Radar Jamming

Yes, that is exactly how the 5.8 Ghz toll tag transponder works. However, if the RADAR gun uses a homodyne receiver, adding sidebands to the incident signal by any technique will result in a beat output that would go down the same channel as the doppler shifted incident carrier......

SSB works on paper but it requires extremely precise frequency control in a RADAR gun. However, a free running oscillator will work just fine in a RADAR gun when coupled with a homodyne receiver ( the transmitted signal beats with the return in a mixer, producing the difference frequency as an output)

I am betting that the demodulated sidebands would spoof the RADAR gun receiver.....

I haven't tried it on a Radar gun, but I did use the technique to transmit data from the "transponder" back to the "interrogator".....

Andy

Andy, So, did you every visit the California site during the installation (So. Cal, not the bridge?) If so, we probably met! I was in charge of design and installation of the toll equipment, including the FastTrak antennas!

Charlie Edmondson Engineering Unique Solutions to Unusual Problems

You can spoof the police radar by sitting behind a very large, slow moving truck. At least it seems to work, I've never been stopped for speeding when using this evasive technique.

Ken

Subject to some details being worked out, this has a lot of promise and I have been meaning to try this. Trouble is, I reckon that road trials (without a friendly and co-operative cop) are high-risk potentially-expensive activities!!!!

From a number of radar flight tests I did a few years back, it always amazed me how much return you get off a tiny little retro-reflector. So, I'd imagine that small one will give a more solid return than most autos.

The problem with mechanically modulating it would be the up and down Doppler shift as the speaker gives it a + and - component. I think the processing in the radar gun would get confused, or ignore it, or something equally unsatisfactory.

And I don't know how sensitive the radar gun would be to AM or OOK, I think it might ignore those and just deal with the FM/Doppler. If they are sensitive to AM, the easy way would be to arrange a diode across a dipole and switch it with the appropriate audio freq you want presented to the cop. And maybe if you just did modulate it with audio, the radar gun would see that sideband as the one to be processed (incorrectly of course)

Barry Lennox

On Fri, 15 Apr 2005 01:26:58 -0700, Pooh Bear wrote (in article ):

And how would you know about the "known" traps? If I've driven by them before (personal knowledge of the trap), I wouldn't need GPS.

You got a list of them?

Bah! Snow is easy to drive on. Ice, OTOH...

I tell my wife that I have a 4WD truck, so I can go anywhere. It even has the off-road package so I can go off the road.

Not personally, but ISTR that there is a site for the UK that lists them. It relies on users reporting fixed speed traps and commonly used locations for mobile ones.

Here's a small example...

Check out the explosives used on some Gatsos here...

Graham

"Andy" wrote in news: snipped-for-privacy@o13g2000cwo.googlegroups.com:

Laser speed guns work by making multiple distance/time measurements,using pulse widths of ~35ns,rep rates of ~500 hz.They fire a pulse,and clock the return to measure distance.Then calculate the distance change over time.

I got that a long time ago from an industry laser magazine;Laser World or something like that.

(So.

Andy writes:

No, not after it was installed, other than incidental trips on other projects. I did a site survey at SH121 in the early 90's to see what interferers were around, but after riding around for a day over the proposed route with a spectrum analyzer, I didn't find anything that looked like it would bother us....

Several trips to Lawrence Livermore to confer with Don Davis, and a couple others, about the system, since it was they who wrote the Title 21 spec that the legislature passed. I have some real problems with a couple of their specs (namely the field activation strength) since even NIST at Boulder Colorado could not calibrate an antenna to the accuracy required by Title 21 (went there, too, and talked to their big guns. However, as a practical matter, nobody else seemed to care that a spec was unattainable, and were mainly concerned with whether the system would acually work....

I was lead design engineer, and worked mainly in the lab, but I set up a test track for TIRIS in an abandoned race track between Dallas and Ft Worth (Richland Hills), and got a LOT of good , practical data from this. It reinforced my feelings that , no matter how smart the team is, or how much preparation they do, you don't know diddly squat about how a system works in the field till you try it out.......

