10) Can my MXT tell the difference between coins or gold rings and pull tabs or other trash?

No discrimination system on any detector is perfect. There are always tradeoffs in any target ID system design, and although the MXT ID system is as good as any available today, it can be fooled and it cannot always differentiate between some types of targets and some types of trash. The discrimination readings are influenced principally by the target shape, size and conductivity of the metal. As an example, nickels, some pull tabs and rings all appear the same to VLF type metal detector’s ID systems. Most men's wedding bands and ladies gold rings read in the 10 to 30 range in my soils. The lower end of that range includes junk foil, and the upper end includes many types of pull tabs and cut up bits of aluminum cans. Larger men’s rings and "class" type rings usually read in the 30 to 53 range – same as the square pull tabs. Nickels usually read in the 18 to 22 range in my area soils, but there are exceptions. Some oval shaped pull tabs read consistently in the nickel range - but I find near surface nickels sound "sharper" and pinpoint tighter (smaller) than pull tabs. Silver rings are usually not ignored by detectors as they usually read in the dime to quarter range. Certainly when you hit a target with a VDI number between 30 to 55 it is almost always going to be a square pull tab or aluminum screw cap, but not always - once in a while those targets might be a large gold ring and you would be losing a potential great find. You just can’t get around it - if you ignore the targets in that VDI range, you are ignoring some nickels and rings as well as those pain in the neck pull tabs. Turn up the discrimination too high and you will miss gold rings. However, in some very trashy areas, you can dig 10,000 pop tops and pull tabs to every gold ring. If that’s worth it to you go for it - its your decision. The key for me has been deciding what I will do based in my location. Picnic areas in parks are overloaded with pull tabs, but not as many rings. Sports fields have more rings and usually fewer pull tabs. I recommend choosing yourself, based on the type of site, when you will or will not dig all targets in the pull tab range. In sites which have been abandoned since  before the pull tabs came out (in the early 1960’s) you want to be sure to dig any signals in that range, because there should be few and there is a significant chance of a valuable target. The following chart gives VDI ranges for some typical targets (a chart like this should have been in the MXT user’s manual in my opinion). Degrees of corrosion, soil iron, nearby junk and other factors affect the VDI readings, so these are not carved in stone, but will give you a good idea of what you might find in each range.

VDI Range	Some Possible Targets found in this VDI Range:
-95 to - 20	Antique iron relics, Iron nails, rusty iron junk, hot rocks
-20 to 0	Small gold nuggets, gold earrings, gold chains, small bits of iron, gum wrappers, small bits of foil
0 to 15	Platinum rings, smallest gold rings, gold earrings, gold nuggets, sterling chains, larger foil pieces, gum wrappers, bits of chopped aluminum cans
15 to 30	Most gold rings, Gold nuggets, Gold $1, Nickels, oval pull tabs, bent tabs, bits of chopped aluminum cans, zipper tabs
30 to 45	Largest gold rings, larger gold nuggets, Gold $2.50, Copper Nickel cents (1856 to 1864), Silver War Nickels, most square pull tabs, iron bottle caps, small aluminum screw caps, Costume jewelry
45 to 60	Gold $5, Corroded zinc cents, 3 cent silver, zinc pot metal junk, costume jewelry, brass keys, small aluminum screw caps
60 to 70	Indian Head Cents, small sterling earrings, zinc cents, hot wheels cars, larger aluminum screw caps
70 to 78	Gold $10, modern copper cents, half cents, two cent pieces, small sterling rings and sterling jewelry, hot wheels cars
79 to 81	Gold $20, sterling silver rings, clad or silver dimes
82 to 88	Clad or silver quarters, heavy sterling silver rings, Sacajewea "golden" dollars, SB Anthony dollars, buried brass sprinkler heads
89 to 92	Clad or silver halves, large cents, buried brass sprinkler heads
93 to 94	Clad Eisenhower or silver dollars, large copper pipes

11) My MXT is noisy in wet sand on saltwater beaches. How can I improve its performance?

On dry sand, there should be no problems. There can be noise and chatter issues in wet sand and with the head underwater. On a low mineral beach soil, the MXT may operate just fine in wet sand. However, on beaches with significant iron content, the MXT must adjust both for any iron sand or rocks in the soil, as well as the salt. Unfortunately, black sand and salt balance out on opposite ends of the scale, so it is hard to adjust for both at the same time. The standard 950 concentric coil is fairly sensitive to mineralization. If there is any iron, any variance in conductive soil moisture, or if the coil head actually goes under water, this will cause the coil to make lots of noise. The ground balancing switch needs to be set in the "salt" mode for these conditions, but most users find they also need to switch to one of the DD coils to get the best results on the wet sand when the sand has some iron mineralization present. The DD coils are less sensitive to the salt or iron mineralization than the standard 950 concentric. The last option in these conditions is to turn up the discrimination (usually not desirable since beaches are prime ring hunting areas and it is easy to lose potential finds turning up the discrimination too high) or to reduce the gain which still allows ring detection, but lower gain reduces the depth at which a target could be detected.

