A long time ago, I made the observation that when I am metal detecting for very deep objects, every metal target ‘goes to iron’. Now I know that that was a poor choice of words.
What I meant to say is that when you are detecting for very deep objects, and for me, that’s past ten inches deep, all targets sound the same as iron would at that depth. With the XP Deus Metal Detector, that means an ID in the high 90’s and a high tone. Of course, with advanced detectors, you can change the tone to whatever you want but be that as it may, the ID probably won’t change.
Why you may ask? The answer is that the identifying circuit in your detector, at least for a Very Low Frequency (VLF) detector, does not go all the way to the limits of the signal. Confused? Let’s see if I can make a picture:
So, as you can see, your detector can achieve an absolute depth dictated first by the power output of your machine and the size of your coil, and then, by various external variables such as ground mineralization, ground moisture, ElectroMagnetic Interference (EMI), ambient temperature, etc. When you get to this limit, you may get an ID or you may not but whatever audio signal you get however, will be the same for ALL targets. There may be people out there with super ears who, while using a detector with variable audio may discern differences in the tone at that depth. I hear people claim this but I haven’t met anyone personally who can do it.
That’s what I meant when I said ‘all targets go to iron’ at the limits of your detector’s signal. Why this happens is beyond my puny little brain. In fact, I could be wrong about my understanding of things. This notion was borne of experience. I have dug thousands of holes in the last 6 years and explored the depths more than most. It really hurts me to see newbies get excited because they get a high tone on a deep target. Sometimes they get lucky, as do I, and pull a keeper from the depths but let me assure you that if you routinely dig signals at eleven or twelve inches (or deeper) as I do, you will have an impressive amount of old, rusted iron for your efforts.
I also do not understand why a freshly buried target can be id better than a target which reaches the same depth via natural processes. A detectorist claimed once that his Tesoro Vaquero could id a nickel at twelve inches. To test, I buried a nickel at 12 inches and was able to id it half the time with my machine. In real life, however, I’ve yet to id a nickel past seven inches, and I mean, with a proper id and a tone.
So there you have it. Maybe this is useful or maybe it is pure dribble. You decide. Also, if you are smarter than me and have a good solid understanding of the workings of a detector, please comment below. I could stand a bit of learning.