Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Various not so random notes: The power needed to jam GPS depends a lot on receiver state, during TTFF it takes virtually nothing. Therefore most real jammers will periodically blast at high power, to dislodge any locked receivers and then continue at low power to keep them off the signal. They are also built spectrum efficient, by emitting a signal designed specifically to interfere with GPS' spread-spectrum encoding, either by trying to lure the receivers to aim for the jammer (lowest power) or just by mimicking the worst kind of power for acquisition tracking (higher power). Most receivers have hard-limiting inputs, so overload is a slightly more involved concept than for analog inputs, but it is still possible. The jammers which were quoted earlier are not real jammers: they are just simple noise-sources, and long range is a negative sales parameter, because they are intended for personal protection: a long range would increase the risk that they get detected. Their main customer base is drug-runners, fraudulent businessmen, infidel husbands and criminals sentenced to home-confinement with a GPS a ancle-bracelet. Many of those jammers does not work as well as advertised. Some of them are even trojaned and emit a signature signal for the benefit of law-enforcement. The infamous tv-preamp case was so efficient because it trippled the frequency of a local TV signal, due to instability, went into saturation/clipping and had a circular antenna with convenient dimensions to radiation of the resulting blanket of noise around the GPS frequency. Unfortunately, nobody tought about measuring its power-consumption or if they did, they didn't publish it. Given the kind of UHF transistors usually used in antenna-preamps, we are very likely talking no more than 1W. I an urban/hi-rise environment, havoc can be played with jammers that use glass facades as reflectors for the signal. The story about the Mexican LORAN-C jammer is instructive in how that complicates finding the trouble. GPS antennas on planes in the air do receive some help from being above it all, and pilots can still fly without GPS. The trouble starts once CATIII landings on GPS become routine. Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
GPS antennae are mounted top and bottom on tactical aircraft. Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Francesco Ledda Sent: 16 November 2009 00:37 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Considering that the GPS antenna in aircrafts is mounted on top of fuselage, and that its radiation pattern is upward, it seems that a ground jammer will have an uphill battle. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of J. Forster Sent: Sunday, November 15, 2009 6:28 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Or even into MP3 players, iPods, laptops, or cell phones. Then they'd wander all over the place too. With the latter two hosts, they could even be controlled remotely and even be fairly powerful. Would you notice having to recharge your battery a bit more often? -John === Magnus Danielson wrote: Chuck, Chuck Harris wrote: What makes you think it needs to be CW, and cannot be pulsed and chirped? May I roll in a noise jammer into the debate? Absolutely! They can be extremely power efficient. Raise the noise floor in the vicinity of the receiver, and it is all done. Probably the easiest solution would be to take a PN source and use it to drive a pulser that pulses a chirp oscillator. If you are feeling really polite, you could put a bandpass filter on the thing to protect other services. All it has to do is confuse the receiver enough so that you can't trust its readings. Depends on the goal. For some strategies, blackout is the goal, for some getting the readings go haywire every once in a while suffice. Agreed! My 9V battery suggestion was for a localized blackout device. You only have to make the receiver question each satellite's signal often enough for it to rule it out. No way is CW necessary, or even desirable. As John suggested, someone (say the Chinese) could put these things in battery operated stuffed animals, and set them up to jam a little bit now and then. After Xmas, the GPS landscape would be littered with these little stealth jammers, and willing supplicants to replace their batteries. -Chuck ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
From a friend and GPS expert: A *much* more effective and cheap strategy is a repeater jammer.. Receive the signal and retransmit it: two antennas and an amplifier. The victim sees the delayed retransmitted signal at a higher level than the direct one. It's sort of like creating fake multipath interference. No need for PN generators, oscillators, etc. Granted, a smart receiver that *understands* the relationship between SV to user geometry and doppler can beat it (because the carrier phase and PN phase of the repeated signal won't be consistent with the geometry), but the run of the mill PN tracking loop probably won't. Jim Lux is smart and knowledgeable, so naturally :-) he suggested a repeater jammer as I did. The implementation that he describes is the traditional one, in which separate transmitting and receiving antennas are used to avoid self-interference. I suggested a single-antenna form because I wanted the jammer to be compact and self-contained. Most inexpensive receivers use a single bit sampler, so a suitable CW tone could also probably jam it effectively, but might require some knowledge of the victim receiver to pick an appropriate frequency (i.e. You'd need to know the sampling rate.) Jim Lux is correct. A one-bit sampler is just a hard-limiter. Any signal in the passband that is stronger than the normal receiver input of background random noise plus GPS signals kills the sensitivity of the receiver by holding the output of the limiter against its high and low limits. (Normally, the hard-limiter dithers randomly between its limits, so that hard-limiting reduces the receiver's sensitivity by rather little, less than 2 dB IIRC.) The jamming signal does not have to be CW, but CW works. It is not difficult to excise CW signals by means of anti-jamming DSP; and sophisticated military receivers have such protection. However, anti-jamming processing is somewhat costly in terms of parts-count, complexity, and power-consumption. AFAIK, no commercial or civilian GPS receiver manufactured within the last 23 years has included such processing. The very first commercial/civilian GPS receivers, more than 25 years ago, _were_ quite immune to CW and other narrowband jamming; but this feature did not survive market price competition. Most inexpensive receivers are especially highly vulnerable to jamming by CW at or near 1575.42 MHz, the L1 carrier frequency, even when the jamming signal is not much stronger than a normal GPS-plus-random- background input (so that one-bit sampling is not an issue), because the C/A code correlation in these receivers is not 100% continuous. Once per millisecond, there is a dead time of few microseconds during which correlator outputs are read and correlator input parameters such as delay and delay-rate are updated. I have tested several makes and models of GPS receivers and been amazed by how little CW power was required to disable them -- typically 20 dB less than with full-time correlation. Again, this vulnerability is a consequence of cost- cutting pressure. -John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Lux, Jim (337C) wrote: A *much* more effective and cheap strategy is a repeater jammer.. Receive the signal and retransmit it: two antennas and an amplifier. The victim sees the delayed retransmitted signal at a higher level than the direct one. It's sort of like creating fake multipath interference. No need for PN generators, oscillators, etc. The delay attack is known (it's actually more of a spoofing attack), but most jamming uses just simple CW or noise signals. A problem with the delay attack is that you have a risc of creating a feedback loop which creates an unstable oscillation, which may or may not be what you would like. Among other things, directional finding on an oscillation is much easier than the delayed signal. However, a good hint is to use a directional L1 antenna and point it to the signal and just hook a receiver up and the position you have is that of the attackers antenna. Again that reveals the position. I guess this is why the attack isn't particularly used. Granted, a smart receiver that *understands* the relationship between SV to user geometry and doppler can beat it (because the carrier phase and PN phase of the repeated signal won't be consistent with the geometry), but the run of the mill PN tracking loop probably won't. Actually, even the simpler receivers has some resistance to it, the higher amplitude is the main problem. Most inexpensive receivers use a single bit sampler, so a suitable CW tone could also probably jam it effectively, but might require some knowledge of the victim receiver to pick an appropriate frequency (i.e. You'd need to know the sampling rate.) The CW attack is well known and has been analyzed fairly deeply. You don't need the sampling rate to make it efficient. The one-bit receiver is dead in the sea compared to even 1.5 bit receivers with suitable AGC loop detection. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
I agree with the commitment comment. Here in the UK we were just starting to see affordable Decca Navigator receivers using mdern (microprocessor) technology when they shut the system down. I prsonally think that the big driver is that the military don't use LORAN. They have GPS and inertial (ships as well as aircraft, even some land vehicles) and are content to let LORAN go. Robert G8RPI. --- On Sun, 15/11/09, b...@lysator.liu.se b...@lysator.liu.se wrote: From: b...@lysator.liu.se b...@lysator.liu.se Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) To: j...@quik.com, Discussion of precise time and frequency measurement time-nuts@febo.com Date: Sunday, 15 November, 2009, 7:28 John, If a LORAN transmitter were destroyed by a terrorist team, a backup could be in operation in hours. A damaged GPS system could easily take many months or even years to fix. -John A LORAN site, with a several hundred meter high mast, a small house full of transmitter, signal generation and Cs clock(s?)... on a remote Norwegian island... would not be back online within a few hours after an attack. GPS is supposed to work without _any_ terrestrial support for days or weeks. I doubt that anyone can get something lethal for the SVs up in orbit without making it very obvious who they are. GPS now has lots of hot spare birds in orbit, that a instantly online with one or a few satellites going bust. That said, I think LORAN should be kept running as a backup, also with a firm commitment that it WILL KEEP running for 10+ years, giving vendors a reason to develop modern receivers. -- Björn ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
b...@lysator.liu.se wrote: John, If a LORAN transmitter were destroyed by a terrorist team, a backup could be in operation in hours. A damaged GPS system could easily take many months or even years to fix. -John A LORAN site, with a several hundred meter high mast, a small house full of transmitter, signal generation and Cs clock(s?)... on a remote Norwegian island... would not be back online within a few hours after an attack. Regardless of location, it will take some time to restore functionality. About a year maybe. The LORAN-C station would reduce navigation in a certain area. However, since most interesting targets use GPS, it is a more interesting target. GPS is supposed to work without _any_ terrestrial support for days or weeks. I doubt that anyone can get something lethal for the SVs up in orbit without making it very obvious who they are. GPS now has lots of hot spare birds in orbit, that a instantly online with one or a few satellites going bust. The AutoNAV feature should keep it up for 180 days. It has never been used. Essentially, what if you wipe out the ground segment and needs to rebuild it. The ground segment points of GPS is fewer than the LORAN-C stations. Firing rockets to down the birds is above the average terrorist budget and infrastructure. While not all 30 GPS birds needs to go down, a significant number of them needs to for a significant system impact. Downing a single of them is sufficient for the political effect, so that is more likely. Using jammers is far more likely. It has been analyzed quite deeply. It is not impossible to locate a GPS jammer. In Iraq, they had relative high power jammers and they where able to locate them and finally take them out. That said, I think LORAN should be kept running as a backup, also with a firm commitment that it WILL KEEP running for 10+ years, giving vendors a reason to develop modern receivers. The electronics needed to support LORAN-C and eLORAN is not very complex by todays measure. Could be integrated with a GPS receiver. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
The bottom line is simple: the military don't need it, the FAA see no value in it; the avionics industry has discontinued the manufacturing of LORAN receivers years ago, the General Aviation community has bigger fish to fry (fight user fees); the Europen talked in the past about using LORAN for redundancy purposes, but never issued any concrete plans or requisitions. For all above reasons, LORAN is going to go. As a pilot, my personal experience about LORAN is mixed. Two times in heavy IMC, using RNAV LORAN, the LORAN went out in crytical phases of flight. This has never happened to me, with GPS. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of Magnus Danielson Sent: Sunday, November 15, 2009 9:01 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) b...@lysator.liu.se wrote: John, If a LORAN transmitter were destroyed by a terrorist team, a backup could be in operation in hours. A damaged GPS system could easily take many months or even years to fix. -John A LORAN site, with a several hundred meter high mast, a small house full of transmitter, signal generation and Cs clock(s?)... on a remote Norwegian island... would not be back online within a few hours after an attack. Regardless of location, it will take some time to restore functionality. About a year maybe. The LORAN-C station would reduce navigation in a certain area. However, since most interesting targets use GPS, it is a more interesting target. GPS is supposed to work without _any_ terrestrial support for days or weeks. I doubt that anyone can get something lethal for the SVs up in orbit without making it very obvious who they are. GPS now has lots of hot spare birds in orbit, that a instantly online with one or a few satellites going bust. The AutoNAV feature should keep it up for 180 days. It has never been used. Essentially, what if you wipe out the ground segment and needs to rebuild it. The ground segment points of GPS is fewer than the LORAN-C stations. Firing rockets to down the birds is above the average terrorist budget and infrastructure. While not all 30 GPS birds needs to go down, a significant number of them needs to for a significant system impact. Downing a single of them is sufficient for the political effect, so that is more likely. Using jammers is far more likely. It has been analyzed quite deeply. It is not impossible to locate a GPS jammer. In Iraq, they had relative high power jammers and they where able to locate them and finally take them out. That said, I think LORAN should be kept running as a backup, also with a firm commitment that it WILL KEEP running for 10+ years, giving vendors a reason to develop modern receivers. The electronics needed to support LORAN-C and eLORAN is not very complex by todays measure. Could be integrated with a GPS receiver. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
