(source: deutschesatlantikwallarchiv.de, retrieved March 2020)

Knickebein large

Fig. Kn-4-B: Aerial photo of Kn-4 during the severe winter of 1944/45

(source: photo adapted (incl. 180° rotation) from ref. 230Q20 (January 1945))

Knickebein large

Fig. Kn-4-C: Same area on a Canadian Army topographic map of the town of Cleve - January 1945

(source: ref .230Q22; compare to the aerial photo above of the same area)

Knickebein large

Fig. Kn-4-D: Canadian Army personnel inspecting the Kn-4 site - 10-14 February 1945

(source: adapted from ref. 230Q16)

Knickebein Kleve

Fig. Kn-4-E: 1950s aerial photo of the Kn-4 area

(source: www.geschichtsspuren.de forum, post of 7 April 2019; a small section of zig-zag trenches still visble on the northwest side of the ring)

Knickebein Kleve

Fig. Kn-4-F: Recent satellite image of the same area

(source: google maps, accessed July 2022)


  • Location: w.r.t. Bergen op Zoom and Rotterdam, railroad. Ref. 252S: Located ca 33 miles from the North Sea shore, ca. 500 yards from the shore of the Oosterschelde estuary, 2.5 miles [TBC W] from Woensdrecht airfield north end of 90° turn railway line changes from E - N, 3/4 miles [1 km] NW of Korteven hamlet. About 180 m to west of the "Lindonk" farmstead.
  • Map coordinates (DMS / DD): 51°27'03.0"N, 4°18'00.0"E / 51.450833, 4.300000 (Google Maps, OpenTopoMap).
  • Notes: small Knickebein version; no remains visible in satellite image.

Note: per ref. 210C (Ln map of August 1944), Kn-5 was dismantled by 5 September 1944.

L Two large rectangular bldgs, the one nearest the Kn is of solid construction ["bunker"] with windows painted on the side, probably contains transmitter gear. Stout paling fence around et station.


Fig. Kn-5-A: Part of aerial photo from RAF Photographic Reconnaissance Unit (P.R.U.) sortie T/687 on 27 Sept. 1941

(source: adapted from ref. 252S)


Fig. Kn-5-B: Part of aerial photo from RAF Photographic Reconnaissance Unit (P.R.U.) sortie T/831 on 19 Oct. 1941

(source: adapted fom ref. 252S)


Fig. Kn-5-C: Site map based on RAF Photographic Reconnaissance Unit (P.R.U.) Sortie T/653 No. 735 of 22 Sept. 1941

(source: ref. 252S)

The two "Station Buildings" and the camouflage-net-covered object that are marked in the sketch above, are clearly visible in photo in Fig. Kn-5-B above. The "station building" nearest the Kn-ring is a concrete bunker, made to look like a farm house. It was probably the tranmitter building.


Fig. Kn-5-D: The location of the Kn-5 ring is still visible in this 2006 aerial photo

(source aerial photo: topotijdreis.nl, retrieved September 2022)


  • Location: Mt. Violette / France (350 m N of Le Haut Pichot, 1.8 km N of Halinghen, 13 km SSW of Boulogne-sur-Mer). At the highest point in the area: 121 m ASL. 10 km north-northeast of "Bernhard" beacon station Be-3 at Le-Bois-Julien. w.r.t. down-town London?
  • Map coordinates (DMS / DD): 50°37'02.45"N 1°40'56.82"E / 50.617347, 1.682449 (Google Maps, OpenTopoMap).
  • Notes: small Knickebein version.



Fig. Kn-6-A: Topographic map of the Mt. Violette area

(source: adapted from www.geoportail.gouv.fr)


Fig. Kn-6-B: Part of aerial photo from an RAF Photographic Reconnaissance Unit (P.R.U.) sortie on 21 June 1941

(source: adapted fom ref. 252P)


Fig. Kn-6-C: Part of aerial photo from RAF Photographic Reconnaissance Unit (P.R.U.) Sortie T/653 No. 735 of 22 Sept. 1941

(rotated for "north up" orientation; source: adapted from ref. 252P)


Fig. Kn-6-D: Site map based on RAF Photographic Reconnaissance Unit (P.R.U.) Sortie T/653 No. 735 of 22 Sept. 1941

(source: adapted from ref. 252P)


Fig. Kn-6-E: Aerial photo of the Kn-6 site - date unknown (possibly 1944), note zigzag trenches compared to Fig. Kn-6-D

(source: unknown; also used on rear cover of ref. 90C)


Fig. Kn-6-F: Aerial photo of 4 October 1947

(source: adapted from full-size image at ign.fr, retrieved September 2022)


Fig. Kn-6-G: Satellite image from August 2008

(source: remonterletemps.ign.fr, retrieved September 2022; note the concrete support block at the center of the ring)

Knickebein klein

Fig. Kn-6-H: The concrete block at the center of Kn-6 - ca. 1985

(source: ref. 230Q19)


  • Location: Greny / France (1 km W of Greny, 15 km ENE of Dieppe). At the highest point in the area: 147 m ASL.
  • w.r.t Channel coast? w.r.t. down-town London?
  • Map coordinates (DMS / DD): 49°56'48.904"N 1°17'22.697"E ; 49.946918, 1.289638 (Google Maps, OpenTopoMap).
  • Notes: in modern days, no remnants visible in satellite images.



