red-blue line


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 beacon systems during "blind" approach and landing, and in combination with other beacon systems for guiding bombers and fighter aircraft to their target. The printer system provides 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)

For many years, I have searched for original German documents on the FuG 120 system. Finally, in December of 2013, I located a US microfilm copy in the National Library of... Japan! Several weeks later, a photo copy of the 40+ page document arrived in the mail, see ref. 15. It confirmed most of my assumptions and conjectures, and clarified some open questions.

The FuG 120 "Bernhardine" system comprises the following equipment items (ref. 4, 5, 15, 42, 43, 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. 3 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: p. 99 in ref. 3)

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

The equipment items UG120, SV120, U120, as well as the installation items 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's code is "bou".

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):

The airborne "Bernhardine" system with its Hellschreiber printer, works together with a "Bernhard" beacon ground-station. The "Bernhard" beacon has a rotating antenna system that makes one revolution every 30 sec:

Bernhard beam concept Rotating beacon cartoon

Fig. 3: Concept of the Bernhard/Bernhardine radio-navigation system

The "Bernhardine" Hellschreiber-printer in the aircraft prints two parallel tracks on a paper tape, see Figure 3 above:


A standard Hellschreiber printer consists of an inked spindle that is placed across, and slightly above, a moving paper tape. Below the paper tape is an electromagnet with a hammer. See Figure 4A. When the magnet is energized, the hammer pushes the paper tape against the continuously turning spindle. The magnet-solenoid is energized as soon as, and as long as, a tone signal is received. This causes a dot or line segment to be printed across the paper tape. The length of the printed line depends on the amount of time that the electromagnet is energized.

Standard 1-channel Hellschreiber printer

Fig. 4A: Principle of a standard Hellschreiber printer

Unlike very complex (and large) "telex" teleprinters, this very robust method requires only detection of "signal present / not present". It requires no machine-interpretation of a sequence of "bits", to determine what to print. Also, the compact Hell-printer mechanism has very few moving parts, and is not limited to printing a predetermined character-set. The Hellschreiber can be thought of as a remote dot-matrix printer for any form of low-resolution graphical information (a line of text or other symbols). See the Hellschreiber "How it works" page.

The "Bernhardine" system is actually a dual Hellschreiber-printer. It has two independent printer mechanisms. The lower trace prints the compass rose (azimuth) or command text-messages. This is transmitted in Hell-format by the single-beam antenna array of the rotating "Bernhard" ground station. The upper trace prints the strength of the continuous tone transmitted by the twin-beam antenna array of the ground-station. The two printer-spindles are mounted on the same motorized shaft that turns at 720 rpm (12 rps, ref. 15).

2-channel Bernhardine Hellschreiber printer

Fig. 4B: Principle of the dual-trace "Bernhardine" Hellschreiber printer

The "Bernhard" beacon rotates twice per minute. So it has a rotational speed of 360° / 30 = 12° per second, or 1° in 1/12 sec. The azimuth data is printed with a resolution of three pixel-columns per degree (see Figure 5). That is: 3 x 12 = 36 columns per second. The bar-graph is printed with six pixel-columns per degree (ref. 15). That is: 6 x 12 = 72 columns per second.

azimuth print-out

Fig. 5: Azimuth print-out

(source: ref. 15)

Of course it is possible to print 36 pixel columns per second, with a spindle that has a single thread that is wrapped once around the hub of the spindle. Such a spindle would have to turn at 36 rps = 2160 rpm. Likewise, such a spindle can print 72 bar-graph columns per second, by spinning at 72 rps = 4320 rpm. This is not practical for two reasons. First, 4320 rpm is extremely fast. And to get a stable speed, the motor (with down-gearing) would have to run even faster. Secondly, in the "Bernhardine" printer, both spindles are mounted on the same shaft, so they turn at the same speed. The solution is simple: use multi-start spindles. By using a spindle with N starts, the required shaft speed is reduced by a factor N. Two spindles on the same shaft can have a different number of starts.

In the "Bernhardine", the bar-graph printer has a 6-start spindle (N = 6): it has six thread-segments. Each covers 360° / 6 = 60° of the circumference of the spindle hub. The thread segments do not overlap. See Figure 6. The azimuth printer has a 3-start spindle: N = 3. Its three thread-segments each cover 360° / 3 = 120° of the spindle hub. This means that these two spindles can turn at the same speed: 2160 / 3 = 4320 / 6 = 720 rpm. This speed is easily obtained with down-gearing a standard 3000 - 4000 rpm motor. E.g., the "Presse Hell" printer has a 3000 rpm motor, the "Feld-Hell" machine has a 3600 rpm motor. The 3-start spindle prints three columns per rev, the 6-start spindle prints twice as many.

6- and 3-start spindles
print of 6- and 3-start spindle

Fig. 6A: The 6-start spindle (bar-graph) and 3-start spindle (azimuth) of the "Bernhardine" Hellschreiber printers

azimuth print-out

Fig. 6B: The 6-start spindle of an HS120 "Bernhardine" Hellschreiber printer

The columns of the bar-graph have to be printed bottom-to-top. In principle, the azimuth data could be printed either bottom-to-top or top-to-bottom. However, as explained below, it has to be printed top-to-bottom, because the printer is synchronized to the degree tick-marks at the top of the printout (every third column = 1 rev of the spindle). This means that the two spindles have to print columns in opposite direction, even though they turn in the same direction! This is solved by one spindle having a right-hand thread, and the other spindle a left-hand thread. See Figure 6A above.

