Slashdot Mirror
Engineers Build Satellite Jammer
cencini writes: "According to this article, U.S. engineers developed a device for $7,500 which generated UHF signals strong enough to jam mobile GPS systems. My question is, couldn't you build something like that for less?!" Update: 04/20 02:42 by H : The folks at New Scientist wrote with the original article - the device actually blocks UHF signals, but can be modified for other bands.
Nobody uses GPS to target their nukes. US missiles use inertial/celestial navigation. As the warhead is in its ballistic arc, it takes images of the stars to determine if it's on target (stars are difficult to jam).
Cruise missiles carry a fairly small warhead. To really damage the building/bunker you need to be dead on target. Hitting the parking lot may scare the crap out of the occupants, but won't hurt them. US missiles also have backup navigation systems (the Tomahawk takes pictures of the ground and compares them to images downloaded prior to launch).
Even if they removed the error, it would seem unlikely that civilian units in the US would become more accurate since you could simply remove the error in the satellites over the Gulf.
It's been a long time since I worked on GPS (at Rockwell and some University contracts with NASA and a couple of DoD orgs.), but if my fading memory the P-code PN sequence was one week in length, not one month. There was also something in the stream of GPS data blocks that was encrypted using DES (Crap! Now I'll be down in the basement tonight looking through boxes for old copies of ION transactions). Receivers in those days were pretty much limited to positioning accuracies that you could get from tracking the C/A or P code itself. Newer designs were getting down to millimeter accuracies by tracking the L1 and L2 carrier frequencies and using that information to hone the position solution. AFAIK, anyone getting those kind of accuracies in a civilian receiver is probably using Differential GPS (as well as carrier tracking).
Also, I cannot see how this $7500 piece of equipment can be useful in supposedly jamming GPS signals. I suspect that what they're really doing is swamping the front ends of some of the cheaper civilian receivers that are in the vicinity of this low-cost transmitter. Even then, I would guess that the receiver might not lose lock unless it was engaged is some drastic manuevering and was close enough to the jammer. We looked at this back in the early '80s; it was damned difficult to jam a GPS receiver (well, the military ones anyway).
Err.. you don't need to responde to every single post, especially when you don't have anything to say.
Narf! GPS isn't a geosynch system, it is a high LEO system. Turning off the "error" would involve switching the system as it transitioned past the horizon of the gulf.
You said:
"Because in the case of the Chinese Embassy
we hit exactly what we were aiming for
(+/-1cm). Unfortunatly what we were aiming
for was the wrong target."
Seems like you have bought the entire "intel screwed up" theory stock, hook and barrel. Everybody knew that we WANTED to hit the Chinese embassy. It's the RIGHT target.
Those intel guys who were sacked or gotten "warnings" are fallguys. Their only fault is that they have become the scapegoats for a political decision that went sour.
Muchas Gracias, Señor Edward Snowden !
I really miss the days when moderators had a sense of humor. :-(
I see even classic Slashdot is now pretty much unusable on dial up anymore.
The article was a little vague as to whether we're talking about screwing up GPS receivers here on earth or screwing up the actual orbiting transmitters themselves.
I assume that interfering with reception of the GPS signal within a limited area would be considerably less of a technological and financial challenge, but if you can stick this thing in a truck or jeep and take it where it's needed, wouldn't it be just as easy to carry weapons instead and inflict enough damage to disable whatever you wanted to jam?
That way, you're in and out quickly instead of hanging around waiting to get shot or captured, because anything this would be used against wouldn't be sitting around unguarded and unprotected.
I see even classic Slashdot is now pretty much unusable on dial up anymore.
This post is as daft as whoever moderated it 'insightful'. Two really serious flaws in your argument:
I take it that English is not your first language. Failing which, I take it that rationality is not your favoured reaction.
Hamish
"Wise men talk because they have something to say; fools, because they have to say something" - Plato
Because in the case of the Chinese Embassy we hit exactly what we were aiming for (+/-1cm). Unfortunatly what we were aiming for was the wrong target. GPS guided missiles are only as accurate as the intel they are fired with. If you don't know where the enemy is you can't hit them.
If troops had been sent in to take out the embassy they would have been able to
1. See it was the wrong target before it was attacked (Provided they were informed what the target was).
2. Radio back to command and confirm that this is what they wanted to do.
Minne-snow-da: Winter is comming...
You can get the parts to build somthing like this at the Dayton Hamfest.
--fatboy
There are some pretty astounding military repercussions of this device (which explains the price - it's not a product aimed at pranksters). Since Most modern military weapons (guided missiles, SAMs, SSMs, fighter jets, etc) are GPS guided, land bases and ships can easily defend themselves by switching on a GPS jammer. A $7500 device to defeat million-dollar technology is a very good investment. The American military is particularly dependent on GPS tech (having invented it, they jumped on the bandwagon with more vigour) so this bad news for their fleet of GPS navigators.
Ok, so you don't tailgate when you switch on so you can swerve around the guy when he eats the guardrail. Besides, the guy is already weaving due to USING the phone.
see above on the crash part. I just wish there was something I could do about the people I see reading the paper with two hands and driving with their knees. I commute an hour each way and the stuff that goes on is insane. I can almost believe the joke about the guy that puts it on cruise control and then climbs in the back seat to go through his briefcase. When I read the article on the japanese jammers I contacted the company about them but the frequencies we use are different than theirs. I even thought about the EMP gun in Cryptonomicon 8^)
Very similar to the japanese version I read about. They were marketing theirs towards movie theaters. Were you able to get a price? The email info request form never completed/submitted.
Cant wait to see this one in my next meeting... Ill take mine to the movies too http://www.cguard.com/English/latests/index.html
You are correct. Hands-free units were no more safe than normal hands-on units. The danger arises from the distraction of the call. Phone conversation is worse than person to person conversations in the car because the lack of visual context (gesture, expressions, etc.) requires greater attention to the aural cues. On the phone you actually have to concentrate more attention on hearing at the expense of seeing. Within the car listening is supplemented by seeing, even if its limited to peripheral vision. And I imagine you'd find that drivers have to talk more on the phone than they do in a driver to passenger converstion. (Actually the study avoided making any conclusions about the nature of the increased risk, but I'm less restrained in my opinions!)
An altitude offset wouldn't be a big problem. The warhead would use a contact or radar fuze to control the timing of the detonation.
Mea navis aericumbens anguillis abundat
Yes, if you were attacking a hardened missile silo.
Mea navis aericumbens anguillis abundat
It is not clear to me why anyone in the goverment thinks that a terrorist wouldn't just run a binary editor on the firmware and change the limits to some number 100 times larger. It isn't that simple. Algorithms that work at slow speeds may not work reliably or accurately at high speeds. Getting accurate results might require new firmware and a faster CPU.
Mea navis aericumbens anguillis abundat
This wouldn't be surprising; some military units in the field during Desert Storm were using commercial (handheld) GPS units, not military ones. SAS were using small Magellan units, I'd put money on them being commercial ones. OTOH, ground pounders don't necessarily need the pinpoint accuracy that the fine folks moving at 500 mph over the desert do.
(Yeah I know I misspelled it.)
We are expected to believe that these things cost a lot because they are very "technical" and therefore costly. The government is just as dumb so the companies get to rape us blind with huge markups. Oh well. By now we should be used to it.
<SIG>
I think I lost my work ethic while surfing the web. If you find it, please email it to crispy@crotch.caltech.edu.
</SIG>
My sig has a broken link in it.
hehe... It's not quite midnight here on the Pacific Coast but I got started early. I am going to wake and bake tomorrow morning in celebration. Too bad we can't just make this a national holliday.
<SIG>
I think I lost my work ethic while surfing the web. If you find it, please email it to crispy@crotch.caltech.edu.
</SIG>
My sig has a broken link in it.
True, mid-air nuclear blasts are more destructive (I guess it gives a pressure wave enough space to form), but I was thinking more along the lines of "conventional" weapons, rather than nukes.
:-)
With a non-nuclear missile, you really do need to be pretty accurate if you want to be sure of destroying the target, unless you throw lots of explosives at it, and I was kind of assuming that it was this type of missile that the GPS offset was designed to hinder. After all, with the exception of hardened targets, detonating a nuke 200 feet or 500 feet above the target isn't going to make a great deal of difference; either way, there isn't going to be much of it left
Cheers,
Tim
It's official. Most of you are morons.
Hehe - the only trouble with your idea is that it'll probably cause more crashes than it prevents, as your victims flap about wondering what's happened to their 'phones :-)
It certainly has merit, though - a few times I've been on a bus only to find the driver is using his mobile - taking your own life (and that of anyone you hit) into your own hands is one thing, but the lives of a couple of dozen passengers? Talk about irresponsible...
