• [Introduction]
• [Telefunken UHF rotating beam systems]
• [Telefunken transition from UHF to VHF]
• [Development of VHF "Bernhard/Bernhardine"]
• [System characteristics]
• ["Bernhard 30" / "Bernhaube"]
• [Patents]
• [Unknown/unclear aspects]
• [References]

• [FuG120 "Bernhardine" airborne Hellschreiber printer system]
• [FuSAn 724/725 "Bernhard" ground station]
• ["Bernhard" station locations]
• [Radio direction finding, location, and air navigation through WW2]

By May of of 2020, the "Radio direction-finding, location, and air navigation through WW2" section of this page had become too large, which caused long download times for some users. I decided to move it to a separate page. Please continue to use the (unchanged) list above and update your bookmarks, if necessary.

©2004-2023 F. Dörenberg, unless stated otherwise. All rights reserved worldwide. No part of this publication may be used without permission from the author.

Latest page update: 1 January 2023 (added ref. 290A-290C and associated text; minor edits)

Previous updates: April 2022 (moved "Bernhaube" notes in "Unknown/unclear aspects section to new "Bernhaube" section).June 2021 (added ref. 175B); April-May 2020 (moved the entire radio direction finding/location/navigation section to a separate page); January-February 2020 (added Fig. 3B, Fig. 42, ref. 244A-244Q, ref. 25, 187A-187E, Fig. 2 and text, patent table-3, grouped subsets of references). August-November 2019 (added hi-res version of ref. 15, added ref. 230B, 230C, 230D, 241, 244D-244J, 247, 254, 259).

INTRODUCTION

The "Bernhard/Bernhardine" system is a radio-navigation system that was used by the Luftwaffe to assist fighter aircraft with the intercept of enemy bombers. The system went into operational service late 1941. Ref. 1, 2A, 2B, 5, 6, 7A, 8, 164 (p. 30), 181, 183, 185G. As shown in Figure 1, the system comprises a beacon station and a Hellschreiber printer-system in the aircraft:

• FuSAn 724/725 "Bernhard" is the VHF rotating directional-beacon ground-station (UKW-Richtstrahl-Drehfunkfeuer). It continuously transmits the station identifier and the momentary antenna azimuth (bearing) in Hellschreiber-format. Instead of the azimuth, some stations could also broadcast short "Reportage" text messages, with instructions for intercepting inbound enemy bombers. Note that the system was only operating (thus rotating) when enemy aircraft were in range and fighter planes had to be directed towards them.
• FuG 120 "Bernhardine" is the airborne Hellschreiber system that prints the data stream from the selected Bernhard station. Hence, it is a "UKW-Richtstrahl-Drehfunkfeuer-Empfangszusatz mit Kommandoübertragung". That is, an accessory for a (standard) VHF directional-beacon radio receiver, that also provides command uplink (if the ground-station is equipped for that).

As it operated in the 30-33.1 MHz frequency range, it is by definition a VHF system (30-300 MHz). However, from a radio propagation point of view it behaves more like an HF system (3-30 MHz).

Fig. 1: "Bernhard/Bernhardine" = "Bernhard" ground-station + "Bernhardine" airborne Hellschreiber printer system

(click here for a full size image)

The "Bernhard" ground-station has a rotating antenna system that consists of two antenna sub-systems (both dipole arrays):

• One dipole array has a single-beam radiation pattern (green in Figure 2 below). It is used to continuously transmit data in Hellschreiber-format: either the station identifier and momentary antenna azimuth, or a short "Reportage" text message. The centerline of the beam is the azimuth of the antenna.
• The second (larger) antenna system comprises two dipole arrays and has a twin-beam radiation pattern (purple in Figure 2). The pattern has a sharp null between the two beams. This null is aligned with the maximum of the single-beam. This antenna sends a continuous signal (AM modulated tone).

Fig. 2: Concept of the Bernhard/Bernhardine radio-navigation system

The "Bernhardine" Hellschreiber-printer in the aircraft prints two parallel tracks on a paper tape, see Figure 2:

• The lower track prints the compass scale that is transmitted via the single-beam signal. Each passage of the rotating beam illuminates the aircraft during several seconds. The actual azimuth of the aircraft ( = momentary compass direction as seen from the beacon station) is included in the section of the compass scale that is printed during this short period. This is a two-digit value for every ten degrees of azimuth (as is done to identify the magnetic heading of runways at aerodromes), and a tick mark for each degree. A station-identifier letter is also printed every 10 degrees ("M" in Figure 2). The azimuth (bearing from the beacon) was referenced to True North (QTE, "Rechtweisend"), see §10 in ref. 14, ref. 15, p. 8 in ref. 183. These days, aeronautical radio-navigation beacons are not referenced to True North, but to the regional Magnetic North (QDM; exception: Canada's Northern Domestic Airspace, a polar region).
• The upper track prints the (clipped) signal strength of the received continuous signal of the twin-beam antenna. Hence, the printed pattern shows the two lobes of that twin-beam, with the sharp null in between. This accurate V-shaped null points at the exact azimuth value that is printed in the lower track. Determining the exact minimum is a basic Radio Direction finding (RDF) technique.
• The paper tape only moves when a sufficiently strong signal is received (typ. 3-5 sec per 30 sec revolution of the beacon). So, the print-out does not need to be interpreted immediately.

To the best of my knowledge, no original "Bernhard" audio recordings exist today. So I have simulated the sound of a transmission. The recording below comprises two beam-passages: once without the information in Hellschreiber-format (i.e., only the constant 1800 Hz tone), and once the constant tone plus the constant stream of 2600 Hz Hellschreiber-pulses. Note: the second simulated beam passage also includes a 10 kHz tone. The 1800 and 2600 Hz tone signals were transmitted with two separate AM transmitters, with 10 kHz spacing between their carrier frequencies. The 10 kHz tone at the output of the radio receiver is the normal byproduct of demodulating those two simultaneous AM signals, as explained in the "Filter Unit SG 120 (Siebgerät)" description section.

Simulated sound of two "Bernhard" beam-passages - without & with Hellschreiber tone pulses

Unlike typical radar systems, "fighter guidance" navigation beacons such as Bernhard-stations were only operational on demand! E.g., around the Allied invasion of Normandy on 6 June 1944 ("D-Day", "Operation Overlord"), the British observed the Bernhard station at Le-Bois-Julien (France) with a 10 cm (3 GHz) radar in East Sussex: no rotation on June 1^st, 6^th, 7^th, and 9^th. The antenna rotated for a period of 2 hours 20 min during night of June 2^nd, 4 hours 20 min during evening of June 3^rd, 4 hours + 1 hour 25 min + 20 min during the early morning and early evening of June 5^th, 2 hours 50 min late afternoon of June 8^th. Ref. 173A.

During 1942-1944, RAF 192 Squadron (§9.3 in ref. 175A, p. 2 & 3 in ref. 175B) and the British/American Noise Investigation Bureau (ref. 173A-173E) investigated the Hellschreiber signals that were transmitted by "Bernhard" beacons. The British Foreign Office Wireless Intercept station ( = WI-station = Y-Station) at Knockholt (near Sevenoaks, in the countryside, about 30 km southeast of the City of London) assisted RAF 192 Squadron with knowledge about the Hellschreiber system, its reception, and the required tone-filter. The British and US military and intelligence referred to this system as "Windjammer" (p. 4.09 in ref. 13, ref.172, 173, 174).

The "Bernhard/Bernhardine" system is the final evolution of the Telefunken Rotating Beacon system. The remainder of this page describes the historic background of such radio navigation beacons, starting with the original invention during the early 1900s, and the subsequent development phases leading up to the "Bernhard/Bernhardine" system in 1941. A summary of other German beam systems is provided on this page.

TELEFUNKEN UHF ROTATING-BEAM BEACON SYSTEMS FOR RADIO-NAVIGATION

By 1934-1935, reasonably efficient UHF transmitters had become practical. Therefore, during the spring of 1935, the Telefunken company decided to develop the "Telefunken-Drehfunkfeuerverfahren", a new Telefunken rotating radio-navigation beacon system (ref. 181, 183). Construction of a UHF test/evaluation beacon started in August of 1935. It operated at a frequency of 300 MHz (λ = 1 m). It was installed at a Telefunken test site near Groß-Ziethen, just north of Berlin-Schönefeld airfield. That site was also used to test radar systems, UHF radio-relay links, and high-power PA loudspeakers. These days, the name of the town is spelled "Großziethen", not to be confused with another Groß-Ziethen, 75 km to the northeast. The UHF transmitter had a an output power of 1 watt (ref. 2B). The UHF receiver was located on the tower of the nearby Telefunken plant in Berlin-Oberschöneweide, about 8 km (5 mi) to the northeast. The output signals from the receiver were fed back to the transmitter site via regular phone lines. In December of that year, the beacon was demonstrated to the Reichsluftfahrtministerium (RLM, the German Air Ministry). The antenna system comprised two side-by-side arrays of two vertical dipoles, placed in front of a reflector surface (see Fig. 4 below). The two sub-arrays were fed 180° out of phase. This creates a radiation pattern with two slightly diverging main lobes, with a sharp null between them.

Fig. 4: The UHF beacon at Groß-Ziethen

(source: Fig. 16 in ref. 181)

The test-setup achieved an excellent accuracy of better than 0.1°, based on the received signal amplitudes that were captured with a strip-chart recorder. Fig. 5 shows a plot of the amplitude of the received signal while the antenna rotates, i.e., while the two lobes of the radiated pattern repeatedly sweep by the receiver antenna. The plot clearly shows the null of each sweep, flanked by the two main lobes of the radiation pattern:

Fig. 5: Signal-amplitude plot of the Groß-Ziethen beacon - showing deep null of the antenna radiation pattern

(source: Fig. 17 in ref. 181)

Based on the demo, the RLM ordered three prototype beacons in 1936. They were installed at the following locations (ref. 181):

• Rechlin, about 100 km north-northwest of Berlin. The Rechlin site became operational late August of 1918 as Flieger-Versuchs- und Lehranstalt am Müritzsee (Flight Test & Training Institute at Lake Müritz), upon a November 1916 initiative of the Deutsches Kriegsministerium. At that time, the Flieger-Funker aviation-radio activities were done at Lärz, one of the nearby airfields. As a consequence of the Treaty of Versailles (June 1919), the installations were dismantled in the early 1920s. However, contrary to the Treaty, flight testing in the Weimar Republic (Weimarer Republik, the unoffical designation of the German state 1918-1933) resumed, and construction of a flight test aerodrome started in Rechlin in 1925. The required land was bought by the state, under the guise of a specially founded civil flying club, the Luftfahrtverein Waren e.V.It also operated the aerodrome when it became operational during the summer of 1926. Test activities were handled by Abteilung M (Department M) of the Deutsche Versuchsanstalt für Luftfahrt e.V. (DVL, the German Aviation Test Institite) in Berlin-Adlershof. Towards the end of 1929, the Reichsverband der Deutschen Luftfahrt-Industrie (RDL) took over the site, pressured by the Truppenamtes der Reichswehr. The site was given the cover name RDL Erprobungsstelle Staaken. Upon the 1933, Rechlin quickly became the largest Erprobungsstelle der Deutschen Luftwaffe ("E-Stelle", official Luftwaffe test site). Ref. 19, 241. Construction of the UHF radio-navigation beacon started late 1936. Beacon system development and tests were conducted by the Abteilung Funkforschung (Abt. F, Department F), who covered "Hochfrequenzforschung und Leitstrahlverfahren" (RF-research and flight guidance beams).
• The Telefunken test site near Mietgendorf (near Trebbin and Glau), about 35 km southwest of down-town Berlin. This beacon was constructed during the spring of 1937.
• On the Wasserkuppe, the highest point of the Rhön mountain range in central Germany. This was a camouflaged beacon. Using camouflage is addressed in the 1936 Telefunken patent 767354 (line 49-57).

