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OSS
CIA
SBO
  
SSTR-1
WWII clandestine spy radio set - this page is a stub

SSTR-1, 1 also known as TR1, 2 was a modular valve-based clandestine transmitter/receiver set, also known as a spy radio set, developed in 1942 for the US Office of Stratic Services (OSS) — the forerunner of the CIA. During World War II (WWII), the set was used extensively by OSS agents operating on occupied (European) territory, by resistance organisations throughout Europe and in the China-Burma-India theatre [1]. It is the American equivalent of the British Type 3 Mark II (B2).

The set consists of a transmitter, receiver, power supply unit (PSU) and a collection of spare parts, each housed in a metal enclosure and covered by a removable lid. It was usually supplied in a fibre board transit case, but was often used outside the case and in varying configurations. Some users operated it from within a travel suitcase.

The image on the right shows the dark green fibre board transit case with the various modules in upright position, ready for use. Although the set is often shown like this in museums, the lid cannot be closed as the receiver is too high. 3
  

Prior to the US entering WWII, the OSS had a very basic radio set for clandestine operations. It had the advantage that it could be powered from both AC and DC mains networks, but had otherwise a number of design deficiencies. This prompted the OSS to come up with an improved design [2].

The task was given to Major Henry Shore, who was a former employee of the Radio Corporation of America (RCA). Shore wanted RCA to be involved with the project, but the company was too busy with other wartime projects for the US Government. It was then agreed that RCA employee Earl Anderson would work on it in his own time, using the existing AC/DC radio as a starting point.

The first version of the SSTR-1 was released in 1942, its name being a combination of the model number of the transmitter (SST-1) and the receiver (SSR-1). The prefix 'SS' is the abbreviation of 'Strategic Services' (OSS). Throughout the war, the design was updated several times, resulting in the addition of a letter-suffix to the model. 4 After the war, the SSTR-1 remained in use by the newly established CIA until at least 1953, despite the fact that new clandestine radio sets like the RS-1 and RS-6 had meanwhile become available [2]. The SSTR-1 was also used as a temporary solution by several European Stay-Behind Organisations (SBOs) in the early days of the Cold War — for example in The Netherlands and in Belgium — until it was replaced by newer radio sets.

  1. SSTR-1 is the abbreviation of Strategic Services Transmitter Receiver No. 1
  2. The SSTR-1 was known also as TR1, for example by the Dutch post-war Stay-Behind Organisation O&I. In that case, 'TR' is the abbreviation of Transmitter Receiver.
  3. The receiver has to be placed on its side before the lid of the transit case can be closed.
  4. Receiver model numbers from SSR-1-A to SSR-1-G have been observed, whilst transmitter model numbers range from SST-1-A to SST-1-E.  More

Fibre board transit case
Febire board transit case with SSTR-1 spy radio set
SSTR-1 in green fibre board transit case
Receiver, transmitter and power supply unit
SSTR-1 front view
Headphones
Morse key
Crystals for the SSTR-1
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Fibre board transit case
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Febire board transit case with SSTR-1 spy radio set
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SSTR-1 in green fibre board transit case
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Receiver, transmitter and power supply unit
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SSTR-1 front view
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Headphones
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Morse key
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Crystals for the SSTR-1

Features
The image below gives an overview of the contents of the SSTR-1 transit case. At the far left is the SSR-1 receiver, which is higher than the other modules. It is powered by the SST-1 trans­mitter to its right. The transmitter is in turn powered by the largest module: the SSP-1 power supply unit (PSU). The PSU is powered by a 6V DC source, or directly from the AC mains. The remaining space – at the far right – is taken by the accessories and a range of spare parts.


The headphones should be connected at the top left of the receiver. When transmitting, the operator can use the internal morse key – located at the front edge – or the supplied external key, which can be connected to the jack socket to the left of the internal key. The transmitter produ­ces ~ 15 Watts. Note that in the setup shown above, it is difficult to operate the internal morse key, as it is just below the edge of the fibre board transit case. This indicates that the set was not intended for operation from within the transit case, but had to be removed from it for proper use.

