US satellite spy radio set
- wanted item
RS-804 was an agent radio set,
also known as a spy radio set,
with built-in data encryption, develop in the early 1980s
by or for the US
Central Intelligence Agency (CIA), for use
in Cold War espionage operations.
It allowed an agent, operating in a hostile country, to send high-speed (burst)
messages via a UHF satellite link. One device is known to have been captured
in 1983 by the Russian KGB.
It is also believed to have been used by the CIA in Cuba
during the 1980s .
The RS-804 is believed to be one of the first spy radio sets that used
satellite communications instead of short-wave transmissions (SW).
Unlike with SW signals, a radio signal to a satellite is very difficult
to intercept and trace,
as the waves are 'beamed' straight up rather than all around.
Considering the era in which the set was made, it is extremely small.
Due to the modular design, it could be concealed easily and could be
used in a variety of configurations.
As the tickest part is just 19 mm high, it could easily be hidden inside a piece
of furniture or behind the false bottom of a briefcase, as illustrated
further down this page.
The image on the right shows the complete self-contained RS-804
radio set that was confiscated
by the Russian iKGB
on 7 March 1983, when they compromised the US Embassy's First Secretary
Richard Osborn whilst the latter was making an illicit transmission from a park in
Moscow. The radio set consists of three larger modules plus some kind
of connector that is fitted at the right.
The transmitter operates in the UHF band around 300 MHz with an
RF output power of 10 Watts, and is suitable for communication via the
US MARISAT and FLTSATCOM satellites. A text based message with a
maximum length of 1579 characters can be encrypted and stored in
the CK-42 crypto unit at the bottom left.
When transmitting, the message is sent as a high-speed burst
that lasts 4 to 21 seconds, making it even more difficult
for the authorities to locate the signal.
The diagram above shows how the messages are sent. The agent sends his
messages directly via a satellite link to headquarters (HQ) in the US.
New instructions for the agent are send by HQ via the short-wave
one-way voice link
as OTP-encrypted messages,
for which separate OTP keys were provided.
A variant for
short-range agent communications (SRAC)
is known as CDS-501.
The diagram below shows a complete RS-804 setup as it was usually
built inside the hidden bottom of a common briefcase. The entire
assembly is no larger than 31 x 31 cm, which is the size of the
circular polarized antenna on which the other parts are mounted.
It is just 2 cm thick.
At the bottom right are the three basic modules:
the RT-804 transmitter,
the CK-42 encryption unit
and the BS-804A battery pack
with built-in PSU/charger. The latter also hold the
controls (SEND/OFF/INPUT) and a socket for a
remote control unit that is inserted at the right top.
The complete RS-804 set (with the exception of the antenna)
measures just 198 x 168 x 19 mm and weights 2.3 kg.
It consists of the following parts:
Operation of the RS-804 set was extremely simple, as indicated by the
small instruction label that is fitted on top of the PSU. It shows how
to enter a message and how to send it. It is likely that it could be
operated by an unskilled user after just a short instruction or training.
- Switch to INPUT 1
- With stylus depress INPUT key 2
- Enter 19 character variable 3
- Enter twelve ↓
- Enter message number and an X
- Enter text
- Enter one ≡
- Enter four ↓
Switch to send,1 position antenna,|
depress ACTIVATE.4 After 30 seconds
depress INTERROGATE.4 Observe MSG and
ACT lamps 5 for positive indication.
3-position rotary selector on the PSU.
On the keypad of the CK-42 crypto unit.
This is the message key that was supplied on a separate sheet.
On the transmitter (aside the antenna socket), or on the remote control unit.
We assume that these indicator lamps were on the wired remote control,
along with the ACTIVATE button.
During the Cold War,
the RS-804 was used by US operatives in many countries
that were regarded by the US as 'hostile', such as Cuba, East-Germany (DDR),
Poland and the Soviet Union (USSR). The problem with the USSR however,
was that Moscow was at the very outer limit of the MARISAT satellite's
footprint. In June 1981, tests had shown that the RS-804 could not be used
reliably from Moscow as the antenna was probably too small.
The sets were then returned to the US .
The RS-804 set was improved by CIA technicians and about two years later
it was returned to the Moscow station for testing.
