Monte,

My guess is your coil was fine....and you are just tuned in better to concentric coils as your preference. But, you know better than i that you can get a bad coil, and a coil can be 'tuned' to work better with your machine than another.

I paid attention today as i was hunting along w/ the 7" Detech. I will agree that in a park like environment, the VDI's are a bit tighter on the 6" concentric. They both tend to lock on for me w/ any silver coin, though the old pennies that have seen some verdigris seem to move around bit. Interestingly, when i dig old pennies w/ the V3i and any coil, i set it up to show all the frequency hits coming through on my screen. It paints a nice tight little bell curve of frequencies above and below the hardest hitting frequency....i presume due to the various elements in the copper and deterioration.. A silver coin, however, typically hits on only 1 VDI...though it might vary by a point or 2 when comparing VDI hits across the 3 simultaneous frequencies as you can see all three on the visible screen.

I will also agree that the Detech doesn't pinpoint as well as a concentric. I've never seen a DD nail the location right in the center. For me, it always seems to be somewhere between center and the edge closest to me. I sometimes miss a target with my 10" DD and its almost always in the side of the hole nearest me. Have learned to offset my plugs.

It did, however, hit sufficiently on 5" deep coins today that I'm not at all sure the concentric would have located with a VDI that would have caused me to pay attention. If its in the iron range, I generally pass by unless i know there are deep coin targets in the area due to other recoveries...and i've dug those before successfully - recently i did that w/ the IDX pro and the 3.5" coil. It said iron at end of coil range....but i suspected otherwise. Dug an IHC about 3-4" down.

Anywhoo, just some more data points, and alignment with several of your observations.

Brian