|
|
|
|
|
|
Japanese WWII miniature VHF transceiver
The 94-6 (94 Mark 6) was a miniature single-valve portable transceiver
that was used by the Japanese Army during WWII,
as part of a series of Army radios.
The name is derived from the Japanese year of development 2594 (1934),
with the Mk.6 version being the smallest model.
Althoug the radio was intended for the infantry, it was also used for various
'special' purposes.
|
The radio is extremely small for the era, and is suitable for voice
and morse
transmissions in the VHF band (25-45.5MHz), divided over
three frequency ranges.
It was intended for tactical (i.e. short-range)
communication, up to 2km.
Development of the radio began in 1934 and the first units were delivered
in 1935. Initially the radio was only suitable for a single band,
but a few years later (around 1937) the range was extended and
a three-position band selector was added.
According to the name plate, the radio shown here was manufactured in February
1943.
|
|
|
Japanese radios like the 94-6 are very rare. In WWII, during the heavy fights
at Guadalcanal, American Marines captured a number of them and immediately
put them to use for their own communication [1]. Apparently the radios worked
well, but were only suitable for short-range communication.
Immediately after WWII, the US ordered the destruction of all German and
Japanese war-time equipment, which is why so few of these beautiful
radios have survived.
|
- 24.7 - 34.1MHz
- 29.5 - 41.2MHz
- 35.0 - 50.5MHz
|
The 94-6 is one of the most compact radios of its era.
The entire unit
measures no more than 18 x 13 x 8 cm, and is normally packed inside a
high-quality leather bag,
from which it can be operated directly.
Even the morse-key at the side can be accessed directly
through the leather.
Most of the controls are located on the top surface,
just below the top lid of the case.
There are four adjustements and a meter. Once tuned
to the desired frequency, the top lid can be closed during the conversion.
The operational controls are all located on the side panel. The leather
case has been constructed in such a way that the operational switches
are always accessible.
On the side panel is a classic 3-position
lever-operated telephone keyswitch,
that is used as the power switch. In the center position, the radio is
turned off. In the upper position the transmitter is activated and the
lower position is for reception (RX).
Above the power switch is a 2-position switch that allows the microphone
circuit to be interrupted when the radio is used in CW mode.
The actual morse key is also on the side panel.
It has a large flat circular knob and can be accessed through
a thin flexible spot of the leather case.
The 94-6 was usually carried on the chest with the leather strap hanging
from the neck and the controls at the right.
The operator could then control the radio, and send
messages in morse, with his right hand.
|
|
|
|
|
|
|
The radio is very compact and is extremely well built. In some respects it
is even better built than German radios of the same era. The entire radio is
housed inside a rectangular metal box that is carried inside a leather bag.
The unit can easily be dismantled by opening the top lid and holding the
radio upside-down. The inner frame that holds all components will then
easily come out.
If it got stuck somehow, there is a hole at the bottom that allows you to
push the frame out.
|
The entire radio is built around a single
Japanese UM30MC valve (tube).
This is a double triode that performs more than one function and forms
the heart of a so-called Rushbox.
An excellent description of the circuit was published by Dick Rollema, PA0SE,
in March 1986 [3]. The article is available for download below.
The full circuit diagram
of the radio is stored inside the top lid.
As becomes clear from the images below, the unit is extremely compact,
making one wonder how the Japanese got all these large components
connected together inside such as small box.
|
|
|
The radio actually consists of a single aluminium frame that is open at
two sides. The top surface acts as the control panel and holds the adjustements,
the connections to the headphones and microphone, and the meter. The valve
(tube) can be accessed through a hole in the top surface.
|
Although the 94-6 was a very compact radio, power supply certainly was
a major issue in those days. For that reason, the 94-6 had two power sources:
a battery pack that was used for reception, and a hand-crank-operated
generator that was used to power the transmitter.
|
When receiving, power was supplied by a battery pack that was connected to
the left side of the radio. It contained batteries for 3V and 135V.
In transmission mode, the batteries would not be able to produce the required
current and a manually operated generator had to be used instead. The generator
was connected to the right side of the radio, where a socket is hidden
behind a small flap, just below the power switch.
The generator was capable of producing both 3V at 350mA and 135V at 30mA
simultaneously.
|
|
|
When both the batteries and the generator are connected, the lever-operated
power switch at the side of the radio (S2) automatically selects between the
two power sources when switching from RX to TX.