Fig. 6: Location of the three 1936/37 UHF test stations

(modern national borders)

Fig. 7: The beacon at Rechlin (left) and Mietgendorf

(source: Fig. 18 & 19 in ref. 181)

Note that in this generation, the antenna system had been expanded compared to the original system of the beacon at Groß-Ziethen. The latter had two side-by-side sub-arrays of two vertical dipole antennas each (Fig. 4 above). However, now, there are two sub-arrays of five vertical dipoles each. This makes the main lobes of the radiation pattern narrower, and the null sharper. Above it, there now is a separate array, also of five vertical dipoles. See the left photo in Fig. 7 above. This upper array generates a radiation pattern with a single main lobe. This lobe coincides with the null between the main lobes of the lower array. The beacon now also has two 20 watt UHF transmitters, one each for the top and bottom array, instead of a single 1 watt transmitter.

Fig. 8: The camouflaged beacon on the Wasserkuppe

(source: Fig. 20 & 21 in ref. 181)

During 1936/37, flight test were performed by both Telefunken and the "E-Stelle" at Rechlin. The next photo shows an early equipment set, used in the test aircraft for the reception of the UHF beacon signals, and capturing signal strengths with a 2-channel wax-paper plotter.

Fig. 9: First Telefunken airborne receiver and 2-channel plotter for the UHF beacon

(source: Fig. 22 in ref. 181)

The plotter has to plot two traces, as the beacon now transmits two signals: one via the upper antenna array (single lobe) and one via the bottom array (twin-lobe with sharp null):

Fig. 10: Radiation pattern of the antennas for the pointer signal (lobes D) and the compass scale (lobe K)

(Left: Fig. 2 in patent 767354, right: Fig. 1 in patent 767523)

The single lobe is used to continuously transmit the momentary azimuth value of the antenna's pointing direction (= centerline of the single lobe = null of the twin-lobe). The two signals are plotted simultaneously as two parallel traces. The passage of the null causes a narrow dip in the associated upper trace of the plotter. This used as a pointer ("Zeiger") for the azimuth ("Skala" compass scale) value information printed in the lower trace.

This is the essence of the Telefunken rotating beacon system!

In this early version of the system, the plotted azimuth trace resembles that of a Morse "undulator" recorder. The transmitted pulses were generated with an optical encoder disk that rotated with the antenna. A simple encoding format was used: a sequence of short and long pulses for every 10° section of each compass rose quadrant. It is basically an adaptation of the numbers 0 - 9 in Morse code. However, here, each individual dot and dash marks 1° of the compass scale. No dash is used for marking 9°, 19°, ... , 89°. The resulting pause is used to identify the start of the next 10° section:

Fig. 11: Encoding of the compass rose on the optical encoder disk

(source: adapted from Fig. 5 & 6 in the 1936 Telefunken patent 767354)

When the beams of the rotating beacon sweep by and "illuminate" the receiving aircraft, the following 2-trace plot is generated:

Fig. 12: xxx

(source: adapted from Fig. 4 in the 1936 Telefunken patent 767354)

Note how the signal-strength trace clearly corresponds to the two main lobes D and the associated null of the antenna radiation pattern (Fig. 10 above).

An example of an experimental 2-trace plot is shown in the next Figure. It is from a 1937 Telefunken test flight that recorded the signals from the Mietgendorf beacon, while flying near the city of Breslau at an altitude of 4000 m (13 thousand feet). This city is situated about 300 km (190 miles) southeast of the beacon near Berlin. At the time, Breslau was in the Lower Silesia ("Niederschlesien") region of the Reich. After the war, this area (and others) became part of Poland, and the name of the town changed to Wrocław (Wrazlaw). There were two Luftwaffe airfields there: Breslau-Gandau (Junkers aircraft factory, pilot school Flugzeugführerschule A/B 71 added in 1938), and Breslau-Schöngarten (home of Luftkriegsschule LKS 5, "Air War School nr. 5").

Fig. 13: 2-trace plot of a Telefunken test flight during the summer of 1937

(source: Fig. 23 in ref. 181)

The conclusion from numerous measurements was an achieved accuracy of about ±0.3°, primarily caused by uncertainty about the real position of the aircraft: the accuracy of the "beacon + airborne system" was determined to actually be around ±0.1°. Range with the 20 watt transmitters at 300 MHz was about 300 km (190 miles) at an altitude of 4000 m (13 thousand feet). At lower altitudes, the achieved beacon range was consistent with visual range. Extensive flight tests with the beacon on the Wasserkuppe early 1938 had similar results: a range of 270 km at 2000 m, 320 km at 3000 m, and 340 km at 4000 m. As shown in Fig. 8 above, the antenna system of the Wasserkuppe beacon was mounted on a tower. Range with the antenna installed closer to ground level (as was the case at Rechlin and Mietgendorf) was about 80 km smaller. The average accuracy was ±0.25°, with outlier cases as high as ±0.5° and one of ±0.75°. Note that the objective was an accuracy no worse than ±0.1°... These achieved system-level results ( = beacon + radio wave propagation + uncalibrated aircraft equipment) were a very significant improvement in radio direction-finding (RDF) accuracy. The mentioned Telefunken and E-stelle tests confirmed that the performance of the UHF system was unaffected by weather, twilight and night-time effects, and mountain effects. In all, sufficient reasons to further develop the system and introduce it into service.

After the successful proof-of-concept, attention was focused on presenting the bearing (azimuth) value in a form that was directly readable by anyone, and did not require interpretation of a squiggly undulator trace. For the given antenna configuration and dimensions, an accuracy better than ±0.3° was not achievable. Hence, an indicator device did not have to have an accuracy much better than that. This cleared the way for using a 2-channel Hellschreiber-printer instead of a 2-channel strip-chart recorder:

Fig. 14: First two-trace Hellschreiber print-out on paper tape of the UHF beacon signals - fall of 1937

(source: Fig. 24 in ref. 181)

One-channel Hellschreibers for civil/commercial and military had been around since the early 1930s. It was robust off-the-shelf technology for making a direct-printing system. A Hellschreiber printer comprises an inked spindle that is placed across, and slightly above, a moving paper tape. Below the paper tape is an electromagnet with a hammer blade. When the magnet is energized, the hammer pushes the paper tape against the continuously turning spindle. This causes a line segment to be printed across the paper tape. The length of the printed line depends on the amount of time that the electromagnet is energized. See the "How it works" page. Basically, it prints a line of symbology (text, or - as is the case here - a compass rose scale), that is transmitted to the receiver in the form of a sequence of pixel-pulses. It is similar to a simple fax system that prints a stream of symbols on a paper tape.

The upper trace of the 2-trace print-out is the amplitude of signal received from the twin-lobe transmitter antenna. The transmitter sends a continuous signal, not a pulse stream. A special electronics box had to convert the amplitude of the radio receiver's audio output into a stream of pulses. The width of each pulse represents the momentary signal amplitude, and is printed by the Hellschreiber as a vertical line segment. Hence, the height of this line segment represents the signal amplitude. See the upper trace in the figure above. The special Hellschreiber beacon-printer and associated electronics are described on this page. As the above figure shows, the initial print quality was far from perfect, but it showed that the right solution had been found!

According to the 1938 Telefunken/Johannesson patent 767936, the flight tests concluded that the radiation pattern of the large lower dipole-array (with its narrow twin-beam) had many vertical lobes, caused by ground reflections. The patent proposes to interlace the upper and lower dipole arrays, such that both are at the same height above ground.

The original 1936 Telefunken patent (767354) mentions the possibility of transmitting the azimuth data via the principles of fax or TV ("Bildfunk oder Fernsehprinzip"). Other early patents are explicitly based on transmission of compass-rose information via video (Nipkow-disk image scanning): e.g., patent 562307 (1929, J. Robinson) and 620828 (1933, Marconi Co.).

During the summer of 1938, the three beacon stations were completely refurbished. The new transmitters had a stable crystal-oscillator instead of a free-running oscillator. The new optical disk (bottom of the next photo, between the two black equipment racks) now had the compass rose symbology captured in Hellschreiber format. All electronic equipment was rack-mounted. The output signals of the two transmitters were transferred to the rotating antenna system via a slip-ring arrangement (top of the next photo).

Fig. 15: New & improved equipment set for the three beacon stations - summer of 1938

(source: Fig. 25 in ref. 181, also p. 95 in ref. 2B)

The equipment set for the aircraft was also completely redesigned - and doubled: two receivers, and the Hellschreiber printer (as well as the associated electronics) had four channels. The printer was built by the Hell company.

Fig. 17: New & improved aircraft equipment - summer of 1938

(source: Fig. 26 in ref. 181)

The new dual equipment allowed printing of the signals from two beacons simultaneously onto a single, extra wide strip of paper. I.e., estimate aircraft position via triangulation without having to switch back and forth between two beacons. This is covered by Lohmann/Telefunken patents 767937 and 767538 (see patent table 1). Assuming simultaneous reception of two beacons, the aircraft's position (and, hence, its ground track) could be sampled and recorded continuously.

Fig. 19: Sample of a print-out ("Registrierungschrieb") from the dual receiver-printer system during UHF tests

(source: Fig. 27 in ref. 181; also used in ref. 2B; also see patent 767537, see patent table 1)

The upper traces of the above plot show that the aircraft is on a bearing of 239° from beacon "R", and on a bearing of 315.5° from beacon "M". Note that, compared to the initial experimental Hellschreiber print-out (Fig. 14 above), the compass rose track now includes the identification letter of the beacon: "R" = Rechlin, "M" = Mietgendorf, "W" = Wasserkuppe. Lighthouses for nautical navigation are identified by the blinking pattern of their light beam. Here, a letter is transmitted every 10 degrees of the compass rose.

Telefunken/Lohmann patent 767514 (see patent table 1 below) proposes another solution for triangulation: a single receiver and single printer, but somehow-synchronized rotation of the beacons, all transmitting on the same frequency. Each beacon would a specific fixed angular offset, such that - within any particular region - the signals from only one beacon would be received at a time.

In Hellschreiber-format, any graphical information that is to be transmitted, is decomposed into a number of consecutive pixel columns. A 360-degree compass rose comprises a band of tick marks and numbers. This band can be converted to Hell-format by decomposing it into columns of pixels as shown in Figure 20B below. Consecutive columns are transmitted pixel-by-pixel, top-to-bottom. For details, see this page.

Fig. 20A: Remote compass, as used in Fw190 etc. (made by A. Patin & Co. G.m.b.H. of Berlin)

Fig. 20B: Compass rose of the Telefunken system (sources: patent 767524 (top), ref. 15 (bottom))

Note that the compass scale shows a one- or two-digit value for every ten degrees of azimuth. That is 1 - 36 for each multiple of 10 degrees (10° - 360°). This is also the standard format for compass roses in general, and for identifying the (magnetic) heading of runways at aerodromes (so there is no runway nr. 0, or a runway with a number larger than 36 - other than in stupid movies). The scale has a short tick mark for each degree, a medium size tick mark for each five degrees, an along tick mark for the each 10 degrees. The azimuth (bearing from the beacon) was referenced to True North ( = QTE), see §10 in ref. 14 and ref. 15. These days, aeronautical radio-navigation beacons are referenced to Magnetic North ( = QDM; exception: Canada's Northern Domestic Airspace, a polar region).

