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Subject: Re: LF: Earth electrodes -  depth or surface area?
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Hello all,

not only the ground parameters and the over ground environment have their=
 influence but as simple as logical: The contact of the earth rods to the=
 ground.

Here is an interesting article about that:
http://www.academypublisher.com/ojs/index.php/jcm/article/download/0404284=
294/47

vy73 Horst DO1KHS/DI2AN


=C2=A0-----Urspr=C3=BCngliche Nachricht-----
Von: John Rabson <john.rabson@numeo.fr>
Gesendet: 27.05.2010 19:00:11
An: rsgb_lf_group@blacksheep.org
Betreff: Re: LF: Earth electrodes -  depth or surface area?

>JB, Roger, LF,
>
>It isn't  quite that simple. The standard analysis of a long thin ground=
  rod  (as per David Gibson's article) is to  estimate  the radius of the=
 buried hemisphere  which would give the same capacitance. Knowing the res=
istivity of the ground and  the estimated capacitance you can work out the=
 equivalent resistance. I don't have the analysis to hand but I seem to re=
call it models the rod as an oblate spheroid (as long as the length/diamet=
er ratio is not too great which it isn't in the caving situation). =20
>
>I seem to recall that the effective radius of a thin rod is about one fif=
th of its length. To get the benefits of multiple ground rods you need to=
 space them by at least twice their  length.
>
>73
>John F5VLF
>
>On 27 May 2010, at 15:13CEST, John Bruce McCreath wrote:
>
>>=20
>> Hello LFers,
>>=20
>> While laying in bed this morning pondering the inside of my eyelids I=
 got to thinking about the electrodes used
>> for "through the earth" communications.  What is more important, the de=
pth of the electrode or its surface area?
>> A typical 3/4 inch diameter by 4 foot long ground rod has a surface are=
a of 113 square inches, while a metal
>> plate 1 foot square has a surface area of 288 square inches.  If depth=
 is the key, then obviously the rods have
>> the advantage, but if it's surface area, the plates win hands down.  Ev=
en in stoney soil, it's relatively easy to
>> make a slit-like hole into which could be slipped a sheet of galvanized=
 metal with a lead attached.  To make
>> a good connection to the surrounding soil, pour some "kitty litter" int=
o the slit and moisten it with water so as
>> to improve the contact between the plate and the surrounding soil.  Am=
 I onto something here or have I
>> overlooked some important detail?  =20
>>=20
>> 73, J.B., VE3EAR
>>=20
>> LowFER Beacon "EAR"
>> 188.830 kHz. QRSS30
>>=20
>>=20
>>=20
>>=20
>>=20
>>=20
>>=20
>
>
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