The PSU has three functions. It can act as a:

  1. Mains PSU
    For powering the device from the mains (90-230V AC)
  2. Inverter
    For powering the device from a 6V DC car battery
  3. Charger
    To charge a 6V battery from the AC mains
Known usage
Ton van Schendel
A special example of the SSTR-1 is shown in the image below [3]. It is of WWII vintage and was owned by Dutch resistance fighter Ton van Schendel. During the war, he worked for the Dutch radio monitoring service, the RCD, and simultaneously — covertly — for the Ordedienst (OD). 1

From the start of WWII until his arrest by the Germans in February 1943, van Schendel was the chief marconist of the OD. He trained many clandestine radio operators 2 and occasionally operated a clandestine station himself, in particular for communication with England.

The OD mainly used radio sets provided by the British SIS and SOE, such as the Mark V and Mark VII (Parasets), the Type 3 Mark II (B2) and the Type A Mark III (A3). When these were in short supply however, radios from American origin were supplied instead, such as this SSTR-1.
  

The image above shows the SSTR-1 transmitter (SST-1) and receiver (SSR-1) that were in posses­sion of Ton van Schendel some time after WWII. It was used by the OD during the war and/or by the Dutch Stay-Behind Organisation O&I in the early days of the Cold War. As far as we know, these are the only surviving parts of van Schendel's radio set. It is unknown whether the original PSU was lost, or whether it was never provided. It is possible that the set had been supplied without the original PSU and that an alternative PSU – made locally by the OD – was used instead.

 More about Ton van Schendel
 More about the Ordedienst (OD)

  1. During WWII, the Ordedienst (Order Service) was one of three major resistance organisations in The Netherlands. It provided intelligence to the British MI6 and to the Dutch Government in exile in London. Its task was to act as a law enforcement service immediately after the liberation of The Netherlands.  More
  2. Radio operators were also known as marconists.

Stay-Behind organisations
After WWII – at the beginning of the Cold War – the SSTR-1 remained in use until at least 1953, despite the fact that newer CIA spy radio sets, like the RS-1 and RS-6, had meanwhile become available. In the early days of their existence, some European Stay-Behind Organisations (SBOs) used left­overs from WWII as a gap-fill solution until newer sets became available to them. The stay-behind use of the SSTR-1 is confirmed for the following countries:

 More about stay-behind organisations


Parts
Fibre board transit case
Receiver `SSR-1
RX
Transmitter SST-1
TX
Power supply unit `SSP-1
PSU
Headphones
Morse key
Quartz crystals
Wire antenna
Container with spare parts and accessories
Operating instructions
Transit case
in most cases, the SSTR-1 was supplied in a dark green fibre board transit case, such as the one shown in the image on the right. It contains the receiver, transmitter, PSU and all accessories and spare parts. The lid is held in place by 8 spring loaded clips, and has a rubber gasket to make it water resistant. Note that this is not a suitcase.

The radio set has to be removed from the case before operation. In some cases, the complete set was placed inside a regular travel suitcase.

  

Receiver   SSR-1
The receiver is the leftmost module in the transit case. It is higher than the other module and has to be placed on its side before closing the lid of the transit case. When in transit, the controls of the receiver can be covered by a metal lid.

There were at least four versions of the receiver, each with a different frequency range and speci­fi­cations. The one shown here is an SSR-1-G, which covers 2.4 to 16.3 MHz, divided over two ranges which can be tuned freely.

  

Transmitter   SST-1
The transmitter is placed to the right of the receiver. It is crystal-controlled and is suitable for the transmission of CW signals (morse) only. When in transit, it can be covered by a metal lid.

There are at least two versions of the trans­mit­ter, with slightly different specification. The one shown here is an SST-1-E. It covers 3 to 15 MHz and has an output power between 8 and 15 W.

  

Power supply unit   SSP-1
The PSU is the heaviest module and is placed to the right of the transmitter. When in transit, it can be covered by a metal lid that also holds 2 spare fuses. The PSU allows the radio set to be powered from virtually any AC mains network in the world between 90 and 230 V.

The PSU can also be used as a power inverter, in which case a 6V DC source can be used to power the radio set. In addition, the PSU can be used as a battery charger, allowing a 6V battery to be charged from the AC mains.

  

Headphones
The SSTR-1 was supplied with the headphones shown in the image on the right. It is connected to the SSR-1 receiver by means of a 6 mm jack.   

