[RFI] Inverse Square Law and RFI

[Cortland Richmond]

BPL was common mode for at least one horizontal conductor  and (I don't 
have access to the data) not a  source, (arcing insulator, etc) local to 
the pole/tower ground; at OUR frequencies; given the inductance of the 
intra-pole ground conductor, the nearest vertical one  *would* carry the 
most RF current.

Cortland

KA5S


On 6/13/18 11:06 AM, JW wrote:
> 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 at earthlink.net>
> *To:* rfi at 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 at comcast.net>
> >  To: rfi at 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
> >
> >
> > _______________________________________________
> > RFI mailing list
> > RFI at contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
>
> >
> >
> >
> > _______________________________________________
> > RFI mailing list
> > RFI at contesting.com
> > http://lists.contesting.com/mailman/listinfo/rfi
>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
>