Gesellschaft für elektroakustische und mechanische Apparate

Gesellschaft für elektroakustische und mechanische Apparate mbH (GEMA) (English: Society for Electroacoustic and Mechanical Devices) was a pioneering German defense electronics manufacturer based in Berlin. Founded in January 1934, the company became the primary birthplace of operational German radar and sonar technology. Heavily funded by the German Navy (Kriegsmarine), GEMA developed and supplied the world's first operational shipboard radar units (Seetakt) and the backbone of Germany's early warning air-defense radar network (Freya). The company expanded dynamically during World War II, growing to employ nearly 6,000 workers across multiple production sites before its permanent dissolution in 1945.

Foundations and early acoustic research (1932–1934)

The company originated from an acoustic and sound-recording enterprise called Tonographie GmbH, founded in Berlin in 1928 by electronics researcher Hans Erich Hollmann, technical expert Hans-Karl von Willisen (1906–1966), and manager Paul-Günther Erbslöh (1905–2002). By 1932, the studio began collaborating with Dr. Rudolf Kühnhold, the Chief Physicist of the Navy's Signals Research Institute (Nachrichtenmittelversuchsanstalt, or NVA) in Kiel. Kühnhold was investigating improved methods for the underwater acoustic detection of ships via hydrophones, which formed the basis of early German active sonar research.

Concurrently, Kühnhold recognized that measuring the distance to targets with optical precision required the use of electromagnetic radio waves. After major commercial electrical conglomerates, including Telefunken, rejected his radical theories on radio reflections, Kühnhold turned to von Willisen and Erbslöh. Operating initially out of their sound studio, the team built a continuous-wave (CW) transmitter operating on a 50 cm wavelength (600 MHz) with a split-anode magnetron tube purchased from Philips. In June 1934, they successfully detected a large steamer ship in the Kiel harbor via Doppler-beat interference at a distance of 2 km.

Because the research was highly speculative and entirely outside the scope of their commercial acoustic business, Erbslöh and von Willisen formally incorporated **GEMA** on January 16, 1934, with a capital of 20,000 Reichsmarks. The new firm was initially headquartered at Potsdamerstraße 122 before moving to Gaußstraße 2 in Berlin-Oberschöneweide.

Development of pulsed radar (1935–1939)

While early continuous-wave tests successfully proved that electromagnetic waves bounced off metallic hulls and passing aircraft, the continuous signal bled directly into the receiver, preventing accurate distance (range) calculations. Kühnhold shifted GEMA's focus to a pulse-modulated architecture.

Under the technical direction of Dr. Theodor Schultes and consultant Hans Erich Hollmann, GEMA integrated a pulse generator modulating 2-microsecond bursts at a pulse repetition frequency of 2000 Hz. Crucially, they integrated a **Braun tube (cathode-ray tube)** to visually display the time delay of returning signals, allowing direct range readings.

In May 1935, GEMA tested this new pulsed unit at Pelzerhaken in the Lübecker Bay. Reconfigured into a super-regenerative receiver paired with a mattress-style array of dipole antennas, the system successfully tracked the naval research vessel Welle (the former state yacht Grille) at ranges up to 8 km. This breakthrough culminated in a formal demonstration to the Commander-in-Chief of the Kriegsmarine on September 26, 1935, showcasing a range tolerance of just 50 meters and a directional accuracy of 0.1 degrees achieved via lobe switching. Impressed, the Naval High Command issued GEMA lucrative production contracts, code-naming the technology Funkmesstechnik (radio-measuring technology).

To handle industrial scale-up, GEMA outgrew its Oberschöneweide facilities. In September 1937, the company purchased a massive, 36,000-square-meter vacant linoleum factory from Linolwerke AG at 154–158 Wendenschloßstraße in Berlin-Köpenick, completely relocating its operations there by 1938.

From these foundations, GEMA branched its designs based on branch-specific military requirements:

• The Kriegsmarine required shorter wavelengths to track smaller surface targets amidst sea clutter, leading to the 80 cm wavelength **Seetakt** system (FuMG 38G), first operationally deployed aboard the pocket battleship Admiral Graf Spee in 1936.
• The Luftwaffe required maximum early-warning range to detect incoming aircraft, resulting in the longer-wavelength (1.8 to 2.0 meters) **Freya** system (FuMG 39).

Wartime operations, decentralization, and the Wahlstatt complex (1939–1945)

Following the outbreak of World War II, GEMA shifted entirely to a massive wartime production footing. On December 18, 1939, a GEMA-designed Freya station achieved a major early-warning milestone by enabling the interception of RAF bombers in the Battle of the Heligoland Bight.