Fig. 21: Print-out of an HS120 "Bernhardine" printer - the paper strip is 4 cm wide

(source: ref. 290B; generated with a PS 120 "Kurzzeichen Prüfsender" "Bernhard" beacon simulator / test signal generator)

A station-identifier letter is also printed every 10 degrees (e.g., "R" or "M" in Figures 19, 20B, and 21 above). The Hellschreiber printing system dates back to 1929 and was the world's first application of a bit-map font. The printer itself is totally oblivious to the content of the bit-pattern. It simply prints each pixel that it receives. This made it possible to temporarily transmit short text messages of 10 characters, instead of the compass scale. For details, see this page. This was the world's first system for uplinking freely formattable textual commands to aircraft ! The messages followed the same format as fighter-control "Reportage" messages, that were normally broadcast via Morse code telegraphy and radio telephony (which was increasingly subject to jamming). Using the beacon to transmit the text messages also freed up capacity on radio-telephony frequencies. Implementation of this data link system required a modification to the signal generator of the "Bernhard" beacon. By the end of the war, this was only implemented at three stations.

Fig. 22: Re-created print-outs with compass scale track (station ident "M") and with "Reportage" track

(I have used FontStruct™ to capture the signal-level track and compass-rose segment as Feld-Hell characters of a "TrueType" font that can be used in regular Windows® and MacOS® programs (e.g., Word®, PowerPoint®). Click here for the two-character font (capital letters A and B) for the signal level. Click here for the 18-character font (capital A-R) for the 360º compass/datalink track)

Late 1938, all prototyping and concept validation-testing was completed. This allowed the RLM during the spring of 1939 to decide to implement the system. However, the activities (incl. construction of beacons) were interrupted for two reasons: the outbreak of the war during the fall of 1939, and the conclusion that the scope of the program (i.e., final development of beacons and aircraft equipment) was too big for the expected scale and duration of this war. Only the pre-production development was to be completed, just in case the need would arise. E.g., the successful dual receiver/printer equipment of 1938 lacked two features: automatic gain control of the received beacon signals, and automatic start-stop of the printer. The latter was needed, as the printer could only include a limited supply of paper tape, a beacon was only received during several seconds of each 30 sec revolution its antenna, and the printed signals should remain visible long enough so as not to require immediate interpretation by the navigator/operator. The required design enhancements were completed during the spring of 1940:

Fig. 23: The automatic receiver/printer system - early 1940

(source: Fig. 29 in ref. 181; also p. 97 in ref. 2B and Fig. 29 in ref. 185J)

To make the automatic receiver/printer work properly, the beacon also had to be adapted. In particular regarding minimizing the side-lobes of the antenna's radiation pattern. Significant effort was expended to arrive at the final solution: a parabolic antenna with an aperture of 6 λ (where wavelength λ = 1 m as f = 300 MHz), a focal length of 5/4 λ, and two dipole feed-antennas (one for the compass rose signal, one for the pointer signal). However, this antenna configuration caused undesirable coupling between the transmitted signals. To suppress this without compromising the complicated radiation patterns, the transmitters were mounted on the back of the rotating antenna (see the right hand photo in Fig. 24 below). I.e., not in the stationary base of the antenna, with connection to the antenna via a slip-ring assembly. Two beacons were constructed. One was again built at the Telefunken test site near Mietgendorf. The other at the Kriegsmarine naval station of Schillig, just northwest of Wilhelmshafen (a major Reichskriegshafen naval base). By the summer of 1940, the evaluation tests were so successful, that the pre-production development of the complete UHF rotary beacon system was concluded.

Fig. 24: the new beacon at Mietgendorf (left) and at Schillig (note box with transmitters on the back of the antenna)

(source: Fig. 30 & 31 in ref. 181)

TELEFUNKEN TRANSITION FROM UHF TO VHF ROTATING BEAM SYSTEM

Thus far, the achievable performance of the Telefunken system had been established at UHF operating frequencies. However, for long-distance navigation, a system with a much larger range (500 to several 1000 km) would be needed. The concept of the Telefunken system is independent of the operating frequency. During the second half of 1940, a rotary beacon was built to investigate the performance on shortwave frequencies. I.e., on HF instead of UHF. As already mentioned, UHF radio waves basically propagate along the (straight) line-of -sight. On HF, however, radio waves to some extent follow the curvature of the earth ("groundwave"), and are also refracted by the ionosphere. The ionosphere is a part of the upper atmosphere. It has layers of atoms and molecules that are ionized by solar and cosmic radiation, as well as by high-energy charged particles from space. HF radio waves may actually make multiple "hops" between the earth's surface and the ionosphere, and propagate much farther than the groundwave. This depends on the altitude, thickness, and density of the ionized layers, as well as the angle at which the radio waves ("skywave") enter the ionized layer(s). The characteristics of the ionosphere are subject to daily and seasonal cycles, as well as the 11-year sunspot-cycle.

In order to assess the feasibility and accuracy of an HF rotating beacon system, Telefunken built a test beacon in a field just outside Großbeuthen. This is a village about 3.5 km (≈2.2 mi) east of the Telefunken site near Mietgendorf, where one of the UHF beacons had already been tested.

Fig. 25: Location of the "Haubenlerche" beacon with respect to the "Bernhard" station Be-0

Two receiving stations in occupied France were used - one at Dieppe (at 900 km from the beacon), and one at Morlaix (1300 km from the beacon):

Fig. 26: HF beacon at Großbeuthen, monitoring receivers at Dieppe & Morlaix

(source: adapted from Fig. 33 in ref. 181)

The above map shows that two receiving stations are on the same bearing (azimuth) from the beacon. They received the beacon signal simultaneously, but not via the same ionospheric radio wave propagation paths and conditions. Comparing the reception results allowed assessment of radio propagation effects, in particular on the pointer beam (which, for the system accuracy, is more critical than the printed compass scale).

The new beacon was given the code name "Haubenlerche" (lit. “crested lark”, a bird species). Its rotary antenna system comprised two elevated parallel vertical dipoles, arranged in a so-called "H-Adcock" configuration. Three operating frequencies were used: around 11 MHz (wavelength λ ≈ 27 m), 7.5 MHz (λ ≈ 40 m), and 5.5 MHz (λ ≈ 54 m). As these frequencies are much lower than the 300 MHz (λ = 1 m) of the tested UHF beacons frequencies, the dipoles are correspondingly longer. However, they are short compared to the wavelength of the transmitted signals. We can estimate several dimensions of the antenna system, based on photogrammatic analysis of the photo below, and the height of the lowest and widest building part in the photo being about 3 m (see text around Fig. 31-32 below). The dipoles measured 10-11 m tip-to-tip. They are spaced by about 12 m, and the feed-point of the dipoles is about 10-11 m above ground level (i.e., only ≈ 0.2 - 0.4 λ).

Fig. 27: The "Haubenlerche" beacon near Großbeuthen

(source: Fig. 35 in ref. 181)

The transmitter was located in the small octagonal room directly below the antenna mast. This room rotated with the antenna. This arrangement avoided errors that would otherwise be introduced by using a slip-ring between a stationary transmitter and the rotating antenna. The motor drive for rotating the "antenna + transmitter room" was located in the slightly larger octagonal room below it. The entire structure sits on top of a round brick building with four corner pillars.

The beacon had one transmitter, with an output power of 500 watt. Only the constant pointer-signal was transmitted, as it is most critical for the system accuracy of the beacon system.

Fig. 28: Horizontal radiation pattern of a single vertical dipole vs. 2 vertical dipoles, spaced 1/2 λ and fed in-phase

Extensive tests were run during a 4-week period in the winter of 1940. In all, bearing values were measured well over 23 thousand times! Only in about 1% of the cases were the bearing values recorded by the two receiving stations identical (both the sign of the error with respect to the actual bearing, and the width of the V-shaped pointer as printed by the Hellschreiber recorders). About 60% of the data was unusable, as the received signal strength was insufficient - not too surprising, given the transmitter's output power. Of the 40% usable data points, all had an accuracy better than ±4°, 97% better than ±3°, 83% better than 2°, and 58% better than 1°. Note: at range of 1300 km (i.e., the distance between the transmitter at Mietgendorf and the receiver at Morlaix), 1° is equivalent to ≈23 km (≈14 miles).

Fig. 29: The V-shaped pointer as printed by the Hellschreiber recorder under various radio-propagation conditions

(source: Fig. 34 in ref. 181)

The round brick building of the "Haubenlerche" beacon is still standing to date (2017; compare to Fig. 26 above from 1940, ref. 259):

Fig. 30: The "Haubenlerche" brick building, just south of Großbeuthen - over 75 years later...

(source: ©2017 B. Saalfeld; used with permission)

Fig. 31: The "Haubenlerche" brick building, just south of Großbeuthen

(source: ©2016 B. Saalfeld; used with permission)

Its roof has a diameter of about 6 m (≈20 ft). The inside diameter of the building is 4 m (≈13 ft), with a wall thickness of 40 cm (≈16"). The floor-to-ceiling height is 2.7 m (≈9 ft). It has four support columns (that appear to be brick, rather than steel I-beams), three windows, and a brick wall. The roof is reinforced with four sections of steel beam that join at the center of the roof. There is no hole at the center of the roof, to the equipment room and antenna installation on top of it. The door opening is 1.9 m tall and very wide. The floor inside the building is at the same level as the ground outside. According to an eyewitness account, there still was an "installation" on the roof, shortly after the war (WW2).

Fig. 32: The inside of the brick building

(source: ©2016 B. Saalfeld; used with permission)

Fig. 33: The door opening of the brick building

(source: ©2016 B. Saalfeld; used with permission)

On top of the roof, there is an octagon (about 2.6 m across) that is made of crudely cemented bricks. One side of the octagon is open. At each corner, there is a heavy mounting plate with bolts sticking up, for an 8-legged superstructure. Two steel plates protrude from the center of the roof.

Fig. 34: Octagonal structure on top of the roof - satellite image on the right

(source: ©2016 B. Saalfeld; used with permission)

There are two pairs of metal conduits that enter the building near ground level. One has the remains of a multi-strand cable with aluminium wires.

Fig. 35: 2x2 cable entries, including a multi-strand aluminium cable

(source: ©2016-2017 B. Saalfeld; used with permission)

A slightly smaller and heavily reinforced version of this round brick building was used as the equipment room and central support of the "Bernhard" VHF beacon ground station (see next section). Note that the specified gauge (diameter) of all wiring of the "Bernhard" beacon was explicitly based on aluminium wiring (ref. 189).

DEVELOPMENT OF THE VHF TELEFUNKEN "BERNHARD/BERNHARDINE" SYSTEM

Late 1940, British interference with the Knickebein beam system became increasingly successful. This led to the demand from the German military for rapid replacement of the Knickebein system. The new system had to be more universal ( = general navigation), more robust to interference, and with "maximum" range (p. 70, 71 in ref. 181). The solution was the Telefunken Rotating Beam system. First of all, such a continuously rotating beam could be used for aircraft navigation tasks other than identification of a bombing target with stationary-but-adjustable beams (Knickebein, X-System). Secondly, the electronics between the radio receiver and the Hellschreiber printer had narrow audio-tone filters. They provided selectivity that made it harder to block reception. Jamming transmitters of much higher power were needed to make the system unusable, and could also not spoof the system (i.e., cause it to generate false bearing indications).

