I'm still a grounding dumy but I've just bought a GEO test and have done
some soil resistivity test
(for just 800US$ I can do 4 pole methods, cheapest I have found and
still has serial port
to colect data ...)
I'm still in putting my new tower of 200ft ...
Now I have some questions.
In a place where I have 2 ground roads (each 2.5m) I have a resistivity
4m away I have a resistivity of 500.
The test was done with the 4 pole method.
I have not measured the ground of the house, only the soil just above
roads are with several depth and in the deps of 3 m I have this 120
Now my questions:
1. This low resistivity comes from the 2 ground roads already there
I have read that 2 ground roads in parallel will half the resistivity
i..e 500/2 250 but I have 120
If you use 4 you get Resistividad/4 i.e. 500/4=125
Is this formula right?
The other idea is that the fundament of the house is very near (about
1m) could this also
have such influence to lower the resistivity because of concret??
2. The resistivity of 500 is not very good, isn't it?
I have calculated that you must put 36 ground roads in parallel to
achive a resitance of 13.8
which is still pretty bad (of course only if the formula above is right)
BTW: The tests have showed what someone already told me that the soil
here is not good
to go in depth ... I have the following:
a=2m -> 486
a=3m -> 546
a=6m -> 429
so it seems that going in deep does not make any difference (apart from
the cables you must use
to connect the ground roads) in contrast to use parallel ground roads.
And last question:
How many copper have good ground roads. The ground roads I can buy here
have only 200um of copper
(5/8''-2m or 5/8''-3m). I have seen that they peel quickly if driven
into earth and there is any obstacle ...
What I can get also is plate of copper 30cmx30cm but this costs about 8
times more than one ground road
I don't know how they lower the resistividad of the soil ... I have read
in an article about
0.8*Resitivida/circumference is this right?
What about putting using the fundament of the house i.e. drive a whole
in the concrete and connect a
copper or what ever cable ot the iron and put again concret?
Thanks for any ideas or comments
TowerTalk mailing list