A little expeiment in target masking

[luvsdux]

I’m sure any of you that have tried to get an understanding of masking already know this, but thought it might be an eye opener to some. As winter hasn’t quite finished here, I’ve been experimenting with my detectors indoors a bit. I put a silver dime and a thin, iron, back packing style, tent peg on a box side by side (didn’t have an iron nail handy). The box was to raise them above the floor so no flooring nails would have an affect.

Then I passed the coil of the detector over them with no disc. Of course I had a signal. Then I turned the Disc up to eliminate iron and passed the coil over again, left to right or east – west if you prefer, the tent peg’s long dimension up and down or north – south in relation to the coil. I got no signal or just a faint snap or crackle as we’d expect from disced trash. Then I passed the coil over the targets the other way, north – south and bingo a solid signal. I repeated this with several detectors and coil combinations with the same results.

Then I tried the same dime inside the ring on a pull tab and then right beside it. Inside the tab with tabs disced out, I didn’t get a signal. Beside the tab I got a mixed crackle, slight beep a bit stronger when the coil was swung to cross over the dime first. This turned out to be a pretty good example of why we should dig signals that aren’t strong in both directions and any that just don’t seem quite right. Of course, we could hunt mostly in all metal then hit the discrimination, but only digging and seeing will truly confirm whether the target was a goodie or junk, in the end.
HH
Bill

 

[Lowbatts]

You didn't mention how high above your target matrix the coil was but I'm sure your conclusions are correct.

I've maintained target masking can happen with something as small as an office staple in the right orientation to coinage. I've worked so many ground scrapes where no targets were seen in disc mode set from nickel up, but with mere inches taken off volumes of coinage suddenly appear.

In the same ground where I could easily locate a coin at ten inches, and nothing else but iron or low foil would be noted, suddenly there's coins everywhere when they take off 2-4 inches of dirt. That's why I think there's far more coinage left in the hunted out areas than many would guess. The newest machines are getting some of this stuff now, I think the DD coil offers the best response to this and even after that there's still plenty left.

 

[luvsdux]

I swung the coil from near surface to the 6-7' range. Sometimes got a bit more signal when the coil was nearly on the targets. Just shows the only SURE id is when the target is in the hand.

Bill

 

[deepskyal]

You can imagine what's been missed close to picnic shelters with all those pieces of tin foil and pulltabs every couple inches apart. I agree with you Lowbatts, the newer dd coils are going to be a boon to this hobby. And the smaller ones will help pick thru the mess.

Al