The color of the printer ink is reported as being red (§29 in ref. 6). However, this would have resulted in poor contrast on the white paper tape, compared to using dark ink, such as the Hell standard dark violet. Also, red was probably not compatible with night-time lighting conditions in a cockpit (often yellowish, or even red, as this color light does not affect night vision). Per ref. 15, ink of type "HB-50" was to be used. This is Haberolin-Basolomin ink. Haberolin was a deep-black cloth dye (marking-ink), made by Wilhelm Haber. "Wilhelm Haber Stempfelfarben" company was founded in 1873. The company still exists today (located in Lommatzsch, 160 km (100 mi) south of Berlin), under the name "Wilhelm Haber Stempelfarben Steffen Haeckel e.K." Dark violet "HB 45" was the standard ink for other Hellschreibers. I do not know the color of HB50.

The dual Hellschreiber-printer of the "Bernhardine" system comprises the following elements, see Figure 7:

principle diagram HS120

Fig. 7: principle diagram of the HS 120 dual Hellschreiber printer


As described above, the "Bernhard" ground station transmits a constant tone via its twin-lobe antenna array. The signal strength of the received signal is printed as a bar-graph in the upper trace of the paper tape. See Figures 3, 8, and 9. The bar-graph has six bars per degree of azimuth (ref. 15). Special circuitry is used, to ensure that the bars start exactly at the bottom of each printed pixel column, and that the height ( = duration of the energization of the printer magnet) corresponds to the signal strength (0 - 100%).

Berhard signal strength plot

Fig. 8: signal strength bars, as printed with the Bernhardine-Hellschreiber

(source: ref. 3)

Berhard signal strength plot

Fig. 9: Signal-level bar-graph based on received signal strength from the main lobes of the antenna pattern

(source: adapted from ref. 46)


The single-lobe antenna of the "Bernhard" ground-station continuously transmits the momentary direction of the antenna (i.e., antenna azimuth = bearing from the station) in Hellschreiber-format. This is printed by the second Hellschreiber-printer of the "Bernhardine", directly below the bar graph of the signal-strength. The result is a segment of a compass rose that is about 30-40 degree wide. The V-shaped dip in the bar graph points at the actual bearing-from-the-beacon that the aircraft is on (255.0° in Figure 10B).

Patin remote compass

Fig. 10A: Remote compass, as used e.g. in Fw190

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

":Bernhardine" compass card

Fig. 10B: the compass rose segment is printed below the bar graph


The motor in the "Bernhardine" Hell-printer is not synchronized to the rotation of the optical disk of the "Bernhard" ground station, that sends the azimuth data in the form of a pixel stream in Hellschreiber-format. In a standard Hellschreiber system, speed differences between sender and printer result in slanting of the printed track. E.g., downward slanting if the printer is slower than the transmitter:

Downward slant

Fig. 11A: Downward slant for receiver spindle that is slower than the transmitter

(source: Figure 9 in ref. 47: 5% asynchrony)

Even if sender and printer are running at exactly the same speed, phase differences result in the printed track being shifted up or down. The slant, or shift, causes part of the track to end up beyond the vertical limit (upper or lower) of the track. See Figure 11B.

Split text line

Fig. 11B: The printed text is split, due to phase difference between sending and receiving motor

(motor speeds are identical - printed text line is not slanted)

In standard Hellschreiber printers of the 1930s and 1940s, the classical solution to this problem is to use a printer spindle with a thread that is wound twice around the hub of the spindle. Such a spindle prints two identical text lines in parallel, one above the other. Hence, at least one text line is always fully legible. See Figure 11C. This is combined with manual adjustment of the printer's motor speed.

Double text line

Fig. 11C Double-line text remains completely legible despite slant and shift, caused by speed & phase difference

Double etxt line

This solution is not an option for the "Bernhardine" printer. Yes, doubling the printout of the azimuth data would make that data legible at all time. However, due to the slant or vertical shift of the printed azimuth data, the bar-graph pointer may no longer line up with the degree tick-marks. See Figure 12. Secondly, manual speed adjustment would not have been practical for the "Bernhardine", as the rotating beacon is only received about 3-5 sec per 30 sec rotation, and (night) fighter pilots cannot afford to spend significant time on such a task. The azimuth printer must somehow be synchronized to the pixel stream, such that the degree tick-marks are aligned with the top of the printed track. I.e., they must all be printed just below, and parallel to the bar-graph.

No double-helix for Bernhardine

Fig. 12 The standard Hellschreiber "double helix" is not an option for the "Bernhardine"

Unlike "telex" teleprinters and post-war start-stop Hellschreibers, the Hellschreiber "font" of the azimuth data contains no explicit start "bits". However, the pixel stream does include a tick-mark at the top of every third pixel column. Each tick-mark is at least three pixels long (the 5° tick-marks are 4½ pixels long, and the 10° tick-marks 10 pixels). These tick-marks are used for synchronization.

As in all teleprinters with character synchronization, the "Bernhardine" motor runs a little faster than the nominal speed: 1.5% (ref. 15), equivalent to about ½ pixel per three columns. This way, it finishes printing each character (here: 3 pixel columns) slightly early. The printer then waits a brief moment, until the next sync pulse (here: tick-mark) is detected, and then starts to print the next character at exactly the right moment. The same method was used for many decades, to synchronize clocks at train stations to an accurate central master clock: each minute, all station clocks run several seconds fast. At the top of the minute, the hands of the clock are held in place, until the central clock sends a release signal to all slave clocks, to start ticking away the next minute.

