• On page 1:
• [Introduction]
• [Concrete ring & circular rail track]
• [Electrical & signal distribution]
• [Antenna system]
• [Transmitter modulation & spectrum]
• [FuSAn724 transmitters]
• [FuSAn725 transmitters]
• [Optical encoder disk]
• [Patents]
• [Unknown/unclear aspects]
• [References]

• On this page:
• [Command uplink]
• [Monitoring antenna mast & receiver]
• [Rotational speed]
• [Cabin]
• [Corner-blocks]
• [Locomotive system]
• [Central-support building]
• [Electrical power]
• [Unknown/unclear aspects]
• [References]

By August of 2019, this page had grown to about 175 photos and diagrams. It had become rather large (ca. 20 MB download size). This caused long download times for some users. I decided to split the page into two separate pages. This split should be fairly transparent to you. Please continue using the (unchanged) items lists above and update your bookmarks - if necessary.

• ["Bernhard/Bernhardine" Luftwaffe radio-navigation system]
• [FuG120 "Bernhardine" airborne Hellschreiber printer system]
• ["Bernhard" station locations]
• [Radio direction finding, location, and air navigation through WW2]

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

Latest page update: May 2022 (updated & expanded the motor drive section, the power section, expanded the remote receiver section)

Previous updates: 10 March 2022 (added ref. 282C, 282D), 6 December 2021 (expanded the command uplink section); 20 June 2021 (added ref. 175B and text); 17-Sept-2020 (added ref. 163S). 6 Aug 2020 (added & used ref. 179 (command uplink)); May 2020 (added ref. 235 and text); October-November 2019 (added ref. 253, 244A-K, added high-res version of ref.15); August 2019 (split into two pages, added ref. 243).

COMMAND UPLINK FEATURE

The "Bernhard/Bernhardine" system is simply a "UKW-Richtstrahl-Drehfunkfeuer und Empfangszusatz mit geschriebener Kommandoübertragung". That is, a rotating VHF directional beacon system, with printed command-uplink capability. The latter capability was demonstrated mid-1944 (§4 in ref. 179). This led the General der Jagdflieger (GdJ, Adolf Galland at that time) to recognize the usefulness of the entire system, and demand its introduction on all night-fighter aircraft late July 1944. Note: GdJ (formerly Inspekteur der Jagdflieger) was not a rank, but a leading position without operational command within the Oberkommando der Luftwaffe (OKL, High Command of the Air Force).

Obviously, the primary purpose of a beacon is to be a navigational aid. With a single beacon, only the relative bearing ( = direction) to/from that particular station can be determined (unless the beacon somehow allows the slant range ( = distance) between beacon and aircraft to be determined). I.e., only a position line ("Standlinie") from the beacon (with known location) can be determined, and neither distance from the station, nor a position point. Position determination is done by combining the bearing from at least two beacons with known location. I.e., by means of conventional triangulation ("Kreuzpeilung").

Fig. 86: Determining bearing angle with a single beacon, and position via triangulation with two beacons

(the bearing angle is measured clockwise from North)

The "Bernhard" beacons were used by fighter aircraft that were engaged in intercepting inbound enemy aircraft, primarily bombers. It was the task of regional fighter control stations ("Jägerleitstellungen", "Jägerleitstände") to guide fighter aircraft to their target. The required guidance, instructions, and information was continuously provided via HF and VHF voice radio (radio telephony, R/T). A standardized short message format was used for the broadcast stream of the so-called "Running Commentary" ("Laufende Reportage"). This was used in German fighter control systems such as "Zahme Sau" ("Tame Boar") and "Wilde Sau" ("Wild Boar"). See ref. 6B, §22-25 in ref. 6C, ref. 282A-282D. In particular, later during WW2, with increasingly frequent Allied bombing raids on Germany, the fighter control voice frequencies became saturated. On top of that, the voice frequencies were also subject to Allied jamming, as were wired-broadcast of radio signals and attacks on the wired telephone network (p. 7, 8 in ref. 282B). As a backup, the same short messages could be broadcast in spoken form via certain radio navigation beacons, and also via some Morse beacons (§59 in ref. 6B).

The 1938 Telefunken patent 767512 already addressed using the "Bernhard" beacons to broadcast the relative direction for intercepting enemy aircraft. It proposes to transmit an extra heavy tick-mark in the compass scale, see Figure 86B. This could be used to indicate a target azimuth (the radial from the ground station) that is to be intercepted. The patent suggests implementation with a fixed notch (cam) on the edge of the encoder disk, and a contact that is adjustable to the desired target azimuth (Fig. 86A). The notch would actuate a switch that was simply connected in parallel with the output of the photocell of the optical disk. However, this target-azimuth marker method would not have been very practical: it could only be received by aircraft that are already flying on nearly the same bearing from the beacon station as that target. Also, the command/guidance would be limited to conveying a target azimuth.

Fig. 87A: Notched optical disk (source: Figure 2 in patent 767512)

Fig. 87B: Target azimuth bar superimposed on azimuth data (source: Figure 3 in patent 767512)

However, the "Bernhard" beacon already broadcasts information in textual form: the fixed numbers of the compass scale and the station identification letter. Why not use the same Hellschreiber system for transmitting short, programmable text messages? Excellent idea! But the beacon rotates, and the beam is only received during about 3⁺ to 5 sec out of every 30 sec rotation (depending on distance from the beacon). At 12°/sec rotation, about a 40-60 degree section of the compass scale is printed each time. Clearly, it must be guaranteed that the complete message is printed during a single beam passage, independent of the bearing from the station on which the aircraft is flying within the operating range of the system. This limits the number of text characters that can be put into a single message.

Let's assume that transmission of the message is continuously repeated as the beacon rotates. To always guarantee that a complete message is received, not one, but two back-to-back copies of the message must fit within a single beam passage! If not, the end of one message is printed, immediately followed by the beginning of the next copy of the same message. This by itself is bad enough, but it is also not possible to determine if all characters of the message have been received. This factor of two further limits the number of text characters that can be put into a single message...

Figures 76B and 76C above show that a traditional Hellschreiber font with five pixel-columns per character is used for the compass scale. Also as standard for Hellschreiber fonts, each character has a leading and a trailing pixel-column that is blank. This is for character spacing. The compass scale has three pixel-columns per degree. Each character spans 5 + 2 = 7 pixel-columns. Hence, at least about 20 characters can be received per beam passage (also per item 9 on p. 10 ( = Blatt 11) of ref. 198A). Therefore, the length of one complete message is limited to about 20 / 2 = 10 characters. To mark the beginning of each message, a delimiter symbol must be used. The start-delimiter of the next message-copy automatically marks the end of the preceding one, which allows confirmation that a complete message has been received. This leaves up to 9 characters of actual fighter guidance information. There were two types of command message (§57-64 in ref. 6B, §23-26 in ref. 6C, §17-28 in ref. 6M, p. 2 & 3 in ref. 244V):

• "Feindreportage", or "Reportage" for short, which is a so-called running commentary on enemy aircraft (typ. bombers).
• Specific instructions to either all units, or to only a specific unit, of the fighter division ("Jagddivision") to which the radio frequency was allocated. This could be orders at various levels: "Geschwaderbefehlswellen" (squadron level), "Gruppenbefehlswellen" (group level), "Divisionsführungswellen" (division level). Examples of such letters/numbers instructions were "C" to order "return to base", "B###" for "fly to airfield nr. ###", "AGZ###" for "Target ("Angriffsziel") of the enemy bombers is airfield nr. ###", and "MOS" for "Mosquito attack in progress".

Both types of messages had the same format as those that were transmitted via R/T telegraphy transmitters (VHF, shortwave, and longwave, with fighter-division specific frequency allocations), and W/T telephony transmitters. Ref. 282A, 282B, 282C. They were also broadcast via various navigation beacons (again, fighter-division specific). The latter included a small number of specially equipped Bernhard stations.

The following format of simple coded groups of letters and numbers was used for "Reportage" broadcast via Bernhard stations (p. 275 in ref. 5B):

• The "+" symbol as a message-start delimiter.
• Altitude (in 100s of meters) of the lead-aircraft of the enemy bomber formation.
• A two-digit identifier of the specific box of the "Jägergitter" (a.k.a. "Jägernetz") air defense grid, in which the enemy lead-aircraft is currently located (e.g., "QR" for the box around the city of Mainz).
• The two-digit course of the bomber group (in 10s of degrees).
• Size of the group (estimated number of aircraft).

Fig. 87C: grid-box "QR" near the city of Mainz

(source: ref. 244G)

Depending on the message content, 8-10 message characters were sent (including the delimiter). The following hand-drawn figure from 1945 illustrates the message "+40KA27100". Unfortunately, it not only (incorrectly) suggests that the station identifier was sent every 20° instead of every 10°, but also (incorrectly) suggests that the messages were sent in addition to the compass scale (ref. 5A even actually states so!). Note that these command messages were transmitted instead of the compass scale, as there was simply no third printer-track.

Fig. 88: Misleading British rendition of a "Bernhardine" print-out with Reportage/Command track at the bottom

(source: ref. 6C (1945), very similar image in ref. 5A)

Specific instruction messages (i.e., for pursuit and intercept, or other specific navigation guidance, not "reportage" situation messages) that were sent to Luftwaffe fighter units via a Bernhard-station; "00" at the beginning of such a Bermhard message signified that it was addressed to all units of the fighter-division that was using the beacon. Messages preceded by a single "FuG 25a Kennung" letter were addressed to a specific unit of that division (§III on p. 2 of ref. 244V). The FuG 25a was a Luftwaffe airborne IFF-transponder system, interrogated by Freya or Würzburg ground radar. A late version of the FuG 25a had some limited character uplink capability. Also see §17-28 in ref. 6M.

In the compass scale format, there is one tick-mark for every degree. These tick-marks are also used to synchronize the compass scale Hell-printer to the Hell-format transmission (as explained in the "Optical Encoder Disk" section). As the same printer channel is used for the command messages, it must now also be synchronized to the command message transmission. This requires tick-marks. Here, a tick-mark is implemented at the top of every single pixel-column, instead of every third column (p. 4 ( = Blatt 3) of ref. 198A). Retaining the tick-mark at the top of every third pixel-column could only have worked with a Hell-character font that is 6 pixel-columns wide (incl. blank columns for character spacing). With a tick-mark at the start of each pixel-column, there is no such limitation. Also, having more sync tick-marks than once per degree does not upset the sync mechanism: the synchronization electro-magnet of the compass scale printer-channel is activated by all black pixels, whether tick-mark or other part of the transmitted symbology.

The upper track of the "Bernhardine" printer is used to plot the signal-strength curve. The curve has a sharp V-shaped dip in the middle, which is used as a pointer for the compass scale that is normally printed below it. Clearly, the pointer-curve is not used in combination with the command messages. However, the signal-strength printer channel is not turned off, as it is linked to the automatic motor start/stop function.

The next figure illustrates what a real print-out with a command message would have looked like:

Fig. 89: re-created Bernhardine print-out with command-uplink message

As stated above, the command uplink messages were sent instead of the compass scale data from the optical encoder disk. So, somewhere, these messages were converted from a text-string input to a Hellschreiber pixel stream. This could have been done with a keyboard and tape-puncher, combined with a "punch tape to Hellschreiber pulse-sequence converter". This was the normal way with the "Presse Hellschreiber" system. The tape could be looped through the tape reader to repeat the message. Of course, speed and text font would have had to be adapted. However, p. 87 in ref. 2A and p. 392 in ref. 7B suggest that a different method was used to program the text character sequence: inserting jumpers ("Stöpsel") into a patch-board ("Stecktafel"). Mid-2015, I finally obtained confirmation of this, by the photo shown below (ref. 93A). It was taken inside the cabin below the rotating superstructure of the Bernhard installation Be-10 at Hundborg/Denmark. The photo shows two transmitter-modulators, two monitor Hellschreiber printers (for printing signals from a nearby remote monitoring receiver and antenna), and a patch-board with patch cords. There are 9 jacks for each of up to 9 selectable characters. With some difficulty, one can see that the left-hand column is labeled A-Z, and the right-hand column 1-9, 0, +, ... So, the conversion from text strings to Hellschreiber pixel streams was done at the Bernhard station, based on telephone or teleprinter messages from the regional fighter command & control center.

Fig. 90A: Lower left-hand corner - patch-board & patch-cords for selecting command-message text string

(source: Figure 30 in ref. 93A; photo taken at Be-10 Hundborg/Denmark)

The actual patch-board and patch-cords appear to be very similar to what was used during the 1930s in standard small German telephone switchboards:

Fig. 90B: Left "Klappenschrank" telephone swithboard model OB-14; right: 50-line Wehrmacht PBX

(source OB-14: Fernmeldemuseum Dresden; "OB" in "OB-14" stands for "Ortsbatterie", meaning local battery operation)

This patch-board method is similar to what was used in the mechanical Siemens-Hellschreiber-sender model 44 in the 1960s. This sender has a character-drum with 19 notched disks and associated slip-contacts: seven disks to generate the pixel sequence for the characters A - G, ten for the figures 0 - 9, and one notched disk for the character "-". This machine sent a string of eight characters, based on a discrete code at its inputs (representing status and self-test results from a telephone exchange system).

Fig. 91: The inside of a Siemens-Hell model 44E with a stack of notched character-generator disks at the center

A similar method with a stack of notched disks may have been used for generating Bernhard message strings in Hellschreiber format. When the messages had to be sent, the output of the photocell of the optical azimuth disk was simply disconnected, and the pixel stream of the text message generator was used instead.

Note that the command-uplink capability was not a standard feature of the "Bernhard" stations. Implementation of this data link system required a modification to the beacon, and was only implemented at three stations by the end of the war in Europe, including Be-9 at Bredstedt in the far north of Germany, and Be-10 at Hundborg in Denmark. It is unclear which 

Fig. 92: Early 1945, three of the Berhard stations had reportage/uplink capability

(source: adapted from p. 1 of ref. 292)

Apparently, late 1943 / early 1944, the Lorenz company also experimented with an expanded Hellschreiber-based command data-link system, referred to as "Sägezahn" ("sawtooth", ref. 2C1).

The Bernhard/Bernhardine system was the first and only operational ground-to-air data-link system of the second World War that had freely formattable messages! Since about the year 2000, the same concept has been introduced to "modern" civil aviation: Controller-Pilot Data Link Communications (CPDLC). In 2015, its usage became mandatory in European airspace above 28500 ft. CPDLC is for up-linking of routine ( = non-time-critical) air traffic control instructions and clearances to aircraft via digital radio. Purpose: reduce the significant time that air traffic controllers spend on routine communications over VHF voice links, and help reduce miscommunications as well as "stuck microphone" issues (which block the radio channel). However, contrary to the Bernhard system, the pilot can now respond to messages, request clearances and information, and declare an emergency - all via the same system (in addition to voice radio).

REMOTE MONITORING-ANTENNA MAST & RECEIVER

The signals transmitted by the "Bernhard" beacon were monitored via a remote receiver and antenna. They were located at a nominal distance of 500 m (p. 21 in ref. 183 (German, 1943), but 400 m per ref. 13 (US, 1945) and 800 m per ref. 1 (UK, 1946) from the beacon. The postion relative to the beacon was accurately surveyed, so the relative bearing was accurately known.

So far, I have been able to determine the location of the monitoring antenna of the following Bernhard stations:

• Trebbin (Be-0): ca. 220 m west of the concrete ring (note that this was initially a test/development station).
• Mt.-St.Michel-de-Brasparts (Be-2): ca. 920 m west-northwest. Ref. 174G.
• Le Bois-Julien (Be-3): ca. 500 m northwest.
• St.-Michel-Mt.-Mercure (Be-5): ca. 410 m southeast. Ref. 174H.
• Bredstedt (Be-9): ca. 550 m southeast
• Hundborg (Be-10): ca. 1 km southwest
• Trzebnica/Trebnitz (Be-11): ca. 445 m south
• Buke (Be-13): ca. 550 m northwest.
• Aidlingen/Venusberg (Be-14): ca. 900 m due west. Ref. 103.
• Hornstein (Be-16): ca. 200 m.

The far-field of antennas starts about two wavelengths from the antennas, i.e., at about 20 m for the operating frequency of the "Bernhard". So, why locate the monitoring antenna and receiver so far away? Probably for three reasons. First of all, the input of a receiver close to the station would be overloaded, even during the passage of the "null" of the twin-beam radiation pattern, and the "null" would not be sharp enough close to the beacon. Secondly, it made obtaining good angular resolution during calibration adjustments easier. It is also possible that the Mercury Arc Rectifier of the locomotive drive system caused a lot of radio interference near the beacon. The latter was very important, in particular during calibration of the antenna radiation pattern. The 1935 Telefunken/Runge/Krügel/Grammelsdorff patent nr. 737102 proposes using a fixed-location remote receiver to check the direction of the beam-null, as measuring and balancing antenna feed-currents does not guarantee its correctness.

The vertical antenna was installed on top of a steel truss mast (lattice mast, cage mast; D: "Eisengittermast"). The antenna has a pointed tip, just like the feedpoint of the dipoles of the Bernhard's antenna arrays. A ladder was integrated into the mast. It consists simply of horizontal sections of L-bracket, mounted between one of the mast legs, and the braces to one of the adjacent mast legs. The box on which the antenna radiator is mounted, is about 50 cm wide. The monitoring receiver was located at the base of the antenna (p. 21 (pdf p. 18) in ref. 183, sheet 8 in ref. 189). The received signals were printed with a "Bernhardine" Hellschreiber-printer in the equipment room below the beacon's rotating superstructure (see Figure 143 above).

Fig. 93: The monitoring antenna mast of Be-11 at Trzebnica/Trebnitz

(photo (1980s): courtesy C. Piotrowski, used with permission)

This "Kontrollmast" (monitoring mast) had a height of 20 m (≈66 ft; p. 21 in ref. 183). According to US photographic intelligence (ref. 13), the mast was about 30 m (≈100 ft) tall, and the vertical antenna (hollow pipe) on top of it about 2.4 m (8 ft). Photometric analysis of the photo above shows that the antenna radiator (on top of the box at the top of the mast) is about 2.6 m tall, assuming a 20 m tall mast. I.e., it was a standard 1/4 wavelength vertical antenna. It has a pointed tip, just like the feedpoints of the vertical dipoles of the "Bernhard" antenna arrays, so possibly it was just half of such a dipole leg. The mast was installed on a concrete foundation.

The mast and antenna were built by Hein, Lehmann & Co., the same company that built and installed the dipole antenna arrays of the Bernhard systems for Telefunken. The tall mast was delivered pre-assembled to the "Bernhard" site - at least at Aidlingen/Venusberg (ref. 103). Telefunken placed an order for six such masts in 1941, at a price of 2020 Reichsmark (RM) each (ref. 177C). This is equivalent to roughly US$12500 and €11500 end-2016, based on general inflation data (ref. 178A-178C). Note that Consumer Price Index (CPI) inflation data does not necessarily apply to specific products (such as antenna masts, electronics) or services. The billing does not state if the price included the actual antenna rod.

The photo below shows the mast of Be-11 at Trebnica/Trebnitz in Poland. It is the only "Bernhard" mast that has survived to date (2014). It is being used for antennas of a local FM radio station. The officially registered height of this "object" is 22 m (ref. 129).

Fig 94 Looking up inside the monitoring antenna mast, and the base of the mast at Be-11 Trzebnica/Trebnitz

(©2014 C. Piotrowski, used with permission)

Fig. 95: The dimensions of the standard concrete foundation of the monitoring masts

(data source: Czarek Piotrowski, used with permission)

Each mast was placed on a 3x3 meter concrete slab foundation. The concrete slab is at least 75 cm thick (2½ ft). The one shown below on the left, has two oblong dimples (see arrows). They measure 19x17 cm and 21x21 cm, respectively. Their purpose is unknown. Possibly they are vertical holes in the concrete, for inserting steel posts for mounting equipment, such as shown in Fig. 97 below. Possibly, those posts were embedded in the concrete, and the photo shows the cutt off remnants.

Fig. 96: Concrete foundations of the monitoring mast of Be-9 at Bredstedt (left) and Be-10 at Hundborg

(sources: R. Grzywatz (Be-9); Hundborg Lokalhistoriske Arkiv (Be-10); both used with permission)

The monitoring receiver was located at the base of the mast (D: "Empfänger am Fuß des Masts"; p. 21 (pdf p. 18) in ref. 183, sheet 8 in ref. 189):

Fig. 97: Monitoring mast - remote-receiver and cable installed at the bottom of the mast

(source: ref. 13; probably Be-4 at La Pernelle,, based on the other photos in ref. 13)

Figure 97 above shows two equipment boxes installed near the bottom of the mast. Field line installations often had lightning protection at both ends: fuses (D: "Blitzschutzpatronen") in a junction box ("Anschlußkasten", AK). This may account for the second box.

The receiver was remote-tuned from the "Bernhard" station (D: "fernbedienter Empfänger"; p. 21 (pdf p. 18) in ref. 183, sheet 8 in ref. 189). Each "Bernhard" beacon used one of 32 operating channels in the 30-33.3 MHz frequency band. To be able to use the same monitoring receiver at all Be-stations, it had to be tunable from the control room beneath the rotating cabin. Another reason for remote-tuning is that the transmitting frequency could be changed for technical or tactical reasons. It took 1-2 minutes to change the receiver frequency to a new channel frequency (p. 27 (pdf p. 24) in ref. 183). The receiver audio was also fed to a monitoring loudspeaker in the guard office near the beacon (line item 29a on sheet 8 in ref. 189).

There was an underground cable between the receiver and the Hellschreiber printers & control equipment in the round room below the rotating superstructure of the beacon. There appear to be two different "remote receiver + cable" configurations:

• According to ref. 189, the cable was of type "Erdkabel RLM". This is a special in-ground cable with a very robust outer insulation ("Kabelmantel"). It had four conductors with a 1 mm² diameter (line item 28a on sheet 8 in ref. 189; ≈AWG #18). This would have supported two separate signal pairs, or three signal pairs with a common reference (e.g., ground/earth).
• Per ref. 10, it was a 5-pair telephone cable. According to that same reference, the remote receiver was a diode receiver with a single audio frequency amplifier stage. So, the cable would have supplied anode voltage and filament heater voltage to the remote amplifier tube.

So, what kind of remotely tunable receiver was used? The aircraft that used the "Bernhard" beacons had an EBL-3 receiver on board. The "F" version of this receiver had remote-control. However, the control interface by itself already required 4 wires just for tuning (p. 87 and Fig. 17 in ref. 72). Note that the antenna mast is also referred to as a "Diodenmast" (e.g., ref. 99). This German term suggest that a "Diodenempfänger" was used (a.k.a. "Detektorempfänger", "Kristalldetektorempfänger"). This is known in English as a "crystal radio" or "crystal set". They were popular in the early days of radio, and got their name from a small piece of crystal that was used in the signal detector. In the 1930s, the inconvenient "crystal detector" was replaced with a diode. Such diode-receivers are not only simple, they are also passive. No separate source of electric power, such as a battery or DC voltage via a cable, is required: the simple circuit is powered by the received radio signals. Also, it is very easy to remote-tune a crystal radio: all that is needed is a small low-rpm DC motor that rotates the shaft of the tuning capacitor (esp. a capacitor without angular limitation). Two wire pairs would have sufficed for audio (2 wires) and DC power (2 wires, with reversible polarity to change tuning direction).

