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©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: March-2020 (started complete overhaul & expansion of the entire radio direction finding/location/navigation section).

Previous updates: January-February 2020 (added Fig. 3B, Fig. 42, ref. 244A-244Q, ref. 185, 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).


red-blue line

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, 2, 3, 5, 6, 7A, 8, 85C, 164 (p. 30), 181, 183, 184Q. 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).

Bernhard Bernhardine system diagram

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).

Bernhard beam concept Rotating beacon cartoon

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.


Bernhard sound

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.

UHF beacon

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:

UHF beacon

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).

X station

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

(modern national borders)

UHF beacon

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.

UHF beacon

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.

UHF beacon

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):

Bernhard antenne pattern

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:

UHF beacon

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:

UHF beacon

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").

UHF beacon

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:

UHF beacon

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).

UHF beacon

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.

Bernhard antenna system

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.

UHF beacon

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.

Triangulation

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.

Patin remote compass

Fig. 20A: Remote compass, as used in Fw190 etc.

(made by A. Patin & Co. G.m.b.H. of Berlin)

Bernhard compass card

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.

":Bernhardine" compass card

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.

Bernhard reportage track

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:

UHF beacon

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. 184W)

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.

UHF beacon

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.

Berhard station

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):

Berhard station

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).

UHF beacon

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.

UHF beacon

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.

UHF beacon

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):

Berhard station

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

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

Berhard station

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).

Berhard station

Fig. 32: The inside of the brick building

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

Berhard station

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.

Berhard station

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.

Berhard station

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. 185.

FuG 100-150

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

(source: ref. 185)

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:

Bernhard development time-line

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):

Bernhard system range vs. altitude graph

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).


Berhard station

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. 712 A. 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).

Bernhard description US
Bernhard description US

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).

FuG120

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)


RADIO DIRECTION FINDING, LOCATION, AND AIR NAVIGATION THROUGH WW2

Clearly, the Bernhard/Bernhardine system is a "rotating radio beam system" for aircraft navigation and guidance. But where does this system fit, within the domain of "Radio Direction Finding" (D/F), Radio Location, Radio Guidance and Navigation", and the associated history through the end of World War 2?

First, we need to introduce some basic terminology regarding air navigation (which, of course, is very similar to nautical navigation). Rather than describing this textually, I will let the figure below speak for itself:

Terminology

Fig. 41: Some basic terminology of air navigation


Directional radio-frequency (RF) waves were discovered during the late 1880s. Starting in the early 1900s, concepts, techniques, and devices were invented and developed, to apply RF to direction-finding and navigation. So, we have to introduce some more terminology:

  • Radio direction finding (RDF). As the name suggests, this is a technique for determing the direction to or from a radio transmitter. I.e., determining Angle of Arrival (AoA) or Angle of Depature (AoD), respectively. The transmitter station can be fixed-base (stationary) or mobile, and cooperative or not ( = "enemy"). The direction is measured and expressed relative to a reference direction at the D/F station or at that transmitter station. The reference direction is typically True North, Magnetic North, or the longitudinal axis of the vehicle (ship, aircraft, land vehicle, surfaced submarine). A distinction is sometimes made between:
  • RDF ("Fremdpeilung"): RDF-ing of a mobile transmitter station by a receiver station with known position.
  • Reverse-RDF ("Eigenpeilung"): RDF-ing by a mobile receiver station of a fixed transmitter station with known position.
  • Radio location, a.k.a. radio positioning: determing the position (own or of a target) by radio means. This is also known as taking a "position fix", or "fix" for short. The position can be the absolute 2D position within some coordinate system on the face of the earth, or a relative 2D position ( = D/F direction + distance/range), or the 3D position of an aircraft ( = 2D position + altitude).
  • Radio navigation, in particular in-flight. One of the mantras that I remember well from my own pilot training, is about the top priorities of every pilot/navigator: always "aviate" ( = fly the airplane), "navigate" ( = figure out where you are, where you're going, and how to get there in 4D), "communicate" (with ATC) - in that specific order of importance. Radio navigation is pre-dated by other forms of navigation, even though those were/are also used by airplane navigators, in particular on trans-oceanic and trans-polar routes, out of range of radio nav stations:
  • Pilotage: visual navigation by reference to landmarks and man-made objects on the ground (or in the water).
  • Celestial navigation: based assessing the angle between one or more celestial bodies (stars, sun, moon, planets) and the horizon. This method has been used by mariners since ancient times. Most of these methods require the knowledge of time (e.g, local noon).
  • A related technique is Dead Reckoning (DR). It estimates the current position, based on a previous position fix (or known position), and an estimated position-change. The latter is based on estimated speed, direction, drift and elapsed time since that previous fix. The same approach can be used to estimate position at some time in the future, based on current position (known or estimated) and conditions.

Clearly, the above radio-based activities are of strategic and tactical importance during times of armed conflict, and preparation therefore. Which also explains why corresponding RF-based countermeasures (interference, jamming, locate-and-destroy, etc.) have a similar level of importance.

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

Note that with a single transmitter/DF-station pair, only a direction ( = angle) can be determined - not position. The result of D/F-ing is basically a continuous straight line of possible positions, emanating from the position of the D/F station, through the position of the transmitter, and beyond. This is a linear Line of Position (LoP). See the left-hand panel of Figure 42 below. Important: without further information, the position of the target on an LoP is not known! For a given position of the D/F or transmitter station, the LoP can be drawn on a map ("chart" in navigation parlance).

Line of Position

Fig. 42: Linear, circular, and hyperbolic Lines of Position


Some other RF methods do not determine direction, but rather the distance ( = range) between an observer/anchor station and the "target". All points with the same distance to the anchor station now lie on a circle that is centered on that station. That is, all these points combined form a circular LoP. See Figure 42. Again, without further information, the target's position on an LoP is not known. Through air and space, radio waves propagate at the speed of light: close to 300000 km/sec, or close to 30 cm ( = 1 foot) per nanosecond. Now you know how long a nanosecond is! This finite-speed property makes it possible to use radio waves for determing distance: speed x time = distance traveled. The standard methods are as follows:

  • An fixed or mobile anchor station transmits a radio-wave pulse. That pulse is scattered from, and reflected by, the surface of the target. The target may be a cooperative/friendly, or non-cooperative/enemy aircraft, ship, land vehicle, or surfaced submarine. A reflected pulse is received back at the anchor station. The pulse has made a round-trip. The total time-of-flight (ToF) to and back from the target covers twice the distance between station and target. By measuring the time-difference (delay) between transmitting a pulse and receiving the echo, that distance (a.k.a. "range") is known. This is the "ranging" ("Enfernungsmeßung") part of what is called "Radio Detection and Ranging" (a.k.a. "radar") since late-WW2. The range from a radar station on ground to an airborne aircraft is actually "slant range", which is not the same "down range". The latter is distance-over-ground, measured along the earth's surface, to the point on that surface, directly below the aircraft.
  • Rather than bouncing a radio pulse of a target, an "interrogator" station can transmit a pulse (or coded sequence thereof), and a compatible mobile "transponder" station replies with another pulse (or sequence thereof) on the same or (usually) different radio frequency. Transponders typically apply a pre-defined reply-delay. Again, half the round-trip time (minus any reply-delay) is equivalent to slant range.
  • The interrogator and transponder roles can be reversed: an airborne interrogator and a ground-based transponder. The latter is often co-located with a radio navigation beacon. The common post-war implementation of this is called Distance Measuring Equipment (DME).
  • In the world's first transponder-based ranging system (patented in 1927 by Koulikoff & Chilkowsky), there were two interrogator/transponder stations. One initiated a pulse, and from thereon, the two stations ping-ponged the pulse. The resulting beat-tone was a measure of the distance between them.
  • Instead of transmitting and replying with a pulse signal, it is also possible to transmit a tone-modulated continuous wave (CW) signal, have the transponder send this back (typ. with a reply-delay) on a different frequency, and measure the phase-difference between the two signals. This round-trip difference represents a time-shift, hence distance. To avoid distance ambiguity, the wavelength of the transmitted tone has to be longer than the round-trip distance. E.g., a 10 kHz modulation tone has a wavelength of about 33 km (≈20 statute miles).

