Close Calling LED Signs

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pb_lonny

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Tasmania
Around six weeks ago, I was driving along Wellington Street in Launceston when I stopped at the traffic lights near the Westbury Road turn off. I had my Uniden UBC126AT scanner with me, running in close call mode.

I got a close call hit on 162.500MHz which is the repeater output frequency for Boral on Mt Arthur. This was "open carrier". I thought this was a little strange as I was over 22km from where this repeater is located (see the map below)



I thought it might have been a driver using this in simplex mode, but I have never heard them do this before. A couple of weeks later I was again driving in this area and again had a close call hit on this same frequency, 162.500MHz. This I found very strange.

Last week I was driving past Queechy High School when I again got a close call hit on 162.500MHz, this really puzzled me. I parked my car and got out, by following the signal strength I was able to locate the source of the signal to this LED sign.



On my drive home I drove along Wellington Street and got another close call hit on this frequency, looking around I spotted this sign.



It seems that these LED signs radiate a open carrier signal on 162.500MHz. Range is up to 25 metres.
 

kevinparrish

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New York City
RFI / Unintentional Radiators / LED Signs

Paul,

The conditions you describe unfortunately have become widespread in recent years with advancing LED technology being used in signs, video walls, studio & theatrical lighting, home lighting, security equipment, etc.

Unfortunately many poorly manufactured LED equipped devices have become common sources of RFI acting as "unintentional radiators" sometimes with significant & harmful impact.

One of the most severe cases of LED interference that I know of plagued a small town fire department which had just re-built and modernized it's firehouse... In an effort to adopt "green technologies" the modernized firehouse was fitted with LED lighting.

Problems arose almost immediately after re-occupancy where the departments 2-way radios in and around the firehouse had poor reception, station alerting dispatch failures and firefighter pagers would not decode.

After an exhaustive investigation by Electrical Engineers, RF Engineers & installing contractors, it was determined that the LED lighting (poorly manufactured) was generating RFI on the frequency used by the fire department.

I can also tell you from personal experience working within the television remote-broadcast production industry that various LED equipment which is used in areas where television broadcast, studio production, theatrical & music venues, sports stadiums, etc increasingly experience RFI.

Wireless Microphones, IEMs, wireless production intercom systems operating in the VHF & UHF spectrum increasingly experience interference from LEDs.

Thanks for sharing your observations.

Kevin Parrish
 

12dbsinad

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Mar 15, 2010
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After an exhaustive investigation by Electrical Engineers, RF Engineers & installing contractors, it was determined that the LED lighting (poorly manufactured) was generating RFI on the frequency used by the fire department.
I relate to this, except in our dept it was the heat pumps from the geothermal heating/cooling system. There was about 15 of them and would render a portable or pager (or even vehicle mounted radios parked near the building) useless. Luckily the company was able to fix this problem, replaced the pumps and the problem went away.

I've also dealt with LED signs on city transit buses. The signs would completely whip out the VHF 2 way mobile radio in the bus due to radiating RFI. It for sure is becoming a increasing problem.
 
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