1. Does the inverse square-law apply to all devices that emit RFI where
the RF energy emanating from the device falls off exponentially with
distance?
For small sources, yes. The square-law applies to a point source. For the
square law to apply, you must be in the far field of the
generator/radiator. Far field is usually defined as:
2
Far Field Distance = 2D / LAMBDA
where D = largest dimension of emitter
LAMBDA = wavelength of the measurement frequency
(in same units as D and far field distance)
2. Is it common for power and other utility cables to carry and radiate RFI
from a device located in a neighbors home over long distances before being
attenuated?
This is why its so difficult to isolate arcing or corona using RF
emissioins and walking the length of the power line. Generally sources
inside a neighbors home don't go much further than the house. However, if
they are strong sources, they will. The reason we do conducted emissions
in regulatory testing is that lengths of conductors in housing are good
radiators of RF energy below 30 MHz. So, we measure conducted emissions
that become radiated emissions once they couple onto the house wiring.
Conducted emissions are measured and regulated from 150 kHz to 30 MHz for
most home electronic equipment. The generator is usually not a good
radiator due to small size wrt wavelength.
Dave - WØLEV
On Mon, Jun 11, 2018 at 9:36 PM, Tony <dxdx@optonline.net> wrote:
> All:
>
> These might be a silly questions, but given how complex this subject is, I
> thought I'd ask anyway.
>
> 1. Does the inverse square-law apply to all devices that emit RFI where
> the RF energy emanating from the device falls off exponentially with
> distance?
>
> 2. Is it common for power and other utility cables to carry and radiate
> RFI from a device located in a neighbors home over long distances before
> being attenuated?
>
> In a case like that, I would imagine locating the source of interference
> would be nearly impossible with all that RFI being radiated by utility
> lines.
>
> 73, Tony -K2MO
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>
--
*Dave - WØLEV*
*Just Let Darwin Work*
*Just Think*
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