OK, just one more type of LoP to discuss! Above, we covered using the "time-difference = 2x round-trip distance" approach. It resulted in circular LoP's. This can be expanded to a system with not one but two anchor stations with known position. Of this station pair, one is referred to as the "master", the other a "slave". The master transmits an omnidirectional pulse. Upon receipt, the slave also transmits a pulse, on the same frequency. I.e., the slave is synchronized to the master. Both pulses are received by the target, where they arrive at slightly different times. Again, we have a time-difference (Time-Difference-of Arrival, TDoA). However, now this time-difference is equivalent not to a distance, but to a distance-difference! It is the difference between 1) the distance between the target and the master station, and 2) the distance between the target and the slave station. All points that have the same absolute distance difference, lie on two open curves. They are two branches of one hyperbola. The two anchor stations are the "foci" of the hyperbola. The two mirror-image curves of each hyperbola pass symmetrically between these foci. In fact, as with the linear and circular LoPs, there is an infinite family of LoP's. In this case, covering all possible distance-differences. Depending on the +/- sign of the distance difference, the target lies on one curve or on the other. So, we now have hyperbolic LoP's. See Figure 42.

In analogy with the various circular LoP methods, the same hyperbolic LoP's can also be created by pair of master-slave anchor stations that transmit a continuous-wave carier signal instead of pulses. Again, the slave is synchronized to the master. But now the LoP represents a fixed phase difference between their (continuous) transmissions, instead of a fixed time difference between pulse-pair receptions. But a phase difference between two sinewaves (audio or RF) of the same frequency is equivalent to a time difference.

As repeatedly mentioned above, without further information, the position of the target on an LoP is not known. It could be anywhere on the LoP - within the reception coverage area of the radio aids. How can this be resolved? By combining two or more independent lines of position into a point of position (PoP). For this approach to work, we need LoP's that intersect. I.e., LoPs that cross, or at least touch each other. This can be achieved with linear, circular, and hyperbolic LoP's, as illustrated in Figure 43:

Line of Position

Fig. 43: Combining Lines of Position for position


It should be intuitively obvious from this figure, that creating an accurate, clear and concise equivalent textual description is a rather tall order, and not necessarily more comprehensible or instructive. So, I will not attempt to do so. That said, a couple of words anyway...

The case of "crossing linear LoP's" is standard classical triangulation, used since many centuries, if not millenia. Note that it works both ways: two (or more) fixed D/F stations can determine the position of a mobile transmitter. This was also done in the early days of radio D/F, and the position estimated by the D/F stations was reported to the transmitter station (ship, airship) via radio. Conversely, a mobile D/F station can determine its own position by using two (or more) beacon stations with known position. Accuracy ( = uncertainty) of the position estimate depends primarily on the angle between intersection LoPs. I.e., distance between the beacon pair or D/F station pair, as wel as the distance from the target to the baseline between the beacon or D/F station pair.

We can also combine a linear LoP (bearing) and a circular LoP (range). These two LoP's can be obtained with two spatially separated anchor stations: one D/F station and one range-finding station. Once can also combine a linear LoP and a circular LoP  into a single system, at a single anchor station. Radar is a prime example of this. Two independent and spatially separated range-finding stations generate two overlapping circular LoP's. Conversely, a mobile interrogator station may determine the range to two spatially separated transponder stations with known position. Generally, two overlapping circles intersect at two points, not one - unless the target is located exactly on the straight baseline between the two anchor stations. I.e., there generally is ambiguity as to which of these two points is the actual position of the target. Overlapping hyperbolic LoP's can also have two intersect points.

Of course, the concept of positioning by means of intersecting LoP's also applies to hyperbolic LoP's. This is done with a chain of (at least) three anchor stations, one of which is the master to which the remaining stations of the chain are synchronized. Early such systems used maps (charts) with a lattice of hyperbolic LoP's, like the pink and light blue lines in the right-hand panel of Fig. 43 above. Each line of the lattice was marked with the associated time-difference.

Note: all necessary basic methods for, and concepts of, radio D/F and radio location/positioning were patented by 1935! See the time-line diagram below:


time-line

Fig. 44: Time-line of primary radio direction-finding/location/navigation patents through 1935

(source: patent table-3)


Note: basically nothing fundamentally new has been added by subsequent radio D/F, positioning, and navigation methods, including those that are based on satellites, WiFi networks, mobile/cellular telephone networks, etc!

The remainder of this section is currently (April 2020) still in the process of being overhauled and significantly expanded.

Doppler  type of LoP?? Shift only measures radial speed/velocity component of target; need multiple (physically or electrically) co-rotating antennas to determine direction and position.

.... when Otto Scheller of the Lorenz company invented the "Wireless course indicator and telegraph" system (Imperial Patent nr. 201496 of 17 March 1907; also consider patent nr. 192524 of the same date), ref. 184A. At that time (before the widespread advent of aviation), the system was intended for guiding ships. The ground-station of the Scheller system had a radiation pattern with four main lobes, in fixed orthogonal directions. See Figure 41A. Two of the lobes transmitted the Morse code letter "A" ( = "dot dash"), the other two the letter "N" ( = "dash dot"). Where lobes overlap and are of equal strength, the combination of "A" and "N" results in a constant tone signal (D: "Dauerton"): the so-called "equi-signal". This signal had a beam width of about 1-5°. This was the first "A/N" system, later used in several other Lorenz radio-navigation systems. Subsequent variations of this scheme used narrow "A" and "N" beams, with a much narrower overlap, allowing more accurate determination of the course line of the equi-signal. In the 1907 Scheller patent, the directional radiation patterns are obtained with four equidistant vertical antennas. This 2-pair antenna configuration was "borrowed" over a decade later by Frank Adcock, as part of his 1919 Direction Finding (DF) patent (GB 130,490). He also proposed a configuration with elevated vertical dipoles (not practical for LF/MF/HF frequencies) instead of monopoles, and added compensation/elimination of the , resulting in a "2 crossing H's" configuration.


