Amateur Radio Sleuthing Pins Down Source of Strange RF Interference
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I think it's a good reminder though that while modern wireless links represent a lot of fantastic engineering and are very valuable they can also be pretty fragile, and it's important to have a physical (be it digital or mechanical) fallback for critical tasks like authentication (in this case to access or startup a vehicle). There are situations where being surprisingly unable to operate ones vehicle (or access a building or whatever) could be quite serious, and the IoT ecosystem needs to give surprise interference some consideration as well. These sorts of incidents should also make society think about failure modes when it comes to interference, be it accidental or intentional. Law enforcement in particular should consider it from two sides, both in terms of emergency planning for if there was a major case (during an emergency or not), and as a strong note of caution vs some of the noises that have been made about LEOs themselves purposefully doing jamming during "periods of unrest" or the like. In an age of ever proliferating wireless devices, beware unintended consequences.
[Edit]: Thanks to Animats below for pointing out that it's UL approved Ventex, it's not in the article text but a photo is included at the bottom. So I guess that underlines SMPS quality control issues can be tough even with more attention paid, and shouldn't be taken for granted in planning even with part control. Though this also seems like it should make it something the FCC should give more attention in terms of confirming that this was a lemon and not an indicator of some more widespread problem. It should be easier for them to do that with a US-based operation.
It's so easy to make an SPS that is essentially a disaster for all RF spectrum around it. In fact, some of my early SPSs, I could "detect" they were on because the noise coming out of a radio receiver nearby would change when I turned the supply on.
OTOH, it's pretty easy to take measures that ensure the RF is kept under control. Shielding is important, but first make sure your circuit doesn't make excessive amounts of RF to begin with.
Myself also. I designed switching power supplies for the Space Shuttle, some of which were meant to power fluorescent lights. NASA wanted dimmable fluorescent lights in the crew quarters, but they also wanted no EMI. Well, they got both -- I figured out a way to dim the fluorescents using a magnetic amplifier instead of the semiconductor switching methods that were common at the time, and (as I intended) the magnetic amplifier created no interference at all.
The details: http://arachnoid.com/PDF_archive/IES_october_1976.pdf
Sounds about right.
TL;DR: Wireless power switch, if you put two of the wireless switches next to each other - they both stop working because they interfere with each other.
Sold every day at Bunnings (australian home hardware/etc store) by a major brand (Arlec)
In the early days of Lockitron we were using the 433MHz bandwidth. We would occasionally experience state wide non-response to our locks despite having full backend network connectivity. Eventually we tracked the problem down to sunspots. Coming from software it was one of the more bizarre things to debug.
Deploying those locks across hundreds of locations we saw quite a bit of unusual stuff. Locks would work fine on one side of a building but not the other - the bad side faced the San Francisco bay - deduced it was from all the SF/Oakland Radio traffic.
Another location would experience problems during baseball games. (Stadium was next door).
Cell tower guys have even crazier stories. One involves my colleague who had a bitcoin mine in his garage. Few dozen graphics cards humming along at ~900MHz knocked out the whole voice uplink for 4 square miles. (He happened to be pretty close to the cell tower and raised the noise floor just enough to make cell phones all but useless.)
Working in ISM bands can be brutal, but it will teach you a lot and quickly.
[1] http://www.space.com/14060-2011-restless-sun-solar-activity-... [2] http://www.space.com/10862-sun-erupts-powerful-solar-flare.h... [3] https://www.youtube.com/watch?v=heVeq_anewU
More likely, in that part of the spectrum, they were seeing adverse effects from (probably undisclosed) military R&D activities. Might as well have been sunspots, for all they could've done about it.
But other phenomena correlated with sunspots do cause UHF interference, so while wrong on the details I generally believe the story.
What would be some examples of such phenomena, bearing in mind that we're talking about very short-range wireless links in a band shared with primary military users?
It's not as if conflicts in that band haven't arisen before: http://www.w5yi.org/ama_news_article.php?id=191l
Another example: http://www.tdsupplies.com/articles/395_MHz_Military_Radio_Re...
The collapse of the magnetosphere on the night side following impact of a coronal mass ejection—which not only make a lot of VHF and UHF noise, they have enough power to just break a device.
On the surface of the Earth?
If that ever happens, you have much bigger problems than a malfunctioning garage door.
At 433 that's pretty close to the 432.1 band some of us use.
