Moonbounce Enthusiasts Enjoy Conference, Brittany Coast
The site of the gigantic antenna in France that received the first live TV broadcast from the US via the Telstar satellite served as the backdrop August 25-26, as more than 100 moonbounce (EME) enthusiasts from 18 countries gathered to compare notes and to socialize. The 16th International EME Conference was held at the Parc du Radôme in Northern Brittany. In July 1962, the 64 meter Radôme was on the receiving end of the first TV satellite link between the US and Europe. Those attending EME 2014 engage in similar activity, bouncing their Amateur Radio signals from Earth to the Moon and back, operating on frequencies as high as 77 GHz. The conference featured some 2 dozen presentations on moonbounce-related topics.
“Speakers from all over the world contributed their experience, technical achievements, and research,” said Rick Rosen, K1DS, one of the attendees. “Workshops and demonstrations were interlaced with the program and included operation of the on-site 144 MHz digital EME and 5.6 GHz CW/SSB EME stations, and reception of the 10 GHz EME beacon with a small 50 cm dish, preamp and down-converter.” Rosen said attendees also exchanged technical small talk throughout the 2-day event. Rosen said a presentation by Al Katz, K2UYH, addressed the important issue of Doppler shift in EME work.
“Although Doppler shift for EME signals is almost negligible on 6 and 2 meters, it becomes a bigger challenge as the frequencies used are increased. As there are many stations using 432 MHz and bands through 24 GHz to communicate by the moon, Doppler shift becomes trickier to calculate,” Rosen said in recounting Katz’s talk. “Doppler shift at 10 GHz can be several kilohertz. The Earth is continually spinning and the apparent position of the moon is changing at rates that may differ for both the transmitting and receiving stations. The ability to listen to one’s own echoes or to place a signal where it will likely to be heard by a DX station is critical to the success of an EME QSO.”
“Al walked us through the various situations, use of Doppler prediction software and helped clarify to many of us the use of these tools,” Rosen said.
A presentation by Jan van Muijlwijk, PA3FXB, outlined the history and restoration of the 25-meter diameter Dwingeloo dish, which has been operational as a radio astronomy site since 1956 but sat dormant since the 1990s. As van Muijlwijk’s presentation explained, volunteers restored the facility during a 2-year publicly funded project that involved disassembling and refurbishing the dish. Restoring the reassembled dish to its mount involved the largest crane in The Netherlands.
The PI9CAM station at Dwingeloo is now active on the air on 432 MHz and 1296 MHz moonbounce. “The station also was used to help an ailing nanosatellite last fall,” Rosen explained. “[T]he satellite became unresponsive to commands due to a spurious 2 meter output that was blocking the 432 MHz command receiver. Once software was loaded at Dwingeloo, a set of commands were sent to shut off the 2 meter transmitter, and the satellite was successfully restored to operation.” Rosen said the PI9CAM station is one of the easiest to work, by even modest EME stations. The Dwingeloo dish has even served as a wedding venue.
Hans van Alphen, PA0EHG, described and demonstrated a small-dish EME 10 GHz beacon receiver. The DL0SHF 10 GHz beacon was placed on the air using a 7.6-meter dish and 50 W output in December 2013. Using a compact motorized auto-tracking system and a 48 cm dish, van Alphen was able to copy the beacon in both its high (600 W) and low (50 W) power outputs, Rosen said.
The ARRL EME Contest takes place over several weekends this fall — October 11-12, November 8-9 and December 6-7. EME 2016 will take place in Venice, Italy. — Thanks to Rick Rosen, K1DS