Cheers,
Tim
It's official. Most of you are morons.
Okay, if the offset is in altitude, not the position on the ground, then couldn't you just target your missile for a spot above the target, then guide it down at it?
(Don't think "along, then down", think "up, arcing over, and down", kinda like a mortar with last minute targetting correction)
Cheers,
Tim
It's official. Most of you are morons.
Yes, I think so. /.
I will have to get to work on this right away.
Driving through downtown could be much fun with one of these. Hmmm.. maybe follow an out of state Jaguar or Seville around for a while. Heck, no need for it to be out of state, everyone gets lost anyway.
Yes, oh, and if someone builds one before I, they should submit it to
010110000010110101010100011110010111000001100101
Well, pete-classic, there goes your TS.
Better luck next time.
Don't sweat too much, though. You haven't let anything slip that wasn't obvious already. Just remember to preview in the future.
********* sig: If you don't like the law, get filthy stinking rich, and buy a better one.
Ok i have a two way radio modified to transmit whereever it can hear (VHF, UHF, SHF) which covers the UHF band. I only spent 250 on this radio. It does 5W out and is portable. Now, couldnt they make a GPS jammer for less?
All of this is, of course, IMNSHO. Cheers, Elmo
"Nobody uses GPS to target their nukes. US missiles use inertial/celestial navigation. As the warhead is in its ballistic arc, it takes images of the stars to determine if it's on target (stars are difficult to jam). "
However, AFAIK, missle subs use it to determine where THEY are in order to give launching coordinates to the missles. This number is important for hard target kills.
"All those tubes and wires and careful notes!"
"All those tubes and wires and careful notes!"
Do you remember KARR? What did KARR stand for, if KITT was Knight Industries Two Thousand?
The Russians also have their own version of GPS - called Glonass. If I remember correctly, Trimble sells a dual-mode system.
Also, one of the previous posters referred to using differential GPS. This is publicly available only in coastal areas and is supplied by the Coast Guard in addition to Loran. It's not available in the central US unless you set up your own DGPS station. It's typically provided by an add-on module to you CA code GPS receiver and operates by time-correcting the incoming satellite signals.
-- Improve Windows - Buy a Mac!
Now, for all of those unenlightened(?) people out there, who think they know about GPS but don't, here are some facts.
Firstly, the the comment about the P-code and C/A-code is correct. And yes, there is a thing called selective availabilty, so therefore with a single gps receiver, you can't get any better than about 100m [1].
Secondly, Differential GPS at sub-centimetre accuracies requires post-processing, you can't do it on the fly. It you want real-time kinematic, or on the fly calculations, the best you will be able to get is around 2m.
Thirdly, for DGPS to work, it doesn't need to be coastal, it needs a DGPS set up so that the same sattelites are being received by both a static and the roving receivers.[2] The static has a known location, and the errors from the ionosphere will be around about the same, and then a vector is calculated from the measurements. To get subcentimetre accuracy, you need to sit there for 2 epochs, i.e., 20 secs, so that an accurate position is gained. This is done by post processing. When the roving receiver is moving, then won't be as accurate.
Fourthly, the error determination in height is less accurate than that in plan due to the nature of the network involved. Ask any surveyor about survey networks and they will tell you the same thing. This is simply due to the way that errors are propogated.
Fifthly, to gain a subcentimetre accuray, there needs to be five, yes, five sattelites visible, so there is an overdetermination of the solution, and therefore, the least squares solution gives better accuracy. They should also be 15 degrees above the horizon, not 5 degrees, to help eliminate errors.
Sixthly, to get subcentimetre accuracies you need to set up a baseline, which generally takes 10 - 15 minutes, so that errors can be determined. If at any time, the number of sattelites able to be viewed drop below 5, or you lose lock on a sattelite, the baseline needs to reestablished.
And last but not least, the time at which these readings are taken needs to be taken into consideration, as you don't have enough sattelites overhead all the time.
[1] The sooner that the US and UK move to metric systems, is they day that people all over the world rejoice that they no longer have to use antiquated methods. And this from countries that are supposed to be ahead of the rest of the world.... Ha ha ha ha ....
[2] The Australian state of Victoria, and Japan are two examples where the government has set up GPS networks around the country for differential use. In Australia, corrections can be picked up on a sideband of a radio station that is nationwide (JJJ). Japan has it set up for it's earthquake monitoring. Other places such as some South American countries are moving to setting things like this up.
I don't know, I usually have a hard time finding which way is north at night and such because (1) in the big cities you can't see too many stars, and (2)in some parts of this beloved town the street signs are fair game for "collectors"...
I ususally know where I'm going, but it'd be nice to not have to get a paper map out and have to see where you're going to have to turn while you're trying to cross four lanes of heavy traffic.
this is just a placeholder till i send back my real sig from the future.
Not true. There are also dual frequency civ GPS units available (Trimble, Leica, Javad, etc). This, combined with DGPS (differential) and RTK (Real Time Kinematic) can result in SUB centimeter accuracies every 2 seconds. Of course, they ain't cheap (>$40k) but if you need that sort of thing. JL
Its not like it'll hurt my karma that much, and to be honest, I just forgot to check the 'post anon button' when I submitted.
You are free to think whatever you want, AC
ReadThe ReflectionEngine, a cyberpunk style n
No, the error is always in your current location. Your fishing boat will only know within 30 feet where it is, and you have to correct for errors due to wind and current anyway. As you're going across the lake you just follow the arrow to end up at the destination you chose, always only knowing your location within 30 feet. If you're headed for a buoy or dock it's easy enough for you to manually steer to your destination.
> The problem with cell phones [is] that most people don't have hands free sets[....]
I could be wrong, but I seem to recall that the news item claiming that mixing cell phones with driving was similar to alcohol and driving also included hands-free models in the barrage.
I hope that there will be solid studies done on driving and cell phones (with and without hands). Maybe something, other than abstinence, will come up that lessens the risks.
Really, You're saying that there was actual MONEY involved (like Fed. Reserve Notes, or Silver Coin?) and not just some pumped up estimates of software development costs?
IIRC, I didn't see anything related to hard currency, could you perhaps provide a reference?
peace, Mike
Technology -- No Place For Wimps! Grateful Dead and Jerry Garcia Chatroom -- http://www.wemissjerry.org
and management would say something about its "synergistic imperviousness that leverages the paradigm of placement empowerment"...
"It's tough to be bilingual when you get hit in the head."
>Where would this world be if all these transmission that we rely upon went down 10 times a day?
;-)
Never used a dialup or a cable modem, have you?
"It's tough to be bilingual when you get hit in the head."
The reason that the signal was not mudged for the Gulf War was becuase so many units (I think mostly US Army) had to use off-tht-shelf civilian GPS. The military models were not available in quantity.
No big mystery, it was a simple problem and a simple solution.
Eve Fairbanks says I drive a hybrid!LOL
If you are jamming a whole area, like the "bubble" the original article speaks of, you are jamming EVERYBODY in the bubble, including yourself.
This has much greater implications for civilian fleets than it does for the military.
Eve Fairbanks says I drive a hybrid!LOL
Is it just me, or when using a GPS receiver, when you are moving at over 5mph it says that it is indeed accurate? When still, the position varies by a few feet in every direction. This suggests that it can correct the offset at speed. I would guess that this is why the gov't needs to jam it instead of increase the offset. Anyone correct me, please?
> The really scary thing about this jamming is
> that commercial airliners are starting to use
> GPS signals for navigation and bad weather
> landing.
I don't think so; according to my friend who's dad
is an airline pilot (so, like authoritative) the
airlines are still worried the US government will
just get bored and turn GPS off...
We've had so many articles on patents already. The issue has been beaten to death. Yes, the concept is /good/. The implementation is /bad/. We have a broken system. Patent duration needs to be tied to the speed of the market/industry the patent is for. E.g., HOW long as Unisys had GIF? How much innovation by them has that engendered? It seems to me software patents should have a short duration, maybe 1-3 years. Patents on business models or how many times to click to buy something I just can't understand.
It's 10 PM. Do you know if you're un-American?
--
This is not my sandwich.
Are there inertial navigation systems that accurate?
--
This is not my sandwich.
Probably. But since the only people who "should" have one are the gubment, no matter how cheaply I can make them, I'm still gonna paint 'em olive green and sell them for ninety thousand dollars...
--
This is not my sandwich.
I love hearing all the self-important people who are talking out of their asses by saying...
