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Pan-European stay-behind radio field station

FS-5000, codenamed HARPOON, was a fully automatic digital spy radio field station, developed between 1985 and 1988 by AEG Telefunken in Ulm (Germany) for the pan-European message system of the European Stay-Behind Organisations (SBOs), by the public often identified as Gladio. 1 The field set was used for communication with a BS-5000 base station. The complete system is known as SY-5000. In the Netherlands the FS-5000 is also known as AZO-90.

The Field Station (FS) consists of a number of individual modules that can be combined in several ways in order to perform a variety of tasks. The image on the right shows a complete FS-5000 radio set with all modules installed.

The unit is powered by a set of two batteries at the front left, that are charged by a mains power supply and battery charger at the rear right. At the rear left is the actual transmitter with its automatic antenna tuner. The separate receiver is located at the front center, in between the batteries and the control/crypto unit (DSU).
Complete FS-5000 radio station

The system was developed by AEG Telefunken in 1985 [5] and gradually became operational in the following years. Judging from the date codes on the electronic components, most sets we've seen were built around 1988. In most countries it was rolled out in 1990 and 1991, just before nearly all European countries dismantled their stay-behind organisations (in or around 1992). It is currently believed that the FS-5000 uses the secret NATO-approved Aroflex/RACE cryptographic algorithm — developed by Philips Usfa around 1980 — for the encryption of its messages [11].

As each country had its own independent stay-behind operation, the FS-5000 (Harpoon) was sometimes given a different name. In The Netherlands, for example, it was known as AZO-90, which is the abbreviation of Automatische ZendOntvanger 1990 (Automatic Transceiver 1990).

The FS-5000 was designed exclusively for NATO Special Services [5] but was also supplied to the Special Forces of the German Army (Bundeswehr) in 1994 and to some intelligence services. In 1998 the FS-5000 was followed by the compatible HRM-7000, which was part of the HF-7000 family. The Terminal Crypto Unit, TCU 7000 XP, shows great resemblance to the DSU of the FS-5000, and its BS-7010 base station was sometimes used in combination with the FS-5000 [B].

  1. Gladio was the name of the Italian SBO. As it was the first SBO to become publicly known, 'Gladio' has become a generic name, and is often used by the public as a synonym for SBOs in general.  More

Complete FS-5000 radio station
Complete FS-5000 radio station
Complete FS-5000 radio station
The DSU of the FS-5000 (SR 5000M)
FS-5000 station with accessories
Close-up of the DSU when attached to the radio station
FS-5000 in suitcase
FS-5000 with DSU inside Samsonite attaché case
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Complete FS-5000 radio station
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Complete FS-5000 radio station
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Complete FS-5000 radio station
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The DSU of the FS-5000 (SR 5000M)
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FS-5000 station with accessories
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Close-up of the DSU when attached to the radio station
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FS-5000 in suitcase
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FS-5000 with DSU inside Samsonite attaché case

 History of the FS-5000

WARNING — Anyone with an FS-5000 in his or her collection, who wishes to use or demonstrate the device, MUST read the following notice. Inside the mains power supply unit (PSU) are a number of capacitors that are likely to explode after a number of years. It is important to replace all RIFA capacitors in the PSU before connecting the it to the mains again, even if it has worked before.  Learn more...
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Modular design
The FS-5000 has a highly modular design. It is beautifully designed with a keen eye for the smallest detail and was certainly state-of-the-art when it was developed in 1985. The system consists of a large number of units (modules) each of which consists of a purpose-built die-cast aluminium box with mil-spec PCBs inside. The various modules are shown in de drawing below:

Exploded view of the various modules of the FS-5000 stay-behind field station. Click any item for further information.
Battery Battery Receiver Antenna Tuner Transmitter Transmitter Toolkit PSU Charger DSU
FS-5000 modules - click any module for a detailed description

The reason for the modular design is that the various units had to be used in a variety of possible set-ups. The modules can be combined in various ways in order to create (partially) stand-alone solutions. Additional accessories, such as the H-bar, are provided to allow even more set-ups. A number of possible configurations is demonstrated below.

High-quality connectors are used between the units and some units could also be used stand-alone. The complete FS-5000 radio station consists roughly of the following units: To protect the units against water and other environmental impact, all units are completely sealed and water-tight connectors are used. The image on the right shows the fully assembled radio station that nicely fits a common briefcase.

