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PostPosted: Sat Feb 12, 2011 3:25 pm 
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Joined: Sat Feb 12, 2011 2:53 pm
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Hi 2 all,
i have heard that recently some companies have produced GPR antenna with 100 to 150 m penetration in best conditions. is it right?
anyhow I need to GPR investigation up to 10 m in wet clay! what is your idea?
thanks in advance


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PostPosted: Sun Feb 13, 2011 9:14 am 
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100 - 150 meters penetration ... in ice, right?
jd


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PostPosted: Tue Mar 01, 2011 7:34 am 
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Joined: Fri Apr 17, 2009 7:52 am
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Location: Boden, Sweden
p9kia wrote:
anyhow I need to GPR investigation up to 10 m in wet clay!

The attenuation is so big in wet clay that there will be nothing left of the initial energy if it ever passes beyond
the first layer, let alone returning back to the receiving antenna.
This is going to be extremely difficult, the only thing I can suggest you to do is to drill a hole in the ground and
download a borehole antenna to pass beyond the 10 m of wet clay. In cases of wet clay what we usually do is to
remove the clay with a bulldozer, but of course this is a solution to 20 - 30 cm of clay, 10 m of clay is way beyond
the scope of this "remedy".
Hope this gives you some ideas,
Regards,

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Reinaldo Alvarez Cabrera
Geoscanners AB
Sweden
http://www.geoscanners.com


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PostPosted: Mon Apr 04, 2011 7:57 pm 
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Quote:
10 m of clay is way beyond
the scope of this "remedy".

any "remedy" to be honest :|
jd


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PostPosted: Sat Jul 02, 2011 2:11 pm 
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Joined: Sat Jul 02, 2011 1:55 pm
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Location: Ukraina
[link removed]

Loza can do it

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GPR Europe ltd.
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Last edited by GeoAdmin on Tue Apr 09, 2013 8:11 pm, edited 1 time in total.
link removed because spam hosting site


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PostPosted: Mon Jul 04, 2011 6:28 am 
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Location: Zagreb, Croatia
Hi LozaUA,
your example looks quite intriguing.
Could you give some more info about the site and survey (and possible a more complete interpretation)?
BR

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"If the only tool you have is a hammer, you will see every problem as a nail."


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PostPosted: Mon Jul 04, 2011 5:12 pm 
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Location: Ukraina
With pleasure, it is geophysical range of the Moscow state university, it is located on the river Ugra, in the Kaluga region the Russian Federation. The geology is presented by a layer dense clay 20-25 m, limestones more deeply lie down, there is a karst development. It is executed by a low-frequency GPR-complex the Loza, 25MHz


It`s subway tunnel [link removed]

more info Deep georadar researches

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GPR Europe ltd.
www.gpr-europe.com
www.gpr-team.com


Last edited by GeoAdmin on Tue Apr 09, 2013 8:12 pm, edited 1 time in total.
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PostPosted: Tue Jul 05, 2011 11:06 am 
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LozaUA wrote:

Loza can do it

Hi LozaUA,
If you don't mind me asking:
What is the dynamic range of your unit?
Regards,

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Reinaldo Alvarez Cabrera
Geoscanners AB
Sweden
http://www.geoscanners.com


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PostPosted: Tue Jul 05, 2011 3:20 pm 
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Location: Ukraina
120 decibels. The range of used frequencies from 300-200-150-100-50-25-15-10-1 MHz, depth depends on length of aerials and capacity of the transmitter (1-10 МВт)

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www.gpr-europe.com
www.gpr-team.com


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PostPosted: Wed Jul 06, 2011 2:42 pm 
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Joined: Fri Apr 17, 2009 7:52 am
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Location: Boden, Sweden
Thank you LozaUA for your answer.
We probably are talking about different things here. let's define "clay":
RDP = 16 - 17 (saturated we are ignoring dry clay for now)
Sigma = 0.01 - 0.1 S/m (to be wide open about this)

with that in mind we find out that:
Best case scenario - 4.1dB/m
Worse case scenario - 40.96dB/m
Required strength of the signal:
Best case scenario - 4.1*20*2 = 164dB
Worse case scenario - 40.96*20*2 = 1638dB
It doesn't make much sense, does it?

Now, 30 or even 40m in dry sand is not a problem for HF band antennas, don't get
me wrong about that. I would imagine that in those conditions and with your LF band
antenna you can go pretty far, although the objects would have to be huge at those
depths. Which in many cases is not a problem, like a subway tunnel or station for
instance. Then again, that won't be any problem for any other manufacturer
producing these kind of antennas, even without the MW outputs.
Regards,

_________________
Reinaldo Alvarez Cabrera
Geoscanners AB
Sweden
http://www.geoscanners.com


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