As stated above, the spindle of the bar-graph printer and the spindle of the azimuth printer are both mounted on the same spinning shaft. But only the azimuth spindle requires synchronization. This implies that this spindle is not permanently fixed to the spindle shaft! It is actually mounted onto that shaft with a small standard slip-clutch. This allows the spindle to be "grabbed" and stopped, while the spindle shaft keeps turning at a constant speed. As soon as the spindle is released, it starts to spin again with the shaft. So a "grab, hold, and release" mechanism is needed. This is just a simple so-called "indexing" mechanism. See Figure 13 below. There is a "catch" notch or pin on the spindle hub (not on the spindle shaft!). A small hook at the end of a spring-loaded lever holds the notch, and prevents the spindle from turning with the spindle shaft. When the motor is running, the clutch slips continuously. A brief energization of the synchronization electro-magnet causes the notch to be released. The spindle now turns with the shaft (no slip). After one revolution of the spindle, the notch on the spindle is caught again by the lever. The spindle is briefly stopped until the next release-pulse (= degree tick-mark), etc. The synchronization-magnet is placed in series with the magnet-solenoid of the azimuth printer. That is, they are energized and de-energized simultaneously.

No double-helix for Bernhardine

Fig. 13: Synchronization mechanism of the azimuth Hell-printer

(source: adapted from Figure 9d of ref. 15)

Let's go through a complete "catch-and-release"" sequence, see Figure 14. Assume that the spindle is held by the sync-lever. The first pixel of a degree tick-mark is received. This causes the notch of the spindle to be released. The spindle turns freely for 1 revolution = three pixel columns. Note that, depending on the pixel pattern in these three columns, the sync-magnet may arm and disarm the lever several times during this revolution! However, this has no effect, since the notch on the spindle is only near the hook of the lever just before the spindle completes its revolution. The lever catches the notch during the white pixel that always precedes the next degree tick-mark ( = bottom of the preceding pixel column).

Bernhardine sync mechanism

Fig. 14: Timing diagram of the synchronization process

This concept of synchronization is based on characteristics of the Hellschreiber pixel-stream instead of explicit start-bits. This was was re-used in the Hell Blattschreiber of the 1950s. In the standard Hell-system, the character font has two white pixels, both above and below each printed pixel column. I.e., there is symmetry in each pixel column, and there should be no black pixels at the top and bottom of the printed pixel columns. During printing, the actual vertical symmetry can be measured, and used to speed up or slow down the motor. This control-loop eliminates the phase difference and, hence, also the speed difference.

Hellschreibers developed after this Blattschreiber, all used start-stop synchronization with an explicit starts-pulse embedded into the first (normally blank) column of the character font: Hell-39/44, Hell 72/73, and Hell-80. The Hell-40 was a replacement for the "Presse Hell", so it did not use synchronization.

According to the "Bernhardine" manual (ref. 15), it required 2 to 4 beam-passages for the synchronization system to be tracking the tick-marks properly: "After selecting the beacon, wait until the Hellschreiber spools up and prints properly (1-2 minutes). The first two prints are not dependable". This could explain the wavy printout in Figure 15 (pink lines). The printed bar-graph is perfectly straight, as it is always fully synchronized to the spindle. Note that waviness could also have been caused by variations in the speed of the beacon.

Wavy azimuth track

Fig. 15: Print-outs with wavy azimuth track

(source: ref. 3)

As stated above, the AGC and synchronization circuitry of the SV120 printer amplifier provides automatic adjustment of the two printer tracks. The only manual adjustment available, is the gain control of the pre-amplifier of the SV 120. The knob (labeled "Empfindlichkeit" = sensitivity) is on the front of the HS 120 printer. Figure 16 shows how it had to be used to obtain correct printing quality.

Wavy azimuth track

Fig. 16: Incorrect and correct printing - adjustment with manual gain control on the HS120 printer

(source: figure 25 in ref. 15, ref. 48)

As stated above, the motor of the Hellschreiber printer ran 1.5% faster than the nominal speed of the beacon's azimuth data transmission. Note that this is more than the typical 0.5% speed difference between the transmitter and printer motors of "telex" teleprinters of the era. It basically implies that the "Bernhard" beacon should not turn faster than the nominal 12°/sec rotational speed. The beacon should also not turn more than 1.5% slower than the nominal speed. If so, a black pixel at the bottom of the column preceding the next tick-mark (e.g., the last pixel of the beacon identifier letter), could inadvertently be interpreted as the next tick-mark and release the spindle. This may cause slant to continue or even worsen, until the printer temporarily syncs again to a real tick-mark. Note that at least two out of every five degree tick-marks are preceded by least one complete white pixel column. This is enough for a "clean" sync.

A few "Bernhard" stations had the capability to transmit 10-character "Reportage" messages, instead of the the azimuth data. Clearly, these messages should also be printed as a single horizontal line of text. I.e., without slant or vertical shift. The normal Hellschreiber font does not include a tick-mark at the top of every third pixel column. The character generator that was used for sending the "reportage" text strings must, however, have included such extra pixels. This would not have been difficult to implement, and would not have been very distracting in the print-outs.


The HS 120 unit measures 35.7x15x14 cm without the housing (WxHxD, ≈14x6x5½"). This is relatively large, but not the unrealistic 60x30x20 cm (≈23½x12x8") that is usually quoted for this model (ref. 6, 49). The official manual (ref. 15) states the following dimensions: 36.2x21x17.4 cm (WxHxD, ≈14.3x8.3x7"). However, the latter height includes a large connector that protrudes from the bottom of the unit, and mounting lugs at the top and bottom on the back of the housing (cf. Figure 13 in ref. 15). The unit weighs 7 kg (15½ lbs).

Based on its size, it could only be used used in larger aircraft (two or more seats, e.g., near the radio/radar operator), and in the Bernhard ground monitoring station. The window in front of the paper tape measures about 24x4 cm.

This Hellschreiber normally has a single, wide paper tape. It is powered by a 24 Volt DC motor, running at 3000 rpm. The paper tapes are re-wound onto a second set of reels inside the printer, so there is no paper tape mess in the cockpit. The upper part of the front panel is hinged, to facilitate inserting the paper tape across the front of the printer. The tape moves from right to left in the window.

