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Clandestine spy radio station - wanted item

SIRIUS III was a modular spy radio set, developed in Czechoslovakia around 1966, by Správa 6 1 for use by the secret state police (StB) and by the secret intelligence agency Sprava 1. It was the successor to the SIRIUS spy radio station, and was usually supplied in a suitcase, together with a MERKUR or MERKUR II receiver and a MĚSIC burst encoder [1]. It is also known as project TI-526.

The diagram below shows a complete SIRIUS III spy radio set in transit case, which is part of the collection of the Police Museum in Prague (Czechoslovakia) [2]. At the right are two units of equal size: the transmitter at the right and the Power Supply Unit (PSU) at the centre, with the mains power cable inbetween. To the left of the PSU are two smaller units: the MESIC burst encoder (at the front) and the MERKUR receiver (towards the rear). The accessories are stored at the back.

Complete SIRIUS III spy radio set in suitcase. Photograph Copyright Detlev Vreisleben [2].

The four units are connected together by means of three short U-shaped cables (not shown here), with the PSU acting as the central hub. The station was supplied with cables, wire antennas, earphones and calibration crystals (none of which are shown here).

Block diagram
As the transmitter shows great resemblance to the original SIRIUS transmitter, we've taken the block diagram of that device as a guide. The transmitter is VFO-operated, which means it can be set to any frequency in its range. The VFO can be calibrated with a built-in crystal oscillator.

Sirius III transmitter block diagram

Valves   tubes
  • ECC85
  • E180F (3x)
  • QE05/40
  • Frequency
    8-16 MHz (or 3.2-7.9 MHz)
  • Modulation
    A1 (CW) or F1 (500 Hz FSK)
  • RF output
    75W (with Mesic keyer, or 12W with manual key)
  • SIRIUS III transmitter
  • Mains power supply unit
  • MERKUR (or MERKUR II) receiver
  • MESIC burst encoder
  1. Miro Horník, OM3CU, Personal correspondence
    August 2015.

  2. Detlev Vreisleben, Photographs of SIRIUS III radio set
    Germany, 10 February 2005. Received August 2015.

  3. Louis Meulstee, Wireless for the Warrior, Part 4 Supplement
    Forthcoming. Accessed August 2015.
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Crypto Museum. Created: Thursday 20 August 2015. Last changed: Thursday, 01 March 2018 - 08:21 CET.
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