- [Telefunken UHF rotating beam systems]
- [Telefunken transition from UHF to VHF]
- [Development of VHF "Bernhard/Bernhardine"]
- [System characteristics]
- [Unknown/unclear aspects]
- [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.
©2004-2020 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: April-May 2020 (moved the entire radio direction finding/location/navigation section to a separate page)
Previous updates: 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).
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, 2, 3, 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.
- 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 1st, 6th, 7th, and 9th. The antenna rotated for a period of 2 hours 20 min during night of June 2nd, 4 hours 20 min during evening of June 3rd, 4 hours + 1 hour 25 min + 20 min during the early morning and early evening of June 5th, 2 hours 50 min late afternoon of June 8th. Ref. 173A.
During 1942-1944, RAF 192 Squadron (§9.3 in ref. 175) 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 at the end.
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. 3). 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. 3)
In these UHF installations, the transmitters did not rotate with the antenna system: they were located in the small stationary building below the antenna system. This arrangement requires a rotary coupler between the antenna system and the transmitters. This may have been implemented as a set of slip-rings on the shaft of the rotating antenna system. Note that a slip-ring approach ("HF-Schleifringkopplung") was actually used in several German systems, for instance the FuMG 404 "Jagdschloß" radar (designed by GEMA, built by Siemens). Ref. 151. The largest version had a 24 m wide antenna array system (4 x 16 horizontal dipoles) that weighed 25-30 metric tons. It rotated at 10 rpm, with the central shaft driven by a 75 kW 3-phase motor. It was a UHF system (120-240 MHz, depending on the version). It transmitted 1- 2 μsec pulses of 8-20 kW, with a pulse repetition frequency (PRF) of 500 / 3000 Hz.
However, there is also a 1936 Telefunken patent (nr. 767525), by Adalbert Lohmann. He was Telefunken's expert on rotary navigation beacons, including the Bernhard system. This patent is explicitly for the directional antenna system of the Telefunken rotating beacon station. It proposes a method for a contact-free rotary coupler: no contact resistance, no arcing at brushes! The coupler comprises two sets of stator and rotor disks that form capacitors. See Figure 16. The disks are installed coaxially: the rotor plates are fixed to a rigid shaft (preferably ceramic), and the stator plates to the housing of the coupler. The transmitters are wired to the edge of the respective stator plate. Note that in the VHF (30 MHz) Bernhard system, the transmitters are located on the same rotating platform as the antenna system. Hence, no rotary couplers were required for between the transmitters and the antennas. Of course, in this configuration, electrical power for the transmitters must be provided via slip-rings.
Fig. 16: Contact-free rotary coupler for RF signals
(source: the 1936 Telefunken/Lohmann patent 767525)
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. 3; 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).
I have used FontStruct™ to capture the above signal-level track and compass-rose segment as Feld-Hell character 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-rose.
Fig. 21: Re-created signal strength bar graph, azimuth data, and station identifier "M"
A station-identifier letter is also printed every 10 degrees (e.g., "R" and "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 textual command-uplink system! The messages followed the same format as fighter-control "Reportage" messages, that were normally broadcast via Morse code telegraphy and radio telephony (which was 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 beacon, and was only implemented at two or three stations by the end of the war.
Fig. 22: Re-created Bernhardine print-out with "Reportage" track instead of compass scale
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. 3 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.
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 at 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 Knickebein. 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. 25.
Table-2: FuG120 and FuSAn724/725 within the Luftwaffe equipment numbering system
(source: ref. 25)
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. 3, 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)
- There are references to a high-power version of the "Bernhard station": FuSAn 725, with 5000 watt transmitters. There is no evidence that these transmitters were ever developed and entered into service. Ref. 20 and 21 state that they were planned only.
- The wiring list of the "Bernhard" station contains several items with two wire gauge specifications: one for a 500 W transmitter, an a much heavier gauge for a 4000 W transmitter (not 5000 W!). E.g., cables nr. 6-8, 33, and 34, in ref. 189.
