Police Baffled? Send For The Radio Amateurs!

The police force in Evanston, Illinois had a problem on their hands. A mystery transmitter was blocking legal use of radio devices, car key fobs, cellphones, and other transmitters in an area of their city, and since it was also blocking 911 calls they decided to investigate it. Their first call for help went to the FCC who weren’t much use, telling them to talk to the manufacturers of the devices affected.

Eventually they approached the ARRL, the USA’s national amateur radio organisation, who sent along [Kermit Carlson, W9XA] to investigate. He fairly quickly identified the frequencies with the strongest interference and the likely spot from which it originated, and after some investigation it was traced to a recently replaced neon sign power supply. Surprisingly the supply was not replaced with a fault-free unit, its owner merely agreeing to turn it off should any further interference be reported.

The ARRL are highlighting this otherwise fairly unremarkable case to draw attention to the problem of devices appearing on the market with little or no pretence of electromagnetic compatibility compliance. In particular they are critical of the FCC’s lacklustre enforcement response in cases like this one. It’s a significant problem worldwide as huge numbers of very cheap switch-mode mains power supplies have replaced transformers in mains power applications, and in any center of population its effects can be readily seen with an HF radio in the form of a significantly raised RF noise floor. Though we have reported before on the FCC’s investigation of the noise floor problem we’d be inclined to agree with the ARRL that it is effective enforcement of EMC regulations that is key to the solution.

City of Evanston police vehicle picture, [Inventorchris] (CC BY-NC 2.0) via Flickr.

88 thoughts on “Police Baffled? Send For The Radio Amateurs!

    1. Same thing here in Belgium. The guys from the radio regulator do a pretty good job searching for radio-interference.
      For policing the ham-bands, the FCC has very simply “outsourced” that to the hams themself (but on the other hand, there are more then enough hams in the us who like “to play cop” if they get the chance to do so).

      I think the US citizens get the governement they vote for: if your motto is “as little gouvernement as possible”, don’t complain if you then have issues like this.

      1. The problem is the Government we do have dosen’t do their Job. Instead they are more concerned with stopping open source firmware, then finding rouge raido signals. Why would we give them more power to not do their job?

    1. Actually, it wouldn’t have made a difference. When I worked at a radio station and someone deliberately was causing interference, we still had a very hard time getting anyone from the FCC out. Then it was only after we traced it all down to who was doing it and where it came from.

      Sadly they just aren’t given the resources that they need to enforce they way they should.

          1. i have considered that solution before, however it only seems feasible for a single term cycle. after the first forced-rotation, there would need to be a secondary system that would force someone to apply to be put in the position next. no one wants to take a job that definitively results in their death, it goes against most fundamental aspects of human nature.

            but forcing someone into a political position they don’t want to be in that results in their death if they do something wrong generally doesn’t do anything for morale, which would then progressively speed up the entire ‘they screwed up, shoot, install next person’ cycle, until either the supply of candidates was exhausted, or a different system was put in place.

    1. Fine enough to cover the cost of enforcement and investigation of that case. If it’s an amateur running a spark gap transmitter, they pay. If it’s a manufacturer with a SMPS spewing stuff out, then fine them.

        1. Someone imported it. If that was the person who plugged it up to their neon sign, then they might have demonstrated a lack of regard if there was no FCC/CE/UL marks on the device (or if they bought it from AliExpress). Otherwise, find the company or person who organized getting these devices off the boat from China, and start levying the fines.

          Yes, it’s harsh to fine an individual. But if they can show that they had reason to believe the devices were legal, then the FCC can start throwing fines higher up. Remember, Yahoo! owns part of Alibaba now, so if we can’t reach the companies directly we can hit their pocketbooks.

          1. It is getting to the point now where something needs to be done. I imagine most of the offenders are just ordinary people who bought something cheap from China and wouldn’t know a MHz if you bought them it for xmas.

            My solution would be to confiscate the offending component, at the user level. For vendors, give a warning, then after that a series of escalating fines. If they deliberately disregard the law, then maybe something more serious.

