10 ms·

Amateur Radio Sleuthing Pins Down Source of Strange RF Interference

196 points by xoa 10y ago

vvanders 10y ago
Kinda surprised the FCC/Wireless providers didn't help. Usually when there's 911 connectivity issues they take it pretty seriously. 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.
- mmagin 10y ago
  Funding for the enforcement branch of the FCC has been seriously cut in recent years.
  - vvanders 10y ago
    Ah, that would help explain it. 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.
    - wyager 10y ago
      I just drove 3000 miles listening on 144.39, 146.46, 146.52, 446.0, and all CB frequencies. There's a fair amount of garbage on the calling frequencies, but CB is really bad. I get horrible noise driving past power lines especially. Also, I was surprised with the level of activity on APRS. Lots of tracking and weather data.
  - kawfey 10y ago
    But to their credit, they're planning on doing a comprehensive study of the RF noise floor. However, they actually have no idea how to do this, and are calling on amateur radio ops and the general public for advice. http://transition.fcc.gov/Daily_Releases/Daily_Business/2016/db0615/DA-16-676A1.pdf http://transition.fcc.gov/Daily_Releases/Daily_Business/2016...
  - akira2501 10y ago
    > Funding for the enforcement branch of the FCC has been seriously cut in recent years. 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 https://transition.fcc.gov/Reports/fcc2007budget.pdf [2] https://apps.fcc.gov/edocs_public/attachmatch/DOC-290641A1.pdf https://apps.fcc.gov/edocs_public/attachmatch/DOC-290641A1.p... [3] https://apps.fcc.gov/edocs_public/attachmatch/DOC-331817A1.pdf https://apps.fcc.gov/edocs_public/attachmatch/DOC-331817A1.p...
- Jtsummers 10y ago
  http://www.pcworld.com/article/2149501/florida-commuters-illegal-jammer-blocked-more-than-cell-talkers.html http://www.pcworld.com/article/2149501/florida-commuters-ill... http://www.dailymail.co.uk/news/article-3488793/Pictured-Chicago-man-using-signal-jammer-stop-chatty-cell-phone-talkers-commute-home.html http://www.dailymail.co.uk/news/article-3488793/Pictured-Chi... A few of these cases apparently.
okket 10y ago
TL;DR "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."
xoa 10y ago
If you scroll down a bit, you'll see that sure enough this involved a switched-mode power supply, /probably some very cheap no-name/ [nope, missed that they included pictures of it]. Even though they're supposed to be at least minimally regulated under Title 47 part 15(B), in practice they're often a plague upon RF and as the article states sometimes the FCC has trouble mustering the energy for small spot trouble. While I feel more generous towards the FCC then some of the commentary I've seen on this, in that I don't think they've been remotely allocated the resources they should have to deal with this kind of small hotspot popping up since historically it was less an emergency matter, it's an issue (and a bit more surprising when it's a request from law enforcement, even if local). 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.
- Florin_Andrei 10y ago
  As someone who has designed and built switching power supplies, the article brought back funny memories. 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.
devy 10y ago
There are tons of cheap electronics (including but not limited to switching power supplies) that are not properly EMI shielded or even not shielded at all. It would be great to have a portable device that can detect and locate the EMI/RFIs. (Perhaps there are already some on kickstarter?)
- cozzyd 10y ago
  Raspberry pi + RTL-SDR + screen + battery?
  - devy 10y ago
    Not for the faint of heart :) Is there a off the shelf product ?
    - dbcurtis 10y ago
      Spectrum analyzer and appropriate antenna.
    - deleted 10y ago
      [deleted]
    - cdawzrd 10y ago
      RF Explorer is a "budget" option at around $300-400: http://rfexplorer.com/models/ http://rfexplorer.com/models/ Professional handheld spectrum analyzers are in the $3k-50k range from the likes of Keysight, Anritsu, etc.
      - tegansnyder 10y ago
        Many vendors will also rent out them by the day. There used to be a company in Denver that did back in my WISP days.
    - Florin_Andrei 10y ago
      Plug a cheap SDR dongle into your laptop and install some free software SDR app. http://www.rtl-sdr.com/ http://www.rtl-sdr.com/ It might seem like the poor man's approach, but plug a good Yagi antenna into that dongle and it becomes quite powerful.
devy 10y ago
So the neon light switching power supply's label with serial number and manufacturer were pictured.[1] And it was UL certified but with no FCC label. Will the manufacturer get a fine if someone files a complain? I am curious. [1]: http://www.arrl.org/images/view/News/Evanston%20RFI-2.jpg http://www.arrl.org/images/view/News/Evanston%20RFI-2.jpg
- Animats 10y ago
  Power supplies don't require FCC approval, just a declaration of conformity. 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.
- twic 10y ago
  FWIW, it's one of these, a Ventex VT 12030-120: http://ventextech.com/downloads/neon-power-supplies/indoor/VT12030-120.pdf 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)
ekianjo 10y ago
I find the conclusion a bit strange: > 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?
- jeff_vader 10y ago
  It was found by a radio amateur, not FCC. So the only way to deal with this is asking nicely and expecting cooperation.
  - rmason 10y ago
    Because the FCC refuses to intervene the firm that installed the transformer will probably continue selling that exact same solution, thus spreading interference all over Chicago.
  - nullc 10y ago
    My experience is that if you offer to fix it at your own expense, most people will just happily let you.
  - PhasmaFelis 10y ago
    Found by a radio amateur at the request of local police! It's a clear public safety issue, and clearly illegal. Why didn't the police tell him to turn it off?
    - morganvachon 10y ago
      Coming from a law enforcement background, my guess is that there is no local statute that deals with it. It's a violation on the federal level, and the feds already declined to address it, so all the local cops can do is ask the business to replace their faulty equipment. Unless they have a local ordinance that specifically addresses the problem, their hands are tied.
    - 10y ago
TazeTSchnitzel 10y ago
Odd the FCC didn't intervene. Here in the UK, Ofcom (our FCC equivalent) has done so in some similar situations (http://consumers.ofcom.org.uk/news/ghost-busting-in-windermere/ http://consumers.ofcom.org.uk/news/ghost-busting-in-winderme..., http://www.bbc.co.uk/news/uk-england-hampshire-15306994 http://www.bbc.co.uk/news/uk-england-hampshire-15306994). 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-drive-TV-How-set-boxes-interfering-car-key-fobs.html http://www.dailymail.co.uk/news/article-2057036/Trapped-driv...
- matt_wulfeck 10y ago
  The FCC may intervene, we unfortunately don't know the rest of the story. It ends in an amateur radio enthusiasts speaking to the sign owner and getting an underwhelming response.
- cnvogel 10y ago
  > Are key fobs are the canary in the coal mine of RF interference? 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.
basicplus2 10y ago
These sorts of issues were found and solved quickly when everyone was listening mostly to AM radio as everyone was effected.
- kawfey 10y ago
  The article mentions key-fobs and cell phones were affected.
  - kazinator 10y ago
    But you don't hear a problem in those technologies the way you do in AM radio. They just appear not to be working. 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."
  - basicplus2 10y ago
    one could also use a radio's aerial to find the direction of the interference, so by walking around one could hone in as the magnitude of the interference increased, pretty useful as anyone could find the source no matter what their expertise.
nickhalfasleep 10y ago
The general quality of Neon and Fluorescent drivers will continue to nosedive as both are replaced by more efficient technologies. Currently the factories are being run out to wring the last bit of profit from these technologies as they are replaced by LED's and their switched mode DC supplies of lower voltage and frequency.
mrestko 10y ago
I live right by here and had actually noticed an odd sign in the window of that shop referencing some problem with car key fobs and that "the police are aware". Maybe I'll stop by and take a picture tomorrow if I have time.