J. Forster j...@quik.com wrote: I've read and heard from this forum as well as a number of other sources that GPS can be easily jammed. What makes GPS so vulnerable? How can it be jammed? Signal strength. LORAN transmitters put out multi-hundred KW to MegaWatt class pulses. Wiki has a list. I would think a GPS bird puts out less than 100 Watts CW. Also, GPS birds are a LOT farther away, especially measured in wavelengths (much higher path loss) Those factors combine to make a huge difference in received power. It could well be over 100 dB. From what I've heard a GPS jammer smaller than a deck of playing cards can easily wipe out GPS w/in a mile or more for a week or longer. John It should be easy to locate a jammer. Go to the area where the GPS signal is being jammed. Drive in some direction until the signal is regained. Repeat to find three locations where the signal is lost. Three points define a circle. The diameter tells the strength of the jamming signal. The center defines the location. Once you are near the center, ordinary DF techniques should quickly identify the source. For faster response, have a number of GPS receivers report the status of the GPS signal to a central location. This would identify a moving jammer. It should also be possible to develop a GPS antenna with one or more nulls in the horizontal direction. Rotate the antenna until the GPS signal is regained. The null points to the jammer. Multiple receivers would remove the ambiguity from antennas with more than one null. These techniques should identify a jammer very quickly, perhaps in hours or minutes instead of weeks. I'm sure the military has some more advanced methods, as well as effective methods of dealing with the threat. Mike Monett ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Francesco Ledda wrote: The bottom line is simple: the military don't need it, the FAA see no value in it; the avionics industry has discontinued the manufacturing of LORAN receivers years ago, the General Aviation community has bigger fish to fry (fight user fees); the Europen talked in the past about using LORAN for redundancy purposes, but never issued any concrete plans or requisitions. For all above reasons, LORAN is going to go. The time for cutting the service will come eventually. While it has serviced us well, the use is not as heavy as previous years and it has essentially been replaced by GPS. It's sad to see it go, but in times when budget is tought good old systems gets killed. Eventually they need to. For those only having LORAN-C, the investment into a GPS receiver should not be too steep. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
I guess the point you folks aren't getting is you can make a very effective local GPS jammer that runs off of a 9V transistor radio battery, and will last for several weeks. It can be done for a total cost of a few bucks per jammer search the web, the designs are out there. Toss the GPS jammers indiscriminately around the landscape, and you put GPS out of business for a very low cost. -Chuck Harris Mike Monett wrote: It should be easy to locate a jammer. Go to the area where the GPS signal is being jammed. Drive in some direction until the signal is regained. Repeat to find three locations where the signal is lost. Three points define a circle. The diameter tells the strength of the jamming signal. The center defines the location. Once you are near the center, ordinary DF techniques should quickly identify the source. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
b...@lysator.liu.se wrote: John, If a LORAN transmitter were destroyed by a terrorist team, a backup could be in operation in hours. A damaged GPS system could easily take many months or even years to fix. -John The military have air deployable radio trucks. A LORAN station could be built into a few trailers, including generator, clocks, and transmitter. There are also fielded deployable masts. Such a station could be deployed rapidly. It would not have as powerful signal as the original station, but would, IMO, be fully functional. -John A LORAN site, with a several hundred meter high mast, a small house full of transmitter, signal generation and Cs clock(s?)... on a remote Norwegian island... would not be back online within a few hours after an attack. Regardless of location, it will take some time to restore functionality. About a year maybe. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
John, If a LORAN transmitter were destroyed by a terrorist team, a backup could be in operation in hours. A damaged GPS system could easily take many months or even years to fix. -John A LORAN site, with a several hundred meter high mast, a small house full of transmitter, signal generation and Cs clock(s?)... on a remote Norwegian island... would not be back online within a few hours after an attack. I think it'd still be a lot easier to replace quickly than GPS jammers widely seeded. What would happen if some rogue country started building mini-GPS jammers and giving them to insurgents to randomly scatter around. A single donkey could carry many hundreds? Or suppose a jammer was built into a child's toy and ran intermittantly off the toy's batteries and sold by the zillions at Walmart for Christmas? GPS is supposed to work without _any_ terrestrial support for days or weeks. I doubt that anyone can get something lethal for the SVs up in orbit without making it very obvious who they are. GPS now has lots of hot spare birds in orbit, that a instantly online with one or a few satellites going bust. I've never suggested attacking the birds is a credible terrorist threat. It is not, IMO. That said, I think LORAN should be kept running as a backup, also with a firm commitment that it WILL KEEP running for 10+ years, giving vendors a reason to develop modern receivers. -- Björn IMO, GPS is much more vulnerable to a jamming attack and LORAN must be maintained as a backup. FWIW, -John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Thanks Chuck, My point EXACTLY. 1. It's well within the capability of dozens of countries or organizations or even individuals. 2. They are trivial to distribute widely, and could be piggy-backed onto other things. 3. Given enough of them with random on-off cycles, you'd force a giant game of Whak-A-Mole. A guy in his basement could easily build 100 in a week given a design and PCB layout. In another week he could scatter them all over a city, even if travelling by bus. The whole operation would cost under a few thousand dollars. Furthermore, it would not be needed to kill all the GPS in an area, all the time. Making it unreliable would likely be enough. FWIW, -John == I guess the point you folks aren't getting is you can make a very effective local GPS jammer that runs off of a 9V transistor radio battery, and will last for several weeks. It can be done for a total cost of a few bucks per jammer search the web, the designs are out there. Toss the GPS jammers indiscriminately around the landscape, and you put GPS out of business for a very low cost. -Chuck Harris Mike Monett wrote: It should be easy to locate a jammer. Go to the area where the GPS signal is being jammed. Drive in some direction until the signal is regained. Repeat to find three locations where the signal is lost. Three points define a circle. The diameter tells the strength of the jamming signal. The center defines the location. Once you are near the center, ordinary DF techniques should quickly identify the source. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
After reading all the responses on this thread, all I can think of is the numerous ideas you folks have given some whackjob out there. Keep up the good work. 73, Dick, W1KSZ -Original Message- From: Chuck Harris cfhar...@erols.com Sent: Nov 15, 2009 9:51 AM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) I guess the point you folks aren't getting is you can make a very effective local GPS jammer that runs off of a 9V transistor radio battery, and will last for several weeks. It can be done for a total cost of a few bucks per jammer search the web, the designs are out there. Toss the GPS jammers indiscriminately around the landscape, and you put GPS out of business for a very low cost. -Chuck Harris Mike Monett wrote: It should be easy to locate a jammer. Go to the area where the GPS signal is being jammed. Drive in some direction until the signal is regained. Repeat to find three locations where the signal is lost. Three points define a circle. The diameter tells the strength of the jamming signal. The center defines the location. Once you are near the center, ordinary DF techniques should quickly identify the source. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
I just put jamming GPS into Google, and got about 348,000 hits. -John After reading all the responses on this thread, all I can think of is the numerous ideas you folks have given some whackjob out there. Keep up the good work. 73, Dick, W1KSZ -Original Message- From: Chuck Harris cfhar...@erols.com Sent: Nov 15, 2009 9:51 AM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) I guess the point you folks aren't getting is you can make a very effective local GPS jammer that runs off of a 9V transistor radio battery, and will last for several weeks. It can be done for a total cost of a few bucks per jammer search the web, the designs are out there. Toss the GPS jammers indiscriminately around the landscape, and you put GPS out of business for a very low cost. -Chuck Harris Mike Monett wrote: It should be easy to locate a jammer. Go to the area where the GPS signal is being jammed. Drive in some direction until the signal is regained. Repeat to find three locations where the signal is lost. Three points define a circle. The diameter tells the strength of the jamming signal. The center defines the location. Once you are near the center, ordinary DF techniques should quickly identify the source. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Exposing vulnerabilities always make for a more secure product. Hiding known security risks or possible avenues of sabotage only creates a false sense of security. I'd rather know how vulnerable GPS is and have paper maps charts than have the false sense of security it's an untouchable system because it's high up in space or any other argument of redundancy, etc. Bottom line is, talking about the possible vulnerabilities for technical purposes isn't giving the enemy any ideas they don't already have. China shot down a weather satellite a few years ago testing a rocket. You don't think there was an underlying message to that? Believe me, The enemy has ideas AND capabilities we haven't even come close to covering. And my opinion, Maybe Obama should take one less flight to Europe talking down about his own nation and spend that 190M on supporting LORAN for the next 10 years (obviously inflated flight costs but you get the picture) Lets face it, the arugment about saving money shouldn't start on cancelling FUNCTIONAL and NECESSARY programs. There's plenty of earmarks, bailouts and other waste that we could EASILY cancel to come up with the 190M required to keep this NAVIGATION system online another decade. Just my two cents. Regards, Scott CISSP. From: time-nuts-boun...@febo.com on behalf of Richard W. Solomon Sent: Sun 11/15/2009 12:26 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) After reading all the responses on this thread, all I can think of is the numerous ideas you folks have given some whackjob out there. Keep up the good work. 73, Dick, W1KSZ -Original Message- From: Chuck Harris cfhar...@erols.com Sent: Nov 15, 2009 9:51 AM To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) I guess the point you folks aren't getting is you can make a very effective local GPS jammer that runs off of a 9V transistor radio battery, and will last for several weeks. It can be done for a total cost of a few bucks per jammer search the web, the designs are out there. Toss the GPS jammers indiscriminately around the landscape, and you put GPS out of business for a very low cost. -Chuck Harris Mike Monett wrote: It should be easy to locate a jammer. Go to the area where the GPS signal is being jammed. Drive in some direction until the signal is regained. Repeat to find three locations where the signal is lost. Three points define a circle. The diameter tells the strength of the jamming signal. The center defines the location. Once you are near the center, ordinary DF techniques should quickly identify the source. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
In message 1078.12.6.201.222.1258304694.squir...@popacctsnew.quik.com, J. Fo rster writes: The military have air deployable radio trucks. A LORAN station could be built into a few trailers, including generator, clocks, and transmitter. There are also fielded deployable masts. In fact, that is pretty much how the original LORAN was built... There are some very good stories about this on: http://www.loran-history.info/default.asp Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
In message e1n9i6k-0005pl...@meow.febo.com, Mike Monett writes: It should be easy to locate a jammer. Go to the area where the GPS signal is being jammed. Drive in some direction until the signal is regained. Repeat to find three locations where the signal is lost. Experience has shown that this is far from as easy as that. For one thing, you have no assurance that the jammer has isotropic propagation and your local geometry obstructions will determine the subset of sats you have access to. In military excercises, I have been told the average time to find a jammer is on the order of many hours in an simulated urban setting, due to propagation and access issues. Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Chuck Harris wrote: I guess the point you folks aren't getting is you can make a very effective local GPS jammer that runs off of a 9V transistor radio battery, and will last for several weeks. It can be done for a total cost of a few bucks per jammer search the web, the designs are out there. We've known about it for years. Toss the GPS jammers indiscriminately around the landscape, and you put GPS out of business for a very low cost. Exactly. You can manufacture hundreds of them and disperse them around. Finding one of those is easy. Having many tens of them around makes it harder. Even if you find several of them, it will take the battery-time for the attack to go away completly. The strategy for such an attack and the strategy to deal with such an attack is a bit different. A military receiver has about 40 dB better suppression just from the coding gain alone (30 dB for C/A and 70 dB for P(Y) if my memory serves me right). A number of other concerns also needs to be dealt with naturally, For obvious reasons alot of effort has been spent on covering this field, and if you are looking, there is alot of material out there. The trouble is that civilian infrastructure does not have the countermeasures at the disposal to the military (US or allied forces). If the civilian infrastructure was limited to a few handfull sites, the modern keying receivers intended for civilian usage would solve part of the problem, but there is a limit to how widely dispersed such receivers can be and also there is such a wide usage. Even lacking such counter-measures, the ability to just detect and warn about lacking reception conditions is less than acceptable in many systems. This details prohibits effective use of other reasnoble countermeasures. Let's recall that interference also can be of non-intentional sort. Also, the huge use of GPS makes it a target for a certain operation, while unintentional targets may also suffer. The trouble is that GPS receivers works too well. Install and forget. Awareness of risk or even the ability to identify what sub-systems even depend on it is limited. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