            I think the heart of the problem is Ebay, Amazon, Alibaba etc. A new phenomenon, customers buying direct, or nearly-direct, from manufacturers. Or from vendors in countries (oh hell, I’ll just say China), where it’s much cheaper to operate a retail business from. Being Internet-based means no need for a store front. Just somewhere to stack the boxes, and I bet there’s a few businesses with stacks of stock in somebody’s kitchen.

            The companies are diverse and have names that mean nothing to a customer. The seller generally speaks no English at all, or very little. This means no brand name value. No relationship of trust between customer and seller. It’s anonymous to anonymous. So there’s no point in trying to build up a reputation for value, instead it’s better to knock 2 pence off the price, so you stand out among the other thousand vendors in an Ebay search.

            Equally this anonymity means governments can’t enforce easily, as does the language barrier and all the other problems. Companies can come and go overnight, they don’t even need to hire a signwriter to change their identity.

            There really needs to be something done about this complete absence of trust and trustworthiness. Not sure what. Ebay etc could do better, but do they care? In fact, Ebay’s policy of offering lower fees to companies with higher star ratings, means companies beg for ratings, and customers feel obliged to give a higher rating than they really feel is deserved. Tying it to money makes the rating process worthless, worse than worthless, when apparently a quarter of all reviews on Amazon are by agencies who will write ratings for cash by the hundred.

            Big problem. I wonder how something like Game Theory would sum the situation up? Or sociology? If it can find it’s way out of being a ridiculous game for ridiculous people to play “Top Victim” with.

  1. So…the part number and supplier of this magic transformer that wipes out cell phone traffic is…? I need about seven of them for my classroom and car.

    Just for research purposes, you understand.

    1. The cheapest model you can find, of course.

      Inductors? what are those? We just squiggle traces on the PCB, same thing.

      Capacitors for filtering? Nah those are expensive, only populate one out of every 3 needed.

    2. Such a thing is not magic, it’s just trash. And if somebody would use such a thing and disturbs my communication, I would suggest other fields of research: How it feels for this guy, when this device hits some of his body parts.

      I can not in any way understand the wish for such junk in my own car. Normally I want good reception, when I use the phone, and when somebody else uses his phone in my car and I had a reason against this then I would just ask the person to stop it (or get out of the car).

  2. fortunately police now have cell phones witch are much more immune to interference and are more secure.

    immune because unless you have a transmitter in the exact frequency range used by cell phones witch the pwm chopper is least likely to do there is no way to take down cell phones outside of then taking a tower down by car accident for example.

    secure because the cell phones operate in frequencies that are banned from most scanners and even then you will just get some kind of buzzing or static as they conversations are not in plain signal.

    so if you are unable to communicate by your radios then use your cell phone and talk to the 911 dispatcher.

    1. Read the article again. The first paragraph will do.
      “A mystery transmitter was blocking legal use of radio devices, car key fobs, cellphones, and other transmitters in an area of their city…”

      1. “after some investigation it was traced to a recently replaced neon sign power supply. Surprisingly the supply was not replaced with a fault-free unit, its owner merely agreeing to turn it off should any further interference be reported”

        that’s why i said pwm chopper.

        besides the point i was trying to say is just change communication devices so instead of the 911 dispatchers using radios they should switch to cell phones

        1. Er, did you miss that you can mimic a mobile phone tower? Google “Stingray surveillance” and read up before you spout such nonsense about them being secure!

        2. I’ll simplify the sentence I already pointed out to you….

          ““A mystery transmitter was blocking legal use of… cellphones…”

          As was stated later in the same article. The neon sign power supply *blocked* the use of cellphones. Ergo, no 911 calls can be had. The police weren’t just concerned about their *own* equipment, but those in use by the general public. Once again, a point that was brought up in the original article.

          The problem with your statement is it completely ignores that cellphones were blocked in the first place.

    2. GSM, if it uses the A5/1 (1987) cipher, these days is about as secure as the fence around your house is at keeping people out of your yard.

