Des Moines (Iowa) Register, August 25, 1922, page 14:

BIGGEST  STATE  FAIR  IN  WORLD  HITS  ITS  STRIDE
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Children  to  Be Admitted  Free  Today.
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    Another feature of the exposition this year, is the radio broadcasting station whose call letters are WJAY. The day's program with brief details regarding the salient features of the day's activities are broadcast over the state from 9:30 to 10 o'clock in the morning, and from 1 to 2 o'clock in the afternoon.
Des Moines (Iowa) Evening Tribune, August 29, 1922, page 1:

WILL  BROADCAST  MUSICAL  PROGRAM
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    Station WJAY, the official Iowa state fair broadcasting station of the Thomas Electric company, will broadcast a complete musical program Wednesday evening at 8 o'clock. This program is furnished through the courtesy of the Simpson college conservatory of music and will consist of the following numbers:
Millers WooingQuartet
GarmenaQuartet
Tenor SoloMr. Butterfleld
Piano SoloMiss Heaton
RosaryQuartet
BarcarolleQuartet
Sing, Sing, Birds on the Wing, duet   Miss McIntire
Contralto SoloMiss McIntire
Hark, Hark, My SoulQuartet
Piano SoloMiss Heaton
Soprano SoloMiss Mullican
DuetButterfield and Mullican
Baritone SoloMr. McIntire
Quartet from RigolettoQuartet