Iron Stained Gold And Hammered Coin Settings MXT

[auminesweeper]

Years ago Steve Told me about NOT setting the Disc above 2 when using the Relic Mode for Prospecting, But I have found that his settings also Applies to Hunting Roman and Hammered coins too, As I was setting the DISC at 2.8-2.9 although I did have a lot of success, It seems that I can find those coins within the first 4 to 6 inches and A lot of Targets can be Missed because after that they send back an Iron signal when in the Ground yet in air test they send a good signal up to a foot - 13".

I have found that either roughly setting it at 2 works Ok or as A Test piece to Calibrate it Properly as all Machines can  Vary even from the same factory from Coils to Battery Power Etc, For you people who  Are World Travellers and come over here to go Detecting, If you Get A New UK 5 pence piece and set your Disc up to the point where your machine (what ever Brand) tells you its junk then Back off the DISC so the Machine now makes it sound like a good signal That is the point you need to be Set At,

There is a Risk that you might dig a bit more Iron, But a fair bit of it will signal as Iron,

This way of setting the Machine will work for Gold Prospecting Too even more so if you have Nuggets with Iron Staining, Because it is low enough to allow the purities of the gold to come through which is also useful when searching for those elusive Tiny Gold Staters over here, and by using that 5 pence setting Nails with give an Iron signal one way and at 90 degrees they give a clear signal,

My Settings on the MXT's  were always 2.8 to 2.9 but using this method they are now at 1.7 - 2.2, It does not sound like much of an adjustment But Believe me it makes a heck of A lot of Difference, Like Small Gold to find Tiny Hammered Coins you have to dig a certain Amount of Trash and over here with 4 or 5000 years of metal workings we have our share of ferrous junk,

This is the Coin In Question

Hope this Helps,, john  

[Steve Herschbach]

Good post John, thanks.

A setting of two was always sort of a default "max" setting for me but it is a very fuzzy setting. If people ask these days I say 1.5 - 2.0.

The borderline between ferrous and non-ferrous overlaps. A lower setting gets most all the non-ferrous but will give false positives on quite a bit of ferrous stuff also. A high setting will eliminate nearly all ferrous but also quite a few non-ferrous targets.

The mix is solely dependent on the ground mineralization and the type and number of ferrous and non-ferrous targets in the ground. The coil type is critical. A concentric coil has a different ferrous response than a DD coil for instance that is very dependent again on the level of ground mineralization. That is why it is dangerous to fall into the habit of using any particular setting, though I have been plenty guilty of that myself.

Best practice is to always set a disc control very low and if you find yourself digging too many ferrous items slowly tweak it upwards. If you are hardly digging any ferrous than go lower. Too many people hate digging any ferrous targets at all and if you set to eliminate all ferrous it is 100% for sure that you are passing on many good targets.

The display on the Garrett AT Gold shows the overlap very well. A setting of 30 gets most of the gold but also has you digging some ferrous. 50 eliminates most of the ferrous but misses a lot of gold. 40 is a default average setting. But again, it totally depends on the mineralization and target mix. In high mineral ground with small gold a setting of 40 may miss nearly all the gold but calling it ferrous.

This also highlights how many newer detectors are using expanded ferrous ranges to allow for better target resolution. The MXT has a very narrow and finicky ferrous range to work with.

Of course many people would just say dig it all. But that is easier to say than do in the middle of an old mining camp or a field in Europe.

[Steve Herschbach]

Another well illustrated example is for the Minelab X-Terra 705 Iron Mask, which also uses a 20 point overlap.

[auminesweeper]

I see what you mean by the Over lap now. Thanks for That.

 

So I re Tested the Coin and there is another problem, At 2 it Makes an Iron sound But at about 1.5/1.4 Down to 0.9 , IT then Makes A Hot Rock Sound but Lower than 0.9 it will Bleep and then I found Problem Number TWO.

 

Have you Ever Found A Nail that your detector wont Pick Up ?? well I just did, even In the Relic Mode at High Gain  ( pre Set ) on the MXT and no Matter where the Disc was set, and when I switched to Prospect  and turned it up flat out gives a soft sound Like A Hot Rock, Baring in Mind that for some reason this MXT with the Whites 10" DD can Pick up my Bare Hand at 6 Inches in the prospect mode and it will Bleep on it at 2 inches in the relic mode.

 

The GMT could only pick it up at 4 to 5 inches But it was giving a Target type sound,  This Nail is 1-11/16ths long

These Nails are used for Cladding and Double Glazing etc, Something is going on here??

.

[Steve Herschbach]

Try manually varying the ground balance on the GMT both up and down and see if it changes anything.

[auminesweeper]

Ok, Right In the Relic Mode the MXT will just pick it up if the Gain is turned up as far as it will go and Only if it is within an Inch of the Coil, But any more than that and the signal turns to a Hot rock sound and it soon Fades within 2 inches and at 4 inches it has Gone, I tried the GB at 83 and 50 and it made no Difference,

In the Prospect Mode it sounds Like A Hot Rock until the V-Sat is above 7 and in Hyper Sat it sounds like A Target.

With the GMT Changing the GB did not work from 50 and 59 to 71 etc it gave the same signal at all setting, at 4"-3/8ths of an inch or 110mm the Zip Zip was all but Gone, But the Iron meter said it was 25%, And my Bullseye II running at 36khz will Only pick it up at 3/16ths of an inch, that's a new probe with new Duracell 9v in it,

This is A New one On me,,, john

PS, on the GMT with a GB of 00 the signal dropped to 2 inches and at 99 it went up to 6 inches.

[Steve Herschbach]

Well, it is something to do with the composition of the steel. Stainless steel for instance is difficult for detectors due to having both poor conductivity and low magnetic properties. This being a hardened steel something similar is going on.

I had you check the ground balance to see if the metal was acting similarly to mineralized ground and being balanced out to some degree. Could be all of the above but by definition metal detectors pick up highly conductive or items with high magnetic permeability so this screw lacks both those properties.

[auminesweeper]

Well, it is something to do with the composition of the steel. Stainless steel for instance is difficult for detectors due to having both poor conductivity and low magnetic properties. This being a hardened steel something similar is going on.

I had you check the ground balance to see if the metal was acting similarly to mineralized ground and being balanced out to some degree. Could be all of the above but by definition metal detectors pick up highly conductive or items with high magnetic permeability so this screw lacks both those properties.

Well I am Glad you did Steve, Because just when I was feeling over confident about how I use my machines this proves that Discrimination whether it be Machine made Or Man made We should never take Our Settings for granted,

I just tested a Rusty Nail the same size but a 1/4 of an inch longer holding it east to west the MXT gave a good signal at 10-1/4 inches or 260mm.

What this all proves is what you said way back and how Critical the Disc setting becomes if you use this Mode for Prospecting or where other High Value Items are at risk of being over Looked.

Thanks Steve,,

John