Fast implementation of the new beacon system required the use of:

• Aircraft radios that were mature and already in service in large numbers. I.e., no development of UHF aircraft radios and installation of additional antennas. Instead, use the same 30-33.1 MHz (λ ≈ 10 m) beacon receivers that were used with the Knickebein beam - without any modifications.
• Note that at this time, there were no UHF aircraft receivers that were available "off the shelf" or even "production ready".
• This meant changing the operating frequency of the Telefunken rotating beacon system from UHF ("1 m", ca. 300 MHz) to low-VHF ("10 m", ca. 30 MHz). Hence, increasing the size of the antenna system by a similar factor (10), and not using a dish antenna but arrays of vertical dipoles. Note that this does not change the actual concept of the Telefunken system.
• Using existing radios was so eminently important, that the implications for the ground station were gladly accepted - as it had been for the Knickebein beacon system. Also, development of the Knickebein had been a good exercise in mechanical engineering for the construction a large continuously-rotating antenna system.
• As had been demonstrated with Knickebein, the range of a "10 m" (i.e., ca. 30 MHz) system could be significantly larger than that of the UHF beacons.
• Transmitters that were available off-the-shelf in sufficient numbers. This was no problem, as 30-33.1 MHz beacon transmitters were readily available. Also, for this frequency range, multi-kW AM transmitters were state-of-the-art. For 300 MHz, however, there were no reliable transmitters with more than 200 watt output power.

Note that at the time, Telefunken considered this "10 m" solution only as an absolute "Kriegsnotlösung" (war time emergency measure; p. 18 in ref. 183): a significant compromise, undoubtedly correct for furthering the war cause, but not for a post-war solution. Obviously, the latter consideration was irrelevant under the given circumstances.

So, after about one year of interruption, the development of the Telefunken rotating beam system was resumed. The beacon station itself was given the code name "Bernhard" and the military designator FuSAn 724. Here, "FuSAn" stands for "Funksendeanlage": a radio transmitter installation, including the antenna system. The Hellschreiber printer system for the aircraft was named "Bernhardine", with the designator FuG 120. "FuG" stands for "Funkgerät", i.e., radio equipment. This is typically a transmitter and/or receiver, with antenna and installation rack. However, here it is used in the sense of an add-on to a radio set. The numbers 724 and 120 are entries in a multi-category running numbering system. The range FuSAn 700-799 was reserved for "Bodengeräte, Navigationssendeanlagen" (ground equipment, navigation transmitter stations) and FuG 100-150 for "Navigations- und Kommandoübertragungsgeräte" (navigation & command-uplink equipment), ref. 2D.

Table-2: FuG120 and FuSAn724/725 within the Luftwaffe equipment numbering system

(source: ref. 2D)

Note that by the time that the first VHF Bernhard/Bernhardine system became operational, the focus on the western front (Britain) had already shifted to (night-) fighter control (i.e., defensive), rather than for guiding bombing missions over enemy territory (i.e., offensive). The latter had moved to the eastern front (Russia).

The following diagram summarizes the time-line of the end-to-end development and operation of the various implementations of the UHF/VHF Telefunken rotating beam system. It spanned a full decade:

Fig. 36: Time-line of the development and deployment of the Telefunken UHF/VHF rotating beam system

(based on ref. 2B, 181, 183)

The "Bernhard" ground station, the "Bernhardine" printer, and the 16 "Bernhard" locations are discussed in great detail on the "FuSAn 724/725 "Bernhard" ground station", the "FuG120 "Bernhardine" airborne Hellschreiber printer system" page, and the "Bernhard" station locations page, respectively.

CHARACTERISTICS OF THE FuSAn724/FuG120 "BERNHARD/BERNHARDINE" SYSTEM

Basic characteristics of the Bernhard/Bernhardine system are:

• Frequency: 30 - 33.1 MHz.
• Transmitter power: 2 × 500 watt (FuSAn 724) or 2 x 5 kW (FuSAn 725)
• Antenna system dimensions: ≈28 x 35 m (HxW, 92x115 ft).
• Rail track diameter: 22.6 m (74 ft).
• Weight of the rotating construction: 120 metric tons (265000 lbs), ref. 2C4. Only ref. 183 (p. 19) states 120 metric tons as the weight of the "Gerüst", i.e., of the super-structure without the locomotives. Some literature states the weight as 102 tons (ca. 256000 lbs), which may be a typographical error, or 100 tons (ref. 20) - without being specific about what is included in the weight.
• Antenna rotational speed: 12 degrees per second (2 revolutions per minute). This means that the small locomotives that turned this enormous antenna installation, moved at a respectable speed of 8.3 km per hour (5.2 mph). Justification for selecting this particular speed is given here. The speed was kept constant to within about ±0.2 % ! Note that by design, the printer in the aircraft can not work with a beacon that turns at a different speed.
• Accuracy: initially ±1°, then improved to ±0.5°, finally reduced to ±4° by using a single-trace ( = simpler) printer system and a single transmitter (though unclear if this was ever operational - see the "Bernhardine" FuG 120k section).
• Operational range as a function of aircraft altitude:

Fig. 37: Operational range of the Bernhard/Bernhardine system vs. aircraft height (above ground level at the beacon)

(source: based on data in ref. 15)

The above graph is based on a table in the official "Bernhardine" manual (p. 22 in ref. 15). The beacon is assumed to be at zero altitude. The claimed range was obtained with 500 W transmitters of FuSAn 724. This range makes "Bernhard/Bernhardine" a medium-range system, like other Luftwaffe radio-navigation systems such as "Erika", "Erich", "Hermine", and "Mond" (ref. 230B).

Fig. 38: "Bernhard" beacon nr. 10 (Be-10) at Hundborg/Denmark

(source: www.gyges.dk, used with permission; US gov't = no ©)

For design, construction, and functional details of the "Bernhard" ground station, see the FuSAn 724/25 "Bernhard" page.

The FuG120 "Bernhardine" system comprised the Hellschreiber model HS120, a tone-filter unit (SG120, item nr. 3 in the photo below), a printer-amplifier unit (SV120, item nr. 4), and a DC-DC power converter unit (U120, item nr. 5). For details, see the FuG120 "Bernhardine" page. FuG120 used the existing "EBl3" landing-beacon radio receiver in the aircraft (item nr. 1). When the FuG120 was in use, the SV120 amplifier unit controlled the RF gain of the EBl3 (hence the cable between the two sub-systems in the photo below).

Fig. 40: Instrument racks with the EBL3/EBl2 radios (left) and the FuG120 "Bernhardine" (right)

(source: Fig. 6 in ref. 183, also Fig. 39 in ref. 183)

THE "BERNHARD 30" / "BERNHAUBE" BEACON SYSTEM

Starting in 1942, the Luftwaffe created long range reconnaissance (recce) groups ("Fernaufklärungsgruppen"). They used medium bombers, such as the Dornier Do-17 and Do-215, Focke-Wulf Fw-200, Heinkel He-70 and He-116, and Junkers Ju-86, Ju-88, Ju-188, Ju-290, and Ju-288.

The standard Bernhard/Bernhardine system was considered to support radio navigation of the recce flights over enemy territory. However, its range (see Fig. 37 above) was considered too small. This led to the development in 1943/44 by Telefunken (Lohman) of a derivative of the Bernhard beacon station, with a lower operating frequency than the standard Bernhard. It was supposed to become operational by the end of 1944, but the project was terminated mid-1944. This new beacon station type was referred to as "Bernhard 30", based on its operating wavelength being around 30 m. I.e., a shortwave frequency around 10 MHz, instead of the low-VHF frequency of 30-33.3 MHz of the standard Bernhard. It was also known as "Bernhaube" and had the military reference Funksendeanlage FuSAn 713. There would have been no need to change the "Bernhardine" printer in the aircraft. However, a radio receiver other than the standard 30-33.5 MHz EBl 3 landing beam receiver would have been required. The 6-12 MHz version of the standard Empfänger Kurzwelle "E 10 K2" of the FuG10 aircraft radio transmitter/receiver system would have been used, without any modification.

Fig. 41: Front of an E 10 K receiver

If it had an dipole-array antenna system similar to that of the standard Bernhard beacon, it must have been a lot larger than the latter: reducing the operating frequency by a factor of 3 (from 30 to 10 MHz) implies an increase in dipole length and dipole spacing by the same factor! I.e., an enormous antenna system. Rotating such an antenna system 360° every 30 sec would have been impractial! However, for supporting long range recce flights, there would have been no need to rotate the 360° system. There are suggestions that electronic beam steering was used, instead of a mechanically rotating the antenna system. This technique is based on varying the phase shift between transmitter power feed to the left-hand and the right-hand half of the antenna system. This would have allowed to sweep the beam back and forth about a specific direction. Note that this phase shift technique was already implemented in the standard Bernhard, but only for calibration-adjustment of the antenna system, not for continuous variation. See Fig. 55 in the "Antenna system" section of the Bernhard groundstation page.

Ref. 2A (p. 90, p. 224), ref. 2D (p. 13).

I am not aware of any drawings, photos, or other documentation (incl. location of the test site(s)) of the "Bernhard-30"/"Bernhaube" beacon that have survived. If you have any information, please contact me.

PATENTS

Below is a listing of patents directly related to Bernhard/Bernhardine. Patent source: DEPATISnet. Patent office abbreviations: KP = Kaiserliches Patentamt (German Imperial Patent Office), RP = Reichspatentamt (Patent Office of the German Reich), DP = deutsches Patentamt (German Federal Patent Office), US = United States Patent Office, GB = The (British) Patent Office, F = Office National de la Propriété Industrielle (French patent office), NL = Nederlandsch Bureau voor den Industrieelen Eigendom (patent office of The Netherlands).

Table 1: "Bernhard/Bernhardine"-specific patents

Here are some ancillary patents:

Table 2: Patents regarding transmitting compass rose depiction via video

UNKNOWN / UNCONFIRMED / UNCLEAR ASPECTS

• Did the simplified system with only ±4° accuracy (single-trace printer system, single transmitter, single antenna array) ever enter into service?
• Details of the "Bernhard 30" / "Bernhaube" beacon.

