[RFI] Light fixtures

Hare, Ed W1RFI w1rfi at arrl.org
Fri Jul 1 15:36:11 EDT 2016

From antenna modeling I have done, the decay of noise with distance depends on how the noise is being coupled on to conductors and how imbalanced those conductors are.

If noise is coupled onto wires in the common mode, noise will generally decay at a power rate of the inverse of the distance squared.

If noise is coupled onto well-balanced wiring in the differential mode, radiation will generally decay at much higher rates, as high as 1/D^3.

For differential-mode coupling onto poorly balanced wiring, the decay rate is somewhere between those two extremes.

Interestingly, the balance of wiring can vary as loads are changed.  One obvious change is what happens when a light fixture is switched. When the switch is closed, the balance of the electrical wiring at RF is fair, and most power is conducted to the load.  When the switch is opened, it opens only the hot lead, effectively adding a short piece of end-fed wire to the electrical-wiring transmission line, and emissions will increase by 10 dB or more.

-----Original Message-----
From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of Dave Cole
Sent: Wednesday, June 29, 2016 6:59 PM
To: rfi at contesting.com
Subject: Re: [RFI] Light fixtures

On Wed, 2016-06-29 at 20:38 +0000, Hare, Ed  W1RFI wrote:
> Also, where do we draw the line?  There is a major difference in kind 
> between a ham that buys a device, installs it in his or her own home 
> and has S9 noise to an antenna close to the house, and S9 from a 
> device in a neighbor's home.

I never even thought about that...  I have a light I put up with in the Laundry Room, it is LED, noisy, (S9), and about 30 feet from one antenna, and maybe 100 feet from the other...  

I only hear it on the closer antenna...  Not even detectable on the far antenna.  

73's, and thanks,
Dave (NK7Z)
For software/hardware reviews see:

RFI mailing list
RFI at contesting.com

More information about the RFI mailing list