I have been using White's DFX for 2 years and i'm having problems with rusty nails. They come up on the screen to the right, full bars and VDI numbers 65-85. I called White's about this problem and they said it's normal because of the rust halo. I can't believe that a rusty nail will come up the same as a coin, there must be a way to tell the difference. The audio-signal also repeats from 90 degrees of the target. I tried a smaller coil but how do you get between rusty nails when the detector is telling you that they are coins with full bars and 85 VDI???? I have Jeff Fosters book and Jimmy Sierra's book on metal detecting and tried corlate, hotrock reject same problem. Does anyone have any ideas how to solve this problem? Does anyone with other brands of detectors have this problem with nails? Any response would be greatly appreciated, thanks! Bill T.
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somebody help me
- Thread starter diggeroof
- Start date
First, are you certain they are rusty iron nails? Through the years I have hunted some sites where I hit on a mess of nails in an area and they all sounded quite good. They were old copper based square nails.
Second, ALL detectors can have some problems with iron nails. Forget about the "rusty" issue or the talk about a "halo" because just a nail by itself can cause some problems.
Part of it is due to the total make-up of the nail. Part is based on the fact that this is man-made and shaped iron and therefore has more conductive properties. Then, too, there is the fact that these are elongated objects and they are iron. Iron has a different effect on the electromagnetic field than would a non-ferrous object, such as a coin or even a similar shape of copper or aluminum.
It is absolutely no problem to reject iron nails. I can reject them 100% if the time with the discrimination control ............ IF, that is, I am using a conventional TR-Discriminate detector!
The problem is that while your DFX does operate on a Transmit/Receive principle, the Discriminate mode is not a true, conventional TR-Disc. mode. Instead, it is one that attempts to compensate for ground signal (GEB) and target signal (Disc. the bad and accept the good) at the same time and ALL (every single one) of these motion Discriminate detectors have an issue with clean and proper rejection of some targets. One of th biggest offenders is the crimp-edge, pry-off type bottle cap (some call it a "crown cap"), but it can also apply to iron nails and various forms of rusty tin and other magnetic (stick to a magnet) type targets.
The secret to good target ID and rejection is two fold. One is to make sure you're using a proper size coil for the site, and if there is iron nail trash you ought to be using a smaller-size coil such as the 5.3 Eclipse. The second it operator technique to deal with suspect junk.
I'll be brief here but a search on these forums will reveal my comments on A.T.C.
I coined the term A.T.C. (Audio Target Classification) about 27 years ago when I was doping some instruction and seminars. Common forms of A.T.C. include "sizing and shaping" a target. You can tell if it is elongated or not, or you can often tell if it is a wide-response (iron and/or large target) or a narrow response (non-ferrous and coin, token or button-like size).
A.T.C. might also include raising the coil away from the ground to determine if that strong, good-sounding response is a shallow target or a deeper large target.
Best of all techniques, from my years of experience, is using two techniques I've been using and demonstrating since the early motion discriminators about 30 years ago (but works much better with newer motion-based detectors). I termed these "Quick-Out" and "E.P.R." or Edge Pass Rejection.
In short, when you have a target that you suspect might be a bad target, make a short and brisk sweep of the coils center across the target. If you get a diminished audio response and/or more of a broken audio or visual TID, then it is quite possible the target is not desirable.
If a short, quick sweep (Quick-Out) doesn't knock a bad (iron or magnetic-based metal) target out or not sufficiently, you can try EPR.
Edge Pass Rejection doesn't use the very 'edge' of the search coil, but a spot out from the center toward the edge of the coil.
You can locate your detector/coil combination's 'edge' point by doing the following. Place a smaller coin on the ground, such as a penny, dime or nickel. Sweep directly across with the coils center and listen to the audio with the coil about 2"-3" above the coin.
Now, continue to make repeated sweeps across the coil as you slowly back the coil away from the target. Not a spot on the coil (such as a decal, etc.) where the coin is in-line when you are last able to get a good repeatable audio signal. Not a good Target ID, just a clean and decent audio response. This is the "edge" point.
Now, use a bottle cap or other ferrous-type offending target and place it on the ground. Sweep directly across it and you might hear a good audio response. Next, try a "Quick-Out" maneuver to see if you can reject it (no audio, broken audio, and a "smear" or and Iron reading).
If that doesn't do the trick, try Edge Pass Rejection. Sweep directly across the target with the coils center, then back the coil away to the "edge" where a good non-ferrous coin still makes a good beep. More than likely, you will now have lost that dreaded piece of junk and have an 'iron' TID read-out. In some really challenging environments, you can combine the EPR technique with a little extra sweep speed (Quick-Out), but just remember to not sweep the coil over a wide area, just across the target with the coil just beyond the target position at the start and finish of the brisk, short sweep.