Lorenz-Scheller A/N system

Fig. 44: The 1907 Scheller patent and the Lorenz-Scheller A/N system

(the Scheller patent uses two pairs of vertical antennas, the A/N system uses two crossed loop antennas)

Rotating-beam radio-navigation beacons are the radio equivalent of common optical rotating beacons: lighthouses. In 1907, Austrian-born Alexander Meißner (also spelled Meissner) invented a rotating-beam beacon: the "Kompass Sender" (radio compass, lit. "compass transmitter"). Ref. 187A-187G, see German Reichspatent 1135604. He also pioneered transmitters using radio tubes/valves instead of mechanical generators or spark-gaps, and invented the feedback-based oscillator around the same time (1912/13) as Lee de Forest, E. Reisz, C.S. Franklin, H.J. Round, E.H. Armstrong, and I. Langmuir. The "Kompass Sender" was developed by the Telefunken company, and used for long-range navigation of dirigibles built by Zeppelin and Schütte-Lanz (ref. 1, 2, 184Q, 184R, 184S). A complete network of 33 of these beacons, stretched along the entire very long border of Germany at that time, was already foreseen in 1912 (ref. 187A, 187B, 187H).

The antenna system comprised 16 dipoles of 2 x 60 m (≈2 x 200 ft), and a motorized antenna switching system. The dipoles were arranged in a star configuration, i.e., one for every 11¼ degrees. The center of this star, the feedpoint of te dipoles, was raised more than the tips of the dipoles. These days, such dipoles are called "inverted-V" dipoles. This made the dipole-arrangement look like the ribs of an umbrella. Hence, this type of antenna system is also referred to as an umbrella antenna ("Schirmantenne").

1907 - TFK Rotations-Senderapparat der Telefunken-Kompaßstation in Berlin-Gartenfeld (spelled Gartenfelde in old Telefunken publications; the area was acquired by Siemens late 1910, became part of Siemensstadt, southwest corner of Berlin-Tegel airport) ; note the two slip rings just below the rotating arms of the commutator, for transferring the signals from the stationary transmitter.

Telefunken Kompass-Sender

Fig. 3A: The 1907 "Meißner" motorized distributor/commutator of an early Telefunken Compass "Kompass Sender"

(source: ref. 187C; also ref. 187D, 187F)

Telefunken Kompass-Sender

Fig. 3B: The Telefunken radio compass transmitter station with its "umbrella" antenna

(source: Fig. 3 in ref. 187C (left) and ref. 187E)

Individual dipoles were successively connected to the transmitter via a motorized distributor that turned at 2 rpm (1 revolution every 30 sec). The switching sequence created a rotating dipole radiation pattern (a horizontal "figure 8", with two null´-directions). with a constant signal. Once per revolution, at the "north" position, the station identifier was sent in Morse code via all dipoles simultaneously (omni-directional). Meißner later replaced the rotary switch with a contactless goniometer arrangement. It consisted of a rotating "search" coil that sequentially coupled inductively to the stationary feed-coil of each dipole.

Telefunken Kompass-Sender

Fig. 3C: Priciple of the "Telefunken-Kompass-Sender" rotating-beam beacon

(source: H.-P. Scholz, wikimedia, Creative Commons Attribution 2.0 Germany)

Telefunken Kompass-Sender

Fig. 3D: The special 30-sec stopwatch of the "Kompass Sender" system

(source: adapted from Fig. 2 in ref. 187D)


Bearing (azimuth, relative direction) from the beacon is determined by measuring the time between the "north" marker and passage of signal minimum. This was done with a calibrated 30 sec stopwatch that had a compass rose on the dial. As the radiation pattern of a dipole is shaped like a figure "8", it has two identical minima. Hence, a 180 degree ambiguity. The ambiguity is resolved by determining the bearing from another beacon (triangulation). With the 2 x 60m "half wavelength" dipoles, the spark-gap transmitter generated a signal in the medium wave band (a wavelength of around 240 meter, equivalent to a frequency of 1250 kHz). "Telefunken Kompaß" is the complete system: "Kompass Sender" beacon + ordinary radio receiver + special stopwatch. Note that the stopwatch does not have a conventional hand (needle), but a double one across the entire watch face. This corresponds to the two null-directions of the rotating beam, and the associated 180° ambiguity. The system achieved an accuracy of about 3°. The system was operational through the end of WW1 (1918). Stations were installed at Bedburg-Hau (a village near Kleve in Germany, spelled Cleve until a spelling reform in July of 1935), and at Tönder (Tønder/Denmark before 1864 and after WW1) with its German Imperial Navy airship base.

During 1932/33, Ernst Kramar of the Lorenz company applied the concept of the Lorenz-Scheller A/N-system to a "blind landing system" for aircraft. Ref. 28, 184U, 184V, 188. Note that "blind landing" is a misnomer, as the system did not provide precision vertical guidance down to the actual landing. Hence, it is only an approach-beacon (D: "Ansteuerungsfunkfeuer", AFF). These days, we would refer to this beacon as a non-precision "localizer" approach system: the horizontal ( = lateral) component of an Instrument Landing System (ILS).

Blind landing: OK, at that time, without accurate ILS, is was possible to do so successfully in a small and slow airplane, with a forgiving landing gear that designed for unpaved runways (e.g., Junkers Ju-52 transport airplane, with a landing speed of a mere 95 km/h, 51 kts). This is akin to the procedure for landing on absolutely flat calm water, so-called glassy water. From above, such flat water looks like a mirror and it is impossible for the pilot to get a sense of depth and judge height above the watery runway. I enjoyed practicing this for my pilot rating for seaplanes & flying-boats!

Rather than using the complementary Morse letters "A" and "N", this system simply used "E" ( = "dot") and "T" ( = "dash"), or even "F" ( = "dot dot dash dot") and "L" ( = dot dash dot dot"). The antenna system was simple: a vertical dipole, with a vertical reflector to the left and to the right, at a distance of ¼ λ. See Figure 42. This was patented in 1932 (Reichspatent 577350). Kramar's 1937 patents expand this with a complementary-keyed (e.g., E/T) beam system for vertical guidance. This was simply re-patented in 1940 in the USA by others.

Lorenz-Schiller A/N system

Fig. 43: The Lorenz-Scheller A/N system ("Lorenz Beam") and associated antenna arrangement

(source: ref. 31)

Lorenz-Schiller A/N system

Fig. 44: The Lorenz-Scheller A/N beacon ground station

(source: image left - ref. 31, image right - ref. 184X)