Hi, I have no clue how to build a military GPS jammer, or even really how GPS works, but you know, the US is getting cheated out of my hard-earned taxpayer money by getting overcharged for building such a simple device. I guess it must be due to the general imbecility of government workers.
*snicker*
telnet://bbs.ufies.org
Trade Wars Lives
Light a fire for a man and he'll be warm for a day. Light a man on fire and he'll be warm for the rest of his life.
I would find a device that jams police RADAR much more effective, though having a microwave dish attached to the front or top of my car would make me an obvious target.
..No officer, I was trying to download my e-mail...
--
it's a sig, wtf?
The answer is August 6th and August 9th 1945.
Twice != never.
You owe the Oracle 100,000 origami cranes.
k.
"In spite of everything, I still believe that people are really good at heart." - Anne Frank
For instance, my favorite would be Orange Marmalade. Some people would argue strawberry would be the best choice, but only one man would dare give you the raspberry....
Learn from your parents' mistakes: use birth control.
Sure...lets jam all the GPS satellites in our ever-continuing quest to make ourselves more lost in the universe than we already are. Seems like a bit of a backwards step to me. I'd think they'd be working on ways to keep better track of where people are.
Of course, GPS has always had enormous "Big Brother" potential. Add some unwanted GPS implants into the mix and we might just need a jamming device of some sort to retain our freedom.
"The majority of the stupid is invincible and guaranteed for all time. The terror of their tyranny, however, is allev
Everybody needs to have their cut - that's what the whole corporate culture is built on.
-- "To ask a question is to show ignorance; Not to ask a question means you'll remain ignorant."
No, most nuclear weapons do the most damage when detonated off the ground. This allows much more surface area of the heat and pressure to hit a certain target, instead of re-directing some of it.Yes I know it will still blow the hell of of things :) but mid air detonation is the most damaging. From what I understand of nuclear explosions if they are detonated near the ground they blast radius will increase and destroy more buildings/people above ground. A mid air (50 to 250 feet I think) will cause more of a crater and destroy fortified underground targets.
Re:What they don't tell you about GPS... (Score:2)
by CMonk on 12:45 AM April 20th, 2000 EST (#60)
(User Info)
I would say that the resolution that consumer grade GPS provides is more than enough to allow an ICBM with a nuclear bomb to be more than effective. The GPS drift that the consumer devices are subject to is much more likely there to help prevent accurate conventional weapon attacks.
Actually, the main reason for the existance of the better grade GPS is for Ohio class missile submarines. Believe it or not, those few dozen extra meters of resolution come into play for a tactic known as "counterforce".
While that 100 meter circle your civilian GPS puts you in would be accurate enough to, say, launch a one megaton warhead at New York City, with a reasonable (i.e. 100%) chance of wiping it off the map, it's NOT enough to destroy a buried, hardened silo containing a land-based ICBM.
On the other hand, if you know EXACTLY where you are on the earth, you can drop your 500kt warhead into a pickle barrel from half a world away, and destroy the land-based missile, thus keeping yet one more warhead from raining down on your country.
Although, it is also as you point out above. Cruise missile + GPS = Conventional explosive litterally going through the front door.
What part of "shall not be infringed" is so hard to understand?
Given the amount of time that government systems are out of date by, could it have been a pentium floating point error?
Grins and giggles,
DB
GPS guided missiles are only as accurate
:)
as the intel they are fired with
So if i look hard enough, i will see Intel Inside on the missle?
The article gives the impression that they started with an empty "junkbox"--buying every part needed. Also the completeness of the individual building blocks in the system would greatly influence the total price. It's the old buy vs build thing. Heck, they could have dropped $1200 on the motor-generator set alone if they bought it before the Y2K non-event!
True, but no nuclear power in their right mind is going to count on GPS to handle fine weapon guidance. The only people likely to pull such a stunt would be perhaps Taiwan, in the case of Chinese agression, or an independant terrorist group. For either, it's a one or two shot deal, and taking out NORAD or a couple of silos isn't likely to be high on their agenda. They're gunning for mass destruction of civilian targets!
.sig: Now legally binding!
GPS is such a vital tool in land surveying that I fear having to relocate those pins scattered all though the US, and can you imagine the inaccuracies that this would cause? How far would it set us back? Think of the
NOAA experiment that found the Washington Monument to be a different height then previously measured. (new height is
here)
Wheeeee
Hmm, don't know how that happened. I did a preview, but I did not look very closely so make sure that it did not put my nick on it.
;-)
My TS expired a couple of months ago anyway
-Pete
the way it works is this:
each sattelite broadcasts a signal wich contains its ID and it's idea of the time.
your receiver MUST track at least 4 sattelites to provide useful info.
your receiver grabs a frame from each of the four satellites simultaneously, and then performs basic trigonometry using the differences between the four time hacks and the known ephemeri of the sattelites.
so, with 4 satellites, you can get a precise 3D location, with the same accuracy in all dimensions.
The difference between Theory and Practice is greater in Practice than in Theory.
The site's in South Africa. Is it that, or the /. effect, causing it to load so slowly?
Here's the text so that poor server can rest a little:
Home-built device can cause air chaos
April 19 2000 at 11:35PM
Paris - The Global Positioning System (GPS), the space network that helps aircraft, ships and
explorers to navigate, can be jammed using cheap equipment bought from stores and
knowledge acquired on the Internet, New Scientist says.
A United States air force team, dubbed the Space Aggressor Squadron, was set up to look for
weak spots in satellite communications and navigation systems, the British scientific weekly
says in next Saturday's issue.
Playing the part of a potential enemy, two rookie engineers were able to build a satellite
jammer by downloading information from the Internet and purchasing equipment from home
improvement stores and electronics "swap meets".
For only $7 500 (about R49 500), they built a device using a UHF signal amplifier and noise
generator, copper tubing which acted as an aerial, with desultory pieces of wood and plastic
piping. A petrol-driven electricity generator provided the power.
Loaded into a pickup truck, the device was "an effective mobile jammer", capable of blocking
satellite antennas or military UHF receivers, it says.
"Different components could be used to jam other frequencies, such as that of the Global
Positioning System," it adds.
The GPS uses signals from several satellites in an orbiting constellation to triangulate a
position, with accuracy down to a few metres.
It is becoming so prevalent that there are now GPS systems being incorporated in
top-of-the-range cars, as well as GPS wristwatches.
John Pike, director of space policy at the Federation of American Scientists, told the
magazine that it was "simple" to jam the GPS, because the satellite signal is weak.
But he believed that the latest generation of global communications satellites would be
immune to similar home-built equipment, as they are "heroically resistant to jamming". -
Sapa-AFP
The navy's been able to jam GPS near ships since at least the gulf war. I suppose it would be bad for the enemy to use our own GPS sat's to guide a missile into us. Also the DoD has their finger on the button and can turn it off whenever they want, causing some controversy in the aviation community. Plus the whole SA error added in the public use channel too.
it's actually more like 300 meters. Most of the consumer GPS' don't have very good clocks in them adding to the error a quite a bit. If I remember right .001 of a second is 1800 meters or miles error (I can't remember which, and don't feel like going to get my notes)
The error is in fact controlled by the sats as follows: Each satelite has an atomic clock. They transmit the time continuously. At any given time a receiver can pick up the signal from three satelites. Because the distance to the satelites is diffrent, the amount of time it takes the signal to reach the receiver is difrent for each satelite and therefore the times are off by hundredths of seconds. The calculation of where you are is based on the differences in the time it takes to receive the 3 signals, and the resulting clock drift.
The "correct" time is DES encrypted by the satellite and only the military grade receivers can decode it. A special algorithm is used on the civilian version which shifts the time going out in the clear a varying amount. This amount leads to the reduced accuracy of the civilian version.
On the ground, this inacurracy can be corrected with Differntial GPS, which communicates with a fixed receiver at a known position. The error can then be calculated by subtracting the GPS position at the fixed receiver from the known actual position of the fixed receiver. This error correction can then be applied to the GPS position calculated on the mobile receiver.
If you really did know about this, you would have used the correct units
If my call is important, why am I talking to a recording?
And I thought putting "Catcher in the Rye" on my library card was risky.
"Well, good luck finding a judge that doesn't run a bestiality site."
This technology should be adopted to work with frequencies for cell phones. Put a short range frequency blocker in every restaurant, moviie theater, and bar, and I'll be happy! Damn people talking on their cell phones while eating dinner... man that pisses me off! At least people should have the courtesy to take their conversation outside, or in the lobby.
There is nothing easier to do direction finding on than someone trying to jam you. Perhaps the jamming resistance isn't electronic at all, but manifests itself in the form a Tomahawk missile cruising in on you.