Fig. Kn-7-A: Recent topographic map of the Greny area

(source: www.geoportail.fr, accessed September 2022)


Fig. Kn-7-B: Part of aerial photo from RAF Photographic Reconnaissance Unit (P.R.U.) Sortie T/723 No. 649 of 1 Oct. 1941

(source: adapted from ref. 252N)


Fig. Kn-7-C: Site map based on RAF Photographic Reconnaissance Unit (P.R.U.) Sortie T/723 No. 649 of 1 Oct. 1941

(source: adapted from ref. 252N)

By early 1943, the entire site was fortified:


Fig. Kn-7-D: Aerial photos of the Kn-7 site during the spring of 1943 and on 28 April 1944

(source original photos: NARA (i.e., public domain); also used on p. 117 in ref. 90C)

There are circular structures on the northeast and southeast side of the site. They have roughly the diameter of the Knickebein ring. However, they are not decoy Knickebeins. For obvious reasons, decoys were never installed in close proximity of the "real" installation (e.g., the decoy of Kn-10 was located 9 km away). The round structure on the northeast side appears to cast a clear shadow, suggesting it may be a bunker. In aerial photos up to the early 1950s, remnants of the round structure on the northeast side are still visible. As this circle is much more prominent than the Kn-7 circle (see, e.g., the left-hand photo below), it is sometimes mistaken for the latter:


Fig. Kn-7-E: 1952 aerial photo of the Kn-7 site - orange overlay extracted from the left-hand image in Fig. Kn-7-D

(source full-size photo: remonterletemps.ign.fr, 29 April 1952; retrieved September 2022)

In the afternoon of 7 March 1944, the site was heavily bombed and "completely destroyed", as evident in the right-hand photo in Fig. Kn-7-D above:


Fig. Kn-7-F: German report (or offical war diary entry) of the attack on the Kn-7 site

(source:  NARA (i.e., public domain); also posted in 2016 in forum.axishistory.com)


  • Location: Mt. Pinçon (Le Plessis-Grimoult) / France (450 m ENE of Mt. Pinçon hilltop highest point (363 m, 1191 ft)), 30 km SW of the center of the city of Caen). 118 km SE of Kn-9, in the Calvados dept. in Normandy (famous for its "Calvados" distilled apple-cider brandy. The area was liberated by British 43rd Infantry Division around 7 August 1944, preceded by the 13th/18th Royal Hussars QMO cavalry regiment.
  • Map coordinates (DMS / DD): 48°58'19.21"N 0°37'12.00"W / 48.9720029, -0.6200012 (Google Maps, OpenTopoMap).
  • Notes: small Knickebein version.


high point Calvados


Fig. Kn-8-A: Recent opographic map of the Mont Pinçon area

(source: www.geoportail.fr, accessed September 2022)


Fig. Kn-8-B: Aerial photo from a low-altitude fly-by of the Kn-8 site, looking in northeasterly direction

(source: RAF, date and sortie nr. unknown; probably summer 1944)


Fig. Kn-8-C: Close-up of the Kn-8

(source: unknown; possibly attributable to Abbé Delacotte, probably 1944)


Fig. Kn-8-D: Site map of the Mont Pinçon area - based on photos from RAF Sortie T/114 on 17 June 1941

(source: adapted from ref. 252M)


Fig. Kn-8-E: Aerial photo of the Kn-8 site - 9 August 1947

(source full-size photo: remonterletemps.ign.fr, retrieved August 2022)


Fig. Kn-8-F: The two entrances and ventilation "towers" of the underground bunker that is marked in Fig. Kn-8-E

(source: ref. 230Q25 - date unknown)

The same type of bunker was constructed at Kn-10. See the Kn-10 section for more details.

Kn-8 is marked "zerstört" ("destroyed") on the 24 June 1944 update of a Luftnachrichten (Luftwaffe Signal Corps) map of the Allied Invasion Landing Area in Brittany - as are Kn-9 and Kn-10:


Fig. Kn-8-G: Kn-8, Kn-9, and Kn-10 are marked "destroyed" by 24 June 1944

(source: ref. 210X)


  • Location: Beaumont-Hague / France (1.5 km NE of Beaumont-Hague, 17 km WNW Cherbourg). Situated on a plateau at 495 ft ASL. Cotentin Peninsula in Normandy, where the Allied "D-Day" Invasion took place in in June of 1944. Position w.r.t. Kn-10, Be-4, nearest points/targets within range in (southern) England?
  • Map coordinates (DMS / DD): 49°40'24.4"N 1°51'09.2"W / 49.673444, -1.852556 (Google Maps, OpenTopoMap).
  • Notes: small Knickebein version.

