Talking all about airplanes last week led to airplane bounce software this week. by Stan Horzepa, WA1LOU
G3PPT's VHF Communication via Aircraft Reflections <http://www.lsear.freeserve.co.uk/aircraft_scatter.html>Web page describes the aircraft propagation anomaly and includes software to experiment with this RF incongruity. After reading last week's Surfin', <http://www.arrl.org/news/features/2006/11/10/1/>About Airplanes, Mark Herson, N2MH, wrote to tell me about software that attempts to use the reflections from aircraft in order to make long distance contacts. Lionel Sear, G3PPT, wrote the software, which is called SlowFeldXPAS; you can read all about it at the VHF Communication via Aircraft Reflections <http://www.lsear.freeserve.co.uk/aircraft_scatter.html>Web page. The Web page describes this propagation anomaly and includes a link to a revealing paper written by Ray Scrivens, G3LNM, explaining the mechanics of aircraft reflections. Lionel then explains how he determined the best mode of operation to use in his software. According to Lionel, Hellschreiber is not sufficiently sensitive for our purpose, but he developed a very slow form of the mode for use where QRSS CW is used. The software that produced this mode was called SlowFeld, and at some three characters per minute, was very slow, but the sensitivity (readable at a level approaching â'30dB below AWGN) was adequate for this application. After further experimentation, it took only slight modifications of SlowFeld to produce SlowFeldXPAS, a version dedicated to aircraft scatter use, which you can download from this Web page. Until next time, keep on surfin'. (Via ARRL Web)