      Part of the reason for security in almost 30 year old encryption being broke was because of requests from governments and law enforcement to weaken the encryption at the time it was created.

      1. You mean A5/2? A5/1 is still pretty secure. Sure, you can crack it with a 4TB rainbow table and a lot of modified hardware but it’s not exactly plug and play. It’s not as if you can easily listen in to every call in the neighbourhood like you could with the analog phones that preceded GSM (and which were in use until the late ’90s here in Europe). It was introduced in 1987 and only really demonstrated to be broken in 2008, a 20-year run is pretty decent for a first-gen algorithm IMO.

        It was A5/2 that was artificially weakened, and it’s been deprecated ages ago.

        Also in regards to this article, the encryption algorithm doesn’t really have much to do with its resistance to interference.

        1. A5/1, which can be cracked in less than 1 second, (with 1.6TiB of publicly downloadable rainbow tables), is not secure. OK you need a large SSD and a few high end graphics cards, it does not matter if the hardware to do so costs $150, or $1500 – it is still broken.

          A5/1 was actually weakened as well, the British GCHQ wanted it weaker and the West Germans wanted it stronger. (ref: https://en.wikipedia.org/wiki/A5/1#Security ).

          I was replying to ejonesss who thought that mobile phones are secure. I never claimed that resistance to interference was improved by encryption, and neither did they.

          But you are right A5/2 is no longer supported by handsets, but strangely any base station can tell a handset to turn off all encryption, which is supported by all handsets, and almost none will inform their owner.

    3. AFAIK local law enforcement around here use the same cell phone networks the general public uses. While some older scanners can receive them, all new scanners in the USA have blocks of the RF spectrum disabled. However a receive transverter would open them up to old and new scanners, but of course any encryption would still prevent the actual traffic from being understood

        1. agreed, with only needle-nose pliers and a loss of warranty, you can adjust both the input freq. as well as the output (seperate ideas)

          but the output adjustment WOULD NEED A WHOLE NEW HARMONIC FILTER on output… assuming you are amping it and transmitting it, not that you would be… otherwise see article above

      1. There are plenty of “scanners” available in the US with no restrictions on what frequencies are received. A cheap one plugs into any laptop, sells for $20, and can tune from 20MHz to 2GHz.

    4. What frequencys would be “banned from scanners”? Especially as Hackaday reader you should have already heard about SDR and HackRF. So reception is easy, but of course it’s digital and probably encrypted.

    5. The police don’t have cell phones “only” anywhere that I know of, they rely on two way radios primarily. and the cost of paying for every officer a cell contract is out of the question in a lot of departments due to cost. It’s much harder to deal with a cell phone on patrol, even a PTT model, its harder to do “all call” where you want everyone on shift to hear you, not just dispatch, and not everyone lives or patrols urban areas where cell reception is a guarantee. A lot of the newer P25 and NXDN radios are digital and have a lot of similar functionality as a cell phone and can even do data for MDT laptops along with AVL using GPS.

      Cops may use a cell phone from time to time when they have a signal and need to call home or dispatch, but none of them use cell phones full time….

  3. I’m surprised at the FCC’s lack of concern about this…
    No, actually I’m not. Not even slightly. The only thing the FCC seems to care about these days is making money by selling off spectrum that they are supposed to be managing. Bunch of bureaucratic morons with their heads shoved so far up their rectums that they can see their own small intestines.

    1. Actually it’s the electorate who are the morons, if not morons, pretty damned ignorant. Land owners and merchants started the American revolutionary war and wrote the US Constitution. Therefor our government is government of the merchants by the merchants for the merchants. Pay attention to the news to discover while conservatives and libertarians falsely blame liberal for regulation, it’s the merchants who write most of the actual regulations. In my direct comment to this topic I pointed out this will never be reported in a manner the public affected will never learn that their devices where affected, and why they where affected.

