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By January of 2019 this page had grown to 125 photos and diagrams. It had become rather large (ca. 18 MB download size), which caused long download times for some users. I decided to split the page in two: equipment items remain on this page, general introduction and printers have moved to a separate page. Please continue using the (unchanged) items lists above, and update your bookmarks accordingly.


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


Latest page update: 1 January 2023 (added Fig. and ref. 249E)

Previous updates: May-June 2022 (added Fig 86B, ref. 10, Fig. 68B, replaced Fig. 87, 88, added Fig. 2B & 69A, added ref- 11 & Fig. xx); March-April 2022 (expanded the "Aircraft equipped with FuG 120" section; incl. Fig. 107C, replaced Fig. 122).Februay 2022 (aded Fig. 106A + text, ref. 281); December 2021 (added Fig. 128); November 2020 (added Fig. 106A and text, expanded Fig. 107A, added Fig. 107B); August 2020 (added Fig. 95B); February 2020 (added ref. ref. 249B, 249C, Fig. 118); October-November 2019 (added ref. 248, 249A, 256 and associated text, added high-res version of ref. 15); September 2019 (added patent nr. 754395)


red-blue line

OVERVIEW

The FuG 120 "Bernhardine" printer system is the airborne counterpart of the FuSAn 724/725 "Bernhard" radio-navigation beacon of the Luftwaffe, 1941-45. It uses the standard on-board EBL3 VHF receiver that was already used with other beacon systems during "blind" approach and landing, and in combination with beam systems for guiding bombers and fighter aircraft to their target. The printer system provided the operator with the bearing from the selected "Bernhard" ground station, and could also receive short "Reportage" text messages with information about enemy aircraft. The official German designation says it all: the FuG 120 is a "UKW-Richtstrahl-Drehfunkfeuer-Empfangszusatz mit Kommandoübertragung". That is, a VHF directional rotating-beam receiver-accessory with command data-link.

Bernhard Bernhardine system diagram

Fig. 1: "Bernhardine" airborne Hellschreiber printer of the "Bernhard/Bernhardine" radio-navigation system

(click here for a full size image)

The FuG 120 "Bernhardine" system comprises the following equipment items (ref. 4, 5, 15, 42, 43, 44, 85B/C/D):

  • SV 120 printer amplifier unit ("Schreibverstärker"),
  • SG 120 audio filter unit ("Siebgerät", "Schreibgabelschaltung"),
  • UG 120 switching unit ("Umschaltgerät"),
  • SpKf 1a mode switch ("Sprechknopf"), system mode-switch (landing beacon vs. "Bernhard" navigation-beacon); modified PPT-switch ("push to talk")
  • U 120 power supply unit ("Umformer"),
  • HS120 dual-trace Hellschreiber printer ("Hell-Schreiber") or Psch 120 ("Peilschreiber" = bearing-printer, also a Hellschreiber).

HS120 Psch120 mfr

Table-1: manufacturers of the HS 120 (Dr.Ing. Hell company) and Psch 120 (Siemens & Halske LGW)

(source: ref. 44)

According to ref. 44 (p. 188), most of these equipment items date back to 1941, with the exception of SpKf1a (1942), Psch 120 (1942), and SV 120 (1944). However, ref. 2B suggests that series production did not start until 1943, and also states that the first "Bernhard" ground stations were built in 1942.

FuBl test rack

Fig. 2: Test rack with FuBl 2 navigation receiver system (left) and rack with FuG 120 "Bernhardine"

(source: Fig. 39 in ref. 181, Fig. 6 in ref. 183, p. 99 in ref. 2B)

Of course, the aircraft installation included a number of mounting frames and interconnect items (besides cables):

  • RDFS 120, "Rahmen für Drehfunkschreiber": mounting frame for rotating-beacon printer,
  • UF 120, "Umformerfußplatte": mounting plate for power converter U 120,
  • RSV 120, "Rahmen für Schreibverstärker": mounting frame for printer amplifier SV 120,
  • SGF 120, "Siebgerät-Fußplatte": mounting plate for filter unit SG 120,
  • VD 120, "Verteilerdose": junction box,
  • ZLK VIII S 3, "Zwischenleitungskupplung": splitter/coupler unit.

FuG120 connections

Fig. 2B: Inter-unit wiring diagram of the FuG 120

(source: adapted from Fig. ref. 10)

The equipment items UG120, SV120, U120, as well as the installation items RDFS 120, UF120, SGF 120, RSV 120, and VD 120, were all manufactured by a Telefunken plant in Berlin-Zehlendorf (same part of Berlin as the Hell company) or in Erfurt. The associated 3-letter military manufacturer code is "bou". The SG 120 filter unit was manufactured by Siemens Luftfahrtgerätewerk (LGW) Hakenfelde GmbH, manufacturer code "eas". The SpKf1a mode-switch and the ZLK VIII S 3 coupler-unit were made by Frieseke & Höpfner, Spezialwerke für Flugfunktechnik in Berlin Potsdam-Babelsberg and in Breslau. Their manufacturer code was "gqd" (p. 188 in ref. 51).

The total weight of the FuG 120 units (incl. mounting frames) is about 38 kg (84 lbs).

In addition to the on-board equipment, there was a number of ground-test equipment items (ref. 15, 44, 45), mostly built by Telefunken (p. 188 in ref. 44):

  • TOG 120, "Tongenerator": an audio signal generator,
  • PV 120 and PV 64, "Prüfvoltmeter",
  • PschMG 120, "Peilschreibmeßgerät", a tester for the Hellschreiber printer,
  • PS 120, "Prüfsender": transmitter / signal generator to test the complete functionality of the FuBL2 plus FuG120. This implies a "Bernhard" beacon simulator,
  • PGst 120, Prüfgestell, a test rack (possibly such as shown in Figure 2 above).


PRINTER AMPLIFIER SV 120 (SCHREIBVERSTÄRKER)

The SV 120 ("Schreibverstärker") is the dual-channel printer amplifier unit of the FuG 120. All Hellschreibers require a "tone-detector plus printer-solenoid driver-amplifier" (see Figure 66). It converts received tone-pulses into energization pulses for the electro-magnets of the printer. The audio input signal is amplified, band-pass filtered, rectified. A final amplifier acts as a power-switch.

Hellschreiber printer-driver basic schematic

Fig. 66: Simplified principle diagram of a standard Hellschreiber printer-amplifier channel


However, the SV 120 is much more than just two such channels - see Figure 69. In total, there are 13 tubes (valves): five RV 12 P 2000 pentodes, five LV1 low-noise power pentodes, and three LG6 dual-diodes (full-wave rectifiers).

SV 120 tubes

Fig. 67: SV120 tubes RV12P2000, LV1, and LG6 (to the same scale)


SV 120

Fig. 68A: The SV 120 printer amplifier

(source: Fig. 10 and 11 in ref. 200; note the hinged cover on the three rectifiers, one is flipped down)

SV 120

Fig. 68B: Inside of the SV 120 printer amplifier

(source: adapted from Fig. 19 in ref. 10)

SV120 diagram

Fig. 69B: Detailed circuit diagram of the SV 120 printer amplifier unit

(source: adapted from Fig. 17 in ref. 10; component list is Fig. 16 in ref. 10)

SV120 diagram

Fig. 69B: Simplified principle diagram of the SV 120 printer amplifier unit

(source: adapted from Appendix-b in ref. 15)

Let's walk through the above block diagram. The first block is the pre-amplifier with one RV 12 P 2000 pentode tube (valve):

  • The input is audio from the EBl 3 receiver.
  • The volume control potentiometer is located on the HS 120 printer unit.
  • The output of the pre-amp goes to a separate dual-channel audio filter unit, the SG 120.

