Satellite Navigation

leolover · 02-07-2006, 08:01 AM

ok, as i know there are several possibilities to jam GPS:

first: a traditional jammer emitting noise in the frequencies used by GPS
Disandvantage: powerfull emitters are easy to detect and can be destroyed. also the receivers of gps-guided weapons are screened against signals coming from the ground.

second: a gps-faker. sound interesting, a sytem the emits a modified GSP-signal. if the receiver uses this fake signal to calculate the position, it will be misguided. this system uses only low-power emissions, hard to detect.

will the described system of a GPS-faker work???
if yes, could it also work if somebody launches a satellite with such an emitter to disable GPS worldwide?
or will the faked signals be ignored since they use an different PRN-code?

are there other possibilities to jam gps?

an last but not least what are counter-countermeasures to keep GPS working?

Wraith601 · 02-07-2006, 04:39 PM

Quote:

Originally Posted by leolover

ok, as i know there are several possibilities to jam GPS:

first: a traditional jammer emitting noise in the frequencies used by GPS
Disandvantage: powerfull emitters are easy to detect and can be destroyed. also the receivers of gps-guided weapons are screened against signals coming from the ground.

second: a gps-faker. sound interesting, a sytem the emits a modified GSP-signal. if the receiver uses this fake signal to calculate the position, it will be misguided. this system uses only low-power emissions, hard to detect.

will the described system of a GPS-faker work???
if yes, could it also work if somebody launches a satellite with such an emitter to disable GPS worldwide?
or will the faked signals be ignored since they use an different PRN-code?

are there other possibilities to jam gps?

an last but not least what are counter-countermeasures to keep GPS working?

Do you really expect military professionals to tell you how to defeat GPS on an open forum?

lurker · 02-07-2006, 05:35 PM

There are mass produced gps jammers made in Russia. Relatively small devices, battery powered. Can be mounted on a jeep.
Jamming radius is about 50km.

p.s. There were stories the Hussein supposedly had them in the beggining. But CNN showed huge Scud-size vehicles in their "cartoons" (everybody who knew had a good laugh).

**Shek** · 02-07-2006, 05:38 PM

Quote:

Originally Posted by lurker

There are mass produced gps jammers made in Russia. Relatively small devices, battery powered. Can be mounted on a jeep.
Jamming radius is about 50km.

p.s. There were stories the Hussein supposedly had them in the beggining. But CNN showed huge Scud-size vehicles in their "cartoons" (everybody who knew had a good laugh).

That'd be a bad move. Since LTs are always lost, all you'd end up doing is jamming them back on course. You can't win

canoe · 02-07-2006, 05:54 PM

From what I understand theres a number of GPS jammers out there and alot of them have success with the civilian frequencies. As far as I know there has been no effective jammer used for the military frequencies.

I know the Iraqies apparently bought some jammers from the Russians during the last war but they apparently had no significant effect on the U.S military gear. From what I understand the military frequencies are pretty hard to jam reliably. There also hard to spoof because their encrypted and the U.S isen't likely to release the encryption method or keys for them. That said its not unbeleivable that someone might develop a reliable working jammer for the mil frequencies at some point.

The other issue from a military perspective is if you activate a jammer like that your painting a bullseye on yourself. I think it took the U.S less then a day to detect and locate and eliminate the jammers the Iraqi's were using.

lurker · 02-07-2006, 06:09 PM

Quote:

Originally Posted by shek

That'd be a bad move. Since LTs are always lost, all you'd end up doing is jamming them back on course. You can't win

There are many ways. Not to block them completely, but re-translate with some delay for example.

It's easy to lose the sat singnal in P-code mode even without jamming. What do you think your receiver will acquire - faint signal from a sat, or a similar but more powerful signal from a jammer?

lurker · 02-07-2006, 06:16 PM

Quote:

Originally Posted by canoe

I know the Iraqies apparently bought some jammers from the Russians during the last war but they apparently had no significant effect on the U.S military gear.

There was a result. Tomahawks were prohibited to fly over Saudi Arabia for example. And that was effect of only 6 (afair) jammers.