Would the audio output of a diode-receiver have been strong enough, without active amplification? This depends on three parameters:

• The signal level required at the input of the Hellschreiber printer-amplifier in the cabin. A Wehrmacht Hell Feldfernschreiber had a specified nominal output signal amplitude of 2.5 volt (900 Hz tone pulses). To ensure proper printing at a receiving Feld-Hell machine, the maximum allowed cable damping was 5 Neper, which is about 43 dB, or a voltage attenuation factor of about 140x. That is, the printer amplifier required an audio input signal with a minimum amplitude of 2500 / 140 ≈ 18 mV.
• The signal attenuation (damping) of the audio signals over field telephone cable with a length of 1 km (the maximum distance between the mast and the "Bernhard" ring). According to a 1945 manual of the Hell Feldfernschreiber (ref. 146), its range over standard field telephone cable of type DL500 was 36 km (22 km when wet), 60 km over regular pupin-cables (D: "bespultes Kabel", "Pupin-Kabel"; cable with a loading coil/inductance at regular intervals, typ. 250 m for German field cable), and 160 km over special pupin-cable of type FL250. That is, worst-case 22 km for 43 dB damping, or no more than 2 dB for 1 km. The required minimum 18 mV plus 2 dB is about 23 mV. So that would have been the required minimum output signal of the diode-receiver.
• The RF field-strength induced at the remote antenna by the "Bernhard" transmitters and antenna system. Per the definition of the ITU (ITU-R BS.561-2), the field strength of a ½λ-dipole with an effective radiated power (ERP) of 1 kW is 222 mV per meter, at a distance of 1 km. Also see ref. 150. The "Bernhard" installation had an ERP of at least several kW (my estimate). I.e., at least several 100 mV per meter at the monitoring antenna. That would have been more than enough to generate 23 mV at the receiver output - at least during passage of the main lobes of the radiation patterns of the upper and lower antenna systems.

The remote receiver was not only used during normal operation of the beacon, but also during calibration and adjustment of the currents to the left- and right-hand antenna subsystems. The receiver audio could be connected to a strip chart recorder in the control room, for the purpose of recording the 360° antenna radiation patterns. It is possible that a diode receiver did not generate sufficient signal for accurate recordings, and an amplifier stage was required. It is always best (from a signal-to-noise ratio point of view)to place an amplifier right at the signal source, i.e., at the receiver, not at the other end of the cable.

The schematic below shows a crystal radio that can power a small loudspeaker (ref. 147). I.e., similar to a small 1-transistor radio, but completely without a tube or transistor amplifier! It has a double-tuned circuit, a full-wave diode rectifier, followed by a voltage-doubler. The output voltage across the capacitors can be connected directly to standard high-impedance headphones (4000 Ω). It can also be connected to a low-impedance load, such as a loudspeaker or a standard "600 Ω" phone line. To match that impedance, a simple output-transformer (about 1:6 to 1:10) must be used. Solid-state diodes were readily available at the time, such as "Sirutor" diodes that were used in various Hellschreiber models. These were quite suitable for crystal radios (ref. 148, 149), as they have a forward voltage (a.k.a. "knee" or "turn-on" voltage) of only 0.2-0.3 volt (Sirutor type 1b), unlike more modern silicon diodes.

Fig. 98: Schematic of a "crystal radio" receiver, capable of driving a small loudspeaker

(source: adapted from ref. 147)

Fig. 99: A "crystal radio" receiver built per the schematic above

(source: ref. 147)

ROTATIONAL SPEED

The official German Bernhard/Bernhardine system description documents (ref. 181, 183, Blatt 8 & 10 in 198A) clearly state that the Bernhard-beacon rotated once every 30 sec, i.e., at 2 rpm. The specified diameter of the center of the circular rail track ( = midway between the two rails) was 2x10.55 = 21.1 m (ref. 193). Hence, the track length was 66.28 m. This means that at 2 rpm = 120 rph, the small locomotives that turned this enormous antenna installation, moved at a respectable speed of 8 km per hour (5 mph). As described in the "Locomotive system" section below, the rotational speed of the system was determined by a single synchronous 3-phase AC motor in one of the four locomotives. The 3-phase AC power was provided by a DC-AC inverter that had a fixed reference frequency. Hence this motor could only turn at the reference speed, and the speed was monitored very accurately. The rotational speed of the beacon was kept constant to within -0.2 to +0.3% ! See p. 80 in ref. 181 and p. 8 & 18 in ref. 183.

The official German system descriptions and the manual of the FuG 120 "Bernhardine" printer system also state the same 2 rpm speed (top of Section B on p. 5 in ref. 15, sheet 8 & 10 of ref. 198A; also §3 in ref. 10). Moreover, the "Bernhardine" printers were simply not compatible with antenna rotational speeds that deviated more than a couple of percent from that nominal speed! As with other types of synchronized teleprinter systems, the motor of the Bernhardine-printer had to turn 1-2% faster than nominal system speed (p. 18 in ref. 183).

There are some persistent statements (e.g., ref. 5A) that the "Bernhard" beacons rotated with a period other than 30 sec. Some of the sources for these statements are the following:

• The French resistance explicitly reported in 1943 that this station Be-3 at Le-Bois-Julien rotated once per minute (p. 62 in ref. 91).
• A British 10 cm [ = 300 MHz] radar station at Fairlight (on the East Sussex coast, east of Hastings, 87 km [54 miles] northwest of Be-3 at Le-Bois-Julien) concluded that the station appeared to rotate once a minute (ref. 173B, December 1943). Likewise, extensive radar measurements early-June 1944 also concluded that the rotation period was 52-60 sec (ref. 173A).
• Luftwaffe POWs in the UK reported 1 rpm for the Bernhard system in general (§10, 18, 19 in ref. 6C)
• A 1946 US air force survey of German electronics development, stating that "... information is printed once per minute" (ref. 93B). This may have been based on war-time "intelligence" from other sources.
• A "reliable informant" who saw the Be-6 station at Marlemont/France station in operation, reported to the British that he was told [correctly] that it rotated with a speed of 8 km/h. Based on the wrong British photometric assumption that the Bernhard-ring had a diameter of 82 ft [25 m], a rotational period of 36 sec. was estimated. Ref. 173E. For the actual diameter of 71 ft [21.5 m], the correct period of 30 sec. would have been obtained.
• Ref. 225 and 226A state that the system rotated at 1 rpm with and the beam was received by aircraft during 10 sec per rev.
• Ref. 175B (RAF 192 Squadron) mentions that the beam was received by aircraft during 5-10 sec per minute. This may suggest 1 rpm. Note that typical reception time was actually 3-5 sec per rev, so 5-10 sec / minute could be 1 or 2 rpm...

The 1936 Lohmann/Telefunken patent 767528 states that the limiting factors for the upper limit of the antenna's rotational speed, are the printing speed of the Hellschreiber and the required pixel resolution of the printed information. Given the large size and weight of the antenna system, there are obviously also mechanical considerations for the upper speed limit. The patent proposes to resolve this, by quadrupling the number of antenna beams, spaced at 90º intervals. Each optical encoder disk would simply have four "light source plus photocell" pairs (two pairs shown in the diagram above), that could be adjusted to account for angular offsets between the beam centerlines.

THE CABIN

Below the antenna installation, and rotating with it, is a steel truss bridge. The rectangular bottom frame of the bridge is made of heavy I-beams. It is supported by the four locomotives and by the round building at the center of the concrete ring. The upper frame of the bridge was suspended from the large lattice truss-joist of the lower antenna system.

Figure 100: Cabin of Be-4 at La Pernelle/France

Inside the bridge is a long wooden cabin ("mitdrehendes Holzhaus"). It measured about 20x4x3m (LxWxH, ≈66x13x10 ft), based on p. 20 in ref. 183, as confirmed by photometric analysis of available photos. Its length is close to the inside diameter of the ring (≈20.5 m). The cabin was made of heavy wooden planks. There is a entrance door and set of stairs at both ends of the cabin.

Ca. 1943, Telefunken contracted its standard antenna structure supplier, Hein, Lehmann & Co., to provide "Panzerung von Holzhäusern" for 12 "Bernhard" stations (purchase order nr. 253/33163, ref. 177C). That is, for sheet-metal protection of the wooden cabin. "Panzerholz" is plywood that is covered with sheet metal armoring on one side or on both sides. The price was 4167 Reichsmark per BE-station. Based on general inflation data, this is equivalent to ca. US$21,900 or €20,250 (early 2017, ref. 177). The metal protection was only installed at five stations (Be-2, Be-3, Be-4, Be-8, and Be-10), before the course of the war intervened. The protective panels probably took the form of large panels that could be slid in front of the cabin windows, see Fig. 91 below. The wooden part of the panels involved Fa. Rostock in Trebbin (ref. 176A). This company operated three owned or leased sawmills in Trebbin (close to Be-0) since the early 1930s, and supplied wooden construction materials for a number of "radar" installations and other Wehrmacht constructions.

Fig. 101: The cabin at Be-10 Hundborg/Denmark - with protective siding panels

At some "Bernhard" sites, these sliding covers are on the outside of the bridge frame that suspends the cabin from the truss-joist. At other sites, these panels slide between the cabin and that frame.

The cabin contained the two transmitters, AC/DC electrical power distribution and controls for the locomotive motors, and for cabin heating & lighting. See the "Electrical & signal distribution" section. Ref. 13 (p. 4.09) suggests that the cabin was divided into three sections. The section on the right (looking at the front of the antenna system) contained the transmitter equipment. This is confirmed by the layout diagram of the Be-0 station. The center section housed the controls for the four electric locomotives. The section on the left was a workspace. A plaque at La Pernelle (Be-4) states that it had one or more beds in it.

The photo below shows the power distribution and control panel ("Schaltwandtafel") inside the rotating cabin of Be-10 at Hundborg. The spoked handwheel in the lower right-hand corner (sheet 15/20 in ref. 189) belongs to the circuitry for bringing the locomotives up to speed from standstill, and for slowing down to standstill ("Kontroller und Anlaßwiderstand"). Also see the "Electrical & signal distribution" section.

Fig. 102: German engineer describing controls in the cabin of Be-10 at Bredstedt to a member of the RAF-ADW

(source: Australian War Memorial photo SUK14636, public domain; ca. August 1945)

THE FOUR CORNER-BLOCKS

At each of the four corners of the cabin, there is a "block" or square silo of about 1½x1½x2 m (WxDxH; ≈5x5x6½ ft). They are mounted on a cantilever, away form the main cabin and above the rear bogie of the locomotive underneath. There are no openings for ventilation in the walls or the roof. No conduits appear to emanate from the bottom. From the available photos it is clear that there are no windows, and it appears that there is no door. Whatever was in there, apparently did not require access! So it was not electrical or mechanical equipment, nor a container with brake sand for the locomotives (for which there would have been a tube descending in front of the powered wheels).

Fig. 103: One of the cantilevered corner sheds in a 1946 film clip of Be-4 at La Pernelle)

(source: Cinémathèque de Normandie)

The next photo shows that the blocks were empty at some point in time (probably during construction, as the photo dates from March 1943):

Figure 104: Low-altitude oblique RAF aerial photo of the La Pernelle site

(source: ref. 172A; photo by G.R. Crankenthorp, taken on 3 March 1943)

Most likely, they contained dead weight (e.g., stone, sand, concrete, lead), to get more weight on the traction wheels of the locomotives - even though the entire structure carried by the locomotives was already quite heavy by itself. However, the blocks must have had considerable weight: a triangular stabilizing arm was installed between the cantilever supporting each block, and the bottom frame of the bridge:

Figure 105: One of the four stabilizing arms of the turntable at Be-10 in Hundborg

At some sites, these blocks have a flat roof (e.g., Be-9 at Bredstedt, Be-10 at Hundborg). At other sites, the four-sided roof is pointed (e.g., Be-4 at La Pernelle, Be-7 at Arcachon).

Figure 106: Corner-sheds with a flat roof (Be-10 at Hundborg/Denmark)

Figure 107: Corner-sheds with a pointed roof (Be-4 at La Pernelle/France)

Unlike the main cabin, the walls are not made of wooden planks - they apear to have been made of sheet metal:

Figure 108: Corner-block of Be-9 at Bredsted/Germany - note the construction details

(unedited photo taken May 1945 by Flt. Lt. Herbert Bennet, RAF Mobile Signals Units of No. 72 Signals Wing; © David Bennet; used with permission)

In available post-war photos of "Bernhard" installations (La Pernelle, Arcachon), the main cabin is completely stripped of its materials - but not the four corner-blocks! Either the material was hard to remove and carry away, not valuable enough, or not usable for some other reason.

Fig. 109: Post-war photo of Be-7 at Arcachon - installation dismantled and stripped, except for the corner sheds

Fig. 110: Post-war photo of Be-4 at La Pernelle - installation dismantled and stripped, except for the corner sheds

(source: unknown)

The photo below (a post-war postcard) shows the site of Be-2 at Mont-St.-Michel-de-Brasparts. The installation was dismantled in 1946, but the (solid!) corner blocks were abandoned inside the concrete ring:

Fig. 111: Postcard of the Bernhard site Be-2 at Mont-Saint-Michel-de-Brasparts (late 1940s / early 1950s?)

(source: unknown)

No such blocks have been found at the "Bernhard" sites were there still are visible remains these days.

THE LOCOMOTIVE SYSTEM

The superstructure of the "Bernhard" (i.e., the antenna system and bridge with cabin) was rotated by four electrically powered locomotives on the circular rail track. Each locomotive had two bogies (US: trucks). The photos below shows that each bogie had two axle-boxes with leaf-spring suspension. Such axle-boxes typically have greased sliding bearings (a.k.a., journal bearings, not ball bearings). Each of the locomotives had 2 x (2+2) = 8 wheels, so the four locomotives had 32 wheels in total. The weight of the superstructure was carried by the four locomotives and the round central support building below it. Let's assume that the weight was evenly distributed among the four locomotives. So, the combined locomotives carried 4/5 x 120 = 96 metric tons. Hence, each wheel carried a weight of 96 / 32 = 3 metric tons. This is well below the standard railway limit of at least 11 tons/wheel, for the load at which both the rail head and full-size train wheels are damaged (about 6 tons/wheel for standard tramway ("Sraßenbahn") wheels).

Fig. 112: Each locomotive has two bogies (Be-10 at Hundborg) - 32 wheels in total

(source: www.gyges.dk, used with permission)

Based on photometric analysis, the locomotives measured about 4x1.2 m (LxH, 13x4 ft). The wheels on the outside rail had a diameter of about 60 cm (24 inch), the ones on the inside rail about 55 cm (22 inch). This is based on the diameters of the inside and outside circular rail track being about 4.3% different, and the wheels on the inside rail having a diameter that is 2 x 2.4 = 4.8 cm smaller than the wheels on the outside rail. The wheels have about half the size of a standard rail wagon wheel, which is about the size of a tramway wheel.

Fig. 113: The side of the locomotive on the outside of the track - direction of motion is to the left

The next photos show that the locomotives had large access holes, normally covered with a rectangular cover plate. The right-hand photo shows that the locomotives had external down-gearing between one of the two motors and the forward bogie. The down-gearing ratio is small: about 1.6:1. The gearing is covered, so it is not sure if it was a chain or a belt. The width of the cover box suggests a belt.

Fig. 114: Close-up of two of the locomotives in a 1946 film clip of Be-4 at La Pernelle)

(source: Cinémathèque de Normandie)

The photos in Fig. 114 and 115 show that the locomotives supported the weight of the superstructure at the point halfway between the front and rear bogies - which makes sense for weight distribution. There was ball socket ("Kugelpfanne") at this point on top of the locomotive (p. 8 in ref. 193). The socket held a large downward-pointing ball-stud ("Kugelzapfen") that was mounted underneath the I-beam frame of the superstructure. Between the superstructure and the locomotives, there are only conduits for electrical power cables to the motors (and a tachometer signal, but only at locomotive nr. 4, see Fig. 116).

Fig. 115: Ball joint on a locomotive of Be-12 at Nevid and electrical conduits to the motors (magenta circle)

(source: brdy.org)

As stated above, each locomotive had two double bogies. Each locomotive had two motors. Per ref. 10 (§7), each motor drove two wheels of a bogie. Presumably, this means that each bogie had one motor, and this motor only drove one axle of that bogie. Dividing motor power evenly between both axles of a bogie might have optimized traction, but would have complicated the construction.

Three of the locomotives had two DC motors. The fourth locomotive had one DC motor and one synchronous AC motor:

Fig. 116: Motorization of the four locomotives

(source: derived from ref. 10, 189, 190)

There were three motor types used in the locomotives (ref. 10 (§7), ref. 190):

• "Hauptantrieb": main drive, 220 volt DC-motors. Only locomotives nr. 1-3 had such a motor. They were used to smoothly accelerate the rotation from standstill to close to the nominal speed, and provide the majority of the drive power that was required during normal operation.
• Per ref. 189, the specified gauge of the wiring to each of the motors was 25 mm² (≈ 5.6 mm Ø, equivalent to about AWG 3). The gauge between the control panel and the variable starter resistance was 95 mm². I.e., a diameter of 11 mm (AWG 3/0-4/0). Note that aluminum wiring was specified for all cables. Aluminium has 61% of the conductivity of copper.
• Input fuses were rated 160 A / 500 V.
• "Synchronantrieb": synchronous drive, 3-phase 380 volt AC 50 Hz synchronous motor drive. Only locomotive nr. 4 had such a motor. It was used to accurately maintain the nominal rotational speed - without an electrical or electromechanical control system! This motor was engaged once the DC main drive motors had brought the system to within 90-95% of the nominal speed. At that point, the synchronous motor would capture and lock on to the nominal speed, i.e., the excitation frequency of the 3-phase power (which is why that frequency had to be accurate).
• The wire gauge for the 3-phase AC was 16 mm² (≈ 4.5 mm Ø, equivalent to AWG 5). Modern 4-conductor insulated aluminium cable of this gauge has a current rating of 50 amps (e.g., cable type NAYY-J). The wiring for the DC field excitation was 2.5 mm² (≈ 1.8 mm Ø, ≈ AWG 13). Modern 2-conductor cable of this gauge has a current rating of about 18 amps.
• The associated fuses were rated 80 A / 500 V and 6 A / 500 V respectively.
• "Nebenantrieb": auxiliary drive DC-motors, with a separately controlled field winding (a.k.a. "separately excited DC-motor"). All four locomotives had such a motor. The rotation direction of these motors was reversible. These motors were disengaged during normal operation. they were only used for positioning the system during tests and calibration/adjustment. These motors were significantly down-geared, to be able to (very) slowly rotate the system.
• Per ref. 189, the specified gauge of the wiring to each motor's field winding was 2.5 mm² (≈ 1.8 mm Ø, ≈ AWG 13), and 6 mm² (≈ 2.8 mm Ø, ≈ AWG 9-10) to each armature winding.
• The two input fuses were rated 35 A / 500 V.

At the nominal speed of the system (2 rpm), the locomotive wheels had to turn at about 72 rpm:

• The diameter of the outer rail track was 21.95 m. Hence, the length of the outside track was close to 69 m.
• The diameter of the outside wheels of the locomotive was about 60 cm = 0.6 m. Hence, the circumference of those wheels was close to 1.88 m.
• I.e., the wheels made about 35.8 revs per revolution of the system.
• As the system turned at 2 rpm (30 sec/rev), the wheels ( = axles of the locomotive bogies) turned at about 71.6 rpm.

So, the synchronous drive motor definitely required some down-gearing. Its speed was fixed: it was determined by the 50 Hz electrical power and the (integer) number of rotor pole pairs. A direct drive would have required a prohibitively large number of rotor pole pairs: 50 Hz x 60 sec/min / 71.6 rpm ≈ 42. Most likely, the auxiliary drive motors also required down-gearing. The gearings would have been integrated with drive axles of the locomotive bogies. Note that Fig. 114 above shows external gearing, but only with a small gear ratio. It is unknown which drive it was part of.

How powerful did the locomotives actually have to be? Let's do a simplistic reasonableness check, using the definition of "horsepower". On a level ( = horizontal) track, the required locomotive horsepower HP_loc is (ref. 156, 157):

 HP_loc = W x T x S / 375

where

 W = total gross train weight in tons (1000 lbs)
 T = total Train Resistance (a.k.a. Starting Resistance) per ton. A standard value used in the railway industry is 8 lbs/ton. Modern rail systems have a lower resistance.
 S = speed in mph
 375 is a constant that assumes that no HP is used for driving accessories (gearing, compressor, alternator, ...)

Converting this to metric units, we get:

 HP_loc = W x T x S / 271

where

 W = total gross train weight in metric tons (1000 kg)
 T = total Train Resistance per metric ton = 8 kg/ton
 S = speed in km/h = mph / 1.609

Total weight of the rotating superstructure was 120 metric tons, distributed among the four locomotives and the central support at the center of the concrete ring. The locomotives carried 4/5 x 120 = 96 metric tons. Wind load would increase this value. The specified diameter of the center of the circular rail track ( = midway between the two rails) was 2x10.55 = 21.1 m (ref. 193). Hence, the track length was π x 21.1 ≈ 66.3 m. This means that at 2 rpm = 120 rph, the small locomotives moved at a respectable speed of 120 x 66.3 = 8 km per hour (5 mph). Hence, the required total locomotive horse power is 96 x 8 x 8 / 271 = 22.7 HP at the traction wheels. There is down-gearing between the motor and the driven wheels. Let's assume a reasonable transmission efficiency of 85%. For the required total motor horsepower we now get:

 HP_motor-total = HP_loc / 0.85 = 22.7 / 0.85 = 26.7 HP

The "Bernhard" system used four locomotives. So, the required motor horsepower per locomotive would be:

 HP_motor = HP_motor-total / 4 = 26.7 / 4 ≈ 6.7 HP

Note that locomotive motors did not have to drive accessory loads such as generators and blowers. Hence, traction horsepower = brake horsepower. The above derivation does not take into account a requirements to accelerate to the nominal speed within a certain amount of time!

The rolling resistance of a railway vehicle (which is a science all by itself) is the sum of all forces acting through the wheels and the axles, that oppose motion of that vehicle. There are many sources of rolling resistance. Some vary only with weight (e.g., journal bearing resistance, rolling friction, track resistance), some are linearly proportional to speed (e.g., wheel-flange contact, wheel-rail interface, lateral and vertical movement), some depend on the square of the speed (e.g., aerodynamic), and some on the fourth time-derivative of displacement. Examples:

• Bearing friction.
• Elastic deformation of the wheel-tread and of the rail, in the wheel-rail contact area. Note that the contact surface between a wheel and the rail is a very small elliptical area, called the "contact patch". It is typically only about 15 mm (0.6 inch) across! The weight of the wheel and the load that it carries, makes a "dent" in the surface of the rail head. This dent moves with the wheel, and is like a very small bow wave. So, trains actually always go uphill, even if the track is perfectly horizontal!
• Losses due to wheel creep (during accelerations and decelerations, the elastic deformations cause the actual wheel displacement to be be different from its rolling distance).
• Losses due to grinding of wheel flanges against the rail head, and "hunting" (horizontal back-and-forth waving movement of the bogies on the track).
• Wheel noise (vibration and resonances in the wheels).
• Suspension "jounce" (the fourth time-derivative of displacement), due to impacts on rail joints (if any), and associated rebounds. Bumps and bounces convert horizontal momentum into vertical momentum; the associated energy is dissipated in the suspension.
• Track deformation (Rayleigh waves).
• Aerodynamic drag that acts on exposed wheels and on the body of the locomotive. At low speed, this is normally quite small, if not negligible. However, in the case of "Bernhard", there is also drag of the large antenna system due to system movement and wind load. The antenna system is symmetrical with respect to the vertical axis of rotation. So there is a "push & pull" effect, depending on whether the movement is upwind or downwind. Wind will change the apparent weight on the locomotives.
• Curve resistance, due to the radius of the curvature of the track. Note that regular "1 meter" gauge track typically has a minimum curve radius of 45 - 60 meters, about 4 - 6 times that of the circular "Bernhard" track! Without special measures, the curve resistance would have been quite high!
• The "Bernhard" track had a gauge ("Spurweite", distance between the inside of the rail heads) of 842 mm. The on-center distance between the rail heads was 900 mm (≈ 3 ft). Ref. 193.