FuG120 pre-amp filter channel

Fig. 70: Pre-amplifier and filter


In the SV 120, the two audio outputs from the filter unit are passed through separate two-stage amplifiers. Each amplifier comprises an RV 12 P 2000 pentode followed by an LV 1 pentode.

The output of the 2-stage amplifier for the bar-graph printer is transformer-coupled to two other stages:

  • One for the 1800 Hz constant tone - for the bar-graph printer.
  • One for the 2600 Hz Hellschreiber tone pulses - for the azimuth printer.

The output of the 2-stage amplifier for the bar-graph printer is transformer-coupled to two other stages, see Figure 71:

  • An Automatic Gain Control (AGC) stage. Its output goes back to the EBL 3 receiver. Remember that the purpose of this printer channel is to print the strength of the signal from the twin-beam of the Bernhard beacon. This AGC has a short attack time, and a very long decay time. These time constants ensure that the AGC-signal is fairly constant during the entire passage of the beam (3-5 sec), so as not to distort the sharp signal minimum between the two main beam-lobes. It also ensures that side-lobes and rear-lobes of the antenna pattern do not cause the printer motor printer magnets to be enabled. Via the AGC, the side- and rear-lobes actually help prevent the receiver gain from becoming too high. The gain of the AGC-amplifier is high, and a threshold is applied at the input. This AGC makes the performance of "Bernhardine" relatively independent of the distance to the beacon.
  • A rectifier/amplifier. Here, the amplitude of the received 1800 Hz tone is first converted to a DC voltage level. Then a sawtooth signal is added, and finally a fixed bias voltage is added. The summed voltages are input to the control grid amplifier tube. This tube acts as a switch, with a small hysteresis. This effectively converts the amplitude of the tone signal to the width ( = duration) of pulses. These pulses are amplified and used to energize the printer-magnet of the bar-graph printer. For a pulse with maximum duration, the printer prints a full-height bar. In absence a pulse (zero width), no bar is printed. The required sawtooth signal is generated by quickly charging a capacitor via a contact that is actuated by a notched wheel on the shaft of the printer-spindle. The capacitor is discharged via a choke coil. The principle schematic of this pulse-width modulator is discussed here.

FuG120 bar-graph channel

Fig. 71: Receiver-AGC and bar-graph printer driver


The output of the 2-stage amplifier for the azimuth printer is transformer-coupled to three other stages, see Figure 72:

  • An Automatic Gain Control (AGC) stage. Its output goes to the first tube of this 2-stage amplifier. The AGC keeps the signal level of the received 2600 Hz Hellschreiber tone pulses (azimuth data) constant.
  • A rectifier/amplifier. Here, the received 2600 Hz tone pulses are rectified. The rectified pulses turn the driver-amplifier on/off, to energize both the printer-magnet of the azimuth printer, and the synchronization magnet-solenoid.
  • A second rectifier/amplifier. This detector is used to start and stop the entire HS 120 printer. Via relay contacts, the motor is turned on, the anode voltage of the two printer-solenoid driver tubes is enabled, and the AGC output to the EBL 3 receiver is enabled. The detector has a hang-time of 1.5 sec, to avoid that the relay de-energizes the system too quickly when the audio signal levels go down. The purpose of this, is to only print (and use paper) when the main beams of the beacon are being received. Once the bar-graph and compass rose segment are printed, the paper does not move until the next beam passage, some 30 seconds later. This makes it easier for the crew to read the print-out.
    • Ref. patent 767527 proposes "a simple method" for start-stop control of the printer system, without using complicated things such as AGC. This involves a notched disk that is "somehow" closely synchronized to the rotation of the beacon's antenna system. The width of the notch corresponds to that the azimuth segment of interest. It actuates a switch that enables the printer. The position of the switch is adjustable, so as to be able to pre-select the azimuth segment. This patent has two weak points: 1) undefined synchronization method that is simpler than AGC, and 2) to be able to adjust the switch position, the bearing must already be known - which defeats the purpose of this method.
FuG120 azim channel

Fig. 72: AGC and printer-magnet drivers for the azimuth printer


According to patent 767354, the field-strength of the received continuous signal could vary as much as 1:10000 (80 dB amplitude ratio) between maximum and the deep null, necessitating a receiver/filter characteristic with compressing/limiting gain curve. The received signal strength obviously depends on the altitude of the aircraft and its distance (range) from the beacon. Patent 767526 foresees an automatic gain control, using yet a third signal transmitted by the ground-station, via an omni-directional antenna system. However, this was never implemented in the Bernhard/Bernhardine system.

As noted  in the "Evolution of the "Bernhardine" printer" section, the the SV120 printer amplifier unit and the Printator disk printer were originally (October 1940) to be developed as an improved cockpit instrument that was needed for testing with the "Knickebein" beam system (ref. 204A, 204F). The Telefunken-internal codename for the printer-amplifier was "Ulrich" (ref. 181, p. 83):

Bernhardine time-line patents

Fig. 73: The SV120 originally had the Telefunken code name "Ulrich"

(sources: Fig. 41 & p. 83 in ref. 181, Fig. 4 in 183)


FILTER UNIT SG 120 (SIEBGERÄT)

The "Bernhard" navigation beacon has two AM transmitters. Their carrier frequencies were spaced 10 kHz (±1 kHz). One carrier was modulated with a constant 1800 Hz tone. This creates sidebands at 1800 Hz above and below the carrier frequency. The second carrier was modulated with a 2600 Hz tone. Hence, this carrier also has sidebands: 2600 Hz above and below the carrier frequency. However, the 2600 Hz tone was on-off-keyed with Hellschreiber-pulses. So, each of the 2600 Hz sidebands itself has an infinite Fourier-series of sidebands. As these tone pulses are not a square-wave, the latter sidebands are not individual frequencies (like a comb), but are "smeared" into half sine-wave envelopes. See Figure 74. The tone-pulse transmitter limits the bandwidth of the sidebands to 400 Hz. This is sufficient to pass the 2nd harmonic of the tone pulses (≈350 Hz), and guarantee proper printing.

RF and audio spectra

Fig. 74: Nominal RF spectrum of the "Bernhard" transmitter outputs

(source: frequencies taken from ref. 15, ref. 181)

The FuG120 "Bernhardine" is operated in combination with an EBL3 shortwave AM navigation receiver. The audio output of the EBL3 contains both the constant 1800 Hz tone from the "Bernhard" beacon's twin-lobe beam and the 2600 Hz Hellschreiber tone pulses that represent the azimuth symbology, as well as the 9-11 kHz (10 kHz nominal) difference between the carrier frequencies of the two "Bernhard" transmitters, ref. 15 (p. 10 = pdf p. 11):

RF and audio spectra

Fig. 75: Audio spectrum of the EBl 3 receiver output


To the best of my knowledge, no original "Bernhard" audio recordings exist today. So I have simulated the sound of a transmission. The recording below comprises two beam-passages: once without the information in Hellschreiber-format (i.e., only the constant 1800 Hz tone), and once the constant tone plus the constant stream of 2600 Hz Hellschreiber-pulses. Note: the second simulated beam passage also includes a 10 kHz tone. As explained above and shown in Fig. 75, this is the normal byproduct of demodulating those two simultaneous AM signals.


Bernhard sound

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


The detector-amplifiers of the the two "Bernhardine" Hellschreiber printers respond to all audio signals that have sufficient amplitude - including noise. But the bar-graph printer should only respond to the 1800 Hz tone signal, and the azimuth printer only to the 2600 Hz signal. This means that the two detector-amplifiers must each be preceded by a filter that only passes the tone frequency of interest. The two required bandpass filters are located in the 2-channel SG 120 ("Siebgerät") audio filter unit. This unit has the Luftwaffe Gerät-Nummer 124-977-A (ref. 15). The unit measures 22.5x16.7x9.3 cm (WxHxD, ≈ 9x6.6x3.7 inch) and weighs about 7 kg (≈ 15.5 lbs); ref. 15, 212.