REFERENCES

• Ref. 1: "Bernhard and Bernhardine", p. 24 in "Some historical and technical aspects of radio navigation, in Germany, over the period 1907 to 1945", Arthur O. Bauer, 28 pp. Source: www.cdvandt.org.
• Ref. 2: pages from the reknowned books and other documents by Fritz Trenkle
• Ref. 2A: "Die deutschen Funkführungsverfahren bis 1945" ["The German radio guidance procedures through 1945"], Fritz Trenkle, Dr. Alfred Hüthig Verlag, 1987, ISBN 3778516477, 215 pp.
• Ref. 2A1: p. 149 (X-Uhr / X-system clock).
• Ref. 2A2: pp. 76-110, 224.
• Ref. 2B: "Die deutschen Funk-Navigations- und Funk-Führungsverfahren bis 1945" ["The German radio navigation & guidance systems through 1945"], Fritz Trenkle, Motorbuch Verlag, 1995, 208 pp., ISBN-10: 3879436150.
• pp. 62, 94-102.
• Ref. 2C: "Bordfunkgeräte - vom Funkensender zum Bordradar" ["On board radio equipment - from spark transmitter to radar"], Fritz Trenkle, Bernard und Graefe Verlag (publ.), 1986, 283 pp., ISBN 3-7637-5289-7. [table of contents]
• Ref. 2C1: p. 61-63 - "Kommandoübertragungszusätze" ["Command uplink accessories"].
• Ref. 2C2: p. 83-95 - "Eigenpeil- und Zielflug-Verfahren - LW-MW-Peil und Zielfluggeräte" ["RDF and reverse-RDF systems - LW/MW RDF & approach equipment"]
• Ref. 2C3: pp. 97-118 - "Leitstrahl-Verfahren" ["Guidance-beam systems"].
• Ref. 2C4: p. 108 - photo "Große Knickebein Anlage bei Kleve", ["Large Knickebein installation near Cleves"; note: incorrectly identified by Trenkle as station K4 at Kleve, instead of K2 at Bredstedt].
• Ref. 2C5: pp. 119-133 - "Drehfunkfeuer-Verfahren - LW, KW, UKW, DMW, bis 1945" ["Rotating-beam beacon systems, Longwave"].
• Ref. 2C6: pp. 134-140 - "Hyperbel-Navigations-Verfahren" ["Hyperbolic navigation systems"]
• Ref. 2C7: pp. 141-150 - "Entfernungsmeß-Verfahren" ["Distance measuring systems"]
• Ref. 2C8: pp. 198-200 - "Kenngeräte (Bord-Transponder)" [FuG 25 "Zwilling", FuG25a "Erstling"]
• Ref. 2D: "Versuch einer Zusammenstellung deutscher Funkgeräte 1939 ... 1945 LUFTWAFFE / HEER / MARINE (ca .1200 Geräte)" ["Attempt at a compilation of German radio equipment 1939 ... 1945 Air Force / Army / Navy (ca. 1200 equipment items)"], Wolfgang "Fritz" Trenkle, Issue VI.60 (1960), 100 pp. [file size: 38 MB]. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, Signatur/file nr. RL 2-V/211, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 5: "Instruments of Darkness: The History of Electronic Warfare, 1939-1945", new ed., Alfred Price, Greenhill Books, 2005, 272 pp., ISBN-10: 1853676160; original edition: William Kimber and Co., Ltd, 1967. See note 1
• Ref. 5A: pp. 236-237; Same as pp. 274-275 in the excellent German translation: "Herrschaft über die Nacht: Spionen jagen Radar", Alfred Price, publ.: Bertelsmann Sachbuchverlag Reinhard Mohn, 1968, 304 pp., ASIN B0000BT35X.
• Ref. 5B: p. 82 - second of sixteen photo pages.
• Ref. 6: Transcribed reports from the British Air Ministry, Assistant Director of Intelligence (Prisoner Interrogation),  A.D.I. (K) (a.k.a. "Felkin Reports", after their author). Source: The National Archives of the UK, ref. AIR40/2875 and 2876. Retrieved from www.cdvandt.org.
• Ref. 6A: §19-23 in "Some further notes on G.A.F. Pathfinder procedure" ["EGON" procedure, new EGON procedure, Berhardiner Gerät, Erika Gerät, Y-gerät, "X" Clock, Knickebein jamming],  S.D. Felkin, A.D.I.(K) Report No. 187/1944, 25 April 1944, 5 pp.
• Ref. 6B: §57-59 in "G.A.F. night fighters - R.A.F. Bomber Command countermeasures and their influence on German night fighter tactics" [transcript], S.D. Felkin, A.D.I.(K) Report No. 599/1944, 2 November 1944, 16 pp.
• Ref. 6C: G.A.F. Night Fighters - Recent Developments in German Night Fighting",  S.D. Felkin, A.D.I. (K) Report No. 125/1945, January 1945, 18 pp.
• Ref. 6D: "The GAF (German Air Force) Signals Organisation in the War" [incl. X-System, X-beam, Knickebein, Y-System (Benito), Zyklop/Cyclop, Erika, Sonne beacons in Spain, radar, FuG25/25A, IFF, Panorama, Centimetre Wave R&D, Egon, Gee, H2S, Berlin-Gerät, Kammhuber night fighting, Window, Wilde Sau, HS293], Samuel Denys Felkin, A.D.I.(K) Report No. 334/1945, 1 July 1945, 27 pp.
• Ref. 6E: "Equipment of a Y-Site" [Berta I, Berta II, S16B, Sadir 80/100, Heinrich I (Peiler, D/F), Heinrich III, FuG 16ZE, FuG16ZY], S.D. Felkin, A.D.I.(K) Report No. 527B/1944, 25 Sept 1944, 13 pp.
• Ref. 6F: "Radio and Radar Equipment in the Luftwaffe- I. Blind Landing and Airborne Communications Equipment" [report of interrogations of General Martini and other PoW's; topics: LFF, JLFF, Fu Bl 2, AWG 1, FuG 10 P, FuGe 16, FuGe 17, FuGe 18, FuGe 15, FuGe 24, FuGe 29], S.D. Felkin, A.D.I.(K) Report No. 343/1945, 1 July 1945, 6 pp.
• Ref. 6G: "Radio and radar equipment in the Luftwaffe - II: Navigational aids" [D/F loop equipment, PeGe 6, FuG 141, FuG 142, FuG145; homing beacons: Schwanboje, Biene; beam systems: Zyklop, Sonne, Mond, Stern, Dora, Komet, Erika, Bernhardine, Hermine; Pulse systems: Ingolstadt, Truhe, Baldur, Baldur-Truhe, Baldur-Bernhardine; Ground control systems: Benito = "Y", Egon, Nachtlicht, Nachtfee, Barbara, Barbarossa, Rübezahl], S.D. Felkin, A.D.I. (K) Report No. 357/1945, 25 April 1944, 18 pp.
• Ref. 6H: "Radio and radar equipment in the Luftwaffe - III: Electric altimeters" [FuG 101A, FuG 102, FuG 103, FuG 104], S.D. Felkin, A.D.I. (K) Report No. 362/1945, 27 July 1945, 3 pp.
• Ref. 6J: "Fighter defence of Germany - Control of fighters by the "Y" Procedure", Samuel Denys Felkin, A.D.I.(K) Report No. 525/1944, 14 pp.
• Ref. 6K: "German knowledge of 'OBOE'", [transcript], S.D. Felkin, A.D.I. (K) Report No. 318/1944, 29 Juni 1944, 11 pp.
• Ref. 6L: "Further Report on the Crew of the Ju.88 8-3 Z6 + FH of 1/K.G.66) shot down by A.A. 5 miles N.W. of Alost, on 23rd January 1945.(Previous A.D.I.(K) Report No.142/1945)" [incl. special navigation aids: EGON, "Y" procedure, "Y" clock, new "X" procedure = "Y" + EGON, FuG 28, Y-Clock (CRT), FuG 17, FuG 25A, FuG 217, Ju-88], S.D. Felkin, A.D.I. (K) Report No. 175/1945, 19 February 1945.
• Ref. 6M: "A G.A.F. Pathfinder Unit - Further report on Ju.88 S-1, Z6+IN, of 5/K.G.66, brought down in the sea off Brighton on 25th March 1944", Samuel Denys Felkin, A.D.I.(K) Report No. 160/1944 (prev. No. 141/1944).
• Ref. 7: "Beiträge der Firma Siemens zur Flugsicherungstechnik und Luftfahrt-Elektronik in den Jahren 1930 bis 1945 (Teil 1 & 2)", H.J. Zetzmann, in "Frequenz - Zeitschrift für Schwingungs- und Schwachstromtechnik"
• Ref. 7A: Part 1: Vol. 9, Nr. 10, October 1955, pp. 351-360. [Wassermann radar FuMG 402, Wellenschieber, Jagdschloß / FuMH 404, PPI, Freya FuMG 41, Würzburg Riese]
• Ref. 7B: Part 2 (pp. 387, 388, 392): Vol. 9, Nr. 11, November 1955, pp. 386-395. [RDF antennas for aircraft, Bernhard/Berhardine, transponder DME, D 2002, Kurskoppler, autopilot, FuG 135 Boden-Bord Kommando-Übertragungsgerät]
• Ref. 8: "General Electric funds Hitler", Chapter 3 in "Wall Street and the Rise of Hitler", Antony C. Hutton, G S G & Associates Publ., June 1976 (reprint), 162 pp., ISBN 0945001533.
• Ref. 13: p. 405 and 4.09 in "Japanese Electronics", OPNAV-16-VP101, Photographic Intelligence - Report 1", U.S. Naval Photographic Intelligence Center, January 1945, 166 pp. [33 MB]
• Ref. 14: summary item 27 in "The German Wartime Electricity Supply - Conditions, Developments, Trends", British Intelligence Objectives Sub-comittee (BIOS), Final Report 342, Item No. 33, 28 selected pages. Source: www.cdvandt.org.
• Ref. 15: "Beschreibung und Betriebsvorschrift für Funk-Navigationsanlage FuG 120" ["Description and Operating Instructions for Radio-Navigation System FuG 120" = "Bernhardine"], Telefunken Gesell. für drahtlose Telegraphie m.b.H., document FN-T-GB Nr. 1932, December 1944, 43 pp. [File size: 66 MB - a good-but-lower resoluton file is here 26 MB]
• Ref. 15A: higher quality version of pp. 16-20 (equipment photos); source: corporate archives of DTM Berlin, file nr. I.2.060C-00666.
• Ref. 19: p. 122 in "Die Erprobungstelle Rechlin", Christoph Regel, pp. 60-149 in "Flugerprobungsstellen bis 1945: Johannisthal, Lipezk, Rechlin, Travemünde, Tarnewitz, Peenemünde–West", Heinrich Beauvais, Max Mayer, Bernard & Graefe Verl., 1998, 364 pp., ISBN: 3763761179; Vol. 27 of "Die deutsche Luftfahrt : Buchreihe über die Entwicklungsgeschichte der deutschen Luftfahrttechnik", Theodor Benecke, Deutsches Museum
• Ref. 20: pp. 59-63 of "Richt- und Drehfunkfeuer" ["Directional and rotating radio beacons"; 4-Course, Telefunken Compass, Bernhard, Erika, Komet, ILS/LOC/GS], Chapter 3 of “Leitfaden der Funkortung: Eine systematische Zusammenstellung der Verfahren und Anlagen der Funkortung“ [Guide to radio location: a systematic survey of radio location methods and installations], Vol. 1 of "Lehrbücherei der Funkortung", Walter Stanner, 4^th ed., Deutsche RADAR-Verlagsgesellschaft m.b.H., 1957, 160 pp.
• Ref. 151: p. 16, 17, 22 in "Jagdschloß A (Lehrunterlagen) Teil I", 2^nd ed., Lehrschule für Fernmeldetechnik, Detmold, November 1944, 115 pp. Source: www.cdvandt.org
• Ref. 164: documents of the Combined Intelligence Objectives Sub-Committee (CIOS). Source: cdvandt.org.
• Ref. 164A: "Institutes of the Bevollmaechtigter fuer Hochfrequenz-Forschung", CIOS, Item No. 1 & 7, File No. XXXI-37, May 1945, 215 pp.; source: cdvandt.org.
• Ref. 164B: "The I.T.T., Siemens and Robert Bosch Organizations" [incl. Lorenz: Elektra, Sonne, Mond, Knickebein, Erika, Goldwever, Hermine, 6-mast Lorenz Adcock D/F based on British patent, Lorenz Blind Approach/Landing, IFF, radar], CIOS, Item No. 1, 7 & 9 (Radar, Signal Communications, Physical & Optial Instruments and Devices), File No. XXXI-38. Source: cdvandt.org. Retrieved 22 September 2019.
• Ref. 164C: "Report on C. Lorenz A.G." [history, factories, relationship with Philips & Telefunken, Stuttgart UHF radio link (FuG0s, FuG03a), Feuerzauber & Feuermolch Oboe-jammer, FuG200, FuG226/Neuling], CIOS, Item No. 1, File No. XXV-12, 13 pp. Source: cdvandt.org. Retrieved 7-Feb-2020.
• Ref. 172: copy of item in file AIR 29/284 "Central Interpretation Unit (CIU) Medmenham; Interpretation reports and aerial photos (1943)". Item is in the collection of The National Archives; material with UK Crown Copyright, used in accordance with the Open Government License [pdf].
