This appears to be the second radio broadcast by a U.S. president, as earlier on this day -- May 30, 1922 -- Harding's speech at Arlington Cemetery had been carried by the same two stations -- NOF in Anacostia, D.C., and NAA in Arlington, Virginia.
 
Popular Radio, August, 1922, page 232:
Harding first U.S. presidential radio broadcast
THE  PRESIDENT  SPEAKS  TO  THE  GREATEST  RADIO  AUDIENCE  IN  THE  WORLD
At the dedication ceremonies of the Lincoln Memorial the President addressed an audience of about 50,000 people. But in front of him was placed a microphone that transmitted his voice to two radio stations--one at Anacostia and one at Arlington--which broadcasted the voice at wavelengths of 412 and at 2,650 meters respectively.