Finnish (Swedish) WW-II spy radio set
The Kyynel M10 and M11 were compact spy radio transceivers, developed
and built by the Finnish Army Depot Company Munkkiniemi near Helsinki
(Finland) during WW-II. Despite the fact that Finland was collaborating
with Germany, they built the M-10X (a crystal version of the set)
for the Swedish Army, where it was known as Radio Station 1 W Br m/44.
It is also known as VRHAG.
The radio set was the successor to earlier Kyynel models and was
basically a combination of the earlier M-5 transmitter
and the M-7 receiver. It produced a maximum output power of 1W
(in practice 0.3-0.5W) and was
intended for long range intelligence and guerrilla patrols .
The M-10 measure only 5.5 x 12 x 24 cm and weights 1.6kg.
It was usually mounted on top of a
cardboard battery box (see below).
When not in use, it was stored in a
cardboard container, together with the
passport. The image on the right shows the M-10X (crystal).
The Kyynel M-10 was introduced in 1942 and is also known as VRHAG.
A later version of the radio, the Kyynel M-11 was produced well into the 1950s.
The M-10 is basically identical to the M-10, with the exception of the filament
voltage (LT) that was 3V rather than 1.5V. Like the M-10X, the M-11X was the
crystal version of the set. The M-11 was also known as VRHAI
Both radios were designed for a long distance communication range between
150 and 500km.
All controls and most of the connections are at the front panel. The crystal
is inserted in a socket on the side of the unit. The batteries are connected
to the contact strip on the right hand side.
A morse key can be connected at the front left and a suitable pair of
headphones at the far right.
A suitable antenna, consisting of two 20 meter wires, should be connected
to the socket at the top left. The antenna wires can be adjusted to four
different lengths, depending on the frequency in use. A tuning chart,
containing the desired antenna length and the correct setting of the antenna
tuning dial, was supplied with the radio.
The manual explains how to
set up the antenna.
Kyynel is the Finnish word for tear. It was used as the codename
for a long range of spy radio sets. Development of the range started before the
winter war of 1939, when the Army recognised the increased need for light-weight
Until that time, all Finnish radio sets used by the Army had been heavy and bulky.
They were unsuitable for remote patrol liaison officers .
As radio amateurs already had valuable experience with radio communication under
varying conditions, the development team consisted mainly of radio hams. The
group worked under supervision of reserve-captain Holger Jalander and the initial
designs were largely based on existing German agent radio sets weighting
15kg. These developments were not very successful.
An additional problem was that suitable components and tools were difficult to
obtain at the time. Nevertheless, the team succeeded in producing a small
portable radio station and the first prototypes were tested at the beginning
of 1940. In the early days, construction work on the radios was carried out
in the utmost secrecy in a heavily guarded cottage at Lake Tuusula.
The enterprise was later moved to a better location in Röykkää and finally
to Nystad .
Already in the early stages of the development Jalander decided to use
die-cast aluminium enclosures for the radios. Not only did he save on
weight this way, it also allowed the radios to become water-tight.
The developments eventually resulted in the production of the early Kyynel
models M-4, M-5 and TÖPÖ (stump) which
used German valves
(e.g. produced by Telefunken).
In 1942, the earlier models were followed by the M-10 which was effectively
a combination of the M-5 transmitter
and the M-7 receiver. The radio set was designated VRHAG (P-12-24)
and the first wiring diagram was drawn on 13 July 1942.
A few years later, a crystal version of the radio had to be developed,
but it appeared to be very difficult to obtain crystals at the height of
WW-II. Again, radio amateurs came to the rescue when reserve-lieutenant
Toivo Leiviskä, an electronics engineer, demonstrated how they could
be made manually . This resulted in the M-10X.
The crystal-driven M-10X was not only used in Finland, but was
also sold to Sweden in late 1943 and early 1944. The first 25 units
were delivered before Operation Stella Polaris in Finland, followed
by another 75 units that were produced by Major Lautkari in his workshop
The necessary components for this production run had to be shipped
over water from Nystad .