First Kn station confirmed-located by aerial photograpy RAF (ref. 230C1, 230D1). Based on aerial photos, it was erected between late-June and mid-September 1940 (ref. 230D1, chapter 16)

Close to Kn-10, close to the world's largest reprocessing plant for spent nuclear fuel from light water reactors at La Hague (since 1976).


Fig. Kn-9-A: Recent topographic map of the Beaumont-Hague area

(source: www.geoportail.fr, accessed September 2022)


Fig. Kn-9-B: Kn-9 - construction nearing completion

(source: Bundearchiv image nr. 101I-228-0322-03 and wikimedia.org; photographer: Friedrich Springorum; also used in ref. 90B)


Fig. Kn-9-C: Kn-9 - construction nearing completion

(source: Bundearchiv image nr. 101I-228-0322-04 and wikimedia.org;  photographer: Friedrich Springorum; also used in ref. 90B)


Fig. Kn-9-D: Kn-9 - construction nearing completion

(source: Bundearchiv;  photographer: Friedrich Springorum; also used in ref. 90B)

The three photos above show Kn-9 towards the end of construction. Note the temporary scaffolding that is visible between the left- and right-hand half of the antenna system. Obviously there is a lot of construction material laying arond. Per the referenced source of the photos (in which the last name of the photographer is misspelled, by the way), they were taken in August of 1941. However, these photos are consistent with the below British aerial photos from September/October 1940, esp. the zoomed-in part in Fig. Kn-9-F. In the latter aerial photo, construction is completed and the scaffolding and construction material has been cleared away. Note that the wooden cabin below the center of the antenna system is not visible in the aerial photos. This is due to the obviously effective camouflage netting that is clearly visible in the photos above.


Fig. Kn-9-E: Near-overhead aerial photo from an RAF Photo Reconnaissance flight in September of 1940

(source: adapted from Plate 5a in ref. 230C1)


Fig. Kn-9-F: Oblique aerial photo from an RAF Photo Reconnaissance flight on 27 October 1940

(source: adapted from ref. 252J (1942); zoomed-in image is also used in ref. 90B (2015), which incorrectly states date as 24 Augus 1940)


Fig. Kn-9-G: Initial British site sketch - 18 Sept. 1940

(source: Fig. 2a in ref. 230C1 & 230D1)

The above sketch correctly shows front and rear antenna arrays. However, it does not show the "V" angle between the left- and right-hand half of the antenna system. Note the "scale?" markings inside the ring. These are probably the wooden ties (a.k.a. cross-ties, sleepers) onto which the steel track was laid, on top of the concrete ring.


Fig. Kn-9-H: Site map based on RAF PRU Sortie T/716 on 29 September 1941, revised on 19 September 1942

(source: adapted from ref. 252J; map is based on aerial photo from 29 Sept. 1914 in that ref.)

A large "underground facilities bunker" ("Unterstand") is marked in Fig. Kn-9-H above. Its construction started on 27 July 1940. Ref. 230Q17. The path to the entrances is from the route du Petit Parc road in the Digulleville community. The Germans surrendered the site to American troops late June of 1944, without a fight. The same type of large bunker was constructed at Kn-11.


Fig. Kn-9-J: The four entrances to the large earth-covered bunker that is marked in Fig. Kn-9-H (1946)

(source: ref. 230Q17)

Kn-9 is marked "zerstört" ("destroyed") on the 24 June 1944 update of a Luftnachrichten (Luftwaffe Signal Corps) map of the Allied Invasion Landing Area in Brittany - as are Kn-8 and Kn-10:


Fig. Kn-9-K: Kn-9, Kn-8, and Kn-10 are marked "destroyed" by 24 June 1944

(source: ref. 210X)


  • Location: Sortosville-en-Beaumont / France (25 km SSW Cherbourg). Normandy. Position w.r.t. Kn-9, Be-4, nearest points/targets within range in (southern) England?
  • Map coordinates (DMS / DD): 49°25'01.7"N 1°42'33.6"W / 49.41715, -1.70934 (Google Maps, OpenTopoMap).
  • Notes: small Knickebein version. The station was captured on 18 June 1944 by the US Army 60th Infantry Regiment (9th Infantry Division), who had crossed the Channel on June 9-10 1944 from Southampton, and landed at Utah Beach, 38 km due east of Kn-10.
  • Location of decoy Kn: 9.2 km (≈5.7 miles) due north of Kn-10; coordinates (DMS / DD): 49°29'58.344"N 1°42'45.3594"W / 49.49954, -1.71260 (Google Maps - no remnants visible)