SG120 block diagram

Fig. 76: The SG120 2-channel audio filter unit - cover removed

(source: Fig. 12 in ref. 200; the three large metal-shielded boxes contain the seven inductor coils)

SG120 block diagram

Fig. 77: Block-diagram of the SG120 2-channel audio filter unit

(source: adapted from ref. 15)

Each filter channel comprises a number of series and/or parallel LC-circuits, of which two pairs are stagger-tuned: two parallel-LC circuits in series, or two series-LC circuits in parallel, with slightly different resonance frequencies. The bandpass filter for the Hellschreiber tone pulses has a bandwidth of 400 Hz (ref. 15). Obviously, the center-frequency of the two bandpass filters is the same as the modulation tones of the transmitters: 1800 and 2600 Hz, respectively. Unfortunately, the manual (ref. 15) only list the values of all the capacitors, but not of the seven inductors. So the actual filter characteristics can not be reconstructed (unless an intact SV120 unit is found).

RF and audio spectra

Fig. 78: Audio spectrum of the two SG 120 filter-channel outputs


The two separate tone outputs of the filter unit are returned to the SV120 printer-amplifier unit.

The SG120 was manufactured by Siemens Luftfahrtgerätewerk (LGW) Hakenfelde GmbH (p. 188 in ref. 44). LGW was located in the borough of Berlin-Spandau, just across the Havel river next to Siemensstadt. LGW was a 1940 spin-off of Siemens Apparate und Maschinen GmbH (SAM). Its military manufacturer code was "hdc"; the code "hnu" was used for international (export) products. LGW made a wide variety of aircraft equipment, such as gyros, temperature gauges, radio altimeters, course indicators, switches, connectors, indicator lights, course guidance equipment, and autopilots.


SWITCHING UNIT UG 120 (UMSCHALTGERÄT)

During approach and landing, the EBl 3 beacon receiver works together with the EBl 2 marker-beacon receiver. In this configuration, the EBl 3 receives an automatic gain control (AGC) signal from the EBl 2, and the EBL2 receives the audio frequency (AF) output of the EBl 3. When the EBl 3 is to work with the "Bernhardine" system, the FuG 120 takes the place of the EBl 2. A mode switch controls the UG 120 switching unit. The UG 120 was built by Telefunken (ref. 44, 212). It measures 22.2x20x4 cm (WxDxH, ≈9x8x1.6 inch) and weighs about 0.5 kg (≈1.1 lbs).

This unit is basically a small box with a 4P2T relay (4 sets of changeover contacts):

UG120

Fig. 79: Umschaltgerät UG 120 - switch-box

(source: Fig. 16 and 17 in ref. 200)

UG120 diagram

Fig. 80: Principle diagram of the UG 120 switching unit

(source: adapted from Figure-7 and Appendix E in ref. 15)

The normal cable that connects the EBl 2 and EBl 3, is replaced with two cables that plug into a splitter/coupler unit: the ZLK VIII S 3 ("Zwischenleitungskupplung"). A third cable connects this coupler to the UG 120 switching unit.

The re-configuration is done with the SpKf 1a mode switch. This is a modified SpKf 1 "Sprechknopf" switch. The latter is used to switch a microphone on and off, like a push-to-talk switch (PTT). SpKf 1 has switch positions that are labeled "EIN" (on) and "AUS" (off). Model 1a is a 3-position switch. A white pushbutton enables changing the switch position. The center position is labeled "NFF" ("Navigationsfunkfeuer" = Navigation Beacon). The left & right position are labeled "LFF" ("Landefunkfeuer" = Landing Beacon). In the "LFF" position, the EBl 3 is connected to the EBl 2. In the "NFF" position, the EBl 3 gets its AGC input signal from the FuG 120, and the FuG 120 gets the AF output from the EBl 3. For an example of the SpKf 1a installed in the cockpit of a Messerschmitt Me-262, see Fig. 107 below.

SpKf1a

Fig. 81: The 3-position SpKf1a switch



SpKf1a

Fig. 82: The SpKf1a switch - manufactured by Frieseke & Höpfner

(source: ref. 44)


The SpKf 1a mode switch (Ln28986) and ZLKVIII coupler were manufactured by "Frieseke & Höpfner, Spezialwerke für Flugfunktechnik" in Berlin Potsdam-Babelsberg and in Breslau. Their manufacturer code was "gqd" (p. 188 in ref. 51). The switch measures 3.5x3.7x5 cm (WxHxD, ≈1.4x1.5x2 inch inch) and weighs 40 grams (1.4 oz.). This company also made other on-board equipment such as amplifiers of type V3 (of the FuG 125a) and V6, mounting frames VR3, VRP6, RSSF6, automatic DF attachment APZ6 (part of Funkpeilsystem EZ6), loop antenna switches RSS6 & RDS6, electro-mechanical DC-DC converter VZ6, and test equipment such as the PK6 and PGV6. Ref. 212.


F&H letterhead

Fig. 83: Letterhead of the Frieseke & Höpfner company (1945)



POWER SUPPLY U 120 (UMFORMER)

The U 120 is the central high-voltage DC power supply of the FuG120 system. It primarily supplies the anode and grid-bias voltages for the tubes in the the SV 120 amplifier unit. The unit measures 34.2x22.5x16.4 cm (WxHxD, ≈13x9x6.5 inch) and weighs about 12 kg (≈26.5 lbs); ref. 15, 212.

At the heart of the U 120 is an "Einanker Umformer": a single-rotor motor-generator-alternator (MGA). It generates 300 VDC and 17 VAC. Its 24 VDC motor is powered by the standard 28.5 VDC aircraft electrical system (note: 28.5 VDC is the normal charging voltage for 24 VDC lead-acid batteries, like 13.8 is for 12 VDC lead-acid batteries). All internal connections to and from the MGA are passed through line-filters, to suppress commutator noise. The MGA, model ZA-FGGW 95b 60, was manufactured by the Ziehl-Abegg company of Berlin-Weißensee. This company also made motors for the electric locomotives of the "Bernhard" ground station.


U120 diagram

Fig. 84: Principle diagram of the U 120 power supply of the FuG 120

(source: derived from Appendix-d of ref. 15)

The U 120 has five outputs. They all go to the SV 120 amplifier unit. The 300 VDC generator output is used for three of the five outputs:

  • 300 VDC is taken directly from the 300 VDC generator, and is not stabilized. It used as anode voltage for the printer driver tubes (final amps) in the SV 120. Upon power-up, this output is kept disabled ("open") with a time-delay relay, until the rectifier tube for the 280 VDC grid bias voltage (derived from the 17 VAC) has warmed up. This is done to avoid damage to the driver tubes, and to avoid the HS 120 Hellschreiber from starting up inadvertently.
  • 280 VDC is obtained by passing the 300 VDC through a choke coil and a filter capacitor. It is used as the anode voltage for all other tubes in the SV 120.
  • 140 VDC is the grid-bias voltage for the tubes in the SV 120. It is derived from the 280 VDC with a voltage stabilizer tube Metall Stabilovolt type M STV 140/60 Z. The voltage across this stabilizer is 140 Volt at a nominal stabilizing current of 35 mA (65 mA max). This tube is also know as the LK121, where L = "Luftfahrtröhre" (aviation tube) and K stands for "Konstanthalter" = stabilizer, ref. 57. This tube contains two 70 volt gas "glow" discharge stabilizers in series. Likewise, the STV280/40 contains four such stabilizers in series (with individual output pins).