In message 11603302.1258306016911.javamail.r...@elwamui-hound.atl.sa.earthlink .net, Richard W. Solomon writes: After reading all the responses on this thread, all I can think of is the numerous ideas you folks have given some whackjob out there. I don't think you are up to date, all the whack-jobs have GPS jammers already. The first one was documented along with schematics and all in 2600 magazine 15 years ago or so... -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
In message 4b004084.5060...@rubidium.dyndns.org, Magnus Danielson writes: Chuck Harris wrote: The trouble is that civilian infrastructure [...] That's actually not the biggest problem, the biggest problem is access. If you put a jammer at the top of a tall building (by RC helicopter ?) getting up there to pick it up is non trivial for the people hunting it, they may need court orders to get access to service stairs etc. Strictly speaking here in Denmark, the police would not have authority to kick in a door to stop a GPS jammer, until the PTT has found it a spectrum violation, warned the owner of the premises, possibly in writing, if it is a rental building. It is not obvious that a signal strong enough to jam GPS would necessarily be found to be a spectrum violation in the first place. Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Chuck Harris wrote: I guess the point you folks aren't getting is you can make a very effective local GPS jammer that runs off of a 9V transistor radio battery, and will last for several weeks. It can be done for a total cost of a few bucks per jammer search the web, the designs are out there. We've known about it for years. Toss the GPS jammers indiscriminately around the landscape, and you put GPS out of business for a very low cost. Exactly. You can manufacture hundreds of them and disperse them around. Finding one of those is easy. Having many tens of them around makes it harder. Even if you find several of them, it will take the battery-time for the attack to go away completly. The strategy for such an attack and the strategy to deal with such an attack is a bit different. Not so. You can easily buy a 1F or more capacitor. Take a small box, like a juice box, put a few solar cells on it and a 1F cap and jammer with a pseudo random on-off timer inside and deploy. Bingo... a headache for years. -John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
On Sun, Nov 15, 2009 at 11:37:11AM -0500, Mike Monett wrote: It should be easy to locate a jammer. Go to the area where the GPS signal is being jammed. Drive in some direction until the signal is regained. Repeat to find three locations where the signal is lost. Three points define a circle. The diameter tells the strength of the jamming signal. The center defines the location. And if the jammer is attached to, saY a radiosonde balloon or other light aircraft and the footprint covers most of the US? Stop thinking terrestrially. 73, Majdi, N0RMZ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
In message 20091115193126.gb5...@puck.nether.net, Majdi S. Abbas writes: On Sun, Nov 15, 2009 at 11:37:11AM -0500, Mike Monett wrote: And if the jammer is attached to, saY a radiosonde balloon or other light aircraft and the footprint covers most of the US? It doesn't. Hint: http://blogs.techrepublic.com.com/geekend/?p=372 -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Given that I learned the techniques from a bunch of wack-jobs, I don't think I have upped the learning curve much. -Chuck Richard W. Solomon wrote: After reading all the responses on this thread, all I can think of is the numerous ideas you folks have given some whackjob out there. Keep up the good work. 73, Dick, W1KSZ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
What makes you think it needs to be CW, and cannot be pulsed and chirped? All it has to do is confuse the receiver enough so that you can't trust its readings. -Chuck Mike Monett wrote: Chuck Harris cfhar...@erols.com wrote: I guess the point you folks aren't getting is you can make a very effective local GPS jammer that runs off of a 9V transistor radio battery, and will last for several weeks. It can be done for a total cost of a few bucks per jammer search the web, the designs are out there. Toss the GPS jammers indiscriminately around the landscape, and you put GPS out of business for a very low cost. -Chuck Harris I'm not so sure that would be very effective. A typical 9v alkaline contains about 900 milliamp/hours at low current drain. Two weeks is 24 * 7 * 2 = 336 hrs. Assuming 100% efficiency, the battery would supply 0.9 / 336 = 0.00267A, or 0.024 watt, not including the drop in voltage after the first few dozen hours. There are quite a few commercial jammers designed specifically to jam GPS signals. These are extremely illegal, but they do give some idea of the range that could be expected. Below is a list of the specified range and power. I calculate the highest ratio to get the meters per watt. GMW12 Cellular GPS L1 Jammer Block cellular signals and GPS L1 system in the same time Jamming Range : Average 40 meters radius Output Power : Total 6.5 Watt ratio : 40/6.5 = 6.15 meters/watt http://www.tayx.co.uk/gmw12-gps-mobile-jammer.html KYG0014 Fixed Jammer Output Power : 2000mw Jamming Range : 15~20 meters ratio : 20/2 = 10 meters/watt http://www.alibaba.com/product-gs/204091726/Fixed_GPS_jammer.html KYG0017 Powerful GPS signal jammer Output power : 25W Range: radius 100-300meters ratio : 300 / 25 = 12 meters/watt http://www.alibaba.com/product-gs/213377763/Powerful_GPS_signal_jammer.html KYG0013 Car GPS jammer Output power : 800mW Range: radius 10-15 meters ratio : 15 / 0.8 = 8.75 meters/watt http://www.alibaba.com/product-gs/204037628/KYG0013_Car_GPS_jammer.html KYP0050 Handheld GPS/GSM signal Jammer / blocker output power : 300mw jamming range : 2~10 meters ratio : 10 / 0.3 = 33.33 meters/watt http://www.alibaba.com/product-gs/206648711/KYP0050_Handheld_GPS_GSM_signal_Jammer_blocker.html The average ratio is: (33.33 + 8.75 + 8.75 + 12 + 10 + 6.15) / 6 = 13.16 meters/watt. The highest claimed performance is the KYP0050, with 33 meters/watt. Assuming the 9V battery jammer has 100% RF efficiency and equal ratio, the jamming range would be 33.33 * 0.024 = 0.799 meters or about 2.62 feet. However, a jammer would require crystal control to stay on frequency. There are no crystals for L1, so a multiplier would be needed. The actual power output would be much lower, so the range would be much less. Another example, a 1500mAh rechargable pocket jammer has a 5 meter range, and only lasts 2~3 hrs: GMT04 Pocket GPS Jammer Jaming Range : Average 5 meters radius Current Voltage : 200mA DC12V / AC120~140V Battery : 1,500mAh battery life 2~3 hours, recharge needs 3~4 hours http://www.tayx.co.uk/gmt04-pocket-gps-jammer.html So a 9V transistor radio battery jammer doesn't seem like it would present much of a danger. Mike Monett ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Chuck, Chuck Harris wrote: What makes you think it needs to be CW, and cannot be pulsed and chirped? May I roll in a noise jammer into the debate? All it has to do is confuse the receiver enough so that you can't trust its readings. Depends on the goal. For some strategies, blackout is the goal, for some getting the readings go haywire every once in a while suffice. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Chuck Harris cfhar...@erols.com wrote: I guess the point you folks aren't getting is you can make a very effective local GPS jammer that runs off of a 9V transistor radio battery, and will last for several weeks. It can be done for a total cost of a few bucks per jammer search the web, the designs are out there. Toss the GPS jammers indiscriminately around the landscape, and you put GPS out of business for a very low cost. -Chuck Harris I'm not so sure that would be very effective. A typical 9v alkaline contains about 900 milliamp/hours at low current drain. Two weeks is 24 * 7 * 2 = 336 hrs. Assuming 100% efficiency, the battery would supply 0.9 / 336 = 0.00267A, or 0.024 watt, not including the drop in voltage after the first few dozen hours. There are quite a few commercial jammers designed specifically to jam GPS signals. These are extremely illegal, but they do give some idea of the range that could be expected. Below is a list of the specified range and power. I calculate the highest ratio to get the meters per watt. GMW12 Cellular GPS L1 Jammer Block cellular signals and GPS L1 system in the same time Jamming Range : Average 40 meters radius Output Power : Total 6.5 Watt ratio : 40/6.5 = 6.15 meters/watt http://www.tayx.co.uk/gmw12-gps-mobile-jammer.html KYG0014 Fixed Jammer Output Power : 2000mw Jamming Range : 15~20 meters ratio : 20/2 = 10 meters/watt http://www.alibaba.com/product-gs/204091726/Fixed_GPS_jammer.html KYG0017 Powerful GPS signal jammer Output power : 25W Range: radius 100-300meters ratio : 300 / 25 = 12 meters/watt http://www.alibaba.com/product-gs/213377763/Powerful_GPS_signal_jammer.html KYG0013 Car GPS jammer Output power : 800mW Range: radius 10-15 meters ratio : 15 / 0.8 = 8.75 meters/watt http://www.alibaba.com/product-gs/204037628/KYG0013_Car_GPS_jammer.html KYP0050 Handheld GPS/GSM signal Jammer / blocker output power : 300mw jamming range : 2~10 meters ratio : 10 / 0.3 = 33.33 meters/watt http://www.alibaba.com/product-gs/206648711/KYP0050_Handheld_GPS_GSM_signal_Jammer_blocker.html The average ratio is: (33.33 + 8.75 + 8.75 + 12 + 10 + 6.15) / 6 = 13.16 meters/watt. The highest claimed performance is the KYP0050, with 33 meters/watt. Assuming the 9V battery jammer has 100% RF efficiency and equal ratio, the jamming range would be 33.33 * 0.024 = 0.799 meters or about 2.62 feet. However, a jammer would require crystal control to stay on frequency. There are no crystals for L1, so a multiplier would be needed. The actual power output would be much lower, so the range would be much less. Another example, a 1500mAh rechargable pocket jammer has a 5 meter range, and only lasts 2~3 hrs: GMT04 Pocket GPS Jammer Jaming Range : Average 5 meters radius Current Voltage : 200mA DC12V / AC120~140V Battery : 1,500mAh battery life 2~3 hours, recharge needs 3~4 hours http://www.tayx.co.uk/gmt04-pocket-gps-jammer.html So a 9V transistor radio battery jammer doesn't seem like it would present much of a danger. Mike Monett ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Magnus Danielson wrote: Chuck, Chuck Harris wrote: What makes you think it needs to be CW, and cannot be pulsed and chirped? May I roll in a noise jammer into the debate? Absolutely! They can be extremely power efficient. Raise the noise floor in the vicinity of the receiver, and it is all done. Probably the easiest solution would be to take a PN source and use it to drive a pulser that pulses a chirp oscillator. If you are feeling really polite, you could put a bandpass filter on the thing to protect other services. All it has to do is confuse the receiver enough so that you can't trust its readings. Depends on the goal. For some strategies, blackout is the goal, for some getting the readings go haywire every once in a while suffice. Agreed! My 9V battery suggestion was for a localized blackout device. You only have to make the receiver question each satellite's signal often enough for it to rule it out. No way is CW necessary, or even desirable. As John suggested, someone (say the Chinese) could put these things in battery operated stuffed animals, and set them up to jam a little bit now and then. After Xmas, the GPS landscape would be littered with these little stealth jammers, and willing supplicants to replace their batteries. -Chuck ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Or even into MP3 players, iPods, laptops, or cell phones. Then they'd wander all over the place too. With the latter two hosts, they could even be controlled remotely and even be fairly powerful. Would you notice having to recharge your battery a bit more often? -John === Magnus Danielson wrote: Chuck, Chuck Harris wrote: What makes you think it needs to be CW, and cannot be pulsed and chirped? May I roll in a noise jammer into the debate? Absolutely! They can be extremely power efficient. Raise the noise floor in the vicinity of the receiver, and it is all done. Probably the easiest solution would be to take a PN source and use it to drive a pulser that pulses a chirp oscillator. If you are feeling really polite, you could put a bandpass filter on the thing to protect other services. All it has to do is confuse the receiver enough so that you can't trust its readings. Depends on the goal. For some strategies, blackout is the goal, for some getting the readings go haywire every once in a while suffice. Agreed! My 9V battery suggestion was for a localized blackout device. You only have to make the receiver question each satellite's signal often enough for it to rule it out. No way is CW necessary, or even desirable. As John suggested, someone (say the Chinese) could put these things in battery operated stuffed animals, and set them up to jam a little bit now and then. After Xmas, the GPS landscape would be littered with these little stealth jammers, and willing supplicants to replace their batteries. -Chuck ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Considering that the GPS antenna in aircrafts is mounted on top of fuselage, and that its radiation pattern is upward, it seems that a ground jammer will have an uphill battle. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of J. Forster Sent: Sunday, November 15, 2009 6:28 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Or even into MP3 players, iPods, laptops, or cell phones. Then they'd wander all over the place too. With the latter two hosts, they could even be controlled remotely and even be fairly powerful. Would you notice having to recharge your battery a bit more often? -John === Magnus Danielson wrote: Chuck, Chuck Harris wrote: What makes you think it needs to be CW, and cannot be pulsed and chirped? May I roll in a noise jammer into the debate? Absolutely! They can be extremely power efficient. Raise the noise floor in the vicinity of the receiver, and it is all done. Probably the easiest solution would be to take a PN source and use it to drive a pulser that pulses a chirp oscillator. If you are feeling really polite, you could put a bandpass filter on the thing to protect other services. All it has to do is confuse the receiver enough so that you can't trust its readings. Depends on the goal. For some strategies, blackout is the goal, for some getting the readings go haywire every once in a while suffice. Agreed! My 9V battery suggestion was for a localized blackout device. You only have to make the receiver question each satellite's signal often enough for it to rule it out. No way is CW necessary, or even desirable. As John suggested, someone (say the Chinese) could put these things in battery operated stuffed animals, and set them up to jam a little bit now and then. After Xmas, the GPS landscape would be littered with these little stealth jammers, and willing supplicants to replace their batteries. -Chuck ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Chuck Harris wrote: Magnus Danielson wrote: Chuck, Chuck Harris wrote: What makes you think it needs to be CW, and cannot be pulsed and chirped? May I roll in a noise jammer into the debate? Absolutely! They can be extremely power efficient. Raise the noise floor in the vicinity of the receiver, and it is all done. Probably the easiest solution would be to take a PN source and use it to drive a pulser that pulses a chirp oscillator. If you are feeling really polite, you could put a bandpass filter on the thing to protect other services. The schematic out there is a PN source feeding an OCXO and then amplified. Crystal loop to keep fairly centered. More or less the same as personalized phone jammers do. Very simple design. All it has to do is confuse the receiver enough so that you can't trust its readings. Depends on the goal. For some strategies, blackout is the goal, for some getting the readings go haywire every once in a while suffice. Agreed! My 9V battery suggestion was for a localized blackout device. You only have to make the receiver question each satellite's signal often enough for it to rule it out. No way is CW necessary, or even desirable. True. As John suggested, someone (say the Chinese) could put these things in battery operated stuffed animals, and set them up to jam a little bit now and then. After Xmas, the GPS landscape would be littered with these little stealth jammers, and willing supplicants to replace their batteries. Well, then you have to consider what the potential gain would be from such an attack. I fail to see the upside of that particular scenario. It would draw the attention over to them and in a field I think they rather stay calm about. Their ability to pull it off as such should not be doubted, but their resoning for it. Rather inefficient actually. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Even 10 KM is pretty useful. If the thing were solar powered with a supercap battery it could easly transmit for say 2 minutes per hour w/ significant power. It'd be hard to find if the on times were generated by a multiple fedback CMOS shift register. -John Mike Instead of relying on the dubious claims of those marketing an extremely inefficient jammer it would be better to actually do some simple calculations. Typical commercial receivers stop tracking with a Jam to signal ratio of not more than 60dB or so: http://www.gpsworld.com/gps/jamming-gps-778 The input signal level at the receiver input is around -160dBW. A 1W ERP source with an isotropic hemispheric radiation pattern will exceed the the required jamming signal strength for distances less than several tens of kilometers. This estimate is consistent with the fact that LO parasitic radiation from TV systems on boats have been known to jam GPS for distances of several kilometers. Bruce Mike Monett wrote: Chuck Harriscfhar...@erols.com wrote: I guess the point you folks aren't getting is you can make a very effective local GPS jammer that runs off of a 9V transistor radio battery, and will last for several weeks. It can be done for a total cost of a few bucks per jammer search the web, the designs are out there. Toss the GPS jammers indiscriminately around the landscape, and you put GPS out of business for a very low cost. -Chuck Harris I'm not so sure that would be very effective. A typical 9v alkaline contains about 900 milliamp/hours at low current drain. Two weeks is 24 * 7 * 2 = 336 hrs. Assuming 100% efficiency, the battery would supply 0.9 / 336 = 0.00267A, or 0.024 watt, not including the drop in voltage after the first few dozen hours. There are quite a few commercial jammers designed specifically to jam GPS signals. These are extremely illegal, but they do give some idea of the range that could be expected. Below is a list of the specified range and power. I calculate the highest ratio to get the meters per watt. GMW12 Cellular GPS L1 Jammer Block cellular signals and GPS L1 system in the same time Jamming Range : Average 40 meters radius Output Power : Total 6.5 Watt ratio : 40/6.5 = 6.15 meters/watt http://www.tayx.co.uk/gmw12-gps-mobile-jammer.html KYG0014 Fixed Jammer Output Power : 2000mw Jamming Range : 15~20 meters ratio : 20/2 = 10 meters/watt http://www.alibaba.com/product-gs/204091726/Fixed_GPS_jammer.html KYG0017 Powerful GPS signal jammer Output power : 25W Range: radius 100-300meters ratio : 300 / 25 = 12 meters/watt http://www.alibaba.com/product-gs/213377763/Powerful_GPS_signal_jammer.html KYG0013 Car GPS jammer Output power : 800mW Range: radius 10-15 meters ratio : 15 / 0.8 = 8.75 meters/watt http://www.alibaba.com/product-gs/204037628/KYG0013_Car_GPS_jammer.html KYP0050 Handheld GPS/GSM signal Jammer / blocker output power : 300mw jamming range : 2~10 meters ratio : 10 / 0.3 = 33.33 meters/watt http://www.alibaba.com/product-gs/206648711/KYP0050_Handheld_GPS_GSM_signal_Jammer_blocker.html The average ratio is: (33.33 + 8.75 + 8.75 + 12 + 10 + 6.15) / 6 = 13.16 meters/watt. The highest claimed performance is the KYP0050, with 33 meters/watt. Assuming the 9V battery jammer has 100% RF efficiency and equal ratio, the jamming range would be 33.33 * 0.024 = 0.799 meters or about 2.62 feet. However, a jammer would require crystal control to stay on frequency. There are no crystals for L1, so a multiplier would be needed. The actual power output would be much lower, so the range would be much less. Another example, a 1500mAh rechargable pocket jammer has a 5 meter range, and only lasts 2~3 hrs: GMT04 Pocket GPS Jammer Jaming Range : Average 5 meters radius Current Voltage : 200mA DC12V / AC120~140V Battery : 1,500mAh battery life 2~3 hours, recharge needs 3~4 hours http://www.tayx.co.uk/gmt04-pocket-gps-jammer.html So a 9V transistor radio battery jammer doesn't seem like it would present much of a danger. Mike Monett ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Chuck Harris cfhar...@erols.com wrote: What makes you think it needs to be CW, and cannot be pulsed and chirped? All it has to do is confuse the receiver enough so that you can't trust its readings. -Chuck I said nothing about the type of modulation. The equipment I listed is designed specifically to disrupt GPS. Presumably they use whatever modulation method that gives the best results. However, GPS is spread-spectrum, so it inherently rejects noise that is not correlated with the satellite signal. This means effective jamming requires a lot more power than is available from a 9V transistor radio battery, and even then, the range is only a few meters. I made an error in calculating the average range per watt. The original shows 8.75 meters/watt twice: (33.33 + 8.75 + 8.75 + 12 + 10 + 6.15) / 6 = 13.16 meters/watt. It should be (33.33 + 8.75 + 12 + 10 + 6.15) / 5 = 14.046 meters/watt. This does not affect the conclusion, which is it takes a lot more power to disrupt GPS than it first appears. Putting jammers in Christmas toys would accomplish little except to drain the batteries faster. Mike Monett ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Jamming Range : Average 40 meters radius Output Power : Total 6.5 Watt ratio : 40/6.5 = 6.15 meters/watt Isn't received power 1/R-squared? I think those calculations should be radius-squared/watts I find it interesting that the products designed as jammers have ranges of only a few 10s of meters while a recent message here said 1/2 mile from a digital-radio link that was transmitting on 315 MHz. (aka designed for something else rather than as a jammer) Similarly, the Monterey Bay jammer wasn't trying to be a jammer, and it wiped out a huge area. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Mike Instead of relying on the dubious claims of those marketing an extremely inefficient jammer it would be better to actually do some simple calculations. Typical commercial receivers stop tracking with a Jam to signal ratio of not more than 60dB or so: http://www.gpsworld.com/gps/jamming-gps-778 The input signal level at the receiver input is around -160dBW. A 1W ERP source with an isotropic hemispheric radiation pattern will exceed the the required jamming signal strength for distances less than several tens of kilometers. This estimate is consistent with the fact that LO parasitic radiation from TV systems on boats have been known to jam GPS for distances of several kilometers. Bruce Mike Monett wrote: Chuck Harriscfhar...@erols.com wrote: I guess the point you folks aren't getting is you can make a very effective local GPS jammer that runs off of a 9V transistor radio battery, and will last for several weeks. It can be done for a total cost of a few bucks per jammer search the web, the designs are out there. Toss the GPS jammers indiscriminately around the landscape, and you put GPS out of business for a very low cost. -Chuck Harris I'm not so sure that would be very effective. A typical 9v alkaline contains about 900 milliamp/hours at low current drain. Two weeks is 24 * 7 * 2 = 336 hrs. Assuming 100% efficiency, the battery would supply 0.9 / 336 = 0.00267A, or 0.024 watt, not including the drop in voltage after the first few dozen hours. There are quite a few commercial jammers designed specifically to jam GPS signals. These are extremely illegal, but they do give some idea of the range that could be expected. Below is a list of the specified range and power. I calculate the highest ratio to get the meters per watt. GMW12 Cellular GPS L1 Jammer Block cellular signals and GPS L1 system in the same time Jamming Range : Average 40 meters radius Output Power : Total 6.5 Watt ratio : 40/6.5 = 6.15 meters/watt http://www.tayx.co.uk/gmw12-gps-mobile-jammer.html KYG0014 Fixed Jammer Output Power : 2000mw Jamming Range : 15~20 meters ratio : 20/2 = 10 meters/watt http://www.alibaba.com/product-gs/204091726/Fixed_GPS_jammer.html KYG0017 Powerful GPS signal jammer Output power : 25W Range: radius 100-300meters ratio : 300 / 25 = 12 meters/watt http://www.alibaba.com/product-gs/213377763/Powerful_GPS_signal_jammer.html KYG0013 Car GPS jammer Output power : 800mW Range: radius 10-15 meters ratio : 15 / 0.8 = 8.75 meters/watt http://www.alibaba.com/product-gs/204037628/KYG0013_Car_GPS_jammer.html KYP0050 Handheld GPS/GSM signal Jammer / blocker output power : 300mw jamming range : 2~10 meters ratio : 10 / 0.3 = 33.33 meters/watt http://www.alibaba.com/product-gs/206648711/KYP0050_Handheld_GPS_GSM_signal_Jammer_blocker.html The average ratio is: (33.33 + 8.75 + 8.75 + 12 + 10 + 6.15) / 6 = 13.16 meters/watt. The highest claimed performance is the KYP0050, with 33 meters/watt. Assuming the 9V battery jammer has 100% RF efficiency and equal ratio, the jamming range would be 33.33 * 0.024 = 0.799 meters or about 2.62 feet. However, a jammer would require crystal control to stay on frequency. There are no crystals for L1, so a multiplier would be needed. The actual power output would be much lower, so the range would be much less. Another example, a 1500mAh rechargable pocket jammer has a 5 meter range, and only lasts 2~3 hrs: GMT04 Pocket GPS Jammer Jaming Range : Average 5 meters radius Current Voltage : 200mA DC12V / AC120~140V Battery : 1,500mAh battery life 2~3 hours, recharge needs 3~4 hours http://www.tayx.co.uk/gmt04-pocket-gps-jammer.html So a 9V transistor radio battery jammer doesn't seem like it would present much of a danger. Mike Monett ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
See my earlier post. Briefly: Antennas do not have an infinite front-to-back ratio. (40 dB) The path loss from a surface jammer to a plane (10 miles) is many, many dB less than from plane to bird (15,000 miles). -John Considering that the GPS antenna in aircrafts is mounted on top of fuselage, and that its radiation pattern is upward, it seems that a ground jammer will have an uphill battle. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of J. Forster Sent: Sunday, November 15, 2009 6:28 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Or even into MP3 players, iPods, laptops, or cell phones. Then they'd wander all over the place too. With the latter two hosts, they could even be controlled remotely and even be fairly powerful. Would you notice having to recharge your battery a bit more often? -John === Magnus Danielson wrote: Chuck, Chuck Harris wrote: What makes you think it needs to be CW, and cannot be pulsed and chirped? May I roll in a noise jammer into the debate? Absolutely! They can be extremely power efficient. Raise the noise floor in the vicinity of the receiver, and it is all done. Probably the easiest solution would be to take a PN source and use it to drive a pulser that pulses a chirp oscillator. If you are feeling really polite, you could put a bandpass filter on the thing to protect other services. All it has to do is confuse the receiver enough so that you can't trust its readings. Depends on the goal. For some strategies, blackout is the goal, for some getting the readings go haywire every once in a while suffice. Agreed! My 9V battery suggestion was for a localized blackout device. You only have to make the receiver question each satellite's signal often enough for it to rule it out. No way is CW necessary, or even desirable. As John suggested, someone (say the Chinese) could put these things in battery operated stuffed animals, and set them up to jam a little bit now and then. After Xmas, the GPS landscape would be littered with these little stealth jammers, and willing supplicants to replace their batteries. -Chuck ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Hal Murray wrote: cfhar...@erols.com said: What makes you think it needs to be CW, and cannot be pulsed and chirped? All it has to do is confuse the receiver enough so that you can't trust its readings. Why is pulse or chirp likely to be more confusing per W of jamming power? I thought the GPS signal was spread spectrum so I wouldn't expect any simple pulse or chirp to be better at jamming than noise over the appropriate bandwidth. If you know the spread spectrum details (which must be public or the receiver can't listen to the signal), then you might be able to mimic a satellite signal. I think that needs the time, so you probably need to listen to the signal you are jamming. Am I on the right track? Is there a trick I'm missing? (If so, how complicated is it?) I think you are running into the jamming/spoofing definition of the problem. When you are jamming, you are transmitting a signal which just overshadows the propper signal but when you are spoofing you try to send a signal which looks like the propper signal. A spoofing attack is a different story altogether. For a spoofer to confuse a receiver, it either needs to be there when the receiver turns on or the spoofer needs to transmitt signals having a position so near the receivers current signals that it can't discriminate them and then track onto the wrong signals. The counter-measure towards spoofers is to used a keyed signal, in which case only delayed signal is available to the attacker, but for most cases the receiver should be able to handle that. For jamming I think chirps or phase-noise transmitters is effective since they select no particular feature of the spreading code, but induces error into both the weak and strong features, which is then shifted by the expected doppler frequency. The sensitivity of jamming energy for various offsets from the carrier for a pseudo-random sequence can be retrieved by Fourier-transform (DFT). Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