196 points by xoa 10y ago

Kinda surprised the FCC/Wireless providers didn't help. Usually when there's 911 connectivity issues they take it pretty seriously. 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.

mmagin 10y ago
Funding for the enforcement branch of the FCC has been seriously cut in recent years.
- vvanders 10y ago
  Ah, that would help explain it. 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.
  - wyager 10y ago
    I just drove 3000 miles listening on 144.39, 146.46, 146.52, 446.0, and all CB frequencies. There's a fair amount of garbage on the calling frequencies, but CB is really bad. I get horrible noise driving past power lines especially. Also, I was surprised with the level of activity on APRS. Lots of tracking and weather data.
- kawfey 10y ago
  But to their credit, they're planning on doing a comprehensive study of the RF noise floor. However, they actually have no idea how to do this, and are calling on amateur radio ops and the general public for advice. http://transition.fcc.gov/Daily_Releases/Daily_Business/2016/db0615/DA-16-676A1.pdf http://transition.fcc.gov/Daily_Releases/Daily_Business/2016...
- akira2501 10y ago
  > Funding for the enforcement branch of the FCC has been seriously cut in recent years. 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 https://transition.fcc.gov/Reports/fcc2007budget.pdf [2] https://apps.fcc.gov/edocs_public/attachmatch/DOC-290641A1.pdf https://apps.fcc.gov/edocs_public/attachmatch/DOC-290641A1.p... [3] https://apps.fcc.gov/edocs_public/attachmatch/DOC-331817A1.pdf https://apps.fcc.gov/edocs_public/attachmatch/DOC-331817A1.p...
Jtsummers 10y ago
http://www.pcworld.com/article/2149501/florida-commuters-illegal-jammer-blocked-more-than-cell-talkers.html http://www.pcworld.com/article/2149501/florida-commuters-ill... http://www.dailymail.co.uk/news/article-3488793/Pictured-Chicago-man-using-signal-jammer-stop-chatty-cell-phone-talkers-commute-home.html http://www.dailymail.co.uk/news/article-3488793/Pictured-Chi... A few of these cases apparently.

okket 10y ago

TL;DR "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."

xoa 10y ago

If you scroll down a bit, you'll see that sure enough this involved a switched-mode power supply, /probably some very cheap no-name/ [nope, missed that they included pictures of it]. Even though they're supposed to be at least minimally regulated under Title 47 part 15(B), in practice they're often a plague upon RF and as the article states sometimes the FCC has trouble mustering the energy for small spot trouble. While I feel more generous towards the FCC then some of the commentary I've seen on this, in that I don't think they've been remotely allocated the resources they should have to deal with this kind of small hotspot popping up since historically it was less an emergency matter, it's an issue (and a bit more surprising when it's a request from law enforcement, even if local). 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.

