Basic Operations of the MXT Metal Detector


Basic Operations of the MXT

The users manual is a very good guide to the basic operations of the MXT, and though this section will duplicate some of that information, I want to include some material that goes into additional detail or applies to situations other that the "normal" conditions addressed in the manual. This section is not intended to replace the owners manual, but to supplant it and provide some additional information.

I).VLF (induction balance) detectors -
One detail the manual does not cover is a basic introduction on how VLF (induction balance) machines work. To put it in the simplest terms, each coil head on a VLF detector actually contains two coil loops, a "transmit" loop and a "receive" loop. The detector puts out an alternating current through the transmit loop which creates a magnetic field that goes through the soil.  The rate of this alternating back and forth is measured in kHtz (thousands of cyclings per second) and significantly affects how various targets respond. The MXT operates at 13.889 kHz. That means that it sends a signal into the ground 13,889 times per second. The "receive" coil measures the magnetic field effects created by the transmit coil in the soil. In target free soils, the receive coil sees the magnetic effects of any natural iron minerals or other conductive elements like salt in the soil.  If a conductive object like a coin or gold nugget is present near the transmit coil, it will have a current induced into it. This induced alternating current will produce its own magnetic field, which the receive coil will see as a change in the magnetic properties of the soil under it. These natural soil responses are usually far greater than the target response, but the detector can notice the small change in magnetic fields caused by the target. When the detector sees this field change, information about the target is collected and analyzed by the MXT's computer software. The results of this analysis are output to the operator as an audio tone and displayed as information on the detector's screen. The tone and display output are different information and tell different aspects about the target. If you are interested in learning more about the basics of VLF (induction balance) detectors, you can find it by CLICKING HERE at White's company web site. The site includes a comparison to PI (pulse induction) detectors as well. You can also find the report of the engineer who designed the MXT, and his comments about its design and operations on the White's company website by CLICKING HERE.

2). Knobs and adjustments of the MXT -
The MXT operators manual provides a good overview and explanation of how the knobs work, and their impact on the MXT's operations. I don't want to make too large an effort to duplicate that information, there does not seem to be much point in doing so. You can read the operators manual, and if you are a new MXT owner, you really should. Instead, I would like to focus on some general comments about the information in the MXT Operators manual, and answer some of the "why" questions to help understand when you might make certain adjustments.

First, many of the suggestions in the MXT owners manual are based on the assumption that good targets sink deep, shallow ones are more likely trash. In many areas of the USA, this is a good guideline, but it is not always true. Remember that nearly all deep targets were once shallow and that there are reasons (like re-grading) that may bring old targets near to the surface. There are also a  variety of reasons why good near surface targets might appear "iffy".

Modes: Coin, Relic, Prospect - The three modes are actually preset programs where the MXT has been "tuned" for that particular use. That may well be true, but there are many situations where one might want to use other modes for certain purposes. As an example, when prospecting in areas with large quantities of iron trash, one might well choose to use relic mode for prospecting. To get the most out of your MXT, you must be open to using whatever mode is the best one for your particular application, in spite of what a particular program is called. Each mode has its advantages. Prospecting mode is a bit more sensitive than the other two. Coin and jewelry is the most stable. Relic mode offers a two tone detecting system.

Gain -
This knob controls the amplification of the response received by the coil from the target. The gain does not amplify loudness of the sound produced by the MXT, in fact the MXT has no volume control in the normal sense. This is why most folks use a good set of set of headphones with their MXT. Increasing the gain will allow the MXT to detect deeper and smaller targets, however it will also increase the response to hot rocks. This can potentially lead to noisy and unstable operations, so gain is adjusted to a point where it is as high as possible while the unit remains fairly stable.
For more detailed information on the maximizing gain while limiting noise and keeping the MXT stable, see the MXT FAQ section.

The Dual setting Knob (Discrimination and SAT) -
A) Discrimination (Coin & Relic Modes):
  The discrimination knob sets what makes a sound on the MXT audio (disc. does not affect what shows up on the MXT visual screen). The MXT has a true zero discrimination when the disc knob is set to 0.
Most of the range of discrimination adjustable on the MXT is mostly in the low VDI target range. Most iron drops easily out using the notch discrimination in coin mode. The MXT video actually says that you CAN discriminate out zinc cents, but that is simply not true, the MAX disc. goes only to about VDI readings in the high 50s (un-corroded Zinc Cents read in the low 60's to low 70's). Use of discrimination can be a two edged sword - it can both save time in digging trash targets, or cost you a fine diamond and gold ring you would have found had you not used discrimination. For further comments on the MXT's identification system (VDI) and discrimination in general, see the MXT FAQ section.