HS120 front view

Fig. 17: Front view of an HS120 Hellschreiber

(original unedited photo: courtesy Leonard Hunter, used with permission)

The front panel has controls for printer-amplifier gain ("Empfindlichkeit" = sensitivity) and lighting brightness ("hell/dunkel" = bright/dim). The "D" toggle switch is a push button for resetting the automatic gain control in the SV120 printer-amplifier, for the EBl 3 radio receiver. At the left and right bottom corner, there is a large mounting bolt that goes all the way through the unit, into the equipment rack of the aircraft. The red ring around the hole for the bolts indicates that the bolts may be removed for field maintenance by standard technicians. The bolts are spring-loaded, to expedite removal and installation of the unit.

Label on HS120

Fig. 18: Label on the front panel of the HS120 Hellschreiber

The label in the photo above provides the following information:

The "Gerät-Nummer" 124-1425A-1 refers to a "Spezial Hellschreiber". All items of the "Bernhardine" system have a Gerät-Nummer starting with "124". This two-part Luftwaffe numbering system is similar to that used by the Heer (Army), ref. 50: a category number ("Stoffgliederungsgruppe", possibly with a suffix for an "Untergruppe" sub-category), followed by an item number.

"Anforderzeichen" Ln28980 (p. 28 in ref. 44). The "Ln" number refers to a Kennblatt (specification sheet) of the Luftwaffe Luftnachrichten (Signal Corps), ref. 52. This particular Ln-number belonged to the technical domain of LU-F-NAVKOMMÜB: Aeronautical Radio Navigation, Communication, Surveillance. These days, the combination Comm-Nav-Surveillance ("CNS") is still used in aviation! The HS120 was built by the Hell company, starting in 1942 (p. 188 in ref. 44). The Hell company had the military 3-letter manufacturer code ("Fertigungskennzeichen") "cmw".

"Werk-Nr." is a serial number. Obviously, no 70346 units were ever built. The "7" may refer to the production series or batch, model variant, modification standard, or factory. The "346" would then be the actual production serial number of this particular unit.

Next to the label is white Waffenamt acceptance stamp: "BAL 378" inside an octagon. The same stamp appears inside the unit, on the chassis near the motor. According to Luftwaffe service regulations, "BAL" stands for Bauaufsichten des Reichsluftfahrtministerium (the Administration of the RLM for the Supervision of Construction, ref. 52, 53), in short "Bauaufsicht Luft". It was subordinate to the Technisches Amt of the RLM. The number "378" refers to the accredited inspector. There is a second "BAL 378" stamp, inside the unit, near the motor. See Figure 19. This BAL number has also appeared on products of "Fernmeldetechnisches Entwicklungslaboratorium Dr. Ing. H. Kimmel" ("Development lab for telecom equipment", though they also made measurement equipment) in Munich. Their 3-letter military manufacturer's code was "bes". Kimmel also made the "NF Phasenuhr" (audio frequency phase-indicator, with 360º scale) that was part of the on-board equipment of the 1943 Lorenz VHF rotating-phase navigation system "Erich" (very similar to the VOR system developed in parallel in the USA). Like "Bernhard/Bernhardine", the "Erich" system also used the EBl 3 receivers.

BAL378 on HS120

Fig. 19: "BAL 378" acceptance stamp on top of the chassis, next to the motor

HS120 top view

Fig. 20: Top-view of an HS120 Hellschreiber

(left to right: stacked electromagnets, reel for blank paper tape, motor, reel for printed paper; original unedited photo: courtesy L. Hunter, used with permission)


Fig. 21: Top-view diagram of an HS120 Hellschreiber

(source: Figure 13 in ref. 15)

6-start HS120 spindle

Fig. 22: The 6-start spindle (yellow arrow) and sync-magnet (magenta box) of an HS120 printer

(original unedited photo: courtesy Leonard Hunter, used with permission)

To avoid a paper tape mess in the cockpit, the paper tape is unwound from one spool, and wound onto a second spool (like in a reel-to-reel tape recorder). To minimize paper consumption (and the hassle of having to replace rolls of paper tape in flight), the paper transport motor was only enabled when the strength of the received signals exceeded a certain minimum value. I.e., a "squelch" function. This way, the paper moved during less than 10 sec per minute (3-5 sec per antenna revolution, equivalent to 36-60 deg change in antenna azimuth). After passages of the beacon's beam, the paper tape would stop moving, and the operator could interpret the print-out.

HS120 rear view

Fig. 23: Rear-view of an HS120 Hellschreiber

(modified for use with two standard-width paper tapes, instead of a single wide tape)

The motor of the HS120 was made by the "Stark-Motor" company of Berlin. Before the war, Stark made electric motors and alternators for the automotive industry. Their motors were also used in Luftwaffe aircraft, including servo-motors for bombsights.

Label on Stark-Motor

Fig. 24: Label on the motor - 24VDC, 3000 rpm

(Motor type "SMKO", as specified in ref. 15)

The company was owned by Hans Stark:

Hans Stark phone book entry 1943

Fig. 25A: Listing in the electric motor section of the 1943 Berlin phonebook (Teil II, p. 165)

(with advert for "small rpm-controlled electric machines"


Fig. 25B: Listing in the electric motor section of the 1951 Berlin phonebook

(still at the same address)

Right-hand sode of an HS120

Fig. 26: Right-hand side of an HS120 Hellschreiber

(two stacked felt ink rollers left of center; note synchronization mechanism for the upper printer channel was removed)

The bottom of the HS 120 shows how the single motor drives the shaft of the printer spindles and the paper tape transport (Figure 27). All capacitors and inductors are also located here (ref. Figure 7). The spool for the printed paper tape is driven via a spring belt that can slip (top right in Figure 27); this tensioning mechanism is needed, as the speed of the spool depends on how much paper tape is wound onto it.