In normal rail applications, total resistance at low speed (less than about 15 km/h, ≈10 mph) is dominated by friction of the axle bearings (ref. 159). Note that a train with steel wheels on steel rails has a friction factor that is about 80% lower than that of a truck (UK: lorry) with rubber tires on pavement! Also note that the central load-bearing support below the rotating superstructure had a large ball bearing (diameter ≈40 cm ≈16 inch). Clearly, it too caused some rotational resistance.

Electrically powered rail vehicles (electric and diesel-electric train locomotives, streetcars/tramways, subways) traditionally used DC traction motors. This remained the case until well after the advent of solid-state power electronics, in particular gate turn-off (GTO) thyristors, in the early 1960s. DC traction motors where primarily of the series-wound brushed type. I.e., with a commutator, and the field windings in series with the motor's armature windings. Note that brushless DC-motors only date back to the late 1950s, ref. 160.

Series DC-motors can produce their highest torque at low speed: as much as 3-8 times the full-load torque at nominal speed. This is ideal for traction applications. For a given field flux, DC motor speed is determined by the armature voltage, whereas the delivered torque is driven by the armature current.

Fig. 117: Basic types of wound Direct Current (DC) motors - classified by placement of the field winding

Fig. 118: Basic characteristics of series, shunt, and compound DC motors

As stated above, the speed of a DC motor depends on the voltage across the motor's armature and the field flux. Standard methods to vary the armature voltage of a series motor are:

• An adjustable resistance placed in series with the motor's armature.
• Ward-Leonard drive system.
• Rectified adjustable AC-voltage (ref. 161, 163G).

There are many other flavors of motor speed control (variable AC frequency, Pulse Width Modulation, ...). They are generally beyond the scope of this discussion, and of the technology available at the time.

The adjustable series-resistance method (e.g., rheostat) has a major disadvantage: poor speed regulation ( = speed is highly load-dependent). There are also very high losses ( = heat dissipation) in the series resistance at low speed. That is, during speed-up from, and slow-down to stand-still. Some speed-control methods for series DC-motors are illustrated in Figure 119 and 120.

Fig. 119: Speed control of a series DC-motor via field or armature diverter, tapped field-winding, variable series resistance

Fig. 120: Speed control of a series DC-motor via series-parallel reconfiguration of split field-winding and multiple motors

The Ward-Leonard Drive System (D: "Leonardsatz", "Ward-Leonard-Umformer", "Leonard Doppel-Umformer") is basically an electro-mechanical way of generating a variable DC-voltage to control the speed of a DC-motor. Ref. 162A-162G. It was invented by Harry Ward Leonard in 1892. For about 75 years, there were few practical alternatives to this system - until the advent of solid-state power-electronics such as thyristors in the 1960s. Worldwide, this was the normal way to provide smooth, step-less control of the speed of high-power DC-motors, from zero to full speed. It has been - and still is - used in many applications, such as cannon/gun- and turret-aiming, elevators, rolling mills, cranes, hoists, mining (colliery) winders, diesel-electric propulsion of locomotives and of special ships, strip-mining shovels, and heavy radar antennas. German WW2 radar antenna systems with a Ward-Leonard drive include the "Wassermann S" (FuMG 42; see figure 2 in ref. 162G; 36-60 m tall / 4 m diameter column, weight up to 60 tons) and the AEG-Telefunken "Würzburg Riese" (FuSE 65) with its large dish antenna (7.5 m diameter, 9.5 tons; ref. 162F). Allied radar system also used Ward-Leonard drives. E.g., the 20 ton antenna of the British "Marconi Type 7" was rotated with a 15 HP DC-motor, controlled with a Ward-Leonard set comprising a 24 HP 3-phase motor, a main DC-generator, and a small DC exciter generator. Ref. 162H.

The Ward-Leonard Drive System consists of a Ward-Leonard Drive Unit and a shunt-wound DC motor. The Drive Unit consists of a motor-generator. The motor (referred to as the "prime mover") has a near-constant speed. This can be a 3-phase or single-phase synchronous AC motor, or a combustion engine (diesel, gasoline/petrol) with a speed governor. The output shaft of the motor is coupled (direct-drive) to the input shaft of a DC-generator. The output voltage of this DC-generator is connected to the armature of the DC-motor that drives the load. The DC-motor need not be located near the motor-generator. The shunt-field of the DC-motor is connected to a constant voltage source; hence, the motor's excitation field (flux per motor-pole) is constant, and the torque only depends on the armature current - independent of the motor speed. The shunt-field of the DC-generator is connected to that same constant-voltage source, though via a rheostat (large variable resistor).

Fig. 121: Ward-Leonard Drive System

The generator's output voltage is varied by changing the generator's field current with the rheostat. In turn, this changes the DC-motor's armature voltage, and hence its speed. The constant voltage source may be a rectified AC voltage (if the prime mover is an AC-motor). It can also be generated with a small DC exciter-generator ("selbsterregter Erregergenerator"), that is also driven by the prime mover, and has its shunt-field connected to its own armature (hence, "self-excited").

The Ward-Leonard drive unit is an electro-mechanical multi-kilowatt amplifier: a small change in the input current (generator field) results in a large change at the output (generator armature voltage and current). However, in its basic form, it is an open-loop control system: the rotational speed of the load is not measured and fed back in order to adjust the generator's field current. Hence, that speed is not regulated with the high precision required in the "Bernhard" application. Note that it is possible to expand the basic Ward-Leonard system with such a feedback loop.

Another drawback is that both the AC-motor (or the engine) and the DC-generator must be dimensioned for the full and peak power of the load-driving DC-motor(s) and system inefficiencies.

System efficiency is driven by the product of the efficiency of the three machines (AC-motor, DC-generator. DC-motor), and typically lower than that of rheostat control and field control methods. A single Ward Leonard drive unit can control multiple load-sharing DC motors in parallel ("group control"). Variations of the Ward-Leonard drive system are electro-mechanical amplifiers such as the Metadyne (1930s) and the Amplidyne (1940s).

As elegant and effective as the Ward-Leonard drive system may be, it was not what was used in the "Bernhard" to provide a variable DC-voltage to the locomotive drive system! The DC motors were regulated with series rheostat for speed up from standstill and down to standstill.

There are two basic types of AC motors: asynchronous motors and synchronous motors. Both have two main parts: a stator and a rotor. In a 3-phase motor (synchronous or asynchronous), the stator basically consists of triple pairs of formed coils of wire. Each coil is mounted in the slots of a laminated steel core. The coil pairs are spaced evenly around the stator. See Fig. 122. The two coils of each pair are connected in series.

Fig. 122: Simplified cut-away view of the stator of a 3-phase AC motor (synchronous or asynchronous)

Each stator coil-pair is energized by one phase of the 3-phase AC electrical power. Each energized coil-pair forms a pair of magnetic poles. The resulting magnetic field extends into the air gap between the stator and rotor, and into the rotor. The magnetic field strength and polarity of each pole-pair changes cyclically, as the AC excitation is sinusoidal. When all three phases are connected, the stator generates a rotating magnetic field (RMF). This field has a constant amplitude, and rotates with the same speed as the 3-phase excitation. E.g., for an excitation frequency of 50 Hz = 50 cycles/sec, the RMF rotates at 50/sec x 60 sec/min = 3000 rpm, and at 3600 rpm for 60 Hz excitation.

Fig. 123: Concept of how RMF is generated by a 3-phase stator when excited with 3-phase AC power

We all know that unlike magnetic poles (North-South) attract each other, and like magnetic poles (North-North, South-South) repel each other. The motor's rotor can turn freely inside the stator. Let's take a rotor that consists of one or more magnetic pole-pairs. The stator generates a rotating magnetic field, so the magnetic rotor poles will try to remain aligned with that field: the rotor turns. There are several ways to make a stator pole-pair, see Fig. 123:

• A permanent magnet (bar magnet).
• A coil with the ends short-circuited. By itself, such a coil does not generate a magnetic field. However, if a varying magnetic flux is induced in this coil, a current will circulate in the coil. The direction of this current is such that it opposes its cause (Lenz's Law). The cause is the varying induced flux. With the RMF of the stator, the induced flux in the rotor winding only varies if the rotor does not turn at the same speed as that RMF. This induced varying flux, combined with the induced current, generates an electro-magnetic force (EMF, Faraday's Law) that acts on the coil conductors. The magnitude of the torque ( = rotating force) is proportional to the relative rotational speed of the rotor, compared to the synchronous speed ( = the speed of the RMF). The speed difference is called "slip". The direction of the torque is such that torque is reduced (remember: Lenz' Law): in other words, such that the speed difference is reduced.
• Important: there is no rotational force if the rotor turns at the synchronous speed! Hence, the rotor never turns at the synchronous speed, but always slower. The amount of slip depends on the mechanical load that is driven by the motor. The heavier the load, the larger the slip ( = lower motor speed). If the load varies, the speed varies. An AC motor with such a rotor is called an asynchronous motor. As it works on the principle of induction, it is also called an induction motor. Low-power asynchronous motors can have a slip of 5-10%, whereas asynchronous motors with a higher power rating have approx. 2-5% slip.
• The rotor coils can be implemented as actual coiled wires (in which case the rotor windings are typically made accessible via slip rings), or simply be implemented as so-called "squirrel cage" (two parallel metal rings with a number of evenly spaced metal bars between them, often at a skew angle).
• A coil that is energized by a DC voltage. This is equivalent to a permanent magnet. As the rotor has to turn, the DC power is supplied via slip rings. When the rotor is at standstill or at low speed, the alternating polarity of the stator's rotating magnetic field (RMF) sweeps by the poles of the rotor relatively fast. Each rotor pole is cyclically briefly pulled into one direction (without producing sufficient starting-torque), and than briefly in the opposite direction. The rotor may vibrate but will not turn!
• Important: a motor with such a stator is inherently not self-starting! The motor needs a supplemental drive mechanism (e.g., a starter winding incorporated into the motor, or another motor) to first be accelerated to 90-95% of the synchronous speed (i.e., < 5-10% slip) - without energizing the rotor. At that point, the rotor is energized and automatically pulls into synchronism (a.k.a. "in step") with the RMF: the rotor poles are locked to the RMF and the rotor turns at synchronous speed. This is great for a constant speed drive application: no need for a closed-loop speed control system! For obvious reasons, a motor with such a rotor is called a synchronous motor.
• Important: a synchronous motor turns at the exact synchronous speed, from no-load to full-load!
• Contrary to the asynchronous motor, the motor torque is generated as a result of the physical angle between the stator and rotor. This phase angle is called the load angle, coupling angle, or torque angle. An increase in mechanical load causes this angle to also increase - but synchronous speed is maintained! If the mechanical load ever exceeds the motor's maximum torque, the rotor completely loses synchronism (drops "out of step") with the stator's RMF, and the motor comes to rest. The same happens if the rotor supply voltage or the stator supply voltage is reduced excessively.
• For a constant load, the motor's EM torque is equal to the load torque and the torque angle is a non-zero constant. A sudden change in load will upset this steady state. The locking between the rotor and the RMF is not rigid! A sudden increase in load causes a temporary slow down of the rotor, which simultaneously increases the torque angle and the EM torque. This accelerates the rotor back to the synchronous speed. As the rotor reaches synchronous speed again, the torque angle is larger than needed and the rotor speed overshoots the synchronous speed. This reduces the torque angle, and the EMF torque drops simultaneously. The rotor decelerates and the rotor speed now undershoots the synchronous speed, etc. I.e., the rotor speed oscillates around the sync speed. This phenomenon is known as "hunting" and "phase swinging". Under certain conditions, these oscillation may diverge ( = exponentially increase in amplitude), even to destructive levels. The oscillation can be reduced by adding damping windings (a.k.a. amortisseur windings) to the rotor, and by large load inertia (e.g., a heavy flywheel, such as the rotating structure of the Bernhard system).

Fig. 124: Possible configurations for a pole pair of an AC motor

The following graphs show the torque-versus-speed characteristics of an asynchronous and a synchronous AC motor:

Fig. 125: Torque-vs-speed characteristic of a typ. asynchronous AC motor (left) and of a synchronous AC motor

The synchronous rotor speed of an AC motor is clearly proportional to the RMF that is generated by the stator, i.e., to the frequency of the AC excitation of the stator. However, it also inversely proportional to the number pole-pairs of the rotor. The simple formula is given in the figure below. For instance, for a 50 Hz excitation, the synchronous rotor speed N_s is 3000, 1500, 1000, and 750 rpm, for 1, 2, 3, and 4 pole-pairs, respectively. The number of pole-pairs is an integer value, so it obviously cannot be chosen as freely as an excitation frequency. Compared to asynchronous motors of equal power and speed, synchronous motors are attractive for low-speed ( < 300 rpm) and ultra low-speed drive applications: their efficiency is high, their power factor can always be adjusted to 1 (via field current adjustment), and they are less costly.

Fig. 126: Synchronous motor rotors with 1, 2, & 3 pole-pairs and slip-rings for DC power

(rotors shown with salient ( = protruding) poles, typ. for low speed applications, rather than cylindrical rotor with distributed windings)

The characteristics of the synchronous motor of "Bernhard" locomotive nr. 4 are not known: neither the frequency of the 3-phase AC (other than "mid-frequency", which is typ. 400 - 2000 Hz), nor the number of rotor poles, nor the torque rating.

At least one of the locomotive motors of the Be-13 station at Buke was built by Ziehl-Abegg Elektrizitätsgesellschaft m.b.H., of Berlin-Weißensee. It was a 10 kW (13.6 metric horsepower, 13.4 US hp) "low rpm" motor (ref. 99). This suggests that it may have been the synchrounous AC motor. The motors at (some) other Bernhard stations may have been built by Siemens (e.g., ref. 103). This was probably Siemens-Schuckert, who also manufactured electric locomotives.

Ziehl-Abegg is a company specialized in electric motors. It was founded in 1910 by Emil Ziehl and the Swedish investor Eduard Abegg as Ziehl-Abegg Elektrizitäts-Gesellschaft m.b.H. Abegg dropped out of the partnership the same year, as he could not come up with the required funds, and the patent that he brought into the deal (ref. 214) proved useless. However, Abegg's initial "A" was retained (as a solid triangle) in the the "Z-A" company logo. Ref. 154. In 1897, Emil Ziehl invented the external rotor motor ("Außenläufermotor", outrunner motor: stator inside the rotor - very compact and excellent weight balancing). In 1904, he invented electrically powered gyroscopes with gimballed suspension. Prior to 1910, Emil Ziehl had developed electric motors and tested generators at AEG, and developed gyro-compasses at Berliner Maschinenbau AG (BEMAG, frmr. Eisengießerei und Maschinen-Fabrik von L. Schwartzkopff). BEMAG was a manufacturer of locomotives powered by steam, compressed air, and electricity. Ziehl-Abegg made DC-DC converters (DC-motor + generator) for Zeppelin airships and airplanes. Telefunken was a major customer. They also made electro-mechanical transverters ("Drehstrom-Gleichstrom-Umformer", i.e., AC-motor + DC-generator, as in Ward-Leonard Drive Systems) for elevators and generation of anode voltage of large transmitters, transformers for directional-gyros (e.g., SAM-LKu4), motor-generators such as the U 4a, and the motor-generator-alternator of the U 120 of the "Bernhardine" system. After the war, the production facilities were carried off to the Soviet Union. In 1947, the company restarted, this time in the south of Germany (some 70 km northeast of Stuttgart). These days, Ziehl-Abegg AG is a manufacturer of electric motors for elevators, ventilation and air-conditioning systems.

Fig. 127: 1912 advertizing poster, listing in 1943 Berlin phonebook, wall plaque on the building in Fig. 109

(source of poster: ref. 155)

Fig. 128: Ziehl-Abegg postmark on an envelope - 1938

(source: www.briefmarken12.de)

Fig. 129: Company buildings of Ziehl-Abegg Elektrizitätsgesellschaft m.b.H in Berlin-Weißensee

(source: unknown

The task of the locomotive motor control system is to smoothly increase the rotational speed of the "Bernhard" beacon from stand-still to exactly 2 rpm, and to accurately maintain that speed. The signals transmitted by the "Bernhard" beacon were printed aboard the aircraft with the "Bernhardine" Hellschreiber-printer. The compass-scale channel of this printer was synchronized to pulses transmitted by the beacon. As explained in the "Optical Encoder Disk" section (after Fig. 79), to make this synchronization scheme work, the allowed tolerance on the 2 rpm beacon speed was only ±0.2-0.3 % (p. 80 in ref. 181 and p. 8 & 18 in ref. 183). This small tolerance had to be met, independent of variations in the motor load (e.g., rail resistance around the circular track, wind load), and independent of amplitude and frequency variations of the 3-phase 50 Hz primary AC power. Note that towards the end of the war, the minimum frequency of the 50 Hz power grid was reduced to 43.3 Hz in the Central German block, and to 41 Hz in the Western German block (ref. 14).

One standard way to control and regulate motor speed is with a closed-loop control system. This requires tachometer feedback of the momentary speed, for comparison against the speed set-point. The amount of speed error (and possibly one or more of its time derivatives, and its integral) is then used to command the motor to speed up, or slow down. If the control system is properly configured and dimensioned ( = control laws/algorithms), and it has sufficient control authority ( = "power"), then the torque-vs-speed curve of such a drive system can be made to approach that of a synchronous motor (see Fig. 125 above, ref. 215). So, when constant speed is required - as is the case here - then why not go straight to an inherently synchronous AC motor drive and use an AC power source that has a sufficiently constant frequency? Yes, indeed, why not! Doesn't this basically just move the control system from the motor to the AC generator? Yes, indeed. But there it is easier to implement, as we shall see.

On the one hand, the locomotive drive system must operate with 3-phase primary AC power that has varying frequency and amplitude. On the other hand, DC power ( = rectified AC power) is required for several reasons. First of all, as explained in the "synchronous AC motors" section above, a synchronous motor is not self-starting. It must be brought close to synchronous speed by other means. Here: with DC traction motors. Also, the field winding of a synchronous AC motor is DC-powered. So, a 3-phase AC rectifier is required. And to complete the synchronous AC drive system, we need a "DC to fixed-frequency 3-phase AC" converter.

The next diagram illustrates the three main blocks of the "Bernhard" locomotive drive system:

Fig. 130: Top-level block diagram of the "Bernhard" motor drive system

(source: derived from ref. 189, 190)

The "Electrical power control, conversion & distribution" block has the following functions and associated control panels:

• Selection of the source of 3-phase 50 Hz (nominal) AC main power: the public power grid, or the local generator of the “Bernhard” station.
• Protection against over-voltage / over-current conditions of the primary AC power, and emergency shutdown. For the latter, there was a shutdown button located in the rotating cabin, in the round building below it, and outside the concrete ring.
• Conversion of the selected 3-phase 50 Hz AC power to DC power. This was done with a 6-anode Mercury Arc Rectifier described further below.
• Conversion of DC power into 3-phase AC power that has a constant frequency (unlike the primary AC power). This conversion was done with an electro-mechanical DC-AC inverter; in this case, a so-called "Conz" converter as described further below.
• Distribution of the AC and DC power. The selected 3-phase 50 Hz AC main power is distributed to the rectifier unit and to the rotating cabin (via a slip ring assembly in the round building below that cabin). The DC power from the rectifier unit is distributed to the DC-AC inverter and to the rotating cabin, Also see the "Electrical & signal distribution" section.

The motor drive control panel was located in the rotating cabin. It had separate controls for the three motor types (main drive DC, auxiliary drive DC with separate field winding, and synchronous AC). The block diagram in the next figure illustrates the power conversion and motor drive control functions with more detail:

Fig. 131: Electrical power and signal interconnections of the locomotive system

(source: derived from ref. 93, 189, 190; 3-phase 380 Vac, 50 Hz from the backup Diesel generator could replace power from the publick grid)

The three main-drive DC motors were controlled via a heavy-duty variable resistor arrangement in series with the field and armature windings of each motor. The controller and resistor bank ware located in the rotating cabin (see the hand wheel on the "Main Drive" control panel in Fig. 132 below). The four auxiliary-drive DC motors had a separate field winding that was wired to the "Auxiliary Drive" control panel. The field current was also controlled with a variable resistor, but with a much lower power rating than that of the main-drive motors.

Fig. 132: German engineer showing the locomotive control panel of Be-9 at Bredstedt to a member of the RAF-ADW

(source: Australian War Memorial photo SUK14636, public domain; ca. August 1945)

Since the synchronous AC motor provided inherent accurate speed control, there was no need for a closed-loop speed control system with a speed sensor. But there were two speed sensors: a tachometer in locomotive nr. 4 (with the synchronous AC motor), and a tachometer track on the optical encoder disk (measurement accuracy 0.1%) in the round building below the rotating cabin and superstructure. However, they were there for speed monitoring and alerting purposes only.

A rectifier is an electrical device that converts alternating current (AC) to direct current (DC). The device achieves this by allowing electrical current to flow through it in one direction only. A half-wave rectifier only passes either the positive or the negative half of a full AC voltage cycle. A full-wave rectifier passes the positive half cycle directly, and the negative half cycle with inversed polarity:

Fig. 134: Half-wave and full-wave rectification of single-phase and 3-phase sinusoidal AC voltages

(assumes ideal rectifiers/diodes (no forward voltage drop, etc.), no source reactance (typ. inductive), no output smoothing, and no load)

By 1930, the Mercury Arc Rectifier (MAR, a.k.a. Mercury Vapor Rectifier; D: "Quecksilberdampfgleichrichter", ref. 163A-163R) had become the best method for rectifying high power AC voltage in industrial applications and electrification of light and heavy railroad. The discovery of the unidirectional current-flow of an atmospheric arc between a mercury pool and a carbon electrode, goes back to 1882 (Jules-Célestin Jamin and his co-worker Georges Maneuvrier, ref. 163H). The MAR was invented around 1900. P. Cooper-Hewitt patented a glass-envelope MAR in 1902 (ref. 163J), based on his mercury vapor lamp. He marketed a metal-envelope MAR in 1908. In 1914, Irving Langmuir patented the concept of using a control-grid between the anode and the mercury-pool cathode (ref. 163K). This made it possible to arbitrarily choose the actual moment of arc initiation ( = switch-on via phase angle control, instead of it being determined by the primary power), and thereby vary the DC output. MARs can also be configured as an inverter instead of a rectifier, i.e., as a DC-to-AC converter.

MARs are a form of cold-cathode gas discharge tube. The rectifier consists of a glass or stainless steel vessel. The vessel is evacuated, or filled with inert gas. There is a pool of liquid mercury at the bottom of the vessel. This is the cathode. The vessel has one or more upward arms with a graphite anode. Clearly, a MAR is a static rectifier, as opposed to the mechanical rotary converters that preceded the MAR.

Full-wave rectification of a single-phase AC voltage requires two anodes. See Figure 135. For rectifying 3-phase AC power, the MAR must have a multiple of three anodes.

Fig. 135: left: Simplified principle diagram with a 2-anode MAR (left) and an active 3-anode MAR

Like a fluorescent lamp, a MAR must be started. Conduction is initiated by dipping the starting (igniting) electrode into the mercury pool, passing a high current, and retracting the electrode. This locally heats up the mercury (the "cathode spot" or "emission spot") and vaporizes it. This starts abundant emission of electrons by the mercury cathode. The mercury vapor is ionized by the stream of electrons that flows to the anode, and causes plasma discharge (arc) between the anode and the cathode. The mercury ions emit both visible blue-violet light, and a large amount of ultra-violet radiation. The light may have another color when the vessel is filled with an inert gas, e.g., pink as in Fig. 125 (probably argon). Evaporated mercury condenses on the cool wall of the vessel (hence the large bulbous form), and returns to the mercury pool at the bottom of the device. The plasma discharge stops as soon as the anode voltage drops below a certain level, or anode current is interrupted. Hence, for rectification of an AC voltage, ignition must be synchronized with that voltage. Alternatively, excitation electrodes may be used to maintain the plasma. The anode material does not emit electrons, so electrons can only flow from the cathode to the anode. I.e., current can only flow from the anode to the cathode. The ripple on the DC output current is smoothed with a series-inductance ("choke coil").