Quote:

The other issue from a military perspective is if you activate a jammer like that your painting a bullseye on yourself. I think it took the U.S less then a day to detect and locate and eliminate the jammers the Iraqi's were using.

Only if you assume that jammers are manned. If it's fully authomatic (as they are), cheap (around 500$) and exist in mass (let say 1000's).
Put them on trees in every sq. kilometer and your missiles (each costs many 1000$) will go in circles.

canoe · 02-07-2006, 06:28 PM

Quote:

Originally Posted by lurker

There was a result. Tomahawks were prohibited to fly over Saudi Arabia for example. And that was effect of only 6 (afair) jammers.

Ok I think this is nonsense, the Saudi's may not have let the Tomahawks overfly but it would have had nothing to do with GPS jamming. The Tomahawks arn't completely reliant on GPS for guidance. They also have backup DSMAC and TERCOM radar guidance which they were using years before GPS guidance came to be accepted.

From what I understand some countries didn't want the Tomahawks overflying their populated areas incase it suffered a failure and crashed.

Quote:

Originally Posted by lurker

Only if you assume that jammers are manned. If it's fully authomatic (as they are), cheap (around 500$) and exist in mass (let say 1000's).
Put them on trees in every sq. kilometer and your missiles (each costs many 1000$) will go in circles.

That has yet to be seen but the jammers themselves are easy to detect and locate. And either way it would only really affect the GPS guided bombs, most of the U.S missiles either don't use GPS or have backup guidance systems. And can you provide a link to a jammer that jams military frequencies for $500? That sounds rediculusly low to me. I know you can get jammers for civie frequences for around that.

And as new jammers come out so does new protection against jamming.
http://www.defense-update.com/products/g/gps-aj.htm

lurker · 02-07-2006, 06:41 PM

Quote:

Originally Posted by canoe

Ok I think this is nonsense, the Saudi's may not have let the Tomahawks overfly but it would have had nothing to do with GPS jamming. The Tomahawks arn't completely reliant on GPS for guidance. They also have backup DSMAC and TERCOM radar guidance which they were using years before GPS guidance came to be accepted.

From what I understand some countries didn't want the Tomahawks overflying their populated areas incase it suffered a failure and crashed.

Maybe it's a non sense, but GPS jammers made the news around same time, so (I guess) there was some effect.
Initial number of misses (I don't remember if it is only for Tomahawks or total) was also very high, around a 100.

canoe · 02-07-2006, 06:42 PM

Quote:

Originally Posted by lurker

Maybe it's a non sense, but GPS jammers made the news around same time, so (I guess) there was some effect.
Initial number of misses (I don't remember if it is only for Tomahawks or total) was also very high, around a 100.

Again I doubt this had alot to do with jamming, the legacy guidance systems of the Tomahawks are good enough to hit building sized targets. Not as good at the GPS system mind you.

And are you talking number of failures or number of target misses? I know there were a number of Tomahawk failures (engines going out, hardware failures, etc) but I didn't hear of to many Tomahawks making it to their target area and missing their target.

Garry · 02-07-2006, 06:45 PM

Quote:

Originally Posted by canoe

Ok I think this is nonsense, the Saudi's may not have let the Tomahawks overfly but it would have had nothing to do with GPS jamming. The Tomahawks arn't completely reliant on GPS for guidance. They also have backup DSMAC and TERCOM radar guidance which they were using years before GPS guidance came to be accepted.

From what I understand some countries didn't want the Tomahawks overflying their populated areas incase it suffered a failure and crashed.

I remember during Yugoslavia bombing Tomohawks were flying to Bulgaria... and other countries..... and one went to Chinese embassy.... If they were not jammed then they were very unprecise!

lurker · 02-07-2006, 06:49 PM

Btw, I was not saying about jammers for "all" mil. frequencies for 500$, I was saying about "GPS jammer" for 500$.

