Flush Out Car Thieves with a Key Fob Jammer Locator

We all do it — park our cars, thumb the lock button on the key fob, and trust that our ride will be there when we get back. But there could be evildoers lurking in that parking lot, preventing you from locking up by using a powerful RF jammer. If you want to be sure your car is safe, you might want to scan the lot with a Raspberry Pi and SDR jammer range finder.

Inspired by a recent post featuring a simple jammer detector, [mikeh69] decide to build something that would provide more directional information. His jammer locator consists of an SDR dongle and a Raspberry Pi. The SDR is set to listen to the band used by key fobs for the continuous, strong emissions you’d expect from a jammer, and the Pi generates a tone that varies relative to signal strength. In theory you could walk through a parking lot until you get the strongest signal and locate the bad guys. We can’t say we’d recommend confronting anyone based on this information, but at least you’d know your car is at risk.

We’d venture a guess that a directional antenna would make the search much easier than the whip shown. In that case, brushing up on Yagi-Uda antenna basics might be a good idea.

97 thoughts on “Flush Out Car Thieves with a Key Fob Jammer Locator

    1. this is the correct logic, it is the same when i saw a movie where they rf jammed the bad guy’s bomb, i immediately imagined that what if the bomb goes when the rf link is broken :)

    2. Cars in California make a lot of noise when locking. In EU fortunately people are smarter and stupid beeps at night are banned. What works were card which lock themselves when you walk away with youe RFID.

      1. Smart EU. Whoever thought wiring the horn to honk twice or whatever when the car is locked is not a smart man.

        On my car the audible beep is done using a quiet piezo speaker, so I don’t end up annoying anyone.

      1. The people in my neighborhood used to constantly beep their cars at all hours and wake me up as if they had a god given right to honk and beep every time they wake up to make sure their car hadn’t magically rolled away since the last time they beeped/honked it. One A-Hole even put the damn thing on a timer to honk every hour. Harassment, pure and simple.

        1. Really? The honking was that bad?

          Was there a really high instance of car thieving in your area? I’ve lived in many apartment complexes thus I’ve lived near a lot of people with a lot of cars. I have even had bedroom windows that faced the parking lot. I never had this problem. Overly sensitive car alarms… yes, those sucked but those super quick little beeps that a car makes when one locks it with the fob… I never noticed.

          I can’t speak about your specific issue. Maybe your neighbors really do have an obsession with over-honking their own horns. In general though.. some people are just too sensitive and should either get over it or not live around other people. This could solve a lot of problems much better than does additional legislation.

        2. As a good neighbor, I have mine set to no-honk. I don’t think my neighbors would appreciate 200W of electronic air-horn when I get home (First Responder, full lights and siren with horn-ring-transfer)

      2. My Wester European built Land Rover beeps only when you double lock the doors. But the sound of the locks is still quite persistent and so are the flashing lights. You have to be almost deaf and visually impaired to not notice.

    1. My car doesn’t beep on the first press of a lock button, but I can usually hear the locks click. If I don’t, a double-press of the lock button will elicit a beep — nice for double checking, or if I want everyone in the vicinity to know I locked my car.

      1. It’s not hard, but very inconvenient. Much more inconvenient than changing the battery to restore original functionality. I can not understand you.
        I normally hear the locks click or I look for the indicators flashing briefly.

      2. Some cars only have one lock that can be used with a key, hidden under a cover. You need a coin to remove it.
        And some cars don’t have any mechanical key locks. So when the battery in your fob runs out you need a brick to break in.

    2. Most cars flash too while beeping, so disabling beeps won’t affect feedback. Of course one has to pay attention and not simply push the button while walking away.

  1. Do normal people not automatically listen for the “beep-kachuck” of their car locking — I notice real quick if /any/ device sounds odd or fails to make expected sounds…

    seriously — is it just editorial rhetoric or or are many people /that/ unaware of the world around them?

    1. My car doesn’t lock immediately. It actually leaves the door unlocked for about 10 seconds, and THEN locks. I guess they figure you might wanna grab something at the last second that you forgot? I dunno. If I wanna confirm it by ear, i have to wait at my car awkwardly for the “kachuck”.

    2. I consider myself normal and am aware of the normal security implications RF systems.
      I thus ordered my car on purpose without RF key lock and simply use the normal mechanical key in the mechanical lock.

      1. You’re not normal. This isn’t necessarily a bad thing, but if basically everyone is using the fob and you’re going out of your way to use a key, that by definition can’t be normal.

        1. That depends. Is everyone using the fob because it’s the default (i.e. you have to go out of your way to get a car without RF locks), or because everyone really wants to. FWIW, my car doesn’t have remote locks either. I know my car is locked because I locked it as I got out (don’t need to use the key for that).

    3. Interesting question, further investigation required. My personal observation is that men are conditioned to be more aware of the diagnostic value of sound when dealing with technology, but that is obviously just a generalisation based on anecdotal evidence.

    4. I do, although without a beep. But I know, that this method of breaking into cars is used “successfully”, so it is definitely an issue. Probably some people, e.g. mother with two small children, are distracted enough to not look/hear for proper locking of their car.