Or for you conspiracy nuts, maybe 4 guys in black suits will just show up at your door and put you someplace you where you won't be conducting any more jamming exercises.
t
.
No off-the shelf parts
Enclosure machined from a solid block of 7075 Aluminium instead of a premade sheetmetal box for $12.
Bobbin cores for magnetics are machined out of rod stock in one piece.
Etc.
All I can think of is the cost of the truck is included, or they included the costs of the trial versions before they hit upon the best combination. The generator might be expensive in france, too... Here in the usa, gensets are cheap used, as people are de-Y2-kay-ing themselves. I would think a tesla coil with an antenna on it, for example, whould jam everything for cheap, but maybe it's so obvious you could not hide it for long..
Your wallet stays open. Our source remains closed. We are MSFT
But, for more strategic nuking, like killing NORAD, White Mountain in Virginia, UN bunkers, the Politburo Defense Bunker, etc. you want to penetrate, and that takes impact and accuracy.
What can I say, I've got a morbid fascination with instruments of war.
IP is just rude.
Is there any torture so subl
Portable GPS jamming is one less reason to buy an I-opener, as if the store you bought it from giving away your credit card number wasn't a good enough reason.
-
You're right. I'm wrong.
It is spread spectrum. The spectrum is just very narrow.
Geosynchronous? Think again.
or... see for yourself:
http://sirius.chinalake.navy.mil/satpred/
Now, I am not a EE, much less a DSP/GPS specialist, but from my knowledge of the system I am guessing that: a) the system described above won't be much use against fast-moving airborne GPS (fighters)...
Generally, it's assumed that radio waves travel at the speed of light. The speed of a fast moving aircraft isn't relevant.
Look at it this way.
1. The satellites are very high.
2. The antenna is placed on top of the vehicle.
3. If your jammer is on the ground, the jamming signal can't pass through an aircraft to get to the receiving antenna.
If you don't belive that, put your GPS receiver underneath your car and see how well it works.
You can't jam the transmitting space vehicle. You can only jam the receiver on earth.
Better yet, here's a picture of the ground track:
http://www.utexas.ed u/depts/grg/gcraft/notes/gps/gif/svs27.gif
Even more than just a serious nuisance. I'm not sure if they are actually using it yet, but years ago, the F.A.A. was investigating GPS for use with instrument landing systems on commercial aircraft. As posted elsewhere in this thread by hpa, the F.A.A. issues NOTAMs whenever the military is testing GPS jammers. A hazard to navigation is much more than just a nuisance.
Power is not the issue.
The amount of energy reaching the earth from a GPS satellite is roughly equivalent to the amount of energy you would receive from a night lite in Chicago... while standing in Los Angeles.
...is that you jam the receiver, not the transmitter. Basically, you have to produce a signal that is stronger that the one being received by the handheld GPS unit. Of course, this is only going to take out the GPS capability of a relatively small area.
Of course, if you want to take out the whole system, then you have to block out the transmissions to all the satellites, and that is going to be expensive. There are too many of them, and they are moving in their orbits. I think a better idea is to build a death laser and shoot the damned things down from the sky.
I do what the voices on my console tell me to do.
That's a valid point, nukes don't have to be that accurate, unless you're trying to blow an underground bunker such as NORAD.
You could use this accuracy not only for conventional weapons, but for chemical and biological. This gives you the capability to conduct deep attacks into the enemy's support and logistics areas. That really limits his ability to wage war, since long-term combat is based on resupply and transportation.
Just something to think about....
I do what the voices on my console tell me to do.
It's a good military phrase, something you can way while you beat on your chest.
If they were geeks, they would say something like "dynamic robustness".
I do what the voices on my console tell me to do.
"Hm. Anyone have a simple explanation of processing gain? I'm not enough of an RF person."
I'm not a big radio guy, but I think it's like putting a filter on to get rid of the noise.
I do what the voices on my console tell me to do.
I've always thought that, unless you're in the middle of the ocean or the flatest desert, you should be able to find your location with a good topo map. I don't even think compasses are necessary.
I knew this one guy who turned on his GPS everywhere he went. After about a week, he ran out of battery juice and was totally lost.
I do what the voices on my console tell me to do.
It is true that you could probably build one, but as one poster pointed out, you'd have to crank out a lot of power over a broad frequency spectrum. This of course makes the device *very* easy to locate using very simple directional antennae. Turn one of these things on and wait for the local FCC enforcer to show up on your doorstep (as well as an angry mob of people who have interference on their cell phones, cordless phones, and anything else that could easily pick up broadband interference). How does a warning followed by a $15k or greater fine grab you?
Luckilly, these days, we got satelite...
You have satellite until someone decides to build one of these jammers! Then you get to see Mr. T try to act.
Anyone wish that Knight Rider, A-Team, and/or Airwolf did a cross-over show? You know like those Hardy Boy/Nancy Drew crossover books? It would be cool to see the Knight Rider team (Go Michael Knight!) and team Airwolf (Dominic Santini forever!) fighting evil together. Maybe even having the A-Team getting ouy their blow torches and welding them together into some sort of flying KITT.
Oh, and for those of you lucky enough to have a tv station playing airwolf, you have to play the stock footage drinking game. Everytime they show a clip of Airwolf with it's bottom mounted rockets retracted when they are supposed to be extended, drink. Basically anytime some accessory on airwolf inexplicably retracts and extends between shots. It's really quite fun. :)
I have my "stuff"; compass (old mil style), map (I like klicks), landmarks (the park). It's time to jam, crank it up. Oh, I didn't mean heavy metal music from the 80s -- what the hell add it to the signal for fun. -d
for civilian purposes not many, you could annoy people by jamming whatever GPS systems they had w/ short rapid transmissions, so they get part of the transmission, but not all; which generally is more annoying it has more purpose for use in the military, b/c GPS is a form of comms, and the military likes to be able to jamm all forms of comms, leaving their enemies blind, deaf and stupid
"In the future, computer-using men will be the sexiest males." -- Scott Adams, "The Dilbert Future"
Seth
$5 / month hosted VPS on linux = awesome!
Seth
$5 / month hosted VPS on linux = awesome!
>Radios are only 50 years old.
Closer to 88 years for marine/military radio, and 72 for commercial AM.
"That ain't the way _I_ heered it, sonny!" - The Old Man on Fibber McGee, considerably more than 50 years ago.
"Ain't no right way to do a wrong thing."
When was the last time the United States used a nuclear device to force a country into submission or to the negotiating table? The answer is never. The GPS system is not crucial to the launching and flight of ICBMs, as the US Air Force/Space Command had the system working without GPS for decades before its invention. The point I'm trying to make is that GPS, when it comes to bombing, was intended for precise tactical warfare such as the use of Tomahawk Cruise Missles. As witnessed in Bahgdad and in Belgrade, 100m can mean the difference between hitting the intended target and collateral damage as sensitive as a neutral foreign embassy or civilian hospital. Today's warfare is not about Mutal Assured Destruction with nuclear devices, but precision with cruise missles, and this is where even a 10m margin of error as compared to 100m in the Global Positioning System is crucial to military applications.
-- "I can't tell the future, I just work there." -- The Doctor
Even if someone does jam the GPS signals to stop terrorists from flying in a stolen/hijacked cruise missile into say, the Pentagon, couldn't they manually control it using a Sony PlayStation 2, which is now meant to be powerful enough as weapons control platform and has to be export-regulated by the Japanese government? = P
-- "I can't tell the future, I just work there." -- The Doctor
i prefer to call it Natural Selection.
the population does need a little thinning...
More alarming than jamming GPS is the fact that the Naval Academy at Anapolis dropped the requirement to study celestial navigation. Very bad idea! You don't need to be a genius to figure out that when the enemy takes out your GPS satellites, you're on your own.
i supose the military wants to jam the GPSs of the "enemy"? wtf?!?!
oh yeah.. 1st?
--DarthVdr
"the only 'evil hackers' are the ones at mircoSoft..."--me
--DV
--DV
In this day it is safer to be a ninja than a samurai
Whats the point of all this discussion of Jamming? You have a device that interferes with GPS signals, so what? Its only a transmitter. Its easy enough to build a device that finds a transmitter ( a directional reciever) its easy enough to build a device that homes in on a transmission and destroys it. Missiles are used to destroy RADAR instilations by doing exactly this. The bigger and more powerfull the jammer, the easier it is to destroy! The smaller, the less there is to worry about. This device is simply an nusiance, dont get all excited about the prospect of blocking missiles that use GPS, its too easy to destroy the jammers before firing off the missile!