At the bottom of the generator are two flat metal hooks that slide outwards.
Each of the metal hooks have two rectangular openings
that are clearly indended for attaching it
to the belt. One side can be used for a left-handed operator and the other
one for a right-handed one.
We currently don't know whether the generator was operated
by the radio operator himself, or by an extra person walking next to him.
In either case, operating the generator must have been very inconvenient,
so conversations were presumably kept as short as possible.
|
|
|
|
|
|
|
The antenna should be connected to the
back of the 94-6, i.e. the side
that faces away from the operator when the radio is carried on the chest.
There are two sockets,
one for the antenna and one for that counterpoise,
that accept a special antenna plug.
The plug consists of a pertinax bridge with a thick messing pin
and a thin one, so that it can not be fitted the wrong way around.
|
The 94-6 radio was normally used with an L-shaped antenna,
consisting of a 1.4m horizontal boom that acted as the counterpoise
and a 65cm vertical rod that was the actual antenna.
The antenna sockets are accessible through
two holes in the leather case.
When the antenna plug is interted, it is held in place
by means of a small leather strap with a buckle.
The image on the right shows the 94-6 radio in a leather case with the
antenna plug in place. More images below.
At the moment we don't know how the antenna rods were mounted to the
antenna plug.
|
|
|
|
Determining the age of the radio can be a bit tricky, first of all
because all text is in Japanese and secondly because the Japanese
have a variety of different calendars. In order to determine the
age of a 94-6 radio, we have to investigate the
serial number tag that is mounted
on the top lid.
|
The top shield with the red lettering is just a warning.
It says: SECRET. The bottom shield is the actual
name and serial number plate.
It contains information about the manufacturer
(Takanashi), the serial number (17899) and the manufacturing date.
The prefix tells us that the Showa calendar is used (昭和),
which counts the years of the reign of Emperor Hirohito
(1926 is year 1).
The engraved numbers tell us that the device was manufactured
in December (一二月) of Showa-year
17 (一七年), which is 1942.
|
|
|
Sometimes it is also possible to dermine the age from the markings
on the meter scale. At the bottom left of the
meter scale is the text 昭和18昭和
2昭和 which translates to February 1943.
Several websites may be of help when translating and interpreting
Japanese letters and numbers, such as [5] and
[6]. We currently don't know the meaning of the other text on
the S/N tag.
|
The Japanese clearly had servicability in mind when they designed the 94-6,
as all components are clearly numbered. The following list can be used as
a rough index to the various parts [6].
|
- Antenna connection
- Counterpoise connection
- Antenna current meter
- Mica capacitor 450/1500
- Coil
- Variable capacitor
- Mica capacitor 450/1500
- Mica capacitor 450/1500
- Coil
- Regeneration control 29K
- RFC
- Mica capacitor 450/1500
- Mica capacitor 450/1500
- Valve socket
- Power switch (TX/OFF/RX)
- Filament rheostat
- Capacitor in metal can
- Wire-wound resistor (250 Ohm)
- Transformer 1:20
- Transformer
- Mica capacitor 450/1500
- CW key assembly
- Tone/Voice switch
- Socket for headsets/handsets
- Generator power socket
- Battery power socket
- Mica capacitor 4500/1500
- Carbon resistor
- 3-position band switch
- Coil
- Coil (mounted on #9)
- Mica capacitor 450/1500
|
- James H. Smith, How Jap Radio Transmitters Work - In US Hands
QST, September 1943. pp. 44, 45 and 59.
- Helmut Liebich, Ein japanischer UKW-Transceiver - Kein Testbericht
CQ-DL, August 1983. pp. 372-373.
- Dick Rollema (PA0SE), Japan's Hush-Hush Rushbox
73 for Radio Amateurs, March 1986. pp. 9-12.
- Wikipedia, Japanese Calendar
Retrieved June 2012.
- I18n Guy website, Calendars: Japanese Emperor Date
Retrieved July 2012.
- LTC William L. Howard, Japanese Type 94-6 Radios
Retrieved June 2012.
|
|
|
|
Any links shown in red are currently unavailable.
If you like this website, why not make a donation?
© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Wednesday, 30 April 2014 - 21:32 CET
|
 |
|
|
