Fortunately, Cortland , all of the power line noise sources I have had the
pleasure to locate exhibited radiation from the vertical ground wire.
Effectively, this represents a T-top loaded type vertical antenna with a
pronounced vertical signal and signature.
IT HAS been instructive, though TO NOTE the characteristics between signal
bearings between say, two different disparate freqs like 400 kHz and 1900 kHz
versus 3.5 MHz
I have found, during field work, the highest freq's bearing is THE correct one
indicating the correct source when outside say 500 feet distance. For 400 kHz
this can be nearfield of the vert ground wire, as well as saome radiation from
a long horz line run.
de Jim WB5WPA
From: Cortland Richmond <ka5s@earthlink.net>
To: rfi@contesting.com
Sent: Wednesday, June 13, 2018 9:11 AM
Subject: Re: [RFI] Inverse Square Law and RFI
This is an issue we lost in the BPL fight; when radiating conductors are
long in wavelength, the transformation from near to far fields occurs
at greater distance than would be expected of a point source. Ignoring
radiator size (in wavelengths)-- part of the equation -- can result in
substantially lower calculated interference potential from such sources.
For 4 MHz
(https://www.everythingrf.com/rf-calculators/antenna-near-field-distance-calculator
) and a 1000 meter radiating conductor:
*
Wavelength
74.9481145m
*
Reactive Near Field Distance
2264.70340834m
*
Radiating Near Field Distance
26685.12761585m
*
Far Field (Greater than this distance)
26685.12761585m
Assuming a "point source" (ONE meter radiator)...
*
Reactive Near Field Distance
0.07161621m
*
Radiating Near Field Distance
0.02668513m
*
Far Field (Greater than this distance)
0.02668513m
Cortland Richmond
ka5s
On 6/13/18 8:14 AM, JW via RFI wrote:
> I suppose it should be mentioned, for completeness, that strictly speaking
> the inverse square law is inapplicable to that range of low band frequencies
> where propagation of the signal via ground wave is taking place, as on the
> 160 meter band,
> de Jim WB5WPA
>
> From: Kenneth Goodwin <krgoodwin@comcast.net>
> To: rfi@contesting.com
> Sent: Tuesday, June 12, 2018 9:55 PM
> Subject: Re: [RFI] Inverse Square Law and RFI
>
> The inverse square law is a geometric result based on the surface area of a
> sphere that applies to an RF source radiating equally in all directions that
> is in perfect environment, e.g. deep space. In most communication
> environments the ratio is closer to the fourth power especially in far field
> situations with all the good features of a typical RF environment -
> scattering, diffraction, reflection, blockage, etc. Signal attenuation
> depends on other factors like frequency not just the distance from the RF
> source as stated in the inverse square law. As Jim has indicated in his
> previous posting, in the real world it is never that simple. Ken K5RG
>
>
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