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Harris RF-5811
Secure voice data unit

RF-5811 is an encryption/decryption device for voice and data signals, developed around 1997 by Harris (now: L3Harris) in Rochester (NY, USA). It was commonly supplied as part of a 400 Watt HF radio station, and used over narrowband HF channels. Intended for non-Type 1 applications, it allows 3 unique algorithms to be selected. The unit is also known as NSN 5820-01-469-8797.

The device has interfaces for Ethernet, RS-232 and fixed-base and handset audio, a versatile processor platform, an LPC-10 vocoder at 2400 baud, a Harris CITADEL crypto­graphic engine, a single-tone HF narrowband modem with a speed of 75 - 4800 baud and a data-directed equalizer that minimises the effects of multi-path delays.

The device is housed in a rugged (grey) die-cast aluminium enclosure, and was part of the Harris RF-5800 Falcon II family of devices. All controls, a 12-button keypad and a backlit Liquid Crystal Display (LCD), are located at the front panel.
Harris RF-5811 secure voice and data unit

Also at the front is a standard U-229 AUDIO socket for connection of a handset, headset or fixed audio unit, a 10-pin NF10 socket for connection of a key FILL device and/or the Crypto Ignition Key (CIK), and a 19-pin DATA socket. The 4-pin power socket, one further 19-pin DATA socket, a 10base 2 thin ethernet socket (BNC) and a GROUND terminal, are all located at the rear panel.

The RF-5811 was registered in the NSN database in 30 November 1999 [4] 1 and was first tested in an operational context in 2003 and 2004 with the Standby High-Readiness Brigade (SHIRBRIG) of the United Nations (UN), which existed from 1 January 2000 to 30 June 2009 [1][2]. It was used to replace the
's existing HC-3300 (telephone) and HC-4220 (fax) encryptors, and provide the participating SHIRBRIG countries with a common – compatible – interface for sending secure voice and data traffic over HF radios and satellites. Other uses of the RF-5811 are currently unknown.

  1. The unit shown here has a manufacturing code of week 23 1997, but this conflicts with the date codes on some of the chips, which are from 1998 and 2000. It is therefore likely that the design was modified one or more times before the first units were delivered in 2000.

Harris RF-5811 secure voice and data unit Front panel Rear pannel Keypad and display Key loading MODE selector BLACK data socket
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Harris RF-5811 secure voice and data unit
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Front panel
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Rear pannel
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Keypad and display
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Key loading MODE selector
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BLACK data socket

The diagram below provides a quick overview of the controls and connections on the body of the RF-5811. Power, the local network and any local (parallel or serial) data devices (i.e. the RED side) are connected to the sockets at the rear. The radio should be connected to the DATA socket on the front panel, whilst a handset (or equivalent) is connected to the 6-pin U-229 AUDIO socket.

SHIRBRIG was a Danish-led initiative, associated with the United Nations (UN) [1], aimed to create a standby force ready for peacekeeping, formed as a result of the Rwandan genocide of 1994 [3]. It had permanent headquarters in Høvelte (Denmark) and was initially led by Major General Patrick Cammaert of the Royal Netherlands Marine Corps [1]. The brigade was active from 1 January 2000 to 30 June 2009. During its existence, the following countries participated in the brigade:

  • Argentina
  • Austria
  • Canada
  • Denmark
  • Finland
  • Italy
  • Netherlands
  • Norway
  • Poland
  • Romania
  • Spain
  • Sweden
 Read the SHIRBRIG Lessons Leared Report of 2009

The RF-5811 is housed in a die-cast aluminium enclosure that measures 250 x 183 x 80 mm and weights 2116 grams. The centre part of the front panel can be removed. The interior is accessible from the rear, and requires the four black screws at the corners of the rear panel to be loosened.

After loosening these screws, the rear panel – that is sealed with a watertight gasket – can be removed. Mounted to the inside of the rear panel is a PCB on which all rear connections are mounted. This PCB is connected to the front panel via a 50-wire high-density ribbon cable.

On the board are the two transformers for the 10base2 Ethernet interface, and some filtering for the data lines. Also on this board is a Lithium battery that is held in place by a metal bracket. This battery is responsible for retaining the KEKs and TEKs in the unit's internal CMOS memory.
Rear panel opened

Also connected to the front panel – which acts as a central hub – is a removable tray that contains the actual circuitry. It is divided in two sections – marked compartment A and B – and is slotted into the front panel by means of two wide multi-pin connectors; one for each compartment.

The tray is held in place by two recessed screws that are located near the short sides. After loosening these screws, the entire tray can be pulled out towards the rear. Note that before doing this, it is advisable to removed the rear panel first, by disconnecting the 50-pin ribbon cable.

The tray is mounted upside down (when looking into the rear end of the device. Inside it are four PCBs – two for each compartment – separated by a metal panel. There are no direct connections between the two compartments. Side-A holds a PCB with a Motorola MC68331 processor, an Altera Flex FPGA and an LSI-chip marked Citadel.

It is mounted on top of another large PCB with the same processor and FPGA, plus a TMS-320 Digital Signal Processor (DSP) made by Texas Instruments. This DSP is probably used for the implementation of the LPC-10 speech processor.
Compartment B side

LPC-10 is a vocoder that allows digitised speech to be transmitted through a narrowband channel (of 800 to 2400 bits per second), at the expense of speaker recognition. The B-side of the tray holds two further PCBs: one with another TMS320 DSP, and one with a Motorola XPC860 multi-I/O controller with built-in 32-bit processor. The latter provides the DATA and ETHERNET ports.

Rear panel opened Rear panel removed Rear panel with PCB PCB inside rear panel Rear PCB detail Lithium backup battery on rear PCB Removable tray with compartment A and B Removing the compartment tray
Compartment A side Compartment A, upper PCB Compartment A, lower PCB Compartment B side PCBs removed from compartment B Compartment B, upper PCB (daughter card) Compartment B, lower PCB (main board) Compartment B, main board detail
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Rear panel opened
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Rear panel removed
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Rear panel with PCB
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PCB inside rear panel
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Rear PCB detail
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Lithium backup battery on rear PCB
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Removable tray with compartment A and B
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Removing the compartment tray
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Compartment A side
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Compartment A, upper PCB
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Compartment A, lower PCB
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Compartment B side
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PCBs removed from compartment B
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Compartment B, upper PCB (daughter card)
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Compartment B, lower PCB (main board)
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Compartment B, main board detail

Help required
At present, no further information about the Harris RF-5811 is available. We are currently looking for brochures, operating manuals, technical documentation and further examples of its use in an operational context. If you can supply any of these, please contact us.

  1. Harris Citadel Cryptographic Engine, product leaflet
    DS-206G. Harris Corporation November 2015.
  1. Wikipedia, Standby High-Readiness Brigade
    Retrieved November 2019.

  2. SHIRBRIG Lessons Learned Report
    1 June 2009.

  3. Wikipedia, Rwandan genocide
    Retrieved November 2019.

  4. WBParts, NSN 5820-01-469-8797
    Retrieved November 2019.
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Crypto Museum. Created: Friday 08 November 2019. Last changed: Saturday, 09 November 2019 - 07:41 CET.
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