Jeez,
Gotta Love South-Africa!
That show was prime-time tv. when I was litle!
And now that I am big prime time is filled with Knight Rider and A Team ReRuns.
The last show to be bought by the SABC must have been the first season of Beverly Hills 90210, in 1997!.
Luckilly, these days, we got satelite...
mmmm. MTV !
---Sucky Sig To Follow---
"Semper in excretum set alta variant"
If this be offtopic I ask thy forgiveness most solemnly, but that news site is in South-Africa, So I am wondering if it was posted by a South-African, I mean most American's don't even know what country .za is, no offense.
NE-Ways, If you or anybody else here is in south-africa, the Pretoria LUG has been discussing the really bad performance of South-Africa at counter.li.org (nu. 74) I do not believe we lack users, just that we don't register...
Ok, before I post again I'll make sure I have something to say.
"Semper in excretum set alta variant"
Instead of just jamming the signals, what if you could fool them into giving false readings...
:)
Think of the possibilities
From day one all engineers are tought how to maximize and to minimize. Maximize performance, minimize cost, maximize usefulness, minimize harm infliction, maximize life-time, minimize energy consumption...
However, in the given economy such ingenuity becomes less and less profitable for the large corporations due to decrease of demand over time, when the market is saturated with first grade merchandize.
That is why engineers had to reverse their positions and now what they have to do is to balance certain aspects of the product in a way as to assert maximum profit for the corporation over time.
It was not always like that, it's the conveyer belt that changed our understanding of mass production.
Modern engineer does something like the following:
Minimize product life-time & minimize cost;
Maximize product life-time & maximize price!
Maximize performance & maximize price!
Maximize usefulness & maximize price!
Minimize price and minimize performance
Minimize price and minimize life-time.
My grandfather made clothing, he was a master, he would make the best closing he could.
Today engineers design everything and the closing they make will either be extremely expensive or will wear out in a matter of days. This is absolutely unnecessary correlation between the performance and the price, since it is basically easier to build a good product than to design it in a special way so that it will fall apart after a week but that's what's going on.
In this case the performance is probably maximized and so is the price.
You can't handle the truth.
That was the most disturbing thing I've heard all week. Good job!
Network Security: It always comes down to a big guy with a gun.
Yeah but theirs is blue.
:wq
Sign me up for the cellphone jammer. I want
to declare the 100 foot radius around myself
to be "cellphone free".
Perhaps one problem is that cellphones use different frequencies, though perhaps all within a certain band. To get around this, perhaps one could build a "reflector" which simply reflects back the incoming waves, BUT with a 180 degree phase shift, which then destructively interferes with the original waves.
Surely if someone was a true luddite then they would be too frightened of techy jamming equipment to actually use it.
I can't be sure of this though, I've never actually been to Lud.
Sir, my hat is off to you, that was the best reply to one of those idiotic first post messages that I've ever seen. (the included link was beautiful!)
Don't try to KNOW everything, just know how to FIND it.
Hemos says "[...]the device actually blocks UHF signals, but can be modified for other bands." My question is, when can I get one to block all cell phones within a 100 yard radius of my truck while on the highway? Cell phone operators are nearly as impaired on the road as the heavily inebreated, yet we have no legal recourse with which to protect ourselves on the road. I think the first guy to come up with a decent cell phone jammer will become an instant hero.
Screw Micro$oft.
I was looking for this before but couldn't find it. A much more detailed discussion of spread spectrum modulation (with pictures :-)
http://sss-mag.com/primer.html#c
Wow... Years without a single post. And now two in less than an hour
Trimble has a really good "Intro to GPS" Tutorial which covers how pseudo-random codes are used. The entire tutorial is here:
http://www.trimble.com/gps/fsectio ns/aa_f3.htm
while the section on pseudo-random codes is here: /aa_hw3
http://www.trimble.com/gps/howworks
It even discusses jamming (briefly).
i have an old electric razor that would jam anything.... esp TV.
The main reason why non nato countries do not have GPS capacibilities at all is that you can chance the coding, making it impossible to non US forces (read NATO forces on general) read the signal.. or you can change the coding, making offset of 100 miles, or revise whole map for GPS recievers of certain coding.
And the GPS system control codes are in the hands of US. So in the times of war only US, and aligned forces may trust in GPS systems.
Then again why was gps offset chanced in persian gulf. Saddams forces had a lot of US army gear, becouse it was the US gov. to promote the junta in the first place. There was no offset in Persian gulf, for the readjusted recievers.
So where do you need the jammer anyhow, if you can ban GPS users at your whim.
Parents Against Kuro5hin
You clearly underestimate the value of annoying the military and doing illegal activities... :)
Using civilian frequencies, Differential GPS can obtain accuracies of 1 to 2 centimeters. I even know of a company that can land a plane using differential GPS. Sort of makes having separate civilian and military GPS frequencies moot, eh? patrick
from the now-no-one-will-know-where-i-am dept.
Shouldn't it be:
from the now-not-even-i-know-where-i-am dept?
On another note, they should change the Preview button text to Strip all the html tags from your post source.
Not only that, but if you're really lost at night, stopping, turning on a light, and looking at a map in your car is like saying "Please carjack/rob/kidnap/rape me."
Yes, it should be possible to build a jammer for the GPS signal. However, it is specifically designed to thwart jamming attempts, because, as it says in the article, the signal is relatively low power, but uses some really neat techniques, all rolled up into something called "anti-spoofing" to avoid jamming.
It is, in fact, much harder to jam the GPS signal than it is to jam communication satellite signals.
Yes, in theory, you can jam it. But in order to do so, you need to be cranking out a *lot* of power (since the signal is spread-spectrum), and even if you have that power, you're only going to jam GPS receivers in the immediate area (remember the inverse square law?).
OK - so perhaps they can jam all GPS signals within say 100 meters of their location. Considering the GPS system was designed to allow ballistic missile submarines to locate themselves when the surface to fire missiles, this is not a problem. You're not going to predict where the sub is going to surface to be within 100m of it.
Or let's say you're using this jammer with one of the new 'smart' bombs that use GPS. The bomb is falling towards you being guided by your signal, and 100m away, the jammer causes it to lose 'lock' on the GPS signal. It knew where you were a few seconds before, and it's falling at terminal velocity. So what if it loses lock a fraction of a second before it hits you? It will still ruin your day.
So, to summarize, yes, you could crash planes with this, *if* the FAA ever decides to use GPS for landing purposes (which they haven't yet), *if* you can find a spot within 100m of where the plane is landing to jam the signal (sitting on the runway probably would not be a good idea), and *if* it mattered at all if the plane lost lock on the signal a few seconds before landing.
If you're trying to crash planes, it seems like it would be easier to use a bomb. However, *as usual*, those who don't understand the technology are using it to create false fears among others. I would have hoped that those on /. were too smart to fall for that.
Since they seem to be having a little /. effect problem I mirrored the text of the article. http://jennings.yi.org/gps.html
Yeah, well, as if it isn't bad enough with the FCC and personal CD players...
Must I be required to have an anal probe so the $6.00/hr security guard can be reasonably sure I'm not going to try to take the plane down?
Jamming itself is quite simple. You just pump
out a bunch of signals on the same frequencies
as the GPS wants to use. However, there is
another problem for the wannabe jammer, which
is that if you start jamming something, then
you are generating lots of radio waves which
can be detected. Your enemy simply triangulates
where the jamming is coming from, and within
a minute of turning on your jammer, you will
have artillery falling all over your position.
A bunch of 155mm shells will probably convince
you that jamming is not such a good idea.
...
Yes! It finally happened. Whenever I travel with a GPS device, I always think, "Even though this device tracks me, no one should be able to." I can now travel in peace. "Watch out! They might start launching cows at us" --Buck Martinez
It'd work a lot better if it used a beowulf cluster of Crusoe processors!
= ==============
CT
===========================================
=====================================
I took a bitchslapping for the energy-efficient Crusoe(tm) processor.
>that would take an awful lot of power
= ==============
Not if they used low-power Crusoe processors!
CT
===========================================
=====================================
I took a bitchslapping for the energy-efficient Crusoe(tm) processor.
As I have given away my AOL spam worthy account and privacy to slahdot..... I know that i am well rrunk. Why are people worried about jamming a low orbit satalire when there are 15-year olds that screw with the NSA of america. I dont know all people, but *&£( is cruseing towards the fan and we are the firewall in the way. >'o' )Quote( We are the but the same as Roman plumbers.. except we bring data in our 'lead' lined pipes.
