Xref: utzoo sci.physics:4553 sci.electronics:3954 rec.autos.tech:4693 Path: utzoo!attcan!uunet!convex!killer!ames!mailrus!tut.cis.ohio-state.edu!rutgers!mcnc!rti!sunpix!matthew From: matthew@sunpix.UUCP ( Sun NCAA) Newsgroups: sci.physics,sci.electronics,rec.autos.tech Subject: Re: Can 31 party balloons aggravate 1 police RADAR? Message-ID: <247@greens.UUCP> Date: 30 Sep 88 15:04:55 GMT References: <880928.0208.11468@ontmoh.UUCP> Distribution: na Organization: Sun Microsystems, Research Triangle Park, NC Lines: 211 In article <880928.0208.11468@ontmoh.UUCP>, peter@ontmoh.UUCP (Peter Renzland) writes: > > While driving an 11 year old Mazda GLC filled with 31 balloons and a > passenger, I was stopped for speeding -- 88 km/h in a 60 km/h zone. > > I had just turned onto the road from a side street, and had only gone > a few hundred metres before being stopped. > > The 31 balloons were filled with helium and had "metallic" colours. > > > Are "metallic" colours on balloons really metallic? My wife works for a balloon shop, I can say a definate Yes! > Might speed-detect radar respond to such balloons? Yes, they are also good for shorting out high tesion power lines. I sat in near pitch black due to one of those balloons shorting out the stadium lights at a local footgame, besides check out the following: ->2. if item 1 fails to stop the ticket, be ready to show how the cop can ->introduce errors. Remember ANY amplitude modulation of the radar signal ->will be displayed. You want to have the gun and the cop car at the court ->house. One of the most common sources of errors is allowing the gun to ->read the heater fan in the car! The fan makes a nice chopper which will ->modulate the microwave beam. To show this, simply have the gun in the car, ->behind the dashboard and kinda aim it down toward the defrost vents. You may ->have to wave it around a bit to find the fan (which should be on max hi). ->Most fans will generate a speed of between 40 and 70 mph. In addition to ->generating a speed indication of it's own, the fan can interefere with or ->mix with the reflection of the car. If this can be happening with the heater fan, why can't it be happening with metallic balloons? Here's the entire text of a previous message. Hope it proves useful. Newsgroups: sci.electronics,sci.misc Subject: Re: Radar In article <12462@duke.cs.duke.edu> gazit@bein.UUCP (Hillel Gazit) writes: > >I was caught by a police radar which claimed that I was going 65 MPH. >My speed was 55 MPH. I think that something was wrong with the radar, >so I want to challenge the policeman in court. > >Can someone please post a list of things that can wrong with a radar? >(I want to ask the policeman if he is absolutly sure that his radar >was OK, and then ask him to >explain to me why cannot all the things on the list happen). > >Hillel gazit@cs.duke.edu Aha, you lucky soul.. living in North Carolina, where the state Gestapo writes at 56 :-). first comment.. kill the remark to the iranian airline.. you don't want to piss off a judge that might take offense to the remark.. besides it's not really germane to the discussion. Last time I had the misfortune to be in NC, the gestapo was using mostly Kustom Signals MR-7's or KH-11 units. I happen to have an MR-7 and so am familiar with it's operation and problems. (bought it just so i could know my enemy.) I'll state flatly - every radar ticket can be beaten - if you put forth the effort. You have to decide if the effort is worth it. If you have some points and your insurance is in the 5 figure range, then maybe it is. First some theory. The radar works by measuring the doppler shift, eg, the change in frequency of an RF beam caused by motion. This motion must be normal to the radar. They cannot measure speed perpendicular to the beam. The gun contains an rf generator that transmits a microwave beam out the horn. A portion of this signal is diverted to the receiver. Reflections from all objects (cars, trees, atmospheric inversions, etc) are collected by the horn and applied to the receiver. The receiver mixes the 2 signals and outputs the difference. With no motion, the difference is 0, of course. With increasing speed, an increasing audio beat frequency is produced. The readout unit counts the frequency of this audio signal, scales it and displays it as a speed. The first important thing to note is that the signal is an audio tone. There are many ways for an audio tone to become superimposed on the signal other than from speed. ANY tone withing the expected bandwidth will be displayed as the equivilent speed. The second thing to note is that the receiver, since it responds to amplitude signals, will "capture" and display the strongest signal. This may very well be your car or it could be the semi truck a half mile back or even the heater blower in the cop car. Following are some techniques I've used. 1. First, process them to death. Supoena (sp) the radar unit, the ticket book, his calibration log, his radio log, the service record on the radar unit, the FCC license of the radar gun, his patrol car, and the tickets he's issued over the last 6 months or so. Here's why. The radar gun must be licensed by the FCC. IT's call letters must be attached to the transmitter. A log of operations must be kept. No highway patrol I've ever encountered has ever conformed to these rules. You can attack his ability to properly operate the unit by showing his non-conformance to the rules. Radar units are known to be unstable. All units are shipped with tuning forks that are designed to display a known frequency. Most states require that a calibration be performed immediately before