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

Latest page update: November-December 2022 (added ref. 7L, 7S, 7T, and 7U)

Previous updates: June 2022 (expanded the "Goliath" section, added ref. 263D2); October 2021 (expanded the subsection on the MW.E.c receiver and added a subsection on the 30WS.a and Fig. 17B, added ref. 10C, 33A-33E); July 2021 .(added Fig. 71, added "Lorenz EO509" section; replaced Fig. 5); March 2021(added LA6NCA YouTube clip about Feld-Hell + Ha5K39b); October 2020 (expanded description of Feld-Hell / 15WSEb CW keying interfacing); June/July 2020 (added FuG 04 "Köln"); February 2020 (added section on Lorenz Posen I and II transmitter); September-November 2019 (expanded the Sägefisch IV part of the the Kw.E.a section, replaced ref. 6B with high-resolution file, added ref. 14J, 30A-30T).

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One of the Frequently Asked Questions that I used to get is: "Which radios did the German military use with the Hell Feldfernschreiber?" This page is an attempt to provide an answer. It primarily covers German military radios that are known to have been (or were intended to be) used in combination with Hellschreiber. I.e., there is documentary evidence (photos), or they have an explicit Hellschreiber interface (which, however, does not prove that they were ever used with a Hellschreiber). It is not my intention to provide an in-depth treatise on these radios, and the list may not be exhaustive. Undoubtedly, the Feld-Hell was used with other radios as well. Note that the title of this page is not "German military radios...." but just "Military radios...": the Feld-Hell was used by the military of several countries, often with their "local brand" radios.

It is important to note that the Feld-Hell was not intended for use with any particular receiver, transmitter, or transceiver. In principle, any radio suitable for fast CW (on-off keyed "Morse" telegraphy), AM, or FM communication could be used. FM modulation was used on UHF directional radio links, such as the "Michael" system. Feld-Hell does not appear to have been used with FM portable radios. Of course, had SSB radios been commonly available (see the "Performance" page), they could also have been used. During WW2, the Hell system was used with transmitters with an output power from several watts to 1 Megawatt! The radio range with Hellschreiber was similar to that of CW "Morse" telegraphy (ref. 1). Ref. 2A-2F provides a general overview of German military radios, 1920-1945.


Fig. 1: Communication range of several Wehrmacht transmitters and transceivers

(source: Fig. 54 in Chapter 8 of ref. 3)


Fig. 2A: one of the model-designator systems of Wehrmacht radios

(source: ref. 4)


Fig. 2B: another model-designator system of Wehrmacht radios

(source: ref. 4)

Note that the Kriegsmarine (German navy, 1935-45) used special Hellschreiber teleprinters that were built by the Hell company (models N2 and NS3). Both the Kriegsmarine and the Swiss army used "Presse-Hell" news-agency Hell printers.

The German 6th Army (with Axis forces) was surrounded at Stalingrad late November of 1942, and surrendered on 31 January 1943. It is sometimes suggested that the Feld-Hell was used as a "last resort" means of communication with the outside world. However, an estimated 90% of communication in and out of Stalingrad was done via Morse code telegraphy, and the rest via land-lines and UHF directional links (ref. 5B). Undoubtedly, units of the Wehrmacht Nachrichtentruppe (Signal Corps) in Stalingrad did have Feld-Hellschreibers, as this was standard equipment (ref. 5A). However, they were used for local communication.

The 6th Army included 20 Divisions. Each division had its own Nachrichtenabteilung (Na-section). Note that the 6th Army had already gone through battles before getting stuck in Stalingrad. Had this Army been at the nominal strength for 1938/39, the combined Na-sections would have comprised 380 (!) large Fernsprechtrupps (both motorized and horse-drawn units) and 100 mid-size & small motorized Fernsprechtrupps. The combined estimated nominal amount of telecom equipment would have been significant (ref. 5B, 5C, 5G):

  • 60x 100WS transmitter
  • 60x LW.E.a receiver
  • 380x Torn.E.b receiver
  • 40x 20WS.d transmitter
  • 40x UKW.E.d receiver
  • 40x UKW.E.f receiver
  • 160x 5WS transmitter
  • 80x Torn.Fu.b1 transceiver
  • 80x Torn.Fu.d2 transceiver
  • 60x Fu.H.E.u receiver
  • 60x Fu.H.E.v receiver
  • 20x "Enigma" crypto machine
  • 80 radio trucks (lorries)
  • 20 trailers with a Ladesatz D power supply

Furthermore, there were numerous motor-generators, pedal-powered generators, battery chargers, also UHF directional radio link systems, and additional radio equipment in tanks, weather stations, and for air traffic control.

Several weeks after the Germans were completely surrounded, a partial "Sägefisch" station was flown in, and probably also a second 70 W transmitter. A complete station included a Siemens-Halske automatic encryption/decryption teleprinter machine T-52 ("Geheimschreiber", British codename "Sturgeon") and a 1 kW Lorenz transmitter of the "Ehrenmal" series. Ref.5B-5E. The "Sägefisch" system used multiple frequency and dual rhombic-antenna diversity, and SSB modulation with partially suppressed carrier. It was highly dependable up to ranges of about 3000 km (ref. 5F). The 70 W and 1 kW transmitters were used at Army/Army Corps level. The Telefunken "Sägefisch IV" could also be used in combination with a Hell Feldfernschreiber (ref. 5H).

Of course, there were also Na-units and their equipment at Army Corps and Army level. Add to that over 2000 motorized vehicles, 640 motorcyles (Krafträder), 140 horse-drawn vehicles, over 1000 horses, field kitchens, etc. After the war, the total amount of discarded equipment (incl. both German and Russian tanks, guns and canons, and assorted vehicles) was so large, that the Soviet government built a steel plant in Stalingrad, to process it all...

If you have any additional information about radios that were used with the Feld-Hell but are not listed here, or have better photos, please contact me!


One of the standard Feld-Hell radio configurations is with the portable and mobile 100 watt medium-wave station Fu 11 SE 100. Note that "portable" is relative: two or three pack animals (mules) were required to carry the radios and the power generator. Anyway, this radio set consists of a Tornister Empfänger b (Torn.E.b) receiver and a 100 Watt Sender (100 W.S.) transmitter. The set was used by the Army ("Heer"), typically in radio trucks ("Funkwagen") such as the Kfz. 17 and Kfz. 61, the mittlerer Kommandopanzerwagen / Funkpanzerwagen Sd. Kfz. 251/3 IV, the schwerer Panzerspähwagen Sd.Kfz.232 (ca. 70 km radio range), and the schwerer Panzerfunkwagen Sd.KFz.263 (ref. 7C). Ref. 7A describes the use of the Fu 11 SE 100 with the Feld-Hell, by the Luftnachrichtentruppe (Luftwaffe Signals Corps).


Fig. 3: "Hellschreiber" is one of the of operating modes supported by the mobile 100 watt station

(source: ref. 28A)

The next figure shows a standard Luftwaffe interface configuration of the Feld-Hell with a 100 W.S. transmitter and a Torn.E.b. receiver. Both are AM and CW capable, but the equipment configuration below is for "AM" modulation. The "La - Lb/E" phone-line and "Empfänger" connector of the Feld-Hell are connected to the fax/Hell input connector of the 100 W.S., and the "Fernhörer" output connector of the Torn.E.b, respectively.


Fig. 4A: interconnection of a Feld-Hell with a "Torn.E.b." receiver and "100 W.S." transmitter

(source: ?)


Fig. 4B: Feld-Hell, "Torn.E.b" and "100 W.S"

Lorenz 100 Watt Sender (100 W.S.)

The "100 Watt Sender" transmitter was developed by C. Lorenz AG in 1934, as a successor to several 20 Watt transmitters of C. Lorenz AG and Telefunken. The original model designator was LS 100/108 (Langwellen Sender - longwave transmitter). This was changed in 1936 to 100 W.S./24b-108 and finally to 100W.S. in 1938. In the earlier designators, "24b" refers to the Wehrmacht equipment sub-category ("Stoffgliederungsuntergruppe") of radio equipment ("Funkgerät"). The items in each equipment sub-category were numbered consecutively. The "Gerätnummer" of this radio is 108. Ref. 6C.

The transmitter opereates in the frequency range of 200 kHz to 1.2 MHz (longwave + medium wave), divided into four bands. This is compatible with the longwave receiver Langwellenempänger a "Anton" (Lw.E.a, 72-1525 kHz), with which it was commonly used, as well as Tornister-Empfänger such as the Torn.E.b.


Fig. 5: The "100 W.S."

(source: adapted from ref. 6F)

Basic characteristics of the 100 W.S. are (ref. 6A, 6D, 6E, 6J):

  • Frequency range: 200 - 1200 kHz, covered by 4 bands
  • Output power: 100 watt (10 W selectable in CW mode)
  • Vacuum tubes: 1x RS 241, 2x RS 237
  • Power supply options:
  • motor-generator converter (dynamotor "Umformer") type U100, U100a, or U100a1 powered by a 12 volt DC radio battery ("Funksammler") type 12B75 (75 Ah)
  • for 1000 volt DC anode voltage (up to 300 mA) and 12 volt DC vacuum tube heater filament voltage (about 7 Amps).
  • generator type Kleinmaschinensatz c or c1
  • power supply type Netzanschlußgerät NA 8 in combination with an Elektromaschinensatz IV
  • transmitter rectifier unit Sendegleichrichter S.GL.T 100
  • Note: there was also as special version for 3-phase AC power.
  • Construction: 3-part die-cast chassis made of light metal alloy ("Elektron")
  • Size: 51x50.3x27.9 cm (WxHxD, ≈20x20x11 inch)
  • Weight (without the vacuum tubes): 33 kg (≈73 lbs)

Connecting the Hell Feldfernschreiber is very simple:


Fig. 6: instructions for connecting a Feld-Hellschreiber to a "100 W.S." transmitter

(source: 6A)

The "La Lb/E" phone line connector of the Feld-Hell machine is either connected to the special connector "Bildtelegrafie/Feldfernschreiber" of the 100 W.S. (located just above the "Mikr." microphone connector). When not used, a jumper is inserted into the latter connector. For AM ("Telefonie") transmission instead of CW ("Telegrafie"), the Feld-Hell's "La Lb/E" is connected to the microphone input of the 100 W.S.


Fig. 7: connector nr. 27 is for connecting a fax machine or a Feld-Hell machine (also see Fig. 8 below)

(source: ref. 6A)


Fig. 8: connector nr. 27 (shown with jumper installed) is for connecting a fax machine or a Feld-Hell machine

(source: ref. 6A)


Fig. 9: a "100 W.S." with "Kleinmaschinensatz C" generator and the "100 W.S. / Torn.E.b" range table

(source table: ref. 6A; range depends on which umbrella antenna or vehicle roof antenna is used)

A special keying device was available for the 100 WS. Tastzusatz Tz. (Fu) 100 WS. (ref. 6B). It comprised a fast keying relay: Siemens-Halske type T.rls. 54b (Bv 4/726). According to ref. 7B, remote keying could be achieved for distances of 3 km (≈2 mi) over regular "Feldkabel/Feldfernkabel" field phone lines, and up to 50 km (≈30 mi) over "Dauerleitung" permanent field phone lines. The same keying device was also used with the 15.W.S.b transceiver.


