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What's In a Name -- Of My Antenna?
On Fri, 25 Mar 2016 21:39:10 -0700, "Sal M. O'Nella"
wrote: "Jeff Liebermann" wrote in message .. . Major snippage Arnold Wilkins recalled that it was possible to detect an airplane when it created multipath interference patterns as the airplane flew between the transmitter and receiver. A field test was arranged, it worked, and the rest it history. ================================================= ======== I recall an article in an electronics magazine about an aircraft detection system that worked that way. It was tested in Maryland using the area's TV station signals. http://users.ece.gatech.edu/lanterma...ultistatic.pdf Wikipedia has an article called "Passive Radar." "Sal" More correctly, it's CW radar, where the target is illuminated by a simple carrier, and the interference pattern is detected by a receiver located somewhere else. While it is possible to use an RF seeking missile to remove the transmit source, the receiving station(s) are difficult to find and detect because they emit no RF. The CW "illumination" transmitter can also be a broadcast TV station, which is rather politically incorrect to destroy. Similar systems that use broadcast, cellular, paging, beacons, and repeaters have been built and tested. I suppose ham operators could have built such a device, but were probably discouraged by the airlines and military not offering QSL cards for tracking their flights: https://en.wikipedia.org/wiki/Continuous-wave_radar However, please not that it only works with modulation schemes that have a carrier. SSB, spread spectrum, and some forms of digital data don't work. The original RADAR was RDF (radio direction finding). At the time, most everyone was thinking in terms of some kind of burglar alarm, where the aircraft would cross a radio "beam" as in the common optical door annunciator. Other schemes were based on detecting the IR from hot engines or engine sounds. When the RDF was thrown together, and combined with the oscilloscope, the designers were amazed that they could accurately measure range, as well as follow the path of large artillery shells. So, the "ranging" was added to the acronym. 11PM and I'm still working in the office. I can see it coming... dinner at midnight (again). What did I do Friday evenings before I discovered computahs? -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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