Masking Issue... Or Normal?

[MichaelHill]

So today I was playing around with the Fe settings etc on the Nox 900. Just as a test, I laid a quarter on top of an empty plastic trash can. Next to it a rusty square nail. As long as the nail is laying with either the point or the head towards me, the coil hits the coin just fine, no hint of iron. Now, turn the nail so that it's pointing left or right, and the coin becomes invisible to the coil. This is on factory settings, park 1, park 2, field 1 and field 2...the only setting that has been changed is the Fe setting. It does this no matter what Fe is on ..-1 through 9. Out of curiosity I checked the X-Terra Pro and it does the same thing. Turn the nail pointing towards you or away, it bangs the coin. But, turn the nail so it points to either side and the coin disappears along with the nail. Has anyone else encountered this? 

[Chase Goldman]

It’s normal and called “down the barrel” masking as the coil is hitting the nail throughout the swing and it dominates the response of the detector.  Move a quarter way around the trash can and see if you can pick it up again.  That’s why when you get a ferrous hit, you should turn 90 degrees to see if the iron is potentially masking a non-ferrous target.  I’m not 100% sure how you have the nail oriented, but on your first nail quarter configuration, if you do the 90 degree turn, you might find the quarter disappears, just as in the second scenario.   One thing you can try is increasing recovery speed and see if that helps.

[MichaelHill]

As I explained, or tried to...if the nail is pointing to either side the there is no signal for the coin or the nail either one. If the nail is pointing to or away from me then the coin signal rings out loud and clear. There is no iron tone or grunt of any kind, so the nail is being masked out for sure, but depending how the nail is situated to the coin it also masks the coin out as well. Just found it odd, and like I said the X-Terra Pro does the same thing. It's just something Ive never noticed before. Makes me wonder how many coins I have walked over in high iron sites and didn't get because they were being masked out due to the orientation of a nail or similar shaped piece of iron. 

[GB_Amateur]

If you could post a drawing or photo of the setup it would help immensely.  What you describe can be interpreted in multiple ways.

[Jeff McClendon]

1 hour ago, MichaelHill said:

This is on factory settings, park 1, park 2, field 1 and field 2...the only setting that has been changed is the Fe setting.

Does factory settings mean that the iron range of target IDs are rejected? Are you doing the test with the horseshoe button all metals accepted function turned On or Off?

[MichaelHill]

Yes the factory range of iron ID's are rejected, but I also tried all metal mode as well, on or off it's still the same results. Would be interesting if someone would do the same test and see what their results are. My results are the same with the factory 11 and 6" coils, and a Coiltek 10x5 coil as well. 

[Chase Goldman]

48 minutes ago, MichaelHill said:

As I explained, or tried to...if the nail is pointing to either side the there is no signal for the coin or the nail either one. If the nail is pointing to or away from me then the coin signal rings out loud and clear. There is no iron tone or grunt of any kind, so the nail is being masked out for sure, but depending how the nail is situated to the coin it also masks the coin out as well. Just found it odd, and like I said the X-Terra Pro does the same thing. It's just something Ive never noticed before. Makes me wonder how many coins I have walked over in high iron sites and didn't get because they were being masked out due to the orientation of a nail or similar shaped piece of iron. 

What you described could be any one of the following pics.  Assume the coil is being swept left-to-right and vice versa over these two targets.  Which two apply to your setup and how did the detector respond?  Then we can talk specifics.  And yes, masking can leave a lot of targets in the ground.  That's why many experienced detectorists like to hear the iron and when they hit a target, they like to turn 90 degrees on the target to see how it responds and if it changes from ferrous to non-ferrous to make a dig decision.

Pic 1

Pic 2

 

Pic 3

Pic 4

 

[MichaelHill]

Pics 2 and 4 the detector will pick up the coin very well. No iron grunt or to e of any kind.

Pics 1 and 3 there is no tone of any kind for the coin or the nail either one, just absolute silence. 

The detector will.also pick up the coin if the nail is laying right on top of it, oriented as in pic 4, but if you turn 90 degrees it goes silent, no tone at all.

[Chase Goldman]

2 minutes ago, MichaelHill said:

Pics 2 and 4 the detector will pick up the coin very well. No iron grunt or to e of any kind.

Pics 1 and 3 there is no tone of any kind for the coin or the nail either one, just absolute silence. 

The detector will.also pick up the coin if the nail is laying right on top of it, oriented as in pic 4, but if you turn 90 degrees it goes silent, no tone at all.

Yep, that's the detector picking up the nail "down the barrel" as it encompasses a majority of the coil swing so it tends to dominate what the detector sees.  Increasing recovery speed has little effect.  And -1 iron bias doesn't help either.  Note that single frequency has no iron bias, but single frequency may not help either as you saw with the Xterra Pro.  When you get a signal like this it pays to turn 90 degrees to see if it unmasks.