Fig. 10: patch cords and keying device of "Tastzusatz Tz. (Fu) 100 W.S."

(source: ref. 6B)

When using the 100.W.S. as a CW transmitter for a Feld-Hell machine, local printing of the sent text can be enabled with the methods discussed in the 15W.S.E.b section below.

Tornister-Empfänger b "Berta" (Torn.E.b)

The Tornister-Empfänger b ("Bertha") is a direct-conversion receiver ("Geradeausempfänger"). I.e., the frequency of the local oscillator is the same as (or close to) the carrier-frequency of the signal being received. This is as opposed to a superhet (superheterodyne) receiver, in which detection is done after conversion to an intermediate frequency (IF).

The unit is housed in a carrying case ("Tornister") and is battery powered (both heater and anode voltage of the vacuum tubes). It was one of the most widely used receivers (at least an estimated 150 thousand units built!), and was used by all branches of the Wehrmacht. It was used in combination with the 5 W.S. (radio set Fu 9 / SE 5), 30 W.S., 80 W.S., and 100 W.S. transmitters. Ref. 2B, 7A, 7B.

The Torn.E.b was one of an entire series of new "Tornister" ( = backpack portable) radios that were developed during throughout the 1930s. Ref. 7C-7G. The Torn.E.b entered into service in 1937. It replaced the Tornister-Empfänger model Spez. 445 Bs and Spez. 445 b Bs that dated back to 1931. Ref. 7G. Telefunken also marketed the Torn.E.b as a special receiver with the designator Spez. 976 Bs (ref. 7K, 7J). An export version of the Torn.E.b was developed in 1940. It has the designator Ae 1020, had an extended frequency range of 200 kHz - 15 MHz, and comprised vacuum tubes of type RV 2,4 P 700 rather than RV 2 P 800.


Fig. 11: the Tornister-Empfänger b (Torn.E.b)

Early models of the Torn.E.b were exclusively built by Telefunken (1937-39), later on also by Mende Radio, Saba, Sachsenwerk (in Dresden-Radeberg, ref. 7Q), Ostmarkwerke (in Prague-Gbell), and others. As the war progressed (1943), quality of the produced units declined. This was a general issue, not limited to the Torn.E.b. Increasing scarcity of raw materials and funds led to simplifications and modifications, such as elimination of the voltmeter (the mounting hole was covered by a metal plate), replacing the original light magnesium-aluminium alloy of the chassis and front panel with a 50% heavier zinc alloy, and reducing the size (and eventual elimination) of aluminium screening of RF sections.

Basic characteristics of the Torn.E.b are (ref. 30B):

  • Frequency range: 97-6970 kHz, covered by 8 bands
  • Modulation: A1 (unmodulated telegraphy), A2 (modulated telegraphy), and A3 (telephony).
  • Vacuum tubes: 4x RV 2 P 800 (ref. 7K):
  • Power for the vacuum tubes:
  • Heater: 2 volt / 0.8 amps DC heater battery (model 2B38) or electromechanical DC-DC chopper/vibrator supply ("Wechselrichter" model E.W.b)
  • Anode: 90 volt / 12 mA DC battery
  • Size: 36.5x24.5x22.5 cm (WxHxD, ≈14x10x9 inch)
  • Note: the matching Tornister case for the batteries and some accessories had the same size. The Tornister of the Torn.E.b was clipped on top of the battery Tornister, to form a single Tornister. Hence, both cases are also referred to as Halbtornister "half cases".
  • Weight: 11.3 kg (≈25 lbs)
  • Note: the battery Halbtornister weighed 12 kg (≈26.5 lbs).

The video clip below shows Helge Fykse (LA6NCA) demonstrating one of his Torn.E.b. receivers:

Helge Fykse (LA6NCA) demonstrating a Torn.E.b receiver

Telefunken receiver Spez. 445

The photo below shows a "first generation" Feld-Hellschreiber connected to a Telefunken receiver of type Spezial 445 (Spez. 445), installed in a Funkkraftwagen radio truck. This receiver is the predecessor of the Torn.E.b described immediately above, and successor to the Telefunken E 266x receiver (ref. 7G). It was used in combination with, e.g., the 5 W.S. transmitter (radio set Fu 9 / SE 5), ref. 7P.


Fig. 12: Telefunken receiver model Spez. 445 (left) connected to a "first generation" Feld-Hell (center)

(source: ref. 7L; the interface box (Fu)E/a to the right of the Feld-Hell is shown in Fig. 30B below)


Fig. 13: receiver model Spez. 445 Bs (left) and transmitter model 5 W.S.

(source: ref. 7A (Spez. 445) and ref. 7P)

The Spez. 445 entered service in 1932 (ref. 7P) and was built until some point in 1937. There were several versions, such as the 445 dBg (ref. 7N), 445 Bs and 445 b Bs (ref. 7M, 7T). The difference between the latter two is limited to the mechanical construction on the inside.

The receiver came standard with a shortwave ("Kurzwellen") frequency range of 2750-7500 kHz. As the tuned circuits of the receiver used air-wound coils (ferrite coil cores were not used yet), the coils were large. Covering other frequency bands required exchanging the coil set. Besides the coil set for "Kurz", there was an optional coil set for 500-3300 kHz "Mittel" ("Mittelwellen", mediumwave) for use with the 5 W.S.c transmitter (a.k.a. Spez. 469 Bs). For use with the 20 W.S. and 100 W.S. transmitters, there was a 100-1000 kHz "Lang" coil set ("Langwellen", longwave). Ref. 7N. These large coil sets ("Einschub mit Spulensatz") were plugged into the front of the receiver, see the oblong front panel with two frequency tables at the lower right-hand corner of Fig. 13 above.

This is a regenerative receiver - standard from ca. 1915 up to WW2. It uses a simple vacuum tube amplifier circuit with a positive feedback loop (re-generation). A gain control allows the operator to adjust the amount of feedback to the point just below or above the level at which self-oscillation occurs. The receiver's circuitry comprises four triodes of type RE 074 Neutron. The regular RE 074 was not to be used (unsuitable, per section III item 19 in ref. 7M). The "neutron" version was screened to tighter tolerances on the grid-anode ( = grid-plate) capacitance, heater current, and the oscillation operating point ("Schwingungseinsatz"). Heater voltage (at 250 mA) is provided by a 4.8 volt NiCad battery (Nickel-Cadmiumsammler 4,8NC10). Anode voltage is provided by a 90 volt anode battery (Anodenbatterie) at 8 mA. This battery has a 3 volt tap, for the grid-bias of the vacuum tubes.

The carrying case ("Tornister") of the Spez. 445 measures 36x47x23 cm (WxHxD, excluding the lumbar cushion on the back, ≈14x18.5x10 inch). The unit weighed 25 kg (≈55 lbs). Ref. 7M. The 5 W.S. basically had the same dimensions, and weighed 21.5 kg (≈48 lbs). It was also built in several versions: 5 W.S., 5 W.S.b and 5 W.S.c.

Kurzwellen-Empfänger a "Anton" (Kw.E.a)

Initially (1936-1941), the 100W.S. was used in combination with the Kurzwellen-Empfänger a (Kw.E.a "Anton") instead of the Torn.E.b. The Kw.E.a is beautiful super-heterodyne receiver that covers 980 kHz up to 10200 kHz with five bands. It has a single IF of 250.9 KHz. There is an RV 2 P 800 pentode vacuum tube (also used in the Torn.E.b) in each of the 11 stages of the circuitry. The radio consumes about 2.2 A at 2 volt for the tube filaments, and 20-25 mA anode current at 90 volt DC. The unit is battery powered, though a power supply model NA 6 can be used for the anode voltage. The unit is big: about 69x27x35 cm (WxHxD, ≈27x11x14 inch). It is also rather heavy: 42 kg (≈93 lbs), despite the die-cast chassis and front panel being made of lightweight "Silumin" aluminum-silicon alloy. Ref. 8A, 30E. This is a true "boat anchor" radio!


Fig. 14: the "Kurzwellen-Empfänger a" (Kw.E.a)

(source: on-line auction, 2015)


Fig. 15A: Two Feld-Hell stations with KwEa (or LwEa) in a Wehrmacht radio room

(source: © Fastner Collection/Sammlung; used with permission)

The KwEa was also part of the Wehrmacht's Sägefisch IV 9-channel radio teleprinter system with automatic encryption/decryption capability. This system includes three such receivers:


Fig. 15B: System configuration of the Sägefisch IV station

(source: ref. 8B)

Unlike earlier Sägefisch versions, the IV also included the capability to select "Hell Feldfernschreiber" ( = T.Typ.58) as operating mode:


Fig. 15C: Additional operating modes of the Sägefisch IV station

(source: ref. 8B)

The system included two large broadband Rhombic antennas. These directional antennas consist of one to three parallel wires that are suspended above the ground. Looking down on the antenna, it has a diamond shape. Combined with the three Kw.E.a receivers, the two antennas provided dual HF-diversity and 2x3 = 6-fold AF diversity.


Fig. 15D: Standard configuration of a Rhombic antenna

(source: ref. 8C)


The "Fahrbare 30-Watt-Mittelwellen-Station" is a mobile 30 W medium-wave transceiver set. It comprises the 30 Watt Sender (30 W.S.) transmitter and the Mittelwellen-Empfänger b (Mw.E.). It was intended for operation with a Hell Feldfernschreiber:


Fig. 16: operating modes of the "30 W.S." - telegraphy, telephony, and Hellschreiber

(source: ref. 9)


The Telefunken 30 W.S. 24b-120 is a medium-wave transmitter that covers 950-1670 kHz. Its modulation modes are A1 (unmodulated CW telegraphy), A2 (modulated CW telegraphy), A3 (AM telephony), and A4 (Hellschreiber). Output power is 30 watt in A1, and 12 watt in A2-A4. The Telefunken commercial designator for this model is "Spez. 657 A". The model was introduced in 1938. The circuitry comprises five tubes of type RS 241. Ref. 9A.


Fig. 17A: the 30 W.S. transmitter

(source: ref. 9A)

had a metal ring and rotary lever on the front panel, to select two fixed-but-variable frequency operating channels.

Around 1939, the above Telefunken model "30 W.S./24a-120" was replaced by the Telefunken 30-Watt-Sender a (30WS.a). It covered 120 kHz - 3000 kHz with 3 bands. It comprised six tubes: three RL12P35 35-watt power pentodes (power oscillator, power amplifier), two RV12P2000 pentodes (modulation), and (early vs. later version) either an RL12T15 triode or a third RV12P200 pentode (frequency calibration). Ref. 9B.

The "30WS.a" was used in reconnaissance vehicles ("Panzerspähwagen"), armored command vehicles, and command tanks. E.g., in the Panzer-Funkgerätesatz "Fu 8 SE 30", "Fu 20 SE 30", and "Fu 22 SE 30".which also included the Telefunken "Mw.E.c" receiver. It was also used with "Torn.E.B." and "Lw.E.a." receivers.