If I confused you, drop me an E-mail.
MonteVB@comcast.net
Monte
Second, ALL detectors can have some problems with iron nails. Forget about the "rusty" issue or the talk about a "halo" because just a nail by itself can cause some problems.
Part of it is due to the total make-up of the nail. Part is based on the fact that this is man-made and shaped iron and therefore has more conductive properties. Then, too, there is the fact that these are elongated objects and they are iron. Iron has a different effect on the electromagnetic field than would a non-ferrous object, such as a coin or even a similar shape of copper or aluminum.
It is absolutely no problem to reject iron nails. I can reject them 100% if the time with the discrimination control ............ IF, that is, I am using a conventional TR-Discriminate detector!
The problem is that while your DFX does operate on a Transmit/Receive principle, the Discriminate mode is not a true, conventional TR-Disc. mode. Instead, it is one that attempts to compensate for ground signal (GEB) and target signal (Disc. the bad and accept the good) at the same time and ALL (every single one) of these motion Discriminate detectors have an issue with clean and proper rejection of some targets. One of th biggest offenders is the crimp-edge, pry-off type bottle cap (some call it a "crown cap"), but it can also apply to iron nails and various forms of rusty tin and other magnetic (stick to a magnet) type targets.
The secret to good target ID and rejection is two fold. One is to make sure you're using a proper size coil for the site, and if there is iron nail trash you ought to be using a smaller-size coil such as the 5.3 Eclipse. The second it operator technique to deal with suspect junk.
I'll be brief here but a search on these forums will reveal my comments on A.T.C.
I coined the term A.T.C. (Audio Target Classification) about 27 years ago when I was doping some instruction and seminars. Common forms of A.T.C. include "sizing and shaping" a target. You can tell if it is elongated or not, or you can often tell if it is a wide-response (iron and/or large target) or a narrow response (non-ferrous and coin, token or button-like size).
A.T.C. might also include raising the coil away from the ground to determine if that strong, good-sounding response is a shallow target or a deeper large target.
Best of all techniques, from my years of experience, is using two techniques I've been using and demonstrating since the early motion discriminators about 30 years ago (but works much better with newer motion-based detectors). I termed these "Quick-Out" and "E.P.R." or Edge Pass Rejection.
In short, when you have a target that you suspect might be a bad target, make a short and brisk sweep of the coils center across the target. If you get a diminished audio response and/or more of a broken audio or visual TID, then it is quite possible the target is not desirable.
If a short, quick sweep (Quick-Out) doesn't knock a bad (iron or magnetic-based metal) target out or not sufficiently, you can try EPR.
Edge Pass Rejection doesn't use the very 'edge' of the search coil, but a spot out from the center toward the edge of the coil.
You can locate your detector/coil combination's 'edge' point by doing the following. Place a smaller coin on the ground, such as a penny, dime or nickel. Sweep directly across with the coils center and listen to the audio with the coil about 2"-3" above the coin.
Now, continue to make repeated sweeps across the coil as you slowly back the coil away from the target. Not a spot on the coil (such as a decal, etc.) where the coin is in-line when you are last able to get a good repeatable audio signal. Not a good Target ID, just a clean and decent audio response. This is the "edge" point.
Now, use a bottle cap or other ferrous-type offending target and place it on the ground. Sweep directly across it and you might hear a good audio response. Next, try a "Quick-Out" maneuver to see if you can reject it (no audio, broken audio, and a "smear" or and Iron reading).
If that doesn't do the trick, try Edge Pass Rejection. Sweep directly across the target with the coils center, then back the coil away to the "edge" where a good non-ferrous coin still makes a good beep. More than likely, you will now have lost that dreaded piece of junk and have an 'iron' TID read-out. In some really challenging environments, you can combine the EPR technique with a little extra sweep speed (Quick-Out), but just remember to not sweep the coil over a wide area, just across the target with the coil just beyond the target position at the start and finish of the brisk, short sweep.
If I confused you, drop me an E-mail.
MonteVB@comcast.net
Monte
One of the most valuable posts i ever read from Monte was Edge pass rejection and learned how to ID an interfering iron object more than enough times to know it works. Once you notice the iron imprint almost any target id could be a good target but at least know the reason to question the audio or visual ID. There are many other reasons to doubt a target ID but as long as you know there are many variables you may have a different perspective on digging a target.
We have to learn to play the odds from experience but it's nice have help from folks like Monte to help the learning curve. HH Bill
We have to learn to play the odds from experience but it's nice have help from folks like Monte to help the learning curve. HH Bill