A hundred years ago, the radio experimenter in the nation’s capital could get the parts he needed from Doubleday-Hill Electric Company, as evidenced by this ad in the Washington Evening Star, July 4, 1921. The company was located at 715 – 12th St. NW, Washington.
The shop and its staff as they appeared about that time can be seen at the photo below, from the Library of Congress.
The company was actually based in Pittsburgh, and was the licensee of KQV, formerly 8ZAE. The April 1917 issue of QST carried this ad for their rotary spark gap:
