SLD920X radar detector/jammer - does it actually work??

Jun 24, 2005 95 Replies

Well the limit in towns is more to do with the performance of pedestrians, so 50kph / 30mph is pretty much the norm throughout the world.

On motorways it is a different matter. The UK limit was introduced in the

1960's and was based on the performance etc. of cars at the time (top speed ~75mph, cross ply tyres, drum brakes, naf steering, solid rear axle & cart spring suspension). These days almost any car can reach 100mph, has suitable radial ply tyres, disc brakes (so can stop from top speed near physical limit), rack and pinion steering and independent suspension.

Almost alone the UK has persevered unchanged. In Europe, only Denmark, Sweden and the [motorway free AFIACS] Baltic republics have a lower motorway limit.

So the poster is correct the current UK speed limits WERE introduced for a very good reason, and whilst the limit on shared roads are broadly correct the limits on segregated roads (motorways, grade separated dual carriageways etc.) could do with updating.

Of course if vehicles didn't move at all then they would be almost totally safe.

All states DON'T require a front plate... for example, Arizona.

...Jim Thompson

| James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.

Or if they were built like this:

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-- Cheers! Rich ------ "Cover your stump before you hump. Before you attack her, wrap your wacker. Don't be silly... protect your Willie. Wrap it in foil before checking her oil. If you're not going to sack it, go home and wack it. -- National Condom Week"

Fortunately AZ is an anti-government state, per the Reagan definition.

...Jim Thompson

| James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.

Then they arrest you for not having, modifying, or altering your license plate. Problem solved.

Keith

Yet. VT was going to drop the front plate (at a savings of some real $$), but the cops put the kibosh on that! Guess why? ...and how long will it take AZ to figure it out? ;-)

Keith

I've gone through quite a few of those, too.

Very odd as to why nothing ever got picked up...

Incidentally, the jammer isn't supposed to be obvious. If it's working properly, the speed gun just doesn't show a reading at all. But I would expect the police equipment to be continually upgraded, whereas motorists would be stuck with their expensive SLD920X installations for years.

It receives passively, and upon detecting a laser it jams it. You also get an audio warning (which is the bit I've never heard in several years, although the sounder does work, during the power-up tests) and then you jump on the brakes and switch the unit off fast, allowing the PC to get a valid reading.

snipped-for-privacy@somewhere.in.the.uk.com wrote on Mon, 27 Jun 2005 13:03:15 +0100:

If they point a speed gun at you, and they don't get a reading, I would call that obvious.

David Taylor

So it can start jamming the signal fast enough to prevent any return to the laser gun?

Alex Hermes: "We can\'t afford that! Especially not Zoidberg!" Zoidberg: "They took away my credit cards!" www.drzoidberg.co.uk www.ebayfaq.co.uk

"Dr Zoidberg" wrote in news: snipped-for-privacy@individual.net:

laser speed measurement is actually a number of distance measurements that are timed,and a processor calculates the speed from the change in distance over time.So,a number of laser pulses are required to make a speed measurement,and a pulse train in the range gate will confuse the processor.

Jim Yanik jyanik at kua.net

snipped-for-privacy@somewhere.in.the.uk.com wrote in news: snipped-for-privacy@4ax.com:

What does a laser speed gun do if it receives NO reflected signal? Would it consider that "jamming"?

It has to receive it's reflected pulses to make it's distance measurements,and extra pulses received will throw off the change in distance measured.

Jim Yanik jyanik at kua.net

"David Taylor" wrote in news:d9oush$lku$ snipped-for-privacy@outcold.yadt.co.uk:

if there was no reflection of the pulses,the laser speed gun cannot make it's measurements.

Is that "jamming"?

(no,it's stealthing)

Jim Yanik jyanik at kua.net

That's what I thought. Sounds like an approach which is wide open to failure.

Daytona

Jim Yanik wrote on 27 Jun 2005 14:04:09 GMT:

So, how do you stealth a car, required by law to have a reflective numberplate on the front of it?

David Taylor

Meanwhile, in uk driving groups and in the UK in general, reflective numberplates front and rear are legal requirements on all vehicles registered since 1973.

Laser SDD's very very often fail to get a reading, and if the tripod is poorly damped and/or the van is parked close to the road then an error code can be produced twice as often as a good reading.

The modern devices will only be active for about five seconds and not produce a jamming warning on the SDD, therefore the operator will just target the vehicle again and get a good reading. The theory is that the laser alarm goes off, the driver stands on the brakes and the second time the operator gets a reading. Unless the car is stoped and searched there is no proof that a jammer was in use.

Gareth

Yes, the commonly used laser speed detection devices (SDD's) send out

30-40 pulses over about a third of a second. They use least-squares on the time of flight to calculate the speed of the vehicle. The jammer would be active after the first few pulses are detected and produces signals which frustrate the detector portion of the SDD.

Gareth

Incorrect , they are not required on the front of motorcycles or motorscooters

At the standard operating distance the laser beam will have diverged quite substantially, to the point that it could be a metre wide.

The problem with detectors and jammers is that they need to be fitted properly. I went with my boss to see somebody about fitting an Origin B2. The installer's detector was fitted onto the rear view mirror and was obscured by the tint. I questioned whether this was a good idea and the reply was "well it works when I point a Nokia phone with IR enabled at it". Good test method then! As the range increases the quality of installation will have a critical effect on the detection capability. A detector and jammer *should* be fitted around the number plate area because this is the most vertical area of a car and hence it recommended for targetting. Apparently the reflectiveness of the plate only has a marginal effect.

Gareth

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