Built in 1941 (ref. 230D1, caption of Plate 5c)

Close to Kn-9


Fig. Kn-10-A: Recent topographic map of the Sortosville-en-Beaumont area

(source: www.geoportail.fr, accessed September 2022)


Fig. Kn-10-C: Site map of the Kn-10 site - based on RAF PRU Sortie T/377 on 3 July 1941

(source: adapted from ref. 252L)


Fig. Kn-10-C: Zoomed-in aerial photo of the Kn-10 site - 11 June 1947

(source full-size image: ign.fr, retrieved September 2022)


Fig. Kn-10-C: Satellite image of the Kn-10 site - 2022

(source: adapted from Google Maps (image ©2022 CNES/Airbus, Maxar, retrieved 2022)


Fig. Kn-10-D: Drawing of the dugout concrete bunker facilities and photo of the entrances at the front

(source: adapted from ref. 230Q19; wall thickness ca. 3 m, overall footprint ca. 24x20 m)

Note: the function of the "batteries ?" and "transmitter ?" rooms varied, depending on whether a radar was added to the site (or replaced the Kn), and was operated from the bunker. In that case, one room became "Auswerteraum" - radar processing/interpretation room. The same type of bunker was part of the Kn-8 site (see Fig. Kn-8-F).

There is an eagle-with-swastika plaque over the right-hand entrance in the inset photo in Fig. Kn-10-D. At some point after the war, the swastika, most of the name, and "land 1941" have been chopped off.


Fig. Kn-10-E: Plaque above the right-hand entrance of the Kn-10 bunker

(source: Plate 5c in ref. 230D1; it reads "Constructed under Adolf Hitler in the fight against England 1941")

A decoy-Kn ("Schein Knickebein", typically a wooden contraption) was located 9.2 km (≈5.7 miles) due north of Kn-10, just south of the D23 road, 7 km east-southeast of Les Pieux:


Fig. Kn-10-F: Decoy Kn in aerial photo from RAF Photographic Reconnaissance Unit (P.R.U.) Sortie R/58 No. 43 on 14 Apr. 1942

(source: adapted from ref. 252L)


Fig. Kn-10-G: Remants of the decoy Kn in an aerial photo from 3 July 1947

(source full size image: ign.fr)

Kn-10 is marked "zerstört" ("destroyed") on the 24 June 1944 update of a Luftnachrichten (Luftwaffe Signal Corps) map of the Allied Invasion Landing Area in Brittany - as are Kn-8 and Kn-9:


Fig. Kn-10-H: Kn-10, Kn-9, and Kn-8 are marked "destroyed" by 24 June 1944

(source: ref. 210X)


  • Location: Saint-Fiacre / France (2.3 km NNE of Lanmeur 29620, between Chevrel and Kervern, 17 km ENE of Morlaix). Brittany. This is the westernmost Kn-station.At the highest point in the aera: 121 m ASL. Position w.r.t. nearest points/targets within range in (southern) England?
  • Map coordinates (DMS / DD): 48°39'58.31"N 3°43'48.7"W; 48.666198, -3.730194 (Google Maps, OpenTopoMap).
  • Notes: small Knickebein version.


Location vs Kn-8 and Kn-9

Knickebein Kn-11

Fig. Kn-11-A: Recent topographic map of the Saint-Fiacre area in Brittany

(source: adapted from www.geoportail.gouv.fr)

Knickebein Kn-11

Fig. Kn-11-B: Aerial photo from an RAF low-altitude fly-by on 23 July 1942 (Combat Film No. 1587 )

(source: adapted from ref. 252G)

Knickebein Kn-11

Fig. Kn-11-C: Site map based on RAF Photographic Reconnaissance Unit (P.R.U.) sorties in July 1940 - Sept. 1941

(source: adapted from ref. 252G; consistent with the aerial photos below)

Knickebein Kn-11

Fig. Kn-11-D: Oblique view from low-altitude fly-by of the Kn-11 site, Atlantic coast on the horizon - 1946/47

(source: adapted from ref. 230Q23)

The mast to the left in the photo above is claimed to be the 40 m tall mast of a "See-Elefant" radar system that was added to the site in 1944. At different times, the site included a FuSE 62A "Würzburg" radar with its large dish antenna, and a "Wassermann" radar system - though not necessarily at the same time. Photogrammatic analysis of the photo above suggests that the mast is actually about 60 m tall and is not pointed at the bottom. Based on this, it is the mast of a 1942 model "Wasserman S" radar - without the actual antenna elements. By the way, the "See-Elefant" by itself was not a complete radar system. It was only half of a bi-static radar system: the radar transmitter-only station ("See-Elefant", with a twin-mast (!) antenna) was not collocated with the associated radar receiver-only station ("Rüssel"). They had separate large antenna systems and were spaced by about 1 km. Neither antenna system had a mast that looked like the one in the photo above...

