steve herschbach
New member
Hi,
From the moment I got an X-Terra 50 it seemed to me the unit was hot on tiny items. It seemed to have great potential for small gold items, and I posted on this at length at http://www.findmall.com/read.php?55,228791
I used the X-Terra 50 to do some beach hunting and again came to the conclusion it was hot on small items, as I posted at http://www.findmall.com/read.php?55,251295
My only quibbles with the X-Terra on tiny non-ferrous items is that 1. The X-Terra lacks a single tone all-metal mode and 2. It therefore has a "bouncy" signal on tiny targets, as small non-ferrous items tend to bounce from ferrous low tone to non-ferrous medium tone.
As my main interest for the X-Terra is hunting jewelry and maybe even a little nugget hunting the promised 18.75 kHz coil was of huge interest to me. Just as I received this new coil I also got some requests to do some more tests on small gold items with the X-Terra 50.
So I dug out my test rocks. I have two flat rocks of moderate iron content I use to test machines for nugget detecting. They are not "hot rocks" but they do simulate moderately mineralized ground well when placed over test targets. One thing I have learned over the years is that in most locations VDI or target id number get pulled lower the deeper an item is buried. At the extreme edge of detection depth most detectors will actually call non-ferrous items iron, and so even minimal iron rejection will eliminate them.
I'm sure this effect varies by location and ground mineral content. I've heard some areas actually cause VDI numbers to increase, but from my reading of others posts this seems to be rare. On certain machines, like the Fisher CZ series, this effect is well-known and commented on by quite a few people. Even machines like the Minelab Explorer that purport to be less affected by ground mineralization are reported to have target id numbers shift with depth in some locations.
This effect is far more pronounced with low conductive targets like gold but does exist for higher range coins also. The difference is with gold it can pull down into iron readings, whereas coins just shift down into lower but still non-ferrous readings. But super deep coins can finally end up reading iron before they go out of range.
When nugget detecting in junky iron areas, a wise person trying to reject iron junk will use a machine that instead of rejecting iron, will give an iron signal. So you know you have a suspected iron target. Then kick an inch or two of dirt off the top, and see if the signal changes to non-ferrous. And sure enough, an iron reading will sometimes end up being a deep gold nugget.
A person running a machine with a silent rejection type mode like a Fisher Gold Bug 2 should run in all-metal, then switch to iron id to check the target for an iron reading. If an iron reading is had, take a couple inches off and see if it changes. What you do not want to do is run in iron id mode all the time as the item will get identified as iron and the machine will not even beep, so you will never even know you had a target. A machine like a White's GMT will alert you to a suspected iron target via a "grunt" but will not eliminate the target, so you get the chance to check it out.
I will admit, however, that I have run my Gold Bug 2 in iron reject full-time in trashy locales as sometimes I simply do not want to analyze every target. But I do so knowing I probably miss gold. Clean reject units like the Gold Bug 2 can also reject noise from certain numerous hot rocks and run quieter in areas where machines like the GMT grunt multiple times per sweep. So having a true rejection mode can have its advantages at times.
This is getting long, but bear with me. When coin detecting this effect is one reason why notching or discrimination of any sort is a bad idea. If you do not get alerted to a target you cannot analyze it. A machine that gives you signals on all targets gives you the chance to hear that iron signal, and then maybe press your coil down real hard in the grass to get that 3/4" closer to the target that it takes to make it goes non-ferrous instead of reading iron. Or maybe you can sweep faster or slower over the target, depending on the machine, to clean up the signal. Unfortunately, in turf you can't just kick a couple inches off the top like I can when nugget detecting.
So yes, I do understand how notching can cost me targets. But I still like to notch out targets sometimes, and that is one big reason I like the X-Terra machines. Given all I know about masking, deep signals, and VDI shift, sometimes I simply do not want to set my machine to beep on everything and work every target that hard. Many times I do. It can be fun and productive. But sometimes I want to cherry pick certain VDI ranges for all kinds of reasons and I do not want to be distracted by all the other targets. Just kiss off borderline targets and go for shallower stuff that give a clean id. I like notching!
Another note. High frequencies are not just more sensitive to gold items. It is that high frequencies give more accurate VDI numbers on low conductive items than higher frequencies. A higher frequency machine is less likely to call a gold item iron in mineralized ground than a lower frequency machine. So even if two units manage to signal on the gold, a high frequency unit is more likely to properly identify it.