      1. Wow, so my ancestors from 10 generations ago are somehow to blame for the decisions of non-elected government officials in 2016? If only they had known, they could have shoved their heads up their arses and just continued to deal with the nightmare of British rule and saved us all the trouble of having a minor inconvenience or two. What a shame.

    2. Well soon you don’t have to worry about FCC, since the big ISPs are paying for laws to disable FCC completely. I don’t know, not counting the router firmware fiasko, FCC has done a few nice decisions. They don’t much consern me, since i don’t live in states, but still.

  4. I’m partially surprised they ignored it. Partially because they apparently didn’t ignore an complaint from Verizon about cell interference here in LA 2 years ago.


    Apparently the police having issues isn’t a problem, but big business having issues is…. at least the police got help from people who cared. As an old ham operator used to always tell us, “When all else fails… Amateur Radio”

    1. Undoubtedly at all levels it matters who is making the complaint. Along with who and the area being affected. Many of we hams could find the source of the problem, but there’s much they can do after that. In this case all they could recommend the sign owner replace the faulty component, if the sign owner need to use the sign 24/7. Not far from here a FM broadcast station can be herd in the 2M band. The station engineer i unconcerned as , the FCC is unconcerned as well. I don’t know all the details, but if it’s a result of of intermod, not created by any faulty equipment anywhere, the hams may have to resolve themselves to the fact it’s going to be there. Although the attitude of the broadcaster and the FCC is disconcerting.

  5. This article ALSO features the FCC refusing to do a job of RGI / EMI damaging or making impossible vital city and other emertgency services…apparently the FCC could not have cared less.

        1. It only works as idiom with heavy sarcasm, as it originated, “Yah, like I could care less.” Which is used to punctuate a previous statement rather than how it is misused in a construct like “I could care less about blah blah” which is prone to misinterpretation.

  6. Chances are incidents like these will never will reported in a manner where those affected will never know why the devices they used failed to work as intended. The public will never discover why performance standard are important and our government’s libertarian approach in self certification and compliance isn’t working on many levels. The government cutting it’s own cash flow for the benefit for the already well off has an effect on investigation and enforcement. The purchaser of a sign component that can’t be used as intended has been robbed, and knows to raise hell. Until those affected by he faulty sign know they where affected and raise hell new new status quo will remain and become worse. The paradox is the proliferation of unlicensed devices will cause a noise floor problem affecting the users of those devices. Hopefully the manufacturer of the faulty component has provided the sign owner with a properly working one. Could be this was a lone defect, but without a fully funded functional FCC, it will never be known if there is a poorly engineered or poorly manufactured product that should be recalled.

  7. There was a similar incident Lubbock back in 2010.

    Sometime in Jan or Feb the spectrum band for the instrument landing system at the airport was flooded with a tremendous amount of energy and planes reported their instruments going erratic on final approach. Flights could no longer land in IFR conditions and had to be diverted to Amarillo. This was costing the airport, city, the airlines and the passengers a crap ton of money and it went on for weeks.

    Probably because of the danger and the money involved ALL agencies flew in to find the culprit. FCC, FBI, DOD sent electronic intel aircraft to help out as well and some “other” agencies came in too. They were threatening murder on the party responsible. Radio and TV stations were order to cease transmission for days to quiet the spectrum while tests were ran.

    I was working as a dev at a start up making field sensors that had lots of radios in them, mostly cell/wifi channels. We were pretty sure it wasn’t us but the notices put out by the agencies had us worried. They were out for blood and we checked and double checked with our analyzers to make sure it wasn’t us.

    They found some faulty transformers in the investigation and constructive interference from some radio stations but in the end they changed the ILS system to use a different frequency.

    The system does work(it helped to get the local congressman involved since his office is in the city). But we they are resolved they bring big tools and big hammers.

    a few articles about it. It was a very interesting problem.

  8. Until there is compliance at ISO 9001 levels with all stuff coming from the East with full provenance as to source of manufacturing and a functional warranty, there will be this mess.

    1. *milk-nose*


      iso 9001 means jack shit about product quality. it just means you have well documented procedures for producing shitty products.

      anyone can pay for, and receive, iso 9001 certification. it means nothing.

