Have you done any DF work with low chip rate spread spectrum signals down in the noise. It's not easy and you need to fft for the data
A high power pulse train lots easier to DF Sent from my iPhone On Jul 27, 2013, at 3:44 PM, Bob Camp <li...@rtty.us> wrote: > Hi > > A Loran jammer would / could work with a *much* smaller antenna if a local > area was the target. Power is easy at 100 KHz. Loran is no easier / harder to > DF than GPS. > > Bob > > On Jul 27, 2013, at 3:37 PM, Scott McGrath <scmcgr...@gmail.com> wrote: > >> LORAN was/is not perfect geographic features could and did limit reception >> However an effective jammer would need effective power in the hundred watt >> range and a efficient antenna system plus a connection to power grid or >> small Genset. >> >> Not amenable to easy concealment and fairly easy to DF using standard >> techniques especially since location of real station well known and fixed >> >> An effective GPS jammer which can take out a few square miles is the size of >> a trade paperback and runs on batteries and costs under 50 bucks to build >> >> Imagine a scenario where a few hundred of these are deployed with hostile >> intent. >> >> Military and Civillian systems are now useless due to nature of signal they >> are hard to DF >> >> Sent from my iPhone >> >> On Jul 27, 2013, at 2:09 PM, Bob Camp <li...@rtty.us> wrote: >> >>> Hi >>> >>> Loran can / could easily be jammed over a limited area, just like GPS. >>> Nothing crazy large or expensive would be required. The same sort of >>> "malfunctioning this or that" took out Loran from time to time over harbor >>> sized areas. Loran had so many issues with dropping out, that they simply >>> were not worth talking about …. >>> >>> Bob >>> >>> On Jul 27, 2013, at 1:35 PM, Scott McGrath <scmcgr...@gmail.com> wrote: >>> >>>> Key >>>> >>>> Problem with GPS is its easy to spoof on one level and have a complete >>>> denial of service on the other. Out in California a while back a >>>> malfunctioning TV distribution amplifier jammed a major harbor and >>>> surrounding almost 25 sq miles affected all because of a 49.95 TV amp had >>>> a problem. The military receivers had the same problem >>>> >>>> LORAN is virtually jam proof unless you have a very powerful transmitter >>>> >>>> Sent from my iPhone >>>> >>>> On Jul 27, 2013, at 11:17 AM, Michael Perrett <mkperr...@gmail.com> wrote: >>>> >>>>> I have seen a lot of differing opinions on GPS Spoofing and using back up >>>>> systems on this thread. Most pretty good, but a couple off the mark a bit. >>>>> >>>>> Here are a couple of comments on GPS Spoofing. >>>>> >>>>> - There are anti-spoofing GPS receivers available - to "authorized" >>>>> users. Typically DOD. Most, if not all, military receivers utilize the >>>>> encrypted "P-Code", while civilians must use the more vulnerable clear >>>>> text >>>>> "C/A code". The P-Code signals are very difficult to spoof unless you have >>>>> a-pirori knowledge. The newer satellites (GPS III) will have an even more >>>>> robust AS methodology. >>>>> - Note: beware of P-Code, or Military, receivers available on eBay. >>>>> They are useless without the encryption keys distributed by the US >>>>> Government. >>>>> - In the (near?) future there will be four civilian GPS Signals: "The >>>>> government is in the process of fielding three new signals designed for >>>>> civilian use: L2C, L5, and L1C. The legacy civil signal, called L1 C/A or >>>>> C/A at L1, will continue broadcasting in the future, for a total of four >>>>> civil GPS signals. Users must upgrade their equipment to benefit from the >>>>> new signals". ref >>>>> http://www.gps.gov/systems/gps/modernization/civilsignals/ >>>>> - Receivers utilizing the new civilian GPS frequencies can solve the GPS >>>>> equations from more than one frequency and see if any one signal is being >>>>> spoofed. The