OK, finally time to get to the point. I took my smaller test rock and put it over a thin gold nugget about the size of a small fingernail. The nugget air tests on the X-Terra 50 with stock coil as numeric 6, a good gold reading. I put my little rock over it, and got a reading of -3. A real solid -3. I could not get it to chirp higher no matter what. I re-ground balanced on the rock both higher and lower and it made no difference. The rock pulled the nugget two segments lower and made it read iron. Good solid beep, just wrong id.
Hmmm... I was not liking this. I do know about this kind of stuff, but it always looks bad when you see it put so plainly before you eyes. I started to wonder how many solid iron signals in Cabo might have been gold. I dug the bouncers but ignored quite a few solid iron readings as the few I dug did turn up iron. But now I was thinking maybe I should have kicked more sand off of more targets. Or just dug them all!
Oh well, live and learn. But this was not making me too happy, as jewelry is my main goal with the X-Terra. So I put the new 18.75 kHz coil on and gave it another try. And the nugget read good and clear again as numeric 6 through the rock! Yay!!
I fiddled around for some time with my gold and test rocks. I can tell you two things for sure. In at least some circumstances, small gold items will drop by a couple segments with the stock 7.5 kHz coil. Coins do not seem to be as affected but I would not be surprised if someone somewhere finds they are. I would very much like for anybody to try and duplicate and confirm what I am talking about here.
I can also say that the 18.75 kHz coil very much corrects this issue and so is a "must-have" for anyone wanting to go after gold with the X-Terra 50. It not only brings the target id back up to where it should be in mineralized ground, but it strongly boosts the signal on tiny gold. My two grain nugget only signals on the 7.5 kHz coil if rubbed on it, and it bounces into iron. It signals nicely through my test rock with a non-ferrous id of 3 with the 18.75 kHz coil. The higher frequency coil should greatly reduce the tendency of small items to bounce into iron, and some small items to just plain read as iron!
There may be some loss of depth on coins with the higher freq coil. I do not care for my uses. For me the 18.75 kHz coil is the only coil I am likely to be using on my X-Terra 50 going forward. You other guys can figure out for me what I'll be giving up on coins as it is probably more important to you.
Well, in closing I must say I continue to be pleased with my X-Terra 50. Now the more so as the new coil does make a substantial difference in my own area of particular interest
From the moment I got an X-Terra 50 it seemed to me the unit was hot on tiny items. It seemed to have great potential for small gold items, and I posted on this at length at http://www.findmall.com/read.php?55,228791
I used the X-Terra 50 to do some beach hunting and again came to the conclusion it was hot on small items, as I posted at http://www.findmall.com/read.php?55,251295
My only quibbles with the X-Terra on tiny non-ferrous items is that 1. The X-Terra lacks a single tone all-metal mode and 2. It therefore has a "bouncy" signal on tiny targets, as small non-ferrous items tend to bounce from ferrous low tone to non-ferrous medium tone.
As my main interest for the X-Terra is hunting jewelry and maybe even a little nugget hunting the promised 18.75 kHz coil was of huge interest to me. Just as I received this new coil I also got some requests to do some more tests on small gold items with the X-Terra 50.
So I dug out my test rocks. I have two flat rocks of moderate iron content I use to test machines for nugget detecting. They are not "hot rocks" but they do simulate moderately mineralized ground well when placed over test targets. One thing I have learned over the years is that in most locations VDI or target id number get pulled lower the deeper an item is buried. At the extreme edge of detection depth most detectors will actually call non-ferrous items iron, and so even minimal iron rejection will eliminate them.
I'm sure this effect varies by location and ground mineral content. I've heard some areas actually cause VDI numbers to increase, but from my reading of others posts this seems to be rare. On certain machines, like the Fisher CZ series, this effect is well-known and commented on by quite a few people. Even machines like the Minelab Explorer that purport to be less affected by ground mineralization are reported to have target id numbers shift with depth in some locations.
This effect is far more pronounced with low conductive targets like gold but does exist for higher range coins also. The difference is with gold it can pull down into iron readings, whereas coins just shift down into lower but still non-ferrous readings. But super deep coins can finally end up reading iron before they go out of range.
When nugget detecting in junky iron areas, a wise person trying to reject iron junk will use a machine that instead of rejecting iron, will give an iron signal. So you know you have a suspected iron target. Then kick an inch or two of dirt off the top, and see if the signal changes to non-ferrous. And sure enough, an iron reading will sometimes end up being a deep gold nugget.