HS120 bottom view

Fig. 27: Bottom of the HS120 Hellschreiber

(original unedited photo: courtesy Leonard Hunter, used with permission)


Fig. 28: The stacked electromagnets, with their hammer blade against the paper tapes

The following marking is engraved on the back side of the plastic backlighting panel of the HS120: "A. BAJANZ, Berlin -- DRGM;DRP.angem." The Bajanz company manufactured acrylic glass parts (common trade names are plexiglas and perspex), including canopies for military planes (e.g., Heinkel). The abbreviations DRGM, DRP, and angem. respectively stand for "Deutsches Reichsgebrauchsmuster" (model - or patent, in the proper sense of the latter word). This implies "registration without patent protection", "Deutsches Reichspatentamt" (the patent office), and angemeldet: "applied for" ("pending").

BAJANZ marking inside HS120

Fig. 29: Marking of the manufacturer of the plexiglas front panel

Here is a 25 sec video clip of this printer in action:

An HS120 printer in action

Note: this machine was modified to use two standard Hell paper tapes, instead of one wide tape. It has regular 2-turn spindles, hence, cannot print single-line symbology.


The Psch 120 "Peilschreiber" (bearing printer) was built by Siemens & Halske A.-G in Berlin (p. 188 in ref. 44). They had the military manufacturer code "eas". This code was used for all Siemens plants, such as the Wernerwerk telecom design and manufacturing plant in Berlin-Siemensstadt, were other Hellschreibers were built. Siemens also made the RDFS 120 "Rahmen für Drehfunkschreiber" (the mounting frame for Psch 120), and a "Papierbehalter für Peilschreiber" for storing (used) paper tape of the Psch 120.

There are suggestions in 1945 Allied post-war reports that the development and prototyping labs of C. Lorenz A.G. in Falkenstein/Thuringia (some 100 km southeast of Nürnberg) were involved with this printer (ref. 54). A number of development labs (some 700 employees, no production) were moved there in August of 1943, from Lorenz in Berlin (ref. 55).

Psch 120

Fig. 30: Peilschreiber (bearing printer) "Psch 120" of the FuG 120a - a compact paper tape printer

(source: page 101 in ref. 3)

Psch 120

Fig. 31: Photo of another "Psch120" unit

(source: ref. 7B)


Peilschreiber 120a (Psch 120a) is the printer of "Berhardine" FuG 120b system. It is a "paperless" printer. The idea was to avoid time-consuming replacement of a full roll of tape during flight, and avoid running out of tape altogether.

The 1939 patent 767513 proposes a bearing printer that uses an endless 3-layer printing tape. This tape is a triple-layer sandwich of wax-covered dark paper, thin silk tape, and thin protective celluloid tape. This technology actually dates back to ca. 1923, when a two-layer version was patented (but not invented) by R.A. Watkins of Illinois/USA (later Watkins-Strathmore Co, until acquired by Western Publishing Co. in 1957). The original implementation consisted of a piece of black waxed cardboard and a translucent grey plastic sheet. One would write or draw on it with a plastic stylus, not unlike today's Personal Digital Assistants (PDAs). This quick-erase slate was called "Magic Slate", and became popular all over the world. In the USA, one can rather easily patent pre-existing devices and methods, so the Bernhardine Wachsschreiber was (re-)patented there in 2003 (US Patent 6,578,615) by the Hewlett-Packard (HP) company.

Magic Slate

Fig. 32: A "Magic Slate" note pad or doodle pad

In patent 767513, the tape moves around a drum. Spring-loaded rollers are used to maintain tension in the three layers of the tape. The layers are joined just before entering the printer window. Where the printer-spindle applies pressure to the tape, the silk tape sticks to the waxed paper and the pressure points become visible. Erasing is done by separating the silk tape from the waxed paper with a knife blade, after passing the printing window. See Figure 33. This is referred to as a "Wachsschreiber" or "Folienschreiber", i.e., a wax or foil (film) printer. This method was actually implemented during the 1936/37 development by Telefunken of the "Bernhardine 1m mit Wachsschreiber" of the initial UHF Bernhard/Bernhardine system (300 MHz, λ = 1 m). Ref. 2.

Erasable wax printer

Fig. 33: Concept of a "Bernhardine" erasable tape wax-printer

(source: adapted from Figure 3 and 4 in patent 767513)

Whereas patent 767513 proposes an endless tape, the 1940 patent 767536 proposes a triple-layer erasable disk. See Figure 34. Note that the threads on the two printer spindles are oriented the wrong way (turned 90 deg). The latter patent suggests that the drum-shaped wax printer has some serious disadvantages: 1) the tapes wear out and entire spare "drum + tape" modules must carried on the aircraft, and 2) imperfections in the drum surface (bumps, seams, out-of-round tolerances) cause failures.

Erasable wx printer disk

Fig. 34: Erasable-disk "Bernhardine" wax-printer

(source: Reichspatent Nr. 767536 , see patent table below)

Supposedly the erasable disk concept corrected these shortcomings. This is what was actually implemented in the Psch 120a "Bernhardine" printer. See Figure 35. It has about the same shape and size as the Psch 120 printer. Clearly, replacing an erasable disk would be easier than replacing a drum or installing a new tape, esp. given the tape tensioners. However, even replacing a disk would not have been easy either, given that the layer-separating blade must be inserted between two layers - without damaging the disk. This cannot have been easy, esp. not not with gloves and while maneuvering or during a bumpy flight. Indeed, the disk printer proved inadequate in operation: too complicated and unreliable. It was taken out of service, and retrofitted back to the Psch 120 paper tape printer.