    5. my truck doesn’t make any special noise, if it is quiet enough you can hear the power locks. And you can see the turn signals flash if you are standing right in front or behind the truck.

  2. Instead of confronting the scum yourself, you could simply inform the police instead, and hope they care enough to pay them a visit. They generally do appreciate the silver platter.

          1. Let me teach you a trick: in the dark, take your key in your hand, then extend the tip of your index finger to touch the tip of the key. Find the keyhole with your index finger nail. Without losing the contact with keyhole, slide the tip of your index finger over the edge of the key to insert the key into keyhole. Try on light first until you get the feel.

          2. I do it like salec describes. Not only for keys but also for finding and inserting misc connectors in the dark or in inconvenient places. Thought everyone did it, never understood why anybody would scratch their car with the key except when drunk…

      1. Lemme try to solve this problem for ya!
        I’ll have to assume you have something in other hand (usually a cell phone. thus the loss of situational awareness that others have mentioned)
        Hold key between thumb and first finger.
        Use middle finger to touch keyhole.
        -Usually- solves that location problem for me.

        1. I hear ya Martin. I just was trying to throw out something for the key crowd.
          I actually used the fob for my vehicle until I figured out that it always seemed to end up in my pocket and thus beside of the keys.
          Was a bit interesting trying to figure out why about every second step seemed to try to cycle the locks or alarm/panic button, when I first noticed it happening.
          If you try to orient the keys in a tip down position, they tend to rip pockets seams and then just gravity flip to head down anyway.
          As a result I ended up just chucking the fob into the spare key drawer.
          The keyhole finger trick just was handy for all the doors, residential or vehicular, that this dinosaur grew up around.

          Prior to the advent of cheap LEDs, carrying a penlight was an iffy proposition to count on for finding keyholes. battery life was short with incandescent bulbs and dropping one was a good 60% chance it would break the filament.
          Old habits that serve(d) me well just seem tough to break.

          1. Argh. That should have said “I actually used the fob for my vehicle until I figured out that it always seemed to end up in the bottom of my pocket and thus beside of the keys.

            10 minute edit button please?

          2. Your correction was not necessary, I understood the meaning (like button gets pressed inadvertently). But I also would like an edit button. They could make it 5min or until a follow up post comes.

            Luckily the keys of my car-keyfob are hard enough to press, that this is no issue, although I have the car key in the same pocket as a big keyring with a 5W LED torch (LiIon AA) attached to it. So it definitely has some bulk. :-)

  3. I press the physical button inside my car most of the time nowadays. I’ve had my keyfob jammed before, but it was almost certainly RF interference from the giant wall of electronics in the building.

    1. The one that cracks me up is my car won’t let me press the lock button if the door is open and the fob is in the car. It doesn’t want me to lock the fob in.

      Of course, it also has a bunch of “safety” features that get a little annoying, like a triple beep if I leave the car running but get out and close the door. If left running but stopped, it will turn itself off after an hour, and ACC mode only lasts 10 minutes after it’s activated. Don’t want you sitting in the car and listening to the radio. lol

      1. If I switch on the radio with enigne stopped, it would switch it off after one hour. But you can press the button again. It also has another nice feature: If the battery runs low, it issues a warning and shuts the radio off, if you don’t override.

      1. that won’t work on the newer Dodge/Jeep/Chrysler cars with the keyless entry since the car will simply unlock itself again when you touch the door handle. It took me a few months to get used to not testing the door handle.

  4. If they are that desperate to get in I’d rather they jammed my keyfob than smash a window.

    The cost of the side window they are likely to smash is quiet likely more than the value of the goods they are likely to get….

    Just speaking from personal experience

    1. Funny you mention value of things contained in the vehicle.

      Here’s a list of things very likely to get stolen from cars, especially from not so old but not brand new ones: Satnav unit. Steering wheel. Climate control unit. Instrument cluster. The whole bloody dashboard. And so on.
      Over here in germany, the high-priced vehicles manufactured by Audi, BMW and Mercedes, but also the more appropriately priced products of VW are perfect targets for organized groups coming from the eastern-european countries.

      To be fair, they do not screw around with keyfob jamming, they just smash the one window that makes the least noise upon smashing, open the doors and disassemble half of the interior in a very quick and very professional manner.

      1. Damn… here they just grab whatever looks like it might have something valuable in it. I got a bag of laundry stolen once, and I knew someone that had a diaper bag full of dirty cloth diapers stolen, that must have been a bad day for the thief. A local nonprofit got the canvas for their fair tent stolen, because it was a heavy duffel bag and looked more valuable than it was.

  5. This only works if the thieves are transmitting while you’re sniffing. Normal operation is to watch the victim and jam only when they’re about to press the button. So unless you were lucky enough to see them jam someone else, this won’t catch them.

  6. No-one seems to get the point of keyfob jammers here.
    The idea is they get the rolling key by jamming your key & capturing it, then capturing a second key and transmitting the first.
    This means they can unlock the car once you’re gone, and all you noticed is a delay in your car unlocking.

