Text 16191, 133 rader
Skriven 2005-11-14 16:42:00 av Michiel van der Vlist (2:280/5555)
  Kommentar till text 15925 av Raymond Yates (1:3613/48)
Ärende: looters in NO
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 MvdV>>>> But the reflected signal will be 20 to 40 dB weaker than the
 MvdV>>>> direct signal. That means you have to get a lot closer to
 MvdV>>>> detect it.

 >>> That'd depend on the sensitivity of the detectors front end.

 MV>> No, it doesn't. The difference in signal level depends on a lot of
 MV>> things, but the sensitivity of the receiver is NOT one of them.

 > I almost hate to get into the middle of this, but I will,
 > anyways. <g>

Don't say you haven't been warned... ;-)

 > North Carolina is one of those states that allows the use of
 > radar detectors.

 > I've used them for years. At one point I had two differet
 > models in my car for comparison purposes. I found I could pick
 > up the side and rear lobes very well, at different ranges with
 > either unit, well before entering the detection zone.

That makes me wonder how you know ehere the detection zone starts. If you can
pick uo the signal reflecting from objects, why can the reciever in the speed
trap not pick uo that same signal end use it for measurement?

 > The difference was in the front end recievers, which is
 > what Roy was trying to explain.

Roy was just trying to contradict me. You know Roy...

 > In the case of encountering the front lobe, one unit was signifcantly
 > better than the other, having nearly twice the range.

All very weel, buy the *difference* between direct and reflect3d signal would
still be 2- tp 40 dB. With both receivers. Althouf the better receiver would
detect the trap form a greater disctance, you would still have to come a lot
closer when detecting if from the back then when detecting it from the front
when one is in the main beam.

 > True, the signal level reamins constant, but the ability of
 > the reciever to detect that signal is critical. That /is/
 > a function of the electronics, obviously.

Obviously.

 > After I was done with the comparison, I placed the weaker of
 > the two recievers facing towards the rear of the vehicle. I
 > figured that if the police can mount two transmitters one
 > facing forward and one facing rearward, the least I can
 > do is set recievers to match. <g>

Ah, yes. That would be usefull when speeding in reverse... ;-)

 > Oh. I could pick up radar transmitters on stores, up to a
 > half-mile away..

That is pretty good. Much better than I expected. I wonder why they need such
strong transmitters for a door opener.

Over here radar is not used for door openers btw. All these detectors are
passive infrared.

 > In my area, I have a four-lane highway I travel six times a
 > week at minimum. It's the only road to town, there is no choice.
 > The posted speed limit is 55mph (88kph_). Nearly everyone without
 > exception travels faster than that, usually 65mph (104 kph) to
 > 70mph (112 kph) at all times, day or night. Now were I to travel
 > at teh posted speed limit I would be impeding  traffic in the
 > practical sense.

We had similar situations with the 100 kph general speed limit some 15, 20
years ago. Few observed it and it wasn't enforced.

Then they raised the general speed limit to 120 kph and said that *this* limit
would be enforced. And they did. aqnd it worked. Speeding is much kess seen
that it was 15 years ago. Most people now observe speed limits here.

 >>> Wanna bet? I've seen youngsters jump from lane to lane, cutting
 >>> people off and causing accidents behind them in traffic jams.

 MV>> Not possible in the traffic jams they have here. In such a jams
 MV>> cars are bumper to bumper at walking speed or are at a complete
 MV>> stop. One can not "jump form lne to lane", there is simply no
 MV>> room to go anywhere but go with the flow.

 > Roy's describing the other type of traffic jam, the one at speed.

In that case we do not call it a traffic jam, that's just heavy traffic.

 > I have been in traffic at speed in the morning rush hour where
 > everyone is traveling 70mph (112kph) excpt for a few idiots
 > that jump from lane to lane in the attempt to go faster than
 > the average. Tha's what roy is describing, the "at speed" traffic
 > jam. I don't know if you have ever experienced this or not,

Sure, what you describe is more or less the normal situation during the rush
hour on the motorways here.

 > but ti's different from the stopped traffic jam which we call
 > "gridlock", whether it's in a city or not(the precise term gridlock
 > referes to traffic in cities where the cross streets are also
 > full of stopped traffic, but the term is used to generically
 > describe any traffic that is immobile).

Such a situation often occurs here. Not just in the cities, but also on the
motorways. often because of an accident. Or a situation where to roads come
together. In the latter case, traffic will still be moving, but ever so often
it slows down to a crawl.

 MvdV>>>> Plus that the methods of detection have improved to the point
 MvdV>>>> that there is no escape. The latest system is "traject
 MvdV>>>> controle". Camaras at checkpoint A record you time of passing
 MvdV>>>> and then when you pass checkpoint B five kilometres further
 MvdV>>>> down the road you are clocked again. Arrive their too early
 MvdV>>>> and you get the ticket in the mail.

 > The New York State Thruway was doing that in the 1950's, where
 > they ticket you had picled up at the entering tollbooth had
 > your starting time stamped on it. When you turned it in topay
 > your toll, the tolltaker would check the time (the computer
 > did that) and tell you what your toll was while the machine was
 > printing out your speeding ticket.

Over here they now have it perfected to the point that there is no human
involved. The camera sends its images to a computer that extracts the license
number on the plates from the pictures. The computer sends the speeding ticket.
Only when someone contests it, will a human look at the pictures.

Cheers, Michiel

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