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Covert surveillance detection receiver - wanted item

SRR-100 was a covert body-worn receiver, or scanner, developed in the 1970s by the Office of Strategic Services (OTS) and the Office of Communications (OC) of the US Central Intelligence Agency (CIA), and probably 1 manufactured by Motorola. It was used during the Cold War for intercepting the radio communications of Soviet and other Eastern Bloc surveillance teams, and comprises a miniature receiver, an inductive neckloop/antenna and a wireless Phonak earpiece.

The basic version measures 96 x 54 x 12 mm. It has two knobs at the top, one for controlling the volume and one for selecting the desired mode of operation. At the left is a 4-pin socket for the neck­loop. At the bottom is a circular screw that gives access to the battery compartment. The unit is powered by two 1.35V mercury batteries.

The neckloop serves two purposes: it is used as the antenna, and as an inductive loop or coil for delivering audio to the wireless Phonak earpiece.

The receiver is capable of intercepting FM radio signals in the 102 MHz band (3 metres), that use inversion-based speech scrambling. It was usually carried in a cloth harness or pocket under the clothing of the CIA operative. It was deployed in Eastern Block countries like Russia (USSR) and East-Germany (DDR), to ensure that the operative was black, which means that he or she was free from adversary surveillance.

The image on the right shows a close-up of the SRR-100 as described in surviving MfS (Stasi) 2 reports about confiscated US covert equipment.

The SRR-100 is similar to the Russian Kopchick receiver, which serves the same purpose. It was developed around the same time as the SRR-100, but it is currently unknown who was first. The SRR-100 seems to be the more advanced one, as it uses a wireless Phonak earpiece.
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Unlike the SRR-100 however, the Kopchik was a non-selective or aperiodic receiver, which means that it could pickup any signal in its vicinity, regardless the frequency.

  1. This is unconfirmed, but seems likely when considering the construction and the selected materials, such as the knobs. At the time, Motorola had a highly secret Goverment Electronics Division, that worked exclusively for US intelligence agencies like the CIA and the NSA.
  2. Ministerium für Staatssicherheit (MfS), commonly abbreviated as Stasi, was the repressive intelligence and secret police organisation of the former DDR (East-Germany).  More

Help required — We are looking for detailed information about the SRR-100 receiver and, if possible, a working unit. If you can provide any of these, or any other information, please contact us.
The diagram below shows the various features of the SRR-100 when looking at the device from the front. The controls and connections are in a recessed area at the top. The two knobs at the centre are for volume control and mode of operation selection. At the left is a 4-pin socket for connection of the induction loop, which also acts as the antenna. The induction loop is carried around the neck and passes the audio to the Phonak earpiece. The loop also acts as the antenna.

At the right is the recessed TEST push-button, which should be pressed to check the operation of the device. The unit is powered by two 1.35V mercury batteries (connected in parallel) that are installed via the hinged access door at the bottom. Depending on the setting of the audio volume, the batteries allow between 3 and 10 hours of uninterrupted operation. According to the hand­written marking on the front panel, the device was last check and approved on 19 July 1979.

Mode of operation
The MODE-selector on top of the device has the following settings:

  1. Off
    Power off
  2. S
    Standby (AFC disabled)
  3. N
SRR-100 Mark I
There were at least two versions of the SRR-100: the initial single-channel version, and an expanded version with six channels. The diagram below shows the top panel of the single-channel version, which is just 12 mm thick. Crystal and batteries are installed at the bottom.

Educated guess of the layout of the top panel of the SRR-100

This version is suitable for the entire 101.8 - 103.4 MHz frequency range, but can only receive one channel at a time. This means that the frequency used by the Russian surveillance teams had to be determined carefully before each mission, after which a suitable crystal was installed in the SRR-100. The device found by the KGB on CIA officer Martha Peterson when she was arrested in Moscow on 15 July 1977, was of this type. It was fitted with a crystal for 103.25 MHz [8] .

The image below shows a complete SRR-100 kit, consisting of the SRR-100 receiver unit (left), a neckloop that acts at the antenna and as inductive audio coil, a white cloth holster or body harness, a phonak earpiece and a set of spare hearing aid button-type batteries for the earpiece. The photograph is taken from Stasi reports about confiscated equipment [2][8]. Click to enlarge.

