Metal Detecting Article: "Quiet Detector's Operation vs. Finding Most Deep Targets"
Busting Myths About Metal Detector's Sensitivity, Discrimination and Depth
To conduct the most effective and comfortable search under "tough" metal detecting conditions - when the site is littered with junk, and/or the soil mineral content is high, one should find an optimal combination of settings - "golden medium", when it comes to "Quiet Detector's Operation vs. Detecting Most Deep Targets".
If the former can be improved by increasing Discrimination and running Sensitivity in AUTO, or decreasing Manual Sensitivity, the latter can be achieved by changing the levels of Discrimination and Manual Sensitivity in the opposite way.
Before going further, I want to make one thing clear: this article's title should not be read as "Quiet Detector Operation vs. Maximum Detection Depth".
It is important to understand that one CAN NOT increase the detector's TRANSMIT POWER (the strength of the emitted electromagnetic field), i.e. increase DETECTION DEPTH (also called DEPTH POTENTIAL), unless the detector is equipped with a specific control, such as, for example, the 'TX Power' setting on the XP Deus metal detector, for adjusting the Transmit Power.
Many enthusiasts believe that Sensitivity sets the detector's transmit power, and "More Sensitivity = More Detection Depth" as well as "Less Discrimination = More Detection Depth". However, these are huge MISCONCEPTIONS that have been formed from the common practice: if one cranks up the Sensitivity level, one starts receiving responses from deep targets, and the same happens when Discrimination is reduced. Moreover, the latter effect is employed to check ferrous properties of detected targets by means of the auxiliary Discrimination patterns (QuickMask in E-Trac and 2nd Discrim Pattern in CTX 3030) with least or no Discrimination. The correct explanations for both effects are simple and have nothing to do with the DETECTION DEPTH which, in fact, remains UNCHANGED when both effects are observed.
Sensitivity, as its name indicates, only determines the detector's ability to respond to the weakest electromagnetic fields generated by the conductive and ferromagnetic substances which may range from non-ferrous targets to clods of mineralized material in the ground (read more about Sensitivity on page 1 of my article - How To Search Around Cellar Holes Successfully). In other words, by increasing the Sensitivity level, you only instruct your metal detector to LET YOU HEAR more weak audio responses emitted by small and deep targets situated within the detector's actual DEPTH PENETRATION (see details in my article - "Detector's Depth Penetration and What Affects It").
In case of detecting with maximum Sensitivity on the high-mineralized ground, the detector is allowed to respond to the ground minerals, and the user hear lots of additional "noise" - the ground "clutter". Now the user hears anything but the small non-ferrous targets. Their weak responses, even when amplified by the 'Volume Gain", become masked by a mix of interferences such as the high-sensitivity circuit noise, iron falsing of any type including responses to partially rejected targets and, most of all, ground mineral effects including effects of natural magnetic mineralization - all being also INTENSIFIED.
Discrimination is controlled by a special filtering circuitry that intentionally blocks the detector's audio and/or visual responses to undesired metal objects beginning with metallic iron. By using the Discrimination control, you instruct your detector to LET YOU HEAR only responses from detected targets you want. Besides its major function - to sort out information related to Phase Shift - the duration of time a transmitted electromagnetic field is returned from a detected target to the search coil's receiver winding, Discrimination also filters out signals emitted by soil minerals. Altogether, that is a lot of filtering! (you may want to read more about negative effects of Discrimination in my article - "Less Discrimination Lets You Find More")
With the current search coil to be used for coin shooting, you can observe your detector's DEPTH POTENTIAL for coins only through conducting the Air Test (Bench Test). Under real metal detecting conditions, the OPERATIONAL DEPTH RANGE (Detecting Range) for coins will never surpass either the air test results or the detector's DEPTH PENETRATION, and may only approximate the Depth Penetration if you detect on neutral or low-mineralized ground, provided that the coins have been buried and undisturbed for very long periods of time. In regards to various ground mineral contents, you will always be dealing with your detector's DEPTH PENETRATION ability (see details on factors that negatively affect the metal detector's depth penetration ability in my article "How To Avoid Reduction of Your Detector's Depth Penetration").
The amount of Discrimination to be utilized for detecting coins under any particular search conditions should be considered based on what a user would like to find rather than what should be rejected.
If you decrease the Discrimination level, you will hear more "noise" but it will consist of mostly TRUE signals (in Auto Sensitivity) emitted by the targets now being accepted. If you switch to Manual Sensitivity and increase it to a level greater than the value of the 'Suggested' Sensitivity (page 55 of the E-Trac Instruction Manual, page 21 of the CTX-3030 Instruction Manual), you will receive not only a few more true signals, but also zillions of FALSE signals and ground "chatter", especially with Manual Sensitivity being set to the max.
