E-trac Noise Cancel TID shift?

E-TRAC NOISE CANCEL TARGET ID SHIFT?

I posted this on another forum, but others there may not have encountered these shifts.

The reason for this post is for further understanding of manual Noise Cancel and its other possible uses. Much of the info is based on personal experiences with Noise Cancel, and other parts are based on air-tests and speculation. The Noise Cancel function must be quite good, because the GPX 5000 has 256 of them. Perhaps a better understanding of this function might allow a detectorist to optimize the E-trac for specialized hunting (small gold jewelry at beaches, hunting sites with high levels of surface mineralization, high iron trash sites, and perhaps even shallow sub-gram nugget hunting.)

While saltw@ter shoreline detecting, got a strong 12-46, similar to a quarter. Turned out to be a copper penny with a black mud-like coating. While air-testing it using the Sunray target probe, I lowered the Noise Cancel (NC) number from 11 down to 1, one number at a time. The target ID value gradually changed from 12-46 down to 12-42/43, as did the tone. From this, guessed that there’s a slight change in tone and target ID values between the different NC numbers.

To try to understand this Noise Cancel number target ID shift, I air-tested some coins with NC #1 and NC #11 using the Pro coil, the SEF 4.5”x7” coil, the Minelab 8” coil, and the Sunray target probe, with auto sensitivity = 16.

COIL_____|_  _  PRO_COIL_  __||  MINELAB 8” COIL  ||  SEF 4.5”x7” COIL ||SUNRAY TARGET_PROBE|
NC_#_____|__ 01__  |__ 11_  _||___01____|___11____||___01____|___11____||___01____|___11____|
Half dol.|  09-47  |  09-47  ||  09-47  |  09-46  ||  08-46  |  01-49  ||  11-46  | 03/04-49|  
Quarter  |  12-46  |  11-47  ||  12-46  |  12-46  ||  12-46  |  05-49  ||  12-46  |  09-48  |
Dime     |  12-44  |  12-44  ||  12-44  |  12-44  ||  12-44  |  13-47  ||  12-43  |  13-46  |
Penny    | 12-42/43|  12-43  || 12-42/43|  12-43  ||  12-42  |  13-45  ||  12-42  |  13-45  |
Nickel___|  12-13_ |  12-13 _||_12-12/13|__12-13__||_ 12-13__|__12-15__||_ 12-13__|__12-14__|

The NC number appears to affect the high conductive targets’ ID values more than the low conductors.

The air-tests of the Pro coil and the 8” coil (both are Minelab) shows very little change in target ID values, but in ground, quarters read up to 48 on both coils with NC#11. Nickels usually read as high as 15 in the ground, but I did find one buffalo nickel that read 18. Saltw@ter corroded and severely worn down V-nickels and buffalo nickels read as low as 09, and modern nickels in a high iron rust beach area read as high as 35-17. (All readings using the Pro coil).

Both the 4.5”x7” coil and the Sunray target probe show the biggest NC number shift in target ID values during air-tests. The 4.5”x7” coil has the largest overall shift on both low and high conductive targets. The ID values shift exactly 3 points for all coins except for the nickel, which shifts only 2 points. This implies the shift becomes less as the ID value decreases.


A CHART OF THE NC NUMBER SHIFT IN TARGET ID VALUES, BASED ON THE 4.5”x7” COIL TEST

       1      5       10      15      20      25      30      35      40     45      50
NC#11  |______|_______|_______|_______|_______|_______|_______|_______|______|_______|
                                                                                    |
        1       5       10      15      20       25      30     35      40      45     50
NC#06   |_______|_______|_______|_______|________|_______|______|____ __|_______|______|

         1        5       10      15      20       25      30     35       40      45     50
NC#01    |_ ______|_______|_______|_______|________|_______|______|____ ___|_______|______|
                                                                                    |
                                                                                  quarter

The quarter is lined up at both NC#01 at 46 and NC#11 at 49.

This part is based on the chart above, and is purely speculative.
NC#11 at conductivity value 1, there may be a slight shift to the left (conductivity value slightly less than 1) as compared to NC#06, and more so NC#01. This may allow NC#11 to be more sensitivity to very low conductive small targets, but also to tiny low conductive junk on the ground surface.
NC#01 shifted slightly to the right of NC#06, may allow NC#01 to be less sensitive to very small low conductive targets at the surface, allowing better penetration when the ground is littered with tiny, noisy surface junk. (which NC#11 is more sensitive to).
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Earthmansurfer pointed out the possibility that a slower sampling rate on the lower NC numbers might be used to make the E-trac less sensitive to mineralization. That would mean that a slower sweep speed may be required for the lower NC numbers to detect very small low conductors. That may be why European detectorists like to use NC numbers 2-4 to hunt for small hammered coins.

Using mainly NC#11 while beach hunting, I can usually sweep moderate to fast and still detect small, low conductive non-ferrous targets. In the past when hunting with NC#2 with the same sweep speed as NC#11, sometimes I’d get a broken signal from a dime near the surface. And only when lowering the sweep speed would the target come in loud and clear. NC#11 always gets such targets. I don’t know if it’s because of the possibility of a slower sampling rate.