- Antenna system dimensions: ≈28 x 35 m (HxW, 92x115 ft).
- Rail track diameter: 22.6 m (74 ft).
- Weight of the rotating construction: 120 tons (265000 lbs), ref. 21, 181, 183; some literature states the weight as 102 tons (ca. 256000 lbs) which is probably a typographical error, or 100 tons (ref. 20).
- 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).
- Operational range as a function of aircraft altitude (with respect to the "Bernhard" antenna altitude):
Fig. 37: Operational range of the Bernhard/Bernhardine system vs. aircraft altitude
(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. Note: as FuSAn 725 never entered service, 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 British and US military and intelligence referred to this Radio Direction Finding (R.D.F.) system as "Windjammer" (ref.172, 173, 174). By mid-1943, they basically had the system construction and operating frequencies figured out correctly. Ref. 172A. However, a 1945 US "Intelligence" synopsis of the "Bernhard/Windjammer" system (p. 4.09 in ref. 13), confuses it with the "Y-System" ("Benito"), even towards the end of WW2. Contrary to the Bernhard system, the Y-System could provide "slant range", i.e., line-of-sight distance (not distance-over-ground) between the aircraft and the ground-station. The referenced frequency also belongs to the "Y-System" (42-48 MHz), not the Bernhard system (30-33.1 MHz).
Fig. 39: Flawed 1945 U.S. description of the "Bernhard" system
(source: ref. 13)
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)
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).
|Patent number||Patent office||Year||Inventor(s)||Patent owner(s)||Title (original)||Title (translated)|
|577350||RP||1932||E. Kramar||C. Lorenz A.G.||Sendeanordnung zur Erzielung von Kurslinien||Antenna arrangement for producing course lines|
|Telefunken GmbH||Antenneanordung zur Aussendung von zwei oder mehreren einseitig gerichteten Strahlen||Antenna arrangement for transmission of two or more uni-directional beams|
|737102||RP||1935||W. Runge||Telefunken GmbH||Anordnung zur ständigen Kontrolle und zur Ein- bzw. Nachregulierung der geometrischen Lage eines Leitstrahls während des Leitvorganges||Arrangement for monitoring and adjustment of the location of a directional beam|
|767354||RP||1936||-||Telefunken G. für drahtlose Telegraphie m.b.H.||Verfahren zur Richtungsbestimmung||Method for direction-finding [this is the primary "Bernhard" patent]|
|767528||RP||1936||A. Lohmann||Telefunken GmbH||Verfahren zur Richtungsbestimmung||Method for direction finding [optical disks, quadruple antenna]|
|730635||RP||1937||R. Hell||Dr.-Ing. Rudolf Hell||Verfahren zur Registrierung des Verlaufes veränderlicher Stromkurven||Method for printing the trace of varying signals [Hell printer for signal-level track of Bernhardine]|
|767512||RP||1938||-||Telefunken GmbH||Verfahren zur Richtungsbestimmung mittels rotierender Richtstrahlung||Method for direction finding by means of a rotating directional beam|
|Telefunken GmbH||Empfangseinrichtung zur Durchführung des Verfahrens zur Richtungsbestimmung||Receiver-side device for the implementation of the method for direction-finding|
|767524||RP||1938||A. Lohmann||Telefunken GmbH||Verfahren zur Richtungsbestimmung mittels rotierender Richtstrahlung||Method for direction-finding with a rotating directional beam|
|767525||RP||1938||A. Lohmann||Telefunken GmbH||Einrichtung zur Speisung eines rotierenden Richtantennensystems||Device for capacitive coupling of a transmitter to a rotating directional antenna system|
|767526||RP||1938||A. Lohmann||Telefunken GmbH||Verfahren zur Richtungsbestimmung||Method for direction finding|
|767527||RP||1938||A. Lohmann||Telefunken GmbH||Einrichtung zur periodischen Ein- bzw. Ausschaltung einer Registriervorrichtung||Device for switching on and off of a printer|
|Telefunken GmbH||Einrichtung zur Erzeugung angenähert rechteckiger, zur Modulation des Kennzeichensenders dienender Abtastimpulse bei einem Verfahren zur Richtungsbestimmung mittels Drehfunkfeuer||Device for the generation of an approximately square pulse envelopes, for the direction finding method by means of a rotating beacon|