The heat of the mercury vapor must dissipate through the glass envelope in order to condense. To help keep the glass envelope cool enough, an electric fan is typically installed below the MAR (as clearly visible in Fig. 138 and the the right-hand photo of Fig. 140 below).

Fig. 136: Effect of cooling on voltage vs. current curve ( = losses & efficiency) of a glass MAR

(source: Fig. 66 in ref. 192)

For operating temperatures below 10 °C (50 °F), special measures must be taken to protect the MAR against damage from instable operation, and the attached transformers against current surges. This may be done with surge diverters and cathode heating. Ref. 161. Note that mercury freezes around -39 °C (-39 °F).

The MAR anodes are connected to AC power via a transformer. Each phase of the secondary side of this transformer has an inductance: inductance of the secondary winding itself, and transformed inductance of the primary transformer windings and the AC power line. Inductance prevents current (here: anode current) from varying instantly. Hence, when one anode becomes conductive and its current is building up, the current of the adjoining previously conductive anode anode is still dying down: for a short time, both anode arcs are active simultaneously! This cyclic "overlap" phenomenon effectively short-circuits the main transformer's secondary phases that are associated with these anodes. For rectifier circuits, the "overlap angle" (a.k.a. commutating angle) is the commutation time interval when when both devices conduct. This causes the rectifier's DC output wave to temporarily drop to the average of the overlapping sinusoidal transformer phase voltages, which significantly distorts the ripple (Fig. 25, 29, 33, 37 in ref. 163C).

Fig. 137: The effect of phase-overlap on the DC voltage wave

(overlap due to source reactance or load; source: Fig. 25 & 29 in ref. 163C)

The voltage drop during the overlap period is proportional to the output current, and is also a function of the number of anodes and of the transformer inductance. As load current is increased, the operating time (duty cycle) of each rectifier phase is increased, and more phases will overlap. In case of a short-circuit load, the significant voltage drop across the rectifier arcs and resistive losses in the transformer (and other parts of the rectifier circuit) prevent full-time overlap of all phases.

MARs can be constructed for hundreds of kilovolts and tens of thousands of amps. They have been used, and sometimes still are (!), as rectifiers for locomotives, radio transmitters, control of industrial motors, welding equipment, aluminum smelters, high-voltage DC power transmission, etc. Glass-bulb MAR designs are typically limited to 250 kW (500 volt, 500 amps). For higher power levels, a steel-tank version was developed around 1908. Siemens-Schuckert developed a compact double-wall water-cooled tank rectifier around 1920. Through the 1960s, high power (up to gigawatts, ref. 163L) high-voltage DC (HVDC) transmission line systems were designed with MAR rectifiers and inverters. MAR technology was succeeded by ignitrons and thyratrons (ref. 163F, 163S), and then solid-state Gate Turn-Off devices (GTOs, e.g., thyristors), ref. 163Q.

In May of 2015, I obtained the black & white photo shown below. It shows the large 6-anode MAR of the Be-10 "Bernhard" at Hundborg/Denmark. The MAR does not appear to have control-grid electrodes. It was installed in a typical MAR-cubicle, 2 m tall (≈ 6.7 ft). The required primary transformers were located in the adjacent MAR-control cabinet. Likewise, the choke-coil, though the DC-motors may have had enough inductance so as not to require such a DC-current smoothing coil.

Fig. 138: The rectifier system of Be-10 at Hundborg/Denmark

(sources: (left) ref. 223; (right) Fig. 31 in ref. 93A; the thick "disk" below the MAR is actually the spinning cooling fan)

The "Bernhard" MAR was made by the Gleichrichter Gesellschaft m.b.H company in Berlin, manufacturer of rectifiers since 1919. They were acquired by the Swiss company Brown-Boveri & Cie. (BBC) in 1921 (ref. 191). BBC became ABB (ASEA Brown Boveri), after a merger between BBC and ASEA AB of Sweden in 1988. The "Bernhard" MAR was a model S 18 T "Glasgleichrichterkolben" (glass bulb rectifier; pdf page 20 in ref. 189). The complete rectifier cubicle with all the equipment and controls was model DRA 300A / 220 V, also of the Gleichrichter G.m.b.H. (pdf page 20 in ref. 189). The model designator suggests that the MAR had a rating of 330 amps DC at 220 volt AC. The cubicle included the standard cooling fan as well as a bulb heater. The circuitry around this MAR included 17 fuses! Standard equipment of each "Bernhard" station included one spare MAR (pdf page 21 in ref.189).

Fig. 139: Label of a BBC MAR-cubicle with a MAR built by Gleichrichter G.m.b.H. in Berlin

(source: H.-T. Schmidt homepage; MAR for 220 volt 3-phase AC @ 75 amps, 100/140 volt DC @ 150 amps, 140/165 volt DC @ 65 amps)

Other German MAR manufacturers of the era included Siemens-Schuckert Werke, several German subsidiaries of BBC, and the AEG company Apparate-Werke Berlin-Treptow (AT) that was founded in 1928. A 6-anode MAR with a height of 90 cm (3 ft, about the size of the "Bernhard"-MAR) can typically handle as much as 350 amps at 650 volts. The photo on the left in Fig. 140 below shows a small MAR, rated for only 220 volt / 100 amps (22 kW), together with its transformers. This MAR was manufactured in the 1950s by Elektro-Apparate-Werke J.W. Stalin in Berlin-Treptow. This was the post-war continuation of AEG-AT in the Soviet-occupied part of Germany. The 6-anode MAR in the photo on the right is about 60 cm (2 ft) tall. It is part an elevator (lift) system in a defunct very large WW2 air-raid shelter 140 ft (43 m) below Belsize Park in London (ref. 243). This MAR is still operational in modern days (at least through the year 2014). The cubicle is similar to the "Bernhard" cubicle in Fig. 138.

Fig. 140: Example of MAR cubicles (left: 1950s, right: 1936)

(sources: collection of Technical University Freiberg(left); ©2000 Nick Catford Subterranea Brittanica (ref. 243); both used with permission)

The "Bernhard" MAR shown in Figure 128 has six anodes. For obvious reasons, these multi-arm MARs are sometimes referred to as "Krakengleichrichter" ("octopus-rectifiers"). Compared to a 3-arm MAR, a 6-arm MAR reduces the ripple in the rectified voltage. It also requires a more complicated main-transformer connection to AC power, e.g., a delta/double-star or star/double-star configuration. See pp. 18-24 in ref. 163B. Six-anodes is typically sufficient. Having more anodes does reduce the output ripple (which has a lowest harmonic frequency of six times the 50 or 60 Hz main power). However, the reduction when going from 6-phase to 12-phase rectification is less than half the reduction when going from 3-phase to 6-phase (Fig. 35 in ref. 163C for no-load conditions). Also, cost increases rapidly without increasing rectifier output, and the already low power factor (due to an undesirably large phase angle between AC supply voltage & current) is further reduced.

Fig. 141: A 6-anode Mercury Arc Rectifier with delta/double-star main-transformer connection to 3-phase AC power

(source: Figure 7.41 in ref. 163E)

When the motor voltage is reduced to slow down the motors (e.g., to brake to standstill), the large inertia of the "Bernhard" turntable will reverse the load torque of the motors. However, current can only flow through the MAR in one direction - it is a rectifier/diode. So, regenerative braking ( = using the motor as a generator and feeding the generated electricity back to a power grid) is not an option, and the motor cannot exert a braking torque. As a result, the armature voltage will increase to undesirably high levels. This is typically handled by switching-in a large dummy-load resistors across the armature of the motors, and dissipating the generated power as heat.

Here is a 36 sec video clip of a 6-anode MAR in action (WARNING - MAR systems are very loud!):

As stated above, a synchronous AC motor was used for obtaining and maintaining the required accurate locomotive speed. The frequency of the 3-phase AC power from the public power grid and the local backup generator was not sufficiently accurate. Hence, the fluctuating primary AC power had to be converted to constant-frequency 3-phase AC. Before the days of solid-state power electronics (1960s), the required power conversion was done by electro-mechanical means: an electric motor, an AC generator, and a closed-loop control system. The motor, generally referred to as the "prime mover", could be AC or DC. In the "Bernhard" system, a special DC-to-3-phase-AC inverter (D: "Umformer für Gleichstrom-Drehstrom") was used: a model NGJV So, 5/2 T built by the Conz company (sheet 16 in ref. 189). It was located in power generator building near the "Bernhard" beacon. The associated control panel had the following fuses: two for 350 V, 160 A, and three for 500 V, 35 A (per sheet 20 of ref. 189).

The Conz Elektricitäts-Gesellschaft mbH company was founded in 1887 by Gustav Conz. It was originally located in the Spaldingstraße in the southern German city of Ulm. The company moved to Hamburg in 1890, and acquired a plot of land in Hamburg/Altona-Bahrenfeld (Gasstraße 6-10) in 1911. An office building and two factory building were constructed here in 1912. Ref. 207. In 1962, Conz became a wholly-owned subsidiary of Deutsche Maschinenbau-Aktiengesellschaft (DEMAG) in Duisburg. The Hamburg plant was closed in 1995.

Fig. 142: advertizing of the Conz company from 1924

(source: Elektrotechnische Zeitung (ETZ), Nr. 16, 17 April 1924)

Fig. 143: advertizing of the Conz company from 1937 & 1940

A standard AC-generator has a field winding that is fed with DC power, and an armature winding that outputs the generated AC power. That is: a "singly-fed" generator. However, at the heart of a Conz converter is a high-power "doubly-fed AC generator" (D: "Doppeltgespeister Drehstromgenerator"). This is also called a "doubly-fed induction generator (DFIG) and "slip-ring generator" (D: "Schleifringläufergenerator"). Note: "doubly-fed" is somewhat of a misnomer, as it does not mean that the machine has two separate power inputs. Just that it has two sets of 3-phase connections. A DFIG is similar to the singly-fed generator, in that the stator outputs the generated AC power. However, now the rotor is excited with 3-phase AC power at variable frequency. The frequency of this AC excitation power is continuously adjusted to compensate for changes in the speed of the prime mover. The result is regulated 3-phase AC power (D: "geregelter Drehstrom") with a constant frequency. In modern times, DFIGs are widely used for large wind turbines, as solid-state inverters required for megawatt-scale wind turbines are larger and more expensive.

Fig. 144: singly-fed and doubly-fed 3-phase AC power generator

(the stator windings and DFIG rotor windings are shown in the standard WYE (a.k.a. "Y", star") configuration rather than Delta ("Δ"))

The next figure shows the principle diagram of the AC-AC Conz generator, as patented in 1937:

Fig. 145: Conz convertor - variable-to-fixed frequency AC-AC converter

(source: adapted from the 1937 Hans Gross / Conz patent nr. 692583; see ref. 188 for a list of related patents)

The green overlay in the figure above, shows the control loop for keeping the output frequency of the DFIG constant - independent of variations of the frequency and voltage of the primary AC power and of the output load: the 3-phase AC output power drives a synchronous AC motor. This motor is small (low power) compared to the DFIG and the primary mover. It drives a centrifugal governor. Based on the rpm, the governor adjusts a variable resistance. The resistance is placed in series with the field of a small DC motor, so as to change its speed. The DC motor drives a small 3-phase AC generator that excites the DFIG. Note that it is also possible to reverse the rotational direction of the three phases of the output. The efficiency of a Conz generator is higher than Ward-Leonard converter, especially under partial load or no load (idling).

The Conz generator configuration above uses an AC motor as prime mover, and a DC generator. This configuration can be simplified if a high-power DC source is available. This is the case in the "Bernhard" system, for powering the DC motors in the four locomotives. The DC-to-AC converter configuration is also mentioned in the Conz patent. So, a DC motor was used as prime mover, and the small DC generator was eliminated:

Fig. 146: Conz generator - DC-AC configuration as probably used in the "Bernhard" motor drive

(source: adapted from the 1937 Hans Gross / Conz patent nr. 69258; see ref. 188 for a list of related patents)

The output frequency of the "Bernhard" Conz-generator is not known. However, the title of the related 1937 Reichs patent is "Frequenzwandlergruppe zur Erzeugung konstanter Mittelfrequenz", i.e., "Frequency converter for generation of constant mid-frequency". In modern times, 400 - 2000 Hz mid-frequency AC is used in high-power application such as resistance welding. Ref. 10 (1946) states that the the "Bernhard" Conz-generator generated 50 Hz power.

The photo below was taken in the power supply bunker or barrack of Be-10 at Hundborg/Denmark. The Conz converter is on the right and is about 2 m tall. It is installed upright, probably due to the centrifugal governor. The cabinets on the left house the MAR rectifier and associated circuitry and controls.

Fig. 147: The Be-10 Hundborg installation - cabinets with the MAR and its controls, and the "Conz" generator

(photo courtesy Mike Dean, US National Archives & Records Adm. (NARA) image nr. 111 SC 269041; US gov't = no ©)

THE ROUND CENTRAL-SUPPORT BUILDING

At the center of the concrete ring of the "Bernhard" beacon, there is round brick building with a flat concrete roof:

Fig. 148: Concrete ring with central- support building

Fig. 149: Left-to-right - the round building of Be-7 at Arcachon, Be-14 at Aidlingen, and Be-3 at Le-Bois-Julien

(photo Le-Bois-Julien: ©2006 T. Oliviers, used with permission)

Fig. 150: The round building of Be-8 at Bergen/Schoorl (left), and Be-12 at Nevid/Plzeň

(sources: photo Be-8: ref. 127; Be-12: © Jacek Durych, used with permission)

This small building has two functions:

• Central support for the heavy rotating superstructure ( = cabin and antenna systems) of the beacon.
• Stationary equipment room (D: "feststehender Geräteraum").

The following items were installed in this equipment room below the rotating superstructure (see Figure 151):

• A 15-ring slip-ring assembly, suspended from the ceiling of the equipment room. Slip-rings allow electrical lines to traverse continuously rotating mechanical joints. The rotor of the assembly was driven by a shaft that descended through the ceiling of the equipment room (see Fig. 161) and rotated with the superstructure. The slip-rings passed electrical power and signals between the stationary equipment room and the rotating cabin above it.
• Optical encoder disk assembly, suspended from the slip-ring assembly and driven by the shaft of that assembly.
• Three audio tone modulators:
• a constant 1800 Hz audio tone for the pointer beam transmitter
• 2600 Hz audio tone pulses, representing the compass scale in Hellschreiber format, for the compass scale transmitter.
• 2600 Hz audio tone pulses, representing the command-message text string in Hellschreiber format, for the compass scale transmitter (when replacing transmission of the compass scale with the command-message).
• Two Hellschreiber printers (the same HS 120 printers as used in the aircraft), for printing:
• the signals transmitted by the beacon, as received by a remote receiver.
• the command-message text string, to verify it before actually transmitting it (only installed at a few beacons).
• A patch board and associated patch cord, for composing the up to 10 characters of the command-message (only installed at a few beacons).
• A power distribution and control panel. The panel also indicated the exact rotational speed of the optical disk (and, hence, of the beacon), as measured by a tachometer track on that disk.
• A switch for selecting the forward/reverse rotational direction of the beacon.
• An emergency shutdown button.

Fig. 151: The round building below the rotating superstructure - equipment and interconnections

(source: derived from ref. 189 and 190)

The photo below is the only one that I have of the inside of the equipment room:

Fig. 152: Equipment inside the round brick equipment room of the Bernhard installation at Hundborg

(source: Figure 30 in ref. 93A)

The 15-ring slip-ring assembly passed the following electrical power to the rotating cabin:

• DC, for the DC motors in the four locomotives. The associated fuses had a rating of 160 A / 500 V (ref. 189).
• 3-phase AC, constant frequency. Used for the synchronous AC motor in locomotive nr. 4. The associated fuses were rated at 80 A / 500 V.
• 3-phase AC, nominally 50 Hz (directly from the public power grid or a local backup generator). Used for the power supplies of the two transmitters, as well as general lighting and heating.

The slip-ring assembly passed the following other signals to and from the rotating cabin:

• Constant-tone audio modulation for the pointer beam transmitter.
• Hellschreiber tone-pulse audio modulation for the compass scale transmitter.
• Quadrant-keying ("Sektortastung") to both of the transmitters, by a switch contact that is actuated by a notched disk on the shaft of the slip-ring assembly. Most likely, this was (or could be) used to not transmit during the entire 360° rotation, but only in a specific limited directional range. This could be used to avoid detection of transmissions by Allied monitoring stations, e.g., in Britain. Beacons operating this way were referred to as "Sektorfunkfeuer" (p. 16 in ref. 181).
• Switch closure of the emergency shutdown button on the superstructure.

No photos are available of the slip-ring assembly. As an example, the photo below shows the slip-ring assembly of German "Panther" and "Tiger" tanks of the same era. Their slip-rings have a diameter of 12 cm (≈5 inch). There are four brass rings for electrical power (12 & 24 volt, 50 amps) and seven rings for communication and lighting.

Fig. 153 The slip-ring stack of Panzer V "Panther" and VI "Tiger" tanks

(source: ref. 145)

The standard "Bernhard" equipment included a full set of 52 spare tubes (valves), per sheet 19 & 20 in ref. 189 (pdf pp. 22, 23):

• For the modulators and transmitter-keying units:
• 10x RV12P2000, 1x RG12D60, 1x AZ12, 6x RV275, 4x RV335, 4x RG62, all made by Telefunken.
• 1x STV100/25Z and 1x STV280/80 made by Stabilovolt.
• For the measurement/monitoring equipment:
• 3x RV12P2000, 6x LV1, 6x RG12D60, 1x RGN4004, 3x RV275, 2x RV335, 2x RG62, all made by Telefunken.
• 4x STV150/15 and 1x STV280/80, made by Stabilovolt.

The walls of the building are made of brick. There are four windows of 1.2x1.2 m (4x4 ft), and a door. Whatever equipment was installed inside this building, it must have fitted through the door or a window. Floor-to-ceiling height inside the building is about 3 m (10 ft), so the floor is well below the base of the concrete ring. This is why there is a small trench and steps that lead down to the door.

The three diagrams below show the cross-section (with measured dimensions) of the concrete ring and round building of the "Bernhard" installation at Aidlingen/Venusberg, Arcachon, and Hundborg:

Fig. 154: Cross-section of the installation at Aidlingen/Venusberg

(based on the measurements that I took in June of 2012)

Fig. 155: Cross-section of the installation at Arcachon

(based on the measurements that I took in July of 2012)

Fig. 156: Cross-section of the Bernhard ring on Gåsbjerg hill at Hundborg

(based on ref. 115)

The concrete roof of the round building is supported by four columns, made of massive steel I-beams (H-beams, D: "Doppel T Träger"): the flanges are 30 cm (1 ft) wide and 24 mm (1") thick! The web of the beams is 32 cm (12½ inch) wide and 15 mm (0.6 inch) thick. So these columns have a cross-section of 30x37 cm. The columns are spaced evenly in the round wall. The roof-joists are made of the same heavy I-beams. Why would such a solid, heavy construction be necessary? The rotating superstructure weighed 120 metric tons (265 thousand lbs). Assuming the weight was distributed evenly between the four locomotives and the central support, the roof had to carry 120 / 5 = 24 metric tons (53 thousand lbs) statically!

The following diagrams show more details of the steel structure:

• 4 large steel I-beam columns, with end-plates. The flange of these vertical I-beams is 30 cm (1 ft) wide, and the height of the beams is 37 cm (1 ft 3")
• 4 large steel I-beam joists, with a joist-to-column brace and a triangular filler plate. The brace is a heavy steel plate (3 cm thick), as wide as the flanges of the columns and the joists. The joist and brace are mounted to the column with 8 bolts. The brace prevents the structure from racking ( = sideways swaying of the tops of the columns). The brace is mounted to the column at a 50° angle.
• 4 steel doubler-plates, to better transfer vertical forces on the joist to the column, and to distribute any bending force to both flanges of the columns. The doubler-plate is mounted onto the end-plate of the column with 8 bolts, and to the joist with eight bolts.
• 2 identical steel octagonal plates, to interconnect the four joists. Each joist is mounted to the two octagonal plates with 6 bolts. The plates have hole at the center.
• 4 small steel plates that form the sides of a box that is placed between the octagonal plates. The corners of the box are butted up against the web of the joists, but do not appear to be welded to them. The function of the box is unclear - possibly to prevent the center of the top octagonal plate from being pushed down, possibly they where used to pre-assemble the two octagonal plates.
• 4 small steel I-beams, connecting the joists above the braces. This makes the structure torsionally stiff. I found no sign that the columns are interconnected at the bottom.
• Numerous steel concrete reinforcement rods/bars ("rebar"), placed radially inside the concrete of the roof. The ends of the rods are curled back.

Fig. 157: The major elements of the steel support structure of the round building

(based on my measurements of the "Bernhard" at Aidlingen/Venusberg)

Fig. 158: Dimensions of the steel "skeleton" of the round building

(based on my measurements of the "Bernhard" at Aidlingen/Venusberg)

A doubler-plate reinforces the joint of each joist and the associated column:

Fig. 159: Dimensions of the column-to-joist doubler plate

(based on my measurements of the "Bernhard" at Aidlingen/Venusberg)

Fig. 160: Details of the steel support structure of the "Bernhard" at Aidlingen/Venusberg

Two heavy octagonal plates interconnect the four large I-beams joists at the center of the roof. One plate on top, one from below. There are two brackets on the bottom plate, for suspending equipment. The space between the brackets is about 55 cm (22 inch).

Fig. 161: The octagonal mounting plate against the ceiling - with mounting brackets to suspend equipment

Fig 162: Dimensions of the octagonal mounting plates and associated brackets

(based on my measurements of the "Bernhard" at Aidlingen/Venusberg)

Four smaller I-beams make the top of the structure torsionally stiffer, by bracing the four main joists:

Fig. 163: Top view of the steel support structure

(based on my measurements of the "Bernhard" at Aidlingen/Venusberg)

The next photo shows the remains of the steel structure (upside down), after removing the walls and collapsing the roof:

Fig. 164: The remains of the steel structure at Nevid, after destruction of the building in 2015

(source: © jdvlavicka)

Fig. 165: The remains of the steel structure at Nevid, after destruction of the building in 2015

(source: © jdvlavicka)

A very large ball bearing was installed in the middle of the roof:

Fig. 166: The round building with the raceway of a large ball bearing in the middle of the roof

(Be-12 at Nevid/Plzeň; source: © Jacek Durych, used with permission)

It had an outer diameter of about 40 cm (≈16 inch). The ball bearing held a cylindrical tube, that rotated with the antenna system and the cabin. The bottom of this tube has a flange, for connecting to equipment that rotated with the tube. The tube had a diameter of about 14 cm (5½ inch).