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The device in the image is the original SRR-100 (i.e. Mark I), that did not have the bolted-on modification. The body harness was designed for the male body, and was less suitable for females, which is why CIA officer Martha Peterson made her own cloth pocket.

 More about Martha Peterson (CIA)

SRR-100 Mark II
The enhanced version is suitable for six crystal-based channels in the 102 MHz range. It is shown in the photograph below and is basically a standard SRR-100 with an additional module bolted to its rear side. The colour of the add-on is slightly different from the basic unit, which suggests that it was added later, perhaps as an aftermarket upgrade. The combined top panel is shown below. At the left is a coaxial socket that might have been used for the connection of an antenna. At the right is a white push button that is used for the selection of one of the six channels.

Educated guess of the layout of the top panel of the SRR-100 Mark II

The rear unit is bolted to the basic unit. This was probably done by removing the rear panel from the SRR-100 and fitting the expansion unit in its place. The add-on holds the crystals for the 6 channels, which are accessible from the bottom. The interior is shown further down this page.

The photograph above was taken by the Polish intelligence service SB, following the arrest of CIA case officer Peter Burke on 18 November 1979. Burke, who had assumed his position as Second Secretary of the Political Section of the US Embassy in Warsaw a few month earlier, was known by Polish intelligence by the cryptonym Amon-79. As the SB suspected him of working for the CIA, he was placed under surveillance by Department II of the Polish MoI and Bureau B of the SB [9].

In the early morning of 18 November 1979, he was caught red-handed whilst retrieving a dead-drop that his Polish agent had failed to pick up on 29 September. Violating the diplomatic status of Burke's car, the SB — disguised as police officers — found the dead-drop package under his seat, along with an SRR-100 receiver, fitted with crystals for the radio frequencies of Bureau B in the 102 MHz band. They also found a commercial Panasonic pocket FM-band radio on him [9].

The SB had also filmed the entire operation, which is available on YouTube, complete with an introduction (in Polish) [10]. The Panasonic RF-015 pocket radio appears at 41:03. The SRR-100 appears at 40:37 and again at 41:39. This is the actual device that is shown in the image above.

Original SB footage — I am an American Diplomat [3]

The SRR-100 set consists of the following parts:

  • SRR-100 receiver
  • Phonak earpiece
  • Neckloop
  • Batteries
  • Harness
The wireless earpiece is made by Phonak in Switzerland, and consists of a pick-up induction coil, a battery, an amplifier and a miniature loudspeaker. It operation is similar to a hearing aid which is set to telephone-input.

To make the earpiece invisible, the CIA made silicone reproductions of the operative's real ears, that obscured the Phonak device.

Equipment in Moscow
The image below shows the kind of equipment the the Russian KGB (now: FSB) found on American agents during the Cold War [1]. At the rear left, just in front of the leftmost portable radio, is an SRR-100 receiver with inductive neckloop. The SRR-100 was probably recovered from CIA case officer Martha Peterson when she was arrested on 15 July 1977 after making a dead drop for the Russian spy Aleksandr Dmitrievich Ogorodnik, codenamed TRIGON. Click for a close-up  More

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Detection runs in Moscow
The online magazine WIRED has made an interesting series of YouTube videos, in which Jonna Mendez — former CIA Chief of Disguise of the Office of Technical Service (OTS) of the CIA — talks about some of the tactics and gadgets they used during the Cold War. In the episode below she explains how the SRR-100 receiver was used during surveillance detection runs in Moscow [3].

Former CIA Chief of Disguise Jonna Mendez explains how the SRR-100 was used [3]

Below is the only photograph of the interior of an SRR-100, that was found in a KGB/Stasi report of the 1980s. It shows the interior of the add-on of an SRR-100 Mark II (i.e. the part that is bolted to the rear of the basic unit). At the top is the white push button for selection of the desired channel. At the bottom are the crystals for the six channels in the 102 MHz range.

At the center is a double-sided printed circuit board (PCB) that is populated with miniature components. Judging from the layout and the lack of a solder-mask, it was part of a small hand-assembled series. At the left are three (white) integrated circuits (ICs) that were probably made by RCA. At the bottom right is a coaxial cable that connects the expansion unit to the basic receiver.

