|
|
|
|
|
|
WWII intercept receiver
The R-IV, or R4,
was a communications intercept receiver,
developed by
Siemens
and used during WWII by the German secret service, the Abwehr.
The R4 was based on the pre-war Siemens R-II (R2),
that in turn was a copy of the National HRO receiver,
similar to other copies, like the Körting KST.
Although the design of the R4 is based on the HRO,
it has a number of differences.
|
The receiver roughly has the same size as the National HRO
and covers a frequency range from 3.15 to 33 MHz. It was suitable for
the reception of AM and CW (morse).
A major difference with the HRO is that the
coil packs
are not inserted at the front, but at the top left of the receiver.
The frequency dial
resembles that of the HRO, but contrary to popular
believe [6], the tuning section was not obtained from National during
the war, like it was done for the Korting (KST) receiver.
Although it is similar in design, the Siemens one
differs from the original HRO one.
|
|
|
In his book Die deutschen Funknachrichtenanlagen bis 1945 [6],
Fritz Trenkle classifies the R-IV an HRO-copy, but this seems to be
incorrect. There are far too many differences with the original HRO
design to call the R-IV a copy. 1
Furthermore,
according to personal notes that were recently discovered in the estate
of a late collector [4],
the design of the R-IV, introduced in 1940/1941,
was based on the pre-war Siemens R-II (R2) receiver,
that in turn was a copy of the National HRO.
It appears that Siemens bought
the original HRO tuning units directly from National until 1939 [5].
After the outbreak of war, Siemens no longer had access to the original
parts from National and was forced to redesign the radio,
As far as we know, there are no surviving R-II receivers.
Based on the serial numbers of the surviving R-IV receivers, it seems likely
that only a couple of hundreds were built. There appear to be two
production runs: the so-called 4-series, of which the serial number starts
with a '4', and the 5-series, that have a serial number starting with '5'.
The receiver was available in two colours: dark green, as shown in the
image above, and grey as shown below.
Siemens R-IV receivers are extremely rare and are highly wanted
by collectors.
|
 |
-
Trenkle is not the only source that mentions the Siemens R-IV
as a copy of the National HRO, but it appears that most authors are
quoting from his publication Die deutschen Funknachrichtenanlagen
bis 1945 [6].
|
The Siemens R-IV shown in the images above is housed in a dark green enclosure
and has a serial number starting with '4'. Another R-IV unit, shown below,
is housed in a grey case and has a serial number that starts with
a '5'. This suggests that all 5-series machines may have been grey.
|
The machine shown here has been 'amateurized' and has a few extra knobs
at the right half of the front panel. Furthermore, the front panel has been
partly restored. Eventually, this machine will be brought back to its original
condition.
Apart from a few manfacturing differences, such as the square capacitors
in the compartment at the right, this version is identical to the
4-series R-IV (i.e. the version in the green case).
|
|
|
|
|
|
|
|
|
|
The image below shows the front panel of the Siemens R-IV receiver,
that holds all controls and connections. The antenna connections are at the
left center, with a socket for the earth (ground) at the bottom left.
At the center of the front panel is the typical tuning dial, which resembles
the micrometer tuning dial of the National HRO. The dial of the R-IV however,
was manfactured by Siemens and has an additional fine tuning knob
at the left, that drives the main dial. This is very useful on
the 80 meter band, which is packed with narrowband signals.
The fine tuning dial can be disengaged
by pushing it to the left, after which the main dial can be moved freely again.
The remaining controls are at the right half of the front panel.
At the top are two meter: one for measuring the signal strength and one
for checking the internal voltages. The three knobs are for adjusting the
bandwidth, the BFO (tone) and the audio volume. At the bottom are the
switches for enabling the filter, the AGC and the BFO. The rightmost switch
is the power switch (on/off). To the left of the switches are sockets for
two pairs of headphones. At the bottom right is a 5-pin socket for connection
to the mains power supply unit (PSU).
|
The R-IV is extremely service friendly. Its interior can be accessed from
two sides: the top and the bottom. All valves can be accessed from the top
of the unit, simply by lifting the upper panel (just like on the National HRO).
