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"Wavescan" is a weekly program for long distance radio hobbyists produced by Dr. Adrian M. Peterson, Coordinator of International Relations for Adventist World Radio. AWR carries the program over many of its stations (including shortwave). Adrian Peterson is a highly regarded DXer and radio historian, and often includes features on radio history in his program. We are reproducing those features below, with Dr. Peterson's permission and assistance.
Wavescan N497, September 2, 2018
Historic KDKA Experimental Shortwave Station KDPM in Cleveland, Ohio
It was back during the early 1920s, soon after the end of World War 1, that the Westinghouse company in Pittsburgh, Pennsylvania in the United States began to experiment with the usage of shortwave transmissions. It was soon discovered that shortwave signals have several advantages over mediumwave, including long distances with lower power, less atmospheric static at higher frequencies, and physically smaller equipment.
As an experimental concept, Westinghouse gave consideration to the possibility of using a shortwave relay as a program feed for a distant mediumwave station, rather than renting expensive telephone lines to cover the intervening distance. Perhaps one shortwave signal at a central location could feed numerous mediumwave stations throughout the country as an economical radio network.
For their first practical experiment with a shortwave program feed, Westinghouse chose a shadow location where the KDKA mediumwave signal gave poor reception. In addition, they needed a location where Westinghouse already owned a suitable property.
The city of Cleveland in Ohio was chosen as their first experimental location. Cleveland is a hundred air miles (northwest) from Pittsburgh; the mediumwave signal from KDKA was never heard well in Cleveland, and Westinghouse owned a sizable property in that city.
In February 1921 Westinghouse in Cleveland received government approval to operate a non-broadcast radio station for the purpose of inland communication with other scattered Westinghouse facilities. This new radio station received a sequential callsign KDPM and it was permitted to use Morse Code on any of four specific channels in what are today the standard mediumwave and longwave bands.
The new KDPM was installed in one of the two story industrial buildings on the Westinghouse property at the Lake End of West 58th Street in Cleveland. Test transmissions from this new radio station were noted on 600 kHz in May (1921).
In June of the following year (1922), preliminary plans were laid for the experimental usage of the new KDPM in Cleveland as a radio broadcasting station that received most of its programming on shortwave from KDKA in Pittsburgh. The government license was received during the following month, July.
The first test transmissions from KDKA mediumwave in Pittsburgh were sent from their shortwave transmitter 8XS with 1 kW in the 3 MHz band in September 1922. The receiving antenna in Cleveland was a single strand 8 feet square loop and the signal from the output of the small two tube receiver was fed straight into the mediumwave transmitter. The transmitting antenna at KDPM was a copy of the one for the KDKA mediumwave transmitter, at 105 feet high and 200 feet long.
Thus the new mediumwave KDPM was on the air as a remote slave transmitter with 250 watts on initially 833 kHz. It was installed in a second floor wooden attic of the Westinghouse foundry, and we would suggest, that it was operating in what we could call building number 5, right against the taller eight story building at the northern edge of their property.
The series of shortwave test transmissions from KDKA-8XS in Pittsburgh with the relays on mediumwave via KDPM in Cleveland came to an end in January 1923. Regular daily programming began on March 4, 1923 and by this time KDPM was operating on 1110 kHz.
Because radio station KDPM was simply an experimental venture, the whole project simply faded away into nothingness after a while; and in fact, it was superseded by another similar project elsewhere, though on a much larger scale. The Westinghouse repeater broadcasting station, KFKX, in Hastings, Nebraska, was officially opened later in the same year (1923), on November 22.
Station KDPM was then relegated back to its original purpose, for use as a company communication station, and it continued in this role for the next half dozen years. However, even though the low power shortwave signal from Pittsburgh was not always reliable in Cleveland and it was sometimes a bit noisy, yet nevertheless, the experiment was considered a success, and so the new similar project at Hastings proceeded into fruition.
Alice Brannigan (Editor Tom Kneitel) in the August 1992 issue of the American monthly radio magazine Popular Communications, stated that the programming from KDKA-8XS-KDPM was at times broadcast on shortwave from another transmitter in Cleveland, with the callsign 8XG.
According to entries in the government issued Radio Service Bulletins for that era, station 8XG was an experimental Land Station owned and operated by the Willard Storage Battery Company at 12651 Taft Street in Cleveland. The shortwave callsign for Westinghouse in Cleveland was 8XO.
Was that a typo in Popular Communications, and 8XG was typed instead of 8XO? On the other hand, yes, it is possible that 8XO did indeed relay the Westinghouse radio programming, maybe on an experimental basis.
The KDKA booklet, It Started Here, printed in 1970, states that the second KDKA shortwave transmitter was installed at KDPM in Cleveland; 8XS Pittsburgh was their first. Maybe then perhaps both of these shortwave transmitters in Cleveland, Westinghouse 8XO and Willard Battery 8XG, did indeed carry the KDKA shortwave programming at times.
The Westinghouse property on West 58th street in Cleveland, the home of mediumwave KDPM and its novel shortwave experiment, has lain abandoned for the past many years. There is a For Sale notice that was recently attached to the front facade of one of the two story red industrial buildings.
Coming sometime soon, the story of the follow on Westinghouse radio station, KFKX in Hastings, Nebraska.