12) What happens if I turn the gain down below the recommended preset level?

The MXT is a high gain unit, made to be able to find small gold flakes. When you are just coin shooting, you can turn the gain down some (say to about 7-8) with no big problems if you are willing to blow off the deepest stuff (hey, you don’t need to worry about those 6 inch deep barber dimes when you are hunting at a school built in 1972 on a clean site). When you are new to the machine, try dropping the gain to 8 and then cranking the discrimination up to about 7 to eliminate most trash. You can increase the gain and lower the discrimination later as you get to know the machine better.

However, the deepest detection (of coins, etc) and the detection of the smallest objects (small nuggets, small earrings) require the highest gain. Unfortunately, the highest gain also means the greatest noise from the MXT. For ways to deal with that noise, see the noise question -#18 - below.

13) I took my MXT out and it was acting strangely. I noticed one of the switches had been bumped.

One thing I have noticed it that it is easy to accidentally bump a switch and change a setting while putting the MXT away or getting it out. Every time you take out your MXT and turn it on, check to see that all the switches and knobs are set exactly where you want them.

14) I was testing a target and it just disappeared. A few seconds later it was back. What gives?

When you are in automatic ground balance and making multiple passes over a target to ID it, be careful not to stall over the target and let the system track into the target and adjust the ground reading to include the target. This can give bad or unexpected results. The auto ground balance adjusts quickly and may adjust out a target faster than you might expect.

15) How can I tell what the mineralization level of my ground is? What does it mean?

Here is how to use your MXT to determine your relative level of soil mineralization. When you are out hunting, flip the MXT into prospecting mode when the coil is over some target-free soil. In the upper right hand corner there is a label, GND = 78 (or some other number). The ground reading number tells you what the MXT is seeing as far as soil mineralization. If your number is 30 to 50, you have low or no mineralization (lucky you!). Readings of 50 to 69 are found in moderately mineralized soil. A reading of 70 or over is highly mineralized soil. In general, highly mineralized soils are much harder to hunt in, often tend to have more hot rocks and as a result are noisy to hunt over. Some areas with moisture and a high alkali or salt content can cause their own set of problems. They read very low on the ground scale and give ground readings in the 20s. The MXT has a separate salt adjustment on the ground balance settings for work in these areas.

Soil mineralization that reads high on the ground scale is caused by iron minerals in the soil, and can have a very significant negative effect on the operation of your detector. Unfortunately for us detector operators, the earth's crust averages a little over 8% iron and some of us seem to have a just a bit more than our share! This is why all modern VLF type detectors have the ability to adjust and compensate for increased iron in the soil. The automatic adjustment the MXT makes to compensate for mineralization is not just a simple reduction of gain, but the net result of ground balancing to hunt in highly mineralized soil is reduced sensitivity. Reduced sensitivity means reduced target detection depth. The MXT (and all other VLF type detectors) will detect much deeper in dry sand that reads 40 on the MXT ground scale than it will in soil that reads in the low 80s. There are a number of factors that affect target detection depth, including soil density, soil moisture, salt content, and others. Soil mineralization is just one of these, but it is one that is common, and does have a significant effect. Here in the Reno, Nevada area, soils typically vary from the high 70s to low 80s.

16) My MXT wont get as much depth as others claim for it. Why?

This is actually a very complex question, as lots of factors can negatively affect detector depth. Iron mineralization in the soil is one of the most common, but soil moisture, soil salt content, soil density, and nearby power transmission lines can also affect depth. The settings on your detector and the strength of your batteries can also affect your depth of detection. The deepest depths are usually obtained in dry, non-mineralized sand (or with air tests - no soil at all!). To get the greatest depth, generally the gain must be at its highest setting, +3. The prospect mode of the MXT actually gets just a bit more depth than the other two operating modes. In all modes, deep signals are weaker and can take some experience to recognize. The bottom line is that many of the factors that determine depth, like mineralization, cannot be easily changed – they are characteristics of the site you are hunting. Learn to use your detector to the best of its capability, and you will get the best depth possible at that site with that equipment.

17) Sometimes I find "ghost" targets that disappear when I dig them. Why?

Luckily, ghost signals that are repeatable in more than one direction are not that common. So one good way to eliminate a lot of them is to test weak signals from more than one direction in an X pattern. This can eliminate a lot of unnecessary digging. Even so, ghost targets still occur once in a while. Because of its high gain, the MXT may be a bit more susceptible to these ghost targets than most detectors. Groups of a few small iron bits close together can sometimes cause these - when dug, the group is separated and the apparent target disappears. Tree roots with higher salt content than the soil can show up as good targets that are not really there as well.

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