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Automatic Direction Finder - this page is a stub

ADF-210 was a Radio Direction Finder (RDF), also known as an Automatic Direction Finder (ADF), developed around 1971 by Ocean Applied Research (OAR) in San Diego (Californa, USA), as part of a range of direction finders. The device is based on the Adcock principle and was suitable for locating transmitters in the 11 m radio band (26-28 MHz), also known as the citizen's band (CB).

The device was used for navigation, but also for locating miniature transmitters, such as the ones used for the detection of schools of tuna fish.

The device is housed in a heavy metal enclosure – common for most OAR direction finders – and is suitable for the reception of up to 10 crystal-controlled channels between 26 and 28 MHz. A fairly large loop antenna – constructed from two perpendicular loops – should be mounted out­side, for example in a mast on the deck of a ship, or on the hull of an airplane. The direction to the transmitter was shown on a CRT display.

The ADF-210 could also be mounted within a vehicle, for use on land. In the Netherlands, for example, it was used in the early 1970s by the Radio Monitoring Service (RCD) for locating illegal transmitters in the 11 metre CB-band, which was prohibited in the Netherlands. The major drawback of the ADF-210 however, was that it only had room for 10 channels, whilst CB radios typically had 23 channels, or 28 if the so-called A- or Alpha-channels were counted as well.

It was replaced a few years later by the ADF-928, which covered the original 28 channels of the 27 MHz CB band in AM, and finally – in the mid-1970s – by the more versatile ADF-940, which had a scanner and covered all 40 channels of the expanded 27 MHz (CB) band in AM and FM.

Known models
The following models of the OAR ADF direction finder are known. Note that the 900-range was probably reserved for specials and that the last two digits indicate the number of channels. No information about these variants is publicly available at the moment.

  1. At the time, the CB-band consisted of 23 AM-modulated channels, plus five so-called A-channels or alpha-channels that were used for radio controlled models [7].  Wikipedia

  1. ADFS-210, Sales Leaflet
    OAR, 1971.

  2. ADFS-210, Operating Instructions and Maintenance Manual
    OAR, 1971.

  3. ADFS-210, Operating Instructions for Power Supply and Battery Supply
    OAR, 1971.
  1. Wikipedia, Citizens band radio
    Retrieved December 2016.
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Crypto Museum. Created: Thursday 17 December 2020. Last changed: Thursday, 17 December 2020 - 21:13 CET.
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