Fig. 17B: Initial version (left) and later version of the 30 W.S.a transmitter

(source right-hand photo: rkk-museum.ru)

A later version (1944/45) of the "30WS.a" had a metal ring and rotary lever on the front panel, to select two fixed-but-variable frequency operating channels. This convenient feature for operation in a wildly moving and shaking vehicle. Note that it was already part of the original "30 W.S./24a-120"! See Fig. 17A above. It was also added to other panzer radios, such as "10 WS.c", "20 WS.c", and "20 WS.d". See ref. 33A-33E for some details of panzer radios.


The Mittelwellen-Empfänger b / 24b-312 (Mw.E.b) is a superhet medium-wave receiver that covers the frequency range of 580 - 2000 kHz. The corresponding Telefunken commercial designator is E 434 A. It comprises six vacuum tubes of type RV 12 P 4000. Ref. 10A.


Fig. 18A: the Mw.E.b receiver

(source: ref. 10A)

Note: the Mw.E.b is not to be confused with the Mw.E.c "Cäsar" (though its codename was "Walter"). Ref. 10B. This model covers the frequency range of 830-3000 kHz in two bands. It is a very compact radio: 31x20x18 cm (WxHxD, ≈ 12x8x7 inch) and weighs about 13 kg (≈ 1.8 lbs).


Fig. 18B: Front of the Mw.E.c receiver

(source: adapted from ref. 10C)


Fig. 18C: Front & rear of the Mw.E.c receiver - covers removed

(source: adapted from ref. 10C)

The Mw.E.c comprised twelve vacuum tubes of type RV 12 P 2000. The "Mw.E.c" detector circuitry is a bit unusal: a pentode configured as double diode-triode.


There are several high-power transmitters that

  • The Wehrmacht "1 kW-Kurzwellensender" 1000 W.S.b (also 1 kW W.S.b) shortwave transmitter. Ref. 11A. It was manufactured by both Telefunken and Lorenz AG.
  • This is the military version of Telefunken's S 521 Bs transmitter. Ref. 11D, 11E
  • The Wehrmacht "1.5 kW-Langwellensender" 1500 W.S.a long-wave transmitter. Ref. 11F.
  • This is the military version of Telefunken's S 366 Ba transmitter. Ref. 11B.
  • The transmitter of the large 1.2 kW mobile shortwave station G1,2K (C-Station, SE-302) of the Swiss Army and the Swiss Air Force Radio Corps (Fliegernachrichtentruppe). The Swiss military acquired 16 of these units. They were built during WW2 (1940/41) under license from Lorenz AG, by Standard Telephon & Radio AG in Zürich/Switzerland. They remained in service until the 1960s. Note that the G1,2K station did include a Hellschreiber printer and sender, but the civil "Presse Hell" system rather than the military Feld-Hell.

These transmitters were developed ca. 1935-1936. The table below shows that they basically have the same design, so I have decided to group them. Another reason to do so, is that they are visually identical (other than the frequency scale).


Fig. 19: comparison of the 1 kW, 1.5 kW, and 1.2 kW transmitter

The associated manuals provide instructions for connecting a Feld-Hell machine and state "Hellschreiber" as one of the operating modes:


Fig. 20: instructions for connecting the Hell-Feldfernschreiber to a 1 kW or 1.5 kW transmitter

(source: §50 in ref. 11C)


Fig. 21: "Hellschreiber" is one of the operating modes of the "S 521 Bs" / "1000 W.S.b"

(source: ref. 11E)


Fig. 22: interfaces include Hellschreiber

(source: ref. 11D)

The next photos show the identical look of these transmitters:


Fig. 23: the fixed-base version of the 1 kW "S 521 Bs"

(source: 11E)


Fig. 24: the mobile version of the 1.5 kW "S 366 B"

(source: 11D, 11E)


Fig. 25: the mobile version of the "1 kW S.b"

(source: 11A)


Fig. 26: the 1.2 kW transmitter of the Swiss "G1,2K" mobile shortwave station

(the support-legs are for installation between the wheel wells of a radio truck, i.e., above the rear axle)


Fig. 27: the drawer with the transmitter keying circuitry

(2 tubes of type RS282 for negative-bias keying of the RS239 tubes in the PA; the "wheel" knob is for selecting the modulation/keying mode)


Fig. 28: the RS239 tubes of the final amplifier stage - glowing nicely during transmission

The transmitter could be installed in a radio truck version of the ubiquitous Kraftfahrzeug Kfz. 72. that was built from 1934-1942. The Kfz.72 was based on a 3-ton 3-axle Henschel type 33 "all terrain" truck chassis: Fahrgestell des mittleren geländegängigen Lastkraftwagens, offen (m. gl. Lkw. (o)). The D1 33 had a 6 cylinder gasoline (UK: petrol) engine. There were at least five different types of communication trucks based on the Kfz. 72:

  • Fernschreibkraftwagen (Fernschr. Kw.) - teleprinter truck
  • Fernsprechbetriebskraftwagen ( Fsp. Betr. Kw.) - telephone truck
  • Funkbetriebskraftwagen (Fu. Betr. Kw.) - radio operations truck
  • Funkhorchkraftwagen a (Fu. Horch Kw. a) - radio intercept truck A
  • Funkkraftwagen a und b (Fu. Kw. a & b) - radio truck A/B


Fig. 29: the Kraftfahrzeug "Kfz. 72"

These large, high-power transmitters were used for telegraphy, telephony, and Hellschreiber communication. In particular in the field, they were installed away from where the command authorities was located and where the associated Signal Corps group operated its receiver(s), teleprinter(s) and Morse keys. This was not only done to avoid interference, but also to minimize collateral damage when the transmitter site was discovered by the enemy (via radio directon finding) and attacked. Typically, the transmitter was located in one radio truck, the receivers and radio operators in another radio truck. The trucks were interconnected via a 3-wire cable. A rather simplistic interconnection and switch box was used in the operator's truck: the Umschalter (Fu)E/a. See Figure 30A. One of up to four input sources was selected with a push button, including Hell Feldfernschreiber ("Bildschreiber"). A milliAmp meter was used to monitor the current of the telegraphy keying relay or the connected carbon microphone. The latter was powered by 12 Vdc via the power connector on the front of the box. The microphone was isolated from the rest of the box with a 1:1 audio transformer, with grounded center tap.


Fig. 30A: Umschalter (Fu)E/a - front, side, and inside

(source: ref. 11G)

An even simpler (and much smaller) interface box was installed in the transmitter truck: Schaltkasten (Fu)S. See Figure 30B. It only connects the signal source selected in the operator's truck (voice/Hellschreiber audio, or telegraphy keying) to the transmitter. The name "Schaltkasten" suggests that it has at least one switch, but it has none. The required operating mode of the transmitter was communicated via a phone line between the two boxes. A standard field telephone (FF33) was plugged into the side of both boxes. As instructed, the transmitter operator then plugged in a short patch cord between the lugs of the 3-wire cable (marked "Fernleitung (3fach Kabel)" in Fig. 30B), and either the telegraphy key ("Taste") or microphone ("Mikrofon") jacks. These jacks were hard-wired to the transmitter.


Fig. 30B: Schaltkasten (Fu)S - front, side, and inside

(source: ref. 11G)


Fig. 31: mobile Wehrmacht station with a "first generation" Feld-Hell machine (yellow) with an Umschalter box to the right of it

(source: ref. 11J)


The Telefunken 15W.S.E.b is the 15 Watt Sende-Empfänger (transmitter-receiver) model version b. This CW/AM radio, including the antennas, is also referred to as "Fu 19" (FuG 19 SE 15). It was used by the infantry, and could be installed in armored vehicles. It covers the 3000-7500 kHz frequency range in two bands. The circuitry comprises nine tubes of type RV 2,4 P 700 (eight of which are in the receiver) and three of type RL 4,8 P 15. ref. 7B, 12A-12F.

VEF logo

The 15W.S.E.b was manufactured by Telefunken at the VEF factory (Valsts Elektrotehniskā Fabrika, State Electrotechnical Factory) in Riga/Latvia, starting in mid-1941. This company was founded in 1887 as the Russian subsidiary of the Berlin-based Union Elektrizitätsgesellschaft (UEG). UEG was absorbed into the AEG consortium in 1904/1905. The subsidiary became state-owned around 1919/1920, when Latvia became (temporarily) independent of Russia. At that time, it was renamed to "VEF", and then to "AEG Ostlandwerk GmbH" during the German occupation. Ref. 12A, 12C, 12H.


Fig. 32: operating modes of the "15W.S.E.b" - telegraphy (A1), telephony (A3), and Feld-Hellschreiber

(source: ref. 12G)


Fig. 33: the "15W.S.E.b" transceiver

This transceiver has a dedicated connector that is marked F.F Schreiber (for "Feldfernschreiber"), or just Schreiber. The connector is located at the lower left-hand corner of the front panel, just above the ground lug. Note that the 15W.S.E.a (built by Telefunken in Berlin, starting 1939) does not have this connector:


Fig. 34A: the 15WSEb (left) and 15WSEa - side by side


Fig. 34B: The 15WSEb input connector for the Hell Feldfernschreiber

This connector is for direct keying of the 15WSEb's CW transmitter with the character drum contacts of the Feld-Hellschreiber (accessible via the 12-pin connector on the front of the Feld-Hell machine). Per ref. 12G, the Tastzusatz Tz. (Fu) 100 WS remote keying device of the 100W.S. transmitter was supposed to be used to key the transmitter of the 15W.S.E.b. with the Feld-Hell machine.

Note: pins 3 and 4 of the 12-pin connector are used for keying of a CW transmitter keying. As stated above, when the 12-pin plug is inserted into the connector, the center pin of the plug opens a contact between pins 2 and 3 of the connector. See Fig, 11 and the detailed Feld-Hell schematic (Fig. 15) on the "Electronic circuitry & schematics" page. This is necessary, so as to avoid the constant 900 Hz signal from the Feld-Hell's tone oscillator from being connected to the keying input of the CW transmitter. Without interrupting the 900 Hz signal connection, the transmitter (e.g., a 15WSEb) could be keyed "on" permanently. It is connected to pin 3 via the switch contact, such that the character drum can key the 900 Hz tone. The 900 Hz signal is always present at pin 2. It was forseen to use the constant 900 Hz output (amplitude 2 Vpp) in an external CW keying device. In that device, the 900 Hz was up-transformed to 400 Vpp and rectified for use as a blocking bias voltage to key the CW transmitter. It would be pulled to ground by the Feld-hell's character drum when sending a pixel. See Fig. 35A and 35B below.

Feld-Hell CW transmitter interface

Fig. 35A: Connections of the 12-pin connector on the front of the Feld-Hell

Normally, the Feld-Hell prints prints not only received texts, but also the text that is sent. As a matter of fact, if a Feld-Hell machine receives signals while sending, both are printed simultaneously, on top of each other. As described in the note above, the 900 Hz tone signal is disconnected from the character drum when plugging in a 12-pin plug for keying a CW transmitter. So, when keying a CW transmitter, the sent text is not printed locally, unless the connected transceiver outputs a side-tone via its audio output. However, some CW transmitters (such as the WW2 15WSEb in "FF" mode) do not output a side-tone. In this case, there are several ways to ensure local printing, see methods A-D in Fig. 12. Method A is taken straight from the WW2 manuals (ref. 6B, ref. 12J). D. Bölke (DJ1LP) has shown that without the jumper between pins 4 & 5 (i.e., method B in Fig. 12), local printing is still active. He also found that jumpering pins 3 and 8 with a small capacitor also works (method C). The capacitor value is chosen such that there is no continuous keying of the CW transmitter. H. Fykse (LA6NCA) uses method D. Note that the volume setting on the Feld-Hell amplifier box may effect the  results.

