How traffic lights affect my iPod

[EricNoah]

I drive the same route home from work every day. I have my iPod attached to a "car kit" that broadcasts an FM signal to my car stereo. Every time I approach one particular intersection to stop (because I always hit a red light there), I get a big wash of static through my stereo. What I have noticed, though, is that the second the light at that intersection changes from red to green, the static instantly stops. It's freaking me out, man...

Anything weird happening to you?

 

[HeavenShallBurn]

It's probably an improperly grounded circuit dumping into the metal shell. The issue isn't in the iPod it's in the car kit. Due to FCC regulation they have to meet standards for not interfering with anybody else that also cripple them with regard to accepting interference from everything else. If you've ever lived near a major naval base you'll remember noticing that many things get their reception totally hashed by the various pieces of military sensors and EW gear being operated. This is like a low powered version of that caused by design constraints that force it to accept any interference so that it doesn't cause interference in other receivers.

 

[EricNoah]

Thanks for the explanation. Though I have to say you have ruined my sense of wonder. Wouldn't it be better to live in a world where weird stuff happens and we just don't know why?

 

[GeorgeFields]

Wouldn't it be better to live in a world where weird stuff happens and we just don't know why?

Have you never encountered a species we call women? They do/cause weird stuff all the time.

 

[Richards]

I listen to a radio station from a city about an hour's drive away (it's the only one that plays "Bob and Tom" in the morning), and proximity to traffic lights always wreaks havoc with the reception. It's really irritating pulling up to a red light and having Bob and Tom fade out and a local country and western station bleed in.

Johnathan

 

[EricNoah]

It's really irritating pulling up to a red light and having Bob and Tom fade out and a local country and western station bleed in.

See, now, that's obviously the work of a cowboy ghost whose spirit haunts that particular intersection. Miracles do happen!

 

[EricNoah]

Have you never encountered a species we call women? They do/cause weird stuff all the time.

Been married nearly 14 years. And yes, they sure do! They also restore my Sense of Wonder (TM).

 

[Morrus]

Traffic lights may not affect my iPod, but they sure as hell affect my temper!

*I apparently live in the city with the highest density of traffic lights in the world. Drving here is like limping from one set of lights to the next, continually. Sometimes it takes me 45 minutes to drive the two miles into town.

 

[Umbran]

Due to FCC regulation they have to meet standards for not interfering with anybody else that also cripple them with regard to accepting interference from everything else.

I don't think that's the real base cause. Traffic lights are not supposed to put out appreciable radio noise, period. Note how all the other traffic lights don't cause any problem? That's because they are operating properly. This one light, in a particular state, probably has a loose connection or minor short that is causing some electrical arcing - and thus radio noise.

A simple check - turn on the car stereo to the station you'd use to receive the iPod. But, don't turn on the iPod. Drive by that light - if you still hear the static, the issue is the light, and the iPod has nothing to do with it.

 

[trancejeremy]

Traffic lights have sensors in them to see how many cars are stopped when the light is red. They used to be sensors under the road (they detect metal), but now we're starting to see some work some other way (I guess more like automatic doors in like stores, since the old type don't work well with bikes and such).

My guess is that it's the latter sort that are causing the interference. The next time you go by, see if there is some sort of sensor device on the light.