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

[R. Mark Clayton]

Yes, and they were based upon the performance & safety characteristics of
contemporary cars. Modern cars can safely travel at much higher speeds,
but this has been ignored by successive governments who are fearful of
shroud-waving campaigners. The law has therefore slipped into
disrepute.

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.

 

[[email protected]]

Whilst TC's have been buying more, they are still not all that common, and
as already discussed need to be carefully aimed. Unlike a radar detector
the narrow beam needs to fall on your device and be recognised.

I have seen a few of these and fell foul of one (but the police lost the
paperwork). Look out for vans parked in lay by's etc. with a back door
open. A favourite here in Manchester is too borrow a marked van with an
orange light from the airport, park it up where the limit changes, put a
couple of cones out (as a distraction and so it looks more like road works)
and wait for the money to roll in.

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.

 

[[email protected]]

There's a basic fact I'm missing on this. Does the jammer jam all the
time, or does it wait until it detects an incoming signal and then start
jamming?

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.

 

[Dr Zoidberg]

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.

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

 

[Daytona]

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

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

Daytona

 

[David Taylor]

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.

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

 

[Jim Yanik]

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

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]

[email protected] wrote in

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.

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]

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

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

Is that "jamming"?

(no,it's stealthing)

 

[Keith Williams]

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

Is that "jamming"?

(no,it's stealthing)

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

 

[David Taylor]

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

Is that "jamming"?

(no,it's stealthing)

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

 

[Jim Thompson]

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

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

...Jim Thompson

 

[Brimstone]

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

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.

 

[Gareth A.]

[email protected] 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.

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

 

[Gareth A.]

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

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

 

[Rich The Newsgroup Wacko]

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

Or if they were built like this:

http://www.abiengr.com/~sysop/images/Safe-Car.gif

 

[steve robinson]

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.

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

 

[Keith Williams]

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

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? ;-)

 

[Gareth A.]

Radar detectors work because the radar signal is scattered off of
everything. Laser beams are very highly focused beams of light.
Unless the police point the laser at the detector, it won't
detect anything. They'll probably point it at your numberplate
to get a reading of your speed, so your detector won't notice.

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

 

[Jim Thompson]

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? ;-)

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

...Jim Thompson