Completely assembled FS-5000 radio station

Modules and parts
The FS-5000 consists of the following modules:

# Short Designator Description  
D DSU SR 5000 Digital Storage Unit (controller, crypto)  
R RX E 5000 Receiver  
T TX S 5000 Transmitter  
A ATU - Automatic Antenna Tuner  
C Charger - Battery Charger/Inverter  
M PSU - Mains Power Supply Unit 110-240V AC  
B Battery BA 5000 Rechargeable Battery (2x)  
H H-bar - Versatile stand-alone adapter  
F Fast - Fast discharger (active dummy load)  
S Slow - Slow discharger (2x, part of toolkit)  
X X-unit - Test box for Transmitter and DSU  
- Cable VK 5000 DSU extension cable (1.5m)  
- Tools - Toolkit with accessories  
- Brackets - Various mounting brackets (locks)  

Click any of the items above, or scroll down this page, for a brief description of each item. Alternatively, you may click any of the thumbnails below to go straight to a page with additional information about the item.

Digital Storage Unit (DSU)
Receiver (RX)
Transceiver (TX)
Automatic Antenna Tuner
Battery charger, power inverter and supervisor
Power Supply Unit (PSU)
Rechargeable NiCd batteries
Non-rechargeable battery
Test Device (part of toolkit)
Fast discharger
Digital Storage Unit (DSU)
The Digital Storage Unit (DSU) was the heart of the FS-5000 radio station. Without the DSU, the set can not be operated. It contains the user interface, the frequency adjustment, the Real Time Clock (RTC) and the cryptographic engine.

The DSU is fitted at the bottom right and is connected to the receiver. It can also be detached and operated via an extension cable.

 More information
Click here for detailed information about the DSU

The Receiver is a separate unit that is connected to the transmitter and to the DSU. It gets its power and antenna signal from the transmitter and is suitable for frequencies between 500 KHz and 30 MHz.

The receiver can also be used stand-alone in case of an emergency (e.g. when other modules have broken down). In that case an earphone can be connected to the front panel for the reception of spoken messages or morse code signals.

 More information
Click here for detailed information about the receiver (RX)

The transmitter is normally stacked below the Automatic Antenna Tuner and is suitable for frequencies between 2 and 30 MHz in steps of 1 KHz, under control of the DSU and the receiver.

The transmitter delivers an output power of 25W and is suitable for the transmission of QPSK signals. In a full FS-5000 station is links the other modules together.

 More information
Click here for detailed information about the transmitter

Automatic Antenna Tuner
An automatic antenna tuner was used in combination with the transmitter, to allow the FS-5000 to be operated by non-technical users. A 15-meter wire was sufficient to obtain good results on all frequency bands.

 More information
Click here for detailed information about the antenna tuner

Battery charger
The battery charger allows the batteries to be charged either in situ (whilst installed in the radio station) or separate from the set (stand alone). It takes its power from the PSU that is normally mounted on top of it.

The unit also contains a power inverter that allows an external 12V source to be used instead of the PSU.

 More information
Click here for detailed information about the charger

Mains Power Supply
The PSU is a highly compact and efficient Switched Mode Power Supply (SMPS) that is mounted on top of the Battery Charger. It accepts any AC voltage between 110 and 240V.

 More information
Click here for detailed information about the PSU

The FS-5000 comes with two heavy-duty rechargeable NiCd batteries that allows the radio station to be operated away from the mains (e.g. in the field).

Special tools are provided for extending the battery's life, by charging and discharging them properly.

 More information
Click here for detailed information about the batteries

The FS-5000 comes with a number of smaller accessories that are stored inside a clever slim-line grey plastic box that can be installed as part of the complete radio station, on top of the Digital Storage Unit (DSU) at the front right. It is held in place by a retaining clip on the PSU.

 More information
Click here for detailed information about the toolkit

The H-Bar is a versatile extension to the FS-5000 radio station. It is a junction box in the form of a narrow plastic bar with various connectors at either side to allow a different arrangement of the modules.

The H-Bar can be used for stand-alone battery charging as well as for stand-alone usage of the receiver.
Click here for detailed information about the toolkit

Fast discharger
An active dummy load with heatsink is provided for fast battery discharge. It is used as part of a recovery process that allows batteries suffering from the so-called Memory Effect to be reconditioned.

When connected to a battery, a green LED indicates that discharge is in progress.

 More information
Click here for detailed information about the fast discharger

Test unit (X)
The X-unit is part of the Toolkit. It has connectors at three sides and and offers three test functions.

It can be used to test the output power of the transmitter, but can also connect the transmitter directly to the antenna in case the Antenna Tuner is broken. It can also be used to test the DSU's interface.

