Pinpoint goes null over a screw with D2 coil?

[GoldChaser]

I have never noticed this before and am wondering if anyone else has as well.
I found and dug a signal in my yard and found a 3" screw, pic attached. It was pretty new and since it gave me a higher-than-expected VDI while in the ground (-17) I decided to do some extra testing on it.
When running the coil along its length I get the typical blip-blip double signal, usually identifying the target as a nail or equivalent. When pinpointing this 3" screw and passing the coil along the length of the coil, it goes quiet-loud-silent-loud-quiet !!! I have detected plenty of nails and screws before but can't recall ever getting this. I can go back and forth and it is always loud-silent-loud, with the silent when directly over the screw. I can hold it there over the screw and even move it left and right an inch or so and it stays perfectly quiet until it goes off-center.
I'm fairly new with the D2 coil, being a 6x10 fan for a few years, and have never experienced this with my 6x10 and am wondering if anyone else has. Please let me know.
Thanks!

 

[Aarong81]

I use the D2 as my primary coil and it does that with most small targets at surface depth, or against the coil. When I find a surface penny, it sounds like two targets. I know the tale-tale signs already to know it is merely a single, shallow target. An additional sign to know this is happening is that it is usually a very loud signal then dissapearing in an instant when moved off center. You just wouldn't expect a medium-deep target to hit hard then vanish so sharply. A deep target will fade gradually as you move off center. The reason you hear two seperate signals from one target is due to the shape of the coil and the unavoidable deadspot right in the center. This deadspot is not a problem when the target is not against the coil or extremely close to it. Try testing the screw again at a couple inches or more from the coil.