U120 diagram

Fig. 85: LG6 tube and Metall Stabilovolt M STV 140/60 Z tube (without extraction knob)


The 17 VAC from the alternator is passed through a transformer. The transformer has four secondaries. Two of the secondaries are up-transformed. Each is full-wave rectified with an LG 6 dual-diode (nominal 400 volt and 100 mA). Here again L = "Luftfahrtröhre", whereas G stands for "Gleichrichter" = rectifier. This tube was originally developed by Philips.

  • 280 VDC is obtained by filtering the output of one of the two rectifiers. It is stabilized with two 140 Volt stabilizer tubes in series. This voltage is used as grid bias for the printer driver tubes in the SV 120.
  • 140 VDC is obtained by filtering the output of the second rectifier. It is stabilized with a single 140 Volt stabilizer tube. This is used as the bias voltage of the sawtooth signal generator circuit in the SV 120.

The other two secondary voltages are down-transformed, to provide the required 12.6 VAC heater voltage for these two rectifiers.


U120 diagram

Fig. 86A: The U 120 power supply - cover removed

(source: Fig. 23 in ref. 200 - transformer cover and motor fan cap also removed; also: Fig. 9 in ref. 201)

U120 open

Fig. 86B: The U 120 power supply - cover removed

(source: adapted from Fig. 14 in ref. 10)

U120 diagram

Fig. 86C: Equipment label on a U 120 power supply

(source original unedited photo: ©2018 Dufleuve; used with permission)

U120 diagram

Fig. 86D: U 120 power supply - top view, cover removed

(source original unedited photo: ©2018 Dufleuve; used with permission)

U120 diagram

Fig. 86E: U 120 power supply - front view, cover removed

(source original unedited photo: ©2018 Dufleuve; used with permission)


FuG 120 EQUIPMENT MOUNTING FRAMES

The FuG 120 system comprised the following mounting frames:

  • RPsch 120a, "Rahmen für Peilschreiber": mounting frame for a Psch 120(a) bearing printer,
  • This is the same as the RDFS 120, "Rahmen für Drehfunkschreiber": lit. mounting frame for rotating-beacon printer,
  • UF 120, "Umformerfußplatte": mounting plate for power converter U 120,
  • RSV 120, "Rahmen für Schreibverstärker": mounting frame for printer amplifier SV 120,
  • SGF 120, "Siebgerät-Fußplatte": mounting plate for filter unit SG 120.

As shown in Fig. 87 below, the HS 120 printer was not mounted on a frame: the four lugs on the back of the HS 120 were mounted directly onto four shock mounts, to mechanically isolate the printer from shocks and vibration.

The FuG 120 "Bernhardine" system includes the following interconnection items (incl. for connections with the FuBl 2 beacon receiver radio system):

  • ZLK VIII S 3, "Zwischenleitungskupplung": splitter/coupler unit.
  • VD 120, "Verteilerdose": junction box,
  • Eight custom cables (including connectors), with the following numbers ("Leitung-Nummer"), ref. 15:
  • 371F, 372F (1 conductor),
  • 373F, 378F (12 conductors),
  • 374F - 376F (8 conductors),
  • 377F (2 conductors).

The FuG 120 system test rack includes all of the mounting frames and interconnect items listed above, as well as test rack specific cables ("Prüftafel-Verbindungsleitung", "Hellschreiber-Prüfleitung"):

FuG 120 frames

Fig. 87: Prüfgestell PGst 120 with HS120, and PGst 120a with both HS120 and Psch120

(source: left - Fig. 39 in ref. 181 ( = Fig. 6 in ref. 183), and Fig. 13 & 14 in ref. 10)

The test rack was made by Telefunken, measures 58x82 cm (WxH, ≈23x32 inch), and weighs about 22 kg (≈49 lbs), ref. 212. Note that through 1943 (ref. 181, 183), the test rack only accommodated an HS 120 printer, but the 1944 rack both an HS 120 and a Psch 120 printer (ref. 203):


FuG 120 frames

Fig. 88: Prüfgestell PGst 120a - FuG 120a system test rack with & without equipment set and rear view

(sources: adapted from (left to right) Fig. 10, 9, and 11 in ref. 203)


The mounting from for the The RPSch 120a (also written as RP.Sch.120A) is the mounting frame for the PSch120(a) "Peilschreiber". The frame measured 16.7x18.6 cm (≈6.6x7.3 inch) and weighed about 320 gram (≈0.7 lbs); ref. 212. It has four black rubber "anti vibration" shock mounts.

FuG 120 frames

Fig. 89: RPsch 120a - mounting frame for the Psch 120(a) printer (same as RDFS 120)

(source: Fig. 4 in ref. 189A)

FuG 120 frames

Fig. 90: Top and bottom of an RPsch 120a

(source: eBay)

FuG 120 frames

Fig. 91: Label and manufacturer markings on the above RPsch 120a

(source: eBay art. nr. 201963118195)


The metal frame of the RPSch 120a was manufactured for Siemens & Halske AG by the Nürnberger Aluminiumwerke GmbH, tradename Nüral (esp. for engine pistons). This company was founded in 1924. In 1962, it merged with Aluminiumwerke Göttingen GmbH (founded in 1909 as Aluminium Werke Carl Albracht, acquired in 1930 by Aluminum Company of Canada (Alcan)), to form Alcan Aluminiumwerke GmbH. During the 1990s, it was absorbed into the US-based Federal-Mogul company. Ref. 213.

Feld-Hell

Fig. 92: advertising for Nüral die-cast engine blocks and pistons  (1940 and 1947)


In the three mounting frame photos below, note that besides two mounting hooks to hang the equipment, each frame as a keying pin ("Sperrstift"). Each pin is placed at a location that is specific to the equipment to be installed on the frame. That equipment has a hole at the corresponding location. This precludes inadvertent installation of different equipment that would otherwise fit on the frame.

FuG 120 frames

Fig. 93: Rahmen RSV 120 - mounting frame for the SV 120 printer amplifier

(source: Fig. 20 in ref. 200)

FuG 120 frames

Fig. 94: Rahmen SGF 120 - mounting frame for the SG 120 filter unit

(source: Fig. 21 in ref. 200)

FuG 120 frames

Fig. 95: Front of Fußplatte UF 120 - mounting frame for the U 120 power supply

(source: Fig. 22 in ref. 200)

FuG 120 frames

Fig. 95: Rear of a Fußplatte UF 120 - note the manufacturer's logo boss "CE" of "Elektronmetall Cansstatt"

(source: eBay article 333667088862, 2020)

FuG 120 frames

Fig. 96: Verteilerdose VD 120 - junction/distribution box

(source: Fig. 18 and 19 in ref. 200)

The VD 120 carries the Ln item nr. 28984 (see the right-hand photo above). It is basically identical to the VD 3 of the  "Peil G IV" airborne radio direction finder system. The only difference appears to be the rating of the internal fuse. It is also very similar to the VD 4 (Ln nr. 26934) of radio equipment sets such as the FuG 10 K and FuG 16 ZY, though the VD 4 has an additional antenna cable connection.

There also was another junction/distribution box: Verteilerkasten VK 120 a, for the FuG 120 a configuration. Ref. 212, 236.



FuG 120 TEST EQUIPMENT

In addition to the on-board equipment, there was a number of ground-test equipment items (ref. 15, 44, 45), mostly built by Telefunken (p. 188 in ref. 44):

  • PS 120, "Prüfsender": transmitter to test the complete functionality of the FuBL2 plus FuG120. This implies a full "Bernhard" beacon simulator.
  • PschMG 120, "Peilschreibmeßgerät", for measuring parameters of Hellschreiber printers.
  • TOG 120, "Tongenerator": an audio signal generator.
  • PV 120 and PV 62, "Prüfvoltmeter": multi-range voltmeters.

