eLoran and current GPS vulnerability - Page 1
Forum section: electronics / projects

author: SoundTech-LG
author_rank: Frequent Contributor
timestamp: April 17, 2015, 02:38:32 pm
content: Looks as if the U.S. is considering reinstating the Loran system of navigation, and timing signals in the form of enhanced Loran. The N. Koreans apparently are having fun jamming GPS over S. Korea. No reason that cannot be done over any region.http://rntfnd.org/2015/03/27/new-gpseloran-bill-in-congress/

author: max666
author_rank: Frequent Contributor
timestamp: April 17, 2015, 04:11:02 pm
content: Just wanted to mention that since GPS was build and is maintained by the United States, the US can jam GPS whenever and wherever they want and have done so in the past. Little fun fact for all none Americans who depend on GPSWhat's the status of Galileo, lemme check ... well anyway, there's always GLONASS for those who have coverage I guess.

author: SeanB
author_rank: Super Contributor
timestamp: April 17, 2015, 04:49:22 pm
content: They sold off all the old hardware for LORAN though, including the spare PDP-11 computers that ran it, along with the software. Steve Gibson bought a whole load of them on eBay for playing with.

author: SeanB
author_rank: Super Contributor
timestamp: April 17, 2015, 07:35:12 pm
content: NK does not really have much in the way of electronics. most of it still runs via candlepower and steam, with only the elite having electricity. most of the population is living in a manner that would be familiar to a Medieval serf, and are treated similarly as well.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: May 21, 2015, 05:16:32 am
content: I work with a girl who likes to go to North Korea every year for a vacation. No, she is not Korean, not even Asian. She loves it there. And yes, they have everything, lots of nice food and ridiculously fancy spas ...so those are not GPS jammers, just malfunctioning sauna heaters.If I understand physics correctly satellite signals are easy to jam because navigation satellites have to be at higher orbits, not to slow down and in sight and also are limited in on board power. How all nations or not all nations can change that? There are ridiculously expensive anti-jamming antennas, probably useless too. Those are phase shit arrays of 6-8 antennas designed to reject everything "not from above".

author: rs20
author_rank: Super Contributor
timestamp: May 21, 2015, 05:20:50 am
content: How can you possibly make unjammable (or even slightly jam-resistant) GPS? Surely the satellites are at a disadvantage, being at such a great distance from the receivers (compared to the jammers).Quote from: SeanB on April 17, 2015, 07:35:12 pmQuote from: Alexei.Polkhanov on May 21, 2015, 05:16:32 amJust to point out the obvious, these two statements are not contradictory. The former describes the majority, the latter describes the minority.

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: May 21, 2015, 05:50:19 am
content: Well, good active phase shift antennas certainly work pretty well against most of jammers. And of course lots of money to be made on that :-)http://www.spacedaily.com/reports/Raytheon_Awarded_Further_Jam_Resistant_GPS_Contract_999.htmlAs far as I know two approaches can help to resist jamming1. More directivity in receiving antenna, active or both active/passive.2. Broader spectrum - wide band communications with frequency hoping harder to jam. Most modern military radios use frequency hoping extensively.GPS has military channel which is much wider and while we are struggling trying to get signal in "urban canyon environment" military dumb asses enjoying 5 bars on their receivers I suspect.

author: johansen
author_rank: Super Contributor
timestamp: May 21, 2015, 07:16:56 am
content: NK is a sock puppet, ignore them.ask the deeper questions..

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2015, 09:00:20 am
content: Quote from: rs20 on May 21, 2015, 05:20:50 am...and using very limited power supplies.Satellites tend to be overhead. You can use very directional antennae.

author: LabSpokane
author_rank: Super Contributor
timestamp: May 21, 2015, 09:48:17 am
content: Quote from: Alexei.Polkhanov on May 21, 2015, 05:16:32 amThey're called "phase shit" because you shit yourself when you get the $20,000 price tag.

author: rs20
author_rank: Super Contributor
timestamp: May 21, 2015, 10:51:10 am
content: Quote from: Fungus on May 21, 2015, 09:00:20 amGPS satellites are flying all over the place. How can you use a very directional antenna when you have no idea where the GPS satellite is?Unless this phased array antenna cleverly knows where the satellites are at any given point in time, and moves its beam around to optimize the signal individually for each one... definitely feasible actually.

author: paulie
author_rank: Frequent Contributor
timestamp: May 21, 2015, 12:04:21 pm
content: Quote from: Alexei.Polkhanov on May 21, 2015, 05:16:32 amI think those phase "shit" antennas aren't worth a crap.All seriousness aside, it's quite easy to build yagi or multi-patch for pennies with thousand or even million to one noise rejection. Not effective if jammer is next door but very practical if coming from another country.

author: Monkeh
author_rank: Super Contributor
timestamp: May 21, 2015, 12:08:30 pm
content: Quote from: max666 on April 17, 2015, 04:11:02 pmActually, the current generations do not offer selective availability. And their military relies very heavily upon GPS, so..