J. Forster wrote: Or even into MP3 players, iPods, laptops, or cell phones. Then they'd wander all over the place too. With the latter two hosts, they could even be controlled remotely and even be fairly powerful. Would you notice having to recharge your battery a bit more often? There is one report in which the laptops of ambulances had CPU frequencies in the neighborhood (1,5 GHz or 1,6 GHz if I recall correctly) of the GPS band and the GPS receiver lost tracking so they essentially lost functionality. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Francesco Ledda wrote: Considering that the GPS antenna in aircrafts is mounted on top of fuselage, and that its radiation pattern is upward, it seems that a ground jammer will have an uphill battle. Not all GPS receivers is sitting on flying airplanes. Far from it. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Mike, A defective TV antenna preamp (oscillating in an uncontrolled manner), on board a boat in California wiped out GPS for several kilometers! Because it only wiped it out when the owner was watching TV, the interferrence went on for months. This is well documented. Do a google search and you will find the report from the guys that found the jammer. When a modern high sensitivity GPS receiver cannot get a fix through the shingled roof of a house, you have to understand that the signals are really weak. The folks selling commercial GPS jammers are being rather brutish with their methods. They are using sledge hammers where a little tack hammer would do nicely. -Chuck Mike Monett wrote: Chuck Harris cfhar...@erols.com wrote: What makes you think it needs to be CW, and cannot be pulsed and chirped? All it has to do is confuse the receiver enough so that you can't trust its readings. -Chuck I said nothing about the type of modulation. The equipment I listed is designed specifically to disrupt GPS. Presumably they use whatever modulation method that gives the best results. However, GPS is spread-spectrum, so it inherently rejects noise that is not correlated with the satellite signal. This means effective jamming requires a lot more power than is available from a 9V transistor radio battery, and even then, the range is only a few meters. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
GPS receivers have considerable coding gain, which makes it possible for them to detect such low signals in the first place. The jamming signal will not benefit from the coding gain because it does not have the right coding and will be uncorrelated to the actual spread-spectrum signals the receiver is tracking. This is probably 30 dB or more. Also, you assume that your jammer has a similar antenna gain and radiation efficiency as the GPS transmitter on the satellite, that is unlikely. Bottom line, it is unlikely that a jammer running off a 9V battery, even on a baloon will jam the entire US for weeks. Can we go back to timing now? My 9V battery is running out... Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. Forster Sent: Sunday, November 15, 2009 6:51 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) See my earlier post. Briefly: Antennas do not have an infinite front-to-back ratio. (40 dB) The path loss from a surface jammer to a plane (10 miles) is many, many dB less than from plane to bird (15,000 miles). -John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Magnus Danielson wrote: Well, then you have to consider what the potential gain would be from such an attack. I fail to see the upside of that particular scenario. It would draw the attention over to them and in a field I think they rather stay calm about. Their ability to pull it off as such should not be doubted, but their resoning for it. Rather inefficient actually. The Chinese seem to have a difficulty worrying about the ethics of some of the things they do towards others. Some simple examples would be the lead in paints and plastics used in toys, melamine powder in milk, and pet food, pork flavored cardboard in frozen dumplings, tainted raw ingredients for heprin, the list goes on and on. It may not be in the nation's political interests to jam our GPS signals through toys, or other devices, but ... from what I have seen thus far, you could easily find several dozen manufacturers in China that would be willing to turn a blind eye to such a trojan payload in return for a few bucks. -Chuck Harris ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Maybe, but what happens if the GPS in a large metropolitan area that is overflown by a mix including General Aviation goes wonky? LA comes to mind because there is a lot of north-south traffic directly over LAX. -John === The one the counts ARE! ;) -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Sunday, November 15, 2009 7:03 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Francesco Ledda wrote: Considering that the GPS antenna in aircrafts is mounted on top of fuselage, and that its radiation pattern is upward, it seems that a ground jammer will have an uphill battle. Not all GPS receivers is sitting on flying airplanes. Far from it. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Not all GPSs are on airplanes, but those I am really worried about are. I don't care if the GPS receiver in my cell phone stops working in some locations, it does not work everywhere to begin with (like in the house, I can't use it to find the bathroom in the dark...), but I worry that the one guiding a missile or a fighter plane might not work. I also worry that the one abord a large passenger aircraft might not work. Most of those that are stationary or move on the ground or on water, I am not too worried about. For instance, the local garbage pickup people use GPS to locate the houses of customers who have unusual (large or unsafe, or possibly contaminating) garbage to pickup. I have had a dead TV on the side of my house for 3 weeks, three times I called and 3 times they missed it because the GPS guided them to my front door (my normal mailing address), but I live on a corner lot and the garbage pickup is on the side of the house, by the garage. If that particular GPS receiver stopped working and forced the employees to look around, it would not bother me (the TV ended up in the trash can. After 3 times and 3 weeks, I assumed I had done a reasonable attempt at avoiding putting too much lead in the garbage, and it had to go.) Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Sunday, November 15, 2009 7:03 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Francesco Ledda wrote: Considering that the GPS antenna in aircrafts is mounted on top of fuselage, and that its radiation pattern is upward, it seems that a ground jammer will have an uphill battle. Not all GPS receivers is sitting on flying airplanes. Far from it. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Hal Murray wrote: cfhar...@erols.com said: What makes you think it needs to be CW, and cannot be pulsed and chirped? All it has to do is confuse the receiver enough so that you can't trust its readings. Why is pulse or chirp likely to be more confusing per W of jamming power? Perhaps this reference will answer some of the questions present here: http://www.navcomtech.com/Support/Download/Sapphire%20Jamming%20Test%20Report%208%20Jan%202007v3.pdf One factor I have not seen anyone address is the effectiveness of jamming as a function of the receiver state. A GPS receiver will be much more susceptible to jamming when it is trying to acquire and lock onto a satellite signal than it is after lock and tracking has been achieved. Bruce, WB9ANQ -- Bruce Rahn Wisdom has two parts: 1. having a lot to say; and 2. not saying it! ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
The one the counts ARE! ;) -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Sunday, November 15, 2009 7:03 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Francesco Ledda wrote: Considering that the GPS antenna in aircrafts is mounted on top of fuselage, and that its radiation pattern is upward, it seems that a ground jammer will have an uphill battle. Not all GPS receivers is sitting on flying airplanes. Far from it. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Contrary to popular belief, us pilots do know how to fly without GPS. I have never seen an IFR aircraft with a GPS that didn't also have a VOR receiver. Any VFR aircraft can be navigated using the Mk I eyeball. IFR certified GPSes have integrity monitoring. So, if the signal gets jammed or there is another system failure, the approach should be aborted and the flight switched to another navigation means. This LORAN debate is all well and good, but most of the general aviation fleet does not have LORAN receivers. They haven't been manufactured in years. On Sun, Nov 15, 2009 at 8:33 PM, Didier Juges did...@cox.net wrote: Not all GPSs are on airplanes, but those I am really worried about are. I don't care if the GPS receiver in my cell phone stops working in some locations, it does not work everywhere to begin with (like in the house, I can't use it to find the bathroom in the dark...), but I worry that the one guiding a missile or a fighter plane might not work. I also worry that the one abord a large passenger aircraft might not work. Most of those that are stationary or move on the ground or on water, I am not too worried about. For instance, the local garbage pickup people use GPS to locate the houses of customers who have unusual (large or unsafe, or possibly contaminating) garbage to pickup. I have had a dead TV on the side of my house for 3 weeks, three times I called and 3 times they missed it because the GPS guided them to my front door (my normal mailing address), but I live on a corner lot and the garbage pickup is on the side of the house, by the garage. If that particular GPS receiver stopped working and forced the employees to look around, it would not bother me (the TV ended up in the trash can. After 3 times and 3 weeks, I assumed I had done a reasonable attempt at avoiding putting too much lead in the garbage, and it had to go.) Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Sunday, November 15, 2009 7:03 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Francesco Ledda wrote: Considering that the GPS antenna in aircrafts is mounted on top of fuselage, and that its radiation pattern is upward, it seems that a ground jammer will have an uphill battle. Not all GPS receivers is sitting on flying airplanes. Far from it. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Mike, Mike Monett wrote: I said nothing about the type of modulation. The equipment I listed is designed specifically to disrupt GPS. Presumably they use whatever modulation method that gives the best results. However, GPS is spread-spectrum, so it inherently rejects noise that is not correlated with the satellite signal. This means effective jamming requires a lot more power than is available from a 9V transistor radio battery, and even then, the range is only a few meters. The power of de-correlation is related to the length of the pseudo-random sequence. This relates back to the codes auto-correlation shape. The C/A code has a length of 1023 chips, giving a correlation gain of about 30 dB. The P code has a length of 7*86400*10,23E6 chips (a GPS week) but only fraction of that can be used for de-correlation. Looking at the detailed codes, the vunerability of C/A codes is worse, for PRN 1 the suppression is only -22,71 dB at 42 kHz sideband. But these coding gains comes to no use if the input is saturated for most of the times. Simple AGC strategies would allow the AGC to be captured by the CW signal for instance. Lack of filtering would allow out-of-bandwidth signals to infect the input etc. etc. Pre-digitalization code de-correlation is less sensitive to jamming, but comes at the price of 3 times number of channels analog decorrelators and integrators. Then again, it only solves part of the problem. The tracking threshold of the particular receiver in its environment has a huge effect. Support systems such as clock, movement sensors etc. can allow for tighter loop filters and thus allow the channels having a lower threshold and that would aid in the jamming resistance too. Regardless, the code-lengths isn't a particular good measure on the resistance to jamming. The P(Y) code is only about 10 dB better than C/A code in that respect, and M code gives another dB or so. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
The commercial jammers referred to in an earlier post advertise 10 to 45m or so range, with significant power levels and battery life measured in a few hours. Considering that these devices are illegal to begin with, I have to assume that these figures are probably optimistic (optimistic advertisement is probably the least of their concern.) If I were a pilot, I would probably be more worried about the kid playing with his Nintendo in 15A (or his father trying to retrieve his email with his GSM smart phone) during approach than a jammer on the ground. Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. Forster Sent: Sunday, November 15, 2009 6:38 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Even 10 KM is pretty useful. If the thing were solar powered with a supercap battery it could easly transmit for say 2 minutes per hour w/ significant power. It'd be hard to find if the on times were generated by a multiple fedback CMOS shift register. -John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Didier As jammers those devices are extremely inefficient. They may well rely on the inefficient generation and radiation of a very high order harmonic of the clock of an unshielded legal device. A commercial GPS receiver may require a signal as small as 60dB (depends on the operating mode, and receiver design) above the GPS signal at the receiver input. An ERP of a few microwatts should suffice to achieve the claimed range. Bruce Didier Juges wrote: The commercial jammers referred to in an earlier post advertise 10 to 45m or so range, with significant power levels and battery life measured in a few hours. Considering that these devices are illegal to begin with, I have to assume that these figures are probably optimistic (optimistic advertisement is probably the least of their concern.) If I were a pilot, I would probably be more worried about the kid playing with his Nintendo in 15A (or his father trying to retrieve his email with his GSM smart phone) during approach than a jammer on the ground. Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. Forster Sent: Sunday, November 15, 2009 6:38 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Even 10 KM is pretty useful. If the thing were solar powered with a supercap battery it could easly transmit for say 2 minutes per hour w/ significant power. It'd be hard to find if the on times were generated by a multiple fedback CMOS shift register. -John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
I think the problem with the Monterey Bay jammer was that he was jamming the DGPS correction signal, not the GPS signal itself. The DGPS correction signal is sent over the UHF band. Most marine GPS are DGPS because they need the better resolution it provides, particularly to find buoys and channel markers in the fog. The DGPS correction signal does not benefit from the spread-spectrum modulation and associated jamming resistance of the GPS signal itself. Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Sunday, November 15, 2009 6:30 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Jamming Range : Average 40 meters radius Output Power : Total 6.5 Watt ratio : 40/6.5 = 6.15 meters/watt Isn't received power 1/R-squared? I think those calculations should be radius-squared/watts I find it interesting that the products designed as jammers have ranges of only a few 10s of meters while a recent message here said 1/2 mile from a digital-radio link that was transmitting on 315 MHz. (aka designed for something else rather than as a jammer) Similarly, the Monterey Bay jammer wasn't trying to be a jammer, and it wiped out a huge area. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