Towards the end of 1982, the Russian
secret service KGB began to notice and intercept burst transmissions to
US MARISAT satellites, which were believed to originate from
parks and forests in the USSR .
Meanwhile, Richard Osborne, a diplomat in his mid-40s, had been placed at the
US Embassy in August 1982 and was now living in Moscow with his wife
and two daughters aged 6 an 8. He was assigned as
Economics Section's First Secretary.
On 7 March 1983, Osborne was going to test the improved device,
using a family walk as cover .
He went to an open spot in Moscow's Poklonnaya Gora Park
and setup the device, concealed inside his briefcase,
in such a way that it could 'see' the satellite.
He then initiated a transmission.
Unknown to him however, was that he and his family were constantly being
observed by a KGB surveillance party who had reason to believe
that Osborne might be behind some of the illicit transmissions.
As soon as the surveillance party received confirmation
that a transmission was indeed taking place from his briefcase,
they arrested him. He was caught 'red handed'.
In his briefcase the KGB found the sophisticated RS-804
satellite burst transmitter hidden behind a false bottom.
It was set to 311.15 MHz in the UHF band: the uplink
to the MARISAT satellite.
The KGB also found notes in his briefcase that were written
on special water soluble paper. For the Russians this was the final proof
that Osborne was indeed a spy and not a diplomat.
After his arrest, Osborne (who had diplomatic immunity) was released and
declared persona non grata for 'actions incompatible with diplomatic status'.
He was then expelled from the Soviet Union .
The sophisticated minature satellite radio set was thoroughly investigated
and photographed by the KGB, who codenamed the device FOBOS (ФОБОС),
and the information was shared with friendly services
in countries like Cuba, Poland and the DDR (East Germany).
More RS-804 units were later captured in Afghanistan — in 1988 —
during the Russian War Against Afghanistan.
The image on the right shows an original colour photograph of
Osborne's briefcase, as taken by the Sovjet
KGB and shared in 1983 with the
East-German state security service (MfS, or Stasi)
The photograph clearly shows how small the RS-804 actually is when
compared to the size of the (regular) briefcase itself. It is completely
hidden behind the lining of the top lid of the briefcase.
Many thanks to Detlev Vreisleben for bringing this photograph to our
The RS-804 has a modular construction, which allows the radio, or parts
of it, to be used in a variety of configurations and concealments. As the
thickest part measures only 19 mm, it is ideal for concealment inside a
briefcase or a piece of furniture. Note that some parts are also used with
the similar line-of-sight CDS-501 radio set.
The modules are described in more detail below.
The transmitter is L-shaped and measures approx. 100 x 188 mm.
It has two sockets for connection to the other modules: one in
the cut-out section at the bottom left that accepts the
CK-42 crypto unit,
and one at the top right that connects it to the
Furthermore it has an antenna socket at the top.
The device is controlled from the PSU.
The transmitter operates in the 300 MHz UHF band and delivers an RF output
of 10W. It is suitable for use with the American MARISAT and FLTSATCOM
satellites. The device that was captured by the KGB was preset to
311.15 MHz; the earth station uplink of the MARISAT satellite.
The following FLTSATCOM frequencies (fleet satellite communication)
are known to have been used by the CIA for
data communication, all in narrowband FM/data :
- 243.000 - 244.000 MHz
- 251.000 - 269.000 MHz
- 292.000 - 317.000 MHz
2. Encryption device
Apart from the remote interface, the crypto unit is the smallest
part of the set. It measures 100 x 68 x 18 mm and weights just 160 grams.
It is fitted inside the L-shaped cutout of the transmitter and
connects to it via a large socket at the top. It can be detached easily,
allowing it to be loaded with data externally. The CK-42 is labelled as a
Confidential COMSEC Controlled Item.
The CK-42 allows messages with a length of up to 1579 characters
to be stored in its internal memory,
encrypted with a 19 character encryption key that was
supplied on a separate sheet. It is likely that a new key was used for
each message. The crypto unit also controls the transmission of the
messages, which are as sent as high-speed bursts
that last 4 to 21 seconds.
Messages are entered on the small keypad on top of the unit.
