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DDR
RFT
RX
OWVL
Cold War
BND
CIA
  
Ilmenau 210
DDR domestic MW/SW receiver · 1959

Ilmenau 210 was a domestic valve-based receiver for the Medium Wave (MW) and Short Wave (SW) radio bands, manufactured from 1959 to 1962 by VEB Stern-Radio Sonneberg in Köppels­dorf (Thüringen) in the former DDR (East-Germany). As it was one of the few radios in the DDR that could receive the 3-4 MHz band, it was selected by Western intelligence agencies like the CIA, for use by its agents operating inside the DDR, for the reception of Numbers Stations (OWVL) [5].

The radio is housed in a bakelite enclosure, and has plastic front and rear panels. At the front is the volume knob – also the ON/OFF switch – the speaker, the tuning dial and a three-button band selector marked Kurz I (SW 1), Kurz II (SW 2) and Mittel (MW). According to the rear panel, it was also known as the Kleinstsuper 1 64/72 W 210.

The radio can be powered by a mains AC voltage between 110 and 220V, selectable with a dealer-configurable wire link that is located behind a transparent plastic window in the rear panel. It requires the plastic back panel to be removed.
  
Ilmenau 210 radio

Ilmenau 210 was available around 1960 for a price of 180 DDM, which was a substantial amount for the average DDR citizen at the time. It was often used as a second radio in the kitchen or the office. It is very similar to the Ilmenau 480 — manufactured on the same production line — which differed only in frequency range (SW, LW, MW). As Ilmenau 210 covered the 3-4 MHz band, it was purchased by CIA agents on the local market, which soon made the radio a suspicious item [5].

Ilmenau 210 was in production until 1962, after which it was gradually replaced by all-transistor models, like the portable Sternchen, which were no longer suitable for reception of the 3-4 MHz band. 2 This prompted the German intelligence service BND to develop an external SW-converter.

  1. Kleinstsuper = miniature superheterodyne receiver.
  2. There were other radio receivers on the market in the DDR that were capable of receiving the SW band, but they were not suitable for frequencies below 6 MHz, making them unsuitable for CIA/BND use.

Ilmenau 210 radio
Front view
Band selector
Rear side
Rear view
Antenna and ground sockets
Brand name and description embossed in the plastic back panel
Mains voltage selector (110 to 220V)
A
×
A
1 / 8
Ilmenau 210 radio
A
2 / 8
Front view
A
3 / 8
Band selector
A
4 / 8
Rear side
A
5 / 8
Rear view
A
6 / 8
Antenna and ground sockets
A
7 / 8
Brand name and description embossed in the plastic back panel
A
8 / 8
Mains voltage selector (110 to 220V)

WARNING — It should be noted that the radio uses a so-called autotransformer [4] , as a result of which the chassis (and even the screw of the volume knob) may carry the full 110V or 220V AC mains voltage, which can potentially be lethal. For this reason, the four screws at the bottom – used to hold the chassis inside the bakelite enclosure – have plastic caps. For demonstrations, it is advised to use an isolation tranformer.



Interior
Ilmenau 210 is housed in a bakelite encosure with plastic front and rear panels. Its interior can be accessed by removing two screws at the left and right edges of the rear panel, after which the rear panel can be taken off. This exposes the interior of the radio, as shown in the image above.

Inside the enclosure is a metal frame, which is bolted to the bottom of the bakelite enclosure by means of four screws with plastic heads. This is necessary, as the device is powered by an auto­transformer [4], as a result of which the chassis may carry the 110V or 220V mains AC voltage.

Before removing the frame from the enclosure, it is necessary to remove the volume knob – held in place by a single screw – and the tuning dial, which is clamped. It has to be removed carefully, as it might be binding to the axle and the plastic scale may have become brittle over the years.
  
Tuned circuit for the three bands

Once the knobs have been removed, the chassis can be removed from the enclosure, leaving the speaker and the output transformer bolted to the front panel. The circuits are built onto a printed circuit board (PCB) that is fitted to the metal frame. At the left is a vertical PCB with the tuned circuits of the 3 band filters. Behind it, is a tuning capacitor with two sections moving in tandem.

At the right is a small PCB with the mains AC voltage selector. It is here set to 220V, which might be too low for the 230V AC mains voltage in Europe. It may cause the transformer to go into saturation, with results in overheating and eventually irreparable damage to the transformer. It is advised to use an isolation transformer, which also converts the 230V down to 220V or less.

Read side
Rear view
Tuned circuit for the three bands
Interior detail
Mains AC voltage selector
B
×
B
1 / 5
Read side
B
2 / 5
Rear view
B
3 / 5
Tuned circuit for the three bands
B
4 / 5
Interior detail
B
5 / 5
Mains AC voltage selector

Specifications
  • Type
    Superheterodyne
  • Modulation
    AM
  • Bands
    3 (see below)
  • IF
    473 kHz
  • Circuits
    6
  • Valves
    ECH81, EBF89, ECL81, EZ80
  • Power
    Mains AC 110V, 127V, 150V, 180V, 200V, 220V — 50/60 Hz
  • Dimensions
    270 × 160 × 135 mm
  • Weight
    2.7 kg
  • Manufacturer
    Stern-Radio Sonneberg (RFT-VEB)
  • Year(s)
    1959-1962
  • Price
    180 DDM
Bands
  • Mittel
    MW
    510 - 1650 kHz
  • Kurz I
    SW1
    9 - 22 MHz
  • Kurz II
    SW2
    3.15 - 7.4 MHz
Documentation
  1. Ilmenau 210, circuit diagram
    Retrieved from Georg Knöchel [3].
References
  1. Karsten Hansky, Ilmenau 210 radio - THANKS !
    Received October 2020.

  2. Radio Museum, Ilmenau 210 64/72W
    Retrieved October 2020.

  3. Georg Knöchel, Stern-Radio Sonneberg Ilmenau 210
    Retrieved October 2020.

  4. Wikipedia, Autotransformer
    Retrieved October 2020.

  5. MfS, Brief Assessment of the Investigation Results Archived in 1961 in Work on Crimes
    of Espionage (English translation). Retrieved from Wilson Center Digital Archive.
    9 January 1962. BStU, ZA, Mfs-HA IX, Nr. 4350, pp. 226-235.
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Crypto Museum. Created: Tuesday 06 October 2020. Last changed: Friday, 09 October 2020 - 16:54 CET.
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