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