Psch120a printer

Fig. 35: Peilschreiber "Psch 120a" of FuG 120b - an erasable disk printer

(source: page 101 in ref. 3; the large round "Dunkel-Hell" knob is for the ""dim/bright" setting of the "dial" light)

In the photo above, the printed compass rose segments cover about 30 degrees of azimuth. The bearing value "34" ( = 340 deg) is repeated 3-4 times during each pass, which means that the signal was not sent by a real ground station. Also, the station identifier is "D+" or "DT", rather than the standard single letter. These plots were probably created with a test signal generator at the factory. The photo also shows that the disk has room for about 5 passages of the beam of the ground station, before the oldest plot is erased.

Psch120 print out

Fig. 36: Enlargement of the PSch 120a photo above


Towards the end of the war, a much simplified Bernhard/Bernhardine system was under development. Its Bernhardine system was the FuG 120k, where "k" stands for "klein", i.e., "small". FuG 120k did not have the two-channel tone filter unit. Also, the printer-amplifier unit only had one channel and did not have the circuitry for creating the bar-graphs of the signal strength. Hence, the actual printer also only had a single printer mechanism, printed on narrower paper tape, and had no cam wheel on the spindle shaft. This made the entire system, and the printer, much smaller, lighter, and cheaper. It was intended for installation in single-seat fighter aircraft, where there is little space. Possibly also for the Ju88 (ref. 8).

Clearly, this Hellschreiber printer can only print the azimuth signal form the "Bernhard" ground station. There no longer is a pointer, previously formed by the V-shaped dip in the signal-strength track. One way to determine the azimuth, would be to visually determine the azimuth value in the middle of the azimuth plot. This is not so simple. But what if the azimuth signal is not transmitted via the single-lobe antenna system of the Bernhard beacon, but via the twin-lobe antenna system? Now the signal strength of the azimuth data has a dip when the null of the twin-lobe radiation pattern sweeps by the aircraft! See Figure 37B. As a result, the achievable accuracy was reduced from 0.5º or 1º, to ≈4º (cf. p. 87 in ref. 2, p. 125 in ref. 56, line item 56 in ref. 8).

High accuracy Bernhardine

Fig. 37A: Separate signal-strength bar graph and azimuth scale - high accuracy

Reduced accuracy Bernhardine

Fig. 37B: Azimuth data transmitted via the twin-lobe antenna system - reduced accuracy

Note that is concept is already mentioned in the original 1936 Lohmann/Telefunken main patent 767354. It also implies a simplification of the Bernhard ground station: only one transmitter is needed, and the single-lobe antenna array is no longer needed.

No photos or diagrams of this printer model are available.


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 38). It converts received tone-pulses to energization pulses for the printer's electro-magnet. The audio input signal is amplified, band-pass filtered, rectified. A final amplifier acts as a power-switch.

Hellschreiber printer-driver basic schematic

Fig. 38: Simplified principle diagram of a standard Hellschreiber printer-amplifier channel

However, the SV 120 is much more than just two such channels - see Figure 39. In total, there are 13 tubes (valves): five RV 12 P 2000 pentodes, five LV1 pentodes, and three LG6 dual-diodes (full-wave rectifiers).

SV120 diagram

Fig. 39: 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):

FuG120 pre-amp filter channel

Fig. 40: Pre-amplifier and filter

In the SV 120, these two audio signals are each passed through a separate two-stage amplifier. 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:

In the SV 120, the two filtered audio signals are each passed through a separate two-stage amplifier. 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, see Figure 41:

FuG120 bar-graph channel

Fig. 41: 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 42:

FuG120 azim channel

Fig. 42: 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.

pulse-width modulator (PWM) of the sv 120

The height of each printed bar must correspond to the signal strength at that moment. In a Hellschreiber printers, the height of a printed line segment is equivalent to the duration of the energization pulse that is applied to the printer's magnet-solenoid. Hence, the pulse duration must be between zero and 100% of the time that the printer-spindle takes to print one complete pixel column. So, to make this work, the amplitude of the received signal must be converted to the width of an energization pulse. This is done in two steps:

SV120 pulse-width-modulator

Fig. 43: Principle circuitry for voltage to pulse-width conversion

(source: Figure 4 in Rudolf Hell's patent 730625)

The drive-shaft of the printer-spindle (item 11 in the schematic above) has a notch (item 17). It actuates a switch (item 18) once per revolution of the spindle, when the thread of the spindle passes through its start position (bottom of the printed vertical line). Closure of the switch causes a capacitor (item 23) to be step-charged with a fixed supply voltage (item 24). As soon as the switch re-opens, the capacitor begins to discharge across a resistor (21). The value of the capacitor and its bleed resistor are chosen such that the discharge time is equal to (or slightly larger than) the duration of a single spindle revolution. This creates a sawtooth voltage, with a fixed amplitude and period. Clearly, the capacitor voltage is not linear but an exponential curve. The simplified schematic above does not show components that linearize this curve. Note that in the actual SV 120, the capacitor discharges via a choke coil, rather than a resistor.

The DC-amplitude EM of the received constant tone signal is applied across resistor (22). This superimposes EM onto the capacitor voltage. This sum is then offset with a fixed negative grid-bias voltage (20). The latter voltage is chosen such that if the input signal is zero, the anode current of the tube (valve, 19) is too small to energize the printer-solenoid. As soon as an input signal is present, the gain of the tube causes the anode current to exceed the energization level of the printer solenoid, and the spindle begins to print a line across the paper tape (bottom to top). For a small EM, the resulting energization pulse is short, and a short signal-strength bar is printed. For a large EM, a long signal-strength bar is printed. This analog technique is now referred to as "intersective pulse-width modulation", and was re-patented in the USA in the 1960s, with follow-on patents even after the turn of the century!

