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#11
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jc wrote in message ... Chad Irby wrote: snip Unless you spend a lot more money on them, they're also very vulnerable to the newer EMP weapons. In WWII the real secret weapon (proximity fuses) could only be used over water until mid 44,in the UK with the V1 and not over enemy territory intil the start of 45. The reason was fear of of copying a dud shell as the allies had more to lose. Actually, proximity fuses did not have the "self-destruct" mechanism, therefore they would explode when hit the ground. Hence the limitation. What is the better target for EMP weapons a GPS jammer or the NY stock exchange? The "piles of cheap low-power jammers" idea is nice, as long as you don't have to keep using them. At a rough guess the cost for a 1W jammer using cellphone components would be ~$5, just keep sending them up with balloons (add $1). Well, it is a bit under-estimated. I don't know much about how GPS works (electronically), but I know it has commercial and military channels/ frequencies and commercial and military encoding. For civilian use, optimum accuracy is receiving three GPS signals from three satellites (somebody correct me if I am wrong, but I read it somewhere for more expensive GPS devices for use, let's say in aviation) for elevation and position. As you travel, the sattelites "switch" (just like GSM) control. Is it a same frequency/coding? I don't know, but it is sure as hell that if you manage to jam one channel, there are other two sats. Jam the other two signals, there is one. In the meantime, your GPS receiver "struggles" to get signals from the other two. And we are talking about civilian device. What method are you going to use-noise or deceptive jamming? Read the history of updates of "AN-ALQ" devices-or just one! Noise? In that case, you are a flashbulb, and you will be attacked with alternate weapon on jamming station. The band is narrow AFAIK, so if your opponent knows what to "listen", you're toast. Deceptive jamming. Well, it is not analogue signal anymore but digital and probably encoded signal-actually, it IS encoded even for the civ use in the matter of digital design-and probably scrambled in mil use. Thus, you have to "doctor" the signal. Actually, signals -three satellites, remeber? You can go to make this simmilar to tripled digital FBW system on, let's say, F-16. Well, if you have failure on one channel then other two will feed the aircraft with flying info, or in this instance, the weapon itself. Two of them gone, you have one channel and two duds and you think that the flying computer thinks that all three are duds? Wrong. Even your modem has sufficient let-me-check-if-this-is-wright capabilities (CRC, CS) so it is possible to imagine that FBW computer might have something simmilar. And your jamming signal has to feed the encoded and encripted digital channel switchig-multiple sattelite signals with false data, and it is desirable to feed them with something meaningful to drive the weapon away, not to owerflow it with garbage. And it's been a long time since F-16 digital FBW was designed (I actually don't know is it possible to fly it on one channel, but I would require it that it would! ))). Oh, the output power. In the Battle of Britain, there was a German bombing device called X-Gerat. Basically, you had three signals for guidance, based on the Lorentz blind-landing system (Morse dots-too left of course, dashes-too right of course, single tone-on course), and the offset signal to mark the bomb dropping. Once discovered, it was jammed by the Brits by sending "dashes". Well, it sometimes worked (and it seems it worked well!) but there were cases that the crew was able to depict the jamming-slight but ear-noticeable change of modulation or change of volume and to offset it. Or back to Your cell phone-it can "sense" the distance from the GSM station-actually, my Motorola CD920/930 has a hidden option that, when activated can measure and display the DISTANCE from the GSM broadcast (albait in very weird units )). Sattelites have very low output power and if you send a "heroic" signal which is by magnitude stronger then satellite signal, the system might think "this is too powerful", or "this is too close" and simpy switch to something else. Remember, expirienced LW pilots were able to depict the false signals. And code-breaking is not a trivial thing; put a password to a MS-Word-file that is, let's say 5 characters long and try to crack it with some program designed to do it, let's say Advanced Office Password Recovery. Yeah, it will eventually break it, but count how long it will take! Also, You have A GPS and GLONASS (a Soviet GPS); while GLONASS is reportedly in a bad shape, as far as I can remember India (I am really not sure!) uses BOTH systems which might suggest that it is not in such bad shape after all. While I am not aware of Russian GPS bombing/missile systems in use, some of their (export?) weapon systems use both. I agree that we are talking about the weapon (figter, bomber, cruise missile or JDAM) that might not have all the "offset" capabilities that I have mentioned here; I might not even be correct in numerous things. Actually, you will need a (really, really) good sample either of the good portion of the knowledge how -military- part of the system works or the system itself. And once you develop a system, it will certainly not be of the cell-phone size but rather of an underwing or wingtip pod size, weight and cost. Nele NULLA ROSA SINE SPINA |
#12
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In message , Al Dykes
writes In article , Paul J. Adam wrote: Let's split the difference and say it got lost somewhere along the way. (Otherwise, why would CCM against GPS jammers be a profitable business, if the system was inherently resistant?) Some creative Russian printed up some ACME GPS Jamming System brochures and took SH for some of his money ? Elements of that. Basic GPS systems, civilian and some military, are very easily sent berserk by low jamming powers. Less basic systems are more resistant, increasing (for rising input cost) to very jam-proof systems that are extremely difficult to lock out. GPS jamming is a real problem. It has real solutions and it's not a surprise. (And it's harder to do than the doomsayers would claim, just as it's more of a problem than some like to admit) -- He thinks too much: such men are dangerous. Julius Caesar I:2 Paul J. Adam MainBoxatjrwlynch[dot]demon{dot}co(.)uk |
#13
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"Paul J. Adam" wrote in message ...
