[s-cars] ?? for List Physicists

[Kirby Smith]

Without making any statement about whether a particular device is great
or a scam, let me answer the question posed.  To look slower than the
actual case, the deceptive return pulses have to be delayed from the
real pulse returns.  Further, the laser gun has to work on last pulse
logic or else the real return will be preferred.  It is not difficult to
generate repeater pulses with a calculated time delay using laser
diodes.  Keep in mind that at 20 m/s, the rate of decreasing pulse
return times is about 60 ns per second.  The device need only delay by a
fraction of that to make the host vehicle look slower.  If such fast
triggering were difficult (and the laser gun wasn't running
pseudo-random pulsing), the device could pick up two pulses and
calculate when to next respond.  Ideally, if the device knew one's
speed, and the speed limit, it could make the vehicle look like it was
going whatever speed one wanted relative to the speed limit.  This would
be more difficult if the laser ping were from another moving car.

The above applies to ladar operated as a ranging device, and not to
coherent ladar operating from doppler directly.

kirby


jeff posto wrote:
>
> --
> [ Picked text/plain from multipart/alternative ]
> Bill,
>
> On the right side of my brain (artistic) I want to believe that review.. But the left side of my logical mind does not. I think we need a guinea pig to test it in real life. and a cash pool to bet on it, proceeds to pay for the unit.
>
> I mean, you read that review and it's really convincing, including the final 'road test'.
>
> I find it hard to believe the Lidatek device can synchornize to an incoming laser pulse accurately and reliably enough to be dependable.
> They don't talk about how many Lidatek misses were encountered.
>
> It has to retransmit a pulse that is distance varied to fool the Laser speed gun. This is a classic signals and systems problem where you have two systems operating at differing 'clock' frequencies and you must synchronize them first  in order to exchange data.
>
> Serial Digital audio, digital video, DBS satellite all have to solve this problem. This solution is well known and the electronics take time to converge on an accurate and repeatable level of stability. If the signal is lost, retransmission usually recovers the synch.
> Commonly done with the phase locked loop. Many versions analog and digital preside.
>
> In these systems, the fault mode is the data is not received in one direction.   In entertainment systems, you get noise or a blank picture.
> In Laser detection systems you get a ticket.
>
> Translation: What's the error rate?
>
> If the Lidatek does not receive AND synch on the incoming laser from the transmitter, then no return pulse is generated. At that same time, if the Laser gun actually does receive it's return pulse, you're tagged, ticketed.
>
> Sure when it works, I don't doubt the display of the Laser is unclear and the officer retransmits. But that's not enough to convince me to drop $400 clams.
> Jeff Posto
>
> Bruce Mendel <brucem105 at comcast.net> wrote:
> There's only two that work, in my humble opinion:
>
> 1. Blinder MT-10 (80% or so effective)
>
> 2. Escort ZR3 (90%+ effective)
>
> I have tested the ZR3 with a friend that's a trooper in NJ, and it works.
> The only thing is, they make the laser unit go nuts and can show it's being
> jammed, so you have to haul the speed down, then turn it off so when the get
> shot by the laser again, they get a speed reading.
>
> Bruce
> ----- Original Message -----
> From: "Bill Mahoney"
> To: "'s-car-list'"
> Sent: Thursday, May 15, 2003 10:58 AM
> Subject: [s-cars] ?? for List Physicists
>
> > Yet again, I am too ignorant to figure out if this is just marketing
> > hype or may actually work?
> > http://www.audiworld.com/news/03/lidatek/
> > This pertains to a $350 / $450 supposed lidar jammer.
> > http://www.lidatek.com/
> >
> > I do know that tickets are mostly being in the wrong place at the wrong
> > time, but spending $400 to $900 is easily saved in time and one year's
> > insurance premiums.
> > The Secretary of State has recently sent me a 4 year safe drivers award
> > (which I have displayed next to my track picture:) and I'd like to keep
> > that going ..yes.
> > Cheers'
> > Bill m -Rainman "excellent driver;)"
> >
> >
> >
> >
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>
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