According to contemporary station lists, Charles L. Austin operated Special Amateur station 7ZI in Portland, Oregon, although most of Austin's early broadcasts were transmitted over Experimental station 7XF, which was licenced to his company, the Northwestern Radio Manufacturing Co.
Radio News, October, 1921, pages 281, 348:

Advertising  by  Radio
Here is the advertising station from which is sent music through a phonograph. The name of the record, its price and the name and address of the shop where it may be bought is announced before each piece. The radiophone set may be seen on the right.
W HILE nearly every day sees some new use to which the radio telephone may be put, perhaps none has been found more interesting or productive commercially, considering the small cost involved, than the advertising of phonograph records by an enterprising music store manager at Portland, Oregon. Charles L. Austin was accustomed each night to send out phonograph music via radiophone for the benefit of sailors at sea and any others who might wish to listen in, from his experimental station at Portland. Austin formerly was a radio operator on an ocean liner and realized the monotony of many trips and the radio-sent music proved a welcome benefaction to many.
    Clyde Freeman, manager of the Portland Remick Song shop, heard of the novel musicals, called on Austin, and substituted a new phonograph for the old one in use and the very latest in jazz dance music, songs and classics, for the collection of antiquated records. Preceding the playing of each record, an announcement is made telling the name of the record, its identification number, on what make of phonograph played and where the records may be obtained. Austin uses a 500-volt sending apparatus, the easy audibility range of which is 600 miles, although under favorable conditions reports have been made that the concerts were heard on the vessel Reuce, 1,400 miles from the sending station.
    Many glowing claims are set forth for the radio telephonic advertising of music. It enables rural dwellers to keep up with the newest in records and music, for there are now many receiving sets throughout the country districts which can listen to the concerts. The information gathered through the air is distributed rapidly and many phonograph record sales have been made to farmers and others who have heard particularly pleasing records over the air. Many sailors who have heard the music at sea have purchased upon calling at port. There is a new business opened up among a class of persons who never would have been phonograph owners had it not been for the romance connected with the receiving of music via radiophone. Taking 600 miles as the distance over which the music is plainly heard, we have a grand total area of 1,130,076 square miles, and on account of the almost negligible expense of the advertising method is declared the most economical per square mile of territory covered of any yet tried. The system will be permanent as results obtained have been eminently satisfactory.