As Allied strategic bombing targeted Berlin later in the war, GEMA decentralized its operations to shield its manufacturing pipelines. The workforce ballooned to nearly 6,000 employees distributed across satellite manufacturing facilities in Jüterbog, Luckenwalde, Woltersdorf, and Wahlstatt in Lower Silesia.

The Wahlstatt factory complex

The factory established in Wahlstatt operated as a highly sensitive, clandestine facility designated for the continuous development and fabrication of radar systems. The industrial complex was set up inside a historic 18th-century Benedictine Abbey dedicated to Saint Hedwig of Silesia. From July 1940 to 1942, the abbey grounds had been utilized as Oflag VIII-F, a high-security prisoner-of-war camp holding Allied (principally French and Belgian) officers.

When the primary POW camp was officially deactivated, [...] authorities retained a select cadre of prisoners on site to perform manual construction labor, retrofitting and adapting the ancient abbey architecture into automated high-frequency assembly floors for GEMA. Following the site's industrial conversion, the factory utilized forced labor units drafted from surrounding regional detention sites. Notably, a significant portion of this specialized workforce consisted of civilian families from Luxembourg who had been forcibly deported by [...] authorities and interred at the nearby Lager 112 in Schlauphof. Inmates worked under strict military oversight to wire complex, high-frequency vacuum tubes and assemble early modular tracking components.

During this late-war period, GEMA engineered the massive **Mammut** (FuMG 415) early-warning installation. Operating with a giant, fixed mattress antenna frame, the Mammut is historically recognized as the world's first operational **phased array** radar network.

Dissolution and post-war legacy

In the closing months of the war, GEMA evacuated its core laboratories and remaining inventory to Schleswig-Holstein to escape the advancing Red Army. Following Germany's unconditional surrender in May 1945, British occupation authorities moved to secure the enterprise. On May 16 and 17, 1945, British military engineers accidentally detonated GEMA's primary experimental testing arrays in Schleswig-Holstein during a clearing operation—much to the intense frustration of British intelligence services, who had intended to exploit the intact technology. However, Allied intelligence successfully confiscated thousands of technical blueprints, patents, and manufacturing schematics.

Under Allied Control Council directives banning German military asset ownership, GEMA was legally liquidated. The heavily damaged main factory complex on Wendenschloßstraße in Berlin-Köpenick fell within the Soviet occupation zone. The site was subsequently nationalized by the East German government, evolving in 1949 into the prominent state-owned enterprise **VEB Funkwerk Köpenick**, which became a leading producer of civilian maritime electronics and broadcasting instrumentation in the GDR.

Key Technological Products

• Seetakt (FuMG 38G / FuMO 22): The world's first operational naval surface-search radar network, operating on an 81.5 cm wavelength (368 MHz).
• Freya (FuMG 39): Early warning air-defense radar operating at 1.8 to 2.0 meters (120–130 MHz), capable of detecting bomber-sized targets at ranges up to 160 km.
• Mammut (FuMG 415): A massive, long-range warning radar utilizing a fixed antenna array; the world's first operational phased array radar system.
• Wassermann (FuMG 402): A heavy, long-range early warning radar consisting of a rotatable structural tower up to 60 meters tall, built upon a vertical array of Freya antennas.
• Erstling (FuG 25a): One of the earliest operational airborne Identification friend or foe (IFF) transponder systems, which responded to interrogating signals from ground-based Freya units.

Notable Personnel

• Paul-Günther Erbslöh & Hans-Karl von Willisen: Corporate founders, technical directors, and managing partners.
• Dr. Rudolf Kühnhold: Scientific director at the NVA whose initial Navy contracts drove the foundation of GEMA.
• Hans Erich Hollmann: Core co-founder of the initial *Tonographie* studio and major technical consultant on ultra-short-wave tube propagation.
• Dr. Theodor Schultes: Chief of GEMA's High-Frequency Laboratory and principal development engineer behind the *Freya* and *Seetakt* systems.
• Dr. Walter Brandt: Chief of the Low-Frequency Laboratory, driving the firm's parallel underwater acoustic and sonar technologies.
• Heinz von Foerster: Noted Austrian-American physicist who conducted high-frequency plasma research inside GEMA's labs during World War II, later gaining fame as a pioneer of cybernetics.

See also

• Radar in World War II
• Würzburg radar (Developed concurrently by corporate competitor Telefunken)
• Oflag VIII-F (The military prison complex integrated into the Wahlstatt works)