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Mk V   Paracette
British WWII spy radio set - wanted item

Mk. V, or Mark 5, was a clandestine radio, also known as a spy radio set, developed in 1941 by the Secret Intelligence Service (SIS, MI6) Section VIII at Whaddon Hall and Little Horwood (UK), for use by agents and resistance groups in occupied Europe. It was the first WWII spy radio dropped by parachute into occupied France in 1941. 1 The French nicknamed it Paraset or La Paracette. 2

The Mk V consists of a transmitter, receiver and power supply unit (PSU), mounted together in a wooden frame that measures 430 x 275 x 180 mm. It was commonly supplied in a suitcase and weights no less than 18 kg, which is one of the reasons why it was known as the Agent Killer [2].

Another reason was that the transmitter output was so strong, that it caused interference in nearby broadcast receivers. In addition, a later version had a simplified receiver that could be detected from some distance. It made the Mk V an easy target for the German direction finders.

The set was used by the SIS (MI6) as well as by the Special Operations Executive (SOE), and also by agents of the Free France intelligence service BCRAM (later: BCRA). It was the main agent's set during 1941 and most of 1942. Although there was also a Mk VI (Mark 6) – of which at least four variants existed – its main successor was the Mk VII (Mark 7), introduced in late 1942. Incidently, the Mk VII is also known as Paraset [3], 2 but that might be a post-war historical misinterpretation.
  
Image taken from WWII German Police handbook and processed by Pat Hawker [10] Click to zoom in

The Mk V transmitter covers a frequency range of 2.9-18 MHz, which includes the 20, 40 and 80 metre bands. It was available in a number of variants, such as in a wooden frame, in a suitcase and as three separate units [8]. Descriptions can be found in Louis Meulstee's book Wireless for the Warrior Volume 4 [8] and in Jean-Louis Perquin's book The Clandestine Operators [9].

The image above was taken from a German Police handbook from the early 1940s, that was distributed to field personnel, such as the Ornungspolizei (OrPo), the Sicherheitsdienst (SD) and the Gestapo, with the aim to recognise the clandestine radio sets of the enemy [10]. For the shorter range, the Mk V was succeeded in late 1942 by the much smaller but equally dangerous Mk VII (Paraset), and in 1943 by the much more secure medium-range three-piece Mk XV. 1

  1. It is often thought that the Mk XV was the first spy radio set that was dropped over France, but that was not the case. The Mk-numbers were issued sequentially and the Mk XV was not available until 1943 [2].
  2. Confusingly, the later British Mark VII spy set is also known as Paraset, but it is believed that this nickname is either incorrect or inherited from the Mark V.  Other Parasets

HELP PLEASE — Crypto Museum would like to add an MK V to its collection. If you have one available, or if you know of one that might be available, please contact us. In addition, we would like to hear from you if you have any additional information or documentation about this radio set.
Image taken from WWII German Police handbook and processed by Pat Hawker [10]
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Image taken from WWII German Police handbook and processed by Pat Hawker [10]

Known users
The Agent Killer
An article by Dave Gordon-Smith in Electric Radio Magazine of September 2018, reveals that the Mk V was nicknamed The Agent Killer by the SIS [2]. There were several reasons for this:

  • Weight
    The early suitcase sets were so heavy – reportedly 18 kg – that it was very difficult to carry them around inconspicuously. As a result, agents were quickly spotted and caught.

  • Powerful transmitter
    In addition, the suitcase version of the Mk V had a powerful output stage, based on an 832 valve, that produced an output power of 20-25 Watts and caused interference in nearby broadcast receivers, especially in urban areas.

  • Leaking receiver
    A later version of the Mk V had a receiver that was built with two 6SK7 valves, rather than three as in the suitcase version. As the RF pre-amplifier was missing in this version, the oscillator signal from the regenerative detector could leak to the antenna, and could be detected from some distance by means of Radio Direction Finding (RDF). One of the successors of the Mk V – the Mk VII (Paraset) – suffers from the same problem.
Operating instructions
During WWII, the Paraset was supplied to a number of agents and resistance groups in occupied European countries like France, Belgium, Norway and The Netherlands. From surviving accounts it is known that these devices were usually supplied with simplified operating instructions, but to our knownledge none of these documents appear to have survived the war. Until now that is...

In March 2021, Dutch amateur radio operator Bas Levering (PE4BAS) published two barely readable paper sheets – titled: Instructions for working a Paracette – which he had discovered in the legacy of Dirk Rustema, obtained in 2019 [7].

During WWII, Rustema – amateur callsign PA0DR – was a clandestine radio operator of the Orde­dienst (OD) — one of three important resistance organisations in The Netherlands. The Paraset was amoung the first radio sets used by the OD, and had been smuggled into the country via the Swedish route: by boat to Delfzijl (Netherlands).
  
Documents from the legacy of WWII radio operator Dirk Rustema, as obtained by Bas Levering [7].