 More information
Click here for detailed information about the X-unit

The following items are options and were not supplied with all FS-5000 units. Some items were added for different users, such as Special Forces (SF). Some items below have been reported by our readers. If you know of any other options that are not listed here, please contact us.

Extension cable
It was possible to use an (optional) extension cable between the receiver and the DSU. The extension cable has purpose-built connectors at both ends and is approx. 1.5 meters long.

Special locking mechanisms are provided for a secure connection in the (battle)field. The cable allows a more convenient operation of the DSU.

 More information
Click here for detailed information about the extension cable

Alternative battery
The battery shown here was developed for the later HRM-7000 manpack radio. It uses LiMnO2 technology and is therefore not rechargeable, which means that it has to be discarded (or recycled) after use.

In 1994 it was adapted for use in combination with the FS-5000M, for use by Special Forces. This resulted in a rather clumsy solution.

 More information
Click here for detailed information about the BPU-7000 battery

Special battery cable
In order to use the BPU-7000 battery (above) with the FS-5000, the special adapter cable shown on right was available.

The battery was mounted upside-down on top of the ATU and the cable was used to connect it to the leftmost battery socket on the transmitter.

 More information
Click here for detailed information about the BPU-7000 battery

Double size battery
This double-size battery was designed as an alternative for the two standard NiCd batteries. It made use of LiMnO2 technology and was therefore not rechargeable.

The battery shown here was a prototype. It is not clear whether it was ever produced in large quantities.

 More information
Click here for detailed information about the double-size battery

External DSU power
A special tool was available to allow the DSU to be used off-line when batteries were dead (or running low). It takes the place of the two 3.5V batteries inside the DSU and has wires that can be connected to an external DC power source.

The tool is shown in the image on the right. It was supplied only for use by stay-behind personnel. Thanks to Jim Meyer [1] for supplying this image.

 More information

The V-Bar was a shorter version of the H-Bar. Like the H-Bar it could be used to charge the two standard batteries in combination with the PSU. The V-Bar was not suitable for stand-alone use of the transmitter.

 More information
Click to see more

Alternative configurations
In the description above the complete FS-5000 station is shown with all modules installed at their default position. It was however possible to group some of the modules together in a different manner, so that the set could be used for more than one application. Below is a description of the currently known configurations. If you know of another one, please let us know.

Full station
The image on the right shows a complete and fully assembled FS-5000 radio station, with all modules in their default position.

In this configuration, the radio can be powered either by the PSU or by the batteries. As the PSU can generate spurious (radio) signals, it may interfere with the reception of weak signals. For this reason battery operation was recommended.

When turned off, the PSU can be used to charge the batteries, simply by pressing a button.
Complete FS-5000 radio station

Briefcase operation
Depending on the required task, the FS-5000 was sometimes supplied in a rugged military suitcase or in a standard attaché briefcase, such as the Samsonite briefcase shown on the right.

The size of the complete radio station is designed in such a way that it fits nicely inside a standard briefcase, leaving enough room for the ancillaries and any support documents. The unit connects to the mains power and can be operated with minimum of fuzz.
FS-5000 with DSU inside Samsonite attaché case

Detached DSU
In normal operation, the DSU is located to the right of the receiver, so that the connectors of the two devices mate. This is how the FS-5000 was designed in 1985. A later extension cable, called VK-50000, allows the DSU to be used as a console. It was probably introduced in 1992.

The image on the right shows the DSU detached from the main station and connected via the VK-5000 cable.

 More information
FS-5000 with detached DSU

Stand-alone DSU
The DSU can be used stand-alone in which case it is powered by the internal backup batteries. This allows messages to be entered and read off-line (i.e. being away from the radio station).

Messages are retained in the internal memory of the DSU and it is even possible to have scheduled transmissions and receptions.

 More information
Stand-alone use of the DSU
Stand-alone receiver
In some countries it was possible to use the receiver stand-alone in case of an emergency (e.g. when the other units failed). The H-bar was then used to connect the receiver to a single battery and the small control panel on the side of the receiver was used to adjust the frequency.

Please note that this mode of operation was not possible with the FS-5000M that was used in Germany. It can be modified however.

 More information
Receiver-only operation

Battery charging station
The batteries could be charged independently from the radio station. This was done by using the power supply/charger in combination with the H-bar, allowing the two batteries to be connected directly to the PSU.

The image on the right shows two batteries connected to the PSU via the H-bar. The black wire on the right is connected to the mains.

 More information
Charging batteries

Battery operation
By default the radio station was powered by the two NiCd batteries. In some countries it was not allowed to leave the PSU connected to the transmitter, so the transmitter was shielded-off at that side.