• Summary of the contents of ref. 172A.
• Ref. 172A: "German “Windjammer” R.D.F. Stations", part of "Monthly interpretation review for July 1943", 7 pp.
• Ref. 173: copy of items in file AIR 14/3577 "Signals investigation on 27 to 35 Mc/s "Windjammer" (1943/1944)". Items are in the collection of The National Archives; material with UK Crown Copyright, used in accordance with the Open Government License [pdf].
• Summary of the contents of ref. 173A-173E.
• Ref. 173A: "'Windjammer" observation", by R.A. Fareday (Noise Investigation Bureau [Electronic Intelligence], N.I.B., London), dated 20^th June 1944, 1 page.
• Ref. 173B: "Possible "Windjammer" transmissions", report by Flight Lieutenant Douglas of 192 Sq., dated 16^th December 1943, 1 page.
• Ref. 173C: "192 Squadron Flight report No. 215/43" by F/Lt Robinson to Squadron Leader Burtler, dated 15^th November 1943 (actual report by P/O G.F. Evans of 13^th November 1943), 6 pages.
• Ref. 173D: "Windjammer – Arcachon", letter from Air Ministry A.I.4. [intelligence branch section supervising RAF Y Service] to Commanding Officer of 192 Squadron, dated 16^th July 1943, 1 page + 1 aerial photo.
• Ref. 173E: "The Windjammer and Dreh-Elektra", by 192 Squadron Leader J. Whitehead, dated 18^th June 1943, 1 page.
• Ref. 174: copy of items in file AIR 14/3594 "Windjammer" station: photographs and interpretation reports. Includes vertical and low oblique aerial photographs of 'Windjammer' radar sites in Germany and France (1943/1944)". Items are in the collection of The National Archives; material with UK Crown Copyright, used in accordance with the Open Government License [pdf].
• Summary of the contents of ref. 174A-174J.
• Ref. 174A: Letter entitled "W/T Bergen/Belvedere" by Squadron Leader C.W. Swanell on behalf of the Group Captain commanding R.A.F. Station Medmenham to R.V. Jones (A.D.I. Science), dated 9^th April 1943, 1 page + 1 photo
• Ref. 174B: Aerial photo of station "Bergen/Belvedere" [The Netherlands], photo No. 3022, taken 22^rd March 1943 by 541 Squadron
• Ref. 174C: Letter entitled "W/T – Bergen/Belvedere" by Group Captain commanding R.A.F. Station Medmenham to R.V. Jones (A.D.I. Science), dated 9^th April 1943, 1 page. (note: photos referenced in letter not on file)
• Ref. 174D: Letter entitled "W/T Desvres/Le Bois Julien" on behalf of Group Captain commanding R.A.F. Station Medmenham to R.V. Jones (A.D.I. Science), dated 15^th November 1942, 1 page + 2 photos.
• Ref. 174E: Letter entitled "W/T: Desvres/Le Bois Julien" on behalf of Group Captain commanding R.A.F. Station Medmenham to R.V. Jones (A.D.I. Science), dated 29^th March 1943, 1 page + 1 photo.
• Ref. 174F: "Interpretation Report No. G. 308" dated 28^th June 1942, of aerial photos taken over Desvres/Le-Bois-Julien at altitude of 20k ft during Sortie A/945 on 20^th June 1942, 1 page + 1 photo.
• Ref. 174G: "Interpretation report No. G.590" dated 6^th October 1942, of aerial photo taken over locality Morlaix, W/T station Mt. St. Michel, at altitude of 12k ft during Sortie Q/21 on 24^th September 1942, 2 pages + 1 photo.
• Ref. 174H: Letter entitled "W/T: Pouzauges/St.Michel-Mont-Mercure" on behalf of Group Captain commanding R.A.F. Station Medmenham to Squadron Leader Whitehead (A.I.4), dated 29^th March 1943, 1 page + 3 photos.
• Ref. 174J: Photos No. 4065 and 4066 of station at St. Vaast / La Pernelle, taken 31^st March 1943 from off shore. [station is fully, though vaguely, visible on horizon]
• Ref. 175: articles about the "Y" service and RAF 192 Squadron
• Ref. 175A: pp. 512-516, 524 in "Activities at Knockholt", J.A. Reeds, Appendix B in "Breaking Teleprinter Ciphers at Bletchley Park - General Report on Tunny with Emphasis on Statistical Methods (1945)", 1^st ed., I.J. Good, D. Michie, G. Timms (J.A. Reeds, W. Diffie, J.V. Fields, eds.), John Wiley & Sons, IEEE Press, 2015, 735 pp.
• Ref. 175B: "Account of 192 Squadron radio countermeasures operations" [part of the 'Y' service; "Bernhardine"], Frances Grundy, 1945, 8 pp. Source: IBCC Digital Archive, accessed June 16, 2021. Content is available under a CC BY-NC 4.0 International license (Creative Commons Attribution-NonCommercial 4.0).
• Ref. 181: "Drehfunkfeuer System Telefunken - Teil 1: Verfahrensbeschreibung EC1-4262" [Telefunken rotating radio beacon, part 1: description of the method], Adalbert Lohmann, Berlin, October 1942, 129 pp., copy nr. 29, personal copy of Albrecht Leyn [note: this document was never printed, other than a very limited number of personal copies, individually approved by Dept. LC-4 (Technisches Amt) of the RLM; ref. 183]; source: corporate archives of DTM Berlin, part of file nr. I.2.060C-06172  [file size: 62 MB]
• Ref. 183: "Das Drehfunkfeuer-Verfahren Bernhard und Bernhardine, System Telefunken" ["Verfahrensbeschreibung Bernhard, Bernhardine", description of the Bernhard-Bernhardine method], Adalbert Lohmann, Telefunken Gesellschaft für drahtlose Telegraphie m.b.H., Berlin-Zehlendorf, Telefunken document EC 1 4310, July 1943, 28 pp., copy nr. 11; source: corporate archives of DTM Berlin, file nr. I.2.060C-04403.
• Ref. 185: radio location & navigation, general articles, articles covering multiple systems
• Ref. 185A: "Survey of Radio Navigational Aids" [DF, Shoran, Oboe, DME, transponders, radar, Loran, GEE, Decca, Raydist, Micro-H, Consol, Sonne, Navaglobe, A-N ranges, CAA Omnirange, ILS landing beam, radio altimeters, rotating beacons, Orfordness range, Navar, Teleran, Navascope], Robert I. Colin, in "Electrical Communication" (Technical Journal of the International Telephone & Telagraph Corporation and Associate Companies), Vol. 24, No. 2, June 1947, pp. 219-261. Source: www.americanradiohistory.com; accessed 27 March 2020. [pdf]
• Ref. 185B: "The Geography of Radionavigation and the Politics of Intangible Artifacts", William Rankin, in "Technology and Culture", Volume 55, Number 3, July 2014, pp. 622-674 [pdf]
• Ref. 185C: "Electronic Navigation Systems", Summary Technical Report of Division 13 of the National Defense Research Committee (NDRC) - Vol. 2B, 1946, 374 pp. [file size 211 MB; a lower-but-good resolution version is here, 49 MB]. Source: www.loc.gov. Retrieved 8 August 2008. [Beacons, Oboe, Decca, A-N, Radio Range, Sonne/Consol, Gee, radar, Loran, Shoran, Micro-H, Four-Course Aural Range, ADF, Elektra, Benito, Knickebein, Ruffian, Hermine, Ruebezahl/Egon, Bernhard/Bernhardine, Hyperbol, Truhe, Zyklop/cyclop, Dora, Erika, Diskus, Schwanboje, Nachtfee, Decca, POPI]
• Ref. 185D: "Air Navigation", U.S. Navy Hydrographic Office H.O. Publication No. 216, corrected print 1963, 717 pp.
• Ref. 185D1: "Lines of Position, Bearings, and Fixes", Chapter IX, pp. 188-202
• Ref. 185D2: "Low Frequency Radio Range", pp. 288-300 in Chapter XI "Radio" (pp. 261-300).
• Ref. 185D3: "Hyperbolic Navigation Systems"[Loran, Decca, Lorac, Sofar, Consol, Sonne, Consolan, GEE], Chapter XIII, pp. 345-365.
• Ref. 185E: "On the origins of RF-based location", Hans G. Schantz, in "Proc. 2011 IEEE Radio & Wireless Symposium", Phoenix/AZ/USA 16-20 Jan., 2011. Source: researchgate.net, retrieved 16 Jan 2020.
• Ref. 185F: "Radiobeacons and radiobeacon navigation", George R. Putnam, U.S. Dept. of Commerce, Lighthouse Service, 1 July 1931, 44 pp. [pdf]
• Ref. 185G: p. 260 in "A survey of continuous-wave short-distance navigation and landing aids for aircraft", Caradoc Williams, in "Journal of the Institution of Electrical Engineers - Part IIIA: Radiocommunication", Volume 94, Issue 11, March-April 1947, pp. 255 - 266.
• Ref. 185H: "History of radio flight navigation systems", translated into English by M. Hollmann, P. Aichner, 15 pp. Source: radarworld.org. [Scheller A/N, Lorenz E/T, Telefunken Knickebein, Hermine, X-System / Wotan I, Four-Course Range, ILS, Elektra, Consol, Erika, Komet, Hohentwiel]
• Ref. 185J: "Navigation und Luftsicherung" ["Navigation and air traffic control"], Leo Brandt, pp. 25-80 in "Arbeitsgemeinschaft für Forschung des Landes Nordrhein-Westfalen", Vol. 13, Springer Fachmedien, 1952, 98 pp. Accessed 3 March 2020. [pdf]
• Ref. 185K: "Die Funknavigation der Luftfahrt" ["Radio navigation for Aviation"], August Leib, pp. 9-68 in "Telefunken Hausmitteilungen", Telefunken, Vol. 20, Nr. 82, December 1939.
• Ref. 185L: "A Brief Description of the Major Second World War Navigational Aids", Brian Kendal, in "Journal of Navigation", Vol. 45, No 1, Januay 1992, pp. 70 - 79. Source: en.booksc.org, accessed April 2021. [pdf, See note 1]
• Ref. 185M: "Radio beacons and Radiobeacon Navigation", George R. Putnam, U.S. Dept. of Commerce, Lighthouse Service (Bureau of Lighthouses), July 1931, 42 pp.
• Ref. 185N: "Flugsicherung durch Richtfunkbaken" ["Air traffc control through directional radio beacons"], H. Rahskopff, in "Zeitschr. des Vereins deutscher Ingenieure (V.D.I.)", Vol. 75, 4 January 1931, pp. 116-117.
• Ref. 185P: "Radio navigation in the 1920s" [abstract], C. Powell, in "Journal of the Institution of Electronic and Radio Engineers (IERE)", Vol. 56, Nr. 8-9, August/September 1986, pp. 293-297. Source: en.booksc.org, accessed April 2021. [pdf, See note 1]
• Ref. 185Q: "La Radionavigation" [in French], J. Piergo, pp. 159-167 in "Science et Vie", No. 349, October 1946.
• Ref. 185R: "The Aeronautical Navigational Radio Service" [Consol, Decca, Loran, GEE, SBA, BABS, MF Range], Chapter VII (pp. 101-109) in "The Civil Aviation Communications Handbook", Vol. 5 of CAP series (M.C.A.P.5), Great Britain Ministry of Civil Aviation, 2^nd ed., 1949, 286 pp. Source: atchistory.files.wp.com. Accessed 19 May 2020. [pdf, file size 26 MB]
• Ref. 185S: "RF Positioning - Fundamentals, Applications, and Tools" [incl. RDF, TFK Kompass, Orefordness, Sonne, Gee, Oboe, Gee-H, Loran], Rafael Saraiva Campos, Lisandro Lovisolo, Artech House (publ.), 29 pp. Accessed: 31 January 2020. [pdf]
• Ref. 185T: "Mail Planes Radio Equipment", in "Radio Topics", March 1924, pp. 15-16. Accessed 14 April 2020. [pdf]