Doing both, decreasing Discrimination and increasing Manual Sensitivity, may cause an audio-mix of all kinds of sounds - beeps and bleeps, blurps and squeaks, grunts and blaats, chirps, etc. High mineralization and/or heavy iron junk, if present in the ground, may be the major causes for the "sound bedlam", and, therefore, can not be ignored.
Of course, there are quite a few enthusiasts who utilize Maximum Manual Sensitivity and are not bothered (as they claim) by their detectors' noisy operation. To get the maximum operational depth ranges out of E-Tracs and CTX-3030s, these "rebels" run their metal detectors hot utilizing both Manual Sensitivity set on maximum, and no Discrimination - in All Metal mode (the Smartfind window is all white).
Unless these enthusiasts hunt on neutral or low-mineralized ground, it is hard to believe that they do not suffer from cacophony of false signals. This leads to missing a lot of valuable targets because the human brain becomes insensitive to slight variations in sound tones just after one hour of continuous "noise attack". After a few hours of the excessive "auditory torture", one becomes desensitized to the "iffy" signals (deep silver) and unable even to separate one tone from another.
Such an extreme way of reaching down to deeper targets also makes the E-Trac's powerful tool - Multi-Tone Audio in Conductive sounds, useless. To avoid the cacophony of false responses of various tones, the Multi-Tone Conduct Audio is then replaced by the 2-Tone Ferrous (Two Tone Ferrous, TTF). Most TTF search programs utilize both the high levels of Manual Sensitivity and almost no Discrimination. But these TTF programs can be effective only if 1) used by an experienced detectorist, 2) used at the metal detecting sites with least mineralization, and 3) the "wrap around effect" (explained on page 2 of my E-Trac field-test report) is eliminated. Otherwise, after an hour of operating in TTF, your brain gets affected the same way as described above.
On the CTX-3030, the noise problem can be partially solved by utilizing Combined Audio, RESIZE the TONE PROFILE, CHANGE PITCH, Ferrous-Coin Separation and Ground-Coin Separation (all these features are explained on the following pages). With implementation of these features on the CTX-3030, the TTF search program has gone up to a new level allowing the users a greater ability in isolating targets. Plus, the CTX-3030's "Smart" coils allow for setting the Manual Sensitivity to higher levels than on the E-TRAC without causing too many false signals. And, as I mentioned above, the CTX 3030's graphic target representation makes up for the detector's noisy performance.
I prefer to hear least iron- and ground-falsing not to miss the true coin signals and their fragments in order to "catch" both the partially masked and deeply buried coins at the trashed sites. This is why I seldom use Manual Sensitivity (read more details on page 3), and never at its high levels. For my Level-3 program settings - a TTF-type search program, I use AUTO Sensitivity because of high mineral content in soil. And I use my TTF program only after I finish cleaning the site of all medium-to-large-sized iron objects using the Level-1 and Level-2 search programs if needed. This way I keep my detector's operation less noisy and with stable audio Threshold.
In my experience with Minelab FBS metal detectors, decreasing Discrimination has been proved as the most practical and effective approach to increasing E-Trac's and CTX 3030's ability to recognize more deep and small coins. Some enthusiasts may disagree with my point of view, but it is fine with me because they most likely hunt on NEUTRAL grounds, and I deal with high mineralization.
We quite naturally may form wrong ideas from our various metal detecting experiences or when being influenced by opinions of other enthusiasts. The above-mentioned cases of Sensitivity and Discrimination are good examples of how these two detector's key-features can be misunderstood and misused to the point that more harm than good can be done.
And finally, when you metal detect at the site of the former settlement or homestead, try to follow this simple principle of searching: as you gradually reduce an amount of both non-ferrous and ferrous targets in the ground, and you unintentionally break the Halo Effects of some rejected iron objects while actually digging up other targets, you need to change some settings in your search program along with the Discrimination pattern accordingly.
In other words, it is not wise to "pound" a good metal detecting site over and over using the same program settings and high discrimination. For instance, when inexperienced detectorists stop receiving good signals while hunting at any given metal detecting site, they think that they have depleted the site of all goodies, but in fact, they just prepared the area for upcoming skilled hunters who will sure reap the best fruits.
My 3-level search program for Minelab E-Trac and CTX 3030 allows me to quickly implement appropriate program settings without many additional adjustments when the metal detecting conditions change. In the Level-1 program description starting on next page, I give detailed explanations of each setting's level or mode, and how certain settings interact with one another. I hope my input will help you figure out the "golden medium".
