Not so at all. What I described is a simple means to make a receiver see different GRIs and TDs than what it might see off the air. The system can accurately set any GRI in 1 uS increments and any one of several TDs to 1 uS also. That is hardly a jammer.
Furthermore, if the Tek DD501s were replaced by something like BNC programmable Digital Delays, you could change the received position over time. -John ============ > I've just been catching up on this thread. > > The subject says GPS Spoofing, but most of the replies seem to revolve > around jamming. Not the same thing. > > Just a thought... > > Rob > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of J. Forster > Sent: 28 July 2013 20:06 > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] GPS Spoofing > > The point about the duty cycle being low is correct. And, there are > commercial linear power amps, like the used ones made by ENI and others, > that can easily put out 1 kW plus narrow pulses. > > Furthermore, the pulse generator is trivial to make with a Rb, 3 or more > Tektronix DD501s, a simple OR gate and a gated oscillator at about 100 > kHz. > I've cobbled up that setup several times as a LORAN-A simulator. > > The main difficulty is getting a reasonable match to an efficient antenna > at > 100 kHz. > > -John > > ================= > > > >> Hi >> >> Since it's a pulse system, and you get to position your pulse for >> maximum effect, I don't see any reason to generate CW power. Simply >> mimic the lowest power slave in the chain. There's very little >> redundancy with Loran, so spoofing one station will mess it up. No >> need to mask the entire chain. At most you would need to hit two low >> power > slaves. >> >> Math wise: >> >> Wavelength is 10,000 ft / 3,000M. Throw things off by ~10% of that and >> you have problems in a harbor. You would need to play a bit to see >> weather a pulse every so often does the trick or not. Is that 20 db >> below the slave or not ? You'd have to play with it. It's in that >> range. A spoof that says they are on the other side of the world isn't >> going to work. One that says you are on the north side of the channel >> (when you are on the south side) is what would work. >> >> Power within a pulse set at a 5:1 duty cycle. For a 50,000 us GRI you >> have another 50:1. For longer GRI's you might add another 2:1. Net is >> a peak to average ratio of 250-1000 to 1. Put another way, a 500W >> pulse is ~ >> 1 average. >> >> Power at 100 KHz = what's in a fairly cheap switching power supply. >> Plug it into the wall. A couple hundred watts (or even KW) pulse is >> cheap. Say you have 120W out of the wall (or a car battery). If the >> math above is correct and you can run 80% efficiency, that's a pretty > powerful pulse. >> It's probably cheaper to generate something at 50:1 rather than the >> whole >> > 200:1. A 5KW is a *lot* of RF, even into a simple antenna. >> >> Antenna - there's a couple ways to do that. All of them are tradeoffs >> (size / cost / power). The cheap way is to use a wire that's already >> there.. Since you don't need to propagate (near field), the antenna >> efficiency could be higher than you would think for some antennas. >> >> Is it easier than that with some smarts involved in the pulse - >> probably yes. Do the smarts raise the hardware cost significantly? - >> you'd have to build a few and find out. What really drives this or >> that Loran receiver nuts? I'm quite sure you could work that out with >> one > to play with. >> >> Am I gong into the Loran-C jammer business? No, so don't contact me >> off list to buy one. The point is not *have* I built one, but could >> one be built easily. >> >> >> Bob >> >> >> On Jul 28, 2013, at 1:29 PM, "Poul-Henning Kamp" <[email protected]> >> wrote: >> >>> In message <[email protected]>, Bob Camp >>> writes: >>> >>>> I'm not talking about taking out Loran-C over the entire North >>>> Atlantic. >>>> The target is a harbor sized area. For that, you certainly do not >>>> need a 600' antenna or megawatts of power. >>> >>> No, you need about 600W (continuous) and a loop-antenna about 5m in >>> diameter. >>> >>> Do the math, It's not as easy as you think. >>> >>> -- >>> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >>> [email protected] | 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 -- [email protected] To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > > _______________________________________________ > time-nuts mailing list -- [email protected] To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
