Decided to post some truth on coil size comparison

[Scott Maine]

First off I am not going to argue about this with John, he is misguided in his understanding of DD verses concentric and actually is completely wrong. I was closer in my understanding but far enough off to not qualify as being correct either.
One of the people involved with the design of the T2 gave me a very simple answer.
First off...you cannot accurately compare a DD coil size to a concentric coil size especially for size to size and depth to depth.
The explanation stated the DD coil on the T2 samples a volumetric amount of soil....in other words it is a 3D view....or volume equal to aprox 2/3 of a gallon of soil.
This was not something I have heard...or atleast related this way.
He also stated that if you were to compare that sampling amount to a concentric coil it would be the equivelant to a 6.3" concentric coil.
Which would seem that I was right on target while my Fla friend was way off. Well....we both are off.
While the volume sampling amount would equal a 6.3" coil.....I gathered that that does not indicate that the same 6.3" coil would be a fair comparison for depth verses coil size.
What I basically gathered is there is no fair way to compare...they are too different.
Now, I knew that there was enough of a difference between DD and concentric that the best test was to use the coils that performed the best in my area. My criteria was stability, target depth, target seperation AND sensitivty to target size.
A Nautilus with a 10" coil here..and I say here..is the same depth as an 8". The 8" coil HERE runs best in the area I tested.
My goal was to use two deep machines side by side with the exxact coils I would use in that situation.
I will not discuss this further.

 

[Ralph Bryant]

I think your comments here actually key on the issue of the T2 reportedly being designed only to use the DD style coil, and perhaps even "just" the stock coil provided, at least where the accuracy of the Fe304 reading is concerned. I really had not taken that into consideration before, but any change in the volume of ground the coil is reading is necessarily going to change he Fe304 reading. You could still do "comparison readings" with different coil sizes, but actual value readings of the Fe304 scale would be off, something similar to using depth readings for different coil diameters. The machine is calibrated to a specific coil and a certain volumetric value, and any change from that calibration point due to differences in coil size is going to skew the results.

Ralph

 

[Dave Z]

I had a 6x10dd on my DFX and it wasn't as deep as the stock 9.5.I would say a solid 2"less on coins than the stock.Sold it rather quickly,it was about the same size as the stock and not as deep.So I really saw no need for it.Dave

 

[Scott Maine]

n/t

 

[Mike Hillis]

That is what I was told. What size that will actually be and when is still up for grabs last I heard.

 

[Scott Maine]

n/t