The image on the right shows the two batteries and the receiver connected to the transmitter. The DSU is connected to the receiver at the front right.
Battery operation

Operate and charge
The image on the right shows the FS-5000 in battery-operated configuration, whilst the PSU is used to charge an additional set of batteries.

This was the main configuration in a number of countries that used the FS-5000.
Operate and charge simultaneously

Manpack solution
For application in the (battle)field, it was possible to use battery-operation in combination with a detached DSU. It allows the radio station to be installed in a more convenient location or in a back-pack, whilst the DSU is hand-held.

The image on the right shows the portable self-contained radio station with detached DSU.
Battery operation and detached DSU

For the Special Forces of the German Army, the so-called Fernspäher, the BPU-7000 battery of the later HRM-7000 man­pack radio was adapted for use with the FS-5000, as an alternative for the increasingly deteriorating standard BA-5001 battery.

The result is the improvised and rather clumsy solution shown here, in which the BPU-7000 battery is connected with an adapter cable that easily comes off.

 More information
Special Forces setup

All FS-5000 sets were supplied by the factory in a large carton box, with each module (or set of modules) packed inside a sealed water tight green fiber container. The total set consisted of 8 containers: 4 small ones and 4 double-size ones. They were packed as two stacks of 3 high.

The image on the right shows the contents of the carton. There were 4 large and 4 smaller containers, each holding one or more modules. The modules themselves are each packed in plastic, in order to protect them when stored for longer periods of time. A small container with the DSU is missing in the picture.

Each container has a label with the serial number and a letter denoting the module that is stored inside it. If more than one module is packed inside a container, multiple labels are present. The meaning of the letters is listed above.
FS-5000 packed for long-term storage

If the FS-5000 was going to be stored for a long period of time, e.g. as part of a cache, the set had to be taken apart and each module had to be stored in its container again. The batteries had to be removed from the DSU. The containers were then sealed with water-proof adhesive tape.

In the period following WWII, the organisation of stay-behind networks in Europe was extremely scattered. Each country had its own stay-behind organisation and used a variety of spy radio sets, ranging from simple valve-based analogue radios to fully digital rigs with built-in encryption.

In the early 1980s, the ACC (Allied Clandestine Committee), attached to NATO headquarters SHAPE in Mons (Belgium), decided to develop a pan-European communication system for all stay-behind organisations in Europe, including non-NATO countries such as Sweden and Switzerland.

In the early days of the Cold War, it was believed that the governments of most European countries would make their way to England when their countries were invaded by the Soviets. For this reason, some Harpoon FS-5000 sets were installed there. Later, when nuclear weapons became available to the USSR, the general consent was that the European goverments would escape to the US. Arrangments were therefore made, to have some FS-5000 radio sets in the US as well. These sets were delivered to the American National Security Agency (NSA). The FS-5000 was suitable for this, as it was specified for a range of 6000 km!

As it was impossible for the (secret) stay-behind organisations to deal directly with Telefunken, the German intelligence service (BND) acted as a facade and ordered 854 units from Telefunken, for a total amount of 130 million German Marks (equivalent to 65 million Euros) [4]. The first sets were delivered in 1988, and by March 1991 all FS-5000 radio sets had been delivered to the various countries [6]. Stay-behind personnel was trained on the new radio and the first long-range field tests (LOR) were successfully completed in 1990 [6 p.139]. Shortly afterwards, after a series of scandals, most European countries decided to dismantle their stay-behind organisation.

By the end of 1992, Gladio had become history. All field agents had been detached and the Harpoon radio sets (FS-5000) were collected and stored. As the cost of development of the FS-5000 was quite substantial, a new destination was sought for some of the equipment.

Bad quality
In 1991, the USA decided to give the FS-5000 a real-life field test, by using it in the First Gulf War. The American Special Forces (SF) however, had trouble operating the radio and concluded that it was impractical and unsuitable for SF use. They were probably right, as the radio set was developed for a total different purpose. In 2000 some of these American FS-5000 units accidently appeared on the surplus market, albeit without the DSU. When the mistake was discovered, the remaining sets were quickly withdrawn, but a mere 22 units had already found a new home.

Whether or not the above story is correct, remains to be seen. It is very unlikely that the American SF or the CIA would use former stay-behind equipment in a war theatre, whilst they had plently of alternative equipment available from US sources. It is far more likely that the story of 'bad radios' was invented to masquerade the accidental and unintended release of FS-5000 units in the US.