Found a picture of it btw.

canoe · 02-07-2006, 06:50 PM

Quote:

Originally Posted by Garry

I remember during Yugoslavia bombing Tomohawks were flying to Bulgaria... and other countries..... and one went to Chinese embassy.... If they were not jammed then they were very unprecise!

Yah I remember the Chinese embassy incident as well. But from what I recall the Tomahawk hit the right building, its was the intel people who identified the wrong building.

*update*
I checked the stats the Tomahawks had about a 90% success rate pre-GPS(block I, block II). Thats including failures, misses, etc.

canoe · 02-07-2006, 06:52 PM

Quote:

Originally Posted by lurker

Btw, I was not saying about jammers for "all" mil. frequencies for 500$, I was saying about "GPS jammer" for 500$.

Found a picture of it btw.

And yes in that case your correct civie jammers can be bought for around that price. You can infact make a civie GPS jammer in your garage (can google the instructions on the net) if you know what to buy. The civilian frequences are pretty easy to jam.

lurker · 02-07-2006, 07:09 PM

Quote:

Originally Posted by canoe

And yes in that case your correct civie jammers can be bought for around that price. You can infact make a civie GPS jammer in your garage (can google the instructions on the net) if you know what to buy. The civilian frequences are pretty easy to jam.

They are not much different.

Current GPS freqs are:
L1 - 1575.42 Mhz - C/A and P/Y code
L2 - 1227.60 Mhz - P/Y code.

L2 is mil., but there are some civ. receivers that use both. The signals are relatively weak, since sats are geo-static and about 50 W only.

p.s. your link says exactly about the idea I posted in 1st posts - retransmit with some delay, i.e. create pseudosat.

02-07-2006, 08:01 AM	#1 (permalink)
leolover Regular Join Date: 10-20-05 Posts: 26	How to jam GPS? ok, as i know there are several possibilities to jam GPS: first: a traditional jammer emitting noise in the frequencies used by GPS Disandvantage: powerfull emitters are easy to detect and can be destroyed. also the receivers of gps-guided weapons are screened against signals coming from the ground. second: a gps-faker. sound interesting, a sytem the emits a modified GSP-signal. if the receiver uses this fake signal to calculate the position, it will be misguided. this system uses only low-power emissions, hard to detect. will the described system of a GPS-faker work??? if yes, could it also work if somebody launches a satellite with such an emitter to disable GPS worldwide? or will the faked signals be ignored since they use an different PRN-code? are there other possibilities to jam gps? an last but not least what are counter-countermeasures to keep GPS working?

02-07-2006, 05:35 PM	#3 (permalink)
lurker Contributor Join Date: 08-12-03 Posts: 696	There are mass produced gps jammers made in Russia. Relatively small devices, battery powered. Can be mounted on a jeep. Jamming radius is about 50km. p.s. There were stories the Hussein supposedly had them in the beggining. But CNN showed huge Scud-size vehicles in their "cartoons" (everybody who knew had a good laugh). __________________ Long time we thought that a million monkeys in front of a million typewriters would eventually type William Shakespeare's complete works. After invention of the Internet, we understand that it's not true. Last edited by lurker : 02-07-2006 at 05:37 PM.

02-07-2006, 05:54 PM	#5 (permalink)
canoe *Military Professional* Join Date: 08-13-05 Posts: 698 Country:	From what I understand theres a number of GPS jammers out there and alot of them have success with the civilian frequencies. As far as I know there has been no effective jammer used for the military frequencies. I know the Iraqies apparently bought some jammers from the Russians during the last war but they apparently had no significant effect on the U.S military gear. From what I understand the military frequencies are pretty hard to jam reliably. There also hard to spoof because their encrypted and the U.S isen't likely to release the encryption method or keys for them. That said its not unbeleivable that someone might develop a reliable working jammer for the mil frequencies at some point. The other issue from a military perspective is if you activate a jammer like that your painting a bullseye on yourself. I think it took the U.S less then a day to detect and locate and eliminate the jammers the Iraqi's were using. Last edited by canoe : 02-07-2006 at 05:58 PM.

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Satellite Navigation

Monday, October 22, 2007

How to gam GPS

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