"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 N289, September 7, 2014
Another Blast from the Past: American Mediumwave Radio on High Power
On two previous occasions here in Wavescan we have presented the story of high powered broadcasting; on longwave throughout the world, and on mediumwave throughout the world except for North America. On this occasion we present the story of high powered radio broadcasting on mediumwave in the United States, Mexico and Canada under the title "Another Blast from the Past: American Mediumwave Radio on High Power."
As in other parts of the world, when mediumwave radio broadcasting made its first tenuous attempts in the United States, the transmitter power was quite low, sometimes as low as 5 or 10 watts, with 500 watts considered to be in the top bracket. The first station in the United States at 5 kW was Powell Crosley’s famous WLW in Cincinnati, Ohio which was inaugurated in January 1925 on 710 kHz at a new location in Harrison Ohio.
Even though WLW became quite famous in the American power race, yet it was not the first station to operate at a higher power level. Towards the end of the year 1925, Westinghouse opened a new facility at Bound Brook for their mediumwave station WJZ which was licensed at the time to Newark, New Jersey.
This new WJZ transmitter was rated at 50 kW (on 660 kHz) and it is listed as the first station in the United States at this power level. However, the strong signal from the new WJZ overwhelmed everything else on the air and so this higher power was in use only spasmodically for the first ten years.
Three years after the inauguration of WJZ at a spasmodic 50 kW, the Cincinnati WLW inaugurated its 50 kW unit at a new location in Mason, Ohio, somewhat north of Cincinnati itself. This was the first mediumwave station with regular operation at 50 kW in the United States, and several other stations followed in quick succession.
The first super power station in the United States was not WLW, and not even KDKA, but rather WGY at South Schenectady in New York State.
According to Radio Broadcast magazine for October 1927, station WGY was permitted to conduct test broadcasts at 100 kW from midnight until 1:00 am under the callsign W2XAG. These high powered test transmissions began on August 4, 1926, and a photo of the transmitter is shown on page 340 of this particular issue of Radio Broadcast magazine. At an increased power of 200 kW, W2XAG began another series of test transmissions on March 9, 1930.
Then came the well-known KDKA at Pittsburgh in Pennsylvania. In the early part of the year 1932, the famous KDKA began experimental transmissions at 400 kW from its location at Saxonburg under the callsign W8XAR. These experimental broadcasts were permitted on air only between 1:00 am and 6:00 am.
Nearly two years later, WLW began test transmissions from its new 500 kW transmitter under the callsign W8XO. This massive transmitter was assembled under contract by RCA at their Camden factory in New Jersey.
Both GE and Westinghouse participated as sub-contractors for the Ohio project by providing basic segments for the total transmitter assembly which was made up of a 50 kW transmitter acting as the driver followed by three successive power amplifiers. The entire transmitter was installed against the back wall of a second building at Mason, Ohio, adjacent to the regular transmitter for mediumwave WLW. The entire facility, transmitter and antenna system, cost a half million dollars and it was inaugurated on May 2, 1934 during a ceremony at the White House with President Franklin D. Roosevelt.
However, because of the massive power output from Mason, Ohio, complaints flooded in from listeners in both Canada and the United States who complained of interference to programming from other stations on the same or nearby channels. People living nearby to the massive transmitter complained that the programming could be heard from metal roofing, coil springs in mattresses and from other spots at the conjunction of two different metals. In response, the power output from WLW-W8XO was reduced to just 50 kW during the hours of darkness.
During World War 2, the 500 kW W8XO was switched into service for occasional special broadcasts for American servicemen on duty in Europe. The last time that W8XO was on the air with programming at full power was in 1943, though the transmitter was maintained for possible usage up into the 1960s. Sometime afterwards, the transmitter was gutted, leaving just the shell, and the antenna system was sold to an FM station in Eaton, Ohio, station WCTM (WJAI-WGTZ), 92.9 MHz.
During the era running from the 1930s into the 1960s, somewhere around twenty mediumwave stations in the United States applied to the FCC for approval to install super power transmitters, and the requested power level varied from 400 kW to 750 kW. However, none were approved, and the maximum power level for mediumwave in the United States (and Canada also) has remained at 50 kW.
The first high powered mediumwave transmitters in Canada were 50 kW units that were installed for coverage of Toronto and Montreal in 1937. The new CBL Toronto was built at nearby Hornby and it was allocated the channel 740 kHz; the new CBF Montreal was built at nearby Contrecoeur and it was allocated the channel 910 kHz.
Interestingly, Mexico also entered the power race back in the 1930s with a whole slew of stations in northern Mexico that were bent on capturing listeners across the border in the United States, a lucrative commercial market. These border blasters as they were called, emitted power ranging from 50 kW, up to 100 kW and 250 kW, and even 500 kW.
Station XED in Reynosa was the first border blaster in Mexico at 10 kW in 1930. This station later became XEAW. It appears that the highest powered border blasters in Mexico have been XERA at Villa Acuna, and XEX & XEW in Mexico City, each at around 500 kW.
The current WRTVHB lists just seven super power mediumwave stations in Mexico. These are:
|One station at 78 kW||XEWW||Tijuana||690 kHz|
|Four stations at 100 kW||XEG||Monterey||1050 kHz|
|XEP||Mexico City||1060 kHz|
|XERED||Mexico City||1110 kHz|
|XERF||Ciudad Acuna||1570 kHz|
|One station at 150 kW||XEWA||San Luis Potosi||540 kHz|
|One station at 250 kW||XEWW||Mexico City||900 kHz|
In the United States itself, four super power stations have been constructed and taken into regular radio broadcasting service. The first on air was WGY-W2XAG at South Schenectady in New York State with 100 kW in 1926 and 200 kW in 1930. The second superpower station was KDKA-W8XAR at Saxonburg in Pennsylvania with 400 kW on 980 kHz in 1932. The third was WLW-W8XO in Mason Ohio with 500 kW on 700 kHz in 1934.
The fourth American superpower station was WJZ in Bound Brook, New Jersey with 500 kW on 770 kHz. However, this WJZ super power transmitter was never activated at Bound Brook in the United States; instead it was exported to England for another purpose, and that’s another story for another day here in Wavescan.