Morse key
The transmitter is suitable for CW (morse) transmissions only, and can be oprated with the internal morse key located at the font edge.

The tranmitter can also be used with an external morse key, which must be connected to the 6 mm jack sockeet to the left of the internal morse key. The morse key shown in the image on the right was supplied with the set featured here.

  

Quartz crystals
The transmitter is crystal operated. The crystal socket, at the centre of the transmitter, accepts a wide range of crystal shapes, such as the small FT-243 shape and the larger US and UK crystals with a pin distance of 19 mm.

 Crystal shapes

  

Wire antenna
In most cases, the SSTR-1 was supplied with a wire antenna, consisting of two long pieces of electric wire. An additional (short) piece of wire was used to connect the radio set to ground.

In some cases, alternative antennas were used, such as the roll-up mesh antenna shown in the image on the right. Ideally, each wire should be a ¼λ long, but longer wires can easily be tuned for maximum RF output.

  

Spare parts
To allow the SSTR-1 to be repaired in the field, it was supplied with a range of spare parts, such as spare valves, fuses, vibrator, egg isolators, light bulbs, tools, etc., some of which are shown in the image on the right.

 List of spare parts

  

Operating instructions
Operating instruction and technical descriptions were provided in the form of the small A5-size booklet shown in the image on the right. It contains many photographs of the exterior and interior of the modules, along with clear descriptions on their use.

 Read the manual

  

Fibre board transit case
Febire board transit case with SSTR-1 spy radio set
Transmitter covered with lid
Transmitter with lid removed
Crystals for the SSTR-1
Crystal installed on the transmitter
Large crystal installed on the transmitter
Receiver covered with lid
Receiver with lid removed
Controls and volume adjustment
Runing knob and scales
Band selector
PSU
Note on the body of the PSU
Controls and meter on the PSU
Headphones
Headphones
Morse key
Morse key
Rollup antenna
Spares
Spares, morse key, etc.
Accessories and spares
Vibrator pack
SSTR-1 operating instructions
Page from the SSTR-1 instruction booklet
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Fibre board transit case
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Febire board transit case with SSTR-1 spy radio set
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Transmitter covered with lid
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Transmitter with lid removed
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Crystals for the SSTR-1
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Crystal installed on the transmitter
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Large crystal installed on the transmitter
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Receiver covered with lid
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Receiver with lid removed
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Controls and volume adjustment
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Runing knob and scales
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Band selector
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PSU
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Note on the body of the PSU
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Controls and meter on the PSU
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Headphones
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Headphones
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Morse key
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Morse key
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Rollup antenna
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Spares
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Spares, morse key, etc.
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Accessories and spares
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Vibrator pack
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SSTR-1 operating instructions
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Page from the SSTR-1 instruction booklet