Fig. 167: Tubular shaft descending through the roof of Be-6 at Marlemont and Be-10 at Hundborg

(source Hundborg photo: www.gyges.dk, used with permission; note the original wiring)

A small turntable is installed on top of the ball bearing, and the tube is attached to it from below:

Fig. 168: small turntable on top of the shaft

(Be-6 at Marlemont; note the large mounting bolts inserted into the turntable from below)

SUPPLY OF ELECTRICAL POWER

The "Bernhard" installation had several consumers of electrical power:

• Four electric locomotives. Reportedly one of the motor types was a low-rpm model, rated 10 kW (ref. 99). Let's assume all eight locomotive motors (two types of DC motor and one synchronous AC motor) had this rating. This would add up to 80 kW in total.
• Two model AS 4 transmitters, each with an output power of 500 watt, or 1 kW total. Each AS 4 had a power supply model NA 500, with separate inputs for 220 and 380 volt 50 Hz 3-phase AC ("Drehstrom"), rated at 5 kVA. Ref 39C (p. 7) states that each NA 500 was normally powered by a standard heavy motor-generator model "A" ("schwerer Maschinensatz A"), rated at 12 kVA (see Fig. 163 below), or the public power grid. Either way, the power source was loaded with 5 kW. I.e., ten times the transmitter output power, and 10 kW total for the two transmitters combined.
• Miscellaneous items in the equipment room (three modulators, two printers, three projector lights in the optical disk assembly) - let's conservatively assume 1 kW.
• Heating and lighting in the rotating cabin and equipment room below it, as well as in the ancillary building) - let's assume 4 kW.

Adding up the four types of electrical loads, we arrive at an estimated total load of 80 + 10 + 5 = 85 kW. To translate this to the required power from an AC source, we have to assume a worst-case phase angle φ between the generated voltage and current. For a reasonable cos(φ) = 0.8, the AC-power source would have to be dimensioned for at least 85 / 0.8 ≈ 106 kVA.

The table below shows the specified power supply for a number of Wehrmacht transmitters of the same era, including other beacon transmitters. The power supply outputs are all dimensioned for at least four times the transmitter output power.

Fig. 169: Specified power supply rating for a number of Wehrmacht transmitters

(based on various data sheets)

To be able to operate independently from the local public power grid, the "Bernhard" installation had its own local power generator, driven by a combustion engine (diesel or gasoline/petrol). Ref. 183 (pdf p. 18) states that "Bernhard" backup generator was powered by a diesel engine ("Notstrom-Diesel"). Ref. 180 implies that "Bernhard" station Be-0 near Trebbin had a 120 kVA backup diesel generator. Note that this station was also a test site, and probably had more ancillary buildings (labs, offices, kitchen, living quarters) with associated loads than a standard "Bernhard" station. Ref. 10 (§8) states that backup power was provided by a 160 kVA 3-phase 380 volt generator, driven by a 200 horse power (HP) diesel engine. I.e., 2.4 HP per kVA.

Based on the local situation (access to the local public power grid), the "Bernhard" installation typically included a high-voltage bunker ("Hochspannungsbunker"), e.g., ref. 99. It contained one or more transformers, to connect to the multi-phase regional Hochspannungsnetz (high voltage public power grid, 110-220 kV in Germany), or to the local Mittelspannungsnetz (6-60 kV, typically 10 or 20 kV). The local Niederspannungsnetz (several km) carried less than 1 kV. Incidentally, towards the end of the war, the minimum frequency of the 50 Hz power grid was reduced to 43.3 Hz in the Central German block, and 41 Hz in the Western German block. Ref. 14.

Fig. 170: The two sources of electrical power of the "Bernhard" installation

For comparison, next table lists the horse power of the engine of a number of Wehrmacht electrical power generators ("Maschinensätze") for transmitters, various models of Flak-Scheinwerfer (search-lights for Anti Aircraft gun installations; ref. 152A, 152B) and even of a field bakery. This ranges roughly from 1.5 - 3 HP/kVA.

Fig. 171: Engine power for a number of Wehrmacht generators

The photo below shows the 110 kVA emergency backup generator of the "Goliath" Kriegsmarine transmitter station for world-wide communication to submerged submarines (incl. via Hellschreiber). It has a 150 HP diesel engine, ref. 218 (p. 188). That is, 1.4 HP/kVA. Note that the main generator, for the 1 megawatt (!) "Goliath" transmitter, had a power of 1800 kVA and was driven by a 2110 HP diesel engine! That is, about 1.2 kVA/HP.

Fig. 172: Example of a 110 kVA, 3-phase 380 VAC diesel generator

(source: "Der Goliath in Bildern - Fotos vor 1946/47" web page)

Ref. 103 suggests that the generator(s) of the "Bernhard" station Be-14 at Aidlingen/Venusberg were powered by two engines that came from high-speed patrol boats of the French navy. However, the French navy's "vedette rapide" boats were standard British-built "Fairmile" models. The smallest model had two Hall-Scott Defender V12 gasoline (UK: petrol) engines of 650 BHP each. The larger "A" model had three 600 HP engines. Clearly a single engine would have been able to supply more power than needed for a Bernhard installation, even if power was also generated for the local FLAK unit and its search-light(s). On the other hand, this Be-14 station was built towards the end of the war, when materials other than rocks and stone were in increasingly short supply. A strong engine that costs nothing, is better than a correctly sized engine that is not available... There are two stone buildings near the ring of Be-14. In the middle of one of them, there is a rectangular concrete slab that measures 1.4 x 3.25 meters (4.6x10.7 ft). The slab has 6 pairs of shallow round dimples, 8 and 10 cm in diameter. The purpose of the slab in unknown. Possibly the dimples corresponded to mounting feet of a motor-generator, such as shown in the photo above.

Fig. 173: A concrete slab in the middle of an ancillary building of Be-13 at Aidlingen/Venusberg

Below one of the windows of the round building of the "Bernhard" at Arcachon, there is an old 4-prong junction box with triangular shape. Near this box, several old cables enter the building through the wall, just above floor level. This appears to be where 3-phase AC-power entered from the generator in a nearby building.

Fig. 174: Large 4-prong (3-phase) junction box on inside wall of the round building of Be-7 at Arcachon

PATENTS

Below is a listing of patents related to the "Bernhard" system.

Here are some ancillary patents:

Patent office abbreviation: RP = Reichspatentamt (Patent Office of the Reich), DP = deutsches Patentamt (German Patent Office)
Patent source: DEPATISnet

UNKNOWN / UNCONFIRMED / UNCLEAR ASPECTS

• The purpose of FuSAn725, with 4 or 5 kW transmitters instead of 0.5 kW? Range increase, interference-proofness?
• Open-wire feedline between the dipoles: characteristic impedance (spacing between the wires, wire diameter)?
• Were the rails continuously welded rail or jointed?
• Purpose/content of the four corner-sheds? Dead-weight?
• Purpose of two different types of DC motors per locomotive?
• Were both bogies of each locomotive motor-driven, and one or both axes of each driven bogie?
• Which company was the manufacturer of the locomotives?
• Purpose of dimples in the top of several of the concrete rings, between the rail ties/shoes?
• Purpose of a box with 5 kg of graphite (powder?) that was part of the standard equipment (sheet 20, ref. 189)?
• Why was a special Telefunken crystal module needed in the AS 4 transmitters (improve the frequency accuracy/stability?).
• Purpose of the remote tachometer in Locomotive nr. 4 (going to the rotating cabin), in addition to the tachometer track of the optical disk (in the round equipment building below the rotating cabin)?
• Frequency of the accurately regulated 3-phase AC (50 Hz?), and the number of rotor poles of the synchronous AC motor of locomotive nr. 4?