The operating instructions for the Paraset came on two very thin folio paper sheets – presumably carbon copies (CC) – that were folded and stapled together. Apart from these instructions, the operator also needed a secret code for encrypting and decrypting messages. It consisted of the title of a poem (or song) and a 5-digit number to mask the position of the selected key words.

Part of the original Paraset instructions, as kept by Dirk Rustema and published by Bas Levering in 2021 [7].

Rustema probably retained the instructions that came with his Paraset, and rediscovered them years later, by which time much of the text had faded [A]. It prompted him to retype the text verbatim on his company's stationary, and save it for the future [B]. Unfortunately how­ever, he skipped the paragraphs that had meanwhile become unreadable. In May 2021, Crypto Museum obtained high-quality scans of the document from Bas Levering [7]. Using digital enhancement, we were able to reconstruct most of the text and make a nearly complete transcription [C].

 Download the reconstructed transcript

Handwritten notes on the original document [7]. Click to view the digitally enhanced version of the document.

Note that a few comments are handwritten at the top of the original document, probably at two different moments in time and possibly by two different people. First of all, the pencil-written marking S. 2441 in the top left corner. The same reference is written twice in the top right corner of the same page. It is currently unclear what it means, but there are several possibilities:

  1. The secret number for the poem code (see below)
  2. A production or delivery code with place/date, e.g. Sweden week 24 of 1941
  3. The serial number of the radio: S/N 2441
  4. An indicator or key for the so-called STP-code
  5. ...
The other comments are darker and are written in ink, probably in Dirk Rustema's handwriting. They might have been added at a later moment; most likely well after the war, as a reminder. "TLK de JCD" clearly refers to the call signs used for the station (JCD) and its counterpart (TLK). The handwritten text "Toen onze mop een mopje was" is the title of a famous Dutch poem that was used for several years during the war by the British Special Operations Executive (SOE) and the Dutch Ordedienst (OD) for exchanging encrypted messages. It is part of a poem code [10].

 Poem code used by the OD


About the authenticity of the document

After carefully studying the scans of the original document, there is no doubt at Crypto Museum that these are genuine instructions of British origin, that date back to WWII, probably 1941. Typeface and paper type are correct for the era. The language suggest that it was written by a native English speaker. The documents are hand-typeded carbon copies (CC), which means that typos (of which there are several) could not be corrected.

It was clearly supplied with a Paraset, which was probably at some point in the possession of Dirk Rustema, a Dutch amateur radio operator (PA0DR) who also acted as a clandestine radio operator for the Dutch resistance (OD) during the war. It is known that during the course of the war, several Parasets were supplied by SIS/SOE to the Dutch resistance via the so-called Swedish route: from the UK to Sweden and then by ship to The Netherlands, where they arrived in the harbour of Delfzijl, just 20 km east of Middelstum where Rustema lived.

It seems likely that the pencil-written marking 'S. 2441' was already on the document when Rustema received it, and might have been added by SIS/SOE when the device was assigned to Sweden. In that case it might be a date code: Sweden, week 24 of 1941. But it might also be a serial number, or something else altogether.

The handwritten text "Toen onze mop een mopje was", is in a different handwriting, and appears to be in ink. It is possible, if not likely, that this was added by Rustema after the war, as a reminder for the encryption method they had used at that stage. According to the post-war written account of chief marconist Ton van Schendel, the text — a famous Dutch poem — was used as part of a secret code by the SOE and the OD. That report also confirms the use of the Paraset by the OD and the involvement of Dirk Rustema in this context [9]. The first Paraset supplied to the Netherlands and used by Rustema, was known by the codename De Soto.

The marking "TLK de JCD" is somewhat mysterious. It is in a format that was (and still is) commonly used in radio communication. At the time, French was the common postal language and the word 'de' is French for 'from'. It is certain that TLK and JCD are callsigns, but it is currently unknown to whom they belonged. Also peculiar is the word Paracette in the title of the document. This name was given to the device by the SIS, who initially supplied the device to the French resistance, but later also deployed it in other countries [6].

Paul Reuvers & Marc Simons
Crypto Museum, March 2021
Paracette
When the document above surfaced in March 2021 [4], it was initially thought to describe the British Mk VII (Mark 7) — the spy radio set that is commonly referred to as the Paraset. But the instructions clearly indicate that a removable coil is fitted externally, which is not the case on the Mk VII. In addition, it is known that the radio set involved, arrived in The Netherlands during the course of 1941, at which point the Mk VII was not yet available. It was introduced in late 1942.

This is corroborated by Dave Gordon-Smith in an article in Electric Radio of September 2018, in which he demystifies the history of the British spy sets [2]. In his article – based on the personal account of Geoffrey Pidgeon [3] – Gordon-Smith confirms that the Mk V was nicknamed Paraset by the French, and that this name might have been passed on to the Mk VII later on, but that this is by no means certain. In any case, there is no historical evidence for the latter. It seems likely, that the nickname Paraset was given to the Mk VII by Pierre Lorain in 1972 when he published his book Secret Warfare [7], based on the limited information that was available at the time.