In message , Al Dykes writes In article , Paul J. Adam wrote: Let's split the difference and say it got lost somewhere along the way. (Otherwise, why would CCM against GPS jammers be a profitable business, if the system was inherently resistant?) Some creative Russian printed up some ACME GPS Jamming System brochures and took SH for some of his money ? Elements of that. Basic GPS systems, civilian and some military, are very easily sent berserk by low jamming powers. Less basic systems are more resistant, increasing (for rising input cost) to very jam-proof systems that are extremely difficult to lock out. GPS jamming is a real problem. It has real solutions and it's not a surprise. (And it's harder to do than the doomsayers would claim, just as it's more of a problem than some like to admit) The higher end systems would appear to have highly directional 'phased array' antena that can exclude the jaming signal by locking onto the satelite directly based on both satelite signal and known maps of satelite position. A jammer must thus be as high as possible (preferably in line with between the satelite ) to get energy into the sidelobes of the antena. Low cost solid state acceleromters and inertial guidence systems will give many munitions a inertial guidence system that will takeover as soon as effective jamming is detected which is likely to be only near the target. There are indeed wind corrected bombs that cost perhaps double that of a GPS bomb but loose only a little in accuracy. On top of that simple infrared imaging systems based on the same sensors now used in highend cars add even more accuracy than GPS is capable of. At best jammer will only be able to degrade the accuracy slightly while forcing up the price of the munition slighly or even increasing it by forcing the bomber to add a simple terminal homing system. |
#14
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GPS jammers (noise generators) are the standard tools nowadays.
Obviously, the weak satellite signal could be shutdown quite easily. It's not a top notch, cool technology anymore, just usual (and probably boring) stuff. See, http://www.noisecom.com/content/Prod.../GPS7500_5.pdf Russian regards, Yuri |
#16
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On Mon, 19 Jul 2004 15:20:40 +0200, Nele VII wrote:
At a rough guess the cost for a 1W jammer using cellphone components would be ~$5, just keep sending them up with balloons (add $1). Well, it is a bit under-estimated. I don't know much about how GPS works (electronically), but I know it has commercial and military channels/ frequencies and commercial and military encoding. For civilian use, optimum accuracy is receiving three GPS signals from three satellites (somebody correct me if I am wrong, but I read it somewhere for more expensive GPS devices for use, let's say in aviation) for elevation and position. You need to receive signals from four satellites to obtain a 3-D position. Most GPS receivers can make do with three satellites, but when they do they give only a 2-D position, and assume your elevation is constant. Modern consumer GPS receivers can receive and use signals from up to twelve GPS satellites simultaneously. With the current GPS constellation, it's not unusual to have ten satellites above the horizon and useable. Most receivers will use the additional satellite signals (above the four needed for 3-D position) to determine your position more accurately. As you travel, the sattelites "switch" (just like GSM) control. Actually, the satellites are most likely traveling faster than you are. Their orbital period is just under 12 hours, so you'd have to be moving more than 2000 mph to stay directly underneath one. The GPS receiver computes which satellites are above the horizon, and listens for their signals. As satellites rise and set, the receiver updates the group of satellites it's listening for. [...] What method are you going to use-noise or deceptive jamming? Read the history of updates of "AN-ALQ" devices-or just one! Noise? In that case, you are a flashbulb, and you will be attacked with alternate weapon on jamming station. The band is narrow AFAIK, so if your opponent knows what to "listen", you're toast. [...] Deception jamming might be possible if you have a civilian receiver, but you'd need to crack the encrypted signal to spoof a military receiver. There are a number of introductory descriptions of how the GPS system works on the web -- for example, check out http://www.aero.org/publications/GPSPRIMER/ ljd |