It consists of 32 buttons, arranged as 4 rows by 8 columns, plus a separate
INPUT button at the top. Because of the small size of the device, the buttons
can only be operated with a sharp object like a stylus.
The encryption algorithm that is used by the CK-42 is currently unknown.
The same crypto unit was also used with the
CDS-501 line-of-sight (LoS)
radio set, that was used by the CIA for
short-range agent communications (SRAC).
➤ More information
The PSU is the longest part of the set and measures approx. 69 x 180 mm.
It holds a set of rechargable NiCd batteries plus a mains AC power supply
unit (PSU) that is also used as a battery charger. This means that the set
could be operated either from the batteries or the AC mains.
The PSU is connected to the transmitter via the socket at the top left.
The PSU also holds the main MODE selector: a 3-position rotary switch
that can be set to SEND, OFF or INPUT. At the top right is a socket for
a remote control unit, allowing the set to be operated whilst it is
concealed. The PSU shown here is configured for the 220V AC mains,
as indicated by a small tag at the top edge.
The PSU also holds a small CHARGE lamp at the top, that is lit when the
unit is connected to the AC mains. It indicates that the NiCd batteries
are being charged. At the lower part of the PSU is a label with the
suggesting that the set was extremely easy to operate.
4. Remote control
A small remote control interface is connected to the socket at the top
right of the PSU. It allows an external (wired) activation switch
to be connected to the set. The switch could be mounted elsewhere in the
or on briefcase, e.g. in the handle, so that it could be activated covertly.
The antenna is the largest part, but also the thinnest. It measures
310 x 310 mm and has rounded corners. Furthermore it acts as the base
on which the other modules are mounted. The antenna is circular
polarized and is fed via the large filter at the top.
The antenna consists of laminated copper and was probably made
of double sided PCB material that was painted black.
- Jan Bury, Project Kalina: The Lotos Operation Conundrum
Cryptologia 36:2, April 2012, pp. 119-128.
- Archives of the Polish Institute of National Remembrance (IPN)
Information on the FOBOS agent radio communications device from the First
Secretary of the US Embassy in Moscow R. Osborne on 7 March 1983.
Warsaw 1983. 2
Available at the Archives of the Polish Insitute of National Remembrance.
File # IPN BU 01304/953.
- Detlev Vreisleben, Personal correspondence
- KGB, Photographs of RT-804 spy radio set
March 1983. Photographs from BStU, kindly supplied by . 1
- David E. Hoffman, The Billion Dollar Spy: A True Story of Cold War Espionage
Moscow station to headquarters, June 26 1981, 261440Z. Page 311, pt. 20.
- John F. Burns, Moscow ousts a US Diplomat, Calling Him a Spy
The New York Times, 11 March 1983.
- New FFR, Communauté Underground, Old School → Ecoute (espionnage) radio
Website: Les Forums Sécurité (French). Retrieved November 2015.
- Bundesbeauftragte für die Stasi-Unterlagen (BStU) 3
Federal Commissioner for the Stasi-Records.
- Excerpt of KGB report, sent in 1983 to the MfS (Stasi)
MfS 1983 .
Obtained via Detlev Vreisleben, September 2018 .
In March 1983, the set was photographed by the KGB following the
arrest of Richard Osborne. The information was shared with friendly
services in Cuba, Poland and the DDR. The photographs that were formerly
part of the Stasi archives in the DDR, are now maintained by the BStU
in Germany (BRD) and are freely accessible. Many thanks to Detlev
Vreisleben  for supplying these photographs.
Original text: Informacja dotyczaca agenturalnej aparatury
lacznosci radiowej 'FOBOS' zatrzymanej u pierwszego sekretarza ambasady
USA w Moskwie R. Osborne'a w dniu 07.03.1983 r. Warszawa 1983.
Full name: Bundesbeauftragte für die Unterlagen des Staatssicherheitsdienstes
der ehemaligen Deutschen Demokratischen Republik
Federal Commissioner for the Records of the
State Security Service
of the former German Democratic Republic (GDR) —
officially abbreviated to BStU.
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© Crypto Museum. Created: Saturday 05 September 2015. Last changed: Wednesday, 02 September 2020 - 15:44 CET.