I had a SIG once... it was years ago.
if you read the article it doesn't say they managed to jam GPS, just sattelite and uhf equipment, but with other components they could possibly jam gps. passivly jamming uhf is trivial. jamming gps would probably demand components that are not as readily available.
I just did a web search on Zarf... seems it's a popular mud name. Didn't know, I don't mud. So... I've created a separate slashdot account to avoid confusion. Sad, I had a low UID on that other account and was finally getting some karma.
//
--// Hartsock
Live to Code, Code to Live!
As a user of "P" code GPS (trimble) base stations, i think a jammer is the silliest thing i have ever heard of. I worked as a Base-op in burma, commie china, Egypt, and several other hot tourist spots!! for those that do not know, a base station takes the programmed error of GPS and averages it over a time period (longer it sets, more accurate it gets) then broadcasts that info on a VHS freq to the client GPS devices, this is useful for surveying. it brings the accuracy from +/- 40m to +/- .5m could be used for missile guidance systems, ??how far can line of sight VHF go??? i can throw a gov engineer further. So, here are my top 10 ways to jam a GPS base station 10) give the operator of the station access to a whore. 9) Drop some beer or whiskey nearby where he can find it. 8) Tell him you will give him $5 to turn it off 7) wait for him forget to refill the diesel tank 6) don't worry, it will break soon 5) supply him with an ECONOMY generator, preferably some cheap pc of crap purchased at Grainger 4) wait for his employer to screw him out of break days, he will intentionally crash the fucker then, just to cost em $$$$$ 3) move it 5m, (will take it 24hrs to figure out where it is) 2) let the freon out of the cooling system 1) just ask the operator, most could give a fuck
But what the hell do I know. I'm just disgusted with the Hole world anyway
I'd expect the usual blithering lusers to talk about banning this (probably "for The Children!") for awhile until reality intrudes.
It's also worth noting that the easiest way to feel more comfortable about this sort of thing would be to realize that a) GPS counts as a vital military service, b) jamming it could be seen as a threat to the country and that civilian usages also cause threats to a variety of important services, c) to jam, it must transmit and finally d) if it transmits, you can drop something nasty on it from a squad of pissed-off Marines on up.
__
In some of these parks, the rescue attempts are known as "I.N.S."--Interference with Natural Selection . . .
It's really off-topic here, but OK. Software that I had written was in question. I write it as a contribution to the free software community exclusively. I do not want to be somebody else's unpaid employee, which is what I effectively am when somebody takes my software and does not return anything to the community or to me - does not distribute their modifications, does not distribute source code at all. That is the quid-pro-quo implicit in free software. If people want to use it in a way that is outside of the GPL, they are welcome to get a commercial license from me, so that there is some return to the community for the software - I'll take the money and use it for some free software cause. So, the point here is that I do not consider free software to be a gift. It's part of an exchange. Generally, that exchange means that I get more, and better, free software in return for my efforts. OK, your question didn't get moderated off-topic, so maybe my reply won't be. Thanks Bruce
Bruce Perens.
Heh you can say that again. CA grade GPS (what civilians get) is accurate to about 100m, and gets even better if differential GPS is used. In terms of positioning a nuclear bomb, that's like arguing over a few microns.. utterly pointless. Let's not forget that nukes could be accurately aimed long before the advent of GPS, BTW.
--
I think there is a world market for maybe five personal web logs.
Differential GPS relies on being able to yank the signal over the selected area in an emergency. It should be noted, though, that the Russian GLONASS system doesn't have Selective Availability, and that a combined GPS-GLONASS receiver can be build to achieve very good accuracy. The European Galileo system is supposed to be launched this decade, too.
Jamming radio signals isn't high tech exactly -- dicatorships have been doing it for many decades to keep real news out. The only question is: how big an area do you want to jam? The bigger the area, the fancier the jamming.
You need wideband jamming to block GPS, since it uses spread spectrum, so the cost goes up (you need wideband amplifiers etc; you may be able to boost the efficiency by mimicing the real spreading sequence, which would add complexity.) However, the biggest cost is still going to be your wideband power amplifier stage. The bigger area you want to jam, the higher the cost.
Oh, the military has played with GPS jamming for years. There has been several Notices To Airmen (NOTAMs) from the FAA warning of GPS outages around <military base> at <time> over the past few years.
You don't need a lot of transmission power if you can get the jammer really close to your target. Jammer artillery shells bury themselves in the ground and their protroding antennas are made to look like the vegetation making them hard to find and disable. They are cheap and very effective.
----
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
- Frequency Modulation
- Spread spectrum and frequency hopping
- Encoding and Compression
- Error correction
- Contingency Link Margin
- Active Channel Seeking
And those are just the ones that come spontaneously to mind...Also, I would say that, if we're gonna pick on colorful adjectives, we should at least give credit to the engineers who designed the comm equiment on "the latest generation of global communications satellites" for their "heroic" efforts to create a robust system, before we start calling people "naive."
I can see the fnords!
While performing field tests out of Nellis AFB for an onboard ECCM system for fighter jets, the engineers noticed that intermittently, there was another jamming source, in addition to the one they were using to test their countermeasure. In fact, this source was so much better than the jammer they were using for the test that the countermeasure under test was completely ineffective.
So they got the USAF to send out planes to locate this mystery source, and it turned out to be in a small town outside Nellis. When investigators went to the town, they discovered the jamming signal eminated from an old auto garage. Inside was a weathered old man using a pre-WWI DC arc welder. It turned out to be the arc welder that was radiating like a banshee from DC to light.
When the Air Force and engineers learned this, they offered to buy the welder from the mechanic, but he refused every offer, citing his preference of the old DC welders, and his dislike of anything he would be able to find to replace it.
So. Moral is, if you want a cheap, low-tech jammer, pump a few dozen amps DC across an air gap.
I can see the fnords!
Bruce,
3 4211&cid=293
I asked you a question at:
http://slashdot.org/comments.pl?sid=00/04/18/13
You responded to my original comment, but completely misinterpreted what I said, and did not address my question in any way, shape, or form. I would appreciate a meaningfull response.
Thanks,
Fall
Ooooo, big coverup...
:-)
Everyone I know who knows about GPS has known about Selective Availability (SA for short) for years.
Funny thing is, they had to turn it off during Desert Storm (probably the only time it might have served a purpose) because they didn't have enough military receivers
That would be your government at work.
--
grappler
Vidi, Vici, Veni
AFAIK, your GPS receiver shouldn't get more accurate at speed. However, you may get a better fix for your present position if there is some way of telling your GPS receiver that you are stationary, since you are fixing some of the variables (velocity & acceleration) that your unit is trying to determine.
Your basic accuracy depends on where the satellites you are getting a fix off are located, with the ideal being 3 satellites at 5 degrees above the horizon, and a 4th directly overhead.
Vertical accuracy is less accurate than horizontal accuracy, due to the fact the entire constellation is normally 'above' you.
Donte Alistair Anderson Roberts - hi son!
Karma: Chameleon
I would say that the resolution that consumer grade GPS provides is more than enough to allow an ICBM with a nuclear bomb to be more than effective. The GPS drift that the consumer devices are subject to is much more likely there to help prevent accurate conventional weapon attacks.
For a great introduction to the GPS system (and technologies such as differential GPS) check out the Trimble web site:
What do you mean - "what they don't tell you about GPS?" If you mean that owners - the US Air Force, they tell lots., including all that.
This is widely known and common information - obviously. I mean, if you know about it, its not that unknown now, is it?
Space Times, Jane's, and other Federal geek rags have told you all about this many times over. And I'm sure that you can find the info at either www.laafb.af.mil (they guys that bought and built it) and/or www.schriever.af.mil (the guys who fly it).
Not only everything you said - but Clinton wrongly told everyone that the AF was going to give everyone 1m resolution with consumer gear. Unfortunately, he didn't give them an executive order - so they ignored him, as usual. Consumer gear without using multisampling (sitting in one spot for a while to get a more accurate position by taking more samples) give you around 30 m accuracy (that is, its off by about errrr at least 30 m in all directions (like you were in a 30 m hampster ball)
Surveyors use multisampling GPS do this all the time.
Many people use it just for timing anyway - not caring about the location, but use it to keep lots of clocks across a wide area in sync.
i'm rambling - but i was concerned that "they" have told us a LOT about GPS... none of this info should be shocking and none of it is secret or unknown in any fashion.
guns kill people like spoons make Rosie O'Donnell fat.
Oh shit! My nuke missed by 100 meters. Damn!
There are already UHF sources like TV stations that disrupt the civil GPS signals.
