Sorge
I may have been too quick to dismiss the possibility that Soviet spies built their own radios. Maybe they did, but with a radio specialist on the team. Thanks to Mikele 9A3XZ for alerting us to this case.
Here is a 1964 New York Times article on the Sorge case: https://www.nytimes.com/1964/10/11/archives/again-the-sorge-case.html?unlocked_article_code=1.M1E.mQv_.rxy03pIehUb4&smid=url-share
Here is some great info on the radios thay used:
The clandestine radio equipment used by Dr. Richard Sorge’s Soviet military intelligence (GRU) spy ring in Tokyo (1933–1941) was custom-built, field-assembled, and highly effective.
Because bringing specialized espionage hardware into imperial Japan was too risky, the ring's technical mastermind and radio operator, Max Clausen, manufactured and assembled the gear locally using commercially available components and household scrap.
Max Clausen
The technical breakdown of the "Ramsay" ring's radio setup includes:
1. The Homebrew Transmitter
Clausen built small, portable shortwave transmitters using the simplest possible circuitry to ensure reliability and easy concealment.
The Circuit Type: He heavily favored the Hartley oscillator circuit, a highly efficient and simplistic vacuum-tube configuration requiring very few parts.
- Power Source & Output: The transmitter generated roughly 15 watts of power. It ran on standard Japanese household AC electrical mains (100V), meaning they did not need bulky, suspicious external generators or specialized military batteries.
- Frequency Range: Transmission took place on amateur shortwave bands (around 7 MHz), which allowed the signal to blend in with legitimate civilian radio enthusiasts.
2. Disguise and Concealment
The entire unit was designed to look like "household junk" if discovered during a routine police sweep.
- Modular Assembly: The transmitter was not kept as a single, uniform device. Clausen kept individual parts (tubes, coils, capacitors) scattered around his house. He would only assemble the working radio immediately prior to a transmission window and dismantle it directly afterward.
- The Cabin Cruiser / Fishing Boat Trick: As Japanese counter-intelligence began realizing an illegal radio was transmitting out of Tokyo, the ring adapted. Sorge purchased a luxury cabin cruiser. Clausen would pack the transmitter onto the boat and sail into the open sea or disguise themselves as a fishing vessel to transmit, making it completely impossible for the Japanese authorities to pin down their location using shore-based radio direction-finding (RDF) equipment.
3. The Receiver
For receiving commands from Soviet intelligence handlers in Vladivostok, Clausen modified a standard, commercially available civilian radio receiver. By altering its internal coils, he expanded its frequency coverage to intercept shortwave military bands. It possessed exceptionally high sensitivity to pick up faint, distant signals from across the Sea of Japan.
4. Code and Operational Security
- One-Time Pads: Sorge's ring used a highly secure system of enciphering their Morse code messages based on numbers from a German statistical yearbook. Because the "key" changed with every single letter and was never reused, the Japanese intercept stations could read the signal but could not decrypt the messages.
- Radio Jargon Disguise: To further evade suspicion, Clausen heavily spiced his transmissions with casual "ham radio" lingo, making it seem like an amateur hobbyist chatting with someone abroad rather than a spy sending high-level military secrets.
Despite the primitive and makeshift nature of this equipment, Clausen successfully transmitted over 23,000 code phrases. This included Sorge's most critical intelligence coup: confirming that Japan would strike south toward the US/Pacific instead of invading Siberia, allowing Stalin to safely redeploy his massive Siberian divisions to save Moscow from the German advance.
The radio operations of Dr. Richard Sorge’s "Ramsay" spy ring in Tokyo are considered some of the most successful and technically fascinating in espionage history.
The technical setup, gear, and tactics behind Sorge's communications relied heavily on a specialized approach to clandestine radio:
🛠️ The Custom-Built Hardware
Unlike many World War II intelligence networks that used factory-issued, military-grade espionage transceivers, Sorge’s equipment was entirely custom-built and home-brewed from commercially available parts.
- The Builder: The equipment was designed, built, and maintained by Sorge’s highly skilled radio operator, Max Clausen (a German communist and Soviet GRU agent).
- The Rig: Clausen constructed compact, portable shortwave transmitters and highly sensitive receivers. He bought ordinary radio components—tubes, condensers, and coils—from commercial shops across Tokyo to avoid drawing attention.
- Size and Capability: The transmitter had to be small enough to easily hide and transport, yet powerful enough to consistently project a signal from Tokyo all the way to a Soviet receiving station in Vladivostok.
📡 Counter-Surveillance & Transmission Tactics
The Japanese Tokko (Special Higher Police) and military counterintelligence knew an illegal radio transmitter was operating in Tokyo, but Clausen successfully evaded their radio direction-finding (RDF) vans for six straight years. They managed this through strict transmission discipline:
- Constantly Moving Locations: Clausen never transmitted from the same place twice in a row. He regularly moved the equipment between various safe houses in Tokyo.
- The Cabin Cruiser: Sorge purchased a luxury cabin cruiser boat. Clausen would sometimes install the transmitter on the boat and broadcast from the open sea, completely confounding land-based Japanese tracking units.
- Brief Airtime: Transmissions were brief, highly condensed, and conducted late at night to minimize the window for the Japanese to lock onto their signal.
🔐 The Encryption: Book Cipher & One-Time Pads
Even if the Japanese intercepted the radio waves, they could not read the content for years because of the ring's manual encryption system.
- The Statistical Almanac: Sorge's ring used a manual book cipher utilizing the Statistisches Reichsamt (German Statistical Almanac).
- The Process: Clausen would take the page numbers, columns, and figures of the almanac to serve as a random text key (or text gamma) to convert Sorge's intelligence into long strings of numbers.
- The Advantage: Because it was a "manual cipher," it required absolutely no mechanical cipher machines (like the German Enigma), eliminating bulky, incriminating hardware.
🛑 The Downfall
The radio operation ultimately collapsed not because the Japanese intercepted the signal or broke the code technically, but through human counterintelligence work. In October 1941, Japanese police arrested an associate of the ring, leading a trail back to Sorge and Clausen.
Upon Clausen's arrest, the Japanese authorities finally seized the hidden radio components. They were reportedly astonished at how Clausen had engineered such a high-performing, long-range shortwave system using nothing but simple, over-the-counter radio parts.
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