|
|
|
|
|
|
|
Italy
World War II spy radio set
RN-3 is a two-piece spy radio set, introduced in 1942
by Nova Radio in Milano (Italy), and later also by
Construzioni Elettromeccanische, also in Milano.
Based on the SE-85/14 of the
German Abwehr, it consists of a TRN-3 transmitter
and an RRN-3 receiver, usually supplied in a cardboard suitcase.
It was used during World War II (WWII)
by the Italian intelligence services. The transmitter and the receiver
both cover the shortwave (HF) radio band from 3.5 to 7.5 MHz.
|
The image on the right shows a typical RN-3 set in a
brown letherette cardboard suitcase.
Inside the suitcase is a wooden frame with three
compartments: one for the receiver, one for the transmitter,
and one for the ancillaries, such as the morse key, the
crystals and the headphones.
The transmitter has an internal power supply unit (PSU), and is
powered directly from the local mains network. It has a socket at the front
panel at which the power for the receiver is available.
The receiver is suitable for AM (A3) and CW (A1), but the
transmitter is only suitable for CW (A1).
|
|
|
|
The transmission frequency is determined by a quartz crystal that
must be installed on the transmitter's front panel (QUARZO). The receiver
is free-running. The design of the RN-3 is largely based on the
SE-85/14 of the German Abwehr,
which was introduced in 1938. However, rather than using a separate PSU
like the SE-85/14, the receiver takes its power from the transmitter.
|
The image below provides a quick overview of the features of the receiver
(left) and transmitter (right) of the RN-3 spy radio station. The
transmitter contains the power supply unit (PSU) and must be connected to
the mains AC network.
Note that is must be configured for the local mains voltage
first. The receiver obtains its power from the transmitter via a short
cable with a plug.
The receiver has sockets at the top left for antenna and ground.
At the bottom right is a socket for connection of the (high impedance)
headphones. The three-valve receiver is free running and covers the entire
frequency range (3.5 - 7.5 MHz) in a single band. The single-valve
transmitter is crystal-operated and has controls for tuning the oscillator
and the antenna circuit. It has several antenna sockets, each of which
matches a particular sub-band. At the top left is a socket for connection
of the morse key. Although a suitable miniature morse key was
supplied with the set, most operators preferred to bring their own key
as it was more stable and could be adjusted.
|
- NOVA Radio (Milano)
This is believed to be the initial manufacturer of the RN-3.
The devices can be recognised by the mint green crackle-paint front page,
and a name tag at the rear of the transmitter's and receiver's enclosures.
Furthermore, both the transmitter
and the receiver have an ACC/SP switch at the front panel that enable
the power. It has white sockets for antenna, crystal, morse key
and headphones.
- Construzioni Elettromeccanische Milanesi (Milano)
This is a later version from a different manufacturer, also from Milano
(Italy). It has bright grey front panels,and black sockets for antenna,
crystal, morse key and headphones. Furthermore, the ACC/SP switches are
missing, which means that the device is always fully powered as soon as
it is connected to the mains.
|
|
|
Differences with SE-85/14
|
|
|
- Exterior colour (mint or bright grey, rather than black)
- Inscriptions (Italian rather than German) 1
- Receiver takes power from transmitter (rather than from separate PSU)
- Filter in receiver's HT rail
|
-
Note that some Abwehr radios — in particular the ones that were
made for the Italians — also had Italian inscriptions on its
front panel.
|
The RN-3 was usually supplied in a suitcase, such as the one
shown in the image on the right. Other types of suitcases are
also known. The device can be operated from within the case.
The dimensions of the suitcase are choosen such that receiver and
transmitter can be fitted side-by-side, leaving a small area at the
front for the ancillaries (power cable, headphones, morse key,
crystals, antenna wires, etc.
|
|
|
The transmitter is the central part of the RN-3. It contains the
PSU which also feeds the receiver. It is based around a single
6L6 valve (tube) that acts as oscillator as well as Power Amplifier (PA).
To transmit, a quartz crystal for the desired frequency must be
installed in the socket marked QUARZO, whilst the oscillator (SINTONIA)
and the antenna circuit (SINT AEREO) must be tuned for maximum signal,
using the meter as an aid to obtain a maximum reading.
|
|
|
The receiver is housed in a similar enclosure as the transmitter,
although it weighs far less as it doesn't have its own PSU.
Instead it is powered from the transmitter via a short fixed lead.