new civilian frequencies will be more spoof resistant. >>>>> >>>>> Comments on using inertial measurement units (IMUs) to back up GPS. >>>>> >>>>> - Current IMUs with even a "good" drift rate of say, 1 degree per hour, >>>>> available for around a few thousand dollars, will be off 60 nautical miles >>>>> after an hour of uncorrected operation. That can be reduced by other >>>>> sensor >>>>> inputs (GPS, LORAN, pit-log or what ever you have), but the navigation >>>>> solution will eventually degrade to the accuracy of the external sensor. >>>>> If >>>>> my memory serves me for a really deep pocket navigator (having tens to >>>>> hundreds of thousands of dollars, and a large amount of available mounting >>>>> space) IMUs with drift rates of up to a thousand times less can be >>>>> purchased (that's ,001 miles per hour, or around a couple of meters per >>>>> hour), think submarines, etc. >>>>> >>>>> Using a dual sensor navigation system (or timing system! ), such as >>>>> GPS/eLORAN, would obviously make the system so much more robust. >>>>> >>>>> Michael / K7HIL >>>>> >>>>> On Sat, Jul 27, 2013 at 6:43 AM, Scott McGrath <scmcgr...@gmail.com> >>>>> wrote: >>>>> >>>>>> Key here is how does the captain know that GPS is no longer providing an >>>>>> accurate fix? You need 2 or more independent systems to cross check >>>>>> each >>>>>> other. >>>>>> >>>>>> Sent from my iPhone >>>>>> >>>>>> On Jul 27, 2013, at 12:21 AM, Jim Lux <jim...@earthlink.net> wrote: >>>>>> >>>>>>> On 7/26/13 8:45 PM, J. Forster wrote: >>>>>>>> I gather from the article, the GPS position was spoofed and the >>>>>> autopilot, >>>>>>>> in bringing it back to where it was supposed to be, actually took it >>>>>>>> off >>>>>>>> course. >>>>>>>> >>>>>>>> There are places where a few hundred feet makes a big difference, viz. >>>>>> the >>>>>>>> Costa Concordia. >>>>>>>> >>>>>>>> IMO, this is a very convincing reason for something like LORAN. >>>>>>> >>>>>>> I think it's a convincing argument for a captain who pays attention to >>>>>> the other navigation instruments and doesn't blindly follow the GPS. >>>>>>> >>>>>>> It's also a convincing argument that shipboard >>>>>> automation/autopilot/autocontrol vendors need to make more sophisticated >>>>>> software (which I suspect they do, particularly on 200+ foot ships.. I >>>>>> would imagine that there are some aspects of this demo that are >>>>>> contrived.) >>>>>> The ship making and driving business is pretty unregulated. It's all >>>>>> about >>>>>> what the owner of the ship is willing to pay (or what he needs to get >>>>>> liability insurance, if he wants). There's nothing even remotely like >>>>>> DO-178 for shipboard stuff. >>>>>>> >>>>>>> The folks doing stabilized oil rigs probably have sophisticated systems, >>>>>> but they're also using IMUs and other stuff. Ditto for high value things >>>>>> (oil tankers, warships). Molasses tankers? They're probably lucky to >>>>>> have >>>>>> a functioning compass and some old charts. >>>>>>> >>>>>>> >>>>>>> I'm not sure, though, that looking at the big picture, whether your tax >>>>>> dollars are better spent on LORAN, or on some other precision navigation >>>>>> method or on making jam resistant GPS receivers (which do, in fact exist, >>>>>> and make use of things like direction of arrival of the signal..) >>>>>>> >>>>>>> Note that a GPS system with 3 antennas (as is common in systems that use >>>>>> GPS to derive attitude/orientation) would be extremely difficult to >>>>>> spoof, >>>>>> and would be VERY inexpensive to implement. Either the carrier phases >>>>>> and >>>>>> code phases are consistent for all the received signals or they're not. >>>>>> A >>>>>> jamming signal coming from the wrong direction will not have the right >>>>>> direction of arrival relative to the platform orientation. One wrong >>>>>> signal might be tolerable (multipath, etc.) but with a multi satellite >>>>>> fix, >>>>>> I suspect it would be hard to do it. >>>>>>> >>>>>>> Sure, one could throw up N pseudolites on a bunch of UAVs, etc., but >>>>>> that's getting to be a bit noticeable. >>>>>>> >>>>>>> >>>>>>> For what it's worth, I don't know that LORAN has the performance to >>>>>> avoid a Costa Concordia type foul up (assuming they were crazy enough to >>>>>> do >>>>>> the near pass in the fog, so visual navigation didn't work) >>>>>>> >>>>>>> I seem to recall that LORAN had 1/4 nmi kinds of accuracy. it would get >>>>>> you to the channel or mouth of the harbor, but not get you into your >>>>>> berth. >>>>>> You might be familiar with the local propagation anomalies and get better >>>>>> accuracy with experience in your local waters. >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>>> >>>>>>>> -John >>>>>>>> >>>>>>>> ================= >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>>> I boat? The backup is a competent captain. He'd see the compass >>>>>> heading >>>>>>>>> move and quickly disengage the autopilot. I had a boat for years >>>>>>>>> I'd >>>>>>>>> notice a 5 degree change. Mine was a sailboat so I'd be more >>>>>> sensitive to >>>>>>>>> heading changes than a power boater but still the human is the backup. >>>>>>>>> >>>>>>>>> Most autopilots don't directly follow GPS, they use GPS to determine a >>>>>>>>> heading, follow it then use GPS to detect drift and re-compute the >>>>>>>>> heading. >>>>>>>>> the heading would be held by a compass sensor in a low-cost setup or >>>>>> in a >>>>>>>>> larger setup a lazer ring gyro backed up by a compass. So a >>>>>>>>> spoofed >>>>>>>>> GPS >>>>>>>>> would cause the autopilot to "think" there was a bigger crooswnd or >>>>>>>>> current >>>>>>>>> and make a bigger heading change. >>>>>>>>> >>>>>>>>> I bet you could hijack a drone not a manned vehicle the pilot is >>>>>> trained >>>>>>>>> to >>>>>>>>> monitor the automation and he'd very quickly turn it off thinking it >>>>>> was >>>>>>>>> broken. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> On Fri, Jul 26, 2013 at 8:41 AM, J. Forster <j...@quikus.com> wrote: >>>>>>>>> >>>>>>>>>> Prof. Humphry from Texas just reported being able to spoof GPS in the >>>>>>>>>> Med >>>>>>>>>> and take over the nav system of a luxury yacht. He's done this before >>>>>>>>>> with >>>>>>>>>> a drone in the US. >>>>>>>>>> >>>>>>>>>> LORAN as a backup, at least? >>>>>>>>>> >>>>>>>>>> -John >>>>>>>>>> >>>>>>>>>> ============== >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> _______________________________________________ >>>>>>>>>> time-nuts mailing list -- time-nuts@febo.com >>>>>>>>>> To unsubscribe, go to >>>>>>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>>>> and follow the instructions there. >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> -- >>>>>>>>> >>>>>>>>> Chris Albertson >>>>>>>>> Redondo Beach, California >>>>>>>> >>>>>>>> >>>>>>>> _______________________________________________ >>>>>>>> time-nuts mailing list -- time-nuts@febo.com >>>>>>>> To unsubscribe, go to >>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>>> and follow the instructions there. >>>>>>> >>>>>>> _______________________________________________ >>>>>>> time-nuts mailing list -- time-nuts@febo.com >>>>>>> To unsubscribe, go to >>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>>> and follow the instructions there. >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- time-nuts@febo.com >>>>>> To unsubscribe, go to >>>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>>> and follow the instructions there. >>>>> _______________________________________________ >>>>> time-nuts mailing list -- time-nuts@febo.com >>>>> To unsubscribe, go to >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@febo.com >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
