SCR-270 (Signal Corps Radio) - World War II
The SCR-270 (a mobile long-range aircraft detector, or early-warning set) — had begun before the nation entered the war. A SCR-270 on Oahu detected the approach of Japanese aircraft the morning of Dec. 7, 1941 — picking up the planes' echoes when they were 130 miles away and giving the warning no one would believe.

The SCR-270 operating position shows the antenna positioning controls, oscilloscope, and receiver.
Photo from "Searching The Skies"

A mobile SCR-270 radar set.
Photo from "Searching The Skies
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This photo shows a restored model of the "Pearl Harbor radar," type SCR-270.
The photo was taken in front of the Historical Electronics Museum near BWI Airport, Baltimore, MD.
Pictures from:SCR-270 Historical Notes (Click for more information on radar in WWII)