The next photo shows the four entrances of the "underground buildings" bunker that is marked in Fig. Kn-11-C above and is clearly visible in Fig. Kn-11-E. Conbined, they span about 20 m (≈66 ft). The earth-covered structure measured about 40x20 m (WxD). The camouflage painting pattern on the exterior concrete surfaces and inside the entrances is dark orange. It is still visible in our time, though primarily on the inside. The same type of large bunker (incl. camouflage painting) was constructed at Kn-9.

Knickebein Kn-11

Fig. Kn-11-F: Entrance to the power-generator/transmitter/radar processing bunker near the Kn installation

(source: ref. 230Q19 - ca. 1985, color photo inset: adapted fom patrimoine.bzh - ca. 2002)

A decoy-Knickebein (“Schein Knickebein”, typically a wooden contraption) was located 3.5 km north of Kn-11, at Saint-Jean-du-Doigt (see Fig. Kn-11-A above):

Knickebein Kn-11

Fig. Kn-11-G: Kn-11 and the decoy Kn marked on a Luftnachrichten (Luftwaffe Signal Corps) map

(source: adapted from ref. 210H, map update of 6 July 1944)

Knickebein Kn-11

Fig. Kn-11-D: Aerial photo of 16 May 1966

(source full-size photo: remonterletemps.ign.fr, retrieved September 2022)


  • Location: in the far southwestern corner of Germany, near the German-Swiss-French border.  More precisely: on the Dachsig Berg height (468 m ASL), between the small villages of Maulburg and Adelhausen. This is about 8 km (5 miles) east-northeast of the town of Lörrach and 16 km (10 miles) northeast of the large city of Basel (Bâle) in Switzerland.
  • Map coordinates (DMS / DD): 47°38′2.68" N, 7°45′47.8" E; 47.634077, 7.763269 (Google Maps, OpenTopoMap).
  • Notes: large Knickebein version. The station was originally installed on the isle of Borkum in the far northwest of Germany, where it used the frequency 32.0 MHz and had a pointing direction range of 270° ± 45°. Ref. 230Q8.


Knickebein large

Fig. Kn-12-B: Large Knickebein Kn-12 at Maulburg near Lörrach/Germany - without antennas

(source: ref. 230Q2)

This station was originally constructed on the isle of Borkum (roughly half-way between Kn-2 at Stollberg/Bredstedt and Kn-4 at Kleve. During the winter of 1939/1940. The station was declared "abandoned" in October of 1941 (BAMA RL 19-7/141). Per ref. 230Q2: terrain was aquired by the Reichsfiskus (national Treasury; unclear if Reichsfiskus/Heer or /Luftwaffe) in 1941. Concrete ring ca. 1 m high.

At the Yalta Conference in February of 1945, the major Allied powers - USA, Britain, Soviet Union - decided to divvy up Germany into three occupation zones. Despite the fact that France had no particularly significant part in the defeat of Nazi Germany, the southwestern part of Germany, bordering on France, was later turned into a fourth occupation zone. The French also got a small zone in southeastern Germany (on Lake Constance, bordering on their zone in western Austria), and - for prestige reasons - a small sector in West-Berlin. The French occupation forces destroyed the Kn-12 installation in 1948 (ref. 230Q15).

Knickebein large

Fig. Kn-12-C: 1968 aerial photo of Kn-12 - inner & outer ring clearly visible, with 3 barracks & acces path to the right

(source: Landesarchiv Baden-Württemberg/Staatarchiv Ludwigsburg)

If you look closely and carefully at the next photo, you will see the overgrown remnant of the concrete central support block. Based on its size relative to the outline of the inner track (vaguely visible just inside the yellow circle), the block measures 2x2 m (≈6.6 ft) - about 1.5 times the size of the support block of the Small Knickebein.

Knickebein large

Fig. Kn-12-C: 1CA. 2018 aerial photo of Knickebein Kn-12 - the inner track and central support block are still visible

(source: adapted from ref. 230Q1 (= the Knickebein page of christianCH, retrieved September 2022; used with permission)


  • Location: Noto, about 31.5 km southwest of the city of Siracusa, in the southeast corner of the isle of Sicily. 9 km NW of center of Noto village. About 540 m ASL. Panoramic view across the southern Mediterranean, in particluar towards Malta and beyond.
  • Map coordinates (DMS / DD): 36°55'52.4"N 14°58'47.9"E / 36.9312287, 14.979982 (Google Maps, OpenTopoMap).
  • Notes: small Knickebein version, construction was never completed. ??? Intended for targets in North Africa?

