[RFI] LED lighting

Tue Jul 28 23:54:35 EDT 2015

Roger, not sure what you were using for a detection system but most 
double walled shielded enclosures (i.e., Lindgren etc) provide around 
120-140 dB S.E. to E-fields.  Less as they got older.  If you had a 10W 
RF source outside of the enclosure (call it +40 dBm) you would have 
roughly a -100 dBm signal inside, which even a mediocre detection system 
or S.A. could easily detect. Like yourself, I used to live inside 
various shielded enclosures and buildings from different manufactures 
for a living as I was a tempest engineer for over 30 years.

Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 7/28/2015 10:35 PM, Roger (K8RI) wrote:
> I worked in a double walled screen room quite often. All leads were 
> filtered. The door used a cam to finish closing.  A 10W signal outside 
> the door was not detectable inside.  You could watch the signal go 
> down as the cam was closed.  Well before the cam was closed the signal 
> was gone.  I can't imagine needing more than a standard screen room 
> for measuring RFI from LEDs and their switching supplies.
>
> In my case the screen room was for isolation of very sensitive 
> measurements in an area with a lot of RF. OTOH  I did a lot of RF 
> monitoring to make sure those 200 KW and up, induction heating units 
> could not be heard.
>
> 73
>
> Roger (K8RI)
>
> On 7/27/2015 11:25 AM, Hare, Ed W1RFI wrote:
>> Actually, we don't.  We have the screen room to do receiver and 
>> transmitter testing, and a room set up in compliance with ANSI C63.4 
>> to do conducted-emission measurements, but not an anechoic chamber. 
>> Outdoor testing should suffice, being a good approximation to a 
>> calibrated open-area test site.  If we find devices a few dB above 
>> the limits, we don't file complaints, but the things we have found to 
>> be bad have been WAY above the limits, so close enough is close enough.
>>
>>
>> Ed Hare, W1RFI
>> ARRL Laboratory Manager
>> 225 Main St.
>> Newington, CT 06111
>> Tel: (860) 594-0318
>> Fax: (860) 594-0259
>> Email: W1RFI at arrl.org
>> Member: IEEE Connecticut Section
>> Member: IEEE EMC Society, Board of Directors
>> Member: IEEE EMC Society Standards Development and Education Committee
>> Primary representative:  ANSI ASC C63 EMC Committee, Vice Chair 
>> Subcommittee 5 (Immunity)
>> Member: QRP Amateur Radio Club International, Board of Directors
>>
>>
>>
>> From: David Robbins [mailto:k1ttt at verizon.net]
>> Sent: Monday, July 27, 2015 11:19 AM
>> To: Hare, Ed W1RFI
>> Cc: rfi at contesting.com
>> Subject: Re: Re: [RFI] LED lighting
>>
>> what?  you don't have an anechoic shielded chamber to do that kind of 
>> stuff???
>>
>>
>> Jul 27, 2015 11:05:16 AM, w1rfi at arrl.org<mailto:w1rfi at arrl.org> wrote:
>> I bought one multi-LED bulb that came from China. It was dead quiet. 
>> My guess is that it simply put the LEDs in series and connected them 
>> to the line. Not all of them will have a switcher in them.
>>
>> ARRL tested a number and found them to be below the conducted 
>> emissions limits. I want to test them above 30 MHz too, for radiated 
>> emissions, though we'd need to set up outdoors to prevent scatters 
>> from throwing off the readings.
>>
>>
>> Ed Hare, W1RFI
>> ARRL Laboratory Manager
>> 225 Main St.
>> Newington, CT 06111
>> Tel: (860) 594-0318
>> Fax: (860) 594-0259
>> Email: W1RFI at arrl.org<mailto:W1RFI at arrl.org>
>> Member: IEEE Connecticut Section
>> Member: IEEE EMC Society, Board of Directors
>> Member: IEEE EMC Society Standards Development and Education Committee
>> Primary representative: ANSI ASC C63 EMC Committee, Vice Chair 
>> Subcommittee 5 (Immunity)
>> Member: QRP Amateur Radio Club International, Board of Directors
>>
>>
>>
>> -----Original Message-----
>> From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of David Robbins
>> Sent: Sunday, July 26, 2015 11:37 AM
>> To: 'Phil Snyder'; rfi at contesting.com<mailto:rfi at contesting.com>
>> Subject: Re: [RFI] LED lighting
>>
>> They could just be led bulbs in a standard 120v socket also... in 
>> those there is a switching supply in the base of each bulb.
>>
>> David Robbins K1TTT
>> e-mail: mailto:k1ttt at arrl.net
>> web: http://wiki.k1ttt.net
>> AR-Cluster node: 145.69MHz or telnet://k1ttt.net
>>
>>
>> -----Original Message-----
>> From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of Phil Snyder
>> Sent: Sunday, July 26, 2015 14:51
>> To: rfi at contesting.com<mailto:rfi at contesting.com>
>> Subject: [RFI] LED lighting
>>
>> Well after a 4 year period the local electric company found the 
>> offending lightning arrester and voila no more noise! Unfortunately, 
>> the neighbor behind me just remodeled the outside of their house and 
>> in the process added about 6 LED lighting fixtures in the soffit 
>> across the front and after a few days of watching and listening it 
>> appears that they are causing way more RFI then the faulty arrester 
>> ever did.
>>
>> I am hoping to learn a little more here before approaching them to 
>> make sure all my facts are straight. I am assuming that there is a 
>> switching power supply running the lights and that the power is cut 
>> to the supply when they are not on since the noise is gone when they 
>> are off. Is it possible to try and suppress the noise on the leads 
>> coming out of the power supply? Does he need to contact the 
>> manufacturer to replace the supply? Unfortunately they are mounted 
>> into the soffit like a can type light you would have inside your 
>> house and I hope the power supply is accessible.
>>
>> Thanks
>> Phil
>> N9LAH
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