[time-nuts] GPS Spoofing

Bob Camp lists at rtty.us
Sun Jul 28 22:44:47 UTC 2013


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" <jfor at quikus.com> 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: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 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 <tmiller at skylinenet.net> wrote:
>> 
>>> You can't use "efficient antenna" and "100 kHz" in the same sentence.
>>> Oh, wait...
>>> 
>>> 
>>> ----- Original Message ----- From: "J. Forster" <jfor at quikus.com>
>>> To: "Discussion of precise time and frequency measurement"
>>> <time-nuts at febo.com>
>>> 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" <phk at phk.freebsd.dk>
>>>> wrote:
>>>> 
>>>>> In message <DAB33AEF-98EF-4503-89A7-657F0D25AC48 at rtty.us>, 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
>>>>> phk at 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.
>>>> 
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>>>> 
>>> 
>>> 
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