Its possible for sunspots to really mess with HF and lower VHF like the 50 MHz 6M band but way off for 432.
Sunspot correlation with sporadic E (bouncing off the ionosphere) is common up to 50 MHz and drops off rather fast. I've made hundreds, thousands of contacts on 6M sporadic E but precisely one in my entire ham radio career on 2M which is 144 mhz pretty far from 432.
What does mess with vaguely 2M and up including 432 is tropospheric ducting. Basically a weather front or extreme fog makes a poor waveguide out of itself. Its somewhat location dependent.
One 70 cm band specific problem that could affect 433 mhz unlicensed stuff in a local area might be (legal ham radio) experiments with wide band ATV using a channel that overlaps the unlicensed band. That has nothing to do with sunspots.
This is an area where IOT makes some sense. If you use an unlicensed frequency using the rule that allows use of such frequencies as long as power is very low, you risk some licensed user legally operating with much more power will stomp all over you, as is the case with the navy.
If you use IOT, that is much less likely. The frequencies used by WiFi are primarily allocated to other services, and so there is some risk that someone will legally stomp all over your WiFi, that risk is a lot less.
First, WiFi bands start at 2.4 GHz and go up from there. At those frequencies range is much more limited than it is at lower frequencies such as those typically used in current garage door openers. So even if someone is doing something high powered on those frequencies, it will likely only wipe out WiFi in a small area, rather than for many miles around.
Second, WiFi is widespread enough that those who might interfere probably use WiFi themselves, and so might be inclined to use some other frequencies available to them so as to not wipe out their own WiFi.
Similar arguments apply to cellular internet, but more strongly because in the case of cellular, I believe the cellular companies are the users who have priority for those frequencies.
This, an IOT garage door opener, connected on your home WiFi, that you can access via your cell phone from your car either via the cell phone using your home access point of over your cellular service, seems like it would possibly be the way to go nowadays (assuming you can secure the damn thing reasonably).
In the case specifically of garage door openers, though, I'd also consider doing it optically or ultrasonically, instead of via radio.
Huh.. he should be able to manually release the door from the inside (that's what the hanging handle [0] is for) and open/close it manually. Or hook up a wired keypad [1]
An interesting story regardless!
[0] http://precisiondoor.net/uploads/content/garage-door-opener-...
[1] https://www.amazon.com/Domino-Engineering-KEYLESS-ENTRY-SYST...
He will probably install a keypad at some point, although since he is a drummer I suggested he do something that listens for knocking on the door in some complex rhythm that would be easy for him but hard for a non-drummer.
I think he hasn't done anything yet because he's got some longer term plans for some home sensor and automation projects, if I recall correctly, and it could make more sense to do the alternate garage door opening interface as part of that instead of as an isolated project.
Or parent sees garage door open and decides to close it. Child is inside playing. Testing starts child is stuck.
Take your pick of scenarios. Neither require a car to be inside.
After a few hours trying to figure it out (not being RF folks) the security guards realised that the USS Kitty Hawk was in Fremantle harbour - and that this had happened last time the ship visited.
Somewhat unfriendly of that aircraft carrier to stomp all over civilian radio, but it might have been some interaction between the type of transmission tower (a large mast on the roof of the tallest building on the campus) and something they were doing (their radar?)
PD: My father is a amateur radio operator that on his good times won some prices talking with people on the other side of the world with a relative low power signal.
Which is a problem with the electronics in your phone not the charger. All Lithium-Ion batteries need to have an on board charge management IC to guard against overcharging. The power supply is just a dumb DC supply possibly with a way to request higher currents. In the end it is the responsibility of the phone electronics to limit current into the battery. Either they failed, were poorly designed, or the battery itself failed.
No, made in USA and UL approved.[1][2][3]
[1] http://www.arrl.org/news/view/amateur-radio-sleuthing-pins-d... [2] http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/sh... [3] http://ventextech.com/
> The troublesome transformer was not replaced, but the building owner agreed to turn off the sign should problems arise.
I thought they said it was a potential danger if folks cannot use their phones nearby, but then they dont take action to take down the sign. Are they waiting for an emergency to happen first?
I remember a story a while back where someone was driving around with a cellphone jammer since he was sick of people talking and driving. They caught him by noticing his commute pattern as connectivity dropped along the freeway he took each day.
[edit] Also another great example of hams helping the local community. Quite a few clubs run communication for remote events(think large bike races/etc) often free of charge and it always great to see technology used in this way.