Soviet equivalent
In the 1970s, the Soviet Union (USSR) introduced its own surveillance detection receiver, which was also body-worn and was able to detect a wide range of nearby radio signals, in particular those in the 150 and 400 MHz bands.

The image on the right shows the Russian device, which was known as Kopchik (Копчик).

 More information
Kopchik receiver with remote control unit, antenna and speaker

Known serial numbers
  • C553
    Mark II
    Colour photograph of a device dated 19 July 1979 [6]
  • C969
    Mark I
    Stasi report about KGB-confiscated SRR-100 [2]
  • Year
  • Organisation
    CIA, CIC
  • Design
    OC, OTS [4]
  • Manufacturer
    Motorola 1
  • Purpose
    Surveillance detection
  • Principle
    Single-conversion superheterodyne
  • Band
    VHF-M, (4 metre band)
  • Frequency
    101.8 - 103.4 MHz
  • Modulation
  • Channels
    1 (crystal-based)
  • Spacing
    50 kHz
  • Sensitivity
    0.16µV @ 10dB S/N, 0.3µV @ 20dB S/N
  • AFC
    at 0.2µV input
  • Deviation
    7 - 10 kHz
  • IF
    17.9 MHz (with crystal filter)
  • Response
    420 - 1250 Hz ±3dB
  • Output
    100 mW into inductive loop
  • Earphone
    Phonak wireless inductive earpiece
  • Antenna
    Shared with inductive loop
  • Security
    Speech scrambling (inversion) around 3050 Hz ±20Hz
  • Range
    500 mA (against 100 mW transmitter)
  • Battery
    2 x RM-625 mercury cell @ 1.35V (connected in parallel)
  • Current
    2.5 - 60 mA (depending on AF volume)
  • Life
    3 - 10 hours
  • Dimensions
    96 x 54 x 12 mm
  • Weight
Mark II
  1. Unconfirmed, but very likely.

  • Purpose
    Wireless earpiece (hearing aid)
  • Type
  • Manufacturer
    Phonak (Switzerland)
  • Battery
    RM 212
  • Current
    500 µA
  • Dimensions
    Ø 12.5 x 18 mm
Known channels
  1. 102.95 MHz
  2. 103.00 MHz
  3. 103.05 MHz
  4. 103.15 MHz
  5. 103.25 MHz
  6. 103.35 MHz
  1. Unknown author, Photograph of CIA equipment found in Moscow
    Date unknown. 1

  2. MfS, Photographs of SRR-100 device
    MfS - HA II, Nr. 42925, BStU 0242-0243. 1

  3. Wired: Former CIA Chief of Disguise Breaks Down Cold War Spy Gadgets
    25 November 2020.

  4. Antonio & Jonna Mendez, The Moscow Rules
    ISBN 978-154173009-0 (2019) / ISBN 978-154176219-0 (2021).

  5. Detlev Vreisleben, personal correspondence
    May 2021.

  6. Louis Meulstee, SRR-100
    Wireless for the Warrior - Volume 4, Supplement chapter 220.
    Version 1.00, October 2019.

  7. Bundesbeauftragte für die Stasi-Unterlagen (BStU) 1
    Federal Commissioner for the Stasi-Records.

  8. MfS, Mitteilung 726/78 (in German language) 3
    Abteilung 26. Nr. 1939. 8 June 1978. 4 pages.

  9. Jan Bury (2012), Finding Needles in a Haystack:
    The Eastern Bloc's Counterintelligence Capabilities

    International Journal of Intelligence and Counterintelligence. Volume 25:4.
    29 August 2012. pp. 751-754.

  10. IPNtv, I am an American Diplomat
    YouTube, 27 May 2015.
  1. Document kindly supplied by Jörg Drobick.
  2. Full name: Bundesbeauftragte für die Unterlagen des Staatssicherheitsdienstes der ehemaligen Deutschen Demokratischen Republik (DDR) — Federal Commissioner for the Records of the State Security Service of the former German Democratic Republic (GDR) — officially abbreviated to BStU.
  3. Document obtained from BStU [7] and kindly supplied by Detlev Vreisleben [5].

Further information
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Crypto Museum. Created: Wednesday 18 January 2017. Last changed: Thursday, 09 March 2023 - 10:06 CET.
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