The carrying case Prüfgeräte Koffer PK 120 contained the PSchMg 120, TOG 120, PV 120, and PV 62. The case measured ca. 62x45x16 cm (WxHxD, ≈24.6x17.6x6 inch), with an empty weight of ca. 8 kg (≈18 lbs) and 19 kg (≈42 lbs) with equipment. Ref. 212.


The PS 120 "Kurzzeichen Prüfsender" is a complete "Bernhard" beacon simulator: it outputs 30-33.3 MHz radio frequency signals to the EBL3 radio receiver of the on-board FuBL2 radio-navigation system. Hence, it has an antenna connector on the front of the unit (labeled "Antennenbuchse" at the bottom right in Fig. 96). The unit measures 68x51.5x21.9 cm (WxHxD, ≈26.8x20.3x8.6 inch) and weighs about 40 kg (≈88.5 lbs); p. 347 in ref. 212). The unit was made by Telefunken (ref. 44).

FuG 120 test equipment

Fig. 97: Prüfsender PS 120 - test signal generator

(source: Fig. 3 in ref. 202)

FuG 120 test equipment

Fig. 98: rear view of the Prüfsender PS 120 - test signal generator - main cover and module-covers removed

(source: Fig. 4 and 5 in ref. 202: note the notched disk installation at the top center)


The next figure shows a printout that was generated with a PS 120. The paper tape is a little over 4 cm wide, so it was printed with an HS 120 printer.

azimuth track

Fig. 99: Print-out generated with a PS 120

(source: Fig. 2 in ref. 202; the tape is 4 cm wide)

The Hellschreiber pixel sequence for the compass symbology was generated with a rotating notched disk - a standard implementation for Hellschreiber senders. Note that the azimuth trace in the print-out above is repeated every 10 degrees. This is why the notched disk, which is clearly visible in Fig. 100 below, only has about 36 notches. They correspond to the vertical line segments of the letter R, the numerals 3 and 4, and the tick marks for 1, 5, and 10 degrees. As the "Bernhard" beacon rotated at 2 rpm, the disk rotated at 2 rpm x 360°/10° = 72 rpm. The diameter of the disk is about 15.5 cm (≈6 inch), based on photogrammetric analysis of Fig. 97 above.


FuG 120 test equipment

Fig. 100: Close-up of the notched disk module ("Tastgerät" = keying device) of the PS 120

(source: Fig. 5 and 6 in ref. 202)

The PS 120 also had to simulate the 1800 Hz signal of the twin-lobe beam, with its amplitude change during rotation of the "Bernhard" beacon. This could have been done with an appropriately shaped "propeller" in combination with a photocell. However, no such device is visible in the photos. It is not the 12-blade ventilation fan behind the strobe disk: it would have been turning too fast, there is no light bulb + photocell anywhere near it, and the blade shape would have been wrong. Possibly, the envelope of the signal amplitude was simply generated with a slow sine wave, with a large offset:

PS 120 test equipment

Fig. 101: Possible method that was used in the PS 120 to generate the twin-lobe signal strength envelope

(adapted from Fig. 2 in ref. 202)

The required clipping need not have been done in the PS 120, as this was already done in the SV 120 printer amplifier. The compass scale segment printed in Fig. 99 spans 50° and would be covered by two sine wave cycles. The beacon rotates at 12°/sec. Hence, the envelope-modulating sine wave frequency would have been (12°/sec) / 50° ≈ 0.25 Hz.

The designator of the PschMg 120 "Peilschreibmeßgerät" suggests that it was used for measuring certain parameters of Psch 120 / Psch 120a printers. I.e., not for actively testing the printers (by injection of test signals). The unit does not include any measurement instruments. Possibly it is primarily an interface box that was used in combination with other test equipment. The test set was made by Telefunken in Berlin-Zehlendorf. This small unit weighed about 5 kg (≈11 lbs) and measured 28.5x25.4x8.8 cm (≈11x10x3.5 inch). Ref. 212 suggests that it could be mounted in the aircraft, on the same RSV 120 rack as the SV 120 amplifier (which has the same WxH dimensions).


PschMg 120 test equipment

Fig. 102: Peilschreibermeßgerät PschMg 120 - bearing printer test set

(source: Fig. 7 and 8 in ref. 203)


The TOG 120 "Kurzzeichen Tongenerator" tone pulse generator probably produced a selectable 1800 Hz or 2600 Hz sine wave with a manually adjustable amplitude. This would have sufficed to test the SV 120 printer amplifier, the SG 120 dual audio filter unit, and the HS 120 or Psch 120(a) printer. The printer would have printed two solid traces (i.e., without white pixels). The unit was made by Telefunken (ref. 44). The unit measured ca. 19x10x11 cm (HxWxD, ≈7.5x4x4 inch) and weighed 2.1 kg (≈4.6 lbs). Ref. 212.

FuG 120 test equipment

Fig. 103: Tongenerator TOG 120 - tone generator

(source: Fig. 1 and 2 in ref. 203)


The test equipment set included two custom "Prüfvoltmeter" test voltmeters: the simple PV 62, and the multi-range PV 120. The latter has a toggle switch for selecting "with/without printer". The PV's were made by Telefunken (ref. 44).

FuG 120 test equipment

Fig. 104: Prüfvoltmeter PV 62 - multi range voltmeter

(source: Fig. 5 and 6 in ref. 203)

FuG 120 test equipment

Fig. 105: Prüfvoltmeter PV 120 - multi range voltmeter

(source: Fig. 3 in ref. 203)


AIRCRAFT (INTENDED TO BE) EQUIPPED WITH FuG 120 "BERNHARDINE"

An estimated 2500 Bernhardine units were installed in various aircraft types (ref. 2A, primarily night-fighter versions), such as the Messerschmitt Me262 (one of my all-time favorite aircraft), but not in the Me262 day-time fighter version (ref. 58A). In August of 1944, it was decided to install the FuG120 in all night-fighter aircaft (ref. 249A). Ref. 288 of mid-November of 1944, states that Messerschmitt had been orderded to install FuG 120a as standard equipment in Me-262 (without detailing in which version of that aircraft), though - for some reason - "the effort will not be able to be fully utilized". Installation in the Me 262 "bad-weather" fighter ("Schlechtwetter-Jäger") was decided in December of 1944; this was configuration "A 1 U 2" of the Me-262 (ref. 59). However, it was cancelled due to lack of availability of the equipment in sufficient numbers (possibly due to Allied bombing of German electronics factories, ref. 60). It was removed from the aircraft equipment list early January of 1945 (see handwritten note in ref. 59). However, a document dated 10 March 1945 (see Fig. 67 in the FuG 120k section) does list the FuG 120k system for the single-seat Me 262 "bad-weather" fighter .

An RAF report on the Me 262 B-2a also describes the FuG 120a as equipment intended for that type (ref. 63). Apparently, a drawing exists that implies installation of a Psch 120 "Peilschreiber" bearing-printer suspended from the canopy between the pilot and radar operator. While purported to be for the Me 262 B-2, this drawing appears to be of the interim night-fighter Me 262 B-1a/U1. Ref. 61, 62. Several captured Me 262 B-1a/U1 showed some equipment at that location.

