Radar technique: target Xenon headlights?

[121Traffic]

Doppler RADAR refers to the RADAR's method of functioning. These types of RADAR operate on the Doppler effect. Let's see if I can explain this without busting out all engineering-like. When Doppler RADAR (i.e. police RADAR), radar waves of a certain frequency are emitted by the source (usually mounted on the patrol car dash). Frequency is essentially how many "waves" pass through a certain point in a given amount of time. Shorter wavelengths make for higher frequencies, due to more "waves" passing through that point in the same amount of time. So let's say that our RADAR emits waves at a frequency of 5 Hertz (5 waves pass through any given point in one second.) Let's picture our radar as a batting cage ball thrower, and the balls are our radar "waves". The ball thrower pitches 5 balls a second. When pitched at a stationary walls, the balls bounce back one after another in a constant return. Now, pitch these same balls at a surface that is moving towards the machine. The balls are still pitched 5 balls a second, but since the wall is coming towards the machine, the balls are hitting the wall faster that 5 balls per second, and are consequently bouncing back closer together than when they were first launched (hence a shorter wavelength, making a higher frequency). Through a specific mathematical equation, a police radar can measure the new frequency and determine how fast the object must be moving to change the radar frequency to what is being received, as opposed to what was originally emitted.

I tried to be clear, but I think I failed, lol. Sorry, it's late, and I hae to get up early...:D

[soundwave]

Okay, this has nothing to do with headlights, but radar rather. I know there are different bands, K, X, whatever else there is. But is Doppler radar different or are they all Doppler radar? I have a radar gun for baseball simply marked as Doppler. We were messin around with it trying it on different radar detectors, and it only set off the more expensive ones. The $35 ones didnt do anything. Anyone know why?

I can answer about the Doppler. Yes, radar guns work on the principle of Doppler Shift. When the radar gun transmits the radio wave it is at a predetermined frequency and the radar gun receives the "bounce" of the radio wave as it comes back. If the vehicle is standing still it produces the same frequency as was transmitted. If the vehicle is moving, it produces what is called a phase shift or a different frequency when it comes back to the radar gun. If the vehicle is moving towards the radar gun the frequency is higher, away is lower. From what I understand, most circuits in radar guns use the absolute value (always positive number) of the returned frequency to calculate the speed. The larger the phase shift (difference) of the frequency, the faster the vehicle is moving. So, all radar guns work on the principle of the Doppler Shift.

As for why it doesn't seem to be detected by the cheaper radar detectors, all I can think of is that it searches the radar bands at a slower speed and the more expensive the detector is, the more likely the sensativity would be for producing an alert (e.g. weaker waves from a radar detector are produced as an alert as a precaution rather than ignored as being produced by something other than a radar gun). Who knows? lol Cheers. ;O)

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I know this is a little off-topic, but has anyone ever encountered someone using a radar jammer? They're actually radar detectors that transmit on all frequencies up and down the spectrum of the radar frequencies to confuse and render useless radar gun readouts.

[Seand442]

A good example of the doppler effect. Stand by a railroad crossing when a train is coming. Listen to the pitch of the horn as it comes closer to you, is right next to you and as it passes you. It is the change in pitch caused by a moving object. That is in a nutshell the doppler effect. I can't remember college that well.

On a side note, funny story passed down to me.Can't vouch for truth but a good chuckle. An officer was at an airforce base and happened to have a radar mounted in his car. he thought it would be funny to clock the f-16 taking off across the way. Long story short, the radar got fried and the officer started quite a ****storm. Turned out the f-16 jammed the radar and sent off all sorts of warnings and alarms. Note to self, don't radar military aircraft.

[bobcoop06]

I understand the concept of RADAR, it's just the bands that confuse me. And why some radar detectors work better than other. Thanks for all the replies though!

[P01IC3M4N]

I know this is a little off-topic, but has anyone ever encountered someone using a radar jammer? They're actually radar detectors that transmit on all frequencies up and down the spectrum of the radar frequencies to confuse and render useless radar gun readouts.

you poor, poor misinformed soul you. the commercial "jammers" don't. it is illegal to transmit without a license issued by the FCC.

i've never seen a car i couldn't tag.