Feld-Hell CW transmitter interface

Fig. 35B: Four methods for obtaining local printing when keying a CW transmitter with a Feld-Hell machine

For Hellschreiber transmission, the mode switch of the transceiver is set to "F.F Schreiber", see photo above. The modulator-amplifier tube (Rö7 in the schematic below) is configured as a tone oscillator during Hell-transmission. The resulting AC signal is passed through a rectifier/voltage-doubler circuit (diodes GL3 and GL4, capacitors C122-C125 and resistors W65-W67). This creates a negative grid bias voltage of -85 volt. This voltage is keyed by the drum of the Feld-hell machine, and used to grid-key the parallel amplifier tubes Rö2 and Rö3. When a drum contact is closed ( = send a letter pixel), the blocking bias voltage is shorted to ground, and a carrier signal is transmitted. See the simplified schematic below, as well as the detailed schematic of ref. 12G, and the description on p. 10 and 17 of ref. 12G. During Hellschreiber transmission, the heater voltage of the tubes in the receiver is turned off (see the switch in the lower right-hand corner of the schematic below). For reception, the mode switch is set to "Empfang Tg" (Telegraphy reception).


Fig. 36: Principle schematic for Feld-Fernschreiber transmission

(source: ref. 12F)

The transceiver is housed in a "Tornister" backpack carrying case that measures 34x42x22 cm (WxHxD, ≈13.4x16.5x8.7 inch). The set weighs 19.5 kg (≈43 lbs). Size and weight are similar to that of the Hell-Feldfernschreiber.


The Telefunken T 9 K 39 "Main" is a superhet shortwave receiver that covers the 1.5 - 25 MHz frequency range with 8 bands. It was primarily used in U-boats and coastal stations of the Kriegsmarine.

As the type designator suggests, it entered into service in 1939. The "9" in T 9 K 39 indicates the number of tuned stages: 3 HF-stages, each with an RV 12 P 2001 pentode, a mixer stage with an RV 12 P 2000, two IF stages (RV 12 P2001 and RV 12 P2000), a detector, AF, and a BFO stage, each with an RV 12 P 2000. The unit is big and heavy: 55x29.5x33 cm (≈22x12x13 inch) and 45 kg (≈99 lbs). The unit has an IF crystal filter with a continuously variable bandwidth (100 Hz - 5 kHz). The frequency scale is displayed via rear-projection of a microfilm onto a small frosted glass plate. Many features of T 9 K 39 have been employed later in the famous Telefunken E 52 and E 53 receivers. ref. 13A, 13B.

The unit has two audio outputs: one with a 10 volt amplitude for a high-impedance headset, and one with 1 volt amplitude, for a Hellschreiber or an external audio amplifier.


Fig. 36A: the Telefunken "T 9 K 39" receiver


Fig. 36B: the Telefunken "T 9 K 39" receiver with antenna selector/coupler attached on the right hand side


The Telefunken E52 "Köln" was one of the four standard receivers of the "Luft-Boden-Empfänger" development program of the Luftwaffe, for ground-based operation. They were named after the cities "Leipzig", "Köln, "Ulm", and "Kulm", and were intended to cover the 40 kHz to 150 MHz frequency range. Ref. 14A. These radios were specified in 1939. Initial production of the E52 started in 1942, and full production in 1943. The E52 is the shortwave receiver ("Kurzwellen, hence the "K" in "Köln") for 1.5 to 25 MHz. It was primarily used in fixed-based and mobile stations of the Luftwaffe. The equivalent Kriegsmarine designator is T 8 K 44. It is an evolution of the Telefunken T 9 K 39 "Main", with improvements and simplifications. Ref. 14B-14J, 30D.


Fig. 37: the Telefunken "E52" "Köln"

This is a fully modular radio. All modules are fully RF-screened and plug into a special backplane module that connects all other modules. The chassis is die-cast light metal. Mechanically and electrically, this is probably by far the most elegant and beautiful receiver of WW2. Construction and performance was far ahead of its time, and unequalled by Allied radios through the 1960s. Due to extensive temperature compensation, the free-running oscillator has exceptional stability. Like the T 9 K 39, it has a rear-projection frequency scale with a microfilm. Each unit had a "personal" microfilm that was specific to the frequency characteristics of that particular individual receiver. In total, ten RV 12 P 2000 pentodes are used in the various receiver stages (except the power supply). Also like the T 9 K 39, it has a crystal IF filter with variable bandwidth. Ref. 14H. Some ten variations of the E52 were developed. The differences are primarily related to manual and motorized tuning. The latter was another electro-mechanical achievement: frequencies could be memorized mechanically, and be recalled - with enough accuracy (about 50 Hz) to not need manual re-tuning.

The E52 has two audio outputs: one for a high-impedance (4000 Ω) headset, the other for a standard phone line (600 Ω). A special high-power audio output module was foreseen, for driving a Hellschreiber:


Fig. 38: special high-power AF final-amplifier module for driving a Hellschreiber ("Presse Hell")

(source: ref. 14A)

With this special module instead of the standard audio output module, the radio was model variant "E52d". There is no documentary evidence that this special module was ever designed, let alone produced.


Fig. 39 "Köln" model "E52d" was to include the Hellschreiber AF final-amplifier module

(source: ref. 14B)

It is unclear for which type of Hellschreiber the special audio output module was intended. The Hell Feldfernschreiber can be driven by the loudspeaker output of any radio receiver. In fact, it needs a signal with a minimum amplitude of only 18 mV. Note that the E52 does not have a loudspeaker output. I do not know the signal level at the phone-line output, but it is probably around 1 volt. So, the special module may actually have been intended for driving the solenoid of a "Presse Hell" printer: 20 mA at about 30 volt.

Helge Fykse (LA6NCA), printing signals from an E52 "Köln" receiver with a Feld-Hell machine

source: YouTube


The type designator T 200 FK 39 tells us this is a 200 watt transmitter made by Telefunken, for Kurzwellen (Fernverkehr), i.e., long-distance shortwave. FK covers 6-30 MHz; the T 200 FK 39 covers 3 - 23 MHz. It entered into service in 1939. It was suitable for installation on board of ships. It was standard equipment on Kriegsmarine U-boats that operated in the south Atlantic and Pacific. This is yet another mechanical masterpiece, with excellent performance, notably extreme stability of the free-running oscilator. Ref. 15A, 15B.

Four operating modes are selectable: modulation types A1, A2, A3, and "TBS": Typenbildschreiber, i.e.., Hellschreiber. Note: this only applies to T 200 FK 39a and T 200 FK 39b, and not to the initial T 200 FK 39.


Fig. 40: position "TBS" of the BAW "Betriebsartenwahlschalter" (operating/modulation mode selector)

(source: 15A)

Above, the "tragbaren Typenbildschreiber" refers to the portable Hell-Feldfernschreiber ("Feld-Hell").


Fig. 41: operating modes (modulation types) of the "T 200 FK 39"

(source: 15A)


Fig. 41: the "T 200 FK 39" tower (power supply not shown) and the priciple schematic

(source: 15A)


The Ha 5 K 39 is a shortwave transceiver that was developed and built by the company Hanseatische Apparatebau-Gesellschaft ehemals Neufeldt und Kuhnke GmbH (Hagenuk) in Kiel/Germany (a major navy port). The company was founded in 1899 and simply named Neufeldt & Kuhnke until 1936. This radio entered service with the Kriegsmarine in 1939, where it was widely used on (small) ships, in land stations, and in vehicles of motorized signal corps units ("motorisierte Marine-Nachrichteneinheiten"). Towards the end of WW2, it was also used on conscripted merchant ships. The company Radiotechnische Fabrik Dipl.-Ing. Nikolaus von Eltz (trademark Radione) in Vienna/Austria built the unit under license. Ref. 16A, 16B, 16-C, 24C-2.


Fig. 43: Hagenuk "Ha 5 K 39c" shortwave transceiver

It is a relatively compact desktop transceiver (52x35x24 cm, ≈20.5x14x9.5 inch; 22 kg, ≈48 lbs). All versions of this radio (Ha 5 K 39, 39a, 39b, and 39c) support the standard modulation modes A1 (5 watt), A2 and A3 (1.5 watt). Model 39 and 39c cover a frequency range of 3 - 6 MHz, whereas 39a and 39b cover the range of 2 - 5 MHz. All vacuum tubes are of type RV 12 P 2000, except for the RL 12 P 10 power pentode in the transmitter's final amplifier, and a GR 150/A voltage stabilizer.

In models 39b and 39c, both the transmitters final amplifier tube and the modulator tube can be cathode-bias keyed with a Feld-Hellschreiber. In Hell-transmission configuration, the keying-relay is continuously energized and the cathode of both tubes is biased "off" with a large resistor to ground. This resistor is bypassed by the keying contacts of the Hellschreiber. During Hell-transmissions, the modulator only serves as sidetone generator.


Fig. 44A: description of the transmitter keying in Hellschreiber mode


Fig. 44B: instructions Hellschreiber hook-up and transceiver operation

(source: ref. 16C)

One of the connectors in the lower left-hand corner of the front panel, there is a 3-prong keying input for a "Morse" telegraphy key ("Taste") or a Hell-Feldfernschreiber (Typenbildschreiber, T.Bild-Schr.):


Fig. 45: keying-input connector and mode-selection for a "T.Bild-Schr." (Typenbildschreiber = Hellschreiber)

Helge Fykse (LA6NCA), demonstrating his Ha5k39 transceiver and Feld-Hell machine (2021)

source: YouTube


The very rare Hagenuk Ha 15 K 42 is a shortwave transmitter (3 - 6 MHz) with an output power of 15 watt (A1 modulation; 5-6 watt in A2/A3) that entered into service in 1942.


Fig. 46: front panel of the Hagenuk "Ha 15 K 42"

(source: www.cdvandt.org)

Like the Ha 5 K 39, the Ha 15 K 42 has a keying input on the front panel, for connecting a Hell Feldfernschreiber. The "BAW" operating mode selector switch has separate positions for Hellschreiber transmission ("T.-Bild S") and reception ("T.-Bild E"):


Fig. 47: Hellschreiber transmit & receive mode selection and Hellschreiber keying input

Also like the Ha 5 K 39, all vacuum tubes are of type RV 12 P 2000, except for the power pentode in the transmitter's final amplifier. However, here, an LS 50 is used, rather than the RL 12 P 10.


The Lorenz Lo 70 KL 40, also referred to as "Marine-Kleinfunkgerät" and "Marine Gustav", was used for ship-to-ship and ship-to-shore communication in the Kriegsmarine. It covers both long-wave (300-600 kHz) and shortwave (1.5-7.5 MHz, covered by three bands). The set comprises a transmitter-receiver (separate modules in a single case) and an antenna coupler unit. The receiver comprises 7 stages, with ten vacuum tubes of type RV 12 P 2000 in total. There is a separate IF for long-wave and shortwave. The transmitter comprises three tubes of type LS 50. Output power is 70 watt (A1 modulation) or 40 watt (A2/A3). Overall size is 81.4x44x36.7 cm (WxHxD, 32x17x14.5 inch), with a weight of 76 kg (≈167 lbs). Ref. 18A.


