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LOCATE ™ is a suite of integrated products for spectrum monitoring, direction finding, adaptive beamforming and geolocation of high frequency signals, introduced around 2008 by Roke Manor Research in Romsey (UK). The system consists of various digital receivers, antennas and software.

Typical antenna configuration for global direction finding

Sarsen antennas
LOCATE is typically build around a field of Sarsen antennas [A], arranged in concentric circles as shown in the diagram above. Each Sarsen antenna consists of a non-resonant vertical monopole combined with crossed loop elements, mounted on a circular metal ground plane. In a typical setup, there are 4 concentric circles (1, 2, 3 and 4) with 13 evenly spaced Sarsen antennas each. Together with the reference antenna at the center (R), this totals to 53 antennas. Each antenna provides 3 independent outputs that are connected to an array of synchronised digital receivers.

Note that the reference antenna (R) and the inner circle of antennas (1) are mounted onto a larger common circular groundplane (U) that also acts as a roof for the underground receivers. Via data lines, The receivers are connected to a remote monitoring station, where multiple workstations can simultaneously use features like adaptive digital beam forming (ADBF) and radio direction finding (RDF) with a resolution of 1° — also known as Super-Resolution Direction Finding (SRDF).

Digital receivers
For the actual reception of the signals, two digital receivers are available: DWR16 and the larger MCDWR16. The latter contains up to nine DWR16 receivers in a single 2U 19" rackmount case. Each MCDWR16 receiver provides up to 36 simultaneous independently tuned narrowband channels, or 4 simultaneous channels for direction finding. For larger systems, two MCDWR16 receivers can be combined. The receivers are controlled via USB 2.0 using Windows™ software.

The diagram below shows a typical configuration of the LOCATE system. The signals from the antenna field are combined in the Antnna Control Unit (ACU) and then passed to one or more MCDWR-16 receivers. For remote access, the data from the receivers is served via TCP/IP, either to the internet – or to a private intranet, from where the signals are delivered to the applications (App). For more accurate direction finding, the data from multiple installations can be combined.

For mobile direction finding, for example from a direction finding vehicle or aboard a ship, a GPS receiver can be added to the system, so that the data can be correlated when delivered to remote monitoring stations. This is also known as team-based direction finding, or LOCATE-T.

Pilot project
One of the first users of LOCATE was the Dutch Ministry of Defense, who purchased it in 2008 on behalf of the NSO (now: JSCU), for its intercept and monitoring station in Eibergen (Netherlands). The system became operational in late 2009 and is still in use today (2022). It is part of the Dutch intercept and codebreaking operation run by SVIC, which is now also part of the JSCU.

The image above shows the almost finished Sarsen arrays in Eibergen in July 2009, just before the system became operational. Image obtained from Google Streetview [2].

  1. Sarsen — Compact HF antenna with co-sited monopole and crossed loop elements
    Roke Manor Research Ltd., 14 February 2014. 1

  2. MCDWR16 — Multi-channel Digital Wideband HF Receiver System
    Roke Manor Research Ltd., 14 February 2014. 1

  3. DWR16 — Digital Wideband Receiver
    Roke Manor Research Ltd., 14 February 2014. 1

  4. LOCATE, leaflet
    Roke Manor Research Ltd., 2020.

  5. LOCATE - Strategic HF signals intelligence
    Chemring Technology Solutions, 2017.

  6. Improving Signal Detection in Radio Direction Finding Systems
    Dr. David Sadler, SSPD2016 Conference, 22 September 2016.
  1. File obtained via Wayback Machine.

  1. LOCATE - Global Scale Direction Finding
    Retrieved February 2022.

  2. Google Streetview, Sarsen antenna arrays in Eibergen (Netherlands)
    Retrieved 20 February 2022.
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