Radar Detector Detectors: Everything You Need to Know

In areas where radar detectors are illegal, police commonly use radar detector detectors (RDD’s) to locate drivers who are running radar detectors. How do they work? How easily can they spot radar detector users? How effective are “undetectable” radar detectors at avoiding detection from a radar detector detector? Let’s take a look and cover everything you need to know about radar detector detectors.

Spectre Elite Radar Detector Detector

Two Most Popular Radar Detector Detectors

One of the most popular early RDD’s was the VG-2. It did a good job and can still detect many radar detectors in use today, but radar detector manufacturers made a simple change to avoid being detected by the VG-2. They simply changed the frequencies that the radar detector’s internal local oscillator used that VG-2 was also scanning for (I’ll talk about this in a little more detail in just a moment) and suddenly those new radar detectors became “undetectable” to the VG-2.

Then the Spectre was developed, and there’s been several generations of the Spectre over the years, and it basically scans all of the possible frequencies radar detector manufacturers could use within their RD’s so the Spectre is much more effective than the VG-2 ever was or could have been. However, RD manufacturers have employed even more sophisticated tricks to make themselves undetectable to even the Spectre RDD, but nevertheless the Spectre is what you’ll see in use nowadays in most places around the world and it is able to detect the vast majority of radar detectors in use today.

Here’s a quick look at the two RDD’s, plus a little information about this whole cat and mouse game:

Radar Detector Detectors In Action

Let’s take a look at RDD’s finding RD’s and what it looks like from the police officer’s end.

VG-2 finds a leaky Cobra:

Spectre Elite finds Radar Detectors:

and here’s a pair of videos with the Spectre Elite in different situations.

As you can see, RDD’s are designed to be spun around on their mount to help the officer locate where the offending RD is. The RDD’s are extremely directional so that the officer can more easily pinpoint the source of the alert when rotating the RDD left or right.

There’s also a sensitivity adjustment knob so that as the officer gets closer to the radar detector, they can still locate the radar detector and have a stronger/weaker beep instead of just having the RDD go full tilt the whole time.

Since some lower end radar detectors emit like crazy, newer RDD’s even have a special filter built in that’s designed specifically to filter out super leaky detectors as they get closer, a similar idea to using the sensitivity adjustment knob.

How Radar Detector Detectors detect Radar Detectors

What’s going on inside a radar detector detector and how does it detect radar detectors? (Wow these sentences are getting crazy, haha.)

Well radar detectors are basically radios, kind of like your car’s stereo. However, instead of looking for music on a certain radio station, they’re looking for the existence of a radio station / radar signal in the first place. Radar detectors are designed to sweep a whole range of frequencies while looking for police radar, similar to scanning for all the radio stations on your car stereo when searching for a radio station to listen to. Inside of a radar detector is a component called a local oscillator (LO) which is what’s doing the sweeping / scanning across the different frequencies. (You can read more about superheterodyne receivers if you want to go into even more technical detail about the LO.)

Now the thing is that this LO is not only detecting radar coming into the radar detector, but it is emitting radar signals back out of the radar detector as well, and these emissions are precisely what an RDD is looking for.

Note: This is part of the reason why our radar detectors need filters on Ka band. Some poorly designed radar detectors such as cheap Cobras have chosen LO frequencies that have harmonics in Ka band and can cause other nearby radar detectors to false alert on Ka band. I’ve done a whole writeup on how Ka filters like Ka Guard and RDR work to deal with this issue, but the emissions that can cause other nearby radar detectors to false alert are the same emissions that a radar detector detector is looking for.

How easy is it to detect these emissions and how far away can an RDD pick up an RD? Well it depends on the design of the RD. Let’s take a look at a few examples.

Radar Detector Detectability Rankings

There’s different classes or tiers of detectability it seems. It’s not always a black and white answer to whether or not a detector is undetectable.

#5 Extremely Detectable, over a mile away

One of the most easily detectable radar detectors I’ve tested to date is the Whistler CR93. It easily maxed out the test course I used where as soon as I crested the hill at the far end of the test course over 1,600 feet away, the Spectre Elite went off.

When the TXCTG tested the CR93 in Texas, in their long, straight, flat terrain they were able to pick up the CR93 over a mile away, lol…

#4: Detectable from hundreds of feet away

However, normal alert distances are typically measured in hundreds of feet. For example, take a look at this test with the Max360.

Example Detectable Radar Detectors:

#3: Detectable only at Close Range, Not Stealth

Some detectors are detectable at only a few feet away rather than hundreds of feet away. They will trigger a Spectre as an officer drives by. If he’s parked on the side of the road with his RDD, camping and looking for RD users, these detectors will trigger his RDD as you drive by so they are not recommended in areas where RDD immunity is a necessity.

Recommended Radar Detectors that are Detectable at Close Range

#2: Effectively Stealth, but use only for front-facing antennas

Some detectors are only detectable from a few feet away, and even then only when directly in front of the detector. Move a few feet back or drive past the detector instead of park right in front of it and the officer will get no alert in practice. A good example is the Uniden R3.

I consider these detectors to be “effectively stealth.” Sure they’re detectable, but you’ll have no issue in practice.

The only time you will see an issue is if you have two detectors, such as a remote with one antenna facing forward and a second antenna facing backwards for arrows. The front antenna won’t cause an issue, but the second rear facing antenna could be an issue if a police officer pulls up behind you at a red light and your rear facing detector will trigger his Spectre. In this situation, the radar detector isn’t completely stealth and that could be an issue in practice. However, for just a single front facing detector setup, you’ll be just fine.

Recommended Effectively Stealth Radar Detectors:

#1: Completely Stealth

Finally you’ve got your completely stealth detectors. These detectors will have NO problem being undetectable to a Spectre Elite.

While these detectors technically aren’t completely stealth and will trigger a Spectre that’s a few inches away, that’s never a situation that you’re going to encounter on the road so when you’re driving, you’ll have no problem being picked up while running a completely stealth radar detector.

Recommended Completely Stealth Radar Detectors:

Discontinued Completely Stealth Radar Detectors:

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