On Sun, Nov 15, 2009 at 08:22:50PM -0600, Didier Juges wrote: I think the problem with the Monterey Bay jammer was that he was jamming the DGPS correction signal, not the GPS signal itself. The DGPS correction signal is sent over the UHF band. Most marine GPS are DGPS because they need the better resolution it provides, particularly to find buoys and channel markers in the fog. The DGPS correction signal does not benefit from the spread-spectrum modulation and associated jamming resistance of the GPS signal itself. That is the first I've heard of a UHF DGPS correction transmission can you provide a frequency and modulation mode ?Most I know of are re purposed LF NDBs or similar transmitters in the 200 to 400 KHz or so range that transmit a PSK'd carrier with the DGPS data at fairly low speed on it. I have heard of cases of wide area GPS outages noted by many folks with NON DGPS receivers (DGPS receivers mostly will just indicate no DGPS available and still show a pretty good position) that were caused by UHF signals on the L2 frequency... though I am sure there are incidents of accidental interference to LF or other distribution of DGPS. -- Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass 02493 An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Bruce, I agree with your calculation and conclusion, as far as commercial consumer GPS receivers are concerned. A data sheet that was linked in a previous post for an aviation-grade commercial GPS receiver indicated resistance to signals -30dBm at the receiver input. That is quite considerable, and much better than the hand-held consumer units (by 30dB?) I would expect planes and other potential high value targets to have receivers of similar performance. I don't disagree that it would be fairly easy to disrupt the consumer devices, but other than a few missed appointments and frustrated gadget freaks, and the occasional emergency vehicle not finding its way to the scene of an accident, that would be more of a problem) I am not too worried about the consequences of that. The thread started with the loss of the LORAN system, and nobody (maybe I am going out on a limb here) ever used a LORAN receiver in his car to find the nearest restaurant :) I think the people who should complain the most about the loss of LORAN are the boaters, but they are the one who embrassed GPS the first and are it's biggest advocates!!! I know, I live on the coast of Florida. Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: Sunday, November 15, 2009 8:21 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Didier As jammers those devices are extremely inefficient. They may well rely on the inefficient generation and radiation of a very high order harmonic of the clock of an unshielded legal device. A commercial GPS receiver may require a signal as small as 60dB (depends on the operating mode, and receiver design) above the GPS signal at the receiver input. An ERP of a few microwatts should suffice to achieve the claimed range. Bruce Didier Juges wrote: The commercial jammers referred to in an earlier post advertise 10 to 45m or so range, with significant power levels and battery life measured in a few hours. Considering that these devices are illegal to begin with, I have to assume that these figures are probably optimistic (optimistic advertisement is probably the least of their concern.) If I were a pilot, I would probably be more worried about the kid playing with his Nintendo in 15A (or his father trying to retrieve his email with his GSM smart phone) during approach than a jammer on the ground. Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of J. Forster Sent: Sunday, November 15, 2009 6:38 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Even 10 KM is pretty useful. If the thing were solar powered with a supercap battery it could easly transmit for say 2 minutes per hour w/ significant power. It'd be hard to find if the on times were generated by a multiple fedback CMOS shift register. -John ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
My first contact with LORAN was at the bankrupcy of a local company that supplied tracking and location services for trucking companies. The trucks had a receiver that sent data back to home base via two-way radio and home pbase computed positions. I was only nteresteed in buying their mimis. In the early 80s I was playing around with uP (8085) based LORAN receivers (Made by Appelco/Raytheon). One version read out time differences and a more advanced (w/ 2x 8085s) version read out Lat Long directly. Either would pinpoint my location to 100' class. It was accurate navigation in a two-way radio sized box. There were, of course, no map or chart displays. Imagine what 20+ years of development would have brought. -John = Bruce, I agree with your calculation and conclusion, as far as commercial consumer GPS receivers are concerned. A data sheet that was linked in a previous post for an aviation-grade commercial GPS receiver indicated resistance to signals -30dBm at the receiver input. That is quite considerable, and much better than the hand-held consumer units (by 30dB?) I would expect planes and other potential high value targets to have receivers of similar performance. I don't disagree that it would be fairly easy to disrupt the consumer devices, but other than a few missed appointments and frustrated gadget freaks, and the occasional emergency vehicle not finding its way to the scene of an accident, that would be more of a problem) I am not too worried about the consequences of that. The thread started with the loss of the LORAN system, and nobody (maybe I am going out on a limb here) ever used a LORAN receiver in his car to find the nearest restaurant :) I think the people who should complain the most about the loss of LORAN are the boaters, but they are the one who embrassed GPS the first and are it's biggest advocates!!! I know, I live on the coast of Florida. Didier ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
On Sun, Nov 15, 2009 at 08:56:36PM -0600, Didier Juges wrote: I don't disagree that it would be fairly easy to disrupt the consumer devices, but other than a few missed appointments and frustrated gadget freaks, and the occasional emergency vehicle not finding its way to the scene of an accident, that would be more of a problem) I am not too worried about the consequences of that. GPS has been widely used for time and frequency sync in radio systems of various sorts - some depend on it for successful simulcast from multiple transmitters (including many public safety radio systems) and while there is SUPPOSED to be significant holdover, there is are always those situations where nobody has EVER checked that it works... And what will holdover do about LONG TERM outages of GPS ? Perhaps folks are willing to bet the whole infrastructure on the supposition that we could NEVER see a complete long term loss of signal (using civilian receivers with modest anti jam abilities) in a particular location or region - I am not exactly sure what alternative might exist though I guess there are some for time and frequency - terrestrial GPS beacons from high points that could lock up a cell system in a region come to mind... And more and more and more stuff depends on more or less ignorant and sometimes not very bright operators expecting that the GPS positions are always there or they don't know what to do. And if GPS is almost always reliably there there may well be little or no practical training about what to do if it fails. Failure modes and paths in code and procedures (and sometimes even actual hardware) which aren't often tested or exercised usually fail when actually needed and often in entirely unanticipated ways - maybe the backup ALSO depends on GPS in some way the system designers never thought about (or knew could happen)... LORAN C represents a viable (albeit not often deployed) backup to time and frequency control and could be implemented in modern hardware as a backup location service at reasonably low cost for those applications where that is important enough. The thread started with the loss of the LORAN system, and nobody (maybe I am going out on a limb here) ever used a LORAN receiver in his car to find the nearest restaurant :) Actually readers of this list have, though not in recent times I guess. I think the people who should complain the most about the loss of LORAN are the boaters, but they are the one who embrassed GPS the first and are it's biggest advocates!!! I know, I live on the coast of Florida. An enhanced LORAN that has some of the accuracy and automation of a GPS receiver exists... I suspect boaters care most about convenience (and accuracy) and found GPS easier. Certainly so compared to earlier LORAN C gear. And of course there is another issue with GPS, it is controlled by the DOD and is supposed to have the ability to deny service in a region if conditions are sufficiently apocalyptic to require it. For folks worried about this (more outside than inside the US obviously) LORAN is a local resource they may control and certainly can if they make a more or less modest investment in the ability to do so. Some (large) players are of course planning their own space based systems for just this reason but LORAN can be implemented by most nation states... -- Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass 02493 An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
On Sun, Nov 15, 2009 at 07:17:37PM -0800, J. Forster wrote: There were, of course, no map or chart displays. Imagine what 20+ years of development would have brought. E Loran could supply the same basic position information as input to charting and mapping software as GPS does... most of the code doesn't care where the position came from one wit But I am sure you know that (we are in violant agreement). -John -- Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass 02493 An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
In fact, GPS has performed so well, it has become part of the furniture and it is really hard now to assess the full impact its loss would have. Another overlooked aspect would be the perceived impact of a number of failures. Just look at the hoohaws over lead in toys, defective cribs, tainted beef, tainted pet food, flamable kids sleepware, trace chemicals in bottles and many other things. LORAN is cheap insurance, IMO. A modern dual receiver could compare LORAN and GPS positions to provide very high confidence levels at low incremental cost. -John = On Sun, Nov 15, 2009 at 08:56:36PM -0600, Didier Juges wrote: I don't disagree that it would be fairly easy to disrupt the consumer devices, but other than a few missed appointments and frustrated gadget freaks, and the occasional emergency vehicle not finding its way to the scene of an accident, that would be more of a problem) I am not too worried about the consequences of that. GPS has been widely used for time and frequency sync in radio systems of various sorts - some depend on it for successful simulcast from multiple transmitters (including many public safety radio systems) and while there is SUPPOSED to be significant holdover, there is are always those situations where nobody has EVER checked that it works... And what will holdover do about LONG TERM outages of GPS ? Perhaps folks are willing to bet the whole infrastructure on the supposition that we could NEVER see a complete long term loss of signal (using civilian receivers with modest anti jam abilities) in a particular location or region - I am not exactly sure what alternative might exist though I guess there are some for time and frequency - terrestrial GPS beacons from high points that could lock up a cell system in a region come to mind... And more and more and more stuff depends on more or less ignorant and sometimes not very bright operators expecting that the GPS positions are always there or they don't know what to do. And if GPS is almost always reliably there there may well be little or no practical training about what to do if it fails. Failure modes and paths in code and procedures (and sometimes even actual hardware) which aren't often tested or exercised usually fail when actually needed and often in entirely unanticipated ways - maybe the backup ALSO depends on GPS in some way the system designers never thought about (or knew could happen)... LORAN C represents a viable (albeit not often deployed) backup to time and frequency control and could be implemented in modern hardware as a backup location service at reasonably low cost for those applications where that is important enough. The thread started with the loss of the LORAN system, and nobody (maybe I am going out on a limb here) ever used a LORAN receiver in his car to find the nearest restaurant :) Actually readers of this list have, though not in recent times I guess. I think the people who should complain the most about the loss of LORAN are the boaters, but they are the one who embrassed GPS the first and are it's biggest advocates!!! I know, I live on the coast of Florida. An enhanced LORAN that has some of the accuracy and automation of a GPS receiver exists... I suspect boaters care most about convenience (and accuracy) and found GPS easier. Certainly so compared to earlier LORAN C gear. And of course there is another issue with GPS, it is controlled by the DOD and is supposed to have the ability to deny service in a region if conditions are sufficiently apocalyptic to require it. For folks worried about this (more outside than inside the US obviously) LORAN is a local resource they may control and certainly can if they make a more or less modest investment in the ability to do so. Some (large) players are of course planning their own space based systems for just this reason but LORAN can be implemented by most nation states... -- Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass 02493 An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
A *much* more effective and cheap strategy is a repeater jammer.. Receive the signal and retransmit it: two antennas and an amplifier. The victim sees the delayed retransmitted signal at a higher level than the direct one. It's sort of like creating fake multipath interference. No need for PN generators, oscillators, etc. Granted, a smart receiver that *understands* the relationship between SV to user geometry and doppler can beat it (because the carrier phase and PN phase of the repeated signal won't be consistent with the geometry), but the run of the mill PN tracking loop probably won't. Most inexpensive receivers use a single bit sampler, so a suitable CW tone could also probably jam it effectively, but might require some knowledge of the victim receiver to pick an appropriate frequency (i.e. You'd need to know the sampling rate.) On 11/15/09 4:39 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Chuck Harris wrote: Magnus Danielson wrote: Chuck, Chuck Harris wrote: What makes you think it needs to be CW, and cannot be pulsed and chirped? May I roll in a noise jammer into the debate? Absolutely! They can be extremely power efficient. Raise the noise floor in the vicinity of the receiver, and it is all done. Probably the easiest solution would be to take a PN source and use it to drive a pulser that pulses a chirp oscillator. If you are feeling really polite, you could put a bandpass filter on the thing to protect other services. The schematic out there is a PN source feeding an OCXO and then amplified. Crystal loop to keep fairly centered. More or less the same as personalized phone jammers do. Very simple design. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
With SA off, the difference between marine DGPS and stand alone GPS is not that significant. If my memory serves me right the Monterey jammer did jam at L1. -- Björn I think the problem with the Monterey Bay jammer was that he was jamming the DGPS correction signal, not the GPS signal itself. The DGPS correction signal is sent over the UHF band. Most marine GPS are DGPS because they need the better resolution it provides, particularly to find buoys and channel markers in the fog. The DGPS correction signal does not benefit from the spread-spectrum modulation and associated jamming resistance of the GPS signal itself. Didier -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Sunday, November 15, 2009 6:30 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) Jamming Range : Average 40 meters radius Output Power : Total 6.5 Watt ratio : 40/6.5 = 6.15 meters/watt Isn't received power 1/R-squared? I think those calculations should be radius-squared/watts I find it interesting that the products designed as jammers have ranges of only a few 10s of meters while a recent message here said 1/2 mile from a digital-radio link that was transmitting on 315 MHz. (aka designed for something else rather than as a jammer) Similarly, the Monterey Bay jammer wasn't trying to be a jammer, and it wiped out a huge area. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Bruce, I agree with your calculation and conclusion, as far as commercial consumer GPS receivers are concerned. A data sheet that was linked in a previous post for an aviation-grade commercial GPS receiver indicated resistance to signals -30dBm at the receiver input. That is quite considerable, and much better than the hand-held consumer units (by 30dB?) I would be very surprised if aviation-grade receivers are better than your new average handheld Garmin. I would expect planes and other potential high value targets to have receivers of similar performance. I would expect the opposite, since important receivers - say for timing of power generation, timing of bankingsystems, etc typically runs forever often beeing 5 to ten years old before uppgrading. -- Björn ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
