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The development of over-the-horizon radar at the Naval Research Laboratory

In 1956, the Naval Research Laboratory completed a set of experiments that showed 1) that VHF and HF radar echoes could be coherently processed, and 2) that the ionosphere is often sufficiently stable for a radar operating in the high-frequency band (3 MHz to 30 MHz) to be capable of detecting and tracking targets beyond the normal microwave radar horizon. Later in 1961, the Naval Research Laboratory began operation of their single-site, over-the-horizon radar located on the shores of the Chesapeake Bay. This radar was called MADRE, for magnetic drum radar equipment, and demonstrated many of the basic capabilities of high-frequency, over-the-horizon radar. This paper chronicles the development of the hardware and software that comprised the MADRE radar and identify the people that participated in its development.