The free-running receiver is built around three EF6 valves (tubes)
that are used as RF amplifier, detector and AF amplifier respectively.
Headphones must be connected at the bottom right. Note that the receiver
requires a separate wire antenna and ground connection
(i.e. the antenna is not shared with the transmitter).
|
|
|
Although virtually any type of morse key can be connected to the
TRN-3 transmitter, the set was usually supplied with the miniature
morse key shown in the image on the right.
It is finished in black or grey wrinkle paint, and should be
connected to the socket marked TASTO.
At the other end of the cable are two banana-type plugs, or
a single mains plug as shown in the image on the right. The pin
distance is correct for the socket.
|
|
|
For reception, a pair of high impedance headphones was used, such
as the one shown in the image on the right. The one shown here was made
for the German Wehrmacht by Telefunken.
Note that the headphones are connected in series with the anode of the
AF amplifier valve, which means that it carries a potentially lethal
high tension (HT) voltage. Ensure that both wires and the metal shells
are appropriately isolated.
|
|
|
The RN-3 came with two wooden spools with antenna and counterpoise wires,
such as the ones shown in the image on the right. They consist of a
wooden or cardboard spool onto which seveal metres of wire is wound.
At one end of each wire is a ceramic isolator. At the other end is a
regular 4 mm banana plug.
Note that transmitter and receiver require separate antennas.
They cannot share one antenna wire.
|
|
|
The RN-3 was supplied with some spare parts and accessories,
such as spare valves (tubes), spare fuses, crystals
and ceramic isolators for the antenna wires.
The image on the right shows the surviving spare parts that
came with the RN-3 in our collection.
|
|
|
Below is the circuit diagram of the transmitter as it was printed in the
original manual [1]. The transmitter is based on a single 6L6 valve (tube)
that acts as oscillator and power amplifier (PA). The crystal is connected
between the g1 and ground. The tuning circuit consists of C2 and L2,
with L2b forming the antenna circuit. The current through L2b can be measured
with a meter that is connected via transformer TR2. Each sub-band has its own
antenna tap on coil L2b.
|
| |
TRN-3 transmitter circuit diagram
|
The transmitter is powered by the internal PSU,
which is connected to the mains via switch S1. 1
When S1 is closed, the filaments (LT) are powered and the HT voltage
is applied to the anode of V1. Nevertheless, the valve will not oscillate
until the morse key is closed. Closing the key completes the circuit by
connecting the cathode of V1 virtually to ground.
|
 |
-
Switch S1 is missing from RN-3 radios manufactured by
Construzioni Elettromeccanische, which means that transmittes from
that manufacturer are powered as soon as they are connected to the mains.
|
Below is the circuit diagram of the RN-3 (RRN-3) receiver as it was printed
in the original manual [1]. The circuit is very similar to the designs of the
German R-75 and E-97/E-98 receivers,
albeit with different valves. The three stages (RF amplifier, Detector and
AF Amplifier) are each based around an EF6 valve.
The receiver is powered from the transmitter via the 3-pin connector at the
top left. Note that the filament voltage (LT) is always present (when the
transmitter is on), but that the HT voltage runs via switch S1. 1
As soon as S1 is closed, the receiver will be active.
|
| |
RRN-3 receiver circuit diagram
|
The receiver is free-running and covers the entire frequency range from 3.5 MHz
to 7.5 MHz in a single band. Frequency tuning is achieved by C1a and C1b which
are running in tandem. Furthermore, the user has to adjust the Reaction
potentiometer to make the detector circuit work as intended. The volume of
the AF output signal is adjusted with the Volume potentiometer.
Note that the headpohones are connected in series with the anode of V3, which
means that it carries the HT voltage. For safety reasons always check whether
the headphones are properly isolated.
|
|
-
Switch S1 is missing from RN-3 radios manufactured by
Construzioni Elettromeccanische, which means that receivers from
that manufacturer are powered as soon as they are connected to a
(powered) transmitter.
|
The transmitter is built on a U-shaped chassis that is bolted to the
front panel. The image on the right shows the chassis as seen from the
rear, with the front panel facing away. At the right are the two valves.
The one closest to the front panel is the 6L6G. The other one is the
5Z3 rectifier, which is part of the PSU.
The mains transformer is mounted in the lower part (not visible here).