• Ref. 185U: "Highlights of antenna history", Jack Ramsay, in "IEEE Communications Magazine", Vol. 19, Iss. 5, September 1981, pp. 4-16. Accessed 6 May 2020. [pdf]
• Ref. 185V: "Aerodrome and Air Route Control", in "The Marconi Review", No. 65, March-April 1937, pp. 9-19. Source: worldradiohistory.com, retrieved 20 April 2021.
• Ref. 185W: "Navigation by cigars" [orig. published in a Pittsburgh newspaper on 19 May, 1938], on p. 47 in "A Place in the Sky: A History of the Arnold Palmer Regional Airport, 1919-2001", Richard David Wissolik (gen. ed.), Saint Vincent College for Northern Appalachian Studies (publ.), 2001, ISBN-13: 978-1885851178, 225 pp.
• Ref. 185X: publications about aviation/flight navigation in general
• Ref. 185X1: "Flight Navigator Handbook", US Dept. of Transportation, Federal Aviation Administration, publication FAA-H-8083-18, 2011, 281 pp.
• Ref. 185Y: articles  in "The Journal of Navigation"
• Ref. 185Y1: "Air Navigation Systems: Chapter I. Astronomical Navigation in the Air 1919–1969", J.E.D. Williams, in "The Journal of Navigation", Vol. 41 , Issue 3, September 1988, pp. 375-406. Source: en.booksc.org, accessed April 2021. [pdf, See note 1]
• Ref. 185Y2: "Air Navigation Systems: Chapter I. Astronomical Navigation in the Air 1919–1969. Part II - Instruments", J.E.D. Williams, in "The Journal of Navigation", Vol. 42 , Issue 1, January 1989, pp. 73-91. Source: en.booksc.org, accessed April 2021. [pdf, See note 1]
• Ref. 185Y3A: "The beginnings of air radio navigation and communication", Brian Kendal, in "The Journal of Navigation", Vol. 64, Iss. 1, January 2011, pp. 157-167.. Source: en.booksc.org, accessed April 2021. [pdf, See note 1]]
• Ref. 185Y4B: response to ref. 185Y3A - "The beginnings of air radio navigation and communication", Walter Blanchard, in "The Journal of Navigation", Vol. 64, Iss. 3, July 2011, pp. 571-572. Source: en.booksc.org, accessed 27 May 2021. [pdf, See note 1]
• Ref. 185Z: articles by Robert Watson-Watt
• Ref. 185Z1: "Radio Aids to Navigation", Robert Watson-Watt, in "The Journal of Navigation", Vol. 1, Iss. 1, January 1948, pp. 15-21. Source: en.booksc.org, accessed April 2021. [pdf, See note 1]
• Ref. 185Z2: "The evolution of radiolocation" [incl. Oboe, Rebecca-Eureka, Orefordness, G-H, BABS], Robert Watson-Watt, in "Journal of the Institution of Electrical Engineers - Part I: General", Vol. 93, Iss. 69, September 1946, pp. 374-382 Source: en.booksc.org, accessed April 2021. [pdf, See note 1]
• Ref. 189: "Stückliste zum Kabelplan "Bernhard"" [parts list of "Bernhard" wiring diagram], Telefunken document EC1-4237, 6 July 1942, 23 pp.; source: corporate archives of DTM Berlin, part of file nr. I.2.060C-07753.
• Ref. 230: German & British WW2 RDF, radio-navigation systems, and associated jamming systems / countermeasures
• Ref. 230A: p. 46 in "The Secret War", Brian Johnson, Pen and Sword (publ.), 2004, 352 pp.
• Ref. 230B: Table 1 in "Verfahren und Anlagen der Funkortung" ["Radio-navigation methods and installations"], W. Stanner, in "Elektrotechnische Zeitung (ETZ)", Ausgabe A, Vol. 75, Nr. 13, 1 July 1954, pp. 438-442. [circular LoP, hyperbolic LoP, Consol, Consolor, Decca, Loran, range of various systems incl. "Erika", "Erich", "Hermine", and "Mond"]
• Ref. 230C: articles and books about the Battle of the Beams
• Ref. 230C1: "Pulling the crooked-leg", R.V. Jones, in "New Scientist", 23 February 1978, pp. 493-496.
• Ref. 230C2: "Milestones - Battle of the Beams", Carlo Kopp, in "Defence Today", January/February 2007, pp. 76, 77. [pdf]
• Ref. 230C3: "The Battle of the Beams - Part 1-3", D.V. Pritchard (G4GVO), in "Practical Wireless", Vol. 64, No. 1, Issue 970, January 1989, pp. 43-47; No. 2, Issue 971, February 1988, pp. 46-49; No. 3, Issue 972, March 1988, pp. 30-34. Source: worldradiohistory.com, accessed 1 September 2020. Also published as "The Battle of the Beams - Part 1-3", D.V. Pritchard (G4GVO), in "Ham Radio Magazine", June 1989, pp. 29-38; August 1989, pp. 20-29; October 1989, pp. 53-61. Source: worldradiohistory.com, accessed January 2014.
• Ref. 230C4: "Battling the Radio beams", "Part 1: Headache and Aspirin" and "Part 2: Bromide, Domino and Benjamin", Bruce Taylor (HB9ANY), in "RadCom Magazine", Radio Society of Great Britain (RSGB), Vol. 96, No. 5, May 2020, pp. 80-82, and Vol. 96, No. 5, June 2020, pp. 82-84. Source: researchgate.net, retrieved September 2022.
• Ref. 230D: "Most Secret War: Britisch Scientific Intelligence 1939-1945", R.V. Jones, Hamish Hamilton (publ.), 1978, 576 pp. See note 1
• Ref. 230E: to be allocated
• Ref. 230F: to be allocated
• Ref. 230G: "Chapter II and III in "R. V. Jones and the Birth of Scientific Intelligence", James Martinson Goodchild, PhD thesis, University of Exeter, March 2013, 640 pp. [pdf] Accessed 12 May 2019.
• Ref. 230H: "Electronic Warfare and the Night Bomber Offensive", Rob O'Dell, pp. 97 - 117 in "Air Power Review", Royal Air Force, Volume 10, Number 1, Spring 2007.
• Ref. 230J: "Radio Navigation Systems for Aviation and Maritime Use — A Comparative Study" [RDF, Consol/Consolan, Navaglobe, VOR, VORTAC, VOR/DMET, Navarho/Navarho-H/-HH/-Rho, Decca, Standard Loran (Loran-A), Loran-C, Radio Mesh Systen], W. Bauss (tech ed.), Advisory Group for Aeronautical Research and Development (AGARD), North Atlantic Treaty Organization (NATO), AGARDOgraph 63, Pergamon Press, 1963, 232 pp. Translation of the German publication "Funkortungssysteme für Luft- und Seefahrt - Eine vergleichende Gegenüberstellung", Verkehrs- und Wirtschaftsverl. Dr. Borgmann (publ.). [pdf, file size 58 MB]. The following are articles taken from this book.
• Ref. 230J1: "Radio Direction-Finding on Board Aircraft and Ships", W.T. Runge, pp. 19-28.
• Ref. 230J2: "Consol and Consolan", Ernst Kramar, pp. 29-39.
• Ref. 230J3: "VOR-System", K. Bärner, pp. 43-57.
• Ref. 230J4: "Decca". H. Lueg, pp. 81-101.
• Ref. 230J5: "Standard-Loran", Ernst Kramar, pp. 113-118.
• Ref. 230K: "The Navigational Beam System "Elektra-Sonne" [Elektra, Sonne, Elektra-Sonne, Mond; complete German description, short translated summary in English], Otto von Heil, FIAT Final Report No. 1105, Field Information Agency Technical (FIAT), US Office of Military Government for Germany, 17 June 1947, 177 pp. Source: www.cdvandt.org. Accessed: March 2019.
• Ref. 230L: "Funknavigation, Elektra, Sonne, Mond, Stern, Erika", J. Goldmann (Lorenz), Vorträge vor Fernmelde-Ingenieuren der Luftwaffe - Luftnachrichtenschule Halle (Saale) [Luftwaffe Signals School], February 1944, 22 pp. [file size: 25 MB]
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 2-V/48, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230M: "Sonne Planungen" [planning of Sonne sites], Luftnachrichten telegram, dated 29 July 1944, signed by Capt. Franz, 1 p.
• Document mentions Sonne station Liebau, Sonne stations 12 (Warsaw) & 23, Großsonne station 32 (Danzig), and new Sonne site near Oppeln.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 2-V/6, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230N: "Bumerangstörung im Ruhrgebiet" [Jamming of "Bumerang" (German codename for Oboe-guided British Mosquitoes) in the Ruhr area), Nr. 82 514/44 g.Kdos. (3.Abt.III)
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 2-V/6, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230P: original correspondence of the Director General of Luftwaffe Signals Corps (General Nachrichtenführer). Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 2-V/5., used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230P1: "Anruf Gen.Martini wegen Erstellung Boden-Truhe West" [telephone call with General Martini regarding construction of Boden-Truhe West]. Letter/telegram from Gen. Nachrichtenführer (1.Abt.II), addressed to Chef. der Ln.Inspektion. Letter ref. OKL Gen.Nafü. Nr. 10 955/44 g.Kdos. (1. Abt.II). Letter is dated 18 June 1944. Letter states that due to current situation, the forward-looking Boden-Truhe West station will not be constructed and construction of the rearward-looking Boden-Truhe West station will be accelerated, using transmitters of the prior. The planned transmitters will be transported from France, but with trucks/lorries (wood gas) instead of by rail.
• Ref. 230P2: "Fernmündliche Rücksprache Major Kluge - Hptm. Gottschalk am 30.6.44" [telephone conversation Major Kluge - Captain Gottschalk]. Letter from Gen.Nafü (1.Abt.), addressed to Lfl.Kdo. 3 - Höh.Nafü, General der Navigation, and General der Kampfflieger. Letter ref. OKL Gen.Nafü. Nr. 11 092/44 g.Kdos. (1. Abt.II). Letter dated 8 July 1944. Letter states that, due to operational and test reasons, construction of radio navigation stations "Komet 2 (Laharie)", "Komet 3 (Labouheyre), and "Dora 2 (Morlaix) cannot be finished. Due to failure of "Erika 2 (Cherbourg)", the "Erika" system can no longer be used in the West. Therefore, "Erika 1 (Boulogne)" can be dismantled and parts (transmitter etc.) be secured.
• Ref. 230P3: "Sender for Bodentruhe" [transmitters for Truhe ground station]. Letter from Gen.Nafü (1.Abt.), addressed to Gen.Nafü/Ln.Insp (5.Abt/6.Abt). Letter is dated 8 July 1944. Letter describes allocation of 3 "Feuerstein" transmitters instead of "Feuerzange" transmitters to "Bodentruhe West", also mentions 3 "Merkur" transmitters are to be modified for "Bodentruhe West", schedule for delivery of additional "Merkur" and "Feuerstein" transmitters to be provided.
• Ref. 230P4: "Abschalten von Rundfunksendern." [Shutdown of (public) radio broadcast transmitters]. Letter from OKL.Gen.Nachrichtenführer. Letter ref. 11 987/44 geh. (1.Abt.II). Letter is dated 2 July 1944. Letter states that, as agreed with OKW and RPromin [Reichs Propaganda Ministerium], the request for shutting down radio broadcast transmitters during jamming/interference of radio beacons for day & night fighters, is denied. Reasons given by RPromin: 1) the current regulations already imply large scale shutdowns, further reduction is unacceptable for the propaganda, 2) the population interprets shutdowns as sign of imminent air raids. Shutdown for other reasons would cause unrest, and 3) Broadcast transmitter frequencies are fixed. If broadcast transmitters interfere with radio beacons or other services, Lfl.Kdo. must make sure that those services use other frequencies. As in other Luftflotten regions, restriction of radio beacons improves spread of utilized frequencies.