Connections
Valves
  • 6J5
  • 6K8
  • 6SC7
  • 6SG7
  • 6SA7
  • 6SQ7
  • 6SN7
  • 6L6
  • 7V7
  • 7J7
  • 7F7
  • 7Z4
Specifications
  • Device
    Clandestine suitcase radio set
  • Purpose
    Agent communication
  • Model
    SSTR-1
  • Year
    1942
  • Country
    USA
  • Organisation
    Office of Strategic Services (OSS)
  • Development
    OSS employees,
    Radio Development & Research Corporation,
    Pioneer Electric and Research (Forest Park, IL, USA)
  • Manufacturer
    Radio Development & Research Corporation (transmitter),
    P.R. Mallory Co. (PSU),
    Finch Telecommunications (Passaic, NJ, USA)
  • Users
    OSS, agents, resistance, CIA, stay-behind
  • Receiver
    SSR-1-A, D, E or G (see below)
  • Transmitter
    SST-1-A or E (see below)
  • PSU
    SSP-1-C, SSP-1-D, SSP-2, SSP-3 or SSP-4 (see below)
  • Generator
    Hand-crank power generator GN-35 or GN-44
Receiver   SSR-1-A
  • Model
    SSR-1-A
  • Frequency
    2.8 - 16.6 MHZ
  • Bands
    3 (2.8-5.1 MHz, 4.5-9.1 MHz, 8.3-16.6 MHz)
  • Circuits
    RF stage, Oscillator/Mixer, Detector/AF, AF amplifier
  • Modulation
    AM R/T, CW
  • Valves
    6J5, 6K8, 6SC7 (2x)
  • Dimensions
    241 x 102 x 76 mm
  • Weight
    2300 grams
Receiver   SSR-1-D
  • Model
    SSR-1-D
  • Frequency
    2.9 - 16 MHZ
  • Bands
    2 (2.9-6.6 MHz, 6.6-16 MHz)
  • Circuits
    RF stage, Oscillator/Mixer, IF stage, Detector/AF, BFO
  • IF
    2 MHz
  • Modulation
    AM R/T, CW
  • Valves
    7V7 (3x), 7J7, 7F7
  • Dimensions
    241 x 102 x 76 mm
  • Weight
    2300 grams
Receiver   SSR-1-E
  • Model
    SSR-1-E
  • Frequency
    2.7 - 17 MHZ
  • Bands
    2 (2.7-6.6 MHz, 6.5-17 MHz)
  • Circuits
    RF stage, Oscillator/Mixer, IF stage, Detector, BFO/AF
  • IF
    455 kHz
  • Modulation
    AM R/T, CW
  • Valves
    6SG7 (2x), 6SA7, 6SQ7, 6SN7
  • Dimensions
    241 x 102 x 76 mm
  • Weight
    2300 grams
Receiver   SSR-1-G
  • Model
    SSR-1-G
  • Frequency
    2.4 - 16.3 MHZ
  • Bands
    2 (2.4-6.3 MHz, 6.2-16.3 MHz)
  • Circuits
    RF stage, Oscillator/Mixer, IF stage, Detector/AF, BFO
  • IF
    2 MHz
  • Modulation
    AM R/T, CW
  • Valves
    7V7 (3x), 7J7, 7F7
  • Dimensions
    241 x 102 x 76 mm
  • Weight
    2300 grams
Transmitter   SST-1-A
  • Model
    SST-1A
  • Frequency
    3-14 MHz
  • Bands
    3 (3-5 MHz, 5-8 MHz, 8-14 MHz)
  • Output
    8 - 15 W
  • Circuits
    Crystal oscillator/PA
  • Valve
    6L6
Transmitter   SST-1-E
  • Model
    SST-1A
  • Frequency
    3-15 MHz
  • Bands
    3 (3-7 MHz, 6-12 MHz, 8-15 MHz)
  • Output
    8 - 15 W
  • Circuits
    Crystal oscillator/PA
  • Valve
    6L6
  • Dimensions
    240 x 102 7.6 mm
  • Weight
    1800 grams
Power supply unit   SSP-1-D
  • Mains
    90, 110, 125, 150, 200, 230 V AC (40-60 Hz)
  • Battery
    6V DC
  • Valve
    7Z4
  • Dimensions
    241 x 152 x 89 mm
  • Weight
    4500 grams
Spares
  • 2 × Antenna wire
  • 4 × Antenna insulators
  • Coupling plug (for German wall outlet)
  • Coupling plug (for French Domestic wall outlet)
  • Solder
  • Bypass condensers
  • Filter condensers
  • Vacuum tube 6L6
  • Pilot light
  • Ground clamp
  • Alligator clip
  • Spare fuses
  • Screw driver
  • Knife
  • Vibrator unit
  • Neon bulb
  • Crystal socket adapter
  • Vacuum tubes 3 × 7V7, 1 × 7Q7, 1 × 7F7
Documentation
  1. Description and Operating Instructions SSTR-1
    Receiver SSR-1-G, transmitter SST-1-E, power supply SSP0-1-D.
    Publisher and date unknown. #CM303507.
References
  1. Louis Meulstee, Wireless for the Warrior, volume 4
    ISBN 0952063-36-0, September 2004.

  2. Peter McColum, The SSTR-1 "Suitcase Radio"
    Retrieved May 2021.

  3. Cor Moerman, SSTR-1 radio set of Ton van Schendel - THANKS !
    Donated November 2020.
Further information
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Crypto Museum. Created: Friday 21 May 2021. Last changed: Tuesday, 16 July 2024 - 13:46 CET.
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