David I. Emery wrote: I have emailed my brother in law who is a rear admiral (I think now called a vice admiral) and currently CFO of the USCG (and as a note re your alma mater a MIT Sloan grad) and rather loudly said so myself. He most likely was part of the group that made the decision... I intend to ask him why they did it when I next see him. David, I see three possibilities: a) modernization (E-LORAN), b) maintain existing service and capabilities, c) shut it down. It would be helpful to know if USCG supports the plan to shut the system down. If USCG does not, those of us who are US citizens can lobby Congress to restore funding for the service. There's an educational piece here to do. -ch ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
AOPA is pushing congress to repristinate funding for LORAN. General aviation is probably the heaviest user on this Nav system. The aviation user community would love to see Nav systems with integrated LORAN and GPS capabilty, but the industry has done little in this area, due to lack of government commitment to LORAN. The FAA knows the GPS can be easily jammed, but has done nothing do push LORAN as the GPS backup system. Sent from my iPhone On Nov 14, 2009, at 2:40 PM, Christopher Hoover c...@murgatroid.com wrote: David I. Emery wrote: I have emailed my brother in law who is a rear admiral (I think now called a vice admiral) and currently CFO of the USCG (and as a note re your alma mater a MIT Sloan grad) and rather loudly said so myself. He most likely was part of the group that made the decision... I intend to ask him why they did it when I next see him. David, I see three possibilities: a) modernization (E-LORAN), b) maintain existing service and capabilities, c) shut it down. It would be helpful to know if USCG supports the plan to shut the system down. If USCG does not, those of us who are US citizens can lobby Congress to restore funding for the service. There's an educational piece here to do. -ch ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
You've hit it on the nose. NONE of them are interested in anything but social issues. LORAN will not get any of them re-elected, and that's all any of 'em care about. Don J. Forster Does anybody know who in Congress might take the lead in reversing the decision? None of the reps in this state are at all likely to give a damn. Their interest is apparently only in social issues. -John = AOPA is pushing congress to repristinate funding for LORAN. General aviation is probably the heaviest user on this Nav system. The aviation user community would love to see Nav systems with integrated LORAN and GPS capabilty, but the industry has done little in this area, due to lack of government commitment to LORAN. The FAA knows the GPS can be easily jammed, but has done nothing do push LORAN as the GPS backup system. Sent from my iPhone On Nov 14, 2009, at 2:40 PM, Christopher Hoover c...@murgatroid.com wrote: David I. Emery wrote: I have emailed my brother in law who is a rear admiral (I think now called a vice admiral) and currently CFO of the USCG (and as a note re your alma mater a MIT Sloan grad) and rather loudly said so myself. He most likely was part of the group that made the decision... I intend to ask him why they did it when I next see him. David, I see three possibilities: a) modernization (E-LORAN), b) maintain existing service and capabilities, c) shut it down. It would be helpful to know if USCG supports the plan to shut the system down. If USCG does not, those of us who are US citizens can lobby Congress to restore funding for the service. There's an educational piece here to do. -ch ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
OK, so who is in a position to MAKE them care? How about those who understand this is a Homeland Security (among other) issue? Perhaps FOX news? Likely LORAN costs about as much a year as a mile of fence along the Mexican border, probably less. FWIW, -John You've hit it on the nose. NONE of them are interested in anything but social issues. LORAN will not get any of them re-elected, and that's all any of 'em care about. Don J. Forster Does anybody know who in Congress might take the lead in reversing the decision? None of the reps in this state are at all likely to give a damn. Their interest is apparently only in social issues. -John = AOPA is pushing congress to repristinate funding for LORAN. General aviation is probably the heaviest user on this Nav system. The aviation user community would love to see Nav systems with integrated LORAN and GPS capabilty, but the industry has done little in this area, due to lack of government commitment to LORAN. The FAA knows the GPS can be easily jammed, but has done nothing do push LORAN as the GPS backup system. Sent from my iPhone On Nov 14, 2009, at 2:40 PM, Christopher Hoover c...@murgatroid.com wrote: David I. Emery wrote: I have emailed my brother in law who is a rear admiral (I think now called a vice admiral) and currently CFO of the USCG (and as a note re your alma mater a MIT Sloan grad) and rather loudly said so myself. He most likely was part of the group that made the decision... I intend to ask him why they did it when I next see him. David, I see three possibilities: a) modernization (E-LORAN), b) maintain existing service and capabilities, c) shut it down. It would be helpful to know if USCG supports the plan to shut the system down. If USCG does not, those of us who are US citizens can lobby Congress to restore funding for the service. There's an educational piece here to do. -ch ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
John, I have asked Alaska's representitives to reinstate LORAN funding due to the large number of private pilots and small fishing boat operators that rely on LORAN in Alaska. During periods of high aurora activity in the arctic the interference with GPS makes it unusable and LORAN is the only viable alternative navigation system. Richard Does anybody know who in Congress might take the lead in reversing the decision? None of the reps in this state are at all likely to give a damn. Their interest is apparently only in social issues. -John = AOPA is pushing congress to repristinate funding for LORAN. General aviation is probably the heaviest user on this Nav system. The aviation user community would love to see Nav systems with integrated LORAN and GPS capabilty, but the industry has done little in this area, due to lack of government commitment to LORAN. The FAA knows the GPS can be easily jammed, but has done nothing do push LORAN as the GPS backup system. Sent from my iPhone On Nov 14, 2009, at 2:40 PM, Christopher Hoover c...@murgatroid.com wrote: David I. Emery wrote: I have emailed my brother in law who is a rear admiral (I think now called a vice admiral) and currently CFO of the USCG (and as a note re your alma mater a MIT Sloan grad) and rather loudly said so myself. He most likely was part of the group that made the decision... I intend to ask him why they did it when I next see him. David, I see three possibilities: a) modernization (E-LORAN), b) maintain existing service and capabilities, c) shut it down. It would be helpful to know if USCG supports the plan to shut the system down. If USCG does not, those of us who are US citizens can lobby Congress to restore funding for the service. There's an educational piece here to do. -ch ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
I was thinking about the costs side as well. From the 2010 budget info I have been able to find, The savings could top $36 million in 2010, with something like $190M over the following 5 years. I think that the GPS birds are far more than that to maintain and replace. I found the following in a May 2009 article which indicates there may even be some question on the GPS service quality in the near future. The U.S. Government Accountability Office has identified that the USAF-run GPS satellite constellation is in trouble. There are currently 30 satellites in orbit, the 24 needed for the system and six spares, which sounds like enough to run the system. The problem is that many of the satellites are getting old and will need replacing soon or will fail. The USAF has a program to replace the satellites, but it is US$1B over budget and almost three years behind schedule. U.S. Government Accountability Office recently said that it is uncertain whether the air force will be able to acquire new satellites in time to maintain current GPS service without interruption...there will be an increased likelihood that in 2010, as old satellites begin to fail, the overall GPS constellation will fall below the number of satellites required to provide the level of GPS service that the U.S. government commits to. Why not keep LORAN and drop one spare bird. - Original Message - From: J. Forster j...@quik.com To: Don Latham d...@montana.com Cc: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, November 14, 2009 11:35 PM Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) OK, so who is in a position to MAKE them care? How about those who understand this is a Homeland Security (among other) issue? Perhaps FOX news? Likely LORAN costs about as much a year as a mile of fence along the Mexican border, probably less. FWIW, -John You've hit it on the nose. NONE of them are interested in anything but social issues. LORAN will not get any of them re-elected, and that's all any of 'em care about. Don J. Forster Does anybody know who in Congress might take the lead in reversing the decision? None of the reps in this state are at all likely to give a damn. Their interest is apparently only in social issues. -John = AOPA is pushing congress to repristinate funding for LORAN. General aviation is probably the heaviest user on this Nav system. The aviation user community would love to see Nav systems with integrated LORAN and GPS capabilty, but the industry has done little in this area, due to lack of government commitment to LORAN. The FAA knows the GPS can be easily jammed, but has done nothing do push LORAN as the GPS backup system. Sent from my iPhone On Nov 14, 2009, at 2:40 PM, Christopher Hoover c...@murgatroid.com wrote: David I. Emery wrote: I have emailed my brother in law who is a rear admiral (I think now called a vice admiral) and currently CFO of the USCG (and as a note re your alma mater a MIT Sloan grad) and rather loudly said so myself. He most likely was part of the group that made the decision... I intend to ask him why they did it when I next see him. David, I see three possibilities: a) modernization (E-LORAN), b) maintain existing service and capabilities, c) shut it down. It would be helpful to know if USCG supports the plan to shut the system down. If USCG does not, those of us who are US citizens can lobby Congress to restore funding for the service. There's an educational piece here to do. -ch ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Somehow, I think they will keep GPS running whatever the cost. There is a huge civilian constituency (everybody who cannot or is too lazy to read a map) and relies on GPS to guide their Lexus to the nearest Starbucks. Also, the military needs it to guide and target munitions. The initial Afgahnistan victories over the Taliban would have been impossible without GPS and the Special Forces teams. The folly of the decision will likely not become apparent until there is a major tragedy of some kind. Frankly, I doubt that $190 M would buy a single GPS bird and launch today. -John I was thinking about the costs side as well. From the 2010 budget info I have been able to find, The savings could top $36 million in 2010, with something like $190M over the following 5 years. I think that the GPS birds are far more than that to maintain and replace. I found the following in a May 2009 article which indicates there may even be some question on the GPS service quality in the near future. The U.S. Government Accountability Office has identified that the USAF-run GPS satellite constellation is in trouble. There are currently 30 satellites in orbit, the 24 needed for the system and six spares, which sounds like enough to run the system. The problem is that many of the satellites are getting old and will need replacing soon or will fail. The USAF has a program to replace the satellites, but it is US$1B over budget and almost three years behind schedule. U.S. Government Accountability Office recently said that it is uncertain whether the air force will be able to acquire new satellites in time to maintain current GPS service without interruption...there will be an increased likelihood that in 2010, as old satellites begin to fail, the overall GPS constellation will fall below the number of satellites required to provide the level of GPS service that the U.S. government commits to. Why not keep LORAN and drop one spare bird. - Original Message - From: J. Forster j...@quik.com To: Don Latham d...@montana.com Cc: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, November 14, 2009 11:35 PM Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) OK, so who is in a position to MAKE them care? How about those who understand this is a Homeland Security (among other) issue? Perhaps FOX news? Likely LORAN costs about as much a year as a mile of fence along the Mexican border, probably less. FWIW, -John You've hit it on the nose. NONE of them are interested in anything but social issues. LORAN will not get any of them re-elected, and that's all any of 'em care about. Don J. Forster Does anybody know who in Congress might take the lead in reversing the decision? None of the reps in this state are at all likely to give a damn. Their interest is apparently only in social issues. -John = AOPA is pushing congress to repristinate funding for LORAN. General aviation is probably the heaviest user on this Nav system. The aviation user community would love to see Nav systems with integrated LORAN and GPS capabilty, but the industry has done little in this area, due to lack of government commitment to LORAN. The FAA knows the GPS can be easily jammed, but has done nothing do push LORAN as the GPS backup system. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Indeed the uscg did agree to shut it down. They signed off on it. On Sat, Nov 14, 2009 at 3:40 PM, Christopher Hoover c...@murgatroid.comwrote: David I. Emery wrote: I have emailed my brother in law who is a rear admiral (I think now called a vice admiral) and currently CFO of the USCG (and as a note re your alma mater a MIT Sloan grad) and rather loudly said so myself. He most likely was part of the group that made the decision... I intend to ask him why they did it when I next see him. David, I see three possibilities: a) modernization (E-LORAN), b) maintain existing service and capabilities, c) shut it down. It would be helpful to know if USCG supports the plan to shut the system down. If USCG does not, those of us who are US citizens can lobby Congress to restore funding for the service. There's an educational piece here to do. -ch ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