|767530||RP||1938||A. Lohmann||Telefunken GmbH||Verfahren zur Richtungsbestimmung||Method for direction-finding [frequency shift for beacon tone frequencies]|
|767537||RP||1938||A. Lohmann||Telefunken GmbH||Anwendung des Peilverfahrens nach Patent 767354 für die Standortbestimmung||Application of the direction finding method of patent 767354, for position finding [printing of two beacons for triangulation]|
|767531||RP||1939||A. Lohmann||Telefunken GmbH||Verfahren zur Richtungsbestimmung||Method for direction-finding [dipole antenna array arrangement with side-lobe suppression]|
|767936||RP||1938||Benno Johannesson||Telefunken GmbH||Verfahren zur Ortsbestimmung||Method for position determination [triangulation with a single receiver + Bernhardine printer, synchronized rotation of multiple Bernhard stations with fixed angular offsets between them]|
|767532||RP||1939||A. Lohmann||Telefunken GmbH||Sendeanordnung zur Durchführung eines Verfahrens zur Richtungsbestimmung||Antenna arrangement for the implementation of a method for direction finding|
|767513||RP||1939||A. Lohmann||Telefunken GmbH||Empfangsseitige Schreibvorrichtung zur Durchführung eines Verfahrens zur Richtungsbestimmung [Wachsschreiber]||Receiver-side printer for the implementation of a method for direction-finding [wax printer, infinite loop, erasable tape]|
|767514||RP||1939||A. Lohmann||Telefunken GmbH||Antennenanordnung zur Durchführung eines Verfahrens zur Richtungsbestimmung||Antenna configuration for performing a direction-finding method; ; addendum to main patent RP 767354 [The narrow twin-beams of the UHF Bernhard hav many vertical lobes due to ground reflections; interlaced single- & twin-beam dipole arrays]|
|767538||RP||1939||A. Lohmann||Telefunken GmbH||Anwendung des Verfahrens nach Patent 767354 für die Standortbestimmung||Application of the method of patent 767354, for position finding [receiver/printer arrangement for triangulation with two beacons]|
|767937||RP||1939||A. Lohmann||Telefunken GmbH||Einrichtung zur Durchführung eines Verfahrens zur Richtungsbestimmung||Device for implementation of a process for direction finding [multi-track optical disk for quick change of identifier]|
|767534||RP||1940||A. Lohmann||Telefunken GmbH||Verfahren zur Richtungsbestimmung||Method for direction-finding|
|767515||RP||1940||A. Lohmann||Telefunken GmbH||Anwendung des Registrierverfahrens nach Patent 767354 für ein Verfahren zur Führung eines Luftfahrzeuges während des Landungsvorganges||Application of the printing method per Patent 767354 for a method for aircraft guidance during landing|
|767536||RP||1940||A. Lohmann||Telefunken GmbH||Empfangsseitige Schreibvorrichtung zur Durchführung eines Verfahrens zur Richtungsbestimmung||Receiver-side printer for the implementation of a method for direction-finding|
|767919||RP||1940||H. Muth||Telefunken GmbH||Verfahren zur Richtungsbestimmung unter Verwendung eines rotierenden Funkfeuers||Method for direction-finding with a rotating beacon [using only twin-lobe beam]|
Table 1: "Bernhard/Bernhardine"-specific patents
Here are some ancillary patents:
|Patent number||Patent office||Year||Inventor(s)||Patent owner(s)||Title (original)||Title (translated)|
|562307||RP||1929||J. Robinson||J. Robinson||Funkpeilverfahren||Method for direction finding [transmission of course-pointer, or compass rose info via Nipkow-video]|
|620828||RP||1933||-||C. Lorenz AG||Funkpeilverfahren||Method for direction finding [transmission of compass rose info via Nipkow-video]|
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 about the (never finished) Bernhard 30 m / Bernhaube (FuSAn 713) system (see p. 224 in ref. 2), operating on a frequency around 10 MHz (a wavelength of 30 m, which suggests larger antenna systems than for the 30 MHz / 10 m "Bernhard"). Apparently it used electronic beam steering instead of a rotating antenna system. Supposedly, the FuG 10 radio system was used in the aircraft, but that radio set had a maximum frequency of 6 MHz...