The two reflector dipoles were activated alternatingly, to deform the dipole beam slightly to the right and to the left. This effectively created a directional beacon ("Richtfunkfeuer") with a twin-beam radiation pattern. At the centerline of the beams (aligned with the centerline of the runway), the "E" and "T" beams would merge into an 1150 Hz equi-signal zone that had an aperture of about 5 degrees. The antenna system was located at the far end ( = departure end) of the runway, so as to provide left/right guidance throughout the entire approach, landing, and roll-out. During approach to landing, the arriving aircraft would intercept and track the equi-signal beam. The beam-system operated at frequencies in the 30 - 36.2 MHz range (λ ≈ 10 m). The pilot would hear the E/T audio signals, and also have a Left/Right course deviation indicator. At two fixed distances from the runway, a marker-beacon ("Einflugzeichenbake", EFZ-Bake) was installed. An Outer Marker ("Vor-EFZ") at 3 km, and a Main Marker ("Haupt-EFZ") at 300 m, ref. 32. These beacons transmitted on 38 MHz, with a narrow upwardly pointing fan-beam, extending across approach course and at right angles to it. This allowed the pilot to determine when to initiate descent to the runway from a standard altitude and with a standard descent rate (3 degrees flight path). Ref. 184R1-R4, 26B. This "Lorenz beam" system entered service in 1934 with the German national carrier, Lufthansa (actually "Luft Hansa", until its post-war re-start in 1953). It was then commercialized worldwide. In the UK, it became the "Standard Beam Approach" (SBA) system. By 1938, some 38 of these beacons were installed at airports throughout the German Reich. The above beacon provides lateral ( = horizontal, left/right) guidance. In 1937, Lorenz/Kramar created a separate system for providing vertical approach-to-landing guidance, by turning the antenna system 90 degrees and placing it next to the runway, abeam the touch-down point. The combined system with lateral- and vertical-guidance beams is called Instrument Landing System (ILS). It is used to this day. For a general treatise of such beam systems by Ernst Kramar himself, see ref. 254 (1938).

A/N system

Fig. xx: Intercepting (with overshoot) and flying an A/N beam of a Four-Course Range

(source: National Air & Space Museum, Smithsonian Institution, "Time & Navigation - Navigating in the Air", 2012, artist: Bruce Morser)

The following audio clip is the realistic simulation (incl. keyclick suppression) of the receiver sound that would be heard when being on the "A" side of the equibeam of a Four-Course Radio Range AN-beacon. The "N" signal is also heard, but much weaker. As it is complementary to the keying of the "A" signal, it sounds like a continuous background signal. In the middle of the clip, there is a 3-letter Morse code identification (here: ABC), transmitted sequentially on the "A" and "N" beam. Tone frequency is 1020 Hz.

Four-course AN beam sound...

Audio simulation for the A side of  an LF Four-Course Radio Range - also receiving (weak) N-beam signal

(source: © Bob Denny, accessed 27 March 2020)

Scheller-Lorenz A/N beam sound - audio file still to be created...

Simulated sound of crossing an A/N beam back & forth and approach beacons - TBD!!!

(source: © ipse)

The "Lorenz Beam" was designed for flying a specific course-line towards a short-range beacon that had relatively wide beam-aperture (5º). In 1932, Dr. Johannes (Hans) Plendl of the Deutsche Versuchsanstalt für Luftfahrt (DVL, German Aviation Test Establishment) already identified the need for a directional beam system, to guide bombers to a target along a course-line away from the beacon, at night and in poor weather (visibility) conditions. Plendl was the national commissary for RF research ("Bevollmächtigte für Hochfrequenzforschung") from November 1942 until December 1943, and also headed up the national agency for RF research "Reichsstelle für Hochfrequenzforschung" (RHF) that was established mid-1943.

Plendl's concept used two directional beacons, sufficiently spaced apart. The centerline of their beams crossed each other at the target. Plotted on a chart, the two beam lines form a big "X". Hence, this concept was referred to as the "X-Method" ("X-Verfahren"). The aircraft would intercept and track the E/T equi-signal of a director-beam ("Leitstrahl") to the target. A second beacon would transmit three E/T beams that would cross the director-beam at certain distances just before reaching the target. Upon reaching the first cross-beam, the aircraft had to well established on the equi-signal course-line. Reaching the centerline of the second and third cross-beam was used to determine when to release the bombs. This was done with a special stopwatch, the "X-Clock" ("X-Uhr"), see Figure 45B. This mechanical calculator computed the "bomb release" time, based on actual groundspeed towards the target (derived from the times between the cross-beams), release altitude, and type of bomb. In a simplified version, only a single cross-beam was used. Ref. 85C.

The (lead) aircraft required an "X-Apparatus" ("X-Gerät") installation. This comprised (see p. 106 in ref. 2):

  • two dedicated receivers with associated rod antennas,
  • two AFN2 ("Anzeigegerät Flug-Navigation") course-deviation indicators (right-hand instrument in Figure 45A).
  • The vertical down-pointing needle indicates left/right deviation from the course line. The needle pulses to the left or right, in the rythm of the dominating "E" or "T" signals ("Zuckanzeige", "kicking meter"). When receiving the beacon and the position is "on course", the needle is centered.
  • The horizontal needle (pointing at the vertical scale on the left) is a signal-strength indicator, and acts as a simplistic near / far indication of distance to the beacon.
  • The indicator lamp in the center is illuminated when receiving a marker beacon during approach to landing. It is a line-replacable neon lamp. On the AFN1, it is located at the top.
  • an AVP unit ("Anzeige-Verstärker Plendl", "Plendl-method Indicator Amplifier") for each AFN2.
  • a power converter unit and a power-distribution unit,
  • an "X-Uhr" multi-stopwatch bomb-release timer (Figure 45B).

AFN1 AFN2

Fig. 45A: Anzeigegerät für Funk-Navigation (Radio-Navigation Indicator) - model AFN1 and AFN2



X-Uhr

Figure 45B: X-Uhr "Bombenabwurfautomat" (automatic bomb-release timer/computer)

(source left image: ref. 230A; clock face is marked "H&B" for manufacturer "Hartmann & Braun"; right image: item in Horst Beck Collection)

In the black & white photo above, the needles are at the position just prior to bomb release. Note that the X-Uhr on the right has a third small scale marked "0 - 4 hours", indicating to what extent the clock spring has been wound.

Proof-of-concept was done with "Lorenz Beam" systems. However, these commercial systems had neither the required range, nor the required accurate and narrow equi-beam (±0.1º aperture). Therefore, the operating frequency was increased from 30 - 36.2 MHz to the 66 - 77 MHz range, and the beacon was equipped with more powerful transmitters. The German code name for the "X"-station ("X-Station", "X-Bodenstelle", "X-Peiler", "X-Bake") was "Wotan I". The basic antenna system comprised two vertical dipoles. The antenna system as such was rotable to the desired beam direction, but not (continuously) rotating. One dipole was energized continuously with an AM carrier that was modulated with a 2000 Hz tone. The second dipole was placed at a distance of 3½ λ, and was energized via a motorized capacitive phase-shifter. The phase was changed stepwise, every 0.5 sec. The resulting radiation pattern had 14 or 18 E/T-beams of about equal strength, and an equi-signal zone with a width of less than ±0.1º. The large number of major lobes was very awkward: the aircraft had to fly across the lobes, and count the passages of the "T" zones to find the intended guide beam ("Marschleitstrahl", the 7th of 14 (as in Figure 44 below), or the 9th of 18).

Wotan I beacon pattern

Fig. 46: Radiation pattern of the Wotan I beacon

(source: adapted from ref. 2)

The complexity of the method required extensive pilot training. Only a rather limited number of aircraft was equipped with the X-Gerät. To cope with jamming by the British, the system was modified to use additional frequency channels, and a tone modulation well above the standard audio bandwidth of regular receivers. This provided some temporary relief from the jamming. The "Battle of the Beams" between Germany and Britain took place from late-1939 through mid 1941. Ref. 6D, 28, 38, 230C, 230D, 230E, 230F, 234. During this period, the British developed countermeasures to German radio-navigation systems and to radio-telephony communication of fighter/bomber control systems, to which the Germans responded with modifying those systems and introducing new systems.