Florin_Andrei 10y ago
As someone who has designed and built switching power supplies, the article brought back funny memories. 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.

devy 10y ago

There are tons of cheap electronics (including but not limited to switching power supplies) that are not properly EMI shielded or even not shielded at all. It would be great to have a portable device that can detect and locate the EMI/RFIs. (Perhaps there are already some on kickstarter?)

cozzyd 10y ago
Raspberry pi + RTL-SDR + screen + battery?
- devy 10y ago
  Not for the faint of heart :) Is there a off the shelf product ?
  - dbcurtis 10y ago
    Spectrum analyzer and appropriate antenna.
  - deleted 10y ago
    [deleted]
  - cdawzrd 10y ago
    RF Explorer is a "budget" option at around $300-400: http://rfexplorer.com/models/ http://rfexplorer.com/models/ Professional handheld spectrum analyzers are in the $3k-50k range from the likes of Keysight, Anritsu, etc.
    - tegansnyder 10y ago
      Many vendors will also rent out them by the day. There used to be a company in Denver that did back in my WISP days.
  - Florin_Andrei 10y ago
    Plug a cheap SDR dongle into your laptop and install some free software SDR app. http://www.rtl-sdr.com/ http://www.rtl-sdr.com/ It might seem like the poor man's approach, but plug a good Yagi antenna into that dongle and it becomes quite powerful.

devy 10y ago

So the neon light switching power supply's label with serial number and manufacturer were pictured.[1] And it was UL certified but with no FCC label. Will the manufacturer get a fine if someone files a complain? I am curious. [1]: http://www.arrl.org/images/view/News/Evanston%20RFI-2.jpg http://www.arrl.org/images/view/News/Evanston%20RFI-2.jpg

Animats 10y ago
Power supplies don't require FCC approval, just a declaration of conformity. 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.
twic 10y ago
FWIW, it's one of these, a Ventex VT 12030-120: http://ventextech.com/downloads/neon-power-supplies/indoor/VT12030-120.pdf 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)

ekianjo 10y ago

I find the conclusion a bit strange: > 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?

jeff_vader 10y ago
It was found by a radio amateur, not FCC. So the only way to deal with this is asking nicely and expecting cooperation.
- rmason 10y ago
  Because the FCC refuses to intervene the firm that installed the transformer will probably continue selling that exact same solution, thus spreading interference all over Chicago.
- nullc 10y ago
  My experience is that if you offer to fix it at your own expense, most people will just happily let you.
- PhasmaFelis 10y ago
  Found by a radio amateur at the request of local police! It's a clear public safety issue, and clearly illegal. Why didn't the police tell him to turn it off?
  - morganvachon 10y ago
    Coming from a law enforcement background, my guess is that there is no local statute that deals with it. It's a violation on the federal level, and the feds already declined to address it, so all the local cops can do is ask the business to replace their faulty equipment. Unless they have a local ordinance that specifically addresses the problem, their hands are tied.
  - 10y ago

TazeTSchnitzel 10y ago

Odd the FCC didn't intervene. Here in the UK, Ofcom (our FCC equivalent) has done so in some similar situations (http://consumers.ofcom.org.uk/news/ghost-busting-in-windermere/ http://consumers.ofcom.org.uk/news/ghost-busting-in-winderme..., http://www.bbc.co.uk/news/uk-england-hampshire-15306994 http://www.bbc.co.uk/news/uk-england-hampshire-15306994). 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-drive-TV-How-set-boxes-interfering-car-key-fobs.html http://www.dailymail.co.uk/news/article-2057036/Trapped-driv...

matt_wulfeck 10y ago
The FCC may intervene, we unfortunately don't know the rest of the story. It ends in an amateur radio enthusiasts speaking to the sign owner and getting an underwhelming response.
cnvogel 10y ago
> Are key fobs are the canary in the coal mine of RF interference? 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.

basicplus2 10y ago

These sorts of issues were found and solved quickly when everyone was listening mostly to AM radio as everyone was effected.

kawfey 10y ago
The article mentions key-fobs and cell phones were affected.
- kazinator 10y ago
  But you don't hear a problem in those technologies the way you do in AM radio. They just appear not to be working. 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."
- basicplus2 10y ago
  one could also use a radio's aerial to find the direction of the interference, so by walking around one could hone in as the magnitude of the interference increased, pretty useful as anyone could find the source no matter what their expertise.

nickhalfasleep 10y ago

The general quality of Neon and Fluorescent drivers will continue to nosedive as both are replaced by more efficient technologies. Currently the factories are being run out to wring the last bit of profit from these technologies as they are replaced by LED's and their switched mode DC supplies of lower voltage and frequency.

mrestko 10y ago

I live right by here and had actually noticed an odd sign in the window of that shop referencing some problem with car key fobs and that "the police are aware". Maybe I'll stop by and take a picture tomorrow if I have time.