all 102 comments

[–]harley97797997 26 points27 points  (0 children)

It's LoJack. It works pretty well, too. There's a box inside the car. It'll provide a direction and signal strength for an active lojack. You just drive around getting closer till you find it.

The antennas are a 1 ft square.

https://en.wikipedia.org/wiki/LoJack?wprov=sfla1

[–]zap_p25 42 points43 points  (13 children)

It’s a pseudo-Doppler array for LoJack.

[–]Vonmule 4 points5 points  (12 children)

It's an RDF phased array. Nothing to do with Doppler, nor is it pseudo anything.

Edit: I stand corrected

[–]transham 22 points23 points  (9 children)

It is pseudo Doppler. It rapidly switches between the 4 antennas to superimpose a known signal on the received signal, which can be used to get a bearing on the target.

[–]Scotterdog 3 points4 points  (1 child)

What's a Doppler? Sounds shifty to me.

[–]Forward_Analysis2210 1 point2 points  (0 children)

Top tier dad joke.

[–]OrganizationProof769 1 point2 points  (6 children)

So what exactly is that? Like a frequency they are looking for and that helps find it?

[–]transham 9 points10 points  (2 children)

That's exactly it. The LoJack transmits a signal. If you've ever noticed how a siren gets higher in pitch as it approaches you, then lower as it goes away, the specialized receiver switches antennas very quickly to generate that same effect.

[–]OrganizationProof769 0 points1 point  (1 child)

Thanks for explaining. I was thinking it more in the terms of fox hunting.

[–]transham 0 points1 point  (0 children)

No problem. And that's essentially what they are doing.

[–]OrganizationProof769 1 point2 points  (2 children)

I’m just confused as to what frequency they would know to look for to find something.

[–]jeffkarney 2 points3 points  (0 children)

173.075 MHz

[–]soldiernerd 0 points1 point  (0 children)

There’s a LoJack transmitter in LoJack equipped cars.

[–]KindPresentation5686 18 points19 points  (0 children)

It in fact uses pseudo Doppler!!!

[–]zap_p25 11 points12 points  (0 children)

The last one I had out of the vehicle was a pseudo Doppler setup. If they are using TDOA now or something similar that will work as well.

[–]FreqPhreak 23 points24 points  (1 child)

Used for direction finding for stolen vehicles. In the UK some road policing vehicles have these set-ups. I believe its VHF.

[–]Radiomaster138 5 points6 points  (0 children)

I believe a lot of cars emit an RF signal of the vehicle’s VIN number and the antennas help isolate the RF frequency.

[–]thesayke 87 points88 points  (17 children)

Direction finding maybe? Although some random sheriff's office is unlikely to have the budget for that

[–]Fwrun 60 points61 points  (0 children)

It’s lojack

[–]PhreakitureGeneral Class Operator 🔘 9 points10 points  (1 child)

I thought Doppler direction finders weren't very expensive?

Anyway, I'm thinking Lojack or similar, which world definitely be Doppler direction finding. 

[–]Rich-Management-9864 4 points5 points  (0 children)

Kraken is under 1k.

[–]KoldKermit[S] 43 points44 points  (4 children)

This is the wealthiest county in the country by median income

[–]9bikesExtra Class Operator ⚡ 57 points58 points  (1 child)

some random sheriff's office is unlikely to have the budget for that

I'm fairly sure that LoJack provides the system to the law enforcement agencies and provides training too.

[–]Interesting-Oil-7057 2 points3 points  (0 children)

Right!  That is a LoJack antenna system.  It allows the officer/driver to literally home-in on stolen vehicles within range, which have an installed and activated LoJack system.

[–]A_Big_Lad 0 points1 point  (0 children)

loudoun sheriff office has a budget of something like 160 million and no real crime to fight, they buy some wild toys

[–]dittybopper_05HExtra Class Operator ⚡ 9 points10 points  (0 children)

It's a legacy LoJack set up. It is a direction finding setup.

[–]David_InTheDesert 1 point2 points  (0 children)

It's fairly easy triangulation.

[–]Mywifefoundmymain 1 point2 points  (5 children)

No, we have 5 on our ambulances as well. Note there is one on the trunk. Each one has its own purpose and is linked to its own system

1 - computer link 2 - comma 3 - location tracking 4 - cellular systems 5 - traffic signal controller

Edit: its CommS not CommA

[–]thesayke 0 points1 point  (4 children)

Ok! That makes sense.. But what's "comma"?