Sicily was liberated by Allied forces during Operation Husky in 1943. The Noto area was taken by the British infantry around 11 July 1943.

Note: the Kn station nearest Kn-13 is Kn-12, at over 1300 km. So, the range of Kn-13 did not overlap with that of any other Kn. It is not known if any additional small Kn stations were planned, to enable marking of targets in and around the Mediterranean.

Knickebein small

Fig. Kn-13-B: Aerial photo of the Kn-13 site - Villa Olivia on the far left

(source: ref. 90B, p. 21)

Track: I-beam clamped onto wooden ties, in rail bed of gravel / crushed rock, on top of the concrete ring foundation.

Knickebein small

Fig. Kn-13-C: Kn-13 during construction - Villa Olivia in the background

(source: ref. 90B, p. 21)

Knickebein small

Fig. Kn-13-D: Looking in both directions along the center of the truss cage below the antennas

(source: ref. 230Q24; in the left-hand image, note the two counterweights for keeping tension on cables)


Zyklop (English: "Cyclop"):

Ref. 6G §28: "This was the latest form of the well-known Knickebein, working on 30 - 33,3 mc/s and received by E.B.L.3 in the aircraft. It was a mobile station which could be fully erected into operation within a week. §29.

Ref. 6G §30. The 120 W ground transmitter was called the ???? which gave a beam 0.5° wide and a range of 300 km at a height of 5000 meters. The Zyklop systems had been made use of on the Russian front up to the end of the hostilities. [--> AS 2, AS 3 ransmitter; ref. 39B, 39D, 39H]

Ref. 2C1: 1940/41, a.k.a. "Zyklopfeuer" FuSAn 722 ground station + FuBl 1 / FuBl 2 airborne radio set.

Ref. 2C3, p. 68

Ref. 2B p. 68; p. 45 (developed 1940/41), p. 171 (rad pattern)

ref. 2A p. 133  beacon transmitter: Lorenz 120 W VHF AS 3 beacon transmitter (ref. 39B, 39H), trailer mounted,  + 2 vertical dipoles on wooden masts, spaced by 14 m (≈ 46 ft; ca. 1½ wavelength at 30-33.3 MHz), 1150 tone midulation (standrad), keyed in the standard 1:7 rhythm; switching the dipoles alternatingly in-phase/counter-phase (180° out of phase) created 4 equisignal beams, ca. 0.3 beam width, one of four used as guide beam, range ca. 300 km @ 5000 m altitude (≈ 16.5 kft). On the western front only Zyklop-1 [note: Z-6 near Brest per ref. 210E/210F map): active, roughly July-December 1944, p124 (1x on map: north of Pont-Audemer (SW of Honfleur & Le Havre (ref 2A, p. 133 + map p. 124); usually pointing in WNW direction (Channel area beyond Cherbourg); used for dropping sea mines at a predetermined distance from the beacon (determined roughly by stopwatch timing after getting light signal from ground when overflying the beacon).

Ref. 6D, §41: It [Zyklop] was developed by Dr. Künhold at Köthen [see X-system section; add bookmark link to there].

Ref. 38A [12/12/45]: PoW report. derived from Knickebein (late 1943). System extensively used by Fliegerkorps IV in Russia and was to have been set up on the Channel coast for attacks on England, but the General [Martini] was not sure whether it was actually used. Range of 300 to 350 km as against the 450 km of Knickebein. Developed by Dr. Künhold at Köthen

Ref. 185C. : useless as ref.

Zyklop Zyklopfeuerl

Fig. Z-1: Installation and radiation pattern of the Zyklop system

(source: adapted from ref. 2A and 2B)

Map icons: Ref. 210D, 210E, 210F, 201Y: in Ukraine, Greece, Poland, Belarus, Lituania, France, Belgium/Netherlands?. Range: marked as 350 km. Ref. 210A (no nmbr, nr Lemberg/Lviv/Ukraine), 210D (no nbr, near Athens/Greece) 210F (no nbr, nr Goldap/Poland), 210D (nr Kischinew/Chişinuă/Moldova), 210F(no nbr, nr Litzmanstadt/Łódź /Poland), 210D (no nbr, nr Pinsk/Belorus), 210F (no nbr, nr Krakau/Kraków/Poland), 210E + 201F (Z-6, nr Brest/France), 210C & 210E (Z-8, nr Boulogne/France, Abbau 5-Sept-44), 210C + 210E (Z-11, nr Boulogne/France -1-Aug-44, Abbau 5-Sept-44), 210E (Z-11, nr. Tilburg/The Netherlands; 1-July-44)


Ref. 6G §28: A still more mobile unit, known as the Bock-Zyklop, has been introduced.[-_> operational!] This could be set up in three days and could be adapted for use on the FuGe 16 frequency [ = ???? MHz, VHF] although as yet, according to documents, no visual indicator for the FuGe 16 had been developed. [--> not compatible with Kn or Zyklop!!!!]