The mains voltage selector (screw terminal)
is embedded in the rear pa–nel. It can only be accessed when the
transmitter is removed from its enclosure.
|
|
|
The construction of the receiver is very similar to that of the
transmitter. The image on the right shows the chassis of the
receiver as seen from the rear. At the centre is the large
tuning capacitor. The three (red) EF6 valves are mounted at
either side of the tuning capacitor. The antenna coil is
visible at the right, near the front panel.
The passive components are located in the bottom part of the
chassis (not visible here).
|
|
|
When we received this spy radio set in June 2026, it was in unknown
condition. The two modules (transmitter and receiver) are cosmetically
in excellent condition, as if they left the factory yesterday.
The cardboard suitcase was dry but dirty and showed the usual scuff marks,
but was otherwise complete and in good condition. A quick inpection
of the interior of transmitter and receiver, confirmed the impression
that this radio set had been preserved very well, despite its age (80+).
This radio set is currently awaiting restoration.
|
Suitcase dry and scuff marks Felt pads inside suitcase completely disintegrated Morse key missing Antenna and counterpoise wires missing - Radio set in unknown electrical condition
|
- Suitcase superficially cleaned and treated with colourless wax
- Wooden frame treated with dark wax
- Felt padding renewed with new-old-stock (NOS) material
- Matching antenna wires with spools found
- Morse key found on eBay
- Morse key fully restored: cable and plug replaced, pressure spring added
- Mains power cord replaced by neoprene alternative (with ground wire)
- Receiver power cord replaced by neoprene alternative; connector refitted
|
Morse key Spools with antenna wires - Manual
|
The voltage of the RN-3 must match the voltage of the local power network.
To set the voltage, disconnect the transmitter from the mains. Note that the
capacitors inside the device may still be charged, which is potentially lethal.
Next, remove the transmitter from its enclosure
(single screw at the back) and identify the
vol–tage selector at the rear of its chassis.
There are five 'slots', each of which is marked with a voltage (110, 125, 145, 160
and 220). A screw is installed in one of the slots. Move it to the slot with the
same voltage 1 as the local network.
|
|
|
-
Note that the mains voltage in continental Europe today is specified at 230 V,
and that in most locations it will be around 240 V. This may cause the mains
transformer inside the transmitter to saturate, as a result of which it may
run hot. This may eventually lead to irrepairable damage.
It is advised to connect the transmitter to the mains via a VARIAC
that is set to a maximum output voltage of 220 V.
|
|
The receiver has a fixed power cable that must be
connected to the power socket
at the top left of the transmitter's front panel.
The plug on the receiver's cable has three wired contacts
plus a thick alignment pin. Below is the pinout of the
transmitter's socket when looking into it.
|
× Unused (guide pin) GND Ground HT Anode voltage (+350 V/DC) LT Filament voltage (6.3 V/AC)
|
|
Device Spy radio set Purpose Two-way Agent-Base communication Model RN-3 Manufacturer • NOVA Radio (Milano),
• Construzioni Elettromeccanische (Milano) Year 1942 Country Italy Users Agents, Military intelligence Based on SE-85/14 (Abwehr) Frequency 3.5-7.5 MHz Dimensions (HWD) 190 × 500 × 350 1 Weight 10,3 kg 1
|
-
Complete with all accessories and in the suitcase featured here.
|
Model TRN-3 Frequency 3.5-7.5 MHz Output 10-15 Watt Waveform A1 (CW) Valves 6L6G (oscillator, PA), 5Z3 (rectifier) Power Mains 110/125/140/160/220 V/AC (internally selectable) Dimensions (HWD) 120 × 200 × 220 mm Weight 5300 g
|
Model RN-3, RRN-3 Frequency 3.5-7.5 MHz Waveform A3 (AM), A1 (CW) Valves 3 × EF6 Circuits RF amplifier, Detector, AF amplifier Power +350 V/DC, 6.3 V/AC (from transmitter) Dimensions (HWD) 120 × 200 × 220 mm Weight 2500 g
|
011 RN-3 Bonhams, 2024-02-14 030 RN-3 Crypto Museum, Netherlands 023 RN-3 Antonio Fucci, Italy
|
RN-3 = complete set, TRN-3 = transmitter only, RRN-3 = receiver only.
|
|
|
|
Any links shown in red are currently unavailable.
If you like the information on this website, why not make a donation?
© Crypto Museum. Created: Friday 03 July 2026. Last changed: Saturday, 03 October 2026 - 21:41 CET.
|
|
|
|
|
