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@contesting.com] On Behalf Of Dave Cole
Sent: Wednesday, June 29, 2016 6:59 PM
To: rfi@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:
http://www.nk7z.net
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