Ref. 2B, p. 68, 2A p. 133/134: switchable to FuG 16 receiver 38-42 MHz freq range. Audio only, no AFN instrument!


Ref. 230T2, p. 136/137: December 1943 - Jan 1944, Y-Service stations intercepted German radio telephony (R/T) traffic on the 31.2 MHz Knickebein frequency, referring to "Ottokar", mentioning British bombers and the Ottokar-direction] and beam signals on that same frequency, with 1150 Hz tone modulation; traced to the Kn-3 area in The Netherlands. Hence, it was assumed that the Kn system was used in a defensive capacity as an aid to night fighters. The Airborne Cigar (A.B.C.) jamming transmitters on the three No. 101 Squadron aircraft were modified to also cover 31.2 MHz, creating interference in the 30-33 MHz band.    p. 137: full number of Kn stations used for "Ottokar" purposes never determined by the British, but at least Kn-5 in The Netherlands was also used for that purpose. Additionally, early 1944, "Rayon" (high power transmitter, with Jostle-type modulation) at No. 80 Wing station Mundesley (ca. 25 km NW of Norwich, ca 220 km due west of Kn-3, ca. 250 km NW of Kn-5) used for jamming the Ottokar R/T.

I.e., two aspects: using the Kn beam, and using the Kn radio frequency for R/T "Running Commentary" annoucements ["Durchsage von Luftlagemeldungen".

There are some references (e.g., ref. 230R3, 230R4) to Knickebein stations (in particular Kn-3) being reactivated starting December 1943 - not for guidance of Luftwaffe bombers, but guidance of fighter aircraft for intercepting Allied bombers arriving from Britain. German codename: "Ottokar".

Trenkle "Die deutschen Funk-Navigations-und Funk-Führungsverfahren bis 1945", pp. 154, 155; Trenkle "Funkfuehrungsverfahren" pp. 132, 197.

I have not yet been able to confirm this with original German documents. E.g., there is no mention of such a procedure in the Kriegstagebuch (KTB, War Diary) of the I. Jagdkorps (1st Fighter Corps, responsible fighter units within the Reich). Technically, it would have been possible to point a Small Knickebein beacon at a bomber stream, scramble fighters on a vector to intercept the beam and inform the fighters of the direction of the beam. The 1939/1940 Lorenz rotable beam system  "Karussel" was actually developed for that purpose, though only two stations were built, primarily for experimental purposes.


EXPAND BRIEFLY: Terminoligy. Detection, intercept, intelligence, countermeasures, electronic warfare (EW). Sometimes no interference with enemy R/T, W/T, RadNav, so as to use the enemy's system (RadNav) or get intel. Terminology.

I highly recommend ref. 230T2 - excellent overview. 100 Group motto "Confound and Destroy" (ref. 33).

On 21 June 1940, an aircraft of the RAF Blind Approach Training & Development Unit (BATDU, replaced several months later by the Wireless Intelligence Development Units, WIDU) intercepted Knickebein signals with a Hallicrafters model S-27 VHF superhet VHF receiver (27.8 - 143 MHz; US reeciver, since no British off-the-shelf reeciver could cover the frequency range), and determined the direction of their source. Ref. 5, 230D1. During the winter of 1940/41, the Knickebein system became increasingly unreliable and unusable over Britain, due to jamming by the British. Reports on "spoofing" and "beam bending" by the British being undetected and effective are contradictory (e.g., ref. 5 vs. §27-28 in ref. 6D). The jamming tone pulses sounded different from the true Knickebein pulses (§28 in ref. 6A), possibly due to better keyclick suppression in the jammer. Also, the British jamming systems were incapable of synchronizing to the Knickebein pulses, hence, their jamming signals created easily detectable "wailing" beat tones. The system continued to be used in the lead aircraft ("Pfadfinder") for navigation towards the target, but those now relied on the X-System to locate and mark the actual target.

Knickebein had the British codename "Headache". Jammers "Asprine". ref. 6B, 230A, 230C, 230D1, 230E1, 230F, 230G, 230Q18, 230T1, 230T2, 230T3, 230T4, 23=U1.

The British "Wireless Interception" service (WI-service, phonetically abbreviated to "Y" service) was responsible for the monitoring of enemy radio transmissions. The radio-intercept stations were known as Y-stations. The service dates back to WW1, and was run by the Royal Navy: Naval Intelligence Department I.D. 25, also known as "Room 40". In 1920, the service was transferred from the Navy to the Foreign Office (FO), and "Room 40" was renamed to Government Code and Cipher School (GCCS). In 1939, the GCCS moved to Bletchley Park (BP) in Milton Keynes/Buckinghamshire (about 80 km / 50 miles north-west of London), and was renamed to Government Code Head Quarters (GCHQ). Ref. 35.