REFERENCES

• Ref. 2: pages from the reknowned books and other documents by Fritz Trenkle
• Ref. 2A: "Die deutschen Funkführungsverfahren bis 1945" ["The German radio guidance systems through 1945"], Fritz Trenkle, Dr. Alfred Hüthig Verlag, 1987, ISBN 3778516477, 215 pp.
• Ref. 2A1: p. 149 (X-Uhr / X-system clock).
• Ref. 2A2: pp. 76-110, 224.
• Ref. 2B: "Die deutschen Funk-Navigations- und Funk-Führungsverfahren bis 1945" ["The German radio navigation & guidance procedures through 1945"], Fritz Trenkle, Motorbuch Verlag, 1995, 208 pp., ISBN-10: 3879436150.
• pp. 62, 94-102.
• Ref. 2C: "Bordfunkgeräte - vom Funkensender zum Bordradar" ["On board radio equipment - from spark transmitter to radar"], Fritz Trenkle, Bernard und Graefe Verlag (publ.), 1986, 283 pp., ISBN 3-7637-5289-7. [table of contents]
• Ref. 2C1: p. 61-63 - "Kommandoübertragungszusätze" ["Command uplink accessories"].
• Ref. 2C2: p. 83-95 - "Eigenpeil- und Zielflug-Verfahren - LW-MW-Peil und Zielfluggeräte" ["RDF and reverse-RDF systems - LW/MW RDF & approach equipment"]
• Ref. 2C3: pp. 97-118 - "Leitstrahl-Verfahren" ["Guidance-beam systems"].
• Ref. 2C4: p. 108 - photo "Große Knickebein Anlage bei Kleve", ["Large Knickebein installation near Cleves"; note: incorrectly identified by Trenkle as station K4 at Kleve, instead of K2 at Bredstedt].
• Ref. 2C5: pp. 119-133 - "Drehfunkfeuer-Verfahren - LW, KW, UKW, DMW, bis 1945" ["Rotating-beam beacon systems, Longwave"].
• Ref. 2C6: pp. 134-140 - "Hyperbel-Navigations-Verfahren" ["Hyperbolic navigation systems"]
• Ref. 2C7: pp. 141-150 - "Entfernungsmeß-Verfahren" ["Distance measuring systems"]
• Ref. 2C8: pp. 198-200 - "Kenngeräte (Bord-Transponder)" [FuG 25 "Zwilling", FuG25a "Erstling"]
• Ref. 2D: "Versuch einer Zusammenstellung deutscher Funkgeräte 1939 ... 1945 LUFTWAFFE / HEER / MARINE (ca .1200 Geräte)" ["Attempt at a compilation of German radio equipment 1939 ... 1945 Air Force / Army / Navy (ca. 1200 equipment items)"], Wolfgang "Fritz" Trenkle, Issue VI.60 (1960), 100 pp. [file size: 38 MB]. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, Signatur/file nr. RL 2-V/211, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 5: "Instruments of Darkness: The History of Electronic Warfare, 1939-1945", new ed., Alfred Price, Greenhill Books, 2005, 272 pp., ISBN-10: 1853676160; original edition: William Kimber and Co., Ltd, 1967. See note 1
• Ref. 5A: pp. 236-237; Same as pp. 274-275 in the excellent German translation: "Herrschaft über die Nacht: Spionen jagen Radar", Alfred Price, publ.: Bertelsmann Sachbuchverlag Reinhard Mohn, 1968, 304 pp., ASIN B0000BT35X.
• Ref. 5B: p. 82 - second of sixteen photo pages.
• Ref. 6: Transcribed reports from the British Air Ministry, Assistant Director of Intelligence (Prisoner Interrogation),  A.D.I. (K) (a.k.a. "Felkin Reports", after their author). Source: The National Archives of the UK, ref. AIR40/2875 and 2876. Retrieved from www.cdvandt.org.
• Ref. 6A: §19-23 in "Some further notes on G.A.F. Pathfinder procedure" ["EGON" procedure, new EGON procedure, Berhardiner Gerät, Erika Gerät, Y-gerät, "X" Clock, Knickebein jamming],  S.D. Felkin, A.D.I.(K) Report No. 187/1944, 25 April 1944, 5 pp.
• Ref. 6B: §57-59 in "G.A.F. night fighters - R.A.F. Bomber Command countermeasures and their influence on German night fighter tactics" [transcript], S.D. Felkin, A.D.I.(K) Report No. 599/1944, 2 November 1944, 16 pp.
• Ref. 6C: G.A.F. Night Fighters - Recent Developments in German Night Fighting",  S.D. Felkin, A.D.I. (K) Report No. 125/1945, January 1945, 18 pp.
• Ref. 6D: "The GAF (German Air Force) Signals Organisation in the War" [incl. X-System, X-beam, Knickebein, Y-System (Benito), Zyklop/Cyclop, Erika, Sonne beacons in Spain, radar, FuG25/25A, IFF, Panorama, Centimetre Wave R&D, Egon, Gee, H2S, Berlin-Gerät, Kammhuber night fighting, Window, Wilde Sau, HS293], Samuel Denys Felkin, A.D.I.(K) Report No. 334/1945, 1 July 1945, 27 pp.
• Ref. 6E: "Equipment of a Y-Site" [Berta I, Berta II, S16B, Sadir 80/100, Heinrich I (Peiler, D/F), Heinrich III, FuG 16ZE, FuG16ZY], S.D. Felkin, A.D.I.(K) Report No. 527B/1944, 25 Sept 1944, 13 pp.
• Ref. 6F: "Radio and Radar Equipment in the Luftwaffe- I. Blind Landing and Airborne Communications Equipment" [report of interrogations of General Martini and other PoW's; topics: LFF, JLFF, Fu Bl 2, AWG 1, FuG 10 P, FuGe 16, FuGe 17, FuGe 18, FuGe 15, FuGe 24, FuGe 29], S.D. Felkin, A.D.I.(K) Report No. 343/1945, 1 July 1945, 6 pp.
• Ref. 6G: "Radio and radar equipment in the Luftwaffe - II: Navigational aids" [D/F loop equipment, PeGe 6, FuG 141, FuG 142, FuG145; homing beacons: Schwanboje, Biene; beam systems: Zyklop, Sonne, Mond, Stern, Dora, Komet, Erika, Bernhardine, Hermine; Pulse systems: Ingolstadt, Truhe, Baldur, Baldur-Truhe, Baldur-Bernhardine; Ground control systems: Benito = "Y", Egon, Nachtlicht, Nachtfee, Barbara, Barbarossa, Rübezahl], S.D. Felkin, A.D.I. (K) Report No. 357/1945, 25 April 1944, 18 pp.
• Ref. 6H: "Radio and radar equipment in the Luftwaffe - III: Electric altimeters" [FuG 101A, FuG 102, FuG 103, FuG 104], S.D. Felkin, A.D.I. (K) Report No. 362/1945, 27 July 1945, 3 pp.
• Ref. 6J: "Fighter defence of Germany - Control of fighters by the "Y" Procedure" [Samuel Denys Felkin, A.D.I.(K) Report No. 525/1944, 14 pp.
• Ref. 6K: "German knowledge of 'OBOE'", [transcript], S.D. Felkin, A.D.I. (K) Report No. 318/1944, 29 Juni 1944, 11 pp.
• Ref. 6L: "Further Report on the Crew of the Ju.88 8-3 Z6 + FH of 1/K.G.66) shot down by A.A. 5 miles N.W. of Alost, on 23rd January 1945.(Previous A.D.I.(K) Report No.142/1945)" [incl. special navigation aids: EGON, "Y" procedure, "Y" clock, new "X" procedure = "Y" + EGON, FuG 28, Y-Clock (CRT), FuG 17, FuG 25A, FuG 217, Ju-88], S.D. Felkin, A.D.I. (K) Report No. 175/1945, 19 February 1945, 13 pp.
• Ref. 7: "Beiträge der Firma Siemens zur Flugsicherungstechnik und Luftfahrt-Elektronik in den Jahren 1930 bis 1945 (Teil 1 & 2)", H.J. Zetzmann, in "Frequenz - Zeitschrift für Schwingungs- und Schwachstromtechnik"
• Ref. 7A: Part 1: Vol. 9, Nr. 10, October 1955, pp. 351-360. [Wassermann radar FuMG 402, Wellenschieber, Jagdschloß / FuMH 404, PPI, Freya FuMG 41, Würzburg Riese]
• Ref. 7B: Part 2 (pp. 387, 388, 392): Vol. 9, Nr. 11, November 1955, pp. 386-395. [RDF antennas for aircraft, Bernhard/Berhardine, transponder DME, D 2002, Kurskoppler, autopilot, FuG 135 Boden-Bord Kommando-Übertragungsgerät]
• Ref. 10: "The German Bernhard Aircraft Navigational System", S/Ldr. G.W. Calvert, AIR 40/2162, Air Minsitry, Directorate of Intelligence (D. of I.), Air Intelligence, Technical, A.I.2(g), Report No. 1834, 20 February 1946, 30 pp. Item is in the collection of The National Archives; material with UK Crown Copyright, used in accordance with the Open Government License [pdf].
• Ref. 13: p. 4.05 and 4.09 in "Japanese Electronics", OPNAV-16-VP101, Photographic Intelligence - Report 1", U.S. Naval Photographic Intelligence Center, January 1945, 166 pp. [33 MB]
• Ref. 14: summary item 27 in "The German Wartime Electricity Supply - Conditions, Developments, Trends", British Intelligence Objectives Sub-committee (BIOS), Final Report 342, Item No. 33, 28 selected pages. Source: www.cdvandt.org
• Ref. 15: "Beschreibung und Betriebsvorschrift für Funk-Navigationsanlage FuG 120" ["Description and Operating Instructions for Radio-Navigation System FuG 120" = "Bernhardine"], Telefunken Gesell. für drahtlose Telegraphie m.b.H., document FN-T-GB Nr. 1932, December 1944, 43 pp. [File size: 66 MB - a good-but-lower resoluton file is here 26 MB]
• Ref. 15A: higher quality version of pp. 16-20 (equipment photos); source: corporate archives of DTM Berlin, file nr. I.2.060C-00666.
• Ref. 20: pp. 59-63 of "Richt- und Drehfunkfeuer" [Directional and rotating radio beacons], Chapter 3 of “Leitfaden der Funkortung: Eine systematische Zusammenstellung der Verfahren und Anlagen der Funkortung“ [Guide to radio location: a systematic survey of radio locationmethods and installations], vol. 1 of "Lehrbücherei der Funkortung", Walter Stanner, 4^th ed., Deutsche RADAR-Verlagsgesellschaft m.b.H., 1957, 160 pp.
• Ref. 28: ITU conference 1938; "Propositions transmises au bureau de l'union, pour être soumises à la conference" [proposals to be submitted to the ITU conference], Vol. 1 of "Documents de la Conférence internationale des radiocommunications di Caire (1938)", International Telecommunications Union (ITU), Bern; no English version available; source: ITU
• Ref. 28A: pp. 218, 219: proposal nr 392 R by C.I.N.A - "Considérations générales sur la largeur de bande des émetteurs de t.s.f. modulés par signaux Siemens-Hell" [general considerations about the bandwidth of radio transmitters that are modulated with Siemens-Hell signals]; at 5 chars/sec (punch tape operation), the 12-line Hell-font with a shortest pulse of 2 msec and shortest pause of 3.12 msec has a shortest cycle of 5.12 msec, hence a max cycle rate of 195 Hz, and 97.5 Hz with manual/keyboard operation at 2.5 chars/sec. Tests by Siemens-Halske, Cable & Wireless (UK), and the German Central Postal Authority (R.P.Z) have concluded that a applying a low-pass filter with a corner frequency of 230 Hz at the transmitter is sufficient, and results in 390 Hz occupied bandwidth.
• Ref. 29: "Bandbreitenfragen bei Anwendung der Siemens-Hell-Fernschreibtechnik" [signal bandwidth issues with A2 and A3 modulation], Rudolf Zimmermann, 7 pp., Technische Mitteilungen des Fernmeldewerks, Siemens & Halske A.G., Wernerwerk, Abteilung für Telegrafengerät, Berlin-Siemensstadt, May 1940, SH 7998, 1. 8. 40. T T1.
• Ref. 34: "Most Secret War", R.V. Jones, Hamish Hamilton, 1978, 576 pp. [file size: 53 MB] See note 1
• Ref. 72: "Funk-Landegerät Fu Bl 2 Geräte-handbuch" [EBL 2, EBl 3], D.(Luft)T.4058, February 1943, 120 pp. Source: www.cdvandt.org.
• Ref. 91: pp. 60-69 in "Mémoires sans concessions", Yves Rocard, Grasset, 1988, 302 pp., ISBN-10: 2246411211.
• Ref. 92: "Yves Rocard, père de la physique française d'après-guerre" ["Yves Rocard - father of post-war physics in France"], Emmanuel Grenier, in "Fusion", No. 86, May/June 2001, pp. 30-44.
• Ref. 93: pp. 115-117 in "The High-Frequency War - A Survey of German Electronic Development", E.S. Henning, HQ Air Materiel Command (AFMC), Wright Field, Dayton/OH, Summary report No. F-SU-1109-ND, 4 June 1946 (US Gov't, hence no copyright).  [file size: 225 MB; a lower-resolution version is here, 56 MB]
• Ref. 99 "Völlig in Vergessenheit geraten: Funkanlage bei Buke", Hans-Walter Wichert, in "Die Warte - Heimatzeitschrift für die Kreise Paderborn und Höxter", Nr. 24, December 1979, pp. 14-15, ISSN 0939-8686 (courtesy Mr. R. Gellhaus and H.-W. Wichert)
• Ref. 103: "Aidlingen Venusberg", web-page of Forschungsgruppe Untertage e.V. [pdf]  Also part of "Pressebericht Tageswanderung zum Venusberg", Reiner Schopf, p. 28 in "Stadt Holzerlingen Nachrichtenblatt", 1 August 2014.
• Ref. 115: Drawing of the cross-section of the Bernhard at Hundborg/Gåsbjerg hill, Jens Salmonson, 1982, source: Hundborg Lokalhistoriske Arkiv, used with permission.
• Ref. 127: "Vliegveld Bergen NH 1938-1940", J.H. Schuurman, A.W. de Poel (ed.), Uitgeverij De Coogh, 2001, 336 pp., ISBN 9075440049
• Ref. 128: personal correspondence with Y. Rose, December 2013 - April 2014
• Ref. 129: "Trzebnica *Raszów*", source: RadioPolska website, accessed 2014.
• Ref. 135: Section 4.2 and 4.3 in "Antennbuch", Karl Rothammel (DM2ABK), Deutscher Militär Verlag, 7^th edition, 1969, 593 pp.
• Ref. 136: "Die Antennen", Section I in "Fibel FuG 200 für den Funkwart und Bordfunkmechaniker" 2^nd ed., April 1944, 53 pp.
• Ref. 137: "Ausstrahlung, Ausbreitung und Aufnahme Elektromagnetischer Wellen", Ludwig Bergmann, Hans Lassen, Vol. 2 of "Lehrbuch der drahtlosen Nachrichtentechnik" ["Textbook of wireless communication"], Nicolai von Korshenewsky (ed.), Wilhelm T. Runge (ed.), Springer -Verlag (publ.), 1940, 286 pp. Source: libarch.nmu.org, retrieved 18 May 2020. [file size: 22 MB]
• Ref. 137A: "Die Dipolreihe, Dipolgruppe, und Dipolebene" ["The dipole row, dipole array, dipole plane"], pp. 62-73.
• Ref. 137B: "Richtantennen für Leitstrahlanordungen (Funkbaken)" ["Directional antennas for guide-beams (radio beacons)"], p. 97-98 in Chapter II.
• Ref. 138: p. 15-20 in "Richtverbindungsgeräte", Vol. 2 of "Richtverbindungen", Riv-2, Luftnachrichtenschule Halle (Saale), 1^st ed., September 1942
• Ref. 139: array antennas
• Ref. 139A: "High-frequency Antennas" in "Radio Antenna Engineering", Edmund A. Laport, McGraw-Hill Book Co., 1952, 560 pp., [pdf 30 MB] © Creative Commons License; also as free online e-Book here.
• Ref. 139B: "The Linear Broadside Array", Chapter 4 in "Array and Phased Array Antenna Basics", Hubregt J. Visser, John Wiley & Sons, 2005, 378 pp.
• Ref. 139B: "Reflective Array Antenna", Wikipedia [pdf]
• Ref. 139C: "Phased Array Handbook", Robert J. Mailloux, 2^nd ed., Artech House, 2005, 515 pp.
• Ref. 139D: "Wire Array Antennas", Chapter 8 in "Antenna Toolkit", Joseph J. Carr (K4IPV), 2^nd ed., Newnes, 2001, 263 pp.
• Ref. 139E: "Multi-Element Arrays", Chapter 8 in "The ARRL Antenna Handbook", 21^st ed., 2007, 976 pp.
• Ref. 139F: "Antenna arrays", Mississippi State University ECE4990 course notes nr. 6, Patrick Donohoe, 2014 [pdf]
• Ref. 139G: "Array Antennas", Chapter 20 in "Electromagnetic Waves and Antennas", Sophocles J. Orfanidis, 2014 [pdf]
• Ref. 139H: "Arrays of Dipoles and of Apertures", Chapter 11 in "Antennas", John D. Kraus, 2^nd ed., McGraw-Hill Book Co., 1988, 924 pp.
• Ref. 139J: p. 170 in "Über die Richtcharakteristik von in einer Ebene angeordneten Strahlern" [About the directivity of planar arrays], H. Stenzel, in "Elektrische Nachrichten-Technik" (ENT), Vol. 6, Nr. 5, May 1929, pp. 165-181; source: cdvandt.org
• Ref. 139K: "Ausgewählte Fragen über Theorie und technik von Antennen - Zusammengestellt aus Vorträgen anläßlich der Arbeitsbesprechung "Antennen" veranstalltet vom Generalbevollmächtigten für technische Nachrichtenmittel in Verbindung mit dem Vierjahresplan-Institut für Schwingungsforschung", 24-26 March 1943, Vol. 2, Zentrale für wissenschaftliches Berichtewesen der Luftfahrtforschung des Generalluftzeugmeisters (ZWB), Berlin-Adlershof; source: cdvandt.org
• Ref. 139K1: pp. 134-144, "Grundsätzliches über Richtantennen" [basics of directional antennas], W. Moser
• Ref. 139K2: pp. 45-63, "Der Einfluss der Reflektorwand auf die Ortskurve von Breitband - Rohrdipolen" [Effect of a reflector surface on the impedance of thick broadband dipoles], G. Dieckmann
• Ref. 139K3: pp. 5-29, "Grundlagen der Breitbandantennenanlagen" [basics of broad-band antenna systems], O. Zinke
• Ref. 139K4: pp. 223-231, "Neue Erfahrungen der Deutschen Reichspost in der Speisung von Antennen für lange und kurze Wellen" [new experiences of the with feeding long-wave & shortwave antennas], Ellrodt
• Ref. 140: "Zum 75 jährigen Bestehen der Firma Hein, Lehmann & Co., A.-G., Düsseldorf. 1888 - 1963", Hein, Lehmann & Co., 1963, 123 pp.
• Ref. 141: "FuSAn, Peil- und Funkanlagen", Harry Lippmann, 2007. Source: Deutsches Atlantikwall-Archiv. [pdf]
• Ref. 142: "Bandbreitenfragen bei Anwendung der Siemens-Hell-Fernschreibtechnik" [signal bandwidth issues with A2 and A3 modulation], Rudolf Zimmermann, 7 pp., Technische Mitteilungen des Fernmeldewerks, Siemens & Halske A.G., Wernerwerk, Abteilung für Telegrafengerät, Berlin-Siemensstadt, May 1940, SH 7998, 1. 8. 40. T T1.
• Ref. 143: to be allocated.
• Ref. 145: "Schleifringübertrager allgemein", pp. 166-169 in "Funk- und Bordsprechanlagen in Panzerfahrzeugen", Vol. 3 of "Die deutschen Funknachrichtenanlagen bis 1945", H.-J. Ellissen, Marketing & Technik Verlag, 1991, 240 pp., ISBN 3-928388-01-0
• Ref. 146: p. 3 in "Instruktion för Hellskriv-apparat" [in Swedish], Kungl. Arméförvaltningens Tygavdelning, SiB/040:3045, 13 July 1945, 40 pp. (courtesy Willi Reppel, SM6OMH)
• Ref. 147: "High-Power Crystal Set", Walter B. Ford, in "Popular Electronics", August 1960, pp. 63-65
• Ref. 148: "Empfangsversuche mit dem Sirutor", F. Nitturra, in "Funkschau", Vol. 13, Nr. 2, February 1940, p. 29
• Ref. 149: "Anregungen zum Detektorempfang", H.-A. Dennig, in "Funkschau", Vol. 16, Heft 8/9, August/September 1943, p. 80
• Ref. 150: "Crystal Set Analysis", Berthold Bosch (DK6YY), March 2002, 15 pp. [pdf]
• Ref. 152: Luftwaffe search-lights
• Ref. 152A: "Scheinwerfer der deutschen Luftwaffe", C. Mattner, in "Zeitschrift des Vereines deutscher Ingenieure", Bd. 18, Nr. 33, 14 August 1937, pp. 953-955
• Ref. 152B: "pp. 136-139 in "Der Flakscheinwerferkanonier", Ernst Schlachtmann, "Handbücher der Luftwaffe - Der Dienstunterricht in der Flakartillerie - Ausgabe für den Flakscheinwerferkanonier", 3^rd ed., Verlag E.S. Mittler & Sohn, 1939, 155 pp.
• Ref. 154: "Das Mädchen, die Katze und der Amboss - Auszüge aus '100 Jahre Ziehl-Abegg'", source: industrieanzeiger.de
• Ref. 155: p. 16 in "PLAKAT - Gedanke und Kunst: Einiges aus der Plakat-Praxis", Propaganda Stuttgart, 1912, 63 pp.
• Ref. 156: "The Science of Locomotion - Why Rail Has 20X Energy Saving Advantage Over Rubber Tire Road Vehicles". Source: Brooklyn Historic Railway Association.
• Ref. 157: "Railway Engineering", Karim H. Al Helo, Department of Building Construction Engineering, University of Technology, Iraq, 64 pp.
• Ref. 158: "Adhesion in the wheel-rail contact under contaminated conditions", Yi Zhu, Licentiate thesis at the Royal Institute of Technology, Stockholm/Sweden, 2011, 100 pp. [pdf]
• Ref. 159: slide 24 in "Railroad Transportation Energy Efficiency", C. Barkan, University of Illinois at Urbana-Champaign, 2007, 61 slides [pdf]
• Ref. 160: "Some graphical solutions to electric railway problems", A.M. Buck, in "University of Illinois Bulletin", Vol. XIII, No. 47, 1916, 40 pp.
• Ref. 161: "The characteristics and control of rectifier-motor variable speed drives" [mercury-arc rectifiers], P. Bingley, in "Proc. of the IEE Part II: Power Engineering", Vol. 99, Issue 69, June 1052, pp. 189-202 ( Author's reply to discussion: pp. 205-206)
• Ref. 162: Ward-Leonard drive systems
• Ref. 162A: "Ward Leonard drives 75 years of development", K.A. Yeomans, IEEE Electronics and Power, Vol. 14, Nr. 4, pp. 144-148
• Ref. 162B: "Electrical Transmission of Power", H. Ward Leonard, United States Patent Office, Patent No. 463,802 [pdf]
• Ref. 162C: "A new system of electric propulsion", Harry Ward Leonard, in "Transactions of the American Institute of Electrical Engineers (AIEE)", Vol. IX, Issue 1, January 1892, pp. 566-577
• Ref. 162D: "Volts vs. Ohms; Speed Regulation of Electric Motors", Harry Ward Leonard, in "Transactions of the American Institute of Electrical Engineers (AIEE)", Vol. XIII, January 1986, pp. 373-386
• Ref. 162E: "Ward Leonard System", pp. 445-446 in "Synchros and Servomechanisms", Chapter 21 in "Basic Electricity", United States. Dept. of the Army, Naval Education and Training Program Development Center, FM 55-506-1, 22 April 1977, 490 pp.
• Ref. 162F: "Leonard Doppel-Umformer U65a (neuere Form)", F 054a, Ln 20 347-1, 2 pp. (3 kW generator, 9 kW motor). Source: www.cdvandt.org
• Ref. 162G: "Beiträge der Firma Siemens zur Flugsicherungstechnik und Luftfahrt-Elektronik in den Jahren 1930 bis 1945 (Teil 1 & 2)", H.J. Zetzmann, in "Frequenz - Zeitschrift für Schwingungs- und Schwachstromtechnik", Part 1: Vol. 9, Nr. 10, 1955, pp. 351-360, Part 2 (pp. 387, 388, 392): Vol. 9, Nr. 11, 1955, pp. 386-395
• Ref. 162H: "Type 7", RAF Ventnor Radar website [pdf]
• Ref. 163: Mercury Arc / Vapor Rectifiers
• Ref. 163A: "Mercury cathode tubes: Ignitron, Excitron, Sendytron", Chapter 6, pp. 210-255, of "Gas-discharge tubes", H.L. van der Horst, Philips Technical Library series, 1964, 318 pp.
• Ref. 163B: "Mercury Arc Rectifier Practice", F.C. Orchard, Pittsburg Instruments Publ. Co., 1936, 255 pp. [pdf 19 MB]
• Ref. 163C: "Mercury Arc Power Rectifiers - Theory and Practice", O.K. Marti, H. Winograd, 1^st ed., McGraw-Hill Book Co. Inc., 1930, 478 pp. [pdf 38 MB]
• Ref. 163D: "Der Quecksilberdampf-Gleichrichter (Stromrichter) der Starkstromtechnik", Weissbach, in "Funk-Technik - Zeitschrift für das gesamte Elektro- Radio- und Musikwarenfach", pp. 15, 18, 19 in Nr. 1, 1948, and pp. 63, 66, 67 in Nr. 3, February 1948
• Ref. 163E: pp. 681-688 in "Electrical machines" R.K. Rajput, 4^th ed., Laxmi Publications, 2006, 881 pp.
• Ref. 163E: "Converters, the mercury arc rectifier and supply to electric railways", Chapter 10 in "Electric Railways 1880-1990", Michael C. Duffy, IET, 2003, 452 pp. [pdf]
• Ref. 163F: "Some notes on ignitrons and thyratrons", F. Dörenberg, 2014, 3 pp.
• Ref. 163G: "Controlling the DC output voltage of a Mercury Arc Rectifier", F. Dörenberg, 2014, 2 pp.
• Ref. 163H: "Sur le courant de reaction de l'arc electrique", Jules-Célestin Jamin, Georges Maneuvrier, p. 1615-1619 in "Comptes Rendus des Séances de l'Académie des Sciences", Vol. 94, January-June 1882, 1795 pp.
• Ref. 163J: "Method of Transforming Electrical Energy", Peter Cooper Hewitt, US Patent No. 780,999; filed April 25, 1902 (patented January 31, 1905), 7 pp.
• Ref. 163K: "Electric-Discharge-Controlling Device and Method of Operating the Same", Irving Langmuir (General Electric), U.S. Patent No. 1,289,823; filed November 6, 1914, published December 31, 1918, 5 pp.
• Ref. 163L: "DC Power Transmission - Mercury-Arc to Thyristor HVdc Valves", Deepak Tiku, in "IEEE Power & Energy Magazine", Volume 12, Nr. 2, March-April 2014, pp. 76-96 [pdf]
• Ref. 163M: "Physik und Technologie der Quecksilberdampfventile für die Hochspannungs-Gleichstrom-Übertragung", Johannes Mitterauer,prsented at VDE-Tagung "75 Jahre Hochspannungs-Gleichstrom-Übertragung (HGU), Entwicklung - Technologie - Anwendung", Berlin, 26-27 September 2011  [pdf]
• Ref. 163N: "Principles of Mercury Arc Rectifiers and Their Circuits", David Chandler Prince, Francis Brooke Vogdes, McGraw-Hill Book Co., 1^st ed., 1927, 233 pp. [pdf]
• Ref. 163P: "Current and Voltage Wave Shape of Mercury Arc Rectifiers", H. D. Brown, J. J. Smith, pp. 973-984 in "Trans. of the American Institute of Electrical Engineers", Vol. 52, Issue 4, December 1933.
• Ref. 163Q: "The development of power electronics in Europe", Frank Dittmann, 2004 IEEE Conf. on the History of Electronics, Bletchley Park/UK, June 2004, 14 pp. [pdf]
• Ref. 163R: "Vom Quecksilberdampfgleichrichter zur Leistungselektronik", A. Schmidt, J. Schräder, in "Elektrotechnische Zeitung (ETZ)", Vol. 101, 1880, Nr. 16/17, pp. 955-960.
• Ref. 163S: "Thyratrons and their applications to radio engineering", A.J. Maddock, in "Electrical Communication - A Journal of Progress in the Telephone, Telegraph and Radio Art", published by International Standard Electric Corp., pp. 339-378. Source: worldradiohistory.com, accessed 16 September 2020.
• Ref. 163T: "Brunswick West Mercury-Arc Tramway Substation", Nomination for the Engineering Heritage Australia Heritage Recognition Program, Version 11, November 2019, 29 pp. Source: engineersaustralia.org.au, retrieved 26 May 2022.
• Ref. 164: documents of the Combined Intelligence Objectives Sub-Committee (CIOS). Source: cdvandt.org.
• Ref. 164A: "Institutes of the Bevollmaechtigter fuer Hochfrequenz-Forschung", CIOS, Item No. 1 & 7, File No. XXXI-37, May 1945, 215 pp.; source: cdvandt.org.
• Ref. 164B: "The I.T.T., Siemens and Robert Bosch Organizations" [incl. Lorenz: Elektra, Sonne, Mond, Knickebein, Erika, Goldwever, Hermine, 6-mast Lorenz Adcock D/F based on British patent, Lorenz Blind Approach/Landing, IFF, radar], CIOS, Item No. 1, 7 & 9 (Radar, Signal Communications, Physical & Optial Instruments and Devices), File No. XXXI-38. Source: cdvandt.org. Retrieved 22 September 2019.
• Ref. 164C: "Report on C. Lorenz A.G." [history, factories, relationship with Philips & Telefunken, Stuttgart UHF radio link (FuG0s, FuG03a), Feuerzauber & Feuermolch Oboe-jammer, FuG200, FuG226/Neuling], CIOS, Item No. 1, File No. XXV-12, 13 pp. Source: cdvandt.org. Retrieved 7-Feb-2020.
• Ref. 164D: "Beacon Transmitters", in "Inspection of Philips Works at Eindhoven", Robert Watson Watt, CIOS Target Number 1/42, transcript of CIOS file No. III-1, 23-26 September 1944, 56 pp. Source: cdvandt.org. Retrieved 27 March 2022.
• Ref. 172: copy of item in file AIR 29/284 "Central Interpretation Unit (CIU) Medmenham; Interpretation reports and aerial photos (1943)". Item is in the collection of The National Archives; material with UK Crown Copyright, used in accordance with the Open Government License [pdf].
• Summary of the contents of ref. 172A.
• Ref. 172A: "German “Windjammer” R.D.F. Stations", part of "Monthly interpretation review for July 1943", 7 pp.
• Ref. 173: copy of items in file AIR 14/3577 "Signals investigation on 27 to 35 Mc/s "Windjammer" (1943/1944)". Items are in the collection of The National Archives; material with UK Crown Copyright, used in accordance with the Open Government License [pdf].
