I live in San Diego, and we have these LED sigs all over the place; I
listen to AM a lot, and have detected no problems...and I put on 25,000
miles in a year in this environment, too, at all hours of the day and
night. Listen to KGO 810 at night too, 500 miles off.
Perhaps this is an indicator that it's _manufacturer-specific_? Someone
saving .13 per unit so the shareholders can get an extra .05 per share
"No-one spends more than the stingy engineer."
As a side note, many years (1990) ago those HV Neon "WALK/DON'T WALK" signs
went up, and created a 1000 foot radius howl on HF like you would not
believe. SDG&E in conjunction with the Street Maint. Dept. came right out
and fixed the problem with a simple filter/ground screen combo.
Some utilities are better than others.
Just my .02 .
At 12:43 PM 12/14/2007, you wrote:
>I live in the country with no traffic lights nearby, so this isn't a
>problem with me, but I keep hearing about RFI generated by the new l.e.d.
>traffic signals. Apparently, the noise is due to a switching power supply
>used to feed the lights, and the power line leading to the unit acting as
>Someone I know has one of those LED stoplights about 100 yards from his
>house. It wipes out the AM BC Band when you are in the car sitting at the
>light, and he says he can hear it up and down the band and weaker signals
>on 75 and 160 at night are GONE. He figures there isn't anything he can
>do about it at all, except move.
>I wonder if anyone has checked to see if those led traffic lights have
>been certified to meet Part 15 standards. Since they are becoming
>ubiquitous in almost every city and town and there are traffic lights
>literally everywhere, this could grow into a major rfi problem that rivals
>or surpasses BPL.
>Perhaps the AM broadcast industry would get involved, since this stands to
>hurt them severely. Over 90% of the prime time radio audience during
>morning and evening hours is made up of commuters, and most listeners will
>simply switch over to FM if they start getting interference at every
>traffic light. This could become the death knell for AM broadcast radio,
>with its odds for survival already marginal at best. Those switching power
>supplies could easily be fixed with a little filtering. I'm not even sure
>that shielding would be required.
>This is a problem that needs to be addressed NOW before the overwhelming
>majority of traffic signals nationwide are replaced with noisy l.e.d. ones
>and the problem becomes impossible to remedy.
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