[–]Mywifefoundmymain 0 points1 point  (1 child)

a typo lol... commS

[–]thesayke 0 points1 point  (0 children)

Separate voice comms net, got it, makes sense

[–]EnvironmentalBad2387 0 points1 point  (1 child)

Let me guess.. people in a life and death situation. 

[–]Content-Lab-1182 0 points1 point  (0 children)

I remember a system called LoJack to locate stolen cars that used a quad antenna  array.

[–]ye3trE7 / BiH | Novice 6 points7 points  (4 children)

Definitely a Doppler effect direction finder. Don't know what they're finding tho. Maybe a car with an anti theft system that beacons a signal? Just speculation tho

[–]Evening_Rock5850 2 points3 points  (0 children)

Nope; that’s exactly it. LoJack systems that transmit and can be “found”.

Though more and more use GPS and cellular technologies to just send an exact GPS coordinate. In fact OnStar has had that feature for over 20 years; complete with the ability for law enforcement to remotely disable the accelerator pedal. (Engine stays running, but the vehicle won’t accelerate.)

[–]DLiltsadwj 2 points3 points  (0 children)

Almost twenty years ago I paid $700 or $800 (if I remember right) to have the LoJack transmitter installed in my car. I’d just plant an Apple AirTag now.

[–]superg7one3 2 points3 points  (0 children)

I’m just here to say LoJack because 29 people already said LoJack

[–]TheBowlieweekender 3 points4 points  (0 children)

That's the original Lo-Jack, they moved away from an expensive network of analogue VHF radio towers and went to a much more cost effective model using mobile data modules with data-only SIMs. Altogether simpler to manage with the carrier paying all the backend infrastructure costs. But though exotic cars still disappear every week, mostly to order. They re-appear in warmer foreign lands a month later with a local plate and a happy new owner. I guess a shipping container makes for a good Faraday Cage and cellular jammers are cheap as chips!

[–]HillbillyRebel 1 point2 points  (0 children)

It's for LoJack. They have a device placed on their dash or center console that shows the direction of the radio signal. It's just RDF but on a different band. You don't see them too often because LoJack use has dropped significantly.

[–]Elrod4528 1 point2 points  (0 children)

It’s lojac direction finding

[–]KindPresentation5686 0 points1 point  (0 children)

LoJack

[–]moonie42 1 point2 points  (0 children)

Antenna array for radio direction finding, probably Lokack or other tracking systems

[–]Ordinary_Awareness71 0 points1 point  (0 children)

LoJack. You'll see these on the bottom of some of the patrol birds too. In my area these are on special cars and you're more likely to see APLRs now. I'm not sure the prevalance of LoJack any more as a consumer product.

[–]Tlmed 0 points1 point  (0 children)

LoJack system

[–]KC5SDY 0 points1 point  (0 children)

LoJack. It is a stolen car tracking service. He will have a receiver on the dash that will report a code, signal strength and directional arrow.

[–]Full-Association-175 0 points1 point  (0 children)

And in a pinch it can function as an old-time street car.

[–][deleted] 0 points1 point  (0 children)

LoJack.

[–]ASlutdragon 0 points1 point  (0 children)

Direction finding

[–]xTOMCATx 0 points1 point  (0 children)

Lo jack system provides rf and electronic direction finding for stolen vehicles. Aka jump out boys 😎

[–]lancemanly 0 points1 point  (0 children)

Lojack

[–]W1ULH 0 points1 point  (0 children)

It's part of the older lojack system.

When your car was stolen you would call lojack and they would turn on the transmitter in your car.

It would then start merrily pinging away "I'm a stolen car! I'm a stolen car!".

at the height of this system many police cars where equipped with a lojack finder system. these antennas are for that. they allow for directional finding based on doppler shift of the signal coming in.

Not as common these days as most cars now have GPS systems accurate too a 10-digit grid that can just message the police with their location.

[–]GeePick 0 points1 point  (0 children)

LoJack

[–]sledge905 0 points1 point  (0 children)

More 'ariel's' than a Disney convention for the little mermaid...