I believe that understanding which conditions to use the lower NC numbers and what sweep speed to use to locate desired targets is very important. Also which conditions to use the higher NC numbers and what sweep speed to use to locate desired targets would further optimize the E-trac’s capabilities.
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The Auto Noise Cancel function does have it’s merits. When other nearby detectors cause interference, or when some other Electro-Magnetic Interference requires it. Just do an Auto Noise Cancel as described in the User Manual.

But, it’s also possible to Noise Cancel out ironstones, and perhaps patches of mineralization. At a saltwater shoreline location, I was able to detect quite a few old silver coins at extreme depth. Auto +3 ran as high as 26, and I ran manual sensitivity at 29. The threshold was very smooth, but periodically, a 01-50 kept popping up. Eventually, I decided to locate one of those 01-50 signals. It turned out to be a large stone. It was detectable with both the Pro coil and the Sunray target probe, but only when the coil was very close to the rock when using high manual sensitivity. I even moved the rock to a different location and had the same results. In an area clean of other targets (including iron), I did an Auto Noise Cancel a couple of inches above the large stone. After that, no more 01-50 signals in that area. I think that the NC number switched from 11 down to either 5 or 8.
From this, I think it may be possible to use Auto Noise Cancel to cancel out some noisy ground. First, while using an all-metal pattern, locate a 1 square meter patch of target free ground. Then, use the Noise Cancel procedure a couple of inches (instead of 12 inches) above the patch. I know this works for ironstone (not magnetite rock), but don’t know for sure if it works on badly mineralized ground.
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White’s detector scale is from -95 to +95. Soil comes in at around -92 to -94. Iron is generally from -95 up to 0. Salt comes in at around 06. Hot rocks comes in at +95, but on the E-trac, it’s mapped in at 01-34 and 01-50. Trying to relate the White’s detector scale to the E-trac’s 01-50 conductivity scale may give a better understanding to this possible ID shift.

It would be nice to know that if there is a target ID shift (in ground) based on the Noise Cancel number, how this shift would relate to the White’s detector scale, and how it could be used to an E-trac detectorists advantage. I’m hoping others have experienced this possible shift and have learned how to use it to their advantage. And hoping that these air-test results aren’t from faulty coils (4.5”x7” and the Sunray target probe).

Perhaps you are onto something and perhaps not my first question is are these changes stable from area to area or do they change when you change areas...if so probably do more testing than hunting or carry a notebook for each area or particuliar coil which could become mind boggling at best.

Heck just noise cancel when I start hunting and if the ground color changes or my unit becomes unstable do another and move on and always said an Explorer for one can be as easy or hard as you want it to be.

Tip of the hat for your thoughts and again you indeed may be onto something as one can never know enough relative the hobby or its tools but k.i.s.s. may or maynot be applicable...

Nice post. Thorough/comprehensive.

Dan-Pa. Wrote:
-------------------------------------------------------
> Perhaps you are onto something and perhaps not my
> first question is are these changes stable from
> area to area or do they change when you change
> areas...if so probably do more testing than
> hunting or carry a notebook for each area or
> particuliar coil which could become mind boggling
> at best.
>
> Heck just noise cancel when I start hunting and if
> the ground color changes or my unit becomes
> unstable do another and move on and always said an
> Explorer for one can be as easy or hard as you
> want it to be.
>
> Tip of the hat for your thoughts and again you
> indeed may be onto something as one can never know
> enough relative the hobby or its tools but
> k.i.s.s. may or maynot be applicable...

The saltw@ter beach where I micro-jewelry hunt using Noise Cancel (NC) #11 is generally not stable. The threshold is more often off than on much of the time, and there is quite a bit of falsing when you don’t use very smooth, very level sweeps. The beach is high in rust, high in iron, high in black sand, and has magnetite rocks. NC #11 is very sensitive to magnetite rock and patches of mineralization, and registers 01-50 very often there. In some areas, almost constantly. But a single discrimination dot a 01-50 cuts most of that noise down considerably.

From quite a few air-tests of very low conductive gold, 12-01 up to 12-03, it appeared that NC #11 is the most sensitive to small gold. The saltw@ter beach where I hunt has produced over 40 gold items in the last 6 months, most of it in the 12-01 to 12-04 range. Most of this low conductive gold reads 35-01 to 35-04 in the mineralized wet sand (very high ferrous readings).

I’ve found sub-gram gold rings with the SEF 18x15 coil, the Pro coil and the Minelab 8” coil.
I was hoping that other E-trac detectorists with non-Minelab coils have noticed a Target ID shift based on the Noise Cancel #. And if so, have found ways of utilizing it for specific target hunting. European detectorists like to use the lower NC numbers (2-4) to hunt for hammered coins. If the precise reasons for using specific NC numbers for specific target hunting were available, it would help other detectorists hunting for similar targets in similar ground conditions.

A tip of the hat for your efforts and perhaps knowing the intelligent guys that use the forum imagine one of them can add their expertise as it certainly does have merits and possibilities and indeed you may be onto something that will further enhance your hunting abilities and thanks for sharing....as indeed it may help other members also....