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.