The upper panel has been constructed in such a way that the coil pack can
be left installed when the lid is opened.
The top section of the receiver is divided into three compartments:
the right compartment with 5 valves and some capacitors, a compartment
at the rear with 4 valves and one at the front that is the slot
for one of the three the coil packs.
|
|
|
|
|
|
|
|
|
|
Each R-IV receiver was supplied with three plug-in coil packs.
Rather than at the front of the receiver, as with the National HRO,
the coil packs of the R-IV were inserted into a slot on top of the device.
A second coil pack was usually placed at the right side of the top surface.
Each of the three coils packs had a different frequency range, giving the
receiver a total frequency coverage of 3.15 - 33 MHz (9 - 95 m).
The table below shows the frequency range of each coil pack.
|
|
Plug-in
|
Range
|
Frequency
|
|
|
|
0
|
9 - 18 m
|
16.5 - 33 MHz
|
|
1
|
17 - 40 m
|
7.5 - 17.5 MHz
|
|
2
|
40 - 95 m
|
3.15 - 7.5 MHz
|
|
|
|
|
Each coil pack consists of a die-case aluminium alloy case with eight
compartments: four small ones and four larger ones. The larger compartments
each contain a single coil wound on a ceramic body. The smaller compartments
contain the adjustable capacitor for each section.
|
The R-IV came with its own proprietary Power Supply Unit (PSU) that
was usually placed to the right of the receiver. It supplied the various
HT and LT voltages and was connected to the rectangular 5-pin socket at
the bottom right of the front panel, with a tick rubber cable.
|
The image on the right shows the PSU of the Siemens R-IV after the top cover
of its case has been removed. The design is rather straightforward and
consists of a transformer, a valve-based rectifier and several capacitors.
The unit is marked Netzanschlußgerät für Empfänger R IV (mains
connection device for receiver R4).
At the front of the PSU are two cables: on for connection to the mains
(Netz) and one for connection to the reciver (Empf.). Also at the front panel
are the fuse, a voltage selector and the on/off power switch.
|
|
|
|
Each R-IV receiver came with a small metal box, roughly the size of a
coil pack, in which the spare valves were kept. The box was padded with
wood chips in order to prevent the valves from getting damaged in transit.
As the R-IV contains four different valves (3 x EF11, 3 x EF12, 2 x EF13
and 1 x ECH11), the box contained just four black metal valves (German:
Stahlröhren).
|
|
|
|
As the Siemens R IV was used by secret services during WWII,
pictures of the radio in use are just as rare as the device itself.
Below an overview of the pictures we have found so far. If you are
aware of any other images that show this receiver, please contact us.
|
The Siemens R4 was used during WWII by the
German intelligence service, the Abwehr.
The image below shows a soldier at work in the secret radio
station of the foreign department of the Abwehr (OKW-Amt Ausland/Abwehr).
The device as the left is the Power Supply Unit (PSU).
Above the radio, mounted on the wall, is the antenna
selection unit. At the right is an identical setup.
The image below shows another Abwehr radio operator at work. This photograph
clearly shows the frequency dial being operated. A major difference with the
HRO receiver
is that the coil units were plugged-in from the top at the front
left. A spare coil pack it placed on top of the receiver (at the right).
Apparently this was common practice as it is also visible in the image above.
|
We are currently looking for the following:
|
- Circuit diagram of the R-IV.
- Information about the Siemens R-II receiver.
- Images of the R-II receiver.
|
-
Document kindly supplied by Günter Hütter [1].
|
|
|
|
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: Thursday, 03 July 2014 - 08:36 CET
|
|
|
|
![Copyright German Federal Archives (Bundesarchiv) [2]](img/abwehr.jpg "Copyright German Federal Archives (Bundesarchiv) [2]")
![Copyright unknown [3]](img/abwehr1.jpg "Copyright unknown [3]")