In May of 1945, a total of 144 Luftwaffe aircraft were surrendered to the RAF at the Schleswig-Land Luftwaffe airbase in the far north of German (renamed Schleswig-Jagel after it became an RAF base). This included eight Messerschmitt 262, five of which were "Bernhardine"-equipped night fighters:

Messerschmitt Me-262

Fig. 106A: Equipment inventory of Me 262 night fighters at Schleswig-Land Luftwaffe airfield, May 1945

(source: ref. 281; Ln 28997/28998 refers to printer Psch & mounting frame RPsch - see ref. 199)

One of the Messerschmitts at Schleswig was Me 262 B-1a/U1 with factory serial number ("Werknummer", W.Nr.") 111980 was known as "Rote 8" ("Red 8") of the Luftwaffe's 10./NJG 11 (10th Staffel of Nachtjagdgeschwader 11) and was equipped with a FuG 120a system (ref. 237). It was ferried to the UK via Gilze-Rijen airbase in The Netherlands on 19 June 1945, where it was involved in a landing incident. It was repaired and continued on to Farnborough, where it was tested. It was shown at various exhibitions before being scrapped during the winter of 1947/48. The Me 262 B-1a/U1 in the photo below had serial number 110306, and was a two-seater trainer converted to a night-fighter. Note the "Hirschgeweih" (stag antlers) antenna of the FuG218 "Neptun" radar on the nose cone. This aircraft, known as "Rote 9" (Red 9), was also surrendered to the RAF at Schleswig airbase, where it received an RAF roundel and marked "USA 2". It was subsequently transferred to the US Air Force, where it was repainted and received tail number FE-610. This was later changed to T2-610, where "T-2" refers to the USAF "Technical Intelligence" section (frmr. "Foreign Data Section") at Wright Field, Dayton/OH/USA, ref. 270. It was scrapped ca. 1950. An RPsch120a mounting frame for a Psch120a printer is visible between the pilot and the navigator/radio-operator canopies:

Messerschmitt Me-262

Fig. 106B: Me 262 W.Nr. 110306 with empty RPsch120 mounting frame and repainted with RAF roundel and Psch120a installed

(source: RAF & USAF, 1945)

The photos below (with a post-war distinctly non-German paint scheme and incorrect symbology!) show "FE-610" with a piece of equipment above the FuG 16 ZY (VHF telephony/telegraphy transceiver and transponder). Based on the size of the equipment, it could indeed be a Psch 120 paper tape printer. A piece of paper tape seems to leave the lower left corner of the equipment. The installation orientation of the equipment also makes sense: the viewing window of the Psch 120 is in its cover, and the printed tape would move right-to-left - as it should, to read the printed symbology.

Messerschmitt Me-262

Fig. 106C: The Me-262 "FE-610" in the USA - with Psch120

(sources: archives of the San Diego Air & Space Museum (SDASM); original photo 1 & 2: no ©, since US Gov't; Psch120: ref. 198A)

Messerschmitt Me-262 Psch120a

Fig. 107A: RgK120a and Spkf1a of the FuG120a - to the right of the rear seat of Me-262 B1a/U1, W.Nr. 110305 "Rote 8"

(soure: adapted from ref. 168; see ref. 236 for the items' F-numbers F390 & F396)

The Psch120 was bolted onto the RPsch120a mounting frame. In the Me-262, this frame's four rubber shock mounts were bolted to another, vertically installed frame. The latter frame was suspended above the FuG 16 ZY receiver by cantilever bars that were fixed to the middle vertical frame of the pilot's canopy:

Messerschmitt Me-262 Psch120a

Fig. 107B: PSch120 mounting in a Deutsche Lufthansa A.G. technical drawing of Me 262 B-1/aU

(soure: adapted from ref. 269; the drawing is dated 3 July 1944 and is actually titled "Nachtjäger B-262 B-2" = night-fighter)

The SG 120, SV 120, and UG 120 of the "Bernhardine" were mounted on a wooden panel against the fuselage behind the rear-seat radio/radar operator. The EBL 3F receiver, FuG 25a IFF-transponder, ZVG 16 radio-nav unit were installed in the same area. The U 120 power supply was located in the equipment bay above the nosewheel, i.e., between the nose cone and the "Waffenraum" gun bay area (together with the U 17 of the FuG 16 ZY VHF transceiver and U 10/S of the FuG 10 transceiver).

Messerschmitt Me-262 Psch120a

Fig. 107C: Location of the SG 120, SV 120, UG 120, U 120, RgK 120, and Spkf1a

(soure: adapted from ref. 269)

There are at least two more installation configurations of FuG 120 equipment in Me-262's:

Messerschmitt Me-262

Fig. 108: Mounting location of the SV120, SG120, and UG120 on a panel against the aft fuselage of an Me-262

(source: p. 484 in ref. 168; original un-annotated photo © EN-Archive, used with permission; see ref. 236 for the items' F-numbers)

 Messerschmitt Me-262

Fig. 109: Bulkhead panel mounting location of the SV120, SG120, UG120, and the EBl 3F receiver

(source: ref. 239)
FuG120k emergency program

Fig. 110: FuG 120k equipment items listed as part of the radio equipment of the single-seat Me-262 "bad weather" fighter

(source: unknown; original unedited image: courtesy M. Gersel)

Other types of aircraft equipped with a FuG 120 were Junkers Ju 88G (ref. 58C, 64, 249A), Junkers Ju 388 (ref. 58B, 65), Arado Ar234 "Blitz" (ref. 66, 238), and Dornier Do-335 A-6 "Pfeil" (though the latter never entered into active service). It may also have been installed in the Dornier P.254 (Do 435).

Mid-1944 the Reichsluftfahrtministerium (RLM, Aviation Ministry of the Reich) launched the Jägernotprogramm (lit. "Fighter emergency-program"). In response to increasing Allied bombing raids, production of most bombers and multi-role aircraft was terminated, in favor of defensive fighter aircraft, in particular jet fighters. Also, development of high-performance experimental aircraft was accelerated, as well as of inexpensive, easy to fly fighters. The FuG 120k was not only planned for the Messerschmitt Me-262 bad weather fighter and night fighter. It was also intended for the Junkers Ju-88 night fighter, Dornier Do-335 A-6 "Pfeil" night fighter, and (ref. 6C, 6G):

FuG120k emergency program

Fig. 111: The FuG 120k was planned to be installed in various Luftwaffe fighter aircraft types - incl. single-seat!

(source: adapted from ref. 6G)

FuG 120k appears to also have been intended for the brilliantly advanced flying-wing Gotha GO-P-60 (Gothaer Waggonfabrik, GWF), probably the night fighter version P-60C. Per ref. 6A (line item 20), Bernhard/Bernhardine flight tests were done in October of 1943, with a Dornier Do-217 M multi-role bomber. Per ref. 76, flight tests were also done in 1943 with the night fighter version Do-27 N (based on model M ).

In November of 1944, Dornier Do 335 night fighters were intended to be equipped with FuG 120:

Dornier Do-335

Fig. 112A: List of intended radio equipment of the Dornier Do-335 night fighter version A-6

(source: ref. 289 (November 1944); to be equipped with FuG 220 "Lichtenstein" radar (later the FuG218 Neptun), and FuG350 Naxos radar detector)

At least three Dornier Do 335 night fighters (serial nr. M10, M15 ,M16) were actually equipped with FuG 120 during February/March 1945 - though unclear with which version. One went to the "E-Stelle" test site Diepensee/Königs Wusterhausen (also a AEG/Telefunken radar test site) near Schönefeld airfield on the south side of Berlin, with its Henschel factory. The other two went to the Luftwaffe airfield at Oranienburg, on the north side of Berlin. The latter had a Heinkel factory, and at that time, was home to Luftwaffe 3. Versuchsverband Ob. d. L. and a Nachtjagderprobungskommando.

