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Kyynel
  
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Kyynel M-5
Spy radio transmitter

M-5 is a compact valve-based clandestine transmitter, also known as a spy radio transmitter, developed shortly before World War II by radio amateur Holger Jalander 1 and manufactured by the Finnish Army Depot Company Munkkiniemi near Helsinki (Finland). Part of the Kyynel 2 family of devices it was introduced in 1940 as the successor to the Kyynel M-4. It was commonly used in conjunction with the Kynnel M-7 receiver, in which case the combination was known as VRHAC.

The M-5 is housed in a die-cast aluminium enclosure that measures 150 x 100 x 56 mm and weights 550 grams. It is watertight, so that it can be stored for a longer period of time in an underground cache or even under water. At the top are the controls and connections, hidden underneath three removable watertight caps.

The device is a single-valve (tube) free-running oscillator that operates between 3.5 and 6 MHz and produces an output power of 500 mW. The image on the right shows a typical M-5 unit in its watertight die-cast aluminium enclosure.
  
Kyynel M-5 transmitter with caps removed

The unit is powered by 1.5V DC (LT) and 120V DC (HT), either from a battery pack or an external power supply unit (PSU). Two reels with 21 m long wires were used as a symmetric antenna. The wires could be shorted to match higher frequencies. Also supplied was a miniature morse key. Some devices had a socket for connection of the receiver, allowing them to share the antenna. Based on surviving serial numbers, it is likely that no more than 100 units were manufactured. The design of the M-5 transmitter was later also used in the Kyynel M-10 and M-11 radio sets.

 History of the Kyynel radio sets

  1. In cooperation with other radio amateurs.  More
  2. Kyynel is the Finnish word for tear.

Kyynel M-5 with watertight caps in place
Laying flat
Bottom view
Straight-up front view
Kyynel M-5 transmitter with caps removed
Kyynel M5 in straight-up position
Front view
Kyynel M5 with morse key
A
×
A
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Kyynel M-5 with watertight caps in place
A
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Laying flat
A
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Bottom view
A
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Straight-up front view
A
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Kyynel M-5 transmitter with caps removed
A
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Kyynel M5 in straight-up position
A
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Front view
A
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Kyynel M5 with morse key

Features
The image below provides a quick overview of the controls and connections of the Kyynel M-5. The compartment at the centre holds the connections to the outside world, such as the power supply unit, the morse key and the antenna wires. It also holds a tuning aid, which consists of a push-button and a light bulb. When the button is depressed, the bulb acts as a tuning indicator.

Overview of the features of the Kyynel M-5.

The outer two compartments hold the power switch and the frequency dial respectively. The linear frequency scale is marked from 0 to 100, which – on the device shown here – corresponds to a frequency range from 3.38 to 5.53 MHz. With a properly tuned antenna, the device should provide an output power of approx. 500 mW. The power switch interrupts the 0V rail, which is the common rail for the 1.5V and 120V power supplies. The circuit is not connected to the chassis.

Removing the watertight cap
Top view
Connector compartment
Connector compartment
Tuning knob
Tuning the device (note the index line)
Receiver antenna socket
Morse key connected to the Kyynel M5
B
×
B
1 / 8
Removing the watertight cap
B
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Top view
B
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Connector compartment
B
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Connector compartment
B
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Tuning knob
B
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Tuning the device (note the index line)
B
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Receiver antenna socket
B
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Morse key connected to the Kyynel M5

Accessories
Morse key
Key
Power cable
Antenna wires
Tuning chart
Morse key
The Kyynel M5 was supplied with a miniature morse key, such as the one shown in the image on the right. It has a short cable that terminates in a bakelite plug with two 3 mm pins.

The morse key should be connected to the leftmost socket of the Kynnel M5.
  
Morse key

Battery power
The M5 was powered by external LT and HT batteries that should be connected to the 4-pin header in the middle compartment.

The power cable is currently missing.
  

Antenna
Two wires of 21 metres each were used as a dipole antenna. They were supplied on spools and could be configured for various lengths, depending on the selected wavelength.

The antenna wires are currently missing.
  

Tuning chart
Each Kyynel M5 came with an individual tuning chart that allows the user to convert the desired frequency or wavelength to the corresponding value on the linear schale of the tuning knob. The chart also specifies the optimum length of the antenna wires for each frequency range.

An original tuning chart is currently missing.
  

Morse key
Kyynel M5 with morse key
C
×
C
1 / 2
Morse key
C
2 / 2
Kyynel M5 with morse key

Circuit diagram
Below is the circuit diagram of the Kyynel M-5 as it has appeared in some publications, which is different from the one presented by Antero Tanninen in [2]. The circuit consists of a DLL21 (V1) double pentode that is configured as an oscillator. Note that the antenna output is symmetric and that the tuning button (S2) is connected in parallel with the lamp (La) and not in series as in [2].


Below is the actual circuit as it was taken down by Thomas Höppe (DJ5RE) in October 2021 from the Kyynel M-5 with serial number S519 [3]. The main difference is that the 0V line is switched (S1) rather than the +1.5V line. Furthermore, the 0V rail is not connected to the chassis (ground).

