“Seemed early to me, too, but apparently there had been radar for a couple of years at that time.”
Not the case.
In 1937, radar was still being developed by the British. And the first systems they put into action were gigantic fixed ground installations, far too large to be hauled around the world to the Pacific.
Systems small enough to mount on a vessel or an aircraft were still many years in the future; even when such became reality, the critical components were highly classified, available only to select British and US researchers and manufacturers.
The assertion here casts everything else in the article into doubt.
True enough. Mobile radar really had to await the UK’s development of the magnetron during the war.
Maybe the author meant radio station.
As I recall that was when FDR went on the Internet to reassure the nation.
"On the radar" and "off the radar screen" could be considered as metaphors, but it's embarassing for a group that's supposed to be experts to make this kind of blunder.
One website, though, says that radio direction finding was available at the time and that could have made a contribution to tracking Earhart's progress.