Dornier Do-335

Fig. 112B: Actual equippage of three Do 335 Night Fighters with FuG 120

(source: ref. 249E, February 1945)

Dornier Do-335

Fig. 113: A captured Dornier Do-335 "Pfeil" - twin-engine with push-pull propeller arrangement

(prototype V10 of the version A-6, a 2-seater / 2-cockpit night fighter - shown without radar antennas in the leading edge of the wings)


Arado Ar-234B

Fig. 115: Arado Ar-234 "Blitz" - the world's first operational jet-powered bomber


The FuG 120a is listed as radio equipment item "Schreibnavigationsanlage (Bernhardine)" ["Bernhardine" navigation printer system] for the Arado 234 B P5, and located in an equipment area behind the wing:

Dornier Do-335

Fig. 116: FuG 120a is listed on an equipment card of the Arado model B-234 P-5 (dated 31 January 1945)

(source: ref. 238)


Junkers Ju-88

Fig. 117: Junkers Ju-88


Junkers Ju-88

Fig. 118: Junkers Ju-88 G1 night fighter

(source: The Hugo Junkers Homepage; accessed 2 August 2019)

Shown below are excerpts from the two flight log books of Konrad Rösner (ref. 166). For 1944, there are five flights in a Ju-88 (incl. the night fighter variant G1) for which the remarks column mentions flight testing of the "Bernhardine" system:

Junkers Ju-388

Fig. 119A: Excerpts from WW2 flight logs of Luftwaffe radio operator Konrad Rösner

(ref. 166; source: courtesy Walter Waiss (archivist of the "Traditionsgemeinschaft Boelcke e.V."), used with permission)

Junkers Ju-388

Fig. 119B: Translated transcript of Fig. 118A


Rösner was stationed at Twente airbase in The Netherlands, close to the Dutch-German border. The airbase is half way between the "Bernhard" beacon Be-8 at Schoorl (Bergen) in The Netherlands (ca. 155 km to the northwest of Twente AB) and Be-13 at Buke in Germany (ca. 155 km to the southeast). It is also ca. 330 km southwest of the "Bernhard" Be-9 at Bredstedt in Germany (ca. 30 km southwest of Flensburg). Note that in the remarks column, "Flensburg test/guidance" refers to the FuG 227 "Flensburg" radar homing device, and not to a fighter control station at the town with that name (there was no such station there).

Starting in 1943, a number of Ju 88 model A-4 were equipped with the FuG 120 "Bernhardine" at the Strausberg airbase, some 35 km northeast of down-town Berlin (ref. 248). Strausberg became a Luftwaffe flight training center (Flieger-Übungs- und Ausbildungsstelle) in 1935. It included a Blindflugschule (training for flight solely by reference to instruments) and a large Navigationsschule where 6-months courses were taught, with a planetarium (ref. 256).


Junkers Ju-388

Fig. 120: Junkers Ju-388J night fighter


In May of 1943, installation of the FuG 120/120a was also requested for the Junkers model Ju-88-S ("Schnellbomber", the fastest of all Ju-88 bombers), Ju-88-A14 (anti-ship bomber, basically a Ju-88-A4 with more amor, a 20 mm cannon, and a "Kato-Nase" barage balloon cable-cutter in the leading edge of the wings), Messerschmitt Me-410 "Hornisse" (Engl.: "Hornet"; 2-seater multi-role fighter-bomber, discontinued August 1944), and Focke-Wulf FW-190-A4 "Würger" (Engl.: "Shrike"; single-seat fighter):

Junkers Ju-388

Fig. 121: request for installing the "Bernhardine" a.s.a.p in various Luftwaffe aircraft types

(source: ref. 249B)

Note that to this date, no documentary evidence has emerged, confirming that this installation request was actually realized. In particular for the FW-190, which is a single-seat aircraft (no navigator / radio operator).

FW-190/Me410

Fig. 122: Me-410 A-2/U1 night fighter (left) and an Fw-190 A-4 somewhere in France, 1943

(sources: unknown)

Towards the very end of WW2, the Messerschmitt company conceived a number of highly advanced fighter and bomber aircraft that never went into production. An example of this, is the Me P 1107/I ultra high speed (transonic) bomber, which was planned to have the FuG 120 "Bernhardine" on board (ref. 240).

Junkers Me-P1107

Fig. 123: Preliminary design of the Messerschmitt P 1107/I long-range transonic jet bomber

(source: USAF Air Materiel Command (AMC), Intelligence Dept. (T-2), Air Documents Div., 1947)


THE FuBl RADIO-NAVIGATION RECEIVER SYSTEM

Standard radio-navigation systems for instrument approaches (so-called "blind landing" = solely by reference to instruments) were the "Funk-Blind-Landeanlage" FuBl 1 and the FuBl 2 (initially written with roman numerals I and II). Ref. 11, 31, 32, 39A, 67, 68, 69, 217. The airborne part of the FuBl 1 system is the EB.3, a militarized version of the Lorenz EB.2 (ref. 31). This system was invented in the early 1930s by Ernst Kramar, Walter Hahnemann, et al (Lorenz Co., e.g., US patent 2,072,267 and 2,217,404) and was successfully commercialized for civil aviation around 1937. The principles of the system are used worldwide to this day (ILS - Instrument Landing System, which even uses the original tone frequencies). The ground station (fixed or mobile) had a 500 W transmitter system, the Ansteuerunsgsender AS 2 (ref. 39D).

The FuBl 2 was basically a FuBl 1 with an extended frequency range and increased sensitivity, to make it work with the Knickebein, Bernhard, and Hermine systems. The airborne system included both a Lorenz EBl 2 and an EBl 3 receiver.

  • The EBl 1 "UKW-Blind-Einflugzeichen-Anlage" is an AM superregenerative ("superregen") landing beacon receiver that covered the 30.0-31.5 MHz frequency range, plus 33.33 MHz (the civil blind-landing beacon frequency). It has 2 selectable frequencies, that could only be pre-set on ground by a technician. Presetting the civil fequency required additional adjustent of the "regen" feedback-loop gain.
  • At 200 m altitude (≈660 ft), its sensitivity was sufficient to ensure reception of the standard 500 W landing beacons out to about 30 km (ref. 31, 39A).
  • Note: superegen receivers have an inherent bandwidth of appr. 1% of the operating frequency, i.e., ≈300 kHz at 30 MHz - which is not a good thing when selectivity is desired (e.g., when dealing with interference/jamming)!
  • The EBl 2 "Markierungsfunkfeuerempfänger" is marker-beacon receiver with a fixed frequency of 38.0 MHz. It indicates passing of fan-marker beacons that are placed at fixed distances from the runway, on the extended runway centerline. The EBl 2 was made by Lorenz, but also manufactured under license by Philips, in its factory in Vienna/Austria (ref. 31).
  • The EBl 3 is an AM superheterodyne ("superhet", "Überlagerungsempfänger") receiver for VHF landing-guidance beam systems ("UKW-Blindflug-Leitstrahl-Anlage". Ref. 72. This receiver was developed by Lorenz AG out of the FuG 16 (ref. 29, 70,79). It was a replacement for the EBl 1. It provides a lateral guidance signal (left/right deviation) to an AFN indicator (Anzeigegerät für Funk-Navigation" model AFN-1, or the later model AFN-2 and AFN-2A), and to a lateral-axis auto-pilot. In combination with navigation beacons such as the Knickebein system, the EBl 1 had insufficient sensitivity for long range navigation (i.e., to targets in England). The EBl 3 was produced by several manufacturers, including AEG Sachsenwerk in Dresden-Niedersedlitz. It comprised seven tubes of type RV 12 P 2000 (schematic: ref. 71), and had an IF of 6 MHz. This receiver has a large bandwidth: ca. 15 kHz. Note that these days, long-, medium- and short-wave AM radio stations only have 5, 9, or 10 kHz channel spacing, and a baseband bandwidth half that size! Initially, the unit had a light-metal ("Elektron") die-cast construction, built by Mahle. Towards the end of the war, the chassis housing and front face were made of simple sheet metal.
  • On the western front, the transition from FuBl 1 with the EBl 1 to FuBl 2 with the EBl 3 took place around September of 1941. Within a couple of weeks (12 October 1941), the British recovered an EBl 3 from a Dornier Do-217 E-1 bomber/reconnaissance aircraft that made an emergency landing on Jurys Gap beach in Sussex, between Rye and Dungeness, after a long erratic flight marked by British interference with German radio-navigation systems and probably poor dead reckoning due to insufficiently accounting for the strong winds. Ref. 2B (p. 155).