Fig. 48: left to right - receiver, transmitter, antenna tuner/coupler

The connector block on the front panel of the transmitter has separate connectors for Hellschreiber transmission ("Typenbild-Send.") and reception:


Fig. 49: connectors for Hellschreiber transmission & reception are on the front panel of the transmitter

(source: Yuri Desyatnik)

The manual (ref. 18A) lists Hellschreiber transmission and reception as two of the five operating modes, as well as suitability for operation with a Hell-Feldfernschreiber:


Fig. 50: operating modes of the 'Lo 70 KL 40"

(source: ref. 18A)

The output to the Feld-Hellschreiber is simply connected in parallel with the headset output. In Hell-transmission mode, the transmitter is basically keyed just like in the "Morse" telegraphy mode: the keying contacts of the Hell-Feldfernschreiber directly (i.e., without a keying relay) key the suppressor grid of the three transmitter tubes, by pulling the +400 volt grid-blocking bias to ground. Note that this implies that one side of the connector is permanently connected to +400 volt - do not touch!


Fig. 51: simplified schematic of the transmitter configuration in Hell-transmission mode

(source: Fig. 7 in ref. 18A)

The radio was designed by C. Lorenz AG, in Berlin-Tempelhof, but built in occupied Czechoslovakia by the company Telegrafia, akc. spol., in Pardubice (ca. 130 km east of Praha / Prague). The company was founded in 1919, nationalized in 1946 and absorbed into the TESLA Narodny Podnik conglomerate. After 1945, the Lo 70 KL 40 continued to be made and used in Czechoslovakia, with the model designator "Jalta". Ref. 18B.


Fig. 52: the "Telegrafia" factory in Pardubice

(source: unknown)


Towards the end of WW2, the Lorenz company in Falkenstein/Saxony developed the shortwave transmitters "Posen I" (3-25 MHz, 100 W) and "Posen II" (same, but 1.4-12 MHz and 150 W) for the German army ("Heer"). Production (under license, by the Schneck company in Vienna/Austria) had just started when the war ended (ref. 31C).

Posen transmitter

Fig. 53: Posen I & II transmitters were intended for use with a Feld-Hellschreiber

(source: ref. 31A)

Posen transmitter

Fig. 54: Hellschreiber keying-input on the front of the Posen I transmitter

(source: ref. 31B; the front panels are not painted, possibly a production-ready prototype or material/cost savings)


The Telefunken AS 11 transmitter was marketed by Telefunken in combination with the Telefunken receiver model Spez. 976 Bs", as the "Portable and Mobile 100 watt station for medium wave". The receiver is also known by its military designator Torn.E.b described further above. The As 11 transmitter covered the 200 - 1200 kHz frequency range with four bands. This corresponds roughly to the high end of the long-wave band through the middle of the medium wave broadcast band. The receiver covered a wider frequency range: 100 - 6670 kHz. The As 11 measured 37.5x51x31.7 cm (HxWxD, ≈14.8x20x12.5"), and weighed about 25 kg (≈55.3 lbs). Ref. 28A.

The As 11 had an output power of 100/20 watt in A1 modulation mode (CW telegraphy), and 25 watt in A2/A3 mode (AM telegraphy & AM Hellschreiber). This transmitter also had a jack on the front panel for connecting the keying output of a Hell Feldfernschreiber:


Fig. 55: Operating modes of the 100 W medium wave station - the transmitter has an input jack for a Hellschreiber

(source: ref. 28A)


Fig. 56: Telefunken 100 watt medium-wave transmitter model As 11 - Hellschreiber connector marked with magenta box

(source: ref. 28A)


The Telefunken AS 59 transmitter was intended for mobile (ship board and vehicles) as well as fixed-base installations. It covers the 2.5-20 MHz shortwave frequencies with 6 bands. Output power of the AS 59 is 200 watt (A1 telegraphy) or 50 watt (A2/A3). It was often used in combination with the Torn.E.b. and Kw.E.a receivers.


Fig. 57: the Telefunken "AS 59"

The front panel has a keying-input connector for a Hellschreiber:


Fig. 58: "AS 59" interfaces - with Hellschreiber keying input ("Hell-Taste")

Hellschreiber transmissions can be done both in CW mode (A1, unmodulated telegraphy), and A2 (modulated telegraphy) with the tone-generator that is built into the AS 59:


Fig. 59: the operating modes of the AS 59

(source: ref. 19A)

This radio was built under license by other companies in Germany, and in Switzerland. During the war, the AS 59 was also built in France, by Société Française Radioélectrique (S.F.R.), in their factory at Levallois-Perret near Paris. Over 1000 units were delivered to Telefunken. S.F.R. already had connections with Telefunken before WW2, and the S.F.R. sites (Levallois and Cholet) in occupied France were put under control of Telefunken during the war and produced Telefunken-designed equipment. Ref. 19B, 19C.


Fig. 560: equipment label of an AS 59 built by S.F.R. for Telefunken

This radio was also used in the "Maikäfer" stations, to report A4-missile ("V2") launches and trajectories to headquarters. Ref. 19D. Germany sold a dozen of these sets to Spain in 1943. Ref. 19E.


The As 60 transmitter was initially built on a small scale in 1943 by Telefunken in Germany. Then it was built under license by Autophon AG in Solothurn/Switzerland and exported to Germany. This continued until sometime in 1944 (!), when the Allied nations were finally successful at forcing Switzerland to stop supporting Nazi Germany. At that point, Telefunken moved the production to a plant in occupied Czechoslovakia, some 160 km east of Prague. As a side-note: in general, license fees continued to be paid by US companies to German companies - and vice versa - via Switzerland, until well after the USA entered the war in 1943. Autophon also produced a derived model of the AS 60 transmitter for the Swiss army, as part of their motorized shortwave station M1K.


Fig. 61: two versions of the "AS 60"

(source: ref. 20A, 20B)

This shortwave transmitter covered the frequency range of 3 to 25 MHz with 6 bands. In A1 modulation mode (unmodulated "Morse" telegraphy), output power varied from 1.4 kW at the low frequency end, to 1.1 kW at the high end. There was a version of the AS 59 with only half that output power: it only had one instead of two RS 384 power vacuum tubes in the final amplifier. With A2 and A3 modulation, output power was only 300-350 watt (or 175 watt with a single RS 384). Hellschreiber transmission operation was done with either A1 or A2 modulation. In A2 mode, the Hellschreiber keyed a constant tone that was generated by an oscillator in the AS 60 itself ("Eigenton", selectable 800, 900, or 1100 Hz). The transmitter can also be keyed with tone-pulses from an external source. These are then rectified and fed to the keying tubes as a negative grid-bias, just like local tone pulses.


Fig. 62: modulation types supported by the "As 60"

(source: ref. 20A, 20B )


Fig. 63: remote Hellschreiber keying (i.e., over a distance of more than 1 km) is done with tone-pulses rather than direct keying

(source: ref. 20A, 20B)


Another shortwave transmitter of the Telefunken "AS" series is the AS 1008. This transmitter has an output power of 200 watt with A1 modulation, and 130 watt with A2 and A3. It covers the shortwave frequency range of 2.5 to 10 MHz. It was part of the mobile 200 watt station with provisions for Feld-Hellschreiber ("Fahrbare 200-Watt-Station mit Einrichtung für Siemens-Halske Hellschreiberbetrieb") installed in radio trucks. The receiver of the "200 watt station" covered 1.25 to 21.43 MHz.


Fig. 64: the "AS 1008" with power supply (left) and the mobile 200 W station with Feldfernschreiber (foreground) and an "AS 1008"

(source: ref. 21A )


Fig. 65: the 200 watt transceiver station with "AS 1008" transmitter supported Hellschreiber

(source: ref. 21A)


The Telefunken longwave equivalent of the above AS 1008 200 watt shortwave transmitter is the S 354 A (civil/commercial designator). Again, 200 watt with A1 modulation, and 130 watt with A2 and A3. the associated Telefunken long-wave/mediumwave receiver covered 75-1500 kHz


Fig. 66: the "S 354 A" transmitter supported Hellschreiber transmission

(source: ref. 22A)


Ca. 1937/38, the small decimeter-equipment "Dezimetergerät 4 Klein(gerät)", or "DMG 4 K" for short, was developed for the Luftwaffe. It was also known as "Michael I", and formally as "Richtverbindungsgerät K" (Directional Radio Relay "K"). This transmitter-receiver system worked with wavelengths of 54-60 cm which is 5.4 - 6 decimeter, hence the designation "Dezimetergerät". This is equivalent to the UHF frequency range of 500-560 MHz. At these frequencies, the radio horizon is actually slightly larger than optical line-of-sight. Highly directional antenna systems were used. "DMG 4a K", or "Michael II", was a 1940 update of "Michael I".

The "Michael II" communications channel could be used for either a single voice channel (telephone or broadcast radio), or up to three simultaneous "two-tone" telegraphy/teleprinter channels. Transmitter output power was about 0.3 watt. Ref. 23G. It was the first UHF directional radio link system in which the transmitter-receiver and the associated AF part of the system were not collocated with the antennas. Instead, they were implemented as modules in an equipment rack, located up to 50 meters away from the antenna, via coax cable.


(source: ref. 23A)

Hell-Feldfernschreiber communication was done with 900 Hz tone pulses via the voice channel, the same as over wired telephone lines:


Fig. 67: Operating modes - Channel 1 is used for telephony and Hellschreiber teleprinting

(source: ref. 23A)


Fig. 68: Hell Feldfernschreiber can be used over any DMG telephony channel

(source: ref. 23H)

The Lorenz Zweikanal Dezimeter Ferntastanlage FuG 04 "Köln" is a mobile version of the 2-channel "DMG 3 K" ("Florian"), but with a modified Channel 1 (voice band), such that it could be used for simultaneous (instead of mutually exclusive) operation of voice and 900 Hz Hellschreiber. This required additional audio filters in the control rack. Channel 2 (6 kHz remote transmitter keying) was the same. The UHF transmitter and the receiver units were both mounted directly at their respective antenna. Each of these two vertical antennas comprised a dipole + reflector + 3 directors. They were mounted next to each other. The system operated in the 475-525 MHz band (i.e., a wavelength of ca. 60 cm = 6 decimeter) Only about 40 of these systems are supposed to have been built.


Fig. 69: Radio truck with 2 sets of FuG04 / DMG 3K transmit & receive antennas and a control rack

(source: ref. 11G, 11H)

The documentation of subsequent DMG models such as DMG 7 K/aK do not explicitly mention Hellschreiber operation. However, any communications channel suitable for voice/telephony, is more than suitable for Hellschreiber.

The maps below show the network of the Luftwaffe UHF directional communication links. Understandably, the network branches out from Berlin, with - at some point in time - an "orphan" sub-net towards Moscow.


Fig. 70: network of Luftwaffe "Michael" UHF directional radio relays (late 1942?)

