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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 N631, March 28, 2021
Moonbounce Radio - 2
Two weeks back here in Wavescan, we presented the story of Moonbounce Radio from the European perspective, and this week we focus our attention on the American initiative, for using the Moon as a passive reflector of radio signals from planet Earth. Interestingly, it was the focus of one man alone throughout much of his professional life that finally brought success to this venture for the United States. That man was John Hibbett DeWitt, and this is his story.
In 1922, 16-year old John H. DeWitt constructed the first radio broadcasting station in Nashville, TN, which he installed in his parents' living room. He launched his new radio station under the callsign WDAA, with just 15 watts on the common channel 360 m (833 kHz) on June 30 (1922). Three years later, he also assisted in the installation of the first radio transmitter for another mediumwave broadcasting station in Nashville, station WSM, which was inaugurated with 1000 watts on 1060 kHz at 15th Ave S., in Nashville, on October 5, 1925.
After that, John DeWitt served with Bell Laboratories in New York for eight years, and then he returned to his beloved Nashville as the Chief Engineer for the now quite famous mediumwave station WSM (The Grand Ole Opry) in 1932. Almost immediately he developed plans to maximize the coverage potential for his WSM radio station, which included the installation of a 50 kW transmitter (the highest power permitted in the United States) and the erection of a radio tower that would be the tallest in North America.
The location for the new transmitter and tower was an isolated country area some 12 miles south of Nashville. A 29 acre site on Concord Road (Hwy 253) was chosen, just off interstate highway I-65 and near to the L&N railway line.
An ornate transmitter building was constructed, a huge 878 ft. tall diamond shaped Blaw-Knox Tower was erected, and an emergency studio was installed in the basement of the building. Back then, the new WSM radio tower was the tallest in North America, a record that it held for nearly 10 years. This powerful new radio complex was taken into service on October 5, 1932, and at that time mediumwave radio station WSM was just 5 years old.
During World War II in the middle of last century, the United States Government War Department chose the WSM Tower, as the tallest in the United States, to serve as an official backup emergency radio station for communication with American submarines when other forms of communication failed.
Now in 1940, John DeWitt at WSM constructed an 80 watt (low frequency) shortwave transmitter and receiver for WGN in Chicago for use in live outside broadcasts. However, before this double unit was delivered to the new owners in Chicago, and therefore while it was still with WSM, Engineer DeWitt configured this combination transmitter/receiver to function on 138 MHz (2 meter) with the intent of making an experimental bounce transmission to the Moon. Perhaps he was hoping he could receive a reflected signal from the Moon 2-1/2 seconds later, on a frequency 300 Hz higher due to the Doppler Effect caused by the speed of the Moon in space.
Ultimately, on the evening of May 20, 1940, DeWitt in Nashville, TN did focus a low power, very high frequency radio signal at the surface of the Moon. Because of subsequent experiments, we now know that there must have been a reflected radio signal, from the Moon back to the Earth. However, because the transmitted signal was so low (only 80 watts), obviously the reflected signal as received back on Earth was not detected.
Almost six years later, John DeWitt tried again to bounce a radio signal, or a radar signal actually, from the surface of the Moon. By this time he was a Lt. Col. in the Army Signal Corps at Fort Monmouth (near Belmar, NJ) and he assembled available electronic equipment for a second era of Moonbounce experimentation.
The equipment used was a complete set of radio equipment SCR271 that included two radio towers that were identified colloquially as the bed-spring mattress, and these were placed side by side, together with a crystal controlled radar transmitter and receiver. The radar transmitter with a power of 3 kW was modified for an output of 50 kW, and the enhanced antenna system produced an effective radiated power (ERP) of 10 Megawatt. The transmission frequency was 112 MHz, just above the standard international FM Band 2.
The first transmission test was made during the evening of January 10, 1946, and a Moonbounce echo from the Moon was successfully received back on Earth. The reflected signal from the surface of the Moon as received on Earth was calculated at considerably less than 1 watt.
The Signal Corps at Fort Monmouth made several additional successful Moonbounce tests back then, all identified as a part of Project Diana. An attractive and now valuable QSL card was printed to verify reception reports from international radio monitors who were able to hear the Moonbounce signals.
So what did they learn from Project Diana? Just two observations. First: In order to gain adequate propagation for a radio signal through the normally reflective ionosphere that surrounds the Earth, it is necessary to utilize a very high frequency channel, considerably higher than the normal mediumwave and shortwave broadcasting channels. Second: The power loss for the very high frequency radio signal to the Moon and back to Earth again shows a degradation loss greater than 1,000,000,000%.
More Moonbounce radio information, and quite remarkable information actually, next time.