| Historia komunikacji Zemia - Księżyć - Ziemia (EME) dyletantowi Czerepakowi Miszy dedykuję Wyśmiany system anten przez dyletanta Miszę Czerep |
| Project Diana Project Diana, named after the Moon goddess of the Roman mythology, was the first deliberate and successful attempt at bouncing radar signals off the Moon. The first echoes were successfully detected at 11:58 AM on Januray 10, 1946. In charge of the project was Lt. Col. John H. DeWitt Jr. of the US Army Signal Corps at Evans Signal Laboratory at Fort Monmouth near Belmar, New Jersey. The equipment consisted of a modified ‘SCR-271 early-warning radar’, providing 3 kW of output power at 111.5 MHz using 0.25 second pulses. The antenna was a reflector array consisting of 64 horizontally polarized half-wave dipoles, providing a gain of approximately 24 dBi. was mounted on a 30 metre tower and was only controllable in azimuth. On the receiver side, the front-end amplifier had a gain of 30 dB with an NF amounting to 4 dB which was considered low at the time. The receiver bandwidth was only 57 Hz, centred at 180 Hz, making accurate Doppler calculations for every test a necessity. Visual echo indication was furthermore provided on a radar scope. Formally, the objectives of Project Diana were to determine whether radio signals could be transmitted through the ionosphere and to develop radars capable of detecting Soviet missiles. The Moon was chosen as a target since no missiles were available for the experiments. Informally however, being a radio amateur, DeWitt also had personal motives for the project. While working as chief engineer of radio station WSM in Nashville, Tennessee, DeWitt had already tried, in May 1940, to bounce radio signals off the Moon, alas unsuccessfully due to insufficient receiver sensitivity. He also had an interest in astronomy, sparked by Karl Jansky’s discovery of cosmic noise in the early 1930s. Hence, when the war ended it is not surprising that DeWitt seized the opportunity to initiate a project like Diana, before being discharged from the Army. Furthermore, one cannot help but wonder if it was a coincidence or not, that three out of five chief members of the project were radio amateurs. The five lead members were John H. DeWitt Jr. (W4ERI, formerly W4FU and later N4CBC), Herbert P. Kauffman1 (W2OQU), Edwin King Stodola (W3IYF later W2AXO), Harold D. Webb and Jack Mofenson. Naturally, more people were involved in the project, some of which were also radio amateurs. DeWitt’s team was however not alone in fulfilling their ambition to bounce radio signals off the Moon. Just a few weeks after the success of Project Diana, a team from Hungary, led by Zoltán Bay, succeeded in their attempts as well . However, having a less powerful system than the Americans, Bay had to somehow increase the received SNR. This led him to inventing the important technique of time integration, using a so called hydrogen coulometer. Unfortunately, Bay had to operate during war-time conditions, forcing him to entirely rebuild his system three times over. Had this not been the case, it is quite possible that Bay would have succeeded before DeWitt in deliberately receiving echoes from the Moon. The word ‘deliberately’ is important in this context. For according to several sources, operators of a German experimental radar succeeded in hearing their own lunar echoes in January 1944, by pure chance. This so called ‘Würzmann radar’ was built by the Telefunken company and was situated on the island of Rügen in the Baltic Sea. It operated at 560 MHz with a peak power of 120 kW, having a very narrow beam antenna consisting of an array with no less than 640 dipoles. Regardless of the above, Project Diana was the the first calculated and successful attempt at receiving radar echoes from the Moon, determining with certainty that radio waves could penetrate the Earth’s ionosphere. This discovery was a prerequisite for all space related communication projects to come, thus marking the beginning of the space age. |