AT Pro Target VDI# is Different with a Different Coil

[Ed-D]

I bought my AT Pro in 2011 and have been using the stock 8.5x11 coil ever since. I like that coil and it always met my needs. However, due to me being a dumb ass, I didn't always keep a fresh coil protector on it and long story short, a couple of months ago needed a replacement. I ended up buying two new coils; the Garrett 5x8 and a Nell Hunter 8.5x12.5.

I like both coils, but noticed something odd. No matter which coil I use the VDI#'s I am seeing are now -2 from where they were when I was using the Garrett stock coil. For example, with the stock coil a clad quarter always came in at 86-87; they now come in at 84-85. To make it even more weird, this oddity seems to only be evident on the higher VDI targets. I have found a few nickels using the new coils and they still come in at 51-53 (as do pull tabs). But I am seeing the higher VDI target #'s at -2 from where they were... and it is with both coils!

I asked Garrett if they had ever seen anything like this and they said it has to do with the size of the coils "field"... If that's the case why would it be the same for a small coil and a large coil.

Have you seen this? Does Garrett's explanation sound reasonable?

Yes, I pretty much dig everything anyway, but I am tiered of getting excited thinking I have a silver ring, when it's only a clad quarter. I'm kinda anal like that.

 

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[John-Edmonton]

Switching coils could give a slight deviation with VDI numbers. Remember, a VDI number is a probability of a coin sized object based on it's metallic composition, the amount/type of oxide in the coin, it's orientation to the coil, mineralization of the coil, humidity....just to name a few. There would also be a tolerance deviation between components in detectors, even after the detector is tuned. You are splitting hairs. It would be like my speedometer on my ford truck is not exactly the same as my Honda Civic. What is important, however, is that you noticed the difference, and now you can apply it to your searches.

 

[RobRieman]

It is a common occurrence for VDI's to change with different brands and sizes of coils. Some brands of detectors have a menu setting to pick the size of the coil to alter the VDI's so they stay consistent. The detector was built and tuned to the factory size coil that came with it.