Shame though, the number of wireless things is only going to grow. The amount of stuff I pick up just driving around on 2m is pretty incredible.
Also, I was surprised with the level of activity on APRS. Lots of tracking and weather data.
Do you have a source for this? FY2005 FCC spent $41m[1], in FY2009 they spent $46m[2], in FY2014 they spent $44m[3]. The worst you can say is that it has stagnated slightly, but then again, so have total FM/AM license holders and the associated license fees they pay.
[1] https://transition.fcc.gov/Reports/fcc2007budget.pdf
[2] https://apps.fcc.gov/edocs_public/attachmatch/DOC-290641A1.p...
[3] https://apps.fcc.gov/edocs_public/attachmatch/DOC-331817A1.p...
http://www.dailymail.co.uk/news/article-3488793/Pictured-Chi...
A few of these cases apparently.
"The interference source turned out to be a recently replaced neon sign switching-mode power supply, which was generating a substantial signal within the on-street parking area just across the sidewalk, between 8 and 40 feet from the sign."
Are key fobs are the canary in the coal mine of RF interference? There's a lot of stories of RF interference stopping them working in different places. Apparently, Ofcom dealt with 140 cases in 2010 alone: http://www.dailymail.co.uk/news/article-2057036/Trapped-driv...
If key fobs use receivers similar to the popular and dirt cheap "433 MHz RF Modules (ideal for Arduino)..." sold on eBay for <1$/piece: these are very, very crude and not selective to a particular frequency at all.
So, yes, they will stop working long before anything else (built a little more sophisticated) starts to show problems. Typically they are designed to be used in close proximity to your car, even if some people got used to operate it at considerable distance.
[1]: http://www.arrl.org/images/view/News/Evanston%20RFI-2.jpg
If a neon sign is generating RF over multiple bands, it may be the neon tube itself. If the tube has a loose connection, there's some arcing outside the tube, which generates broadband RF hash. Well-known problem for bands that play small venues.
http://ventextech.com/downloads/neon-power-supplies/indoor/V...
(note that the picture on the datasheet shows a VT 12030D-120, which is a different model)
Professional handheld spectrum analyzers are in the $3k-50k range from the likes of Keysight, Anritsu, etc.
It might seem like the poor man's approach, but plug a good Yagi antenna into that dongle and it becomes quite powerful.
Another approach seen on hackernews in the past had an omnidirectional antenna and used GPS tagging to make heatplots at different frequencies overlayed on a map. ref: http://www.tautology2.net/heatmap/ It uses the http://eartoearoak.com/software/rtlsdr-scanner software.
Looks like a somewhat portable device (MODEL 243): http://www.radarengineers.com/rfitvi.htm Although it's probably going to cost you $5-10k USD.
Pretty easy to hook up a RTL-SDR ($10) to a cheap Android tablet loaded with SDR Touch for simple surveying.
Google is very weird sometimes.
Note: I have never watched "My Little Pony", collected anything related, visited any My Little Pony fan sites, read any My Little Pony fan fiction (not even accidentally, via crossovers from fandoms whose fiction I do read), or done anything else to show any interest whatsoever in My Little Pony. Google has a ton of information about me with regards to things I might actually buy, so why the heck did they pick My Little Pony? (Heck, I'm pretty sure they have figure out that I have a ham license...surely they have something more relevant for me than My Little Pony).
For hunting a strong signal, the traditional tool is antenna with a deep null such a loop antenna. The reason for this is because the null at a point can be very deep relative to the average response-- e.g. maybe a small directional antenna has 10dB difference between the front and the side, but a small antenna engineered to have a deep null can easily have 40+ dB of isolation between a null and the side. To search for a signal using a null you aim until the signal goes away and you go in that direction. :)
And it's easy to construct antennas with only two (or one) null.
For a directional antenna like a yagi you have various reflections hitting the antennas sidelobes, making it harder to read.
When the rabbit-ears TV in the same room was turned on and tuned to the right frequency, you could hear the leakage from the drive; it sounded like lower-frequency modem chatter. Not entirely sure what part of the drive was leaking that much RF, but I don't think it was intended to work that way.
Your key-fob isn't opening a door. What's wrong? Dead battery? Door components not working?
AM radio: "I hear obvious noise in the broadcast no matter which way I turn the dial, and so does everyone else in their radio when they are in this vicinity."