By May of 1941, the Lorenz X-System was abandoned in favor of the "Y-System", see further below. A secondary reason for abandoning the X-system was the absence of a system for formation flying "in the clouds". This limitation had been recognized, and implied that a simpler system with crossing beams would be just as effective.

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

By the end of 1939, three Knickebein installations were operational along the western border of Germany: station Knickebein-2 (K2) at Stollberg/Bredstedt on the North Sea coast in the far north (later the location of Bernhard station Be-9), K4 at Kleve ( where the Rhine river crosses into the Netherlands; spelled Cleve until July of 1935; this is the German town that is closest to London and the Midlands), and K12 at Lörrach/Maulburg (in the far southwest of Germany, near the German/Swiss/French border). However, the latter was the  small ¼-size version (see Fig. 48). The K2 and K4 installations had an enormous rectangular antenna system, see Figure 47. Their truss frame measured ca. 90 x 30 m (WxH, ≈300 x 100 ft). Suspended in the frame were two dipole arrays, one for the "E" beam and one for the "T" beam. Each of these sub-arrays comprised 8 vertical wire-dipoles. Each wire-dipole had a dipole-reflector behind it. The system could be rotated on a circular track, to point the beam at the target (in Britain). To obtain a narrow equi-beam (≈0.3º), the "E" and "T" beams were offset 7.5 degrees to the left and to the right of the desired equi-beam. This was done by angling the left and right hand half of the antenna system by 15 degrees from each other. Looking at the antenna system from above, it had a slight V-shape ("crooked leg", "dog leg") of 180 - 15 = 165 degrees.

Knickebein large

Fig. 47: Large Knickebein under construction (K2 at Bredstedt; replaced by Bernhard Be-9 in 1944)

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


Knickebein pattern

Fig. 47A: Radiation pattern of the Knickebein beacon

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

There are several Knickebein-beam radiation pattern diagrams floating around in literature, without reference to the ultimate source. As always: trust, but verify! This is why I decided to create a model of the large Knickebein dipole/reflector array myself. I always use the fabulous 4NEC2 antenna modeling freeware tool. The complete antenna system comprises two independent identical arrays side-by-side (one for the dash-beam, one for the dot-beam), but only one beam transmits at a time. So, I only modeled one beam. The NEC-file of my model, which is not optimized, is here. The results are shown above and below. Note that, as is standard for radiation pattern diagrams, a logarithmic scale (decibel, dB) is used for the signal-strength (see far left side of the two figures below).

Knickebein pattern

Fig. 47B: Top, oblique, and side view of the radiation pattern of a Knickebein sub-beam ("E" or "T") - in free space


The top views above are actually quite similar to the generic patterns shown in literature. However, they are only valid for an antenna in so-called "free space". I.e., without any objects anywhere near, or ground below, the antenna. This is unrealistic, in particular for an antenna system close to the ground (in terms of the number of wavelengths λ of the transmitted signals), as is the case with Knickebein (with λ ≈ 10 m). The figure below shows the impact of ground reflections (assuming conductivity and dielectric constant of standard "real ground"), clearly beyond the modeling capabilities of the era. My model does not include the steel trusses around the Knickebein arrays, which could cause some pattern distortions. In practice, this was "not disturbing" (pdf p. 4 in ref. RBD14A).

Knickebein pattern

Fig. 47C: Top, oblique, and side view of the radiation pattern of a Knickebein sub-beam ("E" or "T") - over ground


After the invasion of their neighbor countries, the Germans installed another nine Knickebein stations along the coasts of southern Norway (1x), The Netherlands (2x), and France (6x, from the Channel coast down to Brittany). Construction of station K13 on the isle of Sicily/Italy was never completed. Like K12 in Germany, all of these stations had a smaller antenna system: half the size of the Large Knickebein. The Small Knickebein had a width 45 m, a track diameter of 31 m, and had 2x4 dipoles plus reflectors per beam, instead of 2x8. I.e., one quarter the size of the Large Knickebein. Hence, the width of the equi-beam was larger (≈0.6º) and the side-lobes were stronger. These small stations were installed closer to their targets than the large K2 and K4 stations in Germany. So, over the target, the width of the equi-beam was still acceptable.

Knickebein klein

Fig. 48: Small Knickebein station (left: under construction in France)

(sources: Bundesarchiv Bild 101I-228-0322-04/Friedrich Springorum/CC-BY-SA 3.0 (left) and Fig. 37 in ref. 181 )

The dipoles and radiators of the Small Knickebein were made of thick metal tubes instead of wires. This makes the antenna more broadband ( = usable over a wider frequency range, without "tuning"). The left-hand photo above clearly shows that the reflectors are also driven dipoles (see the split between the two dipole halves). So, they are "active", i.e., powered by the transmitter. Active reflectors are more effective for side-lobe reduction than passive/parasitic reflector dipoles or rods (see p. 71 in ref. 137).

In September of 1941, the aircraft receivers were upgraded from FuBl 1 to FuBl 2, which supported a large increase in the number of available frequency channels in the same band, and a range of 600 km at 6000m altitude (20 thousand feet). During the winter of 1940/41, the Knickebein system became increasingly unreliable and unusable over Britain, due to jamming by the British. Reported effective, undetected "spoofing" and "beam bending" is doubtful at best. The jamming tone pulses sounded differently from the true Knickebein pulses (§28  in ref. 187), possibly due to more keyclick suppression. The system continued to be used in the lead aircraft ("Pfadfinder") for navigation towards the target, but those now relied on the X-System (described further below) to locate and mark the actual target.

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

Simulated sound of crossing a "Knickebein" E/T beam back & forth

(source:)

After the invasion of their neighbor countries, the Germans installed another nine Knickebein stations along the coasts of Norway (1x), The Netherlands (2x), and France (6x, from the Channel coast down to Brittany). Construction of an additional station in Italy was never completed. However, these nine stations had a smaller antenna system: about 1/2 the size of the Large Knickebein. The Small Knickebein had a width 45 m, a track diameter of 31 m, and had 2x4 dipoles plus reflectors per beam, instead of 2x8. Hence, the width of the equi-beam was larger (≈0.6º) and the side-lobes were stronger. On the other hand, they were installed closer to the targets in Britain than the large stations in Germany. In September of 1941, the aircraft receivers were upgraded from FuBl 1 to FuBl 2, which supported a large increase in the number of available frequency channels in the same band, and a range of 600 km at 6000m altitude (20 thousand feet). During the winter of 1940/41, the Knickebein system became increasingly unreliable and unusable over Britain, due to jamming by the British. Reported "spoofing" and "beam bending" is pure propaganda (or ignorance). The system continued to be used in the lead aircraft ("Pfadfinder") for navigation towards the target, but those now relied on the X-System (described further below) to locate and mark the actual target.