(source right-hand image: Fig. 12 in ref. 23F2)

There are sources that state that the UHF relay network with various models of "Michael" equipment, had a total combined length of 50 thousand or even 70 thousand km (about 30 and 44 thousand miles, respectively). The 70 thousand km total length may be a 1950s estimate from Telefunken, based on adding up all network "legs" that were ever built up, but were never all active at the same time. Note that the network "nodes" typically moved with the fronts as the war evolved. The 50 thousand km estimate is from a later date. It may reflect the maximum total network size that was active at any given time. Unfortunately, no records are known to exist that can be used to reconstruct and validate these estimates. Ref. 23C.

There are also statements and claims about the longest single end-to-end network path having a length of 5 or 7 thousand km. Based on the signal-to-noise performance of the UHF relays, such distances could only be covered with a combination of UHF relays and cables (or cable-only). Actual range of the relays was not explicitly specified. It was recommended not to exceed a total length of 300 km ( = five "hops" of 60 km each). Ref. 23D. Each UHF relay company ("Richtverbindungs-Kompanie") of the Wehmacht signal corps comprised twelve "Trupps". Each "Trupp" had one UHF transmitter and one receiver (plus mast with antennas), and could form one end-station or one relay station. Hence, at company level, a stretch of about 400 km could be covered.

Note that in the Luftwaffe as much as 80% of communication was via radio relays, whereas in the Heer (army), about 80% was via wired lines.


The next photo shows the 1940 communications wagon of the Reichsbahn "Sonderzug" (special trainset) of Mr. Heinrich Himmler, Hitler's Reichsführer-SS:

Hell MS3 Morseschreiber

Fig. 71: "Salon-.Nachrichtenwagen" wagon type "Sal N 6ü 39a", serial number "10 255 Bln"

(source: adapted from ref. 32A, 32B; orignal photo by wagon manufacturer Wegmann & Co.; note: wagon "10 253 Bln had a telescopic mast at both ends)

The telescopic T-antenna was only cranked up while parked. Two antenna wires were strung along the entire top of the wagon. The equipment of the radio operating room ("Funkbetriebsraum") included a Feld-Hell machine and an MS3 Hell Morse-printer:

Hell MS3 Morseschreiber

Fig. 72: Equipment in the radio operations room of "10 255 Bln"

(source: adapted from ref. 32A (also in ref. 32C); orignal photo by wagon manufacturer Wegmann & Co.)

As the Lorenz EO 509 general-coverage receiver (ref. 32D) is located directly next to the Feld-Hell machine and directly below the MS3 Hell Morse printer, it is assumed that the receiver was used with both.

The transmitter was located behind the position of the photographer. The photo was taken towards the left in the diagrams of Fig. 71. The wagon also included a teleprinter room, a telephone exchange (switch board) room, a message cipher/crypto room, a Signals Officer room, and a generator room (12 kW, diesel powered; a second generator was gear-driven by an axle of one of the two triple bogies). The rail wagon was built by Wegmann & Co. in Kassel/Germany.


The Kriegsmarine used the Hell-system with an LF/VLF transmitter that was absolutely gigantic, both in terms of size of the antenna system and output power. It was appropriately named Goliath, and was used for world-wide broadcast to (submerged) submarines. In its time, it was by far (!) the world's most powerful vacuum tube transmitter with tunable frequency: close to 1 Megawatt at 15-60 kHz, i.e., a wavelength of 5-20 km! Ref. 24A1/2/3/4/5/6/7/8/9/10. There were 12 crystal-controlled frequencies ( = very stable), in addition to the freely tunable frequency range. Below 19 kHz, the output power had to be reduced, as the narrow bandwidth of the antenna system ( = high Q-factor) caused excessive voltages.

Goliath had the following operating modes and associated radio frequencies:

  • CW ("Morse") telegraphy: 15-60 kHz (primary frequency: 16.55 kHz, i.e., λ = 18.13 km). The transmitter was keyed via dedicated phone lines from the German navy's control center "Koralle", about 145 km (≈90 mi) to the east. This remote-keying was done with 900 Hz tone pulses, that were then converted back to on-off pulses by keying equipment at the transmitter (p. 166 and note 28 in ref. 24B2).
  • Hellschreiber: 30-60 kHz (AM, tone pulses). Available documentation does not state why AM was used, instead of on-off-keyed CW. Most likely, the transmitters CW keying circuitry was not fast enough for the short Hellschreiber pulses. Feld Hell transmission speed is equivalent to 25 "Morse" words per minute (WPM), i.e., 125 average Morse characters per minute, where the word "PARIS" is the considered the standard 5-character word. 25 WPM is not fast for professional telegraphists. Presse Hell is twice as fast, i.e., 50 WPM. Also see the "bandwidth & duty-cycle" page. Since 2003, the ITU allows countries to choose whether to drop the Morse code proficiency test from amateur radio license exams. In the UK and the USA, the highest speed test was 30 WPM and 22 WPM, respectively (I passed the 17 WPM test in 1989 for for my "Advanced" license). The world record is around 140 WPM.
  • Voice/phone: 45-60 KHz; voice quality was rather low, due to the very small bandwidth of the high-Q antenna system. With the same modulation, Hellschreiber could be operated down to 30 kHz, at which the bandwidth was much too small for voice transmission. See the table below. Note: conventional "POTS" telephone systems have a bandwidth of 300-3300 Hz!


Fig. 71: The very small bandwidth of the Goliath antenna system at various frequencies

(source: p. 189 in ref. 24A1)

CW and Hellschreiber messages could be sent in combination with the famous Enigma encryption system (ref. 24E-1, 24E-2).

The 15-60 kHz frequency range was used because it provides world-wide coverage, and these radio signals penetrate seawater sufficiently to reach submerged submarines. Penetration depth depends on factors such as transmitter power, distance from the transmitter, antenna efficiency, and seawater properties (salinity, temperature, density,...). Ref. 24D-3. The following ranges and depths were achieved consistently with "Goliath" and standard German U-boat loop antennas and receivers, based on extensive measurements with 200 U-boats:


Fig. 72: Reception depth for "Goliath" signals in different seas and oceans

(source: ref. 263D2, p. 247 in ref. 24A3, ref. 24A17; slightly different depth ranges are listed in ref. 24A4)

Note that at even lower radio frequencies such as 0.1 kHz (i.e., in the ELF range), depths of 300 m (1000 ft) can be reached.

German submarines that operated in the above parts of the world were equipped with a dedicated LF/VLF receiver, notably the Telefunken Langwellen/ngstwellen Peilüberlagerungsempfänger ( = LF/VLF direction-finding radio with BFO) model T 3 P L Lä 38 from 1938, and an associated loop antenna, steerable with a hand wheel. It covered the frequencies of 15-33 kHz and 70-1200 kHz. Ref. 24B-2, 24B-3.


Fig. 73: the Telefunken "T 3 PL Lä 38" VLF receiver (far right) in a U-boat radio room

(source: Fig. 283 in ref. 24A12)

Below are parts of some radio documents from the German submarine U-505, from November 1943, January and February of 1944. These paper strips reference transmission times and frequencies of Goliath. U-505 was captured intact by the US Navy off the Atlantic coast of northwest Africa in June of 1944. It is on display at the Chicago Museum of Science and Industry.


Fig. 74: radio documents from the German submarine U-505, with "Goliath" frequencies & transmission times

(source: ref. 24B-1; US gov't - no ©)

Note that most other high-power LF/VLF transmitters of that era still were enormous machine-generators. I.e., the continuous carrier frequency was generated electro-mechanically, without radio tubes. Most notably is the Alexanderson alternator, dating back to the early 1900s. Ref. 24A10, 24A11. The only surviving Alexanderson transmitter is located at Grimeton (near Varberg, in Alexanderson's home country Sweden). It is still operated twice a year (on Alexanderson's Day and at Christmas) on 17.2 kHz, with the callsign SAQ. The UK also operated powerful transmitters, but not in the VLF/LF frequency range; e.g., a 600 kW medium wave transmitter for jamming and propaganda broadcast purposes (ref. 24A13, 24A14).

The telegraphy speed of Goliath's Hellschreiber communication is unknown. As a reference: today's US Navy VLF/LF (14-60 kHz) installations use a 50 Bd transmission speed. Above 45 kHz, Goliath was suitable for low-quality voice/phone transmissions. This is quite adequate for transmission of Hell-pulses at 2.5 chars/sec (122.5 Bd = Feld-Hell), and probably even for 5 chars/sec ("Presse Hell"). For Hellschreiber transmissions, the modulator of Goliath transmitter was in the same configuration as used for AM voice/phone transmissions. That is: Hellschreiber tone pulses were used, rather than on-off-keying of Goliath in CW mode. Between 30 and 45 kHz, the bandwidth of the Goliath system was insufficient for voice communication, but usable for Hellschreiber. Available original documentation does not indicate whether "Feld Hell" was used, or "Presse Hell". That said, Goliath broadcast communication with submerged submarines was obviously only uni-directional, as it was not exactly practical to equip submarines with a 1 Gigawatt transmitter and an enormous antenna system. That is: with "Presse Hell", the submarines would only have needed a small "Presse Hell" printer. In general, it is not clear which type of Hell system the German submarines were equipped with. Obviously, the U-boats did not have the equivalent of a Goliath system on board, and could not respond to Goliath transmissions while submerged. So, for Goliath's Hellcasts, the U-boats only needed a Hell printer, not a Hell keyboard- or punch-tape sender.

The Goliath antenna and transmitter installations were located just outside the town of Calbe-an-der-Milde (Calbe on the river Milde), about 135 km (≈85 mi) west of Berlin, and ca. 65 km (≈40 mi) north of Magdeburg. In 1952, Calbe was renamed to "Kalbe", to avoid confusion with the town of Calbe-an-der-Saale (Calbe on the river Saale), ca. 30 km south of Magdeburg. The location was primarily selected because of the properties of the local soil being unusually conducive to VLF propagation. Construction of Goliath took 27 months, and was completed during the spring of 1943. Allegedly, construction of the installation (terrain, buildings, antennas, etc.) may have cost as much as 15 million Reichsmark, about a third of which for the antenna system (ref. 24A1). Based on general inflation rates, this would have been equivalent to about 79 million US$ and 72 million Euro in 2016 (ref. 178C).

The transmitter was developed and constructed by C. Lorenz A.G. of Berlin-Tempelhof. Lorenz became part of the American company International Telephone and Telegraph (I.T.T.) in 1930. In 1948, the name was changed to Standard Elektrik Lorenz (SEL). Goliath was never the target of Allied bombing raids - very likely because the Allies enjoyed eavesdropping on the (encrypted) messages of the Kriegsmarine.

Goliath was remote-controlled from what today would be called the C3 (command, control, communication) center of the Kriegsmarine. This center, code name "Koralle", was located just north of Bernau, some 20 km northeast of Berlin. Ref. 24C-1/2/3. The Oberkommando der Kriegsmarine (OKM, Supreme Command of the Navy) - including the Befehlshaber der U-Boote (BdU) Grand-Admiral Karl Dönitz - had been moved here in January of 1943, due to the increasing risk of bombing raids on Berlin. The location of the (fully destroyed) C3 bunker at "Koralle" is marked on this map (Dönitz's villa is still there). Ref. 24C3. Goliath was linked to "Koralle" (145 km away, ≈90 mi) via the communication network of the Wehrmacht. The Reichspost had put the required phone lines and transmitter-keying equipment in place in 1942. Note that tuning of the transmitter and antennas was not remote-controlled. Goliath was hooked up to the public electrical power network ("Fernleitungsnetz"), with diesel generator backup (2100 HP, 1800 kVA, 380 V, 3-phase; ref. 24A1). Goliath had the BdU callsigns ÄDA and DÄP, as did the BdU transmitters at Nauen (ref. 24B-2).