Since I retired 3 yrs ago, I went back as a consultant to ETCC who bid on a new 121 project about a year ago.... I don't work there, tho, and don't know how their proposal came out.....

So, have you done any in-depth tech study of TIRIS versus AMTECH, and how did they compare ? I am familiar with the AMTECH system, and am fairly sure they can't meet the field activation specs any more than TIRIS can, but , as I said, nobody seems to care (except design engineers like me (grin) ).

TIRIS was sold to a Canadian company, SIRIT, and has a headquarters here in Dallas (Carrolton), and I went by last year to BS with the engineers there.

Even tho I had been away fromt he project for 8 yrs or so, they were

still using the same designs for the READER and the Antenna that I built in the lab ( subbed to TELENEXUS and SEAVY ENGINEERING companies).... But they told me that the lane discrimination pulses had been eliminated from the design. Why was that ?

If you care to correspond further, give me an Email at

snipped-for-privacy@juno.com , with TIRIS somewhere in the subject line, and

we can shoot bulls till sundown.

Andy Sharpe, PE, etc etc,etc

of

measurements,using

clock the

time.

World or

Andy replies:

Well then, I doubt that my blue sky idea would work for LASARs then... Oh well.

I suspect that the beam is wide enough when it meets the car to illuminate the whole front, so they will get enough return from somewhere or other.....

I still think the corner reflector is good, I just can't think of how it would be modulated to confuse the LASAR..... Probably a good thing I never claimed to be a LASAR engineer (grin)...

However, I BET that if I had a schematic, I could come up with something ( along with a dozen others who post here (grin) ) that might work, sort of ....

Thanks for your reply.....

Andy

That is the *problem* here in Australia - the state is the body operating the devices :-(

If only it had the on-road package so you wouldn't need to call a tow truck.

Here in colorado, it's become a cliche: 19 out of 20 cars that go sailing off road when it snows are 4wd. These idiots think that 4wd will hold the road better instead of just gettng them out of control faster.

like

hiking

I drove from Green Bay to Milwaukee on whatever highway that is just before Christmas - not only do you guys drive on the wrong side of the road (I can live with that), and not only at 80mph (that's cool....), but there was SNOW on the road too! Who the hell has snow on a road?? Distinctly uncivilised......

Cheers.

Ken

What was an 'energy ticket' exactly ? Preumably intended to reduce gasoline use. During the 70s 'oil crisis' we had an overall 50 mph speed limit imposed here. I still have the fuel ration tokens that were distributed in case they might need to introduce rationing.

Graham

;-)

your

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before

can

SNOW

That's odd, people weren't using trucks off the road when I went by....

Ken

But the g makes you black out and then you hit the policeman :-)

-- "Electricity is of two kinds, positive and negative. The difference is, I presume, that one comes a little more expensive, but is more durable; the other is a cheaper thing, but the moths get into it." (Stephen Leacock)

I read in sci.electronics.design that Andy wrote (in ) about 'TIRIS', on Sat, 16 Apr 2005:

This is a fundamental law of nature.

Any idea what they use as the "Laser diode"? wavelength, power? Could a simple laser diode modulated with ~35 nS pulses at around ~500Hz stuff it up? I have read somewhere that the later guns have a "jammer detector" built in the brings on a "Jamming" LED for the cop.

Barry Lennox

Barry Lennox wrote in news: snipped-for-privacy@4ax.com:

Specs I've read were 904nm.power,I dunno.The reflected power they get from their pulses will not be that great,either. I suspect a long pulse train would jam the laser guns,but again,I don't know about jam indications.You would wear out the LD if it was on continuously.It would need to be triggered by reception of a laser pulse. (like the Lidatek jammer)

I know that some states have laws that make using laser jammers "interfering with police enforcement activities" or something similar.