Hi Omega was world wide, Loran was not. Anything that operated over *long* distances (tankers, airplanes) was Omega. They pulled Omega gear off of the planes and replaced it with GPS. I suspect they did the same thing on the big tankers.
Bob On Jul 28, 2013, at 6:24 PM, "J. Forster" <[email protected]> wrote: > I'm not so convinced about this: > > "OMEGA was the primary means of radio navigation, world wide, from 1976 to > 1997. ." > > There was LORAN-C, after all. > > And Omega was a CW, phase difference system, LORAN a pulse system. > > AFAIK, Omega never really made it into the uP age; LORAN certainly did. > > -John > > =========== > > > > > > >> The Helix coils are 25' high and have a 6' high relay: >> http://www.haikuvalley.com/History/OMEGA-NAVIGATION-SYSTEM/8839335_kzKJLd#!i=2042047390&k=QJbHKzM/ >> >> >> --marki >> >> >> -----Original Message----- >> From: [email protected] [mailto:[email protected]] On >> Behalf Of Bob Camp >> Sent: Monday, 29 July 2013 7:05 AM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] GPS Spoofing >> >> Hi >> >> So in this case we're talking about "horrible" to "even more horrible" in >> terms of efficiency. I'll freely grant that a 600' tower over a really >> good ground plane (like say the sea) is going to be way more efficient >> than anything I'd come up with. The same thing would apply to a matching >> network made of coils you can stand up inside compared to anything I'd >> make. >> >> Totally off topic - In the lobby of Continental Electronics they used to >> have this typical transmitter sitting there. You sort of wondered "why". >> After looking at it you figured out the little ant down in the bottom was >> a person. Yes, the coils and "stuff" in Omega transmitters were *big*. >> >> Bob >> >> On Jul 28, 2013, at 4:23 PM, Tom Miller <[email protected]> wrote: >> >>> You can't use "efficient antenna" and "100 kHz" in the same sentence. >>> Oh, wait... >>> >>> >>> ----- Original Message ----- From: "J. Forster" <[email protected]> >>> To: "Discussion of precise time and frequency measurement" >>> <[email protected]> >>> Sent: Sunday, July 28, 2013 3:06 PM >>> 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. >> >> _______________________________________________ >> 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. _______________________________________________ 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.