• Ref. 230Q: articles about Knickebein
• Ref. 230Q1: "Location of Knickebein station K1-K13" [map coordinates, satellite images, aerial photos], Frank Dörenberg, 12 August 2020, 8 pp.
• Ref. 230Q2: pp. 245-247 in "Gleichgeschaltet: Maulburg im Nationalsozialismus und die Rolle von Hermann Burte im Dritten Reich", Hansjörg Noe, Verlag Waldemar Lutz (publ.), 448 pp., ISBN 978-3-922107-09-5. [Extract]
• Ref. 230Q3: p. 16 of "Knickebein" thread in the forum of geschichtsspuren.de, post by ChristianCH on 30-Mar-2014. [Extract]
• Ref. 230Q4: p. 2, 3 in "Krigsminner 1940-45 i Klepp kommune" ["War memories 1940-45 in the Klepp municipality"], F. Ravndal, T. Ødemotland, A. Jakobsen, T. Erga, O. Håland, B. Bore, A. Hatteland, J. Sørbø, T. Reve, Laget (publ.), 1990, 8 pp. Source: Norwegian National Library, accessed 31 July 2020. [pdf]
• Ref. 230Q5: "Kontrollpunkten der Knickebein-Anlage 4 (Karten), dabei Gesamtübersicht der Kontrollpunkte, Bereich zwischen Kranenburg und Donsbrüggen" [high-resolution version is here, file size: 42 MB]["Radiation-pattern check points for Knickebein Nr. 4 ( = Kleve-Materborn) in the area between Kranenburg and Donsbrüggen"], 8 maps with check points marked by small red dots and red lines, some measured field strength values are written in green (dated January 1942), Kranenburg = ca. 13 km west of K4; Donsbrüggen = ca. 12 km northwest of K-4; 2 maps with check points in The Netherlands (just north & south of Groesbeek = ca. 18 km west of K-4)]. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/German, Signatur/file nr. RL 19/6/64 - 19/6/84, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230Q6: "Knickebein" [incl. difference between KG 100 and other LW Kampfverbände], Luftwaffenführungsstab Ia (KM), adressed to "I L", 6 October 1940, g.Kdos, 1 page + 1 map. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, Signatur/file nr. RM 7/2372, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230R: articles about X-Verfahren ("X-Procedure), X-Gerät ("X-Equipment"), Y-Verfahren ("Y-Procedure"), Y-Gerät ("Y-Equipment"); the Y-guidance method is not to be confused with Y-Peiler ("Y-D/F system"), nor the British Y-Service; bombing in general.
• Ref. 230R1: pp. 48-49 (X-Gerät, Y-Gerät) in "German Radio Communication Equipment", US War Department Technical Manual, TME 11-227, June 1944, 61 pp.
• Ref. 230R2: "Fliegerhorst Köthen" ["Köthen airfield"], source: Militärhistorisches Museum Anhalt, accessed 11 August 2020. [pdf]
• Ref. 230R3: pp. 14-27 in "The First Pathfinders - The Operational History of Kampfgruppe 100, 1939-1941", Kenneth Wakefield, William Kimber (publ.), 1981, 265 pp.
• Ref. 230R4: "Der Bombenabwurf" ["The bomb drop"], Bachofener, in "Allgemeine schweizerische Militärzeitung = Journal militaire suisse = Gazetta militare svizzera", Vol. 82, Nr. 1, January 1936, pp. 296-304. Source: e-periodica.ch, retrieved 18 June 2021.
• Ref. 230R5: "Deconstruction the myth of the Norden bombsight", Michael Tremblay, University of Victoria/BC/Canada, Master of Arts thesis, 2007, 150 pp. Source: library.uvic.ca, retrieved 30 June 2021.
• Ref. 230R6: "The bombsight", in "US Air Forces At War", special issue of "Flying", Vol. 33, No. 4, October 1943, pp. 103-107, 342-344.
• Ref. 230R7A: "Notes on enemy bombsights", F. Poslethwaite, in "Aircraft Engineering and Aerospace Technology", Vol. 14, Nr. 9, September 1942, pp. 244-247, 250. Source: en.booksc.org, retrieved 30 June 2021. [pdf]
• Ref. 230R7B: "Notes on enemy bombsights (concluded)", F. Poslethwaite, in "Aircraft Engineering and Aerospace Technology", Vol. 14, Nr. 10, October 1942, pp. 276-280. Source: en.booksc.org, retrieved 30 June 2021. [pdf]
• Ref. 230R8: "Close-up of the Norden bombsight", Volta Torrey, in "Popular Science", Vol. 146, No. 6, June 1945, pp. 70-73, 220, 224, 228, 232.
• Ref. 230R9: "Bomb trajectories", Edwin Bidwell Wilson, National Advisory Commission on Aeronautics (NACA), Technical Report No. 79 (NACA-TR-79; reprint from 5^th annual report), 1920, 9 pp. Source: ntrs.nasa.gov, retrieved 28 June 2021.
• Ref. 230R10: "Weapon Delivery Analysis and Ballistic Flight Testing", R.J. Arnold, J.B. Knight, Vol. 10 of "AGARD Flight Test Techniques Series", Advisory Group for Aeronautical Research and Development (AGARD), North Atlantic Treaty Organization (NATO), AGARDOgraph 300, Technical Report RDP, 1 July 1992, 172 pp. Source: www.sto.nato.int, retrieved 21 June 2021.
• Ref. 230R11: pp. lxx-lxxiv in "The Bombing War: Europe, 1939-1945", Richard Overy, Penguin Books Ltd. (publ.), 2014, 852 pp. (published 2013 by Allan Lane, published 2015 as "The Bombers and the Bombed: Allied Air War Over Europe, 1940–1945")
• Ref. 230R12: "Theory of horizontal bombing", pp. 233-234 in Section D of "Aircraft fire control", in Chapter 23 of "Fire Control", Vol. 2. of "Naval Ordnance and Gunnery", Dept. of Ordnance and Gunnery, United States Naval Academy, Bureau of Naval Personnel (ed.), NAVPERS 10798-A, 1958 revision of the 1950 edition, 508 pp. Source: eugeneleeslover.com,, retrieved 21 September 2021.
• Ref. 230R13: "Der gezielte Blind-Bomben-Wurf - Die deutsche Lösungen: Das X-verfahren, Das Y-verfahren (Kampf)" ["The precision blind bomb drop - The German solutions: the X-Procedure, the Y-procedure"], Heinrich Pusch (Oberst a.D.; Gruppenkommandeur Kampfgruppe 100 in 1939, Kommandeur Luftnachrichten-Regiment 31 in 1941 and 56 in 1943], date unknown, 81 pp. [file size: 53 MB]. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) ZA 3/402a, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230S: articles about "Komet" ("Comet")
• Ref. 230S1: "Tysk Retningsantenneanlæge i Kølby Vest for Nibe" ["German Directional Antenna Installation in Kølby, west of Nibe"; rotating-beam system "Komet" ????], Commission for the Inspection of German Radio Stations Constructed in Denmark, report by Capt. Bahnsen and Prof. Jørgen Rybner of site visit on 12 Dec 1945, 3 pp. Courtesy M. Svejgaard, used with permission. English translation by me is here.
• Ref. 230T: "Scientific Intelligence", R.V. Jones, 12 February 1947 lecture, "CIA Studies in Intelligence" Vol. 6, No. 3 (Summer 1962), pp. 55-76. Source: cia.org, accessed 12 August 2020. [pdf]. This is a slighly edited version of the original 12 February 1947 lecture, as first published in "Journal of the Royal United Services Institution", nr. 42, August 1947, pp. 352-360.
• Ref. 230U: "Radio navigation equipment", Section three of "Graphic survey of radio and radar equipment used by the Army Air Force", U.S. Army Air Forces, Air Technical Service Command, 1 May 1945, 68 pp. [file size: 21 MB].
• Ref. 230W: "Aerial Navigation and Traffic Control with Navaglobe, Navar, Navaglide, and Navascreen", H. Busignies, Paul R. Adams, Robert I. Colin, in "Electrical Communication - A Journal of Progress in the Telephone, Telegraph and Radio Art", published by "International Standard Electric Corp.", Vol. 23, No. 2, June 1946, pp. 113-143. Source: worldradiohistory.com, retrieved 17 August 2020.
• Ref. 230Y: "Radionavigation in the UK in World War II", F.C. Richardson, in "The Journal of Navigation", Vol. 45, Issue 1, January 1992, pp. 60-69. Source: en.booksc.org, accessed April 2021. [pdf, See note 1]
• Ref. 230Z: "Zielfluggeräte nach ‟Dieckmann-Hell‟" [Dieckmann-Hell airplane radio direction finding systems; Luftwaffe ZVG 15 / 16 / 17 Z, FuG 141], Werner Thote, in "Radiobote", Vol. 13, Nr. 76, September-October 2018, pp. 14-19. Source: radiobote.at.
• Ref. 241: "Erprobungsstellen der Luftwaffe" [Luftwaffe test sites, incl. Rechlin, Süd/Foggia, Tarnewitz, Travemünde, Udetfeld, Werneuchen]. Bestandsbeschreibung [file description] of Bundesarchiv file nr. (Signatur) RL 36. Retrieved 28 August 2019.
• Ref. 259: pp. 75-84 in "Zwischen Möhrenfeld und Panzerkute - verblassende Erinnerungen im märkischen Sand. Die märkischen Dörfer Groß- und Kleinbeuthen und ihre Umgebung in schwerer Zeit um 1945" ["Between carrot field and panzer pit - fading memories of the Brandenburg marsh sands - The Groß and Kleinbeuten villages and their surroundings during the hard times of 1945"], Bernd Saalfeld, self published book (available via Heimatverein Beuthen e.V.), 2018, 156 pp.
• Ref. 290: Documents from the Bundesarchiv-Militärarchiv (BArch-MA, BAMA) in Freiburg/Germany, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016":
• Ref. 290A: "Anregungen zur Vereinfachung, Weiterentwicklung und Störbefestigung des Bernhard-Verfahrens" ["Suggestions for simplification, further development and improved interference proofness of the Bernhard system"], E. Hammon, Reichsstelle für Hochfrequenzforschung e.V. [RHF; Reich's Agency for High Frequency Research], Ferdinand-Braun-Institut at Bad Aibling / Schloß Pullach, Dept. 1/I, 21 November 1944, 4 pp. Source: BArch/BAMA file nr. (Signatur) RL 39/282. Note: the BArch/BAMA file nr. (Signatur) RL 39/275 file folder contains an other original copy of this report.
• Ref. 290B: "Vorläufige Mitteilung über Störmöglichkeiten und Störmessung am System "Bernhard"" ["Preliminary report on interference possibilities and measurement of the effects thereof on the Bernhard system"], E. Hammon, Reichsstelle für Hochfrequenzforschung e.V. [RHF; Reich's Agency for High Frequency Research], Ferdinand-Braun-Institut at Bad Aibling / Schloß Pullach, Dept. 1/I, 23 November 1944, 14 pp. Source: BArch/BAMA RL 39/284 [file size: 18 MB]. Note: hand-written note on p. 1 of the actual document erroneously states "RL 39/283", which is an entirely different document.
• Ref. 290C: "Vorläufige Mitteilung - Beiträge zur Erhöhung der Störsicherheit beim System "Bernhard"" ["Preliminary report - Contributions to improved interference immunity of the "Bernhard" system"], E. Hammon, Reichsstelle für Hochfrequenzforschung e.V. [RHF; Reich's Agency for High Frequency Research], Ferdinand-Braun-Institut at Bad Aibling, 12 February 1945, 7 pp. Source: BArch/BAMA RL 39/275.

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