SV120 pulse-width-modulator

Fig. 44: Signal-level to pulse-width conversion and printing of the bar-graph

(adapted from Rudolf Hell's patent 730625)

Note that the above circuitry is for a printer spindle that has a single thread that is wrapped once around the hub of the spindle. However, the actual hub of the "Bernhardine" bar-graph has six partial threads (each covering 60° of the hub's circumference). This means that the spindle prints six consecutive columns per revolution of the spindle. To make this work, this printer has six notches on the spindle shaft, instead of just one. The pulse-width conversion circuitry is exactly the same, with the exception of the time-constant for discharging the timing capacitor.

SV120 pulse-width-modulator

Fig. 45: Plot of the actual pulse-width (h1 - h5) for a linearly increasing input-signal amplitude

(source: adapted from ref. 46)


The "Bernhard" navigation beacon has two AM transmitters. Their carrier frequencies were spaced 10 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 is 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 46. 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. 46: RF spectrum of the "Bernhard" transmitter outputs

(source: frequencies taken from ref. 15)

The FuG120 "Bernhardine" is operated in combination with an EBL3 shortwave AM navigation receiver. The audio output of the EBL3 contains both the constant tone from the "Bernhard" beacon's twin-beam antenna, and the Hellschreiber tone pulses that represent the azimuth symbology. See Figure 47.

RF and audio spectra

Fig. 47: Audio spectrum of the EBl 3 receiver output

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 audio filter unit ("Siebgerät"). See Figure 48.

SG120 block diagram

Fig. 48: Block-diagram of the SG120 2-channel audio filter unit

(source: frequencies taken 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). Note that the FuG120 manual (ref. 15, p. 42, Appendix e & f) suggests that the center-frequency of the two bandpass filters is the same as the modulation tones of the transmitters: 1800 and 2600 Hz. Of course, this is not the case, as the two carrier frequencies are spaced 10 kHz. Unfortunately, the manual only list the values of all the capacitors, but not of the inductors. So the actual filter characteristics can not be reconstructed (unless an SV120 unit is found).

RF and audio spectra

Fig. 49: Audio spectrum of the two SG 120 filter-channel outputs

The 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 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.


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.

This re-configuration is done with the SpKf 1a mode switch. This is just a re-labeled standard SpKf 1 "Sprechknopf" switch. The latter is used to switch a microphone on and off, like a push-to-talk switch (PTT). It has switch positions that are labeled "EIN" (on) and ""AUS" (off). Model 1a has the labels "LFF" ("Landefunkfeuer" = Landing Beacon) and NFF ("Navigationsfunkfeuer" = Navigation Beacon).

UG120 diagram

Fig. 49: Principle diagram of the UG 120 switching unit

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

The mode switch controls the UG 120 switching unit. This is basically a small box with a 4P2T relay (4 sets of changeover contacts). 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. 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.

F&H letterhead

Fig. 50: Letterhead of Friese & Höpfner

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 U 120 power supply unit includes 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 charging voltage for 24 VDC lead-acid batteries, like 13.8 is for 12 VDC batteries). 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. All connections to and from the MGA are passed through line filters, to suppress commutator noise.

The U120 has five outputs, that all go to the SV 120 amplifier unit.

The 300 VDC generator output is used for three of the five outputs:

U120 diagram

Fig. 51: Principle diagram of the U 120 power supply of the FuG 120

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

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 a 150 mA LG 6 dual-diode. Here again L = "Luftfahrtröhre", and G stands for "Gleichrichter" = rectifier. This tube was originally developed by Philips. The other two secondaries are down-transformed, to provide the required 12.6 VAC heater voltage to these two rectifiers.

U120 diagram

Fig. 52: Metall Stabilovolt M STV 140/60 Z tube (without extraction knob)


An estimated 2500 Bernhardine units were installed in various aircraft types (ref. 2, 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). Installation in the  Me 262 "bad-weather" fighter ("Schlechtwetterjäger") was decided in December of 1944; this was configuration "A 1 U 2" of the Me-262  (ref. 59). However,  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). A drawing exists that shows installation of the FuG 120a "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 something suspended from the canopy, though so far, no photos are available to positively identify the equipment. An RAF report on the Me 262 B-2a, also describes the FuG 120a as equipment intended for that type (ref. 63).

Other types of aircraft equipped with a FuG 120 were Junkers Ju 88G (ref. 64), Junkers Ju 388 (ref. 58B, 65), Arado Ar234 "Blitz" (ref. 66), and Dornier Do-335 A-6 "Pfeil". It may also have been installed in the Dornier P.254 (Do 435). FuG 120k appears to also have been intended for the brilliantly advanced flying-wing Gotha GO-P60 (Gothaer Waggonfabrik, GWF).

Messerschmitt Me-262

Fig. 53: The night-fighter version of the Me-262 - the world's first operational jet-powered fighter

(source:, no copyright (US Gov't))

Dornier Do-335

Fig. 54: Dornier Do-335 "Pfeil" with push-pull propeller arrangement

Junkers Ju-88

Fig. 55: Junkers Ju-88

Junkers Ju-388

Fig. 56: Junkers Ju-388J night fighter

Arado Ar-234B

Fig. 57: Arado Ar-234 "Blitz" - the world's first operational jet-powered bomber


Standard radio-navigation systems for instrument approaches ("blind landing" = by reference to instruments only) were the "Funk-Blind-Landeanlage" FuBl 1 and the FuBl 2 (initially written with a roman numerals I and II). Ref. 31, 32, 67, 68, 69. The airborne part of the FuBl 1 system is the EB.3, a militarized version of the Lorenz EB.2. This system was patented in the early 1930s by Ernst Kramar (Lorenz Co.) 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.

The FuBl 2 was basically an 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.

