Sensitivity is typically thought of as the level of response that a detector has to a target. And if that were the case, what you said would be true. But the receive circuitry of a detector also responds to the the ground surrounding the target, atmospheric conditions, electronic signals and radio waves. If any of those things cause the detector to become unstable, then you are actually defeating the purpose of cranking up the Sensitivity. When you crank it up, you actually intensify those "ill effects". As a matter of fact, in those situations, you will likely be able to increase the depth of detection by lowering the Sensitivity to a point where those "outside forces" are not effecting the target signal.
One of the simplest ways for me to explain it would be to use the old analogy of driving in fog. If more is better (as you indicate with Sensitivity) then wouldn't it be better to drive with the high beams on in fog? Of course not, as much of the light from the high beams will be reflected back into your line of sight. In foggy conditions, you can see much farther down the road with low beams. Similarly, if you run with too much Sensitivity, the signal you are sending into the ground will bounce off of mineralization and adjacent targets, causing a loss of detection capabilities. Not to mention increasing the adverse effects of those atmospheric conditions, electronic signals and radio waves interfering with the audio tones. Turn down the Sensitivity at those sites and you will actually increase the depth of detection just as using low beams allow you to "see farther down the road" in fog.
With the X-TERRA, I recommend holding the coil steady above a spot of ground with no metal under the coil......... Noise Cancel first, to allow the X-TERRA to chose the optimum noise channel. Then turn the Sensitivity up until you hear a slight chatter.......... then back it off until the chatter just goes away. If you don't hear any chatter running at max, keep it there and hunt. But don't forget to check the Sensitivity during the hunt. Many things can change as you wander across that field. It may remain "quiet" or it may get noisy. If it gets noisier, you need to turn it down a bit. The objective is to maintain a setting where it is maximized, yet stable.
You mentioned automatic sensitivity........ The software of the E-TRAC constantly monitors the conditions, adjusting the three channels of Sensitivity in an effort to mazimize depth of detection while (at the same time) minimizing the adverse effects of those things I mentioned above. But Auto Sensitivity is not available on the X-TERRA series.
HH Randy
