"J. Forster" <[email protected]> wrote: >> I've read and heard from this forum as well as a number of other >> sources that GPS can be easily jammed. What makes GPS so >> vulnerable? How can it be jammed?
> Signal strength. > LORAN transmitters put out multi-hundred KW to MegaWatt class > pulses. Wiki has a list. I would think a GPS bird puts out less > than 100 Watts CW. > Also, GPS birds are a LOT farther away, especially measured in > wavelengths (much higher path loss) > Those factors combine to make a huge difference in received power. > It could well be over 100 dB. >> From what I've heard a GPS jammer smaller than a deck of playing >> cards can easily wipe out GPS w/in a mile or more for a week or >> longer. > John It should be easy to locate a jammer. Go to the area where the GPS signal is being jammed. Drive in some direction until the signal is regained. Repeat to find three locations where the signal is lost. Three points define a circle. The diameter tells the strength of the jamming signal. The center defines the location. Once you are near the center, ordinary DF techniques should quickly identify the source. For faster response, have a number of GPS receivers report the status of the GPS signal to a central location. This would identify a moving jammer. It should also be possible to develop a GPS antenna with one or more nulls in the horizontal direction. Rotate the antenna until the GPS signal is regained. The null points to the jammer. Multiple receivers would remove the ambiguity from antennas with more than one null. These techniques should identify a jammer very quickly, perhaps in hours or minutes instead of weeks. I'm sure the military has some more advanced methods, as well as effective methods of dealing with the threat. Mike Monett _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