Around 1993, Germany decided to give the remaining FS-5000 sets a new lease of life, by using them as a gap-fill solution for their Special Forces (Fernspäher). After a few modifications to the radio set (FS-5000M), it was successfully used for many years during training sessions, until it was replaced by the newer HF-7000 series. In 2012, a number of these FS-5000M sets appeared on the German surplus market, this time complete with the Digital Storage Unit (DSU).

VSB and SSB Modulation
For the transmission of message bursts, the transmitter uses a very sophisticated modulation technique, called Vestigial Side Band Modulation (VSB or C1D), compatible with ECHOTEL. This allows the transmitter to send a message over a channel with an extremely narrow bandwidth at a speed of 2000 baud. As a result, sending a 55 character message takes no more than 0.8 sec. [A], making Direction Finding (DF) practically impossible! Although this technique was already used in 1967 for (computer) modem signals, it was relatively new for use on HF-radio in 1985. The principle is explained in a number of US patents that were filed around this time [7] [8] [9].

Communication path between BS-5000 base station and FS-5000 field station

The receiver uses Single Side Band (SSB or J2B) with single-channel FSK for the reception of data messages at a speed of 75 baud. As the receiver uses a different type of modulation and a different baud rate, it is not compatible with the transmitter. It is therefore not possible to communicate directly between two FS-5000 field stations. Communication was only possible between an FS-5000 and a BS-5000 (or BS-7010) base station.

The block diagram above shows roughly how the various components of the FS-5000 are used together. All frequencies and tuning signals are derived from the receiver where they are generated by a synthesizer running on a 10MHz TCXO. The DSU controls all units and set the RX and TX frequencies. The antenna signal for the receiver is normally supplied by the Antenna Tuner (ATU) through the transmitter. Only when the alternative telescopic antenna is used, a separate pre-amplifier is activated. More details on the relevant pages. A good explanation of the mathematical backgrounds of VSB is given by Phil Schniter on the Connexions website [B].

  1. Feldstation FS-5000M, Technisches Handbuch, Teil 1, Beschreibung
    Field Station FS-5000, Technical Manual, Part 1, Description (German).
    March 1994.

  2. Feldstation FS-5000M, Technisches Handbuch, Teil 2, Bedienungsanleiting
    Field Station FS-5000, Technical Manual, Part 2, User Manual (German).
    March 1994.
  1. Helmut 'Jim' Meyer, HS0ZHK, My way to Ham - Radio and beyond
    Website QRZ.COM. Personal correspondence. Retrieved June 2008.

  2. Louis Meulstee, Wireless for the Warrior, volume 4
    ISBN 0952063-36-0, September 2004

  3. Dr. D. Engelen, De Nederlandse stay behind-organisatie in de koude oorlog 1945-1992
    Ministerie van Algemene Zaken, Ministerie van Defensie & Rijksarchiefdienst/PIVOT
    The Netherlands, National Archives, Institutional Investigation, 2005. (Dutch)

  4. Daniele Ganser, NATO's secret Armies: Operation Gladio and Terrorism in Western Europe
    ISBN 978-071465607-6, 2005

  5. Telefunken Racoms, History
    Timeline -> 1985, SY5000 adaptive HF system to NATO special services.
    Telefunken website. Retrieved May 2009.

  6. Geschiedenis van de Sectie Algemene Zaken, Hoofdstuk VIII,
    Van Stroomlijning tot Opheffing

    History of the Section General Affairs, Chapter 8, From Streamlining to Dissolution. (Dutch) Describing the period May 1987 - January 1994. Dutch National Archives. Top Secret. Partly declassified and released in 2007 under the FOI Act.

  7. United States patent 4,780,884, Suppressed Double-Sideband Communication System
    Filed 13 April 1987. Approved 25 October 1988. Previously filed as 741,026 (3 June 1985) and 835,265 (3 March 1986), both abandonned. Retrieved April 2012.

  8. United States Patent 4,730,345, Vestigial Sideband Signal Decoder
    Filed 4 April 1986. Approved 8 March 1988. Retrieved April 2012.

  9. United States Patent 5,663,773, Demodulator for a Complex-Value VSB Signal
    Filed 20 November 1995 on behalf of ANT Nachrichtentechnik GmbH, Backnang (Germany). Approved 2 September 1997. Retrieved April 2012.

  10. Phil Schniter, Mathematical backgrounds of Vestigial Sideband Modulation (VSB)
    Retrieved April 2013.

  11. Operators Manual for PC-KAYSAT-KAYNARD-RACE Software
    Instructions for the NL-developed message and encryption handling software (English).
    May 1991. SECRET.
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