Hein Lehmann logo

Hein Lehmann logo

The 15-60 kHz operating frequency range of Goliath is equivalent to a wavelength range of 5-20 km (≈3-12 mi). This implies very large antennas. The Goliath "antenna farm" comprised three top-loaded monopole antennas (TLMAs), spaced 800 m (½ mi). They are sometimes referred to as a new variation on the 1920s Alexanderson-antenna (ref. 24D2). The standard Alexanderson configuration with a straight line of T-antennas (as installed at, e.g., Nauen and Grimeton) had been found to be much too inefficient (only 10%) at the desired operating frequencies.

The monopole antennas of Goliath were 204 m tall (≈670 ft), about 2/3 the height of the Eiffel tower. Each of these antennas was a zinc-plated steel tube-mast ("Stahlrohrmast") with a diameter of 1.7 m (≈6 ft). The base of each tube-mast was insulated from ground with two large porcelain insulators, each with a large metal collar. This provided 300 kV isolation even during rain. This approach was patented (ref. 24D-7) by Hein, Lehman & Co., Eisenkonstruktionen, Brücken- und Signalbau of Berlin-Reinickendorf, incorporated in 1888 (sheet metal, steel constructions, bridges, railway signals, hangars for "Zeppelin" dirigibles). Ref. 24D4. This company had a department ("Abt. Funkbau") that constructed and installed (very) large antenna masts and towers ("Funkmaste", "Funktürme"), primarily for Telefunken. E.g., the Funkturm (radio tower) in Berlin-Charlottenburg (1926), the antennas for the Langwellensender at Lahti/Finland (1928), at Nauen/Germany, Kootwijk/The Netherlands, and Sidney/Australia.


Fig. 75: porcelain-insulator base of one the "Goliath" tube-masts

(source: ref. 24A1; similar: ref. 263D2)

The Goliath antenna radiator of 204 m is quite large compared to human scale, but extremely small (≈1%) with respect to the wavelength of Goliath transmissions (5-20 km!). This gives the antenna a large capacitive reactance at the feed point. To counteract this, and increase antenna efficiency, the antennas were equipped with an enormous top-loading "hat" ("Dachkapazität") at the top, and a very extensive ground system. Each radiator had a hexagonal "hat" comprising six sets of six radial wires. The radial wires of the Goliath "hats" were aluminium cables (2.5 cm ( = 1 inch) diameter), strengthened with a steel cable at the core. Combined length of the radials was about 50 km (≈31 mi). These wires look like the ribs of an umbrella. Hence this type of antenna is also called an umbrella-antenna ("Schirmantenne").

Umbrella antenna cartoon

Fig. 76: a real umbrella antenna!

(source: Radiobote, Vol. 5, Nr. 27, May-June 2010, p. 20)

Each of the the antenna radiators had a variable tuning coil. These vertically installed coils were enormous variometers. They comprised a fixed coil with a diameter of 3.5 m (≈11½ft). A slightly smaller coil (3.2 m diameter) could be inserted hydraulically into this stationary, with a precision of 0.1 mm! The coils were 5 m tall (16 ft) and weighed about 5000 kg (11k lbs). The winding of the fixed coil was made of 7x50 mm2 Litz wire (equivalent to a single diameter of 11 cm (≈4.4")) whereas the movable coil had 42 turns of 7x50 mm2 Litz wire. The main tuning coil, similarly massive, was housed in the transmitter building. A frequency change was a two-man job, and took about 5 minutes. The building with the tuning coils was fully screened with aluminium sheet metal. The losses induced by Eddy currents amounted to 50 kW (much more than coil lossses!). An automatic ventilation system was used to remove the heat. Ref. 263D2.


Fig. 77: side and bottom of an antenna tuning coil (one for each of the tube masts)

(source: ref. 263D2, ref. 24A2)

To support the radials of the top-loading "hat", there were six truss-masts (lattice masts, "Gittermast") for each of the three radiator masts. By sharing support masts, their total number was reduced from 18 to 15. The truss-masts stood 170 m (558 ft) tall, and had a triangular cross-section with sides of 3 m (≈10 ft). These masts were grounded and had no RF function. The radials were also insulated from these masts. All tube- and truss-masts were stayed with guy wires at three heights and in three directions. This type of antenna was later also used for VLF long-distance radio navigation systems such as OMEGA and LORAN-C.

The antenna system included an extensive of system of buried ground radials. There were four sections of 204 radials each. According to the Lorenz company, the total length of the radials was at least 350 km (≈220 mi; ref. 45). Other sources mention as much as 465 km (according to the construction supervisor, architect R. Breither, the latter may have included the feed lines; ref. 24A1). The radials were made of zinc-plated steel strips (20 cm x 2 mm and 30 cm x 2 mm), at a depth of 30-40 cm. At this point in the war, copper had become scarce. Solder joints were zinc-plated with a mobile galvanizing unit. To increase the effectiveness of the ground radials, the soil was kept moist. There were ditches and a dozen ponds that served as water reservoirs for irrigation. Ref. 45.

The complete antenna system had a very (!) impressive efficiency: 47% on15 kHz, and as much as 90% on 60 kHz! Ref. 263D2.


Fig. 78: diagrammatic top view of the three umbrella-antennas


Fig. 79: Left-to-right - "Antennenhaus" (22 m tall building) with tuning coils, tube-mast, and main buildings

(source: ref. 263D2, ref. 24A2; foreground: anchor of one of the guy wires of a tube-mast)


Fig. 80: Central transmitter buildings (antenna feed lines exiting the roof) with rail access; cooling tower on the far right

(source: ref. 263D2)


Fig. 81: view from a tube-mast, down to a truss-mast 34 m (≈100 ft) below; (right) base of one of the 15 truss-masts

(source: ref. 24A2)

The fenced-in area of the Goliath "antenna farm" had the shape of an equilateral triangle, with sides of about 2.4 km (≈1.5 miles). The surface area of 2.63 km2 (260 hectares) is equivalent to about 320 regulation soccer fields or 490 US football fields! The image sequence immediately below shows the terrain, the location of the three main masts, an overlay of the umbrella antennas, and some dimensions.

goliath site

Fig. 82: the "Goliath" site - overlaid with location of the antennas and the transmitter & control building

Goliath map

Fig. 83 satellite image of the "Goliath" site, with marked location of the 18 masts

A full-size interactive Google-map version of the above map is here (or click on the map image above). It has the same colored locations markers. In most cases, you can fully zoom-in the satellite image map, and may see the actual the remains of the structures. Click on any marker icon, to get the associated information. You can click-and-drag the map with your mouse, and zoom in & out with your mouse-wheel (or use the buttons in the bottom left-hand corner of the map). Note: you must have maps.googleapis.com enabled in your browser. Locations marked with markerare exact. Click on any marker icon to get the associated information. You can click-and-drag the map with your mouse, and zoom in & out with your mouse-wheel (or use the buttons in the top left-hand corner of the map). The position of the truss-masts is marked with yellow marker; their exact location cannot be determined in the satellite image, except for the one marked with .


The Goliath transmitter comprises a 4-stage modulator ("Steuersender") and a 3-stage power amplifier ("Hauptsender"). Ref. 263D2. Only Telefunken vacuum tubes were used. The modulator has three tubes: RL 12 T 15, RL 12 P 35, and RS 384. The modulator had an output of 500-600 W. It was controled by either a crystal oscillator with 12 selectable crystals, or a variable frequency LC oscillator, covering all freqeuncies (2 ranges). Temperature compensation and  calibration achived an frequency accuracy of 50 ppm. The first stage of the amplifier had two RS 217 tubes (of which one configured as a standby spare) had an output power of 5-10 kW.  The second stage had six tubes of type RS 250 (of which two as standby spares) for an output power of  60-90 kW. The final stage had six tubes of type RS 301 (ref. 24D1). The latter six were arranged as parallel push-pull pairs. Ref. 24A1. These tubes were water-cooled, stood 1.9 m tall (≈6.3 feet), and weighed about 90 kg (≈200 lbs). Ref. 24D5, 24D6. Cooling was provided with distilled & softened water, at a minimum flow of 48 m3 per hour (≈12 thousand US gallons/hr). Maximum capacity was over twice that (100 m3/h). Via heat-exchangers, the dissipated heat was transferred to a second cooling system (filled with plain tap water, not necessarily potable) with two cooling towers.

The first and second stage were Class-B push-pull amplifiers. The final stage was operated with Class-C anode modulation for CW transmissions, and with Class-B anode modulation for voice/phone and Hellschreiber tone pulses. Ref. 24A1, 24A2, 24A4. In CW mode, when the transmitter was not keyed "on", half of the six tubes in the final stage acted as dummy loads. This limted power fluctuations on the regional public power grid to "a mere" 500 kW. Otherwise lights in the region would blink in the rhythm of the Morse characters. The maximum output current of the transmitter was 2500 amps, which was equally distributed to the three antennas (700 amps each) and a central feed point (400 amps).


Fig. 84: the Telefunken RS 301 tube

(source: ref. 24D-1)

A single RS 301 cost 8400 Reichsmark (almost six times the annual salary of the average factory worker in 1937, see this page), making a six-pack as expensive as a "V2" missile. A complete set of tubes cost over 106 thousand Reichsmark (ref. 24D6).


Fig. 85: the final stage of the transmitter amplifier, with RS 301 tubes

(source: ref. 24A2)


Fig. 86: the transmitter and control room in the central building

(source: ref. 263D2, ref. 24A2)

Electrical power was provided by the three-phase 50 kV regional power grid, first reduced to 15 kV with local transformers. Two dozen water-cooled AEG mercury-vapor oxyde-cathode rectifier tubes of type S15/150i were used to rectify the AC power. Capacitors and coils were used to reduce ripple to 0.1°. Backup power was provided by an 1800 kVA AEG generator, powered by a 2110 hp diesel engine made by MAN AG (Maschinenfabrik Augsburg-Nürnberg). The company's lineage goes back as far as 1840 to several machinery construction companies in the cities of Augsburg and Nürnberg, and to several ironworks companies in the Ruhr area as far as 1758. Rudolf Diesel (yes, inventor of the Diesel engine that he patented early 1893), had a development contract with MAN at least until the early 1900s. There was a large supply of fuel (up to three weeks) for the main and backup generators (ref. 24A3).

Goliath was never the target of allied bombing raids (just like the U-boats that served as worldwide weather reporting stations, and most factories that belonged to US consortiums such as Ford and I.T.T.). Intercepted and decoded messages provided invaluable information about U-boat command and the location of U-boat packs. It was also used as a navigation landmark.

