“By 1936 the first five Chain Home (CH) systems were operational and by 1940 stretched across the entire UK including Northern Ireland”
https://en.wikipedia.org/wiki/Radar
I seriously doubt that there was any radar coverage in the middle of the Pacific Ocean in 1937. She could not have been on oxygen, so she probably flew at 12,500 feet or less. The horizon at that height would have been about 250 miles.
Did the article say which radar station had contact with her?
No.
I don’t think there was ANY radar in the pacific in 37. The set we had in Hawaii in 41 was the very first to my knowledge.
And as for other radio and navigation aids, there was a line of US Navy ships set up along the anticipated route as radio pickets.
This was not an ordinary thing to try. Before that it was only done in the Clipper flying boats with a ton of fuel, and highly skilled navigators, flying the exact routes Noonan had pioneered.
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Radio, not Radar.
It could have been thousands of miles away. This is especially true at night.
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” ... She could not have been on oxygen, so she probably flew at 12,500 feet or less. ... “
Before the Second World War, rules of flight were far less detailed and far less restrictive. The FAA safety bureaucracy did not exist (the FAA itself did not exist until the 1950s). Civilian fliers routinely climbed far above 12,500 ft MSL that today marks the upper limit of flight in the US, without supplemental oxygen: they did it to deliver airframes to buyers, or on scheduled airlines outside CONUS. In his autobiography, the late Ernest K. Gann describes ascending to some 18,000 ft MSL to clear mountain passes in South America.
Gann is better known for his novels (Island in the Sky, Fate is the Hunter etc), but he did duty as a civilian transport pilot for Military Air Transport Service during WWII.
The books and essays he subsequently authored on commercial flying in the 1930s and 1940s are a revelation: well worth the effort to find and uniquely readable, for those interested in that period of the history of aviation.