All You Need To Know About How Radar Detector Works

A lot of people use radar detectors pretty much on a daily basis, but probably not even half of them know how that device works. 

Please do note that this article merely aims to provide a full explanation while limiting the use of overly complicated terminologies. It is not intended to justify the use of a radar detector.

However, if you are only interested in knowing all the science-related things going on behind the curtain, you are in the right place, my friends. Read more important articles here

What’s going on behind the curtain

How does radar work? 

To understand how a radar detector, well, detects a radar, we need to understand what radars do and how they work firstly. 

A radar can determine the speed of which an object is moving by measuring how long it takes a wave to come back. Wait. What?

Alright, here is how it works.

A radar sends out radio waves, and these waves would hit a moving object and return to the radar. The radar will then calculate the distance between the car and the radar by how long it takes the returned wave to get back to the radar. 

So, how does it measure speed then?

To understand how radar measures the speed of a moving object, we should now talk about the Doppler Shift phenomenon. The phenomenon describes that sound has different waves ( basically called sound waves).

Doppler shift

So, if two objects are standing still, you will hear the sound emitted from that object in a normal rhythm, which is the same frequency. 

However, if the sound-emitting object is moving toward you, you will hear the sound in a more successive manner. The reason is that each sound wave now takes less than to reach you since the sound emitting object is moving toward you. 

The same goes for radio waves sent out from a radar. When both the object and the radar are stationary, the returned radio waves would have the same frequency with the sent out radio waves. 

If the object moves, the returned radio waves would now have a different frequency to the sent out waves. Have I lost you again? In case I have, here is what different frequency means. 

Imagine touching a perfectly still lake. A ring will form and sent out on the surface of the water, and another ring will follow right after. 

These rings are sent out at a constant speed. So, if the first ring takes 5 seconds to touch a nearby rock, then it should be the same for the second ring. 

Now, there is a leaf on that very lake. But as you know, a leaf is extremely light, and even a wave of water can push it. So, the first ring reaches the leaf in 5 seconds and pushes the leaf forward. As the leaf is moving away from, the second ring takes 5.5 seconds to reach the leaf. 

We now know the leaf is moving away because we are standing still, but the second wave now takes longer to reach the leaf. The opposite occurs if the ring is moving toward you. 

Radio waves work the same way

A radar pretty much works the same way to you touching a spot on the lake and sending out those rings. The difference is that a radar is designed to measure and tell exactly how fast each wave frequency travels. That is something the human senses cannot pick up. 

In short, a radar can tell how fast your car is moving depending on how long it takes the returned waves to reach the radar. Your cars moving forward or toward the radar would not affect the measurement because the radar can tell from the changing in frequency as explained above. 

How does a radar detector work?

A radar detector can pick up the radio waves from the radar. But a radar might not be the only thing that is emitting radio waves. So, how does a detector tell?

Most radar shoots out a variety of radio waves under different frequencies, but they usually only track one moving target. Those radars used by the police will specifically track only car. 

The most traditional and simplest radar detectors can tell the differences and alert you about it. The detection range depends on each detector build.

Nowadays, high-end radar detectors do not only detect radio waves from a radar, but also send out radio waves that can interfere with the radar. 

One thing I do want to mention is that police radars are not that easy to detect. So, don’t expect to get the cheapest radar detector and it will work just fine. 

Police radars these days send out radio waves of a much smaller wavelength, which is harder to detect. The most primitive radar detectors can still detect, but they have to at a close range with each other.

I am talking about like just one or two meters sort of close range. Yes, you guessed it. What good does it do if you guys are that closed? Well, as I said, this article is only here to explain how a radar detector works. So, I am not going to touch on tips and tricks that fool the police speed radar (nor do I think I should).

Bottom line

That’s it, folks, that’s pretty much how a radar detector works. You might have noticed that I explained a little bit too much on how a radar works instead of the detector itself. 

But that’s because they are mainly related to the radio waves, so it is difficult to explain one without the other entirely. Also, I realized I did say it was a full explanation, but there are still many aspects not mentioned yet. 

If you are also interested to know more about related topics, please leave it in the comment section below. I will see what I can do to answer your questions. 

Justin Taylor