[RFI] Traffic Light LED's

Skip Cameron scameron@austin.rr.com
Mon, 14 Oct 2002 12:07:07 -0500

Traffic Light LED's are coming to Austin, Texas!
Please post any hints other than those posted by K0IL and K4CIA (below) on how to
detect and eliminate RFI and I will pass it to our City traffic engineers.
I could not find any references on the ARRL web site RFI Index at
Bright ideas will let city's traffic signals last longer, cost less

By Kelly Daniel
Monday, October 14, 2002

Traffic lights are going to burn brighter pretty soon.

The City of Austin is chipping away at a $5 million plan to
install new types of bulbs at its 770 intersections. The new
technology uses less electricity overall and longer lasting
equipment, so the city hopes to save on both electric and
maintenance bills.

The bulbs, called light emitting diodes, are expected to drop
the city's annual energy use by 2.8 percent, saving $1.7
million a year on the electric bill, the city staff has said in
memos and briefings.
Subject: RE: [RFI] LED Traffic Light RFI
Date: Fri, 27 Sep 200

We started having problems with these LED lights in Omaha, NE last year,
and the traffic engineer laughed at first when I called to let them know about it
since I only knew about QRM to/from VHF
ham bands (and possibly our company's pagers on VHF as well).  We also had reports
from hams that they could control the
left turn signal using 2 meters!  No need to wait to turn, just key up and GO!

Then when the city's contractor for radio systems (local mobilecom shop) called to
tell them about it, they got real
serious since they were getting it on the fire & sheriff VHF freqs as well.

They found that certain mfr's switching power supplies are noise junk generating
broadband noise.  I don't remember the
mfr's name, but only one of them was bad I think so they switched out to the other
brand.  If you need specific names, I
can call our traffic engr here and ask.

Ed Edwards, Communications Engineer
2-Way & Paging Systems
Omaha Public Power District
Phone: (402) 552-5425
From: "William G. McDowell" <k4cia@mindspring.com>
Date: Fri, 4 Oct 2002 11:51:45 -0400
Subject: [RFI] Stoplight LED problem resolved

Happy ending to the story..turns out the green LED 12" fixtures were the
problem.  Precision Solar Controls Model 2035, to be exact.  Changed all on
one direction (east/west) and no noise.  Changed the remaining four on the
north/south lanes and still completely silent.