British WW-II clandestine radio
Type 3 Mk. II, commonly known as the B2, is arguably the most
well known spy radio set
used during WWII. It was designed in 1942
by (then) Captain
British WW-II clandestine radio
Type 3 Mk. II, commonly known as the B2, is arguably the most
well known spy radio set
used during WWII. It was designed in 1942
by (then) Captain John Brown at SOE
Station IX, and manufactured
by the Radio Communication Department of the
SOE at Stonebridge Park.
The set was issued to agents and resistance groups and special forces
operating on occupied territory.
The official designator is Type 3 Mk.II but the radio is also known as
Type B Mk.II,
The B2 came in two flavours. The initial version came in an unobtrusive
leather suitcase that allowed an agent to travel inconspicuously.
This is the most well-known variant.
Later in the war it was dropped by parachute in
two water-tight containers,
that were more suitable for use by resistance groups operating in the field.
The image on the right shows the Type 3 Mk.II in its
original brown/red leather suitcase,
which can easily be recognized as it has three locks at
the front: two simple locks at the sides, and one that can be locked
with a key at the center.
The radio set consists of three units: a receiver (RX),
a transmitter (TX)
and a Power Supply Unit (PSU),
plus a box with spares and accessories. When
mounted in the suitcase, the transmitter is located at the center top, with
the receiver mounted below it. The PSU is at the right in such a position
that the two other units can be connected to it.
The spares box is generally positioned at the left, with the Morse key
mounted on its lid. When operating the B2, the lid of the spares box should
be placed on the table, so that the Morse key can be operated.
The Type 3 Mk.II (B2) was relatively small for its day and produced
an HF output power of 20 Watts.
Nevertheless, it was too big to carry around unobtrusively
especially when travelling by public transport.
For this reason, later radios, such as the
Model A Mk. III (A3) were made much smaller,
albeit with a limited frequency range (3.2-9.55 MHz) and reduced
power output (5 Watt).
The diagram below gives a clear view of the controls, as seen from the top.
The case has four compartments; one for each of the modules.
At the left is the spares box or accessory kit, here shown without its lid.
The spares box has two compartments: one for the spare valves and one for
the accessories. The PSU is at the right, with the AC and DC connections at
the right edge.
The two compartments at the center hold the transmitter (top) and receiver
(bottom), that both are connected to the PSU by means of a 6-pin plug.
The PSU can be powered from the AC mains or from a 6V DC source.
The headphones are connected to the socket marked PHONES L.R. at the front.
A suitable telegraph key should be connected to the socket marked KEY on
The transmitter further needs a crystal at the top right
and a tank coil at the left, just below the meter. The antenna and ground
should be connected to the two screw terminals at the top left of the
transmitter. A short green wire with a banana-plug
connects the antenna to the receiver.
The most well-known appearance of the B2 is the suitcase version, but
hardly any surviving B2 is found in its original red leather suitcase.
In fact, the B2 was delivered in a variety of different suitcases,
ranging from sturdy leather cases to simple cardboard and even wooden variants.
The original leather case is easily recognised,
as it has three locks
rather than the usual two. In many cases, the original case was swapped
for a more common two-lock version, as it was easily recognised by the enemy.
Later in the war, cheaper cardboard suitcases were used instead.
Louis Meulstee's excellent book Wireless for the Warrior, volume 4
 even shows an example of a wooden carpenter's toolbox in which a B2 is
The dimensions of the suitcase are pretty standard for the era.
The image on the right shows a B2 in a
simple cardboard suitcase.
Another reason for the many different types of cases is that, after the
war, many container versions (see below) were converted into
suitcase versions by collectors. Even today, collectors often move t