# Tag Info

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How do radar speed signs work? To answer the question raised in the title, radar signs (and radar guns in general) measure the Doppler shift between the outgoing signal and reflected signal. This frequency shift translates directly to $\frac{dr}{dt}$, the rate of change of the distance between the acquired object and the radar. This range rate ...

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I notice the same thing on my bicycle. As I approach a certain radar sign it says I'm going 10 mph, so I start peddling faster to see how fast I can go, but by then the sign is more off to the side instead of in front of me and the readout on the sign is decreasing! The radar unit is probably measuring how fast I am approaching it, not my speed over the ...

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It's most likely that the radar gun is just locking on to a different vehicle. Depending on how it's filtering and processing the received signal, it could even be measuring the speed of a car going in the opposite direction.

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In radar, chirp (LFM - linear frequency modulation) is used to stretch the pulse so that the received energy is large enough for detection while having a large coherent bandwidth commensurate with the desired range resolution. There are two ways of detection, the so-called "stretch processing" that is just a correlation receiver using a homodyne mixer, the ...

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Under some circumstances it is possible that radar effect a permanent magnet in a sufficient way. First of course by heating. All radiation that hits the magnet and is not deflected by 100% heats the magnet. Second by the use of modulated radiation. Radar is a modulated radio wave with zillion of photons having the same direction of their electric and ...

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