Circuit diagram of the Kyynel M-5 with S/N S519 as taken down by Thomas Höppe [3]

Circuit of the Kyynel M-5 with S/N S519

In addition, C2 has a value of 200pF (rather than 500pF) and an extra mica capacitor is connected in parallel to the 200pF tuning capacitor (C3), probably to alter the frequency range somewhat. In this configuration, the measured frequency range is from 3.38 MHz (scale set to 0) to 5.53 MHz (scale set to 100). Also note the extra antenna socket (Ar) to which the receiver can be connected. This 3 mm banana socket is located between the left and middle compartment at the front panel, but was not present on early devices. Later devices also had a ground socket for the receiver.


Click to see more

Interior
The Kyynel M-5 is housed in a die-cast aluminium enclosure that consists of two parts: the front panel and a case shell, separated by a rubber gasket and held together by four screws at the front panel. Three of these screws also hold the chains to which the watertight caps are mounted. After removing these four screws, the front panel can be lifted from the case shell. All components are mounted to the front panel, or to a vertical aluminium panel that is mounted to the front panel.

Kyynel M5 removed from its enclosure
Kyynel M5 interior
Interior
Interior
Interior seen from the rear
Interior seen from the front
Wiring and power switch
Tuned circuit
D
×
D
1 / 8
Kyynel M5 removed from its enclosure
D
2 / 8
Kyynel M5 interior
D
3 / 8
Interior
D
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Interior
D
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Interior seen from the rear
D
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Interior seen from the front
D
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Wiring and power switch
D
8 / 8
Tuned circuit

Connections
All connections of the transmitter are hidden under the middle cap. At the the left are two 3 mm sockets for connection of the morse key and two 4 mm banana sockets for connection of the antenna wires (A1, A2). At the centre are four 3 mm contact pins for connection of the (external) power sources. The second pin from the top is not used. At the right is the antenna tuning indicator, which is a regular light bulb. It is active as long as the tuning push-button is pressed.


At the front edge of the device, between the leftmost two compartments, is a 3 mm socket for connecting the receiver to the antenna of the transmitter. On some versions of the device, for example S/N S5100 [1], an extra 4 mm socket is available for connecting the receiver to ground.


Specifications
  • Device
    Clandestine transmitter
  • Model
    Kyynel M-5
  • Design
    Holger Jalander (and other radio amateurs)
  • Manufacturer
    Finnish Army Depot Company Munkkiniemi
  • Year
    1940/41
  • Purpose
    Intelligence and guerrilla patrols
  • Type
    Free-running push-pull oscillator
  • Valve
    DLL21
  • Frequency
    3.5 - 6 MHz (3.38 - 5.53 MHz) 1
  • Modulation
    CW
  • Output
    500 mW
  • Power
    +1.5V (LT), +120V (HT)
  • Current
    100 mA (LT), 15 mA (HT)
  • Antenna
    2 x 21 m wire (adjustable to 10 lengths)
  • Dimensions
    150 x 100 x 56 mm
  • Weight
    550 grams
  1. Measured from the device with serial number S519.
Accessories
Known serial numbers
The serial numbers all start with S5, which stands for Sändaren (transmitter) type 5, followed by a sequential number. Below is a list of all surviving units that are currently known [4][3]. If we assume that the first one (S/N 0) is a prototype, and that S/N 100 is the highest number found, it seems likely that around 100 units were manufactured. The serial number is engraved in one of the long edges of the front panel and in most cases also in the aluminium case shell. 1

  • S50
    War Museum (Finland)
  • S51
    Radio Museum Petäjävesi (Finland)
  • S519
    Crypto Museum (Netherlands)
  • S526
    Private collector
  • S535
    Private collector
  • S536
    Private collector
  • S543
    Unknown (featured in [1])
  • S551
    Private collector
  • S569
    War Museum (Finland)
  • S572
    Private collector
  • S575
    Private collector
  • S579
    War Museum (Finland)
  • S591
    Kouvola Military Radio Museum (Finland)
  • S598
    Private collector
  • S5100
    Private collector (featured in [1])
  1. Note that the prefix letter 'S' is not always present. Also note that on some devices the letter 'U' is imprinted in one of the short edges of the front panel. The meaning of the 'U' is currently unknown.
Serial number
Interior seen from the right side
E
×
E
1 / 2
Serial number
E
2 / 2
Interior seen from the right side

Missing
  • Original morse key
  • Tuning chart
  • Wire antennas
  • Operating instructions
References
  1. Louis Meulstee, Wireless for the Warrior, volume 4
    ISBN 0952063-36-0, September 2004.

  2. Antero Tanninen, Fjärrpatrullmännens radio 'Kyynel'
    Translated to Swedish and edited with permission of the author by Thomas ON6NT.
    Date unknown. Retrieved, September 2012.

  3. Thomas Höppe (DJ5RE), Personal correspondence
    October 2021.

  4. Thomas Anderssén (OH6NT), Personal correspondence with [3]
    October 2021.

  5. Thomas Anderssen (OH6NT), K62. Authentic key for the Finnish radio set 'Kyynel M5/M7'
    Visited 21 April 2022.

  6. Wikipedia (Finland), Kyynel (radio)
    Visited 21 April 2022.
Further information
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© Crypto Museum. Created: Monday 22 June 2020. Last changed: Tuesday, 17 May 2022 - 16:10 CET.
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