Real data:
I am presently using a 30' base loaded vertical. The ground system consists
of 90 radials from 12 to 25 feet. The base referred ground loss is 10 ohms.
Dave WX7G
On Sep 27, 2012 6:26 PM, "W2XJ" <w2xj@w2xj.net> wrote:
> Richard
>
> The data is indisputable but I think for the average ham about a dozen 45
> degree radials will produce about 3 DB less than theoretical. That is less
> than an S unit. The other difference is that all this information is based
> on ground wave propagation. There is nothing that addresses higher angle
> sky wave propagation common for 160 M operation.
>
> Sent from my iPad
>
> On Sep 27, 2012, at 7:38 PM, "Richard Fry" <rfry@adams.net> wrote:
>
> > Guy Olinger wrote:
> >
> >> Can you pass along your source of information that BL&E was done over 4
> mS/m soil, ... Or are you using the FCC map for typical soil conductivities
> and presuming a common New Jersey value and no variation at the site?
> >
> > It is my presumption that for their cost and logistics, and with my 15
> years of insight as an RCA Broadcast field engineer (1965-1980), the BL&E
> measurements were made near Princeton, NJ. I'll try to confirm that, and
> advise. Princeton was the corporate facility containing the
> office/laboratory of George H. Brown.
> >
> > If those tests had been made at some physical location where earth
> conductivity at/near the test site was significantly better than in New
> Jersey, this would have been evident in their measured data.
> >
> > For an example of this, if earth conductivity at/near the test site was
> 30 mS/m, then even relatively few/relatively short buried radials in
> contact with that earth would enable higher radiated fields than shown in
> the BL&E data for those radial numbers and lengths. This is illustrated by
> the NEC4 study using a short monopole on 1.85 MHz at this link:
> http://i62.photobucket.com/albums/h85/rfry-100/10m_Vert32Buried_Radials.jpg.
> >
> > Even for an earth conductivity of 4 mS/m, the BL&E data show that
> monopoles ranging from about 45 to at least 90 degrees in physical height,
> driven against an r-f ground system consisting of at least 113 x 0.412-wave
> buried radials, produces a groundwave field at 3/10 of a mile that is
> within several percent of the maximum theoretical value possible for a
> perfect monopole driven against a perfect ground plane, for that applied
> power.
> >
> > The bottom line in all of this is that the worse the earth conductivity
> within 1/2-wavelength of the base of a monopole (especially a short
> monopole) while driving that monopole against a set of buried radials, the
> more important it becomes to use a large number of such radials of lengths
> approaching 1/2 of a free space wavelength.
> > _______________________________________________
> > UR RST IS ... ... ..9 QSB QSB - hw? BK
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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