During WW2, the Y-service covered radio-telephony, Morse telegraphy, and Non-Morse (NoMo) transmissions, whether encrypted or not. NoMo traffic included teletype/teleprinter and Hellschreiber. The Y-stations were operated by a number of government agencies (the branches of the armed forces, the Metropolitan Police, and the General Post Office) and the Marconi company. Some stations only had direction-finding (D/F) capability.

During the course of WW2, the service grew from a few Y-stations, to a global network of small and large stations. They were located in the UK, the Middle East, Far East, North Africa, mainland Europe, and offshore. Intercepted encrypted signals were either analyzed locally, or transferred (by dispatch riders on motorcycle or via teleprinter) to BP. Sometimes BP is referred to as "Station X" (i.e., station nr. 10), though that actually refers to a small Special Intelligence Service (SIS) wireless station (MI6 Section VIII) that was originally located at Barnes in west London (south of the Thames), and temporarily moved to BP.

Ref. 230Q18: Beam bending stories not true! Standard method was to transmit dashes only, in an attempt to create false equisignals. However, they were not (!) synchronized to the real Knickebein signals. Interviewed German bomber crews (also) stated that the real Knickebein signals were easily heard through the low-power jamming. Post-war interviewed Kampfgruppe 100 Pfadfinder crews even stated that they were never aware of British jamming efforts against the X-system. Yes, the Germans abandoned the Knickebein system MM-194Y. The British correlated their success [in terms of what?] with the actual jamming activities/attempts. But: positive correlation by itself does not imply or prove cause-and-effect - but it makes for nice propaganda.

No. 80 Wing -formed in July 1940; No. 80 Wing Operations Record Book (ORB); Blind Approach Training and development Unit (BATDU) at RAF Boscombe Down [formed to train instructors in the use of the Lorenz Blind Landing System] - used in 1940 to investigate the Knickebein system, disbanded 30 September 1940, immediately replaced by the Wireless Intelligence Development Unit (WIDU), only to be absorbed into No. 109 Squadron some two and a half months later. .... Radio Counter Measures (RCM) section formed within the Signals Directory at the Air Ministry, using information from the Wireless Intelligence Service (WI = "Y"). "... more-experienced navigators could work their aids to navigation through interference in cerain circumstances ,but navigtaors of this competency were not available in large numbers" "...countermeasures could not nullify the German use of radio aids to bombing" pp. 29-32, 54 in Ref. 230T3

TO BE ADDED/EXPANDED. Ref. 230F1-230F9: general, countermeasures, British view.

On 7 October 1940, No 80 Wing became the first Royal Air Force electronic warfare unit and was tasked with spoiling the enemy bombing aids. No 100 Group was established soon afterwards, with the duty of deceiving German radio and radar defence services.

In September of 1941, the Luftwaffe aircraft receivers were upgraded from FuBl 1 to FuBl 2, which supported a large increase in the number of available frequency channels in the same band, and a range of 600 km at 6000 m altitude (20 thousand feet).

230T2 Ch 4, Knickebein mods, spoof, rotate.

230T2 Ch 10 p. 136/137: Ottokar, British countermeasure "Rayon" against Ottokar R/T [high-power TX with Jostle-type modulation], starting January 1944. German mesures to overcome jamming of R/T running commentary included using women R/T operators/speakers, whose higher-pitched voices were harder to jam.

Of course, whereas German aircraft used Knickebein beacons to navigate onto a course-line to a target location or area, and back, the British could use those same beams to navigate to, and destroy those beacons!

ADD Knickbein specific RCM here, make dedicated page for countermeasures at  RadNav level, or at section on Bernhard/bernhardine pages (also using ref, 230T2)?

ADA081486: timeline, based on RVJ "Wizard War".


  • Transmitter of the large Kn: manufacturer, model/type, output power, design vacuum tube types, ...
  • Did the cable(s) from the transmitter to the antenna system enter the concrete support block through the bottom or the side?
  • Antenna arrangement and transmitter of "Zyklop" and "Bock-Zyklop".
  • Ref. 230Q10 states that antenna azimuth correction values were marked on the large concrete ring of the Kn-4 station.  It is unclear/unknown where and how these corrections were marked on the concrete ring.
  • The location/number of the following Kn station is unconfirmed:
Knickebein small

Fig. Kn-TBD: Small Knickebein - location and date unknown

(source: unknown)

If you have any info on any of these items, please contact me.


Note 1: due to copyright reasons, this file is in a password-protected directory. Contact me if you need access for research or personal study purposes.

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