There are also a few spots where the interference from different sources just keep GPS from working. There's one somewhere on the east coast (PA/NY?) and a spot near St Louis (on the Ill side of the river) where GPS just doesn't work.
GPS does some interesting frequency hopping. If you can mess with that, 1W would be all it takes.
For what its worth the GPS signals are something like 20 dba below the background radiation noise level at the frequencies used so you could consider it always jammed anyway.
From what I understand, the error inserted is about 100 metres. Would that make a lot of difference if you were using a nuclear device?
Dana
Wrong. The GPS constellation is in low earth orbit, and they are on inclined orbits, so that they cover the whole earth's surface.
Furthermore, the GPS system uses spread spectrum modulation to make it much harder to jam: you would have to create a very wide bandwidth signal at 1.2GHz to block the signal.
Probably, what the military did was come up with a system that not only blocks the signal, but spoofs it, so that rather than just getting no answer you get a wrong answer (since most military gear has both GPS and intertial nav, if your GPS stops giving you any data you fall back, but if it gives you bogus data you screw up your INS).
The reason they are doing this is probably the same reason a good sysadmin tries to break into his own system: once you know what can be done and how, you can begin to act to prevent it.
www.eFax.com are spammers
The GPS system that civilian units use operates on about 1.2GHz (which is way above the UHF TV band and cellular band). The problem with a single frequency system is that you have no idea how much the atmosphere is bending the signal, so you have a systemic error right there. Add to this selective availability, and you get the 30-100 meter error most people quote.
Military units use 2 freqs: the civilian accessable 1.2GHz frequency, and 1.5GHz. Since atmospheric bending is frequency dependant, you get two different readings, and can then derive the real data from that. So, even when they turn off SA, civilian units will not be as accurate as military units.
www.eFax.com are spammers
What purpose does building one of these devices have apart from annoying the military or doing illegal activites ? seems rather pointless to me
Someday, we'll look back on this, laugh nervously and change the subject.
Like this is going to bother the military - "Hey, some loser is jamming our GPS! They've got to be putting out a pretty powerful signal to do that - where's that RF-seeking missile?"
Slightly used VHF/UHF signal jammer for sale (built 1975). Also cleans carpet and comes with handy stair attachment. Only $25
Dual purpose "just like new" VHF/UHF signal jammer for sale (built 1978). Comes with 1 cookbook and 4 components for mixing cake frosting, whipped cream, etc... Only $10.00
My mom ruined so many good Saturday morning "Looney Tunes" with those damn things.
--Clay
Perhaps soak the GPS in some grizzly pheromone for added effect :-)
All opinions are my own - until criticized
When the military first announced their "selective availability", I thought that it was a remarkably stupid idea. The Russians would simply steal the plans for the military receivers, and the plans for the factory that made them, and then the US would give them a loan and technical assistance to build it, and so on. Over the years since, I think that the idea has proven itself to be at least as stupid as I thought. The only reason Congress hasn't been beseiged by a campaign to end selective availability is that it just doesn't matter; to us or to the terrorists. If the military moved to end it on their own, they'd have to admit they were wrong.
Back to the topic at hand: I agree with you, barrage jamming would be tough to beat. But have you seen some of the recent adaptive filtering work? Pretty impressive stuff, and might make this a lot harder.
See what I've been reading.
It's not a secret--it's just not advertised alot.
If I remember right, without the p-code, the accuracy is only about 100-200 meters, but with it, you can get to down around 1-2 meters. That's almost too accurate. I remember that there are even some satellites that are only available with the p-code, which is part of selective avbailability, even in peacetime.
The military GPS also has averaging techniques, which takes the average of as many fixes you can take without moving the receiver.
One problem with barrage jamming is that it is very rough on the transmitter. You need some way to cool off the transmitter, or it will overheat. It depends on the distance between the transmitter and the receiver and the jammer, but usually you have to jam with more power than the transmitter.
I do what the voices on my console tell me to do.
Process gain is basically the improvement in signal-to-noise ratio that can be had in exchange for letting your signal take up more space than Mr. Shannon says it needs.
:-)
For example, Dixon's Spread Spectrum Systems says that for FM/FSK signals with over-unity deviation ratios, the process gain is 3 * (maximum deviation^2). The S/N ratio for the narrowband information being transmitted is effectively improved by allowing it to occupy more spectrum space than necessary. This is why I have my microwave link tweaked to chew up several dozen more MHz of prime 10-GHz real estate that it probably really needs.
As I understand it, another way to think of process gain in the general case is in terms of jamming immunity; i.e., how much power is it going to require in order to use an uncorrelated transmitter to jam the channel.
I'm sure there are different process-gain equations for various modulation mechanisms, but they are all going to boil down to the same basic idea: trading occupied BW for S/N.
Dahlmann tightly grips the knife, which he may have no idea how to use, and steps out into the plain.
Drop the commentary, and give us just the news! That way I wouldn't have to write the following piece of flamebait:
It apparently cost these people $7,500 to build one of these devices. In mass production, the cost would be much less, perhaps down to $99 or so. Just think, anybody could walk into Fry's and pick up a box which could screw up aircraft navigation!
---
How am I supposed to fit a pithy, relevant quote into 120 characters?
By using different modulation/transmission techniques, one may be able to reduce the effect of stochiastic noise on the demodulation side. Take a look at the new cell/portable phones. There is a lot less static on those than there was 5 years ago. Transmissions are always battling the signal to noise ratio. Satelites have to worry about radiation, solar winds, coronal discharges and whatnot screwing up the transmissions. It may not be heroic to you, but to us ham radio freaks it sure is! I remember being in 3rd grade and writing "when I grow up I want to be a jam-proof satelite defending my carrier frequency from the evil-doers! :)
Give them a break. Radios are only 50 years old. We've come a long way. Where would this world be if all these transmission that we rely upon went down 10 times a day?
Speeding never killed anyone. Stopping did.
The first post in the United States was established by Benjamin Franklin in 1775.
It's only 1 centimeter with post processing (the errors are made available the next day for correcting readings). The best that can be achieved immediately is 1-3 meter error, due to atmospheric affects.
...phil
...phil
"For a list of the ways which technology has failed to improve our quality of life, press 3."
ahh, the possibilities.
Bad guy launches missle relying on GPS.
Change just a little to steer it. "Here, missle missle"
A bit more. "C'mon, you're still drifting away."
Finaly change: "THere you go. You're on target now. GO say 'Hi' to
mommy . .
And little Mikey the Missle, thinking that he has cleverly found D.C.,
returns to his launcher in Bahgdad.
:)
hawk
Selective availability can be defeated using differential GPS. I got a Trimble dual differential receiver for a good price at a West Marine clearance sale, and my GPS reads out to a few meters uncertainty rather than 100 meters. Broadband jamming requires a whole lot of power and is thus less effective. Signal strength at any one frequency = power / bandwidth. GPS jamming is easier because there are a number of discrete frequencies. Military GPS uses spread spectrum with an undisclosed spreading sequence, so you must cover all frequencies in a wide band. It also uses tricks like processing gain to recover a usable signal in the presence of a lot of noise.
Hm. Anyone have a simple explanation of processing gain? I'm not enough of an RF person.
Thanks
Bruce
Bruce Perens.
I want something I can use in my car on the highway, possibly even directional so I can take out specific callers. It be great, but consider the driver weaving and cursing as he or she tries to figure out why the signal has gone dead. The problem with cell phones in cars isn't the fact that they exist, its that most people don't have hands free sets for them. As it is if you have people in the car you can and do talk to them, and for the most part when you need to concentrate on driving you fall silent. --locust
I'd like a cellphone jammer so I could get the clueless drivers to pay more attention to the road than the phone and notepad. I know the Japanese have a device that has about a 150 meter range that they use in theaters but I want something I can use in my car on the highway, possibly even directional so I can take out specific callers. There's got to be a couple of hardware hackers out there that could throw a design out open source for some field trials 8^)
1: You can get differential GPS broadcasts now almost everywhere on the globe. You get a GPS receiver that picks up two signals: one from the satellites, and one from a ground base that knows its own location and broadcasts the difference between that and where the satellites tell it it is.
2: Not only did they not increase the offset during Desert Storm- they turned it off completely! The military GPS units are expensive and were in short supply, so many soldiers were using civilian units from home to find their way in the desert.
It's only a matter of time now before the offset is removed for good so the signals can be used for more accurate civilian tasks like surveying without all the expense to of the differential units or the expense to the military of their offset decoders.
The really scary thing about this jamming is that commercial airliners are starting to use GPS signals for navigation and bad weather landing.
