A Complaint: Traffic Lights and Interference - Page 1
Forum section: electronics / rf-microwave

author: IdahoMan
author_rank: Regular Contributor
timestamp: December 18, 2017, 02:15:49 am
content: Anyone else getting this? I'd complain, but a lot of good that would do.When you are stopped at a traffic-light, and I don't know what part of the mechanism is doing it, the system pretty much cancels out the radio station you are listening to -FM or AM- with noise. It particularly happens when the light changes. It never used to be this way..

author: IanB
author_rank: Super Contributor
timestamp: December 18, 2017, 02:19:03 am
content: It's probably to make you concentrate on the light and not be distracted. It's likely intended to stop cell phone use, and the radio interference is collateral damage...(The other day I saw someone completely miss a green light because they were too busy using their phone. It went back to red before they paid attention and started moving.)

author: tec5c
author_rank: Frequent Contributor
timestamp: December 18, 2017, 02:42:53 am
content: Interesting. I have never had this happen to me here in Australia.If you don't mind me asking, which country are you from/had this happen in?

author: IanB
author_rank: Super Contributor
timestamp: December 18, 2017, 02:45:57 am
content: Quote from: tec5c on December 18, 2017, 02:42:53 amWell, unless someone has a weird sense of humor, I'd guess Idaho, USA?

author: tec5c
author_rank: Frequent Contributor
timestamp: December 18, 2017, 02:53:41 am
content: Quote from: IanB on December 18, 2017, 02:45:57 amYep, I didn't even see the OP's username

author: pieman103021
author_rank: Contributor
timestamp: December 18, 2017, 03:09:37 am
content: I remember an old story from /r/talesfromtechsupport about someone's wifi being interfered with by a traffic light. At the very least it is slightly relevant I guess.https://www.reddit.com/r/talesfromtechsupport/comments/2kg7gf/why_do_you_have_my_wifi_on_a_timer/

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: December 18, 2017, 06:40:44 am
content: I notice static on FM radio near intersections, but only the ones that have sensors that detect cars (optical ones, not inductive loop).

author: DimitriP
author_rank: Super Contributor
timestamp: December 18, 2017, 12:22:32 pm
content: It's interference from LED lights . Either from the nearest brightly lit business by the traffic light or the traffic lights themselves.I've noticed it near Starbucks, 7-11, Exxon gas stations and Del Taco drive throughs in Southern California.FM or XM radio station just dies as you approach, and returns as you leave.Progress!

author: David Hess
author_rank: Super Contributor
timestamp: December 18, 2017, 10:13:01 pm
content: It is RFI emitted from the poorly shielded switching driver circuit for the LED lamps. Apparently the FCC does not care if it is a municipality interfering with licensed radio services.

author: denverpilot
author_rank: Regular Contributor
timestamp: December 20, 2017, 06:28:09 am
content: Quote from: DimitriP on December 18, 2017, 12:22:32 pmMmmm. Mystery meat.A place that pairs tacos and french fries is just strange.The sad thing is, their fries are better than the fries at most of the burger joints.

author: Berni
author_rank: Super Contributor
timestamp: December 20, 2017, 06:35:27 am
content: That must be quite a bit of RF power leaking out to blank out the entire FM band. I would certainly bring a spectrum analyzer along if i found a intersection that did this.

author: David Hess
author_rank: Super Contributor
timestamp: December 20, 2017, 04:12:07 pm
content: Quote from: Berni on December 20, 2017, 06:35:27 amA directional antenna and tuned receiver is enough. An untuned receiver with a preselector might be enough.

author: DaJMasta
author_rank: Super Contributor
timestamp: December 20, 2017, 04:37:05 pm
content: Quote from: David Hess on December 18, 2017, 10:13:01 pmBut they should at least care about the supposedly certified bulbs the municipality is installing in their lights?I agree that the LED lights are a likely culprit, though, and that it's probably not narrowband interference.

author: AG6QR
author_rank: Frequent Contributor
timestamp: December 20, 2017, 08:23:25 pm
content: On a similar note, my car has a ham radio, and I often have it scanning several interesting frequencies. Among them is 121.5 Mhz AM, the standard emergency guard frequency for civil aircraft. There are two intersections near my home where I consistently hear a rather strong signal at this frequency. Just a carrier, with maybe a hint of powerline hum.I suspect a switching regulator, but I haven't tracked it down. Maybe someday I'll walk around the area with a handheld receiver to see what I can hear.

author: denverpilot
author_rank: Regular Contributor
timestamp: December 20, 2017, 09:03:52 pm
content: Quote from: David Hess on December 18, 2017, 10:13:01 pmI’ve not seen any municipalities who had any specific requirements to install anything “certified” to anything other than NEC and maybe FCC Part 15.Also never seen FCC go after a municipality for noisemakers unless they’re searching for a very specific interference complaint, to something licensed.And usually they’d accept the municipality just cleaning up that one emitter, they’d never go after them for buying hundreds of the noisy things.Really, they don’t care unless you can get a complaint from the broadcast station’s engineer about each and every traffic light that does it to their station.The only way you’d ever see enough political impetus to take broad scale action would be if a Public Safety organization complained that the municipality was jamming their comm, and considering that department would work for the same municipality, they’d just handle it internally.The main exception possibly being FAA or a FedGov LE system being hammered by a municipality’s poor choices/cheap choices of stop lights.Commercial broadcast versus stop lights? It’d be very hard to get FCC field offices involved in such a thing.

author: coppice
author_rank: Super Contributor
timestamp: December 20, 2017, 09:25:37 pm
content: Quote from: IanB on December 18, 2017, 02:45:57 amIts Mr Potatohead. He just thinks that's a cool tag to use.

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: December 21, 2017, 05:36:23 am
content: Quote from: David Hess on December 20, 2017, 04:12:07 pmYeah no - a spectrum analyzer would be bad enough. Pointing a directional antenna at a traffic light is bound to attract the attention of law enforcement. I can live with some buzz on my FM stations rather than getting shot.

author: ConKbot
author_rank: Super Contributor
timestamp: December 21, 2017, 07:25:50 am
content: Quote from: radar_macgyver on December 21, 2017, 05:36:23 amHi-vis safety vest, and maybe an amber light on a nearby vehicle (even if not on) and you'll be ignored

author: SeanB
author_rank: Super Contributor
timestamp: December 21, 2017, 09:37:31 am
content: Yes, wear a hi viz vest and you have a very effective cloaking device, you become almost invisible to people.

author: DimitriP
author_rank: Super Contributor
timestamp: December 26, 2017, 09:05:07 pm
content: Others have noticed too ....https://www.elektormagazine.com/news/led-rumpus