B) SAT (Self Adjusting Threshold (Prospecting Mode):  In prospecting mode, this knob adjusts speed at which MXT re-adjusts the threshold tone. As the iron content of the soil changes, the threshold (base) response changes as well. In highly mineralized areas, where gold is often found, the amount of iron present can change very rapidly. This can result in very noisy operations, or a situation where the user must readjust the ground balance every few steps. VLF machines which have automatic ground balance are able to readjust the threshold level - in White's machines this is called a self adjusting threshold. The MXT has the ability to adjust the frequency at which the threshold level is adjusted. Increasing the frequency at which the MXT readjusts the threshold level has the effect to help smooth out operations and increase stability.

Threshold - The threshold adjusts the "base" or background noise level. To get maximum performance from your MXT on faint or deep targets, most users will adjust the threshold to what is called "the edge of sound". This is the point where the MXT makes a slight audible hum at all times. It does not need to be loud or annoying, but just hearable.  Some folks can't stand any hum, and they will back the threshold down to just below the hearable level. Be sure that if you use the silent threshold method, that you only reduce the threshold just a hair below the hearable level - if you reduce it too far, you may loose targets.

Ground Balance Selection - The ground balance selection has the choice of salt, lock, and ground. This selection chooses how the ground balance portion of the detector program operates. Most users will be operating in the standard ground mode the majority of the time. In this mode the ground balance part of the detector's program operates normally and tracks the soil response and adjusts accordingly. In the lock mode, the ground balance system stops adjusting the ground balance setting. The detector keeps tracking the soil iron content, so if you flip the switch from lock over to ground, the MXT is already at the right setting. Salt is used in salt water and alkali soil environments. conductive salt soils ground balance at the opposite end of the scale from iron, so a special salt setting is needed for them.

3). Getting the most from your MXT -
The MXT is easy to use - so yes, you can just turn it on and go. The Owners manual has a great quick guide to operation of the MXT, so be sure to read it. However, it takes some adjustments to get MXT's optimum performance, because the recommended "pre-set" levels are not always the optimum settings for working a particular site. This section is my slow guide to MXT operations – how you might want to set the knobs under certain situations to get the best results. The section below is not really intended as a guide as to how to work certain types of sites, but mostly as hints on how to use the MXT to its optimum level. For more detailed site information, including my comments and experiences working with the MXT, see the part of this site called
Site Specific Hunting Experiences With the MXT
The characteristics of any individual site can vary and the suggestions below are generalizations of what you might find. They are my opinions and are not carved in stone, but I hope that from these examples you can get a better feel for how to adjust your MXT and get the most out of it in all situations.

Open Parks and Ballfields - To get the good stuff here, you will want to be hunting deep, so use as a high a gain as you comfortably can. Try to tolerate some noise, and cover a maximum surface area.

Trashy sites - At extremely trashy sites, I like to use of Relic mode and small coils to sort between trash and good targets. Depending on what may be deep, I sometimes raise the gain beyond the recommended setting.

Beach huntingTo detect deep or small gold items, I like to set the gain as high as possible, and the disc not too high. Set gain at the max the area sand and soil will handle.

Nugget shooting - This is another place where you want to use the maximum gain to detect small gold. Set gain at the max the area soil will handle.

Cherry Picking surface coins - Set the gain down to about 7 or 8. This type of hunting can be very useful at times, like in new parks built on previously unoccupied sites. In this mode you are saying - who cares what is deep, I want those easy coins - it works well in some places!

Skiing/Sledding SitesThis is a good place to go hunting for small gold items like earrings and pendants with the MXT. When going for small gold items, I like to set the gain as high as possible, and the disc not too high, but you have to balance that with the amount of trash present.

Relic Search - Ghost towns, civil war sites, etc. - For trashy areas, a small DD coil to pick among the trash for the good stuff. For areas with sparse targets widely dispersed, you can look for maximum depth and area coverage with a big coil, set for the max gain for the ground conditions. Zero discrimination if you want iron too. Very low discrimination may help eliminate very small bits of rusty iron and soil mineralization, which in many locations are not of interest to collectors, while larger iron objects may well be of interest.




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