author: Fungus
author_rank: Super Contributor
timestamp: May 21, 2015, 12:11:38 pm
content: Quote from: rs20 on May 21, 2015, 10:51:10 amYou can block anything that's within 20-30 degrees of horizon. The would shut out most stuff on the ground and leave plenty of sky to get a fix.To beat that they'd have to fly jamming aircraft but anybody flying over another country with hostile intent can be shot down, so...they wouldn't be able to do it for very long.

author: LaserSteve
author_rank: Super Contributor
timestamp: May 21, 2015, 03:08:18 pm
content: Shutting down LORAN in the first place was stupid. It did not save that much money. LORAN became a District of Columbia turf war, shutting down was not a good technical decision. LORAN is hard to jam, that was known. But its ability to penetrate buildings and provide a timing signal would have been beneficial to the "Internet of Things" for in building location services. As well as other uses. Especially things like precision farming. Think "drones", too.I hope they bring it back. The staffing costs were minimal, and the cost to make modern transmitters and timing systems, well insignificant in the long run.Cost to resurrect the towers, admittedly huge. Will it be an international resurrection, covering the Pacific and Canada, probably not. Yes, its a sole supplier issue, but that supplier is NOT one of the big defense contractors.Europe still uses their systems, and improved upon them.Steve

author: edavid
author_rank: Super Contributor
timestamp: May 21, 2015, 03:27:10 pm
content: Quote from: max666 on April 17, 2015, 04:11:02 pmFalse.http://www.gps.gov/support/faq/#off

author: LabSpokane
author_rank: Super Contributor
timestamp: May 21, 2015, 03:38:33 pm
content: Quote from: LaserSteve on May 21, 2015, 03:08:18 pmI have little faith in our congress-critters at this point. They just cut the civilian GPS budget to...hold on to your chair...$10M. If they think that little of the last backbone of aerial navigation, the odds for eLoran deployment are slim.http://www.insidegnss.com/node/4496And you're right, Loran was dirt cheap. I fuzzily recall that the total annual budget for Loran was in the low tens of millions.

author: SArepairman
author_rank: Frequent Contributor
timestamp: May 21, 2015, 06:20:36 pm
content: the more phase shift array antennas you have the greater directionality you have. You can sweep them extremely fast and probably track satellites and jammers with this technology in real time very easily.It's pretty much a radio telescope. How many antennas you got and how big it is determines the arc resolution you have in the sky. The military would undoutably shoot HARM/other transmitter seeking supersonic missiles at any jammer targets in a wartime environment anyway.http://en.wikipedia.org/wiki/AGM-88_HARMThey will program it (or its more advanced equivalents) to seek out signals that are characteristic of the jammer (possibly using advanced DSP techniques, finding a peculiar signature of the antenna, that will still show up with frequency hopping, stuff like transmitter phase noise or w/e).You only need this hardened system for however long it takes to get your forces into position for an attack, then electronic warfare people will make short work of any jammers. They will probably shoot missiles at anything that interferes with anything in a larger engagement, there will be a large task force dedicated to keeping communications clean and destroying all hostile sig int and EW capabilities. Modern army is severely hampered by a communication and command breakdown.Also very interesting if you look at hardened communications (in a nuclear environment)http://en.wikipedia.org/wiki/Project_West_FordI bet there are some missiles like this ready to go, just in case. But north korea is not exactly capable of disrupting global communications,maybe China, defiantly Russia. But in this case no matter how hard your receiver is you are screwed.

author: max666
author_rank: Frequent Contributor
timestamp: May 23, 2015, 12:37:47 am
content: Quote from: edavid on May 21, 2015, 03:27:10 pmI probably wasn't specific enough. No, they don't turn it off.They just add artificial errors to the C/A-code component of the GPS L1 signal on 1575,42 MHz, which is used for standard positioning service, while military receivers use an encrypted P(Y)-code transmitted both on L1 frequency and L2 frequency 1227,60 MHz. This reduces positioning accuracy to standard positioning, while military receivers are unaffected.And evidence of that is recorded by geodesist around the world, well at least by those close enough. FYI Austria is close enough to the Middle East to have been able to measure it

author: eliocor
author_rank: Unknown
timestamp: May 23, 2015, 05:54:38 am
content: Quote from: max666 onTodayat 00:37:47>I probably wasn't specific enough. No, they don't turn it off.They just add artificial errors to the C/A-code component of the GPS L1 signal on 1575,42 MHz, which is used for standard positioning service, while military receivers use an encrypted P(Y)-code transmitted both on L1 frequency and L2 frequency 1227,60 MHz. This reduces positioning accuracy to standard positioning, while military receivers are unaffected.And evidence of that is recorded by geodesist around the world, well at least by those close enough. FYI Austria is close enough to the Middle East to have been able to measure itIt was called Selective Availability (SA) but it is several years it was turned off:http://www.gps.gov/systems/gps/modernization/sa/Please can you state some papers which confirm what are you affirming?