The table below list some other high-power transmitters that were used for transmissions to U-Boats:


Fig. 87: some other transmitters used by the Kriegsmarine for communication to U-boats (ca. 1943)

(source: ref. 24A12)


The US army reached the Goliath site on 11 April 1945. They used it as a prisoner-of-war (POW) camp (ref. 24A8, 24A10). Towards the end of May 1945, it was handed off to the British. Based on the Yalta Treaty, the area was in the Soviet-controlled zone, and the Soviets took over at the beginning of July 1945. The POW-camp was dissolved at the end of that same month. The Soviets had the Goliath installation repaired and tested. It was fully dismantled by April 1947 and shipped to Russia in over 3000 (!) rail wagons. The equipment sat in storage depots near Leningrad (renamed back to its original name St. Petersburg in 1991) for several years (ref. 24A16). By 1952, it was rebuilt near Druzhnyy, about 18 km south of Gorky (some 150 km east of Moscow, and renamed Nizhny Novgorod (= "Nizhny Newtown") in 1990). The Druzhnyy area presumably has similar soil conditions as at Calbe. It is still operated to this day (2016) by the Russian navy, who use it for communication with submarines (surprise!) and to transmit time signals (station RJH99).


Fig. 88: Goliath - rebuilt at Druzhnyy in Russia

(source: 24A2)

A satellite image of the current Goliath site is provided below.

Goliath map

Fig. 89: the current site of "Goliath" with marked location of the 18 masts

(click here (or on the map image) for a fully interactive Google map version of this map in a separate window)


During the latter half of the 1930s, the Swedish army evaluated the Feld-Hell ("Hellskrivapparat" or "Hellskrivare"), over wired connections and also in combination with the following transmitter-receiver stations (ref. 25D-25J):

  • 10 W Br m/39 ("10 watts bärbar radiostation m/39"), portable transceiver (2.5-5.0 MHz transmit, 1.3-6.1 MHz receive, CW/AM). Ref. 43.
  • 30 W Kr m/29 ("30 watts kärr-radiostation m/1929") mobile radio (1.5-3.0 MHz transmit, 0.3-3.0 MHz receive, A1/A2 modulation)
  • 100 W Ft m/38 ("100 watts fast radiostation m/38").

In June of 1939, the head of the Swedish army signed off on a purchase order for 16 Feld-Hell machines. Ref. 25N. During 1940-1942, an additional 220 machines were ordered, of which only 105 were delivered. Ref. 25P.

Per ref. 25A (p. 47), the Swedish army used the Feld-Hell with the following radio sets:

  • 75 W Tp m/43 (ref. 25B) with transmitter type 100 B made by "Standard Radiofabrik", a "mottagarlåda" receiver box with two receivers of type MKL 941 (ref. 25L) made by Svenska Radioaktiebolaget in Stockholm (SRA, 1919-1983, in 1983 Ericsson Radio Systems AB), two 6 volt DC 85 Ah batteries, a 1500 W 50 Hz power generator, and antenna material. The transmitter is directly keyed by the Feld-Hell character drum. This system remained in use (though without Hellschreiber) until the early 1970s!
  • 250 W Bl m/40 and 250 W T m/40 ("250 watts bilradiostation", ref. 25B). This is a 1.3-9.0 MHz radio truck. The transmitter was operated with Hell tone-pulses via the microphone input. Ref. 25H. Output power: 250/110/75 W (A1. A2, and A3 modulation, respectively). The receiver was, again, the MKL 941 ,.Antenna: 6m mast + 2.6 m rod.
  • 800 W Bl m/43 ("800 watts bilradiostation", ref. 17). This is a 2.3-9.0 MHz radio truck, with a receiver for 200 kHz - 10 MHz. In Hell-mode, the CW transmitter was operated via a keying device. Ref. 25B, 25C, 25J. Transmitter output power: 800 watt (A1), and 200 watt (A2/A3). The transmitter covered 2.3-9 MHz. The four receivers (all model MKL 940), covered 200-400 kHz plus 540 kHz - 10 MHz (ref. 25L).


Fig. 90: transmitter (left) and receivers of the "250 W Bl m/40" and "250 W Bl T m/40" mobile stations (radio trucks)

(source: ref. 25B)

The Feld-Hell entered service with the Royal Signal Regiment of the Swedish Army in 1942. Wired operation was over military communications networks and the public telephone system. Their Sats Tc 33 Feld-Hell set (initially army stock number ( = Mtlrnr) Tc 90240, later M3963-105211) came complete with two 12 volt DC / 85 Ah battery packs. An attenuator (Tc 21115) could be plugged into the Siemens keying-device (army stock nr. Tc 20033, later M3936-105219), to reduce the output signal to a level that was compatible with the phone system. Ref. 25D.

Commercial negotiations between Siemens and the Swedish Air Force about Feld-Hell machines and "Presse Hell" type office equipment (5 cps), date back to ca. 1941 (see pp. 119-120 in ref. 25C). Pricing information for the Hellschreibers of the Swedish army and air force and the Swiss army, is provided on the "Hell equipment prices 1937-52" page.


During World War 2, Finland was involved in two armed conflicts with the Soviet Union: the Winter War (November 1939 - March 1940), and the Continuation War (June 1941 - September 1944). During the Continuation War, the headquarters of the Finnish armed forces was located in the town of Mikkeli - 180 km northeast of Helsinki. The headquarters were located in the buildings of the Central Elementary School, whereas the Communications Center was located in a cave in the nearby Naisvuori hill. The Center's codename was "Lokki" ( = seagull). Both sites are now a museum (here and here). The Communications Center maintained a Hellschreiber link with the the German forces in the town of Rovaniemi, 670 km to the north of Helsinki, in Finnish Lapland. Rovaniemi was headquarters of the Wehrmacht in Finland, December 1940 - December 1944. Ref. 26A, 26B, 2. Rovaniemi became one of the nodes on the 4500 km long German wired teleprinter / telephone network from Rastenburg (Kętrzyn) in Poland, to Berlin and Hamburg, via Denmark, Oslo and Narvik in Norway, Petsamo, Rovaniemi and Helsinki in Finland, Reval in Estonia, to Riga in Latvia. Ref. 26C.


Fig. 91: one of ca. 50-150 Feldfernschreiber operators of the women's' auxiliary services in Finland, 1941-1944

(source: courtesy T. Ekko, used with permission)

The first ten Feld-Hell machines entered service with the Finnish Defense Forces at the beginning of 1941. Many more were bought after that. Hellschreiber communication was primarily conducted over telephone lines, though the Finnish navy also used Feld-Hell in combination with the VRJP radio set. The Finnish Defense Forces used Feld-Hell until the early 1970s. Ref. 26D.

The four-digit equipment designator "VRJP" stands for: V = Viestintälaite (communications equipment), R = Radio, J = ???, P = the manufacturer (here: Philips) or country of manufacture. The VRJP set is either a DR 38 A or an FR 38 A transceiver. Both were made by the N.V. Philips' Gloeilampenfabrieken company in The Netherlands. Or rather, they were designed and made by Nederlandsche Seintoestellen Fabriek (NSF, "Dutch Telegraphy Equipment Factory") in Hilversum/The Netherlands. This company was founded in 1918, as a joint venture of Philips (40%), Marconi U.K. (40%), and Nederlandsche Telegraaf-Maatschappij Radio-Holland ("Radio Holland" for short, 20%). The latter was founded in 1916 by several major Dutch shipowners (ref. 283, p. 46) and the Bataafsche Petroleum Maatschappij (a subsidiary of the Royal Dutch Shell oil company). Philips became the majority shareholder of NSF in 1925 by acquiring the Radio-Holland shares, and bought out Marconi in 1946. Initially, NSF produced transmitters for the Dutch Navy, Air Force, national public radio broadcast, and overseas territories. In 1947 it was renamed N.V. Philips' Telecommunicatie Industrie (PTI; p. 225 in ref. 283C).


Fig. 92: logo of the NSF company in The Netherlands

The DR 38 A and FR 38 A are small VHF (66 - 75 MHz) transceivers, and are basically the same, other than the power supply. The Draagbare Radio ( = portable radio) 38 A (DR 38 A) was used in mobile stations (radio trucks, cars); it had a 6 Volt battery and two DC-DC "Zerhacker" vibrator/chopper-converters to generate the anode and grid voltages. The FR 38 A was for fixed-base stations; it had a 110-240 VAC transformer-rectifier power supply. The set measured 25x38x22 cm (HxWxD, ≈10x15x8½ inch). Its original function was that of a mobile phone. The transmitter operated on a single frequency, and had an output power of 3 - 5 Watt (A2/A3 modulation). The receiver covered the entire 66 - 75 MHz band. The "38" implies that the design entered into service in 1938. In 1939, the first production series of 200 units was delivered to local authorities in The Netherlands (fire departments, police, ambulance services, and the national Radio Monitoring Service (Radio Controle Dienst, RCD, of the Dutch PTT). The Ministry of Defense (MoD) requisitioned a number of these sets during the months leading up to WW2. The German occupation forces shipped the sets to Germany, where they were also used by the police (Berlin, starting 1940). Ref. 26F. It appears that these transceivers were also built by Philips UK.


Fig. 93: "Dr 38 A" set installed in a car

(source: ref. 26G)


Fig. 94: "FR 38 A" with its power supply and transceiver chassis

(source: www.cdvandt.org)


During WW2, the Royal Hungarian Army (RHA) used standard Feld-Hell machines, Siemens-Halske Feld Hell machines were also manufactured in occupied Hungary by the Telefongyár company ("Telephone Factory"), starting in 1939. In Hungary, these machines are referred to as "39 M" (Model 39), see ref. 27B-27C.


Fig. 95: Field telephone exchange unit of the Hungarian army, with "Klappenschrank" switch board and a Feld-Hell machine

(source: ref. 27A; Hungarian switchboard model 30-M with 30 lines, HIR = Honvéd (Homeland Defense Force) Infantry Regiment)


Fig. 96: German Feld-Hell machine (pre-1940 model) being used by a unit of the Hungarian Army

(source: collection of the Postal Museum in Budapest/Hungary)

Overall, the RHA used Hellschreibers from 1939 until 1958. The Magyar Államvasutak (MÁV, Hungarian State Railways) also used the Hellschreiber system, on long wavew frequencies, but initially with commercial "Presse Hell" printers.


Fig. 4: A post-WW2 HTG-1 Feld-Hell machine (removed from its carrying case) at the train station at Széchenyi Hill near Budapest

(source: ref. 27E; the radio in the background is a -SWiss-made Autophon E44 (= 1944 design), see the "Radios used with the HTG-1" section)



The Italian Royal Army (Regio Esercito, 1861-1946) also used Feld-Hell machines (ref. 29A/B), with legends in Italian:


Fig. 97: Feld-Hell machine with Italian legends and the standard 1-page Feld-Hell manual in Italian


Fig. 98: Feld-Hell machine of a mobile Signals unit of the Italian Army, being powered with a car battery

(source: forum of Collezionisti & Radio Operatori Stationi Ex Militari - CROSEM)

For instance, the 1943 document below states that the Engineer Corps of the Nr. II Army Corps had eight Siemens-Hell (Feld-Hell) teleprinters that are used over phone-lines, and that will subsequently be used over existing radio links, without the need for any additional equipment. I do not know with what type of radios the Italian Feld-Hells were used.


Fig. 99: mention of eight Feld-Hell machines of the 2nd Army's Engineer Corps

(source: eBay)


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: March 2016 unless noted otherwise.

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