and after the stop. The only way to prove that is to show a log. No cop I've ever seen maintains a log. This is easy shooting. You also want to look at the service history of the unit. If it's been in the shop often, the it may have been mal- functioning when he stopped you. If it has NOT been in the shop, then question the maintenance practices and calibration. (nifty logic, eh?). You will want to review his ticket book to look at his pattern. If all his tickets are written for about the same speed, you can raise the possiblility of a systematic error in his gun or his use of the gun. If he writes them close together, you can maintain that he did not have time to calibrate adn log the unit between stops. you will want to have the car available to demonstrate other sources of error to be listed. As a practical matter, many tickets end here. The state does not want to take a revenue producing car and radar out of service and the cop probably does not want to use an off-day in court. 2. if item 1 fails to stop the ticket, be ready to show how the cop can introduce errors. Remember ANY amplitude modulation of the radar signal will be displayed. You want to have the gun and the cop car at the court house. One of the most common sources of errors is allowing the gun to read the heater fan in the car! The fan makes a nice chopper which will modulate the microwave beam. To show this, simply have the gun in the car, behind the dashboard and kinda aim it down toward the defrost vents. You may have to wave it around a bit to find the fan (which should be on max hi). Most fans will generate a speed of between 40 and 70 mph. In addition to generating a speed indication of it's own, the fan can interefere with or mix with the reflection of the car. Another source of intereference is the car's alternator. the ripple of the alternator can be detected by the gun. In one of my cars, I have to run the radar from a separate battery because of the intereference. 3. Propose that the signal that the cop read was not from your car and instead came from a vehicle behind you. Typically a semi truck. I have a video tape I made of some real life situations where the radar gun picked up a truck a half mile away while ignoring a compact car fairly close in. (don't ask for the tape, lord knows where it is). I'd suggest arranging a demo or a tape of this phenomena. You should have a real good "memory" of trucks behind you. I'll guarantee that the cop will not remember this detail. He's so intent on nabbing that "damn speeder" that he gets tunnel vision while concentrating on the pursuit. 4. If it was raining or inclement or foggy, then attack that as an important source of error. Most states prohibit use of radar in inclement weather because of intereference from lightning, rain drops, hail, etc. 5. Ask if the cop operated his radio while clocking traffic. he probably cannot remember or will say he did not. Be prepared for this. Ask him about his reporting procedures when beginning pursuit and when stopping a vehicle. ALL departments require thier officers to make a radio report when doing either of the above. ANY radio will cause intereference with the radar. I can generate all manner of speed indications with my amateur radio handi-talkie. Most police radios run much more power than my amateur radios. 6. Ask about any emergency equipment such as flashing lights or sirens in use during clocking. all contain motors or high power electronics which cause intereference. 7. Have the cop demonstrate the electronic calibration feature of the readout. This is different from the tuning fork calibration. This function, normally invoked by a CAL switch on the unit, verifies the readout operation by making the unit display a speed of 64 mph. This "speed" can be locked in just like a real reading. It is suspiciously close to 65 mph, especially considering all digital circuits' +-1 count inherent uncertanty. I acutally had a cop try this ploy on me once. It pissed him off that I had a radar detector so he fabricated a 64 mph speed and pulled me over. Most all radar guns have a little indicator on the display which shows that the "reading" came from the CAL function. When I pointed this indicator out to the cop, he got real hostile real fast ... but he let me go, hi. This defense is very effective but must be approached with caution. You do not want to piss the cop-sympathetic judge off by calling the cop an out-and-out liar. you want to kinda skirt the issue and imply the course of action. The above should give you a good selection of options. the key here is wear the bastards down and create a reasonable level of doubt in the judge's mind as to your guilt. You should also 1) get a copy of "the Ticket book" available from most book stores and 2) contact Cincinatti Microwave, makers of the Escourt radar detector. They have a number of handy legal defence aids. "The Ticked Book" was written by a former cop and is designed to teach you how to beat tickets. For future use, I'd suggest a good radar detector (Escort) and some practice at evasive manuveurs. Radar guns are very cheap on the surplus market (<100 bux). It's amazing what you can do with a little practice. In the last 10 years, I've only been stopped 2 times and beat both. I consist- ently drive 80+ on the interstates. IT's all in paying attention to the warning indications and in technique. Radar CAN be beat. Now if some kind soul would send me a LAWS rocket for use against the helicopters..... John De Armond gatech!stiatl!john -- Matthew Lee Stier (919) 469-8300| Sun Microsystems --- RTP, NC 27560| "Wisconsin Escapee" uucp: {sun, rti}!sunpix!matthew |