    1. If you every have to double-tap to get your car to lock, walk away.. while they think they have your code and just within range of your car… hit the lock again. If you hear any swearing turn and stare – or just call the cops. In the US you’d indicate your concealed carry and smile.

      1. You, Sir know how to carry concealed!
        Unlike some deranged bike hating, normal American citizen shaming, shamefully “Stereotypical-American” person who posted on HaD his hate for bikes on the space-race article.

        When you catch him, usually they’ll be too busy and likely at a distance. You can hold him there and make a citizens arrest (I assume Citizens have such a power in the USA) and he’ll get the prison time, hopefully as long as he deserves. approaching for finer aim but not close enough to give him a chance to disarm you. If he then tries to get his gun out, then you can shoot him in defense in an attempt to disarm him even if it kills him.

        For this reason, I’d like more lax laws here in the UK… First I’d have to leave the UK whilst the idiots kill each other off in paranoia and when the sensible ones are left… Then return, save up for training and get licensed (Hopefully it’ll be cheap enough to save up for in a few months)

        1. No, they don’t know how to carry concealed, because “showing someone you’re concealed-carrying” is not “concealed.”

          It’s called “printing” and in many states with concealed-carry, it is enough to get you cited and lose your license, and if it’s done purposefully, it’s called “brandishing” and it will get you jail time.

          1. I don’t carry anything remotely misconstrued as a weapon – defense or otherwise because I live in a Orwellian nanny state and doing such weakens any self-defense claims. Seriously.

            I was poking fun at the way americans share their love of guns in youtube/movies.

            It’d be an interesting addition to a cops sensor network to detect jammers as they patrol… though that would require them to actually patrol hotspots.

    2. Easier and more often they just jam your try to lock the car and if you don’t notice you leave your open car and they are in. If you notice, then they try the next one. There are enough potential victims on a big parking lot.

    1. Except for when they want to have parts of you car instead of your puny valuables. An iPhone is what, $600-800? But an OEM satnav/entertainment unit out of e.g. a BMW is somewhere around $5k.

  7. My car has a lock button on the inside of the door. I typically use that because my key fob is in my pocket, so it’s easier to just press that. It also has a sensor on the door handle that locks the door when touched with a finger or thumb. If I use the key fob, I can press it once and hear the door locking mechanism quite easily. If I really need extra confirmation, I can press the fob twice and get an audible confirmation from the horn. I rarely do that, reserving that only for when I want to let others know I’ve locked the car, such as when I’m parking in an area that’s not as comfortable as I’d like. Honestly, if that doesn’t prevent a theft, I have insurance. I’m not going to waste my life worrying about things less likely to happen to me than getting struck by lightning or eaten by a shark.

  8. or you can just make sure the lights flash or horn honks or whatever your model does. If it does this the CAN chip roles the code.. If it doesn’t someone is jamming.. No need for an expensive solution..

  9. I just lock my car with the fob, watch for the blinking headlights, and don’t worry about it at all because I don’t live in an area with hordes of roving bandits and police who ignore 911 calls. vOv

  10. My car is 13 years old. The only anti-theft protection I need is its appearance and the fact that I give zero shits about it getting stolen. Granted, my method won’t work for everyone but it works here :) I also count on the fact that whoever steals it will ride 2nd gear too hard and hear a bad popping sound before being left stranded lol. It’s paid for though lol.

    Oh man I totally hear you guys on the %*$&%^ alarm armed beep. Jeebus, my neighbors used to do it all the time when we lived in an apartment complex. One set of neighbors in particular would literally wait for people to walk by and then “arm” it while laughing hysterically at the poor jumping rube (and no it was not just set to ‘falling leaf’ sensitivity). I ended up giving them a bellyful of their own medicine by parking in front of their unit and checking my alarm every hour for a night or two which quieted things down for a while. The temptation proved too much though and the last I saw of the whole mess was some old lady and her daughter yelling at them about how it wasn’t 1989 anymore and people all had cellphones and car alarms so learn to use them. Luckily their Section 8 voucher was revoked because of several abuses (other than that) and they were evicted. Oddly enough they ended up moving back in on the (now adult) son’s newly-acquired voucher about 3 years later smdh but were promptly evicted again for losing that over him scamming several “community-building” organizations out of money. It was an awesome sight to watch his Maserati violently beeping as it was repo’d when I was leaving for work one morning. My CSB
    These stories of western europe banning such a thing sounds great! No one does shit when they hear alarms anymore anyway lol. Just figure it is some asswipe pushing the wrong button or forgetting it is locked and trying to open the door.
    Now to get a “polite” horn and “angry” horn installed on cars :D

      1. That’s great. Read the third sentence of my post again (I apologize for the length). They will probably make it 100 yards before leaving second gear in the middle of the road, hopefully wrecking out into a phone pole or a family of four so they get put away for a while. I pay insurance for just that reason and nothing beyond a bunch of industrial music CDs from the 94-98 era are even in there unless they have some sort of cloth shopping bag fetish.. I hear ya though. I should really park it at the boat ramp if I want it to be stolen faster :)

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