Already in 1939, an other successor to the "X-System" was conceived. It retained the director-beam ("Marschleitstrahl") concept of the "X-System". But rather than using a cross-beam to mark the position of the target along that beam, it used a transponder system that allowed the ground controller to determine the aircraft's distance from the beacon (of course "slant range", not distance over ground). After a fixed delay time, the transponder in the aircraft would retransmit the received signal at a different frequency (1.9 MHz lower). The ground station would derive the range from the total round-trip signal delay, minus the fixed delay. The ground controllers would command release of the bombs, based on the range. This was called the "Y-System" ("Y-Verfahren", ref. 244D), US/UK Allied code name "Benito". It became operational in September of 1940. As the procedure involved a ground controller, the number of aircraft that could use the system simultaneously, was limited.

The (lead) aircraft required a "Y-Appraratus" ("Y-Gerät") installation (ref. 2, 6E). This comprised:

  • one dedicated beacon receiver: the "UKW Leitstrahlempfangsgerät" FuG28a. It combined a FuG17 radio-telephony transceiver (42.15 - 47.75 MHz, 10 Watt) and an AG28 "Auswertegerät" - an electro-mechanical equivalent of the X-system's AVP unit,
  • an LKZG ("Leitstrahl-Kurststeuerungs-Zwischengerät") to interface the FuG28a to the lateral-axis auto-pilot ("Kursregler"), for automatically tracking an equi-beam,
  • one AFN2 ("Anzeigegerät Flug-Navigation") course-deviation indicator (Fig. 45A),
  • one FuG16ZE or FuG16ZY transponder (38.5-42.3 MHz and 38.4 - 42.4 MHz, respectively; ref. 40, 41),
  • associated power converter units,
  • various control panels.

FuG28a

Fig. 50: Front & bottom of the FuG28a "UKW Leitstrahlempfangsgerät" (VHF guide-beam receiver)


The "Y-Station" ground station ("Y-Bodenstelle", "Y-Peiler", "Y-Bake") was called "Wotan II" (FuSAn 733). A variety of antenna configurations and beam transmitters was used (Bertha I, Bertha II), and a number of co-located transponder transmitters (S16B, Sadir 80/100).

An interesting beacon system is the Hermes/Hermine "Sprechdrehbake" system ("Talking Beacon"). The system was originally developed in response to a tactical requirement formulated during the second part of 1942, as a navigational aid for the purpose of giving an approximate bearing to single-engine night fighters engaged in "Wilde Sau" [lit. "Wild Boar"] air-defence operations. The pilot could determine the bearing from the beacon, without having to look at an instrument. The beacon stations (FuSAn 726) transmitted real-time voice-announcements of the beam azimuth, every 10º. I.e., the numbers 1 - 35 (multiples of 10º), and the "station call-sign" at 360º = 0º = north. Each digit was pronounced separately: e.g., "12" = "1-2", not "twelve". The voice stream was pre-recorded as an optical track on a film strip ("Tonfilm"). The voice signal was transmitted with an omni-directional antenna. At the same time, and on the same frequency, a strong constant audible 1150 Hz tone was transmitted. However, it was transmitted with a rotating cardioid antenna pattern. The null of this pattern ( = no 1150 Hz interference signal) coincided with the direction as announced by the voice announcement at that very moment. So, the voice could only be heard (briefly) in that momentary direction. Due to the width of the null (effectively about 15° (ref. 8), equivalent to (360°/15°)x60=2.5 sec), the immediately preceding and following announcement was only partially audible, at much reduced volume. The airborne counterpart, FuG125 "Hermine-Bord", comprised the standard EBl 3 receiver, its FBG2 control panel, and a small audio-amplifier (model V3a or ZV3). The system was developed in 1943/44 by Ernst Kramar et al of the Lorenz company. Ref. 247 (pp. 13-15).

Hermine

Fig. 51: Principle of the "Hermes/Hermine" talking beacon system

(source photo: deutschesatlantikwallarchiv.de)


Hermes sound - audio file still to be created...

Simulated sound of a "Hermine" beacon (60 sec rotation)

(source: ? © ? used with permission)

With a single "bernhard", "Hermine", etc. beacon, only relative bearing to/from that particular station can be determined. I.e., not a position ( = direction + distance (range) to the station), but only a line of direction. This is called a linear "Line of Position" (LoP, "Standlinie"). Position determination can be done by combining the bearing from at least two beacons with known location. This is called "multilateration". The simplest form is with two beacons: triangulation ("Kreuzpeilung"). Note that the bearing from a ground station to the aircraft (or vice versa) should not be confused with the aircraft's heading (the way the nose is pointing), nor with the aircraft's course (ground track).

hyperbolic system

Fig. YY: The hyperbolic radio navigation system for aviation

(source: National Air & Space Museum, Smithsonian Institution, "Time & Navigation - Navigating in the Air", 2012, artist: Bruce Morser)



Loran sound

Sound clip of Loran/Loran-A pulses (33 sec)

(source: A. Cordwell, retrieved February 2020)



Consol sound

Sound clip of a Sonne/Consol sequence (42 sec)

(source: de.wikipedia.org, retrieved March 2020)

Consol sound

An other sound clip of a Sonne/Consol sequence (3 min)

(source: www.geocaching.com, retrieved March 2020)



An EM wave is called "vertically polarized", if the E (= electrical) field is vertically polarized. The H (magnetic) field is always perpendicular to the E field.

EM wave E & H field EM E-field dipole

Fig. XX: Linearly polarized EM wave (left) and E-field of such a wave inducing current in an aligned dipole antenna

(image source: (left) wikimedia.org CC license; (right) wikimedia.org, CC license)


RADAR. Out of scope. But....

Finally, after years of shameful denial, the world-renowned IEEE finally redeemed itself in 2019, by formally recognizing that, contrary to popular belief, perpetuated Allied WW2 propaganda and general ignorance, radar was not only invented and patented in 1904 in Germany by Christian Hülsmeyer (patents 165546, 13170, 25608), but also he also publicly demonstrated his "telemobiloscope" in Cologne/Germany (Köln), and in Rotterdam/The Netherlands that same year. Ref. 261A, 261B.

In addition to the beacon systems described above, there was a number of other German beacon systems (ref. 1, 2, 8, 26B, 33, 230A-230C, pp. 7-19 in ref. 247), such as:

  • Baldur, VHF system. Airborne set: FuGe 126 and FuGe 126k. Further developments (never operational): Baldur-Truhe (combination of Baldur and Truhe), Baldur-Bernhardine (combination of Baldur and Bernhard, for simultaneously obtaining bearing and range; with a "Bernhardine" Hellschreiber printer for bearing & range indication).
  • Elektra: long wave beam system (initially ca. 480 kHz, later 270-330 kHz), range over land 800-1200 km (500 and 300 kHz respectively), range over sea 1700-200 km (500 and 300 kHz respectively). Three antennas per beacon station. Transmitter power: 1.5 kW. Ref. 230A, 230B.
  • Elektra kurz (480 kHz, λ = 625 m; 1939-1941), Elektra lang (300 kHz, λ = 1000 m). Ref. 230K.
  • Dreh-Elektra.
  • Elektra-Sonne: beacon could be operated alternately as "Elektra" and "Sonne", to combine advantages of both. Range was intended to be increased by raising transmitter power to 60 kW. Three stations were built during 1944-1945 but were never operational. Ref. 230A.
  • Mond ["Moon"]: experimental system, intended to improve range and accuracy of "Sonne", while operating on higher frequencies (3 MHz, 6 MHz; 30-30 MHz per ref. 230A), at night.
  • Sonne ["Sun"]: long wave (several LF frequencies between 270 and 330 kHz), long-range system of the Kriegsmarine. It was based on "Elektra", but rather than physically rotating a loop antenna, Sonne used three stationary antennas spaced about 1 km (about 3.86 wavelengths) and a single transmitter, to electronically sweep the direction of the beams. Range over land 1200 km. Range over sea 2000 km. Transmitter power: 1.5 kW. Ref. 230A-230C, 230M.
  • Goldsonne.
  • Goldwever: a "Sonne" derivative that never became operational.
  • Stern ["Star"]: an experimental Sonne derivative, operating at VHF frequencies, hence range basically limited to line of sight. Not developed to completion.
  • Erich: VHF system.
  • Erika: a hyperbolic beacon system [TBC], comprising a line of six antenna arrays (spaced ca. 46, 18, 27, 27, and 124 m) each with a transmitter. Similar to the British Gee system. Developed in1942, briefly operational, replaced by Bernhard. Ref. 8.
  • Dora: ca. 1940, shortwave, 2 pairs of vertical dipoles in crossed configuration, with a vertical antenna at the center, rotating dual cardioid pattern; not satisfactory. 1.5 kW beacon, used for calibrating Erika.
  • Komet (FuSAn 712) / Komet-Bord (FuG 124), with concentric rings of antennas for multiple operational HF frequencies (short wave); it proved impossible to adjust/calibrate. Development and evaluation was done from 1941 through the end of the war. Large HF ground station with an antenna array with 127 masts and 19 control huts, with "Kometschreiber" bearing recorder/indicator in the aircraft (FuG124). Ref. 8. Experimental stage only (Bordeaux/France, Kølby/Denmark).
  • Drehbake "M", UHF system.
  • Truhe, VHF hyperbolic pulse system, compatible with the British "Gee" system (where "Gee" stands for the letter "G" in "Grid"), which was referred to a "Hyperbel" by the Germans. Airborne sets: FuGe 122 (46-50 MHz), and FuGe 123 (25-75 MHz).
  • Zyklop, 120 watt transportable beacon station, derived from Knickebein, operated on Kickebein frequencies. A more-mobile version was Bock-Zyklop, working on FuG16 frequencies. Ref. 8.

"I don't trust those high-frequency thingies. One time I flew to southern Germany and landed inadvertently in northern Germany - all because of your high-frequency thingies!"

A. Hitler

"Radio-navigation requires boxes with coils, and I hate boxes with coils!"

H. Göring

Source: p. 53, 157 in ref. 5 (German edition).

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).

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 Transmitter arrangement for producing course lines
662457 RP 1935 W. Runge
K. Röhrich
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
767523 RP 1938 A. Lohmann
A. Bittighofer
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
767529 RP 1938 A. Lohmann
A. Bittighofer
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


Below is a listing of patents related to radio direction finding, radio location, radio navigation (generally covering the early 1900s through WW2).