• Summary of the contents of ref. 173A-173E.
• Ref. 173A: "'Windjammer" observation", by R.A. Fareday (Noise Investigation Bureau [Electronic Intelligence], N.I.B., London), dated 20^th June 1944, 1 page.
• Ref. 173B: "Possible "Windjammer" transmissions", report by Flight Lieutenant Douglas of 192 Sq., dated 16^th December 1943, 1 page.
• Ref. 173C: "192 Squadron Flight report No. 215/43" by F/Lt Robinson to Squadron Leader Burtler, dated 15^th November 1943 (actual report by P/O G.F. Evans of 13^th November 1943), 6 pages.
• Ref. 173D: "Windjammer – Arcachon", letter from Air Ministry A.I.4. [intelligence branch section supervising RAF Y Service] to Commanding Officer of 192 Squadron, dated 16^th July 1943, 1 page + 1 aerial photo.
• Ref. 173E: "The Windjammer and Dreh-Elektra", by 192 Squadron Leader J. Whitehead, dated 18^th June 1943, 1 page.
• Ref. 174: copy of items in file AIR 14/3594 "Windjammer" station: photographs and interpretation reports. Includes vertical and low oblique aerial photographs of 'Windjammer' radar sites in Germany and France (1943/1944)". Items are in the collection of The National Archives; material with UK Crown Copyright, used in accordance with the Open Government License [pdf].
• Summary of the contents of ref. 174A-174J.
• Ref. 174G: "Interpretation report No. G.590" dated 6^th October 1942, of aerial photo taken over locality Morlaix, W/T station Mt. St. Michel, at altitude of 12k ft during Sortie Q/21 on 24^th September 1942, 2 pages + 1 photo.
• Ref. 174H: Letter entitled "W/T: Pouzauges/St.Michel-Mont-Mercure" on behalf of Group Captain commanding R.A.F. Station Medmenham to Squadron Leader Whitehead (A.I.4), dated 29^th March 1943, 1 page + 3 photos.
• Ref. 175: articles about the "Y" service and RAF 192 Squadron
• Ref. 175A: pp. 512-516, 524 in "Activities at Knockholt", J.A. Reeds, Appendix B in "Breaking Teleprinter Ciphers at Bletchley Park - General Report on Tunny with Emphasis on Statistical Methods (1945)", 1^st ed., I.J. Good, D. Michie, G. Timms (J.A. Reeds, W. Diffie, J.V. Fields, eds.), John Wiley & Sons, IEEE Press, 2015, 735 pp.
• Ref. 175B: "Account of 192 Squadron radio countermeasures operations" [part of the 'Y' service; "Bernhardine"], Frances Grundy, 1945, 8 pp. Source: IBCC Digital Archive, accessed June 16, 2021. Content is available under a CC BY-NC 4.0 International license (Creative Commons Attribution-NonCommercial 4.0).
• Ref. 176: post-war correspondence [in German] between Mr. Kurt Pfaender (frmr. Telefunken employee) and Telefunken, as well as Telefunken-internal, regarding past wages (back pay) and reimbursement of expenses incurred by Mr. Pfaender for transportation of Telefunken equipment from Trebbin to a site near Hannover, during February & March of 1945; source: corporate archives of DTM Berlin, part of file nr. I.2.060C-00499:
• Ref. 176A: Letter from Mr. Kurt Pfaender to the HR office of Telefunken in Berlin, with claims; dated 15 November 1950, 1 p.
• Ref. 176B: Letter from Mr. Albrecht Leyn (Telefunken/Hannover) to Mr. Gothe (Telefunken/Berlin), recollecting payments of bills & sale of items to Mr. Pfaender; dated 18 September 1951, 2 pp.
• Ref. 176C: Telefunken memo about conversation with Mr. Pfaender on 20 December 1951, regarding claims of the latter; dated 27 December 1951, 1 p.
• Ref. 176D: Letter from Kurt Pfaender to Telefunken in Berlin, describing the course of events; dated 12 January 1952, 2 pp.
• Ref. 177: post-war letters [in German] from the company "Hein, Lehmann & Co. Eisenkonstruktionen, Brücken- und Signalbau K.-G." in Berlin-Tempelhof to Telefunken in Berlin, with claims ("Altforderungen") regarding delivery and installation of various types of antenna systems (arrays, tube & lattice masts, wooden masts, metal-clad wooden huts, verticals, dishes, turntables, for "Bernhard", "Marius", "Marius II", "Uran II", "Forsthaus-KF", etc.), installations in Germany, Hungary, Monte Carlo, Croatia, etc., during the period of July 1942 through the end of the war (8 May 1945); source: corporate archives of DTM Berlin, I.2.060C-00541:
• Ref. 177A: Letter from Hein, Lehmann & Co. to Telefunken with payment status of 17 Telefunken purchase orders and the resulting outstanding significant claim; dated 19 June 1949, 2 pp.
• Ref. 177B: Letter from Hein, Lehmann & Co. to Telefunken with adjusted claims, based on assessment of Telefunken counter-claims; dated 19 June 1950, 8 pp.
• Ref. 177C: Letter from Hein, Lehmann & Co. to Telefunken, with further justification for claims regarding delivery & installation of 12 "Bernhard" antenna systems (against purchase order of July 1941) for Be-2 - Be-8 and Be-12, of 6 associated "Dioden-Masten" antenna masts (based on price quote of September 1941), and delivery (without installation) of the antenna systems of Be-1 and Be-9 - Be-11; dated 5 February 1951, 3 pp.
• Ref. 178: Reichsmark vs. US Dollar and Euro exchange and equivalency data:
• Ref. 178A: "Deutsche Bundesbank - Average Currency Exchange Rates 1908-1951 Mark / Reichsmark / Deutsche Mark (M/RM/DM) vs. France FRF / Austria K,S / USA $ / UK £ / Netherlands HFL", Vs 801, 12 pp. Retrieved 2017. [pdf]
• Ref. 178B: source of US dollar inflation (CPI, buying power) calculator: www.usinflationcalculator.com.
• Ref. 178C: Tabulated exchange rate of Reichsmark to US$, with conversion to 2016 US$ and Euro, Frank Dörenberg, 21 May 2017; based on ref. 178A/B.
• Ref. 179: "Votragsnotiz", draft presenter notes addressed to the General-Nachrichtenführer (Gen-Nafü), 3 September 1944, 3 pp.
• Covers original plans for geographic coverage (France, German Reich) with Bernhard stations, state of completion of the various Be-stations, status of introduction of the Bernhard/Bernhardine method for night-fighters (Nachtjagd).
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany (Signatur) file nr. RL 2-V/6, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016"
• Ref. 180: Layout of the Bernhard installation in Trebbin, based on a sketch from an eyewitness (name and date unknown); source: corporate archives of DTM Berlin, file nr. I.2.060C-07823.
• Ref. 181: "Drehfunkfeuer System Telefunken - Teil 1: Verfahrensbeschreibung EC1-4262", Adalbert Lohmann, Berlin, October 1942, 129 pp., copy nr. 29, personal copy of Albrecht Leyn; source: corporate archives of DTM Berlin, file nr. I.2.060C-06172  [file size: 62 MB; a lower-resolution version is here, 28 MB]
• Ref. 183: "Das Drehfunkfeuer-Verfahren Bernhard und Bernhardine, System Telefunken" ("Verfahrensbeschreibung Bernhard, Bernhardine", description of the Bernhard-Bernhardine method), Adalbert Lohmann, Telefunken Gesellschaft für drahtlose Telegraphie m.b.H., Berlin-Zehlendorf, Telefunken document EC 1 4310, July 1943, 28 pp., copy nr. 11; source: corporate archives of DTM Berlin, file nr. I.2.060C-04403.
• Ref. 188: List of 1929-1940 patents of the Conz company (and its employees) regarding frequency conversion and motor speed control; source: DEPATISnet (search-engine of the German patent & trademark office, DPMA).
• Ref. 189: "Stückliste zum Kabelplan "Bernhard"" [parts list of "Bernhard" wiring diagram], Telefunken document EC1-4237, 6 July 1942, 23 pp.; source: corporate archives of DTM Berlin, part of file nr. I.2.060C-07753.
• Ref. 190: "Kabelplan "Bernhard"" [system block diagram], Telefunken Gesellschaft für drahtlose Telegrafie m.b.H., document EC1-4237, 27 June 1942, 1 sheet; source: corporate archives of DTM Berlin, part of file nr. I.2.060C-7753.
• Ref. 191: Chapter 4.4 (pp. 93-118) in "Die Geschichte des Quecksilberdampf-Gleichrichters bei BBC Deutschland 1913 - 1963", Peter Rudolf Wetzel, dissertation University of Stuttgart, 2001, 359 pp., OCLC nr. 51713376.
• Ref. 192: "Electronic Rectifiers and Valves", A. Güntherschulze [pdf], translation of "Elektrische Gleichrichter und Ventile" by Norman A. de Bruyne (translator), John Wiley & Sons 1928, 227 pp.
• Ref. 193: "Justier- und Prüfvorschriften für Schienenkranz" [Adjustment and verification instructions for circular rail track], Telefunken Gesellschaft für drahtlose Telegrafie m.b.H., Berlin-Zehlendorf, document nr. EC1-4160, 12 June 1942, 11 pp., p. 7 & 9 missing; source: corporate archives of DTM Berlin, part of file nr. I.2.060C-07753.
• Ref. 195: first page of "Aenderung des Modulators für Zeigersender "BERNHARD"" [modification of the "Bernhard" compass scale transmitter modulator], Telefunken GmbH, document nr. EC1-4157B, February 1943; source: corporate archives of DTM Berlin, part of file nr. I.2.060C-07755
• Ref. 196: "Quarzvorsatzstufe für die 500 Watt-Sender der Anlage "BERNHARD"" [crystal front-end for the "Bernhard" 500 watt transmitters], E-Stelle Rechlin, dept. EB8-SE0525B, date unknown, 1 p.; source: corporate archives of DTM Berlin, part of file nr. I.2.060C-07755
• Ref. 197: pp. 11-13, 24 in "Kabel-Herstellung: Kabelaufbau, Werkstoffe, Verfahrenstechnik" [cable manufacturing], Walther Ehlers, Hermann Lau, Springer-Verlag (publ.), 1956, 434 pp.
• Ref. 198: FuG 120a and Psch 120a
• Ref. 198A: "Ergänzung zur Beschreibung FuG 120 - Nachtrag: FuG 120a, Peilschreiber Psch 120a" ["Supplement to description of FuG 120, Appendix FuG 120a, Psch120a printer"], Telefunken Abt. FN/TL, August 1944, 11 pp. Source: corporate archives of DTM Berlin, file nr. I.2.060C-07754.
• Ref. 198B: "Funknavigationsanlage FuG 120 a - Einzeladerverlegung" [wiring list & diagram], Telefunken Gesell. für drahtlose Telegraphie m.b.H., document nr. V/F 2297, December 1944, 2 pp. Source: corporate archives of DTM Berlin, file nr. I.2.060C-07754.
• Ref. 198C: "Reglerkasten Rgk 120a" [control box], Telefunken Gesell. für drahtlose Telegraphie m.b.H., document nr. V/F 2298, December 1944, 2 pp. Source: corporate archives of DTM Berlin, file nr. I.2.060C-07754.
• Ref. 198D: "Peilschreiber Psch 120a Stromlaufplan, Schaltplan-Stückliste" [schematic & parts list], Telefunken Gesell. für drahtlose Telegraphie m.b.H., document nr. V/F 2334, 1 & 12 December 1944, 3 pp. Source: corporate archives of DTM Berlin, file nr. I.2.060C-07754.
• Ref. 198E: "Peilschreiber P.Sch.120a - Ln 28 997 - Gerät-Nr. 124-270 A - Beschreibung und Betriebsvorschrift" ["PSch120a Description and Operating Instructions"], Siemens Fernmelde Technik, Siemens & Halske AG, Wernerwerk für Telegrafiegeräte, Berlin-Siemensstadt, 23 pp. No date on document, but schematic is dated 24 August 1944.
• Ref. 201: 3 photo pages from "Unterlagenmappe und Bedienungsvorschrift zu den Bordnavigationsgeräten "FuG 120" und FuG 120a"" ["Documentation file and operating instructions to on-board navigation equipment FuG 10 and 120a"], Telefunken Gesell. für drahtlose Telegraphie m.b.H., TFK FN/TL Bord, August 1944; source: corporate archives of DTM Berlin, file nr. I.2.060C-07760.
• Ref. 207: p. 65 in "Hamburgs alte Fabriken - einst und jetzt", E. Freiwald, G. Freiwald, Sutton Verlag, 2013, 159 pp.
• Ref. 208: carbon pile regulators:
• Ref. 208A: "Carbon Pile Regulator" pp. 11-13 in "Aircraft Electrical Systems", E.H.J. Pallett, Pitmann Publ., 1976, 166 pp.
• Ref. 208B: "Carbon pile regulators", June 1945 [pdf]
• Ref. 208C: Pintsch advertising, p. II  in "Elektrotechnische Zeitung", Nr. 12 (21 March), 1935.
• Ref. 211: "Amplitude Modulation and Demodulation", Frank Dörenberg, V1.1, August 2017, 8 pp.
• Ref. 214: "Vindmotor med automatiska regleringsanordningar" [wind turbine with automatic control devices]; Finnish patent nr. 3606 [Finnish title "Tuulimoottori itsetoimivilla ohjejärjestelyillä"]; inventors: Eduard Abegg, Carl Gustaf Oscar Grevillius; owner: Fridolf Leonard Schaumann; awarded 25-Feb-1909, 44 pp.
• Ref. 215: p. 246 in "Disturbance signals in a feedback control system", section 4.4 in "Modern Control Systems", Richard C. Dorf, Robert H. Bishop, Prentice Hall publ., 12^th ed., 2011, 1083 pp.
• Ref. 218: "Der Längstwellensender Goliath bei Kalbe (Milde)", Klaus Herold, pp. 169-190 in "100 Jahre Funktechnik in Deutschland: Funksendestellen rund um Berlin", Wolfgang Behnke, Vol. 1 of "100 Jahre Funktechnik in Deutschland", Wissenschaft-und-Technik Verlag, 3^rd ed. 2004, 342 pp., ISBN: 3-936124-65-5 See note 1
• Ref. 221: "Dr. phil. Siegmund Loewe (1885-1962)", Herbert Börner, in "Funkgeschichte", Vol. 12 (1989), Nr. 67, pp. 9-13 [pdf]
• Ref. 223: "PSU and generator for Bernhardine Hundberg Denmark", US National Archives and Records Administration (NARA), Scan Nr. 9821 111SC 269041; courtesy Mike Dean.
• Ref. 224: several pages from the 20 page April 1939 product catalog and price list for GURO and RAPID products of the Paul Jordan Elektrotechnische Fabrik G.m.b.H. Co, KG. in Berlin-Steglitz.
• Ref. 228G: pp. 200-204 in "Rotating beacons", Section 4.12 of "Radio Aids to Civil Navigation", Reginald Frederick Hansford (ed.), Heywood & Co. Ltd. (publ.), 1960, 623 pp.
• Ref. 229: civil equi-signal beam systems (Scheller, Fixed-course & Four-Course ranges, E/T & A/N beacons, Visual Ranges, Visual Aural Ranges)
• Ref. 229A: articles in German and Dutch language
• Ref. 229A1: "Über die Wirkung von Schellers drahtlosen Kursweiser auf das Flugzeug" ["About the impact of Scheller's wireless direction pointer on aircraft", Eberhard Buchwald, in "Zeitschrift für drahtlose Telegraphie und Telephonie sowie des Gesamtbereichs der elektromagnetischen Schwingungen", Vol. 15, Nr. 2, February 1920, pp. 114-122. Source: hathitrust.org, retrieved April 2021.
• Ref. 229A2: "Neue Versuche über funkentelegraphische Richtsender" ["New trials with directional spark transmitter stations"; A/N system], Franz Kiebitz, in "Zeitschrift für drahtlose Telegraphie und Telephonie sowie des Gesamtbereichs der elektromagnetischen Schwingungen", Vol. 15, Nr. 4, April 1920, pp. 299-310.
• Ref. 229A3: "Zur Geschichte der Richtwirkungs- und Peilversuche auf den Flugplätzen Döberitz und Lärz" ["History of radio directivity- and direction-finding tests at Döberitz and Lärze airfields"], Richard Baldus, Eberhard Buchwald, Rudolf Hase, in "Jahrbuch - Zeitschrift für drahtlose Telegraphie und Telephonie", Vol. 15, Nr. 2, February 1920, pp. 99-100. Source: hathitrust.org, retrieved April 2021.
• Ref. 229A4: "Über Richtempfangsversuche im Flugzeug" ["About directional reception in airplanes"], Eberhard Buchwald, in "Jahrbuch - Zeitschrift für drahtlose Telegraphie und Telephonie", Vol. 15, Nr. 2, February 1920, pp. 101-113. Source: hathitrust.org, retrieved April 2021
• Ref. 229A5: "Das Kaiserliche Telegraphen-Versuchsamt" ["The Imperial Telegraphy Test Institute"], in "Telefunken Zeitung", Vol. 3, No. 1, January 1914, pp. 7-9. Source: radiomuseum.org, retrieved 11 April 2021.
• Ref. 229A6: "Neuere Arbeiten auf dem Funkbaken-Gebiete" ["Recent work in the field of radio beacons"; Lorenz, E/T keying, magnetic-bias keying, VHF beacon], Ernst Kramar, "Hochfrequenztechnik und Elektroakustik", Vol./Nr. 40, September 1932, pp. 88-92. [Abstract].
• Ref. 229A7: "Lorenz-ultra-korte golf-landingsbaken voor vliegtuigen" ["Lorenz VHF landing beacon for aircraft"], H. Veenstra (Lorenz; based on E. Kramar), in "Radio-Nieuws", Vol. 18, Nr. 3, 15 May 1935, pp. 49-61. Source: nvhrbiblio.nl, retrieved 24 May 2022.
• Ref. 229A8: "De Nederlandsche radiobakens" ["The Dutch radio beacons"; incl. B.R.A. 101], pp. 59-66 in "Radio en Luchtvaart" ["Radio and aviation"], S. van der Molen, No. 5 of "Meulenhoff's Luchtvaartserie", J.M. Meulenhoff (publ.), 1936, 107 pp. Source: us.archive.org, retrieved 22 May 2022.
• Ref. 230: German & British WW2 RDF, radio-navigation systems, and associated jamming systems / countermeasures
• Ref. 230A: p. 46 in "The Secret War", Brian Johnson, Pen and Sword (publ.), 2004, 352 pp.
• Ref. 230B: Table 1 in "Verfahren und Anlagen der Funkortung" ["Radio-navigation methods and installations"], W. Stanner, in "Elektrotechnische Zeitung (ETZ)", Ausgabe A, Vol. 75, Nr. 13, 1 July 1954, pp. 438-442. [circular LoP, hyperbolic LoP, Consol, Consolor, Decca, Loran, range of various systems incl. "Erika", "Erich", "Hermine", and "Mond"]
• Ref. 230C: "Pulling the crooked-leg", R.V. Jones, in "New Scientist", 23 February 1978, pp. 493-496.
• Ref. 230D: "Most Secret War: Britisch Scientific Intelligence 1939-1945", R.V. Jones, Hamish Hamilton (publ.), 1978, 576 pp. See note 1
• Ref. 230E: "Milestones - Battle of the Beams", Carlo Kopp, in "Defence Today", January/February 2007, pp. 76, 77.
• Ref. 230F: "The Battle of the Beams - Part 1-3", D.V. Pritchard (G4GVO), in "Ham Radio Magazine", June 1989 pp. 29-38, August 1989 pp. 20-29, October 1989 pp. 53-61.
• Ref. 230G: "Chapter II and III in "R. V. Jones and the Birth of Scientific Intelligence", James Martinson Goodchild, PhD thesis, University of Exeter, March 2013, 640 pp. [pdf] Accessed 12 May 2019.
• Ref. 230H: "Electronic Warfare and the Night Bomber Offensive", Rob O'Dell, pp. 97 - 117 in "Air Power Review", Royal Air Force, Volume 10, Number 1, Spring 2007.
• Ref. 230J: "Radio Navigation Systems for Aviation and Maritime Use — A Comparative Study" [RDF, Consol/Consolan, Navaglobe, VOR, VORTAC, VOR/DMET, Navarho/Navarho-H/-HH/-Rho, Decca, Standard Loran (Loran-A), Loran-C, Radio Mesh Systen], W. Bauss (tech ed.), Advisory Group for Aeronautical Research and Development (AGARD), North Atlantic Treaty Organization (NATO), AGARDOgraph 63, Pergamon Press, 1963, 232 pp. Translation of the German publication "Funkortungssysteme für Luft- und Seefahrt - Eine vergleichende Gegenüberstellung", Verkehrs- und Wirtschaftsverl. Dr. Borgmann (publ.). [pdf, file size 58 MB]. The following are articles taken from this book.
• Ref. 230J1: "Radio Direction-Finding on Board Aircraft and Ships", W.T. Runge, pp. 19-28.
• Ref. 230J2: "Consol and Consolan", Ernst Kramar, pp. 29-39.
• Ref. 230J3: "VOR-System", K. Bärner, pp. 43-57.
• Ref. 230J4: "Decca". H. Lueg, pp. 81-101.
• Ref. 230J5: "Standard-Loran", Ernst Kramar, pp. 113-118.
• Ref. 230K: "The Navigational Beam System "Elektra-Sonne" [Elektra, Sonne, Elektra-Sonne, Mond; complete German description, short translated summary in English], Otto von Heil, FIAT Final Report No. 1105, Field Information Agency Technical (FIAT), US Office of Military Government for Germany, 17 June 1947, 177 pp. Source: www.cdvandt.org. Accessed: March 2019.
• Ref. 230L: "Funknavigation, Elektra, Sonne, Mond, Stern, Erika", J. Goldmann (Lorenz), Vorträge vor Fernmelde-Ingenieuren der Luftwaffe - Luftnachrichtenschule Halle (Saale) [Luftwaffe Signals School], February 1944, 22 pp. [file size: 25 MB]
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 2-V/48, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230M: "Sonne Planungen" [planning of Sonne sites], Luftnachrichten telegram, dated 29 July 1944, signed by Capt. Franz, 1 p.
• Document mentions Sonne station Liebau, Sonne stations 12 (Warsaw) & 23, Großsonne station 32 (Danzig), and new Sonne site near Oppeln.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 2-V/6, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230N: "Bumerangstörung im Ruhrgebiet" [Jamming of "Bumerang" (German codename for Oboe-guided British Mosquitoes) in the Ruhr area), Nr. 82 514/44 g.Kdos. (3.Abt.III)
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 2-V/6, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230P: original correspondence of the Director General of Luftwaffe Signals Corps (General Nachrichtenführer). Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 2-V/5., used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230P1: "Anruf Gen.Martini wegen Erstellung Boden-Truhe West" [telephone call with General Martini regarding construction of Boden-Truhe West]. Letter/telegram from Gen. Nachrichtenführer (1.Abt.II), addressed to Chef. der Ln.Inspektion. Letter ref. OKL Gen.Nafü. Nr. 10 955/44 g.Kdos. (1. Abt.II). Letter is dated 18 June 1944. Letter states that due to current situation, the forward-looking Boden-Truhe West station will not be constructed and construction of the rearward-looking Boden-Truhe West station will be accelerated, using transmitters of the prior. The planned transmitters will be transported from France, but with trucks/lorries (wood gas) instead of by rail.
• Ref. 230P2: "Fernmündliche Rücksprache Major Kluge - Hptm. Gottschalk am 30.6.44" [telephone conversation Major Kluge - Captain Gottschalk]. Letter from Gen.Nafü (1.Abt.), addressed to Lfl.Kdo. 3 - Höh.Nafü, General der Navigation, and General der Kampfflieger. Letter ref. OKL Gen.Nafü. Nr. 11 092/44 g.Kdos. (1. Abt.II). Letter dated 8 July 1944. Letter states that, due to operational and test reasons, construction of radio navigation stations "Komet 2 (Laharie)", "Komet 3 (Labouheyre), and "Dora 2 (Morlaix) cannot be finished. Due to failure of "Erika 2 (Cherbourg)", the "Erika" system can no longer be used in the West. Therefore, "Erika 1 (Boulogne)" can be dismantled and parts (transmitter etc.) be secured.
• Ref. 230P3: "Sender for Bodentruhe" [transmitters for Truhe ground station]. Letter from Gen.Nafü (1.Abt.), addressed to Gen.Nafü/Ln.Insp (5.Abt/6.Abt). Letter is dated 8 July 1944. Letter describes allocation of 3 "Feuerstein" transmitters instead of "Feuerzange" transmitters to "Bodentruhe West", also mentions 3 "Merkur" transmitters are to be modified for "Bodentruhe West", schedule for delivery of additional "Merkur" and "Feuerstein" transmitters to be provided.
• Ref. 230P4: "Abschalten von Rundfunksendern." [Shutdown of (public) radio broadcast transmitters]. Letter from OKL.Gen.Nachrichtenführer. Letter ref. 11 987/44 geh. (1.Abt.II). Letter is dated 2 July 1944. Letter states that, as agreed with OKW and RPromin [Reichs Propaganda Ministerium], the request for shutting down radio broadcast transmitters during jamming/interference of radio beacons for day & night fighters, is denied. Reasons given by RPromin: 1) the current regulations already imply large scale shutdowns, further reduction is unacceptable for the propaganda, 2) the population interprets shutdowns as sign of imminent air raids. Shutdown for other reasons would cause unrest, and 3) Broadcast transmitter frequencies are fixed. If broadcast transmitters interfere with radio beacons or other services, Lfl.Kdo. must make sure that those services use other frequencies. As in other Luftflotten regions, restriction of radio beacons improves spread of utilized frequencies.
• Ref. 230Q: articles about Knickebein
• Ref. 230Q1: "Location of Knickebein stations K1-K13" [map coordinates, satellite images, aerial photos], Frank Dörenberg, latest update: 18 January 2022, 22 pp.
• Ref. 230Q2: pp. 245-247 in "Gleichgeschaltet: Maulburg im Nationalsozialismus und die Rolle von Hermann Burte im Dritten Reich", Hansjörg Noe, Verlag Waldemar Lutz (publ.), 448 pp., ISBN 978-3-922107-09-5. [Extract]
• Ref. 230Q3: p. 16 of "Knickebein" thread in the forum of geschichtsspuren.de, post by ChristianCH on 30-Mar-2014. [Extract]
• Ref. 230Q4: p. 2, 3 in "Krigsminner 1940-45 i Klepp kommune" ["War memories 1940-45 in the Klepp municipality"], F. Ravndal, T. Ødemotland, A. Jakobsen, T. Erga, O. Håland, B. Bore, A. Hatteland, J. Sørbø, T. Reve, Laget (publ.), 1990, 8 pp. Source: Norwegian National Library, accessed 31 July 2020. [pdf]