It's a secret plot by women to get men to put down these things and actually get men to get out of the car and ask directions... or at least look at the road signs..
---
-
ping -f 255.255.255.255 # if only
(rockets can't be steered, missiles can)
Excuse me? A rocket is simply a motor that generates thrust by hurling mass out the back. You can, too, steer a rocket: just point the exhaust nozzle in a different direction. A missile, on the other hand, is an object that is flying (has been hurled) through space (air, usually, but not necessarily) -- for instance, a spitwad is a missile (ballistic), as is a dart (ballistic), as is a Sidewinder (rocket powered). Some of these things are steerable and some of them aren't, but the words "rocket" and "missile" are not the appropriate ones to use to identify that distinction.
Oh, go on, check out my job.
GPS is so prevalent in the 'new', 'modern' battlefield that a device like this makes a lot of sense and I am sure that a lot of militaries have already built their own --or if not, they are starting up similar projects as we type...
Just some potential uses of a GPS jammer: Handheld and dashboard-mounted GPS is used all the time in tanks/helicopters/ships and by troops in the field. In most cases (i.e. outside of the US) these are *commercial* grade GPS, not US Military-grade GPS --i.e. they will be much less resistant to jamming.
The US Military, OTOH, has put so much faith into GPS, it's now using it to guide smart bombs and cruise missiles... so, you can see, the fact that the US Air Force itself has proven that it is feasible to jam GPS with COTS (commercial off-the-shelf) technology will be a HUGE deal to the defense planners of the world...
Now, I am not a EE, much less a DSP/GPS specialist, but from my knowledge of the system I am guessing that: a) the system described above won't be much use against fast-moving airborne GPS (fighters), and b) US Military-grade GPS can be affected just as effectively --as I believe that the US Navy is using an encoded higher time-resolution signal to achieve more accurate measurements. But if the signal is jammed, encryption won't be much use, right?
engineers never lie; we just approximate the truth.
as far as I understand, the error is mainly introduced into the altitude precision. this way civilians can get around, everyone knows where everything is, but no one can be certain they are going to be able to hit it if they launch a missile at it.
Daniel
I'm quite surprised it took this long. I heard a rumor about 2 years ago that a GPS jamming device was available in Russia with a 30 mile radius.
The NavSat network is a series of satellites w/ atomic clocks located in Geosynchronous orbit (so they hold steady above the equator) at over 20,000 miles distance. The timing pulses they send are low power, necessarilly so for them to last as long on their available power output.
Anyone with knowledge of which frequencies are used and the abillity to transmit their own quasi timing pulses in a manner which would interfere with at least 12 possible sats over the horizon at once could make their own jammer for much less.
It's easy to see that not many people are doing this, or GPS would be effectively knocked out in metro areas.
Wow, this must be a record for old news on /. Anyone watching tv in the 80's knows that frequency jamming was perfected with the advent of knight rider's car, KITT. And it didn't take a team of U.S. engineers, either; it was single-handedly perfected by Bonnie in that roving semi.
The only anti-jam feature on most current GPS systems is the spread spectrum modulation. This is a complex topic in communications engineering and I realy don't have room to explain it in detail. However, the nub is that the signal is mixed with a high speed pseudo-random bit stream. This greatly increases its bandwidth (which BTW in this case does not provide any inherent signal to noise advantage) and causes the energy/Hz to drop below the thermal noise level. The receiver generates an identicle bit stream synchronised with the one on the satellite, but offset by the delay between satellite and receiver (this synchronisations is what's going on whilst your receiver is acquiring). When the second bit stream is combined with the signal from the satellite the energy is "de-spread" and basically gets piled back up into a narrow spike again. The inportant point is that any other signal will not correlate with the bit stream in the receiver. A wide band jammer stays wide-band and a narrow band jammer gets spread. In either case the recovered spike now sticks up above the jammer power. Generating a signal spread in the same way as that from the satellite doesn't help unless you can arrange for it to arrive at the receiver in exact synchronism, and to do this you need to know the exact distance between your jammer and the receiver. BTW, this pallaver is not just done for jam resistance, the synchronised bit stream is a critical part of the navigation solution. If anyone knows of an explanation of the above with diagrams, I suspect that many readers who are not RF engineers would find it useful.
Unfortunately, the above scheme only gives you a spreading gain of about 100. I.E. if your jammer is 100 times louder than the satellite then you still win. Since the satellites are a long was away, this is very easy to achieve.
One solution being actively persued by me and my colleagues in DERA's airborne antennas group and presumably the military research labs of other nations is the use of adaptive antennas. I won't even begin to try and explain how these work, but the bottom line is that by using several antennas combined via some clever electronics one can form nulls in the combined antenna pattern which point at the jammers. This makes the job of the jammer significantly more difficult, but not impossible.
BTW, there is nothing secret in the above. One of our industrial partners exhibited a prototype adaptive GPS antenna at the Farnborough Air Show at least 4 and possibly 6 years ago. Also, as might be expected, most current work in adaptive antennas is aimed at using them to defeat multi-path problems in mobile communications.
Everytime I take off a few days from my demanding job in the Valley, I like to head off to places like Yosimite and Yellowstone. But each month it seems that there are more and more untrained yuppies, grinding up the roads with their SUVs, displaying their designer hiking outfits (Tommy Hilfiger backpacks, anyone), and *always* carrying a GPS.
Granted, most of them have no idea how to actually *use* a GPS, or how to coordinate it with a map, but a few manage to figure it out if they haven't succumbed to heat stroke after the first mile or so (apparently they believe that there are Starbucks's scattered every 100 feet, just like in Manhattan). Having conquered the navigation system, they feel supremely condfident, and stride forward in their fashionable Donna Karan outdoorwear. But just sit back, and in a few hours, after wandering a few yards off the path, those newbies will be crying for help, and they expect the rangers to spend their time to go off and rescue them! How absurd! It is the *user's* job to be prepared, not the staff. Why won't they learn? The last thing we need is to devote our time, as a community, to digging these helpless newbies out of a trench they've buried themselves in. If you want to enter *our* territory, you better do it on *our* rules, pal.
I have this friend that has a navagation system in his truck. It's a nice system, between the GPS and a CD map of the east coast he is able to get just about anywhere.
But he uses it to get everywhere. He punches in the address for the grocery store (a mile away) and then punches in the address for back home. Maybe the novelty of a $3000 toy wears off slowly, maybe he is really that bad with directions.
For some reason the thought of wacked-out luddite guerrillas jamming his satellite signal on his way home from the corner market really cracks me up. I can just see him driving aimlessly for hours waiting for the navigation system to tell him when to turn.
Man-oh-man, a GPS jammer is a toy that may not lose it's novelty for a while....
[it is] believed that the latest generation of global communications satellites would be immune to similar home-built equipment, as they are "heroically resistant to jamming"
What does Heroically Resistant mean? I can see this satellite in orbit straining: must resist jamming! grr!It must be wonderful to be so naive that you trust technology to be heroic.
-
[signature]
GPS contains the following capabilities:
Selective Availability adds some noise to the signal received by civilian receivers; military receivers can tune this one out using a specific cryptographic key. Selective Availability was actually turned off during Desert Storm, because the U.S. military didn't have enough "military" receivers for their troops!
Anti-Spoofing makes it cryptographically impossible to give a bogus signal to a military receiver.
The P code (P for Precision) gives very high precision to certain military receivers which have been equipped with receivers for the P code signal, in addition to the regular (CA, for Coarse Aquisition) code. The P code is not receivable by civilian receivers.
The GPS signal is jam resistant by being spread spectrum, but as the poster points out, there isn't any defense against wideband ("barrage") jamming.
The GPS signal coming from the sattelite has a deliberate offset so that they are never 100% accurate. This is because any moron with a steerable missile (rockets can't be steered, missiles can) that can carry a nuclear bomb can wire up a GPS as a precision-guidance system to deliver this missile very accurately.
In time of war, the offset increases dramatically, though supposedly that didn't happen during Desert Storm. I think it has something to do with the GPS capabilities of the enemy.
The military GPS was designed with anti-spoofing (just like IP spoofing) and anti-jamming (I think it dynamically changes frequencies, but not sure) capabilities, but these are not built into the civilian models.
The military GPS can be given a cryptological key that significantly increases the accuracy and enables all the other Electronics Counter-Countermeasures (ECCM--Electonic Countermeasures, or ECM, is what normal people call jamming, ECCM is what you do to combat ECM).
Of course, once you start barrage jamming (blocking out the entire radio spectrum), all bets are off. Nothing can make it through barrage jamming.
I do what the voices on my console tell me to do.