AO-7 Contact at the 2007 Dayton Hamvention

The story behind AO-7 is pretty amazing. It was launched in 1974 into a low earth orbit at an altitude of about 1450 kilometers. In 1981, however, one or more battery cells shorted out and subsequently shorted out the entire voltage buss. In 2002, that battery short became an open. Although the battery were long since dead, the satellite could now power up as long as it was in the sunlight and its solar cells were receiving energy. Each time that the satellite comes out of eclipse, it powers up in one of two different modes: Mode A is 2-meters up and 10-meters down. Mode B is 70-cm up and 2-meters down. During this demonstration conducted by AMSAT-NA at the 2007 Dayton Hamvention, they were prepared for either mode. The satellite did come up in Mode B. You will see the 2-meter and 70-cm Yagis. These are the so-called "cheap Yagis" that have been described in several construction articles. The transceivers used were a pair of Yaesu FT-817's operating in SSB mode. In the video you will probably notice the horizontal 10-meter receiving loop antenna. As you will notice, making contact was somewhat difficult. The antennas had to be re-adjusted every couple of minutes, and both radios had to be adjusted to compensate for the Doppler effect. On top of this you need to find your own transmission as it comes back down the downlink, otherwise you can't have a QSO.

Last updated Friday, April 4, 2014. ©2004 - 2014 by Edward S. Raybould.  Extracting written content, images, audio clips, video clips, applets, and ActiveX controls, without written permission from the author is expressly prohibited.

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