- 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: pp. 76-110, 224 in "Die deutschen Funkführungsverfahren bis 1945", Fritz Trenkle, Alfred Hüthig Verlag, 1987, ISBN 3778516477, 215 pp.
- Ref. 3: pp. 94-102 in "Die deutschen Funk-Navigation und Funk-Führungsverfahren bis 1945", Fritz Trenkle, Motorbuch Verlag, 1995, 208 pp., ISBN-10: 3879436150.
- 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", 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: "Radio and Radar Equipment in the Luftwaffe - II, Navigational Aids", S.D. Felkin, A.D.I. (K) Report No. 357/1945, 1945, 18 pp.
- Ref. 6E: "Equipment of a Y-Site", 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. 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, 1955, pp. 351-360.
- Ref. 7B: Part 2 (pp. 387, 388, 392): Vol. 9, Nr. 11, 1955, pp. 386-395.
- 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 Manual for Radio-Navigation System FuG 120 "Bernhardine", with 2-channel Hellschreiber radio-navigation printer], Telefunken G.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. 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, 4th ed., Deutsche RADAR-Verlagsgesellschaft m.b.H., 1957, 160 pp.
- Ref. 21: "Bordfunkgeräte - vom Funkensender zum Bordradar", Fritz Trenkle, Bernard und Graefe Verlag (publ.), 1986, 283 pp., ISBN 3-7637-5289-7
- Ref. 21A: p. 61-63, "Kommandoübertragungszusätze".
- Ref. 21B: pp. 97-103, "Leitstrahl-Verfahren" (beam methods).
- Ref. 21C: photo "Große Knickebein Anlage bei Kleve", p. 108 [note: incorrectly identified by Trenkle as station K4 at Kleve, instead of K2 at Bredstedt]
- Ref. 21D: "Drehfunkverfahren", pp. 119-130
- Ref. 25: "Verzeichnis deutscher Bordfunkgeräte aller Art (einschl. der mit Fu G-Nr. belegten akust. und UR-Geräte)". "Kenntnis der Allierten von deutschen Bordfunkgeräten (Winter 1944/45, nach engl. amerik. Anweisungen zur Auswertung deutscher Beutegeräte, Stand Februar 1945" [list of German on-board radio equipment, incl. acoustic and infrared; list of equipment types/models captured by Allied forces]. Manuscript notes of Fritz Trenkle, incl. for "Funkgeräte Katalog Deutschland 1908-1918 und 1919-1945", 44 pp. Source: Archives of Deutsches Technik Museum Berlin, retrieved from www.deutscheluftwaffe.com on 19 February 2020. [pdf]
- Ref. 151: p. 16, 17, 22 in "Jagdschloß A (Lehrunterlagen) Teil I", 2nd ed., Lehrschule für Fernmeldetechnik, Detmold, November 1944, 115 pp. Source: www.cdvandt.org
- Ref. 164: "Institutes of the Bevollmaechtigter fuer Hochfrequenz-Forschung", Combined Intelligence Objectives Sub-Committee (CIOS), Item No. 1 & 7, File No. XXXI-37, May 1945, 215 pp.; source: cdvandt.org
- 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 20th June 1944, 1 page.