Note that the EBl 3 receiver does not contain audio amplifier stages, see Figure 124. The AM envelope-detector of the EBl 3 is an RV 12 P 2000 tube that is used as rectifier diode. Its output is passed straight to the EBl 2 receiver (and, when used with the FuG 120, via the UG 120 switch box to the SV 120 printer-amplifier). The input of the EBl 2 has the DC-blocking capacitors, an isolation transformer, and amplifier/filter stages for a headset output, to generate the normal AGC-signal for the EBl 3, and signals for the AFN1 or (smaller) AFN2 indicator.

The EBl 3 used an 80 cm (≈ 31.5 inch) long vertical rod antenna - either fixed, or retractable (Ausfahrbarer Antennenmast AM 5). The EBl 2 had a 2x 95 cm (≈ 2x 37.5 inch) horizontal dipole antenna, aligned with the longitudinal axis of the aircraft. Ref. 72 (pp. 43, 49, 50).


EBL2 EBL3

Fig. 124: Block diagram of the EBL3 and EBL2 receiver

(source: adapted from ref. 72)

There are several EBl 3 models (ref. 72):

  • EBL 3H, where "H" stands for "Handbedienung" = manual tuning (hand-crank). It covered 30.0 - 33.1 MHz with 32 channels (100 kHz channel spacing). These were allocated to the "Bernhard/Bernhardine" system. Channel-33 and channel-34 were set to 33.02 and 33.33 MHz respectively. The latter two channels were for "blind landing" purposes. Model 3H1 had a manual tuning module that could be replaced with an optional remote-controlled tuning unit.
  • EBL 3F, where "F" stands for "Fernbedienung" = remote-control tuning. It had no Channel-34, and Channel-33 was set to 33.33 MHz. The corresponding remote control head was Fern-Bedien-Gerät FBG 2 or FBG 6.
  • EBL 3G is basically an EBL 3F with +/-15 kHz fine-tuning.

Note that, unlike the EBl 1 receiver, the EBl 3 could not switch between two frequencies with a simple toggle switch! Such switching back & forth was actually needed when (near)simultaneously tracking two radio navigation beacons such as "Berhard" or "Knickebein".

These receivers where normally used in conjunction with landing guidance systems (instrument landing system for "blind" flying). Other than during approach and landing, these receivers could be used or other purposes. The two tone signals transmitted by the "Bernhard" beacon stations were close enough in frequency that they could be received by a single wideband receiver. The two tones were separated by the SG 120 ("Siebgerät") audio filter unit of the "Bernhardine" system, and amplified and rectified in the SV 120 ("Schreibverstärker") unit before being passed to the printer unit.

EBL 1 receiver

Fig. 125: Receiver model "EBl 1"


EBL 2 receiver

Fig. 126: Receiver model "EBl 2"


The only aircraft actually equipped with the EBl 3 were (ref. 74, p. 106 in ref. 2A): the bomber version of the Ar-234, the nigh-fighter version of the Ju-88 and Do-335 (appendix II in ref. 6G), Do-217 (ref. 75, 76), and the bad-weather fighter ("Schlechtwetterjäger") version of the Me-109, the Me-262 (ref. 58A, appendix II in ref. 6D), Ju-388 (ref. 58B), FW-190, and Ta-152, and the reconnaissance version of the Me-109, Me-262, Ar-234 (planned only, per ref. 74), and Ta-152. The latter is an early 1945 high-altitude interceptor-fighter derivative of the ubiquitous Focke-Wulf FW-190. The designator "Ta" refers to the renowned FW chief-designer, Kurt Tank. The EBl 3 measures 23x14.3x15.6 cm (WxHxD, ≈9x5.6x6 inch).

EBL 3 receiver

Fig. 127: Receiver model "EBl 3H1"


EBl 3H turning

Fig. 128: Receiver model "EBl 3H"

(courtesy Erich Werner, used with permission)

 EBl 3H receiver

Fig. 129: Receiver model "EBl 3H"

(source: Figure 5.2 in ref. 78)
EBL 3 receiver

Fig. 130: "Landeempfänger" EBl 3 (lower equipment row, right of center) in a "Bordfunkanlage" FuG 10 P

(source: Figure 4.4 in ref. 78)

FBG2 remote control

Fig. 131: FBG2 "Fernbediengerät" remote control unit  for the EBl 3F

(source unedited images: eBay article nr. 323686266762, December 2021)

After the war, the small company Curt Höhne Radiomechanik (radio sales & repairs) in Dresden-Radebeul, somehow "acquired" the EBl 3 inventory of the Sachsenwerk factory from the Russian authorities, and converted parts of them to car radios such as the AS503-OS (ref. 79). Conversions were also published for the 2m (145 MHz) amateur radio band (e.g., ref. 80 from 1952).

AS503-OS receiver

Fig. 132: Receiver model "AS503-OS"

(source: ref. 79)


PATENTS

Below is a listing of patents related to Bernhard/Bernhardine.

Patent number Patent office Year Inventor(s) Patent owner(s) Title (original) Title (translated)
767354 RP 1936 - Telefunken G. für drahtlose Telegraphie m.b.H. Verfahren zur Richtungsbestimmung Method for direction-finding [this is the primary "Bernhard" patent]
730625 RP 1937 R. Hell Dr.-Ing. Rudolf Hell Verfahren zur Registrierung des Verlaufes veränderlicher Stromkurven Method for printing the trace of varying signals [pulse-width modulator, Hell printer for signal-level track of Bernhardine]
767513 RP 1939 A. Lohmann Telefunken GmbH Empfangsseitige Schreibvorrichtung zur Durchführung eines Verfahrens zur Richtungsbestimmung [Wachsschreiber] Receiver-side printer for the implementation of a method for direction-finding [wax printer, infinite loop, erasable tape]
767523 RP 1938 A. Lohmann
A. Bittighofer		 Telefunken GmbH Empfangseinrichtung zur Durchführung des Verfahrens zur Richtungsbestimmung Receiver-side device for the implementation of the method for direction-finding
767526 RP 1938 A. Lohmann Telefunken GmbH Verfahren zur Richtungsbestimmung Method for direction finding [proposes 3rd beam, for AGC]
767527 RP 1938 A. Lohmann Telefunken GmbH Einrichtung zur periodischen Ein- bzw. Ausschaltung einer Registriervorrichtung Device for switching on and off of a printer
767536 RP 1940 A. Lohmann Telefunken GmbH Empfangsseitige Schreibvorrichtung zur Durchführung eines Verfahrens zur Richtungsbestimmung Receiver-side printer for the implementation of a method for direction-finding [print medium is erasable Printator foil disk instead of Printator tape]
767919 RP 1940 H. Muth Telefunken GmbH Verfahren zur Richtungsbestimmung unter Verwendung eines rotierenden Funkfeuers Method for direction-finding with a rotating beacon [using only twin-lobe beam]

Here are some ancillary patents:

Patent number Patent office Year Inventor(s) Patent owner(s) Title (original) Title (translated)
562307 RP 1929 J. Robinson J. Robinson Funkpeilverfahren Method for direction finding [transmission of coursepointer, or compass rose info via Nipkow-video]
620828 RP 1933 - Marconi's Wireless Telegraph Co. Ltd. Funkpeilverfahren Method for direction finding [transmission of compass rose info via Nipkow-video]
754395 RP 1941 Gerhard B.Hagen Telefunken GmbH Einrichtung zur Registrierung von langsam veränderlichen Spannungskurven.
Note remarkable "similarities" with the 1937 Hell patent nr. 730625		 Arrangement for printing slowly changing voltage curves

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

REFERENCES


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External links last checked: August 2019, unless stated otherwise.


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