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← UK Cold War
The Mk.119 is highly modular and consists of three independant modules
(transmitter,
receiver
and power supply)
plus a case with spare parts.
The set was either supplied as three individual units in water-tight
containers (see below),
or as the wooden all-in-one unit shown on the right.
The version shown here is known as Mk. 119A and was probably built especially
for use by the British Army. At the front is a
hinged wooden lid.
When opened (as shown in the image), the lid acts as a writing desk
with a regular morse key
bolted in place in the rear right corner of the lid.
The three individual modules each have their own front panel and
are interconnected by external cables.
The upper unit is the transmitter. It has
a current meter in the top left corner.
At the center is the receiver with its wide 5-band scale drum.
The Power Supply Unit (PSU) at the bottom allows the
radio set to be powered from any AC mains source (110 or 220V) or 6V DC.
The remaining space at the right is taken by the spare parts compartment,
which contains spare valves, fuses, lamps cables, tools and other accessories.
A metal panel – labelled SPARES – keeps the items in place during transport.
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Although the boxed Mk. 119A was intended for use by the British Army, it was
also used by the SAS (Special Forces) and as a stand-by set for British
Embassies [2].
In the case of the SAS, it was often bolted onto a series 1 Landrover.
The unit shown here is a former Embassy standby set.
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- Mk. 119
Standard version of the Mk.119, in which each of the three basic modules
is housed in an individual watertight container. The cables and accessories
are stored in a 4th container.
- Mk.119A
In this version, all modules – including the accessories, spare parts and a
standard morse key –
are stored in a single wooden case. This version was used by the British Army.
- Mk.119B
Difference with Mk.119 currently unknown.
- Mk.119RT
Difference with Mk.119 currently unknown.
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The standard version of the Mk.119, as well as the Mk.119B and Mk.119RT,
consists of three individual modules, each of which is housed in a watertight
container. This version of the radio set was not intended for immediate
use, but was meant to be stored for a longer period of time.
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Each unit is housed in a similar (but differently sized) watertight aluminium
container, that can be closed with a watertight die-cast aluminium lid –
with rubber gasket – that is bolted at the four corners,
similar to the American RS-1 spy radio set.
This makes this version particularly useful for
Stay Behind Organisations (SBO).
The image on the right was taken from the manual
and shows the separate modules (after the aluminium lid has been removed)
plus the accessories. At the bottom left is the
Power Supply Unit (PSU) with the transmitter on top.
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The PSU containes a large transformer that is suitable for connection to
the 110 and 220V AC mains. It also containes a vibrator-unit, allowing the radio
station to be powered from a single 6V DC battery source.
The unit at the right is the receiver with its headphones on top.
All necessary interconnection cables are in front of the units.
The antennas are not shown in the image.
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Single-piece version
Mk.119A
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The image below shows the location of the various controls and connections
on the single-case Mk.119A. The radio set is shown here with the hinged front
lid open, demonstrating that the lid can be used as a writing desk, whilst
using the bolted-on morse key for sending messages.
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The complete set consists of three units, each of which is described in more
detail below. The full circuit diagram
is printed in the original user manual, which is available for download at
the bottom of this page [A].
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Because of its weight, the PSU is located at the bottom of the stack.
At the right is a 11-position rotary switch that allows the unit to be
used on five different AC mains voltages, ranging from 110V to 240V
(right half of the switch).
In the center position of the rotary switch, the unit is powered by an
external 6V DC source. In this position the transformer acts as a
power inverter and is used in combination with the built-in vibrator.
The transformer can also be used to charge the external 6V battery,
in which case the left half of the rotary switch is used.
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All connections to the outside world and to the other units are at the front.
In the unit shown here (Mk.119A) the receiver (REC) and transmitter (TRANS)
are permanently wired. Next to these two connections are mains socket
(AC MAINS) and the socket for the battery (6V BATT).
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The transmitter is mounted at the top of the Mk.119A.
It is crystal-based and can be used on all frequencies between 1.5 and 20 MHz,
divided over 6 ranges that are selectable with a rotary switch at the center.
The antenna is connected at the left, in parallel with the receiver.
A suitable crystal should be inserted into the socket at the bottom right,
next to the built-in morse key. An external key can be connected to the 6.3 mm
jack at the bottom center. In the Mk.119A (shown here) a fixed morse key is
connected in parallel to this socket.
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When transmitting, the meter is used in combination with the tuning knobs
(AE TUNING and DRIVE TUNING) to obtain maximum output power. A separate
7-position switch is available for selecting the desired coupling for
aerial loading.
The transmitter is powered by two voltages supplied by the PSU: 380V (92mA)
and 6.3V (1.5A) and produces a maximum output of 17W.
The circuit is built around two EF91 valves and a 2E26 power valve.
A small NE48 neon valve is used for tuning.
In the Mk.119RT, which is modified
for phone (voice) transmission, two more valves (EL70 and EF72) are used
for the modulator. The morse key is gone on that model.
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Contrary to the transmitter, the receiver is VFO-based. It is suitable
for all frequencies between 0.5 and 20 MHz, divided over 5 bands. The band
selector is at the bottom right and a wide drum-type scale is used for
tuning. On the drum, each of the five bands has its own scale. A small
window to the right of the drum, just above the tuning knob,
is available for fine-tuning.
The 6-valve superheterodyne receiver is designed for the reception of
telegrapy signals (CW), but is also capable of receiving phone, selectable
by a 2-position switch at the right.
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The circuit consists of an HF Amplifier (EF92), a mixer (EF91),
an oscillator (EF91), an IF amplifier (EF92), a second detector and AVC
(Germanium Crystal) and a BFO (EF91). The IF frequency is at 455kHz which
can be tuned ±2kHz by the BFO. According to the manual [A] the sensitivity
is 90µV in the 0.5-2.3MHz range and 20µV on frequencies between 2.3 and 20MHz.
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Spare parts and accessories
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Hidden behind a tall metal panel at the right of the Mk.119A are the spares.
This area is also used for storing the various cables and antennas when the
radio is not in use. With the other versions of the set, the spares are usually
stored in a separate water-tight container.
The image on the right shows some of the spares and cables as they were found
in the SPARES compartment of the Mk.119A featured on this page. The cable at
the top right is for connection to the mains.
A full list of all accessories is given below.
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- Spare valves (2) EF91
- Spare valves (2) EF92
- Spare valve (1) 2E26
- Vibrator SPC6
- Headphones
- Neon indicators
- Phone plug
- Fuses, 2 Amp
- Fuses, 250 mA
- Egg insulators
- Small screwdriver
- Insulated wire (2 mm)
- Small pliers
- E-screw Mains Adapter
- 2-pin Continental Plug
- Transmitting Key
- Supply lead (Power Pack to Transmitter)
- Supply lead (Power Pack to Receiver)
- Battery cable
- Main cable
- Aerial interconnecting leads
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- Varley Dry Accumulator, type 6.0/50H
- Crystals
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- Louis Meulstee, Wireless for the Warrior, volume 4
ISBN 0952063-36-0, September 2004.
- Personal correspondence with a former owner of the Mk.119A featured on this page
Crypto Museum #301633. 19 June 2002.
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© Crypto Museum. Created: Sunday 15 April 2012. Last changed: Monday, 14 September 2020 - 08:54 CET.
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