- Ref. 173B: "Possible "Windjammer" transmissions", report by Flight Lieutenant Douglas of 192 Sq., dated 16th December 1943, 1 page.
- Ref. 173C: "192 Squadron Flight report No. 215/43" by F/Lt Robinson to Squadron Leader Burtler, dated 15th November 1943 (actual report by P/O G.F. Evans of 13th 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 16th July 1943, 1 page + 1 aerial photo.
- Ref. 173E: "The Windjammer and Dreh-Elektra", by 192 Squadron Leader J. Whitehead, dated 18th 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 9th April 1943, 1 page + 1 photo
- Ref. 174B: Aerial photo of station "Bergen/Belvedere" [The Netherlands], photo No. 3022, taken 22rd 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 9th 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 15th 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 29th March 1943, 1 page + 1 photo.
- Ref. 174F: "Interpretation Report No. G. 308" dated 28th June 1942, of aerial photos taken over Desvres/Le-Bois-Julien at altitude of 20k ft during Sortie A/945 on 20th June 1942, 1 page + 1 photo.
- Ref. 174G: "Interpretation report No. G.590" dated 6th 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 24th 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 29th March 1943, 1 page + 3 photos.
- Ref. 174J: Photos No. 4065 and 4066 of station at St. Vaast / La Pernelle, taken 31st March 1943 from off shore. [station is fully, though vaguely, visible on horizon]
- Ref. 175: 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)", 1st 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. 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", 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.
- 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" [Radio-beacon aids to aerial navigation], 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", C. Powell, in "Journal of the Institution of Electronic and Radio Engineers (IERE)", Vol. 56, Nr. 8-9, August/September 1986, pp. 293-297.
- 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, 2nd 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. 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-07553.
- 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: "Pulling the crooked-leg", R.V. Jones, in "New Scientist", 23 February 1978, pp. 493-496.
- Ref. 230D: "Most Secret War", R.V. Jones, Hamish Hamilton (publ.), 1978, 576 pp. See note 1
- Ref. 230E: "Milestones - Battle of the Beams", Carlo Kopp, in "Defence Today", January/February 2007, pp. 76, 77.
- Ref. 230F: "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.
- Ref. 230G: "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. 230H: "Radio Navigation Systems for Aviation and Maritime Use — A Comparative Study", 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. 230H1: "Radio Direction-Finding on Board Aircraft and Ships", W.T. Runge, pp. 19-28.
- Ref. 230H2: "Consol and Consolan", Ernst Kramar, pp. 29-39.
- Ref. 230H3: "VOR-System", K. Bärner, pp. 43-57.
- Ref. 230H4: "Decca". H. Lueg, pp. 81-101.
- Ref. 230H5: "Standard-Loran", Ernst Kramar, pp. 113-118.
- Ref. 230J: "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. 230K: "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: BArch file nr. (Signatur) RL 2-V/48, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
- Ref. 230L: "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: BArch file nr. (Signatur) RL 2-V/6, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
- Ref. 230M: "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: BArch file nr. (Signatur) RL 2-V/6, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
- Ref. 230N: "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.
- Source: BArch file nr. (Signatur) RL 2-V/5, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
- Ref. 230P: "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.
- Source: BArch file nr. (Signatur) RL 2-V/5, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
- Ref. 230Q: "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.
- Source: BArch file nr. (Signatur) RL 2-V/5, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
- Ref. 230R: "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. 241: "Erprobungsstellen der Luftwaffe" [Luftwaffe test sites, incl. Rechlin, Süd/Foggia, Tarnewitz, Travemünde, Udetfeld, Werneuchen]. Bestandsbeschreibung [file description] of Bundesarchiv file nr. (Signatur) RL36. 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", Bernd Saalfeld, self published book (available via Heimatverein Beuthen e.V.), 2018, 156 pp.
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