Patent number Patent office Year Inventor(s) Patent owner(s) Title (original, non-English) Title (original English or translated)
716134 US 1901 John Stone Stone John Stone Stone --- Method of Determining the Direction of Space Telegraph Signals
716135 US 1901 John Stone Stone John Stone Stone --- Apparatus for Determining the Direction of Space Telegraph Signals
770668 US 1903 Alessandro Artom Alessandro Artom --- Wireless Telegraphy of Transmission through Space
165546 KP 1904 Christian Hülsmeyer Christian Hülsmeyer Verfahren, um entfernte metallische Gegenstände mittels elektrischer Wellen einem Beobachter zu melden Method for detecting distant metal objects by means of electrical waves [this is the invention of radar!]
771819 US 1904 L. de Forest L. de Forest --- Wireless Signalling Apparatus
13170 GB 1904 Christian Hülsmeyer Christian Hülsmeyer --- Hertzian-wave Projecting and Receiving Apparatus Adapted to Indicate or Give Warning on the Presence of a Metallic Body, such as a Ship or a train, in the Line of Projection of such Waves
25608 GB 1904 Christian Hülsmeyer Christian Hülsmeyer --- Improvement in Hertzian-wave Projecting and Receiving Apparatus for Locating the Position of Distant metal Objects
192524 KP 1907 Otto Scheller Otto Scheller Sender für gerichtete Strahlentelegraphie Transmitter for directional beams
201496 KP 1907 Otto Scheller Otto Scheller Drahtloser Kursweiser und telegraph Wireless course indicator and telegraph.
[English translation is here]
378186 F 1907 Alessandro Artom Alessandro Artom Système évitant la rotation des antennes dans un poste de télégraphie sans fil dirigable et permettant en particulier de déterminer la direction d'un poste transmetteur System to avoid rotation of the antennas of a directional radio station and in particular enabling determination of the direction of a transmitter station; identical to original Italian patent nr. original Italian patent 11 april 1907 nr. 88766; invention of the goniometer]
943960 US 1909 Ettore Bellini & Alessandro Tosi Ettore Bellini & Alessandro Tosi --- System of Directed Wireless Telegraphy
1135604 US 1912 Alexander Meissner Alexander Meissner --- Process and Apparatus for Determining the Positon of Radiotelegraphic receivers [invention of Radio Compass]
299753 RP 1916 Otto Scheller C. Lorenz A.G. Drahtloser Kursweiser und Telegraph Wireless direction pointer and telegraph [invention of overlapping beams with equi-signal, radio goniometer to couple transmitter to antenna pair]
[English translation of the patent claims is here]
130490 GB 1918 Frank Adcock Frank Adcock --- Improvement in Means for Determining the Direction of a Distant Source of Elector-Magnetic Radiation [adds suppression of received horizontally polarized signals in each antenna pair]
252263 GB 1924 Alexander Watson Watt Alexander Watson Watt --- Improvements in and relating to Radio-telegraphy Direction Finding and other purposes [adds CRT display to Adcock DF antennas]
1741282 US 1927 Henri Busignies Henri Busignies --- Radio Direction Finder, Hertian Compass, and the Like
632304 F 1927 Alexandre Koulikoff & Constantin Chilkowsky Alexandre Koulikoff & Constantin Chilkowsky Procédé et dispositifs pour le mesure des distances au moyen d'ondes electro-magnétiques Method and apparatus for the measurement of distances by the use of electromagnetic waves [identical to British patent nr. 288233; invention of the transponder]
305250 GB 1927 Alexander Watson Watt & Labouchere Hillyer Bainbridge-Bell Alexander Watson Watt & Labouchere Hillyer Bainbridge-Bell --- Improvements in and relating to Apparatus adapted for use in Radio-telegraphic Direction Finding and for similar purposes. [expansion of GB patent 252263; adds omnidirectional / non-directional sense antenna]
502562 RP 1929 Ernst Kramar & Felix Gerth C.Lorenz A.G. Verfahren zum Tasten von Richtsendern für rotierende Richtstrahlen Method for keying directional transmitters for rotating directional beams
546000 RP 1930 Meint Harms Meint Harms Verfahren einer selbsttätigen Ortsbestimmung beweglicher Empfänger Method for position finding by a mobile receiver [phase difference of coherent/synchronized waves; invention of hyperbolic navigation]
661431 RP 1930 Ernst Kramar C. Lorenz A.G. Einrichtung zur Richtungsbestimmung drahtloser Sender Arrangement for direction finding of wireless transmitters
1945952 US 1930 Alexander McLean Nicolson Alexander McLean Nicolson --- Radio Range Finder
1949256 US 1931 Ernst Kramar C. Lorenz A.G. --- Radio Direction Finder
577350 RP 1932 Ernst Kramar C. Lorenz A.G. Sendeanordnung zur Erzielung von Kurslinien Arrangement for creation of course lines
592185 RP 1932 Ernst Kramar & Felix Gerth C. Lorenz A.G. Gleitwegbake zür Führung von Flugzeugen bei der Landung Glideslope beacon for guiding airplanes to landing
405727 BP 1932 --- C. Lorenz A.G. --- Directional radio transmitting arrangements particularly for use with ultra-short waves [use of marker beacons]
408321 BP 1932 --- C. Lorenz A.G. --- Radio beacon for directing aircraft [2 overlapping VHF beams for lateral guidance, curved glidepath on constant signal strength of same 2 beams]
607237 RP 1933 --- C. Lorenz A.G. Leitverfahren für Flugzeuge mittels kurzen Wellen, insbesondere ultrakurzer Wellen Method for guiding aircraft by means of short waves, in particular ultra-short waves [expansion of Reichspatent 589149]
1981884 US 1933 Albert H. Taylor, Leo C. Young, Lawrence A. Hyland Albert H. Taylor, Leo C. Young, Lawrence A. Hyland --- System for detecting objects by radio [Invention of Doppler-shift based radio detection of moving reflective object]
2072267 US 1933 Ernst Kramar C. Lorenz A.G. --- System for Landing Aircraft
616026 RP 1934 --- C. Lorenz A.G. Sendeanordnung zur Erzielung von Kurslinien gemäß Patent 577 350 Transmitter arrangement for obtaining course-lines per Reichspatent 577350 [vertical dipole and resonant reflectors]
612825 RP 1934 --- C. Lorenz A.G. Verfahren zum Betrieb von Funkbaken Method for operating a radio beacon [2-course AN or ET beam, left/right beams swapped based on which course is active]
2196674 US 1934 Ernst Kramar & Walter Max Hahnemann C. Lorenz A.G. --- Method for Landing Aircraft
2217404 US 1934 Ernst Kramar & Walter Max Hahnemann C. Lorenz A.G. --- System and Method for Landing Airplanes
2025212 US 1934 Ernst Kramar C. Lorenz A.G. --- Radio Transmitting Arrangement for Determining Bearings
2083242 US 1935 Wilhelm Runge Wilhelm Runge --- Method of Direction Finding
2184843 US 1935 Ernst Kramar C. Lorenz A.G. --- Method and Means for determining Position by Radio Beacons
44879 F 1935 --- C. Lorenz A.G. Appareil transmetteur pour les ondes électriques et en particulier pour les ondes ultra-courtes Transmitter for electrical waves, in particular ultra-short [curved glidepath based on constant beam signal-strength]
2134535 US 1936 Wilhelm Runge Telefunken GmbH --- Distance Determining System [signal-strength based]
2117848 US 1936 Ernst Kramar C.Lorenz A.G. --- Direction Finding Method
2170659 US 1936 Ernst Kramar C.Lorenz A.G. --- Direction Finding Arrangement
2141247 US 1936 Ernst Kramar & Heinrich Brunswig C.Lorenz A.G. --- Arrangement for Wireless Signaling
734130 RP 1937 Ernst Kramar & Walter-Max Hahnemann C.Lorenz A.G. Ultrakurzwellen-Sendeanordnung zur Erzielung von Gleitwegflächen Arrangement of VHF transmission for generation of glide path planes
705234 RP 1937 Ernst Kramar & Dietrich Erben C.Lorenz A.G. Sendeanordnung zur Erzeugung von geknickten Kurslinien Arrangement for generating angled course lines
720890 RP 1937 Ernst Kramar & Werner Gerbes C.Lorenz A.G. Anordnung zur Erzeugung einer geradlinigen Gleitwegführung für Flugzeuglandezwecke Arrangement for generating straight glide path guidance for aircraft landing purposes
2226718 US 1937 Ernst Kramar & Walter Max Hahnemann C.Lorenz A.G. --- Method of Landing Airplanes
731237 RP 1938 Ernst Kramar C.Lorenz A.G. Empfangsverfahren für Leitstrahlsender Method of reception of guide beam transmitters
2282030 US 1938 Henri Busignies Henri Busignies --- System of Guiding Vehicles
711673 RP 1938 Ernst Kramar C.Lorenz A.G. Gleitweglandeverfahren Glide Path Landing Method
2290974 US 1938 Ernst Kramar C.Lorenz A.G. --- Direction Finding System
2297228 US 1938 Ernst Kramar C.Lorenz A.G. --- Glide Path Producing Means
2288196 US 1938 Ernst Kramar C.Lorenz A.G. --- Radio Beacon System
7105791 RP 1938 Ernst Kramar & Heinrich Nass C.Lorenz A.G. Sendeanordnung zur Erzeugung von Leitlinien Arrangement for producing course guide-beams
2241907 US 1938 Ernst Kramar & Walter Max Hahnemann C.Lorenz A.G. --- Landing Method and System for Aircraft
2238270 US 1939 Ernst Kramar & Heinrich Nass C.Lorenz A.G. --- Radio Direction Finding System
2210664 US 1939 Ernst Kramar & Walter Max Hahnemann C.Lorenz A.G. --- Radio Direction Finding System
2255741 US 1939 Ernst Kramar C.Lorenz A.G. --- System for determining Navigatory Direction
718022 RP 1939 Ernst Kramar C.Lorenz A.G. Antennenanordnung zur Erzeugung einer Strahlung für die Durchführung von Flugzeugblinlandungen Antenna configuration for generating a beam for blind landing of airplanes
2241915 US 1939 Ernst Kramar C.Lorenz A.G. --- Direction-Finding System
581603 GB 1942 Robert James Dippy Robert James Dippy --- Improvements in or relating to Wireles Systems for navigation [invention of the Grid / GEE/ G hyperbolic system; co-patent 581602 "Improvements in or relating to Wireles Signalling Systems" covers GEE pulse-signals receiver & CRT display system design]
862787 DP 1944 Joachim Goldmann C.Lorenz A.G. Antennenanordnung zur Erzeugung von ebenen Strahlungsflächen der Strahlung Null Antenna configuration for generating narrow nulls in beam radiation pattern ["Elektra" beam system]

Table 3: Selected patents regarding radio direction finding, radio location, radio navigation through WW2



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...


REFERENCES


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

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