From surviving accounts – e.g. [3] – it is known that the SOE never adopted the Mk VII in practice. It is therefore much more likely, that the instructions above apply to the Mk V rather than to the Mk VII and that the Mk V should bare the nickname Paraset or La Paracette, and not the Mk VII.

 Other Parasets


Specifications
  • Year
    1941
  • Type
    Suitcase radio set
  • Purpose
    Agents, clandestine operations, resistance
  • Design
    SIS (MI6), Section VIII, Whaddon Hall/Little Horwood
  • Manufacturer
    SIS (MI6), Section VIII, Whaddon Hall/Little Horwood
  • Users
    SIS (MI6), SOE, BCRAM (BCRA)
  • Antenna
    30 m wire
  • Dimensions
    430 x 275 x 180 mm
  • Weight
    18 kg
Transmitter
  • Frequency
    2.9 - 18 MHz 1
  • Bands
    3 (plug-in coils): 80, 40 and 20 m
  • Modulation
    CW only
  • Output
    20-25W
  • Cicuits
    Oscillator, Power amplifier (PA)
  • Valves
    6V6 (or 6F6), 832
  1. Uses frequency doubling above 8 MHz.
Receiver
  • Type
    Regenerative detector
  • Frequency
    3.7 - 7.5 MHz and 7 - 16 MHz
  • Modulation
    AM, R/T, CW
  • Circuits
    RF, detector, AF amplifier
  • Output
    High-impedance headphones
  • Valves
    2 × 6SK7 (some unit 2 x 6SK7)
Power supply unit
  • Mains
    110-250V AC
  • Valves
    5Z3 (or 5T4)
Accessories
  • Headphones
  • Crystal(s)
  • Plug-in coils (3)
  • Spare valves
  • Antenna wire
  • Counterpoise wire (ground)
  • Earth spike
Known locations
  • CHRD, Lyon (France)
Connections
6V6 valve
The 6V6 is a beam-tetrode in a metal enclosure, developed in the mid-1930s by RCA for use in the audio stages of broadcast receivers. They are frequently found in single-ended or push-pull amplifiers, and even in today's vintage/retro valve-based amplifiers. Apart from the use in audio amplifiers, the 6V6 can also be found in the oscillator and PA stages of short-wave transmitters. In the Mk V, the 6V6 is used in the oscillator.

 6V6 datasheet

Pinout of the 6V6 as seen from the bottom of the valve

6SK7 valve
The 6SK7 is a remote-cutoff pentode in a metal enclosure, developed for use as high-gain radio frequency (RF) and intermediate frequency (IF) amplifiers in radio receivers. Because of its cutoff characteristic, it can handle high signal levels without cross modulation or distortion. It is also suitable for receivers with automatic gain control (AGC). In the Mk VI, the 6SK7 is used in both stages of the receiver: the regenerative detector and the audio frequency (AF) amplifier.

 6SK7 datasheet

Pinout of the 6SK7 as seen from the bottom of the valve

Documentation
  1. Instructions for working a Paracette
    Original (partly faded) instruction sheets. Date unknown, but assumed to have been supplied with a Paraset during WWII. Document kindly provided by Bas Levering [7].
     Digitally enhanced version

  2. Retyped (incomplete) transcript by the original owner
    Dirk Rustema. Date unknown, but assumed to be created several years after the war. Document kindly provided by Bas Levering [7].

  3. Reconstructed operating instructions
    Nearly complete transcription of the original instructions.
    Crypto Museum, May 2021.
References
  1. Louis Meulstee, Wireless for the Warrior, volume 4
    ISBN 0952063-36-0, September 2004.

  2. Dave Gordon-Smith (G3UUR), The Agent Killer, A Spy Set with a Bit of a Reputation
    Electric Radio Magazine #352, September 2018. pp. 2-15.
    Reproduced with kind permission of Electric Radio Magazine.

  3. Geoffrey Pidgeon, The Secret Wireless War
    ISBN 978-09560515-2-3. August 2008.

  4. Bas Levering, Instructions for working a Paracette
    Blogspot PE4BAS. 4 March 2021.

  5. A.S.M. van Schendel, Mijn werkzaamheden als chef-marconist van de OD en mijn belevenissen in de gevangenis
    Organisation of the Internal Radio Service (BR) of the OD and the radio links with the UK.
    Post-war report, in Dutch language. Date unknown.

  6. Poem code 'Toen onze mop een mopje was'
    Ton van Schendel. Undated.

  7. Pierre Lorain, Secret Warfare
    ISBN 0-85613-586-0. 1972.

  8. Louis Meulstee, Wireless for the Warrior, volume 4
    ISBN 0952063-36-0, September 2004.

  9. Jean-Louis Perquin, The Clandestine Radio Operators
    ISBN 978-2-35250-183-1, March 2021. p. 71.

  10. Pat Hawker (G3VA), Black & white image of Mk V in suitcase
    Scanned from a German Police handbook and processed by Pat Hawker.
    Early 1940s. Kindly provided by Dave Gordon-Smith [2].
Further information
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Crypto Museum. Last changed: Sunday, 21 November 2021 - 20:09 CET.
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