    1. Simple test, for the people who don’t know a wideband signal analyser from a guitar tuner, is to try to use an AM radio right next to it. If it farts and buzzes and crackles like hell, then you gots some shielding to do.

    2. [RW] has a very good suggestion here, the AM radio trick should cover your backside in many cases.

      And if you take care in your design you should not find yourself in this position in the first place. Many of the offending devices have had RFI-removing components cut to make them cheaper.

      If you want to delve deeper you can use an RTL-SDR as an improvised spectrum analyser for the higher frequencies, but it’s not calibrated in the way a purpose-built instrument would be.

      However you would find it very difficult to ensure FCC compliance in a home situation in the absence of an RF-proof ferrite-lined steel room and a very expensive calibrated test receiver and antenna. For full regulatory compliance you need to be sure the RF you are measuring only comes from the device you are testing, and not from external sources.

      1. Hey Jenny and HaD folks – a great follow-up to this article would be one that details the various ways that interference can be located and identified. The buzzing AM radio is a good starting point. Most of us would require some guidance to effectively use SDR to find interference. Some ideas for directional antennae and broadband detectors would be most welcome.

        Our house or neighbourhood is currently pretty noisy in the HF spectrum, which makes shortwave listening less than fun. I’ve done some basic sleuthing with a detuned AM radio, and switching stuff off and on, but so far I haven’t eliminated it all, though I have found some dimmers driving LEDs that are prominent offenders.

  9. In 1995, a US company making store theft prevention tags was using a particularly noisy transmitter to excite the tags as they left the store. While it was tested to be 902-928 MHz ISM band compliant, what they produced and sent out was not what was tested for compliance. Their device obliterated cellular uplink at 800 MHz…. especially to in-building… mall distributed antenna systems.

    Have you checked your MR16 LED bulbs? There is no room for EMI magnetics in that package…. I’ve found these MR16 to be the worst offenders right up to 400 MHz. Your garage remote doesn’t work anymore (315 MHz? Can’t receive some OTA TV channels or your AM radio is just buzzing?

    Years ago in the analog CATV world… a local police department with a repeater TX at 137 MHz or thereabouts was having trouble receiving their dispatcher for about 2 city blocks in a particular area. Upon investigating, the local RF AHJ found a property owner fashioned their own cable TV connection from the pedestal to their house using 16 AWG electrical extension cable instead of RG-6.

    Power line Ethernet modems unfortunately obliterate a lot of the HF amateur radio bands… no longer usable when the neighbour has these modems.

    Shop the Chinese direct mail order web sites? Their CE logo means China Export… nothing to do with the European Union mark…. Their devices could burn your house down if they don’t simply prevent your RF devices from working correctly. Chinese DECT phones made for Asia…. turn up in North America…. and it happens to be the cellular band. Interference results. Same to some other device where the ITU region band plans don’t line up… License free walkie talkies, etc.

    We could go on… RF is a very bloody business.

  10. Reminds me of a spot coming in to my old town. AM/FM car radio would fade to static and cell service died in a span about a quarter mile long on the main strip. I always wondered if it was intentional or even legal.

  11. Don’t the rules state that interference is the problem of the individual receiving the interference? So how is the FCC at fault for telling the cops to go figure it out and work it out with the offending party. This wasn’t intentional jamming, it was accidental interference, which the rules state its up to you to fix on your end i.e. “go buy a filter”

    1. Not sure about the US, but in most countries the fee for licensed spectrum also pays for some amount of spectrum protection. In practice this is usually difficult unless you can tell the agency exactly what is the source. Even then, it is much easier when you found the source to just knock the door and talk to the owner than to wait months for official resolution.

  12. I bought a brand new Sony Blu-ray player last Black Friday that would make a near by PC hard crash as soon as the Blu-ray player was turned on. If you turned the Blu-ray on before the PC the PC wouldn’t even boot. So much for FCC compliant devices…

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.