There is a difference between falling off a cliff and being pushed. -John == Indeed the uscg did agree to shut it down. They signed off on it. On Sat, Nov 14, 2009 at 3:40 PM, Christopher Hoover c...@murgatroid.comwrote: David I. Emery wrote: I have emailed my brother in law who is a rear admiral (I think now called a vice admiral) and currently CFO of the USCG (and as a note re your alma mater a MIT Sloan grad) and rather loudly said so myself. He most likely was part of the group that made the decision... I intend to ask him why they did it when I next see him. David, ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
I've read and heard from this forum as well as a number of other sources that GPS can be easily jammed. What makes GPS so vulnerable? How can it be jammed? -- David masondg44 at comcast dot net From: Francesco Ledda frle...@verizon.net Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: time-nuts@febo.com time-nuts@febo.com Message-ID: e3e7bc70-4087-4e64-a713-61e8524b5...@verizon.net Content-Type: text/plain; charset=us-ascii; format=flowed; delsp=yes AOPA is pushing congress to repristinate funding for LORAN. General aviation is probably the heaviest user on this Nav system. The aviation user community would love to see Nav systems with integrated LORAN and GPS capabilty, but the industry has done little in this area, due to lack of government commitment to LORAN. The FAA knows the GPS can be easily jammed, but has done nothing do push LORAN as the GPS backup system. Sent from my iPhone ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
On 11/14/09 3:28 PM, J. Forster j...@quik.com wrote: Somehow, I think they will keep GPS running whatever the cost. There is a huge civilian constituency (everybody who cannot or is too lazy to read a map) and relies on GPS to guide their Lexus to the nearest Starbucks. Also, the military needs it to guide and target munitions. The initial Afgahnistan victories over the Taliban would have been impossible without GPS and the Special Forces teams. The folly of the decision will likely not become apparent until there is a major tragedy of some kind. Frankly, I doubt that $190 M would buy a single GPS bird and launch today. I'll bet $190M would buy the bird and launch. The typical LEO science satellite runs about $50M to put into orbit (i.e. Deliver ready to integrate satellite to whereever, and $50M later, it's in orbit). The MEO orbit for GPS might be a bit more expensive, but not hugely. Launching several hundred kilos to Mars or the Moon runs about $100M. If you're building multiple satellites that are truly identical, then a recurring cost of $50M each is totally believable. Again, for context, the typical small earth orbiting science satellite typically has a total project budget (exclusive of launch) of around $100M, and that's to do multiple instruments, get the bus, integrate, etc.. A larger Discovery class (e.g. Messenger, Dawn, Deep Impact, Genesis, Kepler) mission would be in the $350-400M range. New Frontiers class (New Horizons to Pluto, Juno to Jupiter) are in the $750M range (650 for spacecraft, 100 for launch), Flagship are the multi-billion dollar (e.g. Cassini) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Signal strength. LORAN transmitters put out multi-hundred KW to MegaWatt class pulses. Wiki has a list. I would think a GPS bird puts out less than 100 Watts CW. Also, GPS birds are a LOT farther away, especially measured in wavelengths (much higher path loss) Those factors combine to make a huge difference in received power. It could well be over 100 dB. From what I've heard a GPS jammer smaller than a deck of playing cards can easily wipe out GPS w/in a mile or more for a week or longer. -John I've read and heard from this forum as well as a number of other sources that GPS can be easily jammed. What makes GPS so vulnerable? How can it be jammed? -- David masondg44 at comcast dot net From: Francesco Ledda frle...@verizon.net Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) To: Discussion of precise time and frequency measurement time-nuts@febo.com Cc: time-nuts@febo.com time-nuts@febo.com Message-ID: e3e7bc70-4087-4e64-a713-61e8524b5...@verizon.net Content-Type: text/plain; charset=us-ascii; format=flowed; delsp=yes AOPA is pushing congress to repristinate funding for LORAN. General aviation is probably the heaviest user on this Nav system. The aviation user community would love to see Nav systems with integrated LORAN and GPS capabilty, but the industry has done little in this area, due to lack of government commitment to LORAN. The FAA knows the GPS can be easily jammed, but has done nothing do push LORAN as the GPS backup system. Sent from my iPhone ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
I've read and heard from this forum as well as a number of other sources that GPS can be easily jammed. What makes GPS so vulnerable? How can it be jammed? The signal is very very very weak. The question is not how can it be jammed, but rather how can you find the signal at all. There was a recent message here reporting on the 5th harmonic of a small 315 MHz radio link wiping out GPS for a 1/2 mile: http://www.mail-archive.com/time-nuts@febo.com/msg22033.html Here is a good story: Unjamming a Coast Harbor James R. Clynch, Andrew A. Parker, George Badger, Wilbur R. Vincent, Paul McGill, Richard W. Adler GPS World, Jan 1, 2003 http://www.gpsworld.com/gps/system-challenge/the-hunt-rfi-776 -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
LORAN is a good back up, but it has problems and limitations. Navigating next to a storm can overwhelm the receiver and make it unusable. The LORAN system doesn't have a build in accuracy degradation system like GPS(RAIM - receiver autonomous integrity monitoring), and this make LORAN unfit to fly Non-Vertical Guidance approaches. GPS with its accurate positioning, fast update rate and WAAS make is an awesome aircraft navigation system that can replace almost all NAVAIDS including ILS. Today with GPS, we can fly in instrument conditions from take off to landing without ever tuning any external NAVAID; not even INS can't do that. It is pretty amazing to me! -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of Hal Murray Sent: Saturday, November 14, 2009 7:13 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) I've read and heard from this forum as well as a number of other sources that GPS can be easily jammed. What makes GPS so vulnerable? How can it be jammed? The signal is very very very weak. The question is not how can it be jammed, but rather how can you find the signal at all. There was a recent message here reporting on the 5th harmonic of a small 315 MHz radio link wiping out GPS for a 1/2 mile: http://www.mail-archive.com/time-nuts@febo.com/msg22033.html Here is a good story: Unjamming a Coast Harbor James R. Clynch, Andrew A. Parker, George Badger, Wilbur R. Vincent, Paul McGill, Richard W. Adler GPS World, Jan 1, 2003 http://www.gpsworld.com/gps/system-challenge/the-hunt-rfi-776 -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
I have been a private pilot for 40+ years, hold an Airline Transport Pilot rating and am very interested in 'redundancy'. I very much like the availability of GPS, LORAN, VOR, ADF, and ILS but have never been able to afford INS. However, I recognize the we (the USA) have limited resources (national debt in excess of $8T) and we must stop spending on something. If it were up to me, I would stop spending on other things. However, I, for one, am glad that they decided to stop spending on something. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Francesco Ledda Sent: Saturday, November 14, 2009 9:22 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) LORAN is a good back up, but it has problems and limitations. Navigating next to a storm can overwhelm the receiver and make it unusable. The LORAN system doesn't have a build in accuracy degradation system like GPS(RAIM - receiver autonomous integrity monitoring), and this make LORAN unfit to fly Non-Vertical Guidance approaches. GPS with its accurate positioning, fast update rate and WAAS make is an awesome aircraft navigation system that can replace almost all NAVAIDS including ILS. Today with GPS, we can fly in instrument conditions from take off to landing without ever tuning any external NAVAID; not even INS can't do that. It is pretty amazing to me! -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of Hal Murray Sent: Saturday, November 14, 2009 7:13 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) I've read and heard from this forum as well as a number of other sources that GPS can be easily jammed. What makes GPS so vulnerable? How can it be jammed? The signal is very very very weak. The question is not how can it be jammed, but rather how can you find the signal at all. There was a recent message here reporting on the 5th harmonic of a small 315 MHz radio link wiping out GPS for a 1/2 mile: http://www.mail-archive.com/time-nuts@febo.com/msg22033.html Here is a good story: Unjamming a Coast Harbor James R. Clynch, Andrew A. Parker, George Badger, Wilbur R. Vincent, Paul McGill, Richard W. Adler GPS World, Jan 1, 2003 http://www.gpsworld.com/gps/system-challenge/the-hunt-rfi-776 -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
And all the GPS goodness can easily be disabled by a missile and a near nuclear burst or a portable handheld jammer at the airport. The portable handheld jammer is a very real threat to GPS due to the signal levels from the satellite. Now they are trying to revive a miswired SVN and add it to the network. It is very hard to jam the LORAN signal without a high power jammer. If a LORAN station is taken out by enemy action, it is not unreasonable to rebuild or replace it. GPS is just too fragile to be heavily relied on. I know that we do it every day, but, you need to have a backup navigation system. LORAN is time proven to be functional and the technology is in place on a number of platforms to utilize it. 73 Glenn WB4UIV ETCS(SS) USN Retired (Electronic Navigation) At 10:21 PM 11/14/2009, Francesco Ledda wrote: LORAN is a good back up, but it has problems and limitations. Navigating next to a storm can overwhelm the receiver and make it unusable. The LORAN system doesn't have a build in accuracy degradation system like GPS(RAIM - receiver autonomous integrity monitoring), and this make LORAN unfit to fly Non-Vertical Guidance approaches. GPS with its accurate positioning, fast update rate and WAAS make is an awesome aircraft navigation system that can replace almost all NAVAIDS including ILS. Today with GPS, we can fly in instrument conditions from take off to landing without ever tuning any external NAVAID; not even INS can't do that. It is pretty amazing to me! -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of Hal Murray Sent: Saturday, November 14, 2009 7:13 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) I've read and heard from this forum as well as a number of other sources that GPS can be easily jammed. What makes GPS so vulnerable? How can it be jammed? The signal is very very very weak. The question is not how can it be jammed, but rather how can you find the signal at all. There was a recent message here reporting on the 5th harmonic of a small 315 MHz radio link wiping out GPS for a 1/2 mile: http://www.mail-archive.com/time-nuts@febo.com/msg22033.html Here is a good story: Unjamming a Coast Harbor James R. Clynch, Andrew A. Parker, George Badger, Wilbur R. Vincent, Paul McGill, Richard W. Adler GPS World, Jan 1, 2003 http://www.gpsworld.com/gps/system-challenge/the-hunt-rfi-776 -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
Agreed. Furthermore, a GPS jammer is VERY hard to locate because the signal levels are so low. An effective LORAN jammer could easily be DF'd with a foot sized loop and tuning capacitor resonating at 100KHz, diode detector, and a set of headphones. It would be IMPOSSIBLE to hide. If a LORAN transmitter were destroyed by a terrorist team, a backup could be in operation in hours. A damaged GPS system could easily take many months or even years to fix. -John And all the GPS goodness can easily be disabled by a missile and a near nuclear burst or a portable handheld jammer at the airport. The portable handheld jammer is a very real threat to GPS due to the signal levels from the satellite. Now they are trying to revive a miswired SVN and add it to the network. It is very hard to jam the LORAN signal without a high power jammer. If a LORAN station is taken out by enemy action, it is not unreasonable to rebuild or replace it. GPS is just too fragile to be heavily relied on. I know that we do it every day, but, you need to have a backup navigation system. LORAN is time proven to be functional and the technology is in place on a number of platforms to utilize it. 73 Glenn WB4UIV ETCS(SS) USN Retired (Electronic Navigation) At 10:21 PM 11/14/2009, Francesco Ledda wrote: LORAN is a good back up, but it has problems and limitations. Navigating next to a storm can overwhelm the receiver and make it unusable. The LORAN system doesn't have a build in accuracy degradation system like GPS(RAIM - receiver autonomous integrity monitoring), and this make LORAN unfit to fly Non-Vertical Guidance approaches. GPS with its accurate positioning, fast update rate and WAAS make is an awesome aircraft navigation system that can replace almost all NAVAIDS including ILS. Today with GPS, we can fly in instrument conditions from take off to landing without ever tuning any external NAVAID; not even INS can't do that. It is pretty amazing to me! -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of Hal Murray Sent: Saturday, November 14, 2009 7:13 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy) I've read and heard from this forum as well as a number of other sources that GPS can be easily jammed. What makes GPS so vulnerable? How can it be jammed? The signal is very very very weak. The question is not how can it be jammed, but rather how can you find the signal at all. There was a recent message here reporting on the 5th harmonic of a small 315 MHz radio link wiping out GPS for a 1/2 mile: http://www.mail-archive.com/time-nuts@febo.com/msg22033.html Here is a good story: Unjamming a Coast Harbor James R. Clynch, Andrew A. Parker, George Badger, Wilbur R. Vincent, Paul McGill, Richard W. Adler GPS World, Jan 1, 2003 http://www.gpsworld.com/gps/system-challenge/the-hunt-rfi-776 -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ E-mail message checked by Spyware Doctor (6.0.0.386) Database version: 5.13700 http://www.pctools.com/en/spyware-doctor-antivirus/ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
John, If a LORAN transmitter were destroyed by a terrorist team, a backup could be in operation in hours. A damaged GPS system could easily take many months or even years to fix. -John A LORAN site, with a several hundred meter high mast, a small house full of transmitter, signal generation and Cs clock(s?)... on a remote Norwegian island... would not be back online within a few hours after an attack. GPS is supposed to work without _any_ terrestrial support for days or weeks. I doubt that anyone can get something lethal for the SVs up in orbit without making it very obvious who they are. GPS now has lots of hot spare birds in orbit, that a instantly online with one or a few satellites going bust. That said, I think LORAN should be kept running as a backup, also with a firm commitment that it WILL KEEP running for 10+ years, giving vendors a reason to develop modern receivers. -- Björn ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.