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

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 2 Ex receiver

Fig. 58: Receiver model "EBl 2 Ex"

(source: Figure 8 in ref. 32)

The only aircraft actually equipped with the EBl 3 were (ref. 74, p. 106 in ref. 2: the bomber version of the Ar-234, the nigh-fighter version of the Ju-88 and Do-335 (appendix II in ref. 8), Do-217 (ref. 75, 76), and the bad-weather fighter ("Schlechtwetterjäger") version of the Me-109, the Me-262 (ref. 25a, appendix II in ref. 8), 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.

EBL 3 receiver

Fig. 59: Receiver model "EBl 1 Ex"

(original unedited photo: courtesy Erich Werner, used with permisson)

EBl 3H turning

Fig. 60A: Receiver model "EBl 3H"

(courtesy Erich Werner, used with permission)

EBl 3H  receiver

Fig. 60B: Receiver model "EBl 3H"

(source: Figure 5.2 in ref. 78)

EBL 3 receiver

Fig. 61: "Landeempfänger" EBl 3 (lower equipment row, right of center) in a "Bordfunkanlage" FuG 10 P

(source: Figure 4.4 in ref. 78)

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

AS503-OS receiver

Fig. 62: Receiver model "AS503-OS"


FuG 138 "Barbara" was a small "Kommandoübertragungszusatz" (command uplink) attachment to the FuG 25A "Erstling" Identification Friend or Foe (IFF) transponder in bomber and fighter aircraft. This transponder was used in combination with Freya and Würzburg radar systems starting in 1941. The radar system included a transponder interrogation transmitter "Kuh" (125 ±8 MHz), and a "Gemse" receiver (156 MHz) to interpret the 10-bit reply codes of the transponders. Later in the war, the Luftwaffe developed the fighter control system "EGON": "Erstling Gemse Offensiv Navigation". "Barbara" could filter out Morse command messages that were superimposed onto the "Kuh" uplink transmissions. Major disavantages of this system are that the enemy could also read the command messages, and that it required pilots to pay attention to the Morse signals (distraction) and know how to "read" Morse code (not part of pilot training). Cf. §109-115 in ref. 8.

Late 1944, the FuG 139 "Barbarossa" was developed to "to improve the interference immunity of the "Bernhard" system, as well as simplify and further develop it" (ref. 81), thereby also overcoming the weaknesses of "Barbara". Development started mid-1944 at an institute of the Reichsstelle für Hochfrequenzforschung e.V. (RHF) at Bad Aibling near Munich.

"Barbarossa" was intended to work with the FuG 25A transponder and its successor, the Lorenz FuG 226 "Neuling", which was still in the prototype phase early 1945. Messages were uplinked to the transponder via Pulse-Position Modulation (PPM, a.k.a. Pulse-Phase Modulation), probably developed at Lorenz in Berlin or Falkenstein. This PPM used 30 μsec groups of three pulses. The position of the center pulse was varied in discrete steps, to encode information. PPM provides higher noise-immunity than Pulse-Duration and Pulse-Amplitude Modulation. Up to seven message uplink channels could be active on a single transponder interrogation frequency (ref. 82). The "Barbarossa" system included a filter/decoder unit and a Hellschreiber printer. The printer was developed from that of the FuG 120 "Bernhardine". The filter/decoder unit comprised a tapped delay-line ("Koinzidenzsieb") and converted the PPM signals to Hellschreiber pulse sequences. The first production batch of 200 units (out of an order of 1700 units) was supposed to enter into service in April of 1945 (ref. 83).

FuG 25 and FuG 226 were transponder systems that allowed the ground-station to determine the distance between aircraft and that ground-station (i.e., range). Only a small number of aircraft could be handled simultaneously by the system (and by the ground-controller). Clearly, this is incompatible with independent navigation by aircraft. Allowing the aircraft to interrogate the ground-station, rather than the other way around, solves this. The post-war implementation of this is the civil Distance Measuring Equipment (DME) system and the equivalent military TACAN system, both widely used to this day.

The first (and only) Luftwaffe transponder system that worked like this, was the Baldur system. Cf. §83 in ref. 8. It was developed during 1944 (ref.26A). The system comprised the FuSAn 729 "Baldur" ground-based transponder transceiver, and the FuG 126 "Baldur/Bord" transponder-interrogator transceiver onboard the aircraft. A further development of this was "Baldur K". The onboard FuG 126K system included a Bernhardine-type Hellschreiber printer.

If you have any additional information about the Barbarossa or Baldur/Bord system, please contact me!


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]
737102 RP 1937 R. Hell Dr.-Ing. Rudolf Hell Verfahren zur Registrierung des Verlaufes veränderlicher Stromkurven Method for printing the trace of varying signals [Hell printer for signal-level track of Bernhardine]
767513 RP 1939 A. Lohman 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]
767526  RP 1938 A. Lohman Telefunken GmbH Verfahren zur Richtungsbestimmung Method for direction finding
767527 RP 1938 A. Lohman Telefunken GmbH Einrichtung zur periodischen Ein- bzw. Ausschaltung einer Registriervorrichtung Device for switching on and off of a printer
767536 RP 1940 A. Lohman Telefunken GmbH Empfangsseitige Schreibvorrichtung zur Durchführung eines Verfahrens zur Richtungsbestimmung Receiver-side printer for the implementation of a method for direction-finding
767919 RP 1940 H. Muth Telefunken GmbH Verfahren zur Richtungsbestimmung unter Verwendung eines rotierenden Funkfeuers Method for direction-finding with a rotating beacon [using only twin-lobe beam]

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 - C. Lorenz AG Funkpeilverfahren Method for direction finding [transmission of compass rose info via Nipkow-video]

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


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

External links last checked: October 2015

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©2004-2015 F. Dörenberg, unless stated otherwise. All rights reserved worldwide. No part of this publication may be used without permission from the author.