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/0404284294/47
vy73 Horst DO1KHS/DI2AN
-----Ursprüngliche Nachricht-----
Von: John Rabson <[email protected]>
Gesendet: 27.05.2010 19:00:11
An: [email protected]
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 resistivity 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 recall it models
>the rod as an oblate spheroid (as long as the length/diameter ratio is not too
>great which it isn't in the caving situation).
>
>I seem to recall that the effective radius of a thin rod is about one fifth 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:
>
>>
>> Hello LFers,
>>
>> 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 depth
>> of the electrode or its surface area?
>> A typical 3/4 inch diameter by 4 foot long ground rod has a surface area 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. Even 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" into 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?
>>
>> 73, J.B., VE3EAR
>>
>> LowFER Beacon "EAR"
>> 188.830 kHz. QRSS30
>>
>>
>>
>>
>>
>>
>>
>
>
___________________________________________________________
NEU: WEB.DE DSL für 19,99 EUR/mtl. und ohne Mindest-Laufzeit!
http://produkte.web.de/go/02/
|
