Concentric vs DD what's up with this!

I have a test garden with several coins and have 3 dimes at about 8 inches in ground that has not been sanitized, in fact it contains lots of nails etc. With my F75 LTD using both the stock coil and the 5"DD running Bp sens 80 disc at 5 or basically any other setting I can hit one of the dimes consistantly and the other 2 are very hard to hit. I also had an explorer xs and had the about the same results. I decided to put on the 10" concentric, which I have never used, on the LTD. I can now hit all three dimes consistantly with much better VID and sound. Why is the concentric doing better in this situation? The ground is not highly mineralized, I never used the concentric because I thought the DD would do much better in nails and such. Any ideas?? Thanks Randy

TOO many variables in this one....to be able to give a educated guess. BUT.......is does sound like you are encountering 'wrap-around' effect better with the concentric coil.

Let's say a coin is buried at 7". And let's say that a very small piece/sliver of nail is 4" deep.......and directly above the coin. ((( This would be 3" above the coin ))). ,,,,,,,,,,,, It would be common that a very tight footprint DD coil would place MORE FOCUSED energy on the 4" deep sliver that is directly above the coin........and possibly miss the coin; ................. whereas........... a concentric coil....of which does NOT have 'focused' energy............would place less energy on the 4" deep sliver.......and poses a wider angle-of-attack envelope footprint; subsequently lending a better chance of detection of the coin.

Now....................if this little sliver of nail were to be kept at the exact same depth.............but laterally separated (off to one side) by just an inch or two from the coins top-dead-center.....................this would pose a completely different scenario whereby the DD coil would have a strong advantage.

I covered this topic in the "Coil Size Myths" article........if you are interested in amp-info. There are also other articles and threads where this phenomenon is explained.

Tom,
I think that is the answer. Most of the nails and wire ect. that are in my yard fall into the 3 to 5 inch range. I also have small pieces of aluminum foil that are wadded up and look burned all over the yard for some reason and they also fall into the 3 to 5 inch range. That does make sense. Thanks Tom for the response, I really appreciate it. Randy



Edited 1 time(s). Last edit at 10/31/2010 03:34PM by iskirkra.