• Ref. 230Q5: "Kontrollpunkten der Knickebein-Anlage 4 (Karten), dabei Gesamtübersicht der Kontrollpunkte, Bereich zwischen Kranenburg und Donsbrüggen" [file size: 34 MB] ["Radiation-pattern check points for Knickebein Nr. 4 ( = Kleve-Materborn) in the area between Kranenburg and Donsbrüggen"], 8 maps with check points marked by small red dots and red lines, some measured field strength values are written in green (dated January 1942), Kranenburg = ca. 13 km west of K4; Donsbrüggen = ca. 12 km northwest of K-4; 2 maps with check points in The Netherlands (just north & south of Groesbeek = ca. 18 km west of K-4)]. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, Signatur/file nr. RL 19/6/64 - 19/6/84  (frmr. RL 19/537), used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230Q6: "Knickebein" [incl. difference between KG 100 and other LW Kampfverbände], Luftwaffenführungsstab Ia (KM), adressed to "I L", 6 October 1940, g.Kdos, 1 page + 1 map. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, Signatur/file nr. RM 7/2372, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230Q7: "Navigatorische Ausnutzung von Fernfunkfeuern Ukw. (Knickebein)" ["Utilization for navigation of long-range VHF radio beacons (Knickebein)"], memo  Az. 47 p 14, B.Nr.  545/40 g.Kdos., signed by Major Schubert for the Chief of Staff of Luftflottenkommando 2, 5 May 1940, 3 pp. [Keywords: Knickebein, coordinates / radio frequency / center beam pointing direction for Stolberg & Kleve, width of the dots & dashes zones, vertical extent of the radiation pattern, 2 pp. utilization guidelines "Merkblatt" - not to be taken into the aircraft; if taken prisoner, no information shall be divulged]. Source: Bundesarchiv (BArch) Freiburg/Germany, Signatur/file nr. RL 19-6/40 (frmr. RL 19/537), low quality microfiche, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230Q8: "Planung und Erstellung von UKW-Fernfunkfeuern (FFuFd) für die Funknavigation der Luftwaffe" ["Planning for, and construction of, long-range VHF radio navigation beacons of the Luftwaffe"], memo Az. 47 f 68, Nr. 2714/39 g.Kdos., addressed to Reichsminister of Aviation, Supreme Commander of the Luftwaffe, and Chief of the Signal Corps; draft signed by Flight Staff Engineer Gosewisch, 10 September 1939, 12 pp. [Keywords: high priority construction of beacons for Luftwaffe operations over the North Sea; requirements for the first 5 rotable beacons (3x Telefunken G.m.b.H. (high power (3 kW); up to 1200 km range (depending on radio set and aircraft altitude); to be located at Stolberg, Cleve, Borkum; code name Knickebein; antenna system weight 200 (metric) tonnes), 2x C. Lorenz A.G. (lower power (500 W); up to 300-600 km range; to be located at Bad St. Peter and on the isle of Sylt; code name Karussel) in terms of equisignal beam width ±0.2° initially (later ±0.1°), dots & dashes zones width ±12°, rotability range ±45° from center beam-direction, radio frequencies compatible with FuBl 1 radio set (29.8-33.6 MHz, 5 fixed frequencies`+ 2 field-modifiable); degree to which the terrain around the beacons must be flat and unobstructed; remote monitoring radio receiver at each site; diagram with dimensions of the Knickebein antenna system and the rotation tracks; table for standard landing beam + Knickebein + Karussel with (humidity dependent) ranges for 3 receiver types (each with 2 different antennas); graph with 0.3° equisignal beam-width and useable altitude vs. range based on beacon signals audibility = vertical usability boundaries of the equisignal beam lobe].  [file size: 25 MB]. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, Signatur/file nr. RL 19-6/40 (frmr. RL 19/537), low quality microfiche, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230Q9: "Geodätische und elektrische Einmessung der Knickebein-Anlage - Richtlinien über die geodätische und elektrische Einmessung der Knickebein-Anlagen - Anforderungen für die Auswahl und Vermessung des Kontrollbogens bei Knickebein-Anlagen" ["Geodetic and electrical calibration of the Knickebein stations - Guidelines fo the calibration - Requirements for the selection and measurement of the verification-arc of Knickebein installations"], As. 47 f 57 Nr. 72/41 g.Kdos., draft signed by Flight Staff Engineer Gosewich, 17 January 1941, 9 pp. [Keywords: all measurement points to be marked with concrete marker (graphic), 0.5° spacing between adjacent markers, 1:5000 maps for Knickebein K-2, sample data sheet for measurements of both dots & dashes beams )]. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, Signatur/file nr. RL 19-6/40 (frmr. RL 19/537), low quality microfiche, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230Q10: "Erläuterungsbericht zu dem Vermessungsarbeiten für den U.K.W.B Kleve - Ergänzung zum Eläuterungsberiche" ["Explanatory report regarding the measurement activities for the Kleve VHF beacon + supplement"; measurement points must have visual contact with the beacon, distance from beacon: measurement with a truck, so measurement points must lie on accessible roads; min & max distance from beacon: 0.8 and 2 km (exceptions possible); no check points allowed near power lines; check point spacing 0.5°; check points marked with marker stone, sign, or nothing; check points also to be marked on the outer concrete ring of the beacon; mentions map in ref. 230Q5], signed by Dip.-Ing Schmitt, 7 pp. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, Signatur/file nr. RL 19-6/40 (frmr. RL 19/537), low quality microfiche, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230R: articles about the X-Verfahren ("X-Procedure), X-Gerät ("X-Equipment"), Y-Verfahren ("Y-Procedure"), Y-Gerät ("Y-Equipment"); this Y-navigation method is not to be confused with the "Y" fighter-guidance method (incl. Y-Peiler ("Y-D/F system") which is also referred to as "Y-verfahren", nor with the British radio monitoring/intercept Y-Service.
• Ref. 230R1: pp. 48-49 (X-Gerät, Y-Gerät) in "German Radio Communication Equipment", US War Department Technical Manual, TME 11-227, June 1944, 61 pp.
• Ref. 230R2: "Fliegerhorst Köthen" ["Köthen airfield"], source: Militärhistorisches Museum Anhalt, accessed 11 August 2020. [pdf]
• Ref. 230R3: pp. 14-27 in "The First Pathfinders - The Operational History of Kampfgruppe 100, 1939-1941", Kenneth Wakefield, William Kimber (publ.), 1981, 265 pp.
• Ref. 230R4: pp. lxx-lxxiv in "The Bombing War: Europe, 1939-1945", Richard Overy, Penguin Books Ltd. (publ.), 2014, 852 pp. (published 2013 by Allan Lane, published 2015 as "The Bombers and the Bombed: Allied Air War Over Europe, 1940–1945")
• Ref. 230R5: "Der gezielte Blind-Bomben-Wurf - Die deutsche Lösungen: Das X-verfahren, Das Y-verfahren (Kampf)" ["The targeted blind bomb drop - The German solutions: the X-Procedure, the Y-procedure"], Heinrich Pusch (Oberst a.D. (Colonel, retired); Gruppenkommandeur Kampfgruppe 100 in 1939, Kommandeur Luftnachrichten-Regiment 31 in 1941 and Ln-Regiment 56 in 1943], date unknown (but after 1949/50, based on references to volumes of Winston Chruchill's memoires published in 1949 & 1950, see ref. 230R14 & 230R15 below), 71 pp, p. 14 & 16 missing. [file size: 49 MB]. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, Signatur/file nr.ZA 3/402a, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230R6: "The Wizard War", Chapter XIX (pp. 337-352) in "Alone", Book II in "Their Finest Hour" [file size: 29 MB], Vol. II (of 6) of "The Second World War", Winston S. Churchill, Houghton Mifflin Co. (publ.), 1949, 836 pp. Source: readerssection.com, accessed 30 December 2021.
• Ref. 230R7: "The offensive in the Aether", Chapter XVI (pp. 248-259) in "The Onslaught of Japan", Book I in "The Hinge of Fate" [file size: 23 MB], Vol. IV (of 6) of "The Second World War", Winston S. Churchill, Houghton Mifflin Co. (publ.),1950, 476 pp. Source: readerssection.com, accessed 30 December 2021
• Ref. 230R8: "Das Y-verfahren. Eine Weiterentwicklung des X-Verfahrens. Erdacht von Dr. Ing. Hans Plendl, 1940 Flieger-Oberstabingenieur bei der Erprobungsstelle der Luftwaffe Rechlin/Mecklb." ["The Y-Procedure. An evolution of the X-Procedure. Conceived by Hans Plendl, 1940, Pilot – Senior Staff Engineer at the Luftwaffe test center at Rechlin/Mecklenburg"], 32 pp. Source: Bundesarchiv (BArch) Freiburg/Germany (Signatur) file nr. ZA 3/402a, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230R9: "I./K.G.66 - Kurzer Abriss der technischen und taktischen Einsatzgrundlagen der I./K.G.66 (Zielfindergruppe West) in verschiedenen Kriegsphasen" ["Short overview of technical and tactical operationprinciples of No. 1 Group of Kampfgeschwader 66 (Pathfinder Group West)"], [keywords: target finding & marking; Ju-88 S, Ju-188 E; Vannes, Poix, Le Bourget; I./K.G.100; X-Verfahren, Y-Verfahren, Egon, 1324/Truhe-Verfahren; detailed list of I./K.G.66 aircraft/crew losses 30-May-1943 - 11-Apr-1945], Hans Herbestreit, ca. 1970, 14 pp. Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, Signatur/file nr. RL 10/638, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 230S: articles about "Komet" ("Comet")
• Ref. 230S1: "Tysk Retningsantenneanlæge i Kølby Vest for Nibe" ["German Directional Antenna Installation in Kølby, west of Nibe"; rotating-beam system "Komet" ????], Commission for the Inspection of German Radio Stations Constructed in Denmark, report by Capt. Bahnsen and Prof. Jørgen Rybner of site visit on 12 Dec 1945, 3 pp. Courtesy M. Svejgaard, used with permission. English translation by me is here.
• Ref. 230T: "Scientific Intelligence", R.V. Jones, 12 February 1947 lecture, "CIA Studies in Intelligence" Vol. 6, No. 3 (Summer 1962), pp. 55-76. Source: cia.org, accessed 12 August 2020. [pdf]. This is a slighly edited version of the original 12 February 1947 lecture, as first published in "Journal of the Royal United Services Institution", nr. 42, August 1947, pp. 352-360.
• Ref. 230U: "Radio navigation equipment", Section three of "Graphic survey of radio and radar equipment used by the Army Air Force", U.S. Army Air Forces, Air Technical Service Command, 1 May 1945, 68 pp. [file size: 21 MB].
• Ref. 230V: "Navigational Aids" [MF & HF D/F, SBA, Radio Ranges, Gee, SCR 277, B/T, BABS, GCA], pp. 24-28 in "The signals war: A brief history of no. 26 Group", AIR 14/3562, UK Air Ministry, Bomber Command, December 1945.
• Ref. 230W: "Aerial Navigation and Traffic Control with Navaglobe, Navar, Navaglide, and Navascreen", H. Busignies, Paul R. Adams, Robert I. Colin, in "Electrical Communication - A Journal of Progress in the Telephone, Telegraph and Radio Art", published by "International Standard Electric Corp.", Vol. 23, No. 2, June 1946, pp. 113-143. Source: worldradiohistory.com, retrieved 17 August 2020.
• Ref. 230Y: "Radionavigation in the UK in World War II", F.C. Richardson, in "The Journal of Navigation", Vol. 45, Issue 1, January 1992, pp. 60-69. Source: en.booksc.org, accessed April 2021. [pdf, See note 1]
• Ref. 230Z: "Zielfluggeräte nach ‟Dieckmann-Hell‟" [Dieckmann-Hell airplane radio direction finding systems; Luftwaffe ZVG 15 / 16 / 17 Z, FuG 141], Werner Thote, in "Radiobote", Vol. 13, Nr. 76, September-October 2018, pp. 14-19. Source: radiobote.at
• Ref. 235: "The invention of synchronous rotations by means of Paul la Cour's Phonic Wheel as used in Telegraphy", P. Chr. Dresing, in "The Telegraphic Journal and Electrical Review", Vol. XX, No. 476, 7 January 1887, pp. 31, 32.
• Ref. 243: "Belsize Park Deep Shelter", Nick Catford, 27 January 2000, Retrieved 30 August 2019. [pdf]
• Ref. 244: Luftwaffe & Royal Air Force  fighter intercept & control methods ("Jagdverfahren"), maps, and related topics
• Ref. 244A: "Nachtjagd" [intro, descriptions, and evaluations], Luftwaffe document, date unknown, 18 pp. Source: German Russian Project for digitization of archives in the Russian Federation. Retrieved 29 August 2019.
• Ref. 244B: "Bestimmungen über Nachtjagd" [descriptions of methods, and instructions to Flak organisation regarding night fighting], 1^st Flakdivision, Berlin, 19 November 1943, 12 pp. Source: German Russian Project for digitization of archives in the Russian Federation. Retrieved 29 August 2019.
• Ref. 244C: "Mosquito Nachtjagd", [specific fighter and flak tactics against incoming British "Mosquito" fighter-bombers] 1^st Flakdivision, Berlin, 7 March 1944, 5 pp. Source: German Russian Project for digitization of archives in the Russian Federation. Retrieved 29 August 2019.
• Ref. 244D: "Das Y-verfahren für Tag- und Nachtjagd" [file size: 115 MB; good-but-lower-reslution file is here 36 MB], document without reference number, without date, without place, 113 pp. 
• Complete description of the "Y" procedure for day & night fighter control from ground plotting stations with short wave equipment.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 2-V/38, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 244E: "Anlage 1 zu Luftflottenführungsabteilung Ia op2 Nr. 500/41 geh." [file size: 28 MB; good-but-lower-resolution file is here, 4 MB]. Map is not dated.
• Map covers area of Belgium, The Netherlands, Denmark, northern Germany incl. Berlin. Map is marked with locations of militärische Sperrgebiete, Nachtsperrgebiete, Nachtjagdgebiete, Dunkle Nachtjagdsräume.
• Map size: 4x2 (WxH) A4-sheets. Map is low-quality blueprint copy.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 20/186/K.
• Ref. 244F: "Einsatzbeispiel für einen Feindeinflug" (example of response to intruding enemy aircraft). Map is not dated. [file size: 84 MB; good-but-lower-resolution file is here, 10 MB].
• Map shows ground track of enemy bomber stream arriving from Britain with target Frankfurt, intercepting fighters, timing, etc. Map includes large & detailed table of the entire nightfighter intercept process, from long-range radar detection to "kill", with step-by-step status/activity/communication at the level of Flugmeldekompanie, Nachtjagdraum, Fühlungshalter, Jagdgruppe, Flugmeldungszentrale, Fluko, and Flak; the entire sequence covers 1 hr 40 min.
• Map size: 4x5 (WxH) A4-sheets.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 36/443.
• Ref. 244G: "Luft-Navigationskarte in Merkatorprojektion - Erweitertest Blatt Deutschland mit Jägernetz", Bodenorganisation Großraum-Nachtjagd Luftflotte Reich, July 1944. Source: Bestand/File 500, Findbuch/Index 12452, Akte/record 286 of the German-Russian Project for the Digitization of German Documents in Archives of the Russian Federation. Retrieved 28 August 2019.
• Ref. 244H: "Nederland en de Duitse Nachtjacht - Van jager tot prooi" (The Netherlands and German night fighting - from hunter to prey), W.H. Lutgert, R. de Winter, pp. 536- 545 in "Militaire Spectator", vol. 183, nr. 12, December 1994. Accessed September 2019. [pdf]
• Ref. 244J: "Nederland en de Duitse Nachtjacht - Van jager tot prooi (Deel 2)" (The Netherlands and German night fighting - from hunter to prey - part 2), W.H. Lutgert, R. de Winter, pp. 5-17 in "Militaire Spectator", vol. 184, nr. 1, January 1995. Accessed September 2019. [pdf]
• Ref. 244K: "De Luftwaffe en Nederland - Balans van een oorlogserfenis" (The Luftwaffe and The Netherlands - legacy of a war), W.H. Lutgert, R. de Winter, pp. 450- 459 in "Militaire Spectator", vol. 184, nr. 10, October 1995. Accessed September 2019. [pdf]
• Ref. 244L: "Nachtjagdnavigationskarte - herausgegeben von NJG.3.-NO" [night-fighter navigation chart issued by the Nachrichten-Offizier of the no. 3 night fighter-wing, Nachtjagdgeschwader 3]. [file size: 25 MB]
• Map is not dated. Bernhard-stations Be-0, Be-6, Be-8 through Be-12 are also marked on this map. Source: collection R. Grywatz.
• Ref. 244M: "Tag- und Nachtjagd, 3. Jagddivision (als beispiel)".  Map is dated 29 July 1944.  [file size: 24 MB; good-but-lower-resolution file is here, 9 MB].
• Map covers area of The Netherlands to Heilbronn/Germany. Map is marked with location of Tagjagdstellungen and Fu.M.G. sites (1., 2., and 3. Ordnung; dunajafähig vs. nicht dunajafähig).
• Map size ca 3x2 (WxH) sheets of size A4. Map scale 1:1.000.000
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL-3-1527.
• Ref. 244N: "Jagd-Einsatz im November 1943", Anlage 3 (appendix 3) to "Lfl.Kdo3, Führ.Abt(1)/1c No. 15684/43 Kdos". [file size: 19 MB]
• Large bar graph for each day of November 1943, with total number of fighter sorties for each day, split into "day" and "night" fighter. Also: table with statistics for each day: number (with type(s) of aircraft) for each type of sortie/mission: "Alarmstart" / "Überwachung und Sperre" / "Geleitschutz" / "Begleitschutz u. Augnahme"; / "Nachtjagd" (night fighter) / "Fernjagd" (long range intercept); also: total number of sorties/missions, number of enemy kills (incl. type of enemy aircraft), own losses.
• Size: size: ca. 3x3½ (WxH) A4-sheets.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL-3-1527.
• Ref. 244P: "Abschüsse der Nachtjagd im Bereich Luftwaffenbefehlshaber Mitte", Anlage 2 (appendix 2).
• Graph with three lines: "hell" (helle Nachtjagd), "dunkel" (dunkle Nachtjagd), "kombiniert" (kombinierte Nachtjagd). Graph covers monthly statistics regarding enemy kills for the period April 1941 - March 1942.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL-3-1527.
• Ref. 244Q: "Anzahl der voll u. bedingt (ab Juli 1941) bzw. eingeschränkt (ab Mai 1943) einsatzfähigern Besatzungen" and "Anzahl der einsatzbereiten Kampf-Flugzeuge" .  [file size: 17 MB]
• Graph with monthly statistics for the period mid-1939 - mid-1939: number of available flight crews and number of operational fighter planes), separate curves for "Tagjäger" (day fighters) and "Nachtjäger" (night fighters; from late 1940 onward).
• Also: interesting large table with 53 key dates of the WW2, from 1 September 1939 (German invasion of Poland) through 15 August 1944 (anglo-american landing in southern France).
• Size: ca. 1½ x3 (WxH) A4-sheets.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL-3-1527.
• Ref. 244R: "Fighter defence of Germany - Control of fighters by the "Y" Procedure", Samuel Denys Felkin (Chief Interrogator at Bletchley), transcribed report from the British Air Ministry, Assistant Director of Intelligence (Prisoner Interrogation), A.D.I. (K) Report No. 525/1944, 14 pp. Source: The National Archives of the UK, ref. AIR40/2875 and 2876. Retrieved from www.cdvandt.org.
• Ref. 244S: "Das "Y-Verfahren" für Tag- und Nacht-Jagd (Navigations-Verfahren)" ["The Y-Procedure for day and night fighter control (navigation method)"], author unknown, date & place unknown, 114 pp. The 1960s file coversheet of the Militärgeschichtliches Forschungsamt (Research Office for Military History) suggests that it dates to 1940/41, 114 pp. [file size: : 82 MB !!!! - with reduced resolution]
• Keywords: Y-Verfahren, Y-Führung, Y-Stelle, Y-Stellung, Y-Anlage, Y-Station, Y-Einrichtung, E 16, FuG 16, Graetz-E-Mess-Gestell, Siemens-E-Mess-Gestell, Heinrich Peiler, ZVG 16, ZE ZY Zeiger, Schildkröte, PQK, S 16.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) RL 2-V/38, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 244T: "Die Deutschen Nachtjagdverfahren" ["The German nigh fighter procedures"], Walter Grabmann, Generalmajor a.D., date unknown, 22 pp.
  [Helle Objektjagd, helle Gebietsjagd, Himmelbett, Verfolgungsnachtjagd [pursuit night], Objektjagd "Leichentuch" / "Milchglas", 1-mot Objektjagd "Wilde Sau", Fernnachtjagd [long-range night], Zusammenarbeit mit Jäger-Flak, 13 maps].
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, file nr. (Signatur) ZA 3/402a, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 253: antenna directivity
• Ref. 253A: "Berechnung der Charakteristik von Richtantennen" [calculation of radiation pattern of directional antennas, free-space and with ground influence], A. Engel, Berlin, 15 pp., in "Ringbuch der Luftfahrttechnik", Vol. 15: V. Ausrüstung, C. Funkpeilung, 4. Berlin-Adlershof, Zentrale f. wiss. Berichtswesen b. d. Deutschen Versuchsanst. f. Luftfahrt, 1938. [file size: 25 MB]
• Ref. 253B: "50 Jahre Antennentechnik" [Telefunken, incl. dipole arrays with reflectors, patents], W. Berndt, pp. 197-204 in "50 Jahre Telefunken - Festschrift zum 50 jährigen Jubileum der Telefunken Gesellschaft für drahtlose Telegraphy m.b.h. - Gleichzeitig als 100. Ausgabe der Telefunken Zeitung", Vol. 26, Nr. 100, May 1953, 164 pp. Source: nvhrbiblio.nl, retrieved 19 February 2020.
• Ref. 265: "The composition and friction-reducing properties of leaf layers", Michael Watson, Benjamin White, Joseph Lanigan,Tom Slatter, Roger Lewis, in "Proceedings of the Royal Society A", Vol. 476, Issue 2239, 29 July 2020, pp. 34 pp. [pdf]
• Ref. 282: papers about Luftwaffe transmission via radio of enemy aircraft positions.
• Ref. 282A: "Feindreportagen" ["Running commentary on enemy aircraft"] and "Bernhard-Führung" ["Bernhard guidance"], §II and §VII, respectively, in "Nachrichtenbefehl April 1945 (Nachtjagd)", 1. Jaddivision, Nafü 3 - Nr. 2600/45, 18 March 1945, 5 pp.
• Keywords: Verfolgungsnachtjagd, Führungswellen, Gruppenbefehlswellen, Geschwaderbefehlswellen UKW (Tast) Bord-Bord, Divisionsführungswellen Lgw, Kzw, UKW der 1.J.Div., Divisionsklärungswellen (Tast), Y-Linienverteilung für Aufklärer, Y-Linien für 1-mot. Nachtjagd, Mosquito-Jagd (Silber), Feindreportagen, Kennung für Fu. G 25, Rufzeichen und Rufnamen, Optische Gruppenkennung und Wellen für flg. Funkfeuer, Verschlüsselung eigener Standort- und Flughöhenangaben, Gebietsnachtjagd, Flugsicherung.
• Source: Bestand/File 500, Findbuch/Index 12476, Akte/record 90, pages 31-36 of the German-Russian Project for the Digitization of German Documents in Archives of the Russian Federation. Retrieved November 2021.
• Ref. 282B: "Funkübermittlung der feindlichen Luftlage – Auszug aus einem Bericht des Obst. Morgenstern, Chef beim Generalnachrichtenführer vom 22.3.1945" ["Radio transmission of the enemy air situation (aircraft positions) – Excerpt from a report dated 22 March 1945 of Col. Morgenstern, Chief adjoint to the lead Signal Corps General"], Gen.Nafür (1. Abt.) Nr.11 319/45 geh., 9 pp.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, (Signatur) file nr. ZA 3/402, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 282C: "Die Bildung der Luftlage. 1935 – 1944 (Flugmeldedienst, Funkmeßdienst, Funkaufklärung)" ["The creation of (enemy) air situation (aircraft position status). 1935 – 1944 (enemy aircraft warning service, radar service, radio intelligence service)"], Obst. A.D. Greffrath, 1946, 7 pp.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, (Signatur) file nr. ZA 3/402, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 282D: "Die Bildung der Luftlage" ["The creation of (enemy) air situation (aircraft position status)"], Gen.Maj. a.D. Walter Grabmann, no date - possibly 1946, 10 pp.
• Source: Bundesarchiv-Militärarchiv (BArch-MA, BAMA) Freiburg/Germany, (Signatur) file nr. ZA 3/402, used in accordance with "Erstinformation für Ihren Besuch im Bundesarchiv in Freiburg, Stand Juni 2016".
• Ref. 283: Philips transmitter vacuum tubes, NSF/Philips (beacon) transmitters, NSF/Philips companies:
• Ref. 283A: pp. 320, 321 in "Zendbuizen" ["Transmitter tubes"], J.P. Heyboer, Vol VII of "Electronenbuizen" ["Vacuum tubes"], Philips Technische Bibliotheek, N.V. Philips' Gloeilampenfabrieken, Meulenhoff & Co. N.V. (publ.), 1946, 321 pp. Source: frank.pocnet.net, retrieved 11 May 2022.
• Ref. 283B: "Philips zendlamp PA 12/15", Philips transmitter tube datasheet, 2 pp. Source: frank.pocnet.net, retrieved 11 May 2022.
• Ref. 283C: pp. 209-211 in "Spanne en Spanningen - De veertigjarige geschiedenis van de n.v. Philips’ Telecommunicatie Industrie voorheen n.v. Nederlandsche Seintoestellen Fabriek” ["The 40 years history of Philips Telecom Industries, formerly NSF"], Willem Vogt, 1958, 354 pp. Source: nvhrbiblio.nl, retrieved 24 May 2022.
• Ref. 283D: "Radio landing beacons for aerodromes", P. Zijlstra, in "Philips Technical Review", Vol. 2, No. 12, December 1937, pp. 370-376. Source: nvhrbiblio.nl. Dutch version is in "Philips Technisch Tijdschrift", Vol. 2, Nr. 12, December 1937.
• Ref. 283E: "Position finding and course plotting on board an aeroplane by means of radio" [incl. V.P.K. 35, B.R.A. 101], G.P. Ittmann, in "Philips Technical Review", Vol. 2, No. 6, June 1937, pp. 182-190. Source: nvhrbiblio.nl.
• Ref. 283F: "The Philips ultra short wave radio beacon type B.R.A. 075/4", P. Zijlstra, in "Philips Transmitting News", Vol. 4, No. 6, December 1937, pp. ???.
• Ref. 283G: "Philips ultra shortwave beacon type B.R.A. 200/8" [NSF], R.F. Volz, A.G. de Jager, in "Philips Transmitting News", Vol. 5, No. 4, December 1938, pp. ???
• Ref. 283H: "Some theoretical considerations on the Philips short wave radio beacon" [NSF], P. Zijlstra, in "Philips Transmitting News", Vol. 6, No. 3/4, December 1939, pp. ???
• Ref. 292: "Führungs- und Navigationsverfahren, Bordfunksprech- und Bordfunknavigationsgeräte, Bordfunkmeßgeräte, Eigener und feindlicher Hochfrequenzeinsatz, Störsender, feindliche Bordfunkmeßgeräte, Feindliche Navigationsverfahren, Stand 1.1.1945", 6 pp. Source: TBD.
• Tables: Guidance & navigation methods (UKW-Peiler; Y-Anlage; Egon; Bernhard-Anlage; Jagdhütte; Bodentruhe-Anlage; Sonne-Anlage); Radio telephony & navigation equipment (FuG 16ZY; FuG 15, FuG 125; FuG 24 SE; FuG 120, FuG 130, FuG 29, FuG 123); On-board radar (FuG 220 / Li SN2; FuG 228 / Li SN3; FuG 218 VR / Neptun VR; FuG 218 QR / Neptun QR; FuG 240 / Berlin N 1a; FuG 244 / Bremen O; FuG 200 / Hohentwiel; FuG 224 / Berlin A; FuG 217 / Neptun RII; FuG 25a / Erstling; FuG 227 I-III / Flensburg; FuG 350 Z/ZX, Naxos Z/ZX, Naxos ZR; FuG 280 / Kiel; Falter), Luftlageaufklärung (Wassermann MI-MY, Elefant, Klein Heidelberg, Freya, Würzburg Riese, Jagdschloß, Forsthaus F, Jagdschloß Michael B, Jagdschloß Z / Forsthaus Z, Jagdwagen, Korfu/Naxos/Naxburg); Jammers (Heinrich I & II, Karl I & II, Feuerstein I & II, Feuerzange, Feuerhilfe, Feuerland I, Abfrage-Ballstörgerät, Roland I & II, Klystron Röhre); Enemy on-board radar (Rotterdam/Rotterdam-X/Belfort/Meddo, ASV/ASD/Rotterdam, Luchs/Grille/Frankfurt, Monica/Luchs/Fish Pond, Village-Inn); Enemy radio navigation systems (Hyperbel, Long Range, Bumerang, Diskus, Mikro-M). Status of 1 January 1945.

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External links last checked: October 2015 unless noted otherwise.