A person running a machine with a silent rejection type mode like a Fisher Gold Bug 2 should run in all-metal, then switch to iron id to check the target for an iron reading. If an iron reading is had, take a couple inches off and see if it changes. What you do not want to do is run in iron id mode all the time as the item will get identified as iron and the machine will not even beep, so you will never even know you had a target. A machine like a White's GMT will alert you to a suspected iron target via a "grunt" but will not eliminate the target, so you get the chance to check it out.
I will admit, however, that I have run my Gold Bug 2 in iron reject full-time in trashy locales as sometimes I simply do not want to analyze every target. But I do so knowing I probably miss gold. Clean reject units like the Gold Bug 2 can also reject noise from certain numerous hot rocks and run quieter in areas where machines like the GMT grunt multiple times per sweep. So having a true rejection mode can have its advantages at times.
This is getting long, but bear with me. When coin detecting this effect is one reason why notching or discrimination of any sort is a bad idea. If you do not get alerted to a target you cannot analyze it. A machine that gives you signals on all targets gives you the chance to hear that iron signal, and then maybe press your coil down real hard in the grass to get that 3/4" closer to the target that it takes to make it goes non-ferrous instead of reading iron. Or maybe you can sweep faster or slower over the target, depending on the machine, to clean up the signal. Unfortunately, in turf you can't just kick a couple inches off the top like I can when nugget detecting.
So yes, I do understand how notching can cost me targets. But I still like to notch out targets sometimes, and that is one big reason I like the X-Terra machines. Given all I know about masking, deep signals, and VDI shift, sometimes I simply do not want to set my machine to beep on everything and work every target that hard. Many times I do. It can be fun and productive. But sometimes I want to cherry pick certain VDI ranges for all kinds of reasons and I do not want to be distracted by all the other targets. Just kiss off borderline targets and go for shallower stuff that give a clean id. I like notching!
Another note. High frequencies are not just more sensitive to gold items. It is that high frequencies give more accurate VDI numbers on low conductive items than higher frequencies. A higher frequency machine is less likely to call a gold item iron in mineralized ground than a lower frequency machine. So even if two units manage to signal on the gold, a high frequency unit is more likely to properly identify it.
OK, finally time to get to the point. I took my smaller test rock and put it over a thin gold nugget about the size of a small fingernail. The nugget air tests on the X-Terra 50 with stock coil as numeric 6, a good gold reading. I put my little rock over it, and got a reading of -3. A real solid -3. I could not get it to chirp higher no matter what. I re-ground balanced on the rock both higher and lower and it made no difference. The rock pulled the nugget two segments lower and made it read iron. Good solid beep, just wrong id.
Hmmm... I was not liking this. I do know about this kind of stuff, but it always looks bad when you see it put so plainly before you eyes. I started to wonder how many solid iron signals in Cabo might have been gold. I dug the bouncers but ignored quite a few solid iron readings as the few I dug did turn up iron. But now I was thinking maybe I should have kicked more sand off of more targets. Or just dug them all!
Oh well, live and learn. But this was not making me too happy, as jewelry is my main goal with the X-Terra. So I put the new 18.75 kHz coil on and gave it another try. And the nugget read good and clear again as numeric 6 through the rock! Yay!!
I fiddled around for some time with my gold and test rocks. I can tell you two things for sure. In at least some circumstances, small gold items will drop by a couple segments with the stock 7.5 kHz coil. Coins do not seem to be as affected but I would not be surprised if someone somewhere finds they are. I would very much like for anybody to try and duplicate and confirm what I am talking about here.
I can also say that the 18.75 kHz coil very much corrects this issue and so is a "must-have" for anyone wanting to go after gold with the X-Terra 50. It not only brings the target id back up to where it should be in mineralized ground, but it strongly boosts the signal on tiny gold. My two grain nugget only signals on the 7.5 kHz coil if rubbed on it, and it bounces into iron. It signals nicely through my test rock with a non-ferrous id of 3 with the 18.75 kHz coil. The higher frequency coil should greatly reduce the tendency of small items to bounce into iron, and some small items to just plain read as iron!
There may be some loss of depth on coins with the higher freq coil. I do not care for my uses. For me the 18.75 kHz coil is the only coil I am likely to be using on my X-Terra 50 going forward. You other guys can figure out for me what I'll be giving up on coins as it is probably more important to you.
Well, in closing I must say I continue to be pleased with my X-Terra 50. Now the more so as the new coil does make a substantial difference in my own area of particular interest
Good luck with the 50.