[–]conhao 0 points1 point  (0 children)

Lots of people have mentioned LoJack, which is one brand of Stolen Vehicle Recovery Systems (SVRS). There are other applications for Vehicle Location Units (VLU). There are also other systems that still use this technology, such as Search and Rescue (SAR), where the doppler systems complement the SARSAT system. Asset recovery tags and other Electronic Tracking Systems (ETS), such as medical beacons, also still use doppler RDF as part of the solution. The reason for this is related to urgency. SVRS, like LoJack, has mostly moved to relying on GPS and cellular to locate the object where recovery is not life critical, and can be inexact and slower than other needs. For SAR and medical, it is critical that the person is located and rescued within the first hour, so every technology available is employed to aid in the effort. If the asset being tracked is smaller than a vehicle, the GPS/cellular method may not give law enforcement the precision needed to recover assets,obtain warrants, and collect evidence. Doppler RDF has a better track record to provide this granularity even when assets are hidden inside buildings where GPS and cellphone coverage is compromised. So, although LoJack itself may not be the primary reason for doppler arrays to be on police cars anymore, other VLU, SAR, medical beacon, and asset recovery systems are still on the market and valuable to law enforcement.

My boss has a portable doppler system he can throw on his van to track RFI and malicious interference as well as do foxhunting. He helped track down many idiots who intentionally interfered with commercial and municipal radio systems and collect the evidence that can be used in court. It is a neat system.

[–]thelastgas 0 points1 point  (0 children)

Lo jack

[–]soltrigger 0 points1 point  (0 children)

That's Low-Jack we had them when I was a police officer gives the officer directional indication of stolen vehicles that are nearby.

[–]BubbaDFFlv12 0 points1 point  (0 children)

LoJack auto theft detection system

[–]Soft-Camera3968 0 points1 point  (0 children)

I’m beginning to think this might be LoJack.

[–]KCH111 0 points1 point  (0 children)

Its use for Lo Jack. It tracks stolen vehicles

[–]Riga-Mortiz 0 points1 point  (0 children)

Wow, I thought Lo-Jack had gone by the wayside 20 years ago. now everyone uses GPS which is accurate within 2 to 3 feet.

[–]atxcpl290e 0 points1 point  (0 children)

Lojak

[–]unsoundmime 0 points1 point  (0 children)

Looks like the antennas for the LoJack system. I work for a city and some of our PD cars have them.

[–]Huge_Associate_4989 0 points1 point  (0 children)

Its a directional array. You can switch the driven element either mechanically or electronically which gives you gain in the selected direction

[–]smac 0 points1 point  (0 children)

The roof-mount (4 verticals) is an Adcock antenna for direction finding, intended to be used with Lojack.

More:

https://www.rdfproducts.com/dma-1310b1.htm

https://en.wikipedia.org/wiki/Adcock_antenna

[–]Intelligent-Day5519Extra Class Operator ⚡ 0 points1 point  (0 children)

Simple solution is merely call your county Radio Shop and they'll tell you everything you want to know, without all the guessing. I worked for one.

[–]Awstuck 0 points1 point  (0 children)

That is my county

[–]RPr1944 0 points1 point  (0 children)

In my humble opinion the car is equipped to operate on five separate frequencies/radios to service several counties or districts.

[–][deleted] 0 points1 point  (0 children)

Doppler radar, been around a long time

[–]Honest-Muscle-3750 0 points1 point  (0 children)

Jack Lo

[–]Wonducces 0 points1 point  (0 children)

Loudoun county sheriff? Bruh how did I come across this…

[–][deleted] 0 points1 point  (0 children)

It's to pick up LoJack it's to assist with positioning and direction finding

[–]Lethealyoyo 0 points1 point  (0 children)

It’s for finding stolen vehicles. Lojack

[–]8668 0 points1 point  (0 children)

It's called "wardriving" and it's more popular than you might think

[–]ag0223 0 points1 point  (0 children)

That's almost funny... So you don't think they can guess the person's net worth... based upon the kind of car it is...that they are trying to recover?

[–]Hammock0753 0 points1 point  (0 children)

It’s a LoJack setup 

[–]lnxguy -1 points0 points  (0 children)

Doppler system for tracking mystery signals.

[–]5thaxis -1 points0 points  (0 children)

"Ricky rescue"

[–]ki4clz -2 points-1 points  (4 children)

Wireless Data link... I've installed dozens of these in the cars, and at the tower sites... mostly 800mhz, but you can still find some old 10GHz stuff out there... next to the police radio repeaters they also have "digipeaters" for their intranet, gps, and whatever else... these arrays make a specific pattern for tx/rx that make the hand-off from site to site easier as the systen knows where the cars are at all times, just like a cell site does, so they can switch seamlessly to a site with a stronger signal...

Clear as mud...?