The M-10 was manufactured by Army Depot Company Munkkiniemi from late
1942 onwards .
It is housed in a die-cast aluminium case - an idea of Holger Jalander -
that can easily be opened by releasing eight hex-bolts at the edges
of the control panel and lifting out the interior.
The image on the right shows the interior of the M-10X. The radio is well
built, with the three valves of the receiver
(2 x DF11 and DDD1) mounted next to each other.
The transmitter valve (DLL21)
is located at the other end.
The radio is powered by two voltages: 1.5V for the filaments (LT) and 120V
for the rest of the circuitry (HT). The 120V voltage was supplied by a large
rectangular HT battery and the 1.5V was supplied by two large cylindrical
batteries. All three batteries were located in a
cardboard case that
was bolted to the bottom of the radio set.
The batteries were connected to the black contact strip at the right side
of the radio by means of four wires.
The instruction manual
shows how the batteries were installed.
Early versions of the radio were stored in a
cardboard carrying case,
which was later replaced by a metal container.
When not in use. the M-10 was usually stored in a cardboard container with
reinforced corners. The container had a canvas carrying strap on one of its
sides and a removable lid at the top. The lid was held in place by two clip locks.
Later versions of the M-10 (and M-11) were stored in a more robust metal
container, allowing the radio to be stored for extended periods of time in
a moisty place.
A morse key can be connected to a two-pin socket at the bottom left of
the front panel. The key is connected in series with the anode of the
DLL 21 transmitter valve and directly switches the 120V supply
to the transmitter on and off.
The image on the right shows the small morse key that came
standard with the M-10X. Please note that the cover needs to be present
when operating the Kyynel M-10, as the key directly switches the HT voltage.
The Kyynel M-10X was supplied with a pair of 600 ohm high-impedant
speakers, mounted to a canvas strap that allows them to be worn on
the head. The headphones are connected to the 2-pin socket on the right
of the front panel.
The image on the right shows the original headphones that were supplied
with the Kyynel M-10X featured on this page.
The antenna basically consists of two wires of 20 meters each. Depending on
the frequency in use, the wires can be adjusted at four different lengths.
When not in used, each wire is stored on a spool that is stored with the radio
in the storage container.
The manual gives clear instructions on how to setup
and use the antenna. With aid of a separate
rope and two throwing weights, the
wires are effectively used as a dipole.
The X-version of the Kyynel M-10 (i.e. the M-10X) can be operated with a
standard crystal of the era, operating at the fundemental frequency or the
3rd overtone. The crystal is inserted in an extra socket on one of the side
The problem with a standard crystal however, is that the radio doesn't fit
the storage container whilst the crystal is inserted into the socket. For this
reason, an adapted crystal shape (Kide in Finnish) was produced
by T.I. Leiviskö. It is shown in the image on the right.
Crypto Museum is
currently looking for this type of crystal.
A small booklet with clear instructions on how to set up a working radio
station, was supplied with the M-10. The image on the right shows the booklet
that came with the Swedish version of the M-10X.
It contains a checklist, examples for setting up the antenna and
instructions on how to tune and operate the transceiver.
The rightmost page in the image shows how the LT and HT batteries are
connected to the radio. Click to enlarge.
Each M-10 radio came with a small maintenance booklet
- the passport -
that contained simple instructions
and allowed modifications and other
changes to be logged in a table.
It also allowed radio traffic to be logged (journal).
The image on the right shows the first page of the passport, showing
the model and serial number of the radio and the number of the supplied crystal.
More images below.
We are currently looking for the following items for our Kyynel radio:
- Original 'low profile' crystal
- Frequency/antenna tuning table
- Storage container
- Kyynel M-10
- Morse key
- Tuning chart
- Operating instructions
- Passport (maintenance booklet)
- Antenna wires (2)
- Antenna rope
- Lead weight (2)
- Bag with spare components
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© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Monday, 01 October 2012 - 16:10 CET