#17
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Laurence Doering wrote:
On Mon, 19 Jul 2004 15:20:40 +0200, Nele VII wrote: snip What method are you going to use-noise or deceptive jamming? Read the history of updates of "AN-ALQ" devices-or just one! Noise? In that case, you are a flashbulb, and you will be attacked with alternate weapon on jamming station. The band is narrow AFAIK, so if your opponent knows what to "listen", you're toast. [...] Deception jamming might be possible if you have a civilian receiver, but you'd need to crack the encrypted signal to spoof a military receiver. Probably the best (cheap) method would be noise with digital transmissions (as per psuedo random code no need to crack the encryption) on the correct frequencies. 1W dosn't sound much but with the low recieved power of the GPS signal it dosn't take much to overwhelm or confuse it. The cellphone industry has ensured VERY low cost components eg power output transistors/amplifiers for a few cents. No need for elaborate environmental enclosures just attach balloon and battery stick a ziplok bag over the electronics and release. To avoid ECCM attacks change location immeadiately to another school, hospital etc although a vehicle outside the Chinese embassy for a release point is a possible. The cost of hitting the balloons once they are released makes them a rather assymetric weapon. -- regards jc LEGAL - I don't believe what I wrote and neither should you. Sobriety and/or sanity of the author is not guaranteed EMAIL - and are not valid email addresses. news2x at perentie is valid for a while. |
#18
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In article ,
jc wrote: Probably the best (cheap) method would be noise with digital transmissions (as per psuedo random code no need to crack the encryption) on the correct frequencies. 1W dosn't sound much but with the low recieved power of the GPS signal it dosn't take much to overwhelm or confuse it. The cellphone industry has ensured VERY low cost components eg power output transistors/amplifiers for a few cents. No need for elaborate environmental enclosures just attach balloon and battery stick a ziplok bag over the electronics and release. To avoid ECCM attacks change location immeadiately to another school, hospital etc although a vehicle outside the Chinese embassy for a release point is a possible. The cost of hitting the balloons once they are released makes them a rather assymetric weapon. You're forgetting something. Power. For a 1 watt output, you're going to need a battery or other power supply that can supply at least twice that for a significant period of time. If you're going for a balloon launch, to get to significant altitude, you're going to need a couple of hours of capacity, at *least*. Increased weight equal increased balloon size, by the way. With increased tankage for your lifting gas, and massively increased transportation costs. Not to mention, of course, that you're transmitting that 1 watt omnidirectionally, which means that you're only going to cover a couple of square miles with one jammer, at *best*. If you're going for a pure white noise "drown them out" system, plan on a *hundred* watts or more (to beat the directional antennas used on most modern weapons systems). If you're going for digital spoofing, use lower power levels, but spend a lot of money on electronically-steerable transmitters and high-end hardware to make the signal work past the dozen or so GPS sats in view at any one time. Suddenly, the "$5 balloon-borne jammer" is a "$500 balloon-borne jammer that only lasts a few hours." -- cirby at cfl.rr.com Remember: Objects in rearview mirror may be hallucinations. Slam on brakes accordingly. |
#19
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Don't know is it true or not, but have read that hobbyist level
nonsophisticated 1W jammer shuts down GPS devices in an area of hundred kilometres. The ECM warfare is very well developed field, so it's not a problem to jam a weak signal at all. Of course, the GPS could be done more or less jam proof, but it costs a lot of money and hence not practical for wide use. There's no difference in jamming radar/comm/GPS, all of them are the "RF devices", use the same basic principles and communication media. Russian regards, Yuri |
#20
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