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Hunting by ear... Audio tones on the X-TERRA

December 06, 2010 10:08am

Randy Horton
Randy Digger Horton

With "old" being a relative term, I hunt for old coins at old sites. The part of the world that I live in wasn't settled until the mid 1850's. So finding coins older than 1900 is considered to be a good hunt. Many of my favorite spots to detect are old homesteads and farm sites. With the houses and out buildings long gone, to the passerby, most of these places look like any other corn field in this part of the Country. Pieces of brick, stone, glass and pottery are some of the things that I look for when wandering across these corn fields. And when I start hearing the low tones produced by nails and other "farm trash", I know I'm getting close to where I want to be. Unfortunately, even though these pieces of deeply buried iron are a good indicator of where the buildings once stood, their occasional "wrap around" high tones can cause a lot frustration. I'd venture to say that there isn't one among us who hasn't dug a piece of deeply buried iron or an old rusty nail, expecting it to be a coin. Now, I'm not going to tell you that the method I use to help eliminate these targets will keep you from digging all of them. But I will tell you that the X-TERRA has the ability to identify most of these "trashy" targets, even when providing an initial "keeper" tone. It’s just a matter of properly setting up your X-TERRA, knowing how to work the coil and listening to what the detector is telling you. And it is for those "wrap around" targets that I have written this short article.

Harvested corn field - Perfect for metal detecting for old coins and relics

This process is fairly simple… but to implement it, your X-TERRA must be capable of operating in the Multiple Tone mode (X-TERRA 305, X-TERRA 505, X-TERRA 70, or X-TERRA 705). And you must be using zero discrimination (or All Metal mode). Although I've found that the 9-inch Concentric coil at 3kHz provides the most easily distinguishable low tones on deeply buried iron, all of the coils will do it to a certain degree.

 rusty nails found with a metal detector

When you first get the "hit" on what sounds like a good target, slowly “X” over the target from several directions. Much of the deep iron will produce broken or choppy signals when working your coil around the target. If the audio response locks on a high tone, make a mental note as to where the strongest target signal is coming from so you can center the target under the coil. Once you get the target centered under the coil, continue wiggling the coil back and forth over the target while slowly working the coil closer toward you. As the target leaves the front edge of the field of detection, listen even more intently to the tones. If the audio tone is high and drops off suddenly, get out your digging tool and retrieve your coin. Here is a short audio clip of the sound produced by coins.

If the audio tone starts out high, then transforms into a blended harmonic of low tones when the target leaves the detection field, I'd bet the ranch that it is going to be a piece of iron.

By design, the Double-D coil will not lose the target signal until the target "slips past" the front tip of the coil. Whereas the concentric coils may lose the audio signal prior to passing under the front edge of the coil, depending on the depth of the target. Regardless of which coil is your coil of choice, make sure you center the target under the coil before working the coil toward you. And remember, for this method to work effectively, you must have all notches set to accept. Rejected notches create target blanking and audio tones will not be provided for those notch segments. And since all ferrous targets produce the same sound in anything less than multiple tone mode, you wouldn't hear harmonic (blended) low tones if you are using one, two, three or four tone modes either. You must use multiple tone audio mode with zero discrimination for this procedure to work properly.

old coin found with an X-TERRA 705 metal detector in a corn field

Next time you're out hunting a site where deeply buried iron is giving you the "wrap around effect", give this procedure a try. If you hunt the kind of places I hunt, you‘ll find using this procedure will result in your digging a lot less iron. 

Randy Horton


Excellent article Randy, coming from the gold prospecting part of detecting I often find my treasure hunting skills to be a little off due to target size and the frequency of targets (target sizes tend to be much larger and metal signals more prolific when coin hunting compared to the tiny nuggets I look for in mainly low trash areas with my GPX 5000).

On occasion I get to go for a holiday on the coast with the family so take an X-TERRA 70 along for some coin hunting fun as the kids do their thing in the play ground or swim in the sea, more often than not the kids join me and then help spend the money I find on ice creams :-), getting my head around all the discrimination terms and settings is too much for only a short timeframe.

Your suggestions will be invaluable when on occasion I hit a deep target that is tricking my notch method into thinking it is a one dollar or two dollar coin. I assume this method could also be used with the E-TRAC?
Posted By: Jonathan Porter on December 07, 2010 08:00am
Thanks for the comments Jonathan. To a certain degree, you can implememnt this method to differentiate deeply buried iron from coins using most any "coin" detector with multiple tone capabilities. The secret is to sweep very slowly, open up the audio to multiple tone and don't use any discrimination. The slow sweep allows you to separate and hear all target signals. If you don't use multiple tone, adjacent target sounds can be the same pitch as the "keeper" target. And if you use any discrimination, the iron may be "blanked out", resulting in you only hearing the high tone representing a "keeper" target. With my E-TRAC, having both ferrous and non-ferrous TID reduces the number of times I might have to use this procedure compared to a detector capable of only providing non-ferrous (conductive) tones or visual ID. But the practice of sweeping slow and X-ing over the target while moving the coil toward my feet has helped me avoid digging tons of rusty nails in many of the old homesteads I hunt. Particularly those bent nails that typically read 01 - 35 and produce a higher tone on the E-TRAC. Even in two-tone ferrous, small bits of iron can and will produce a high pitch "wrap around" tone if you don't slow down the sweep and allow the targets to separate. Once a coin hunter understands this procedure, they'll be be surprised how "hunting by ear" can greatly increase the amount of turf they can cover in any given period of time, simply because they'll spend less time digging deeply buried iron and more time looking for the good stuff! HH Randy
Posted By: Digger on December 07, 2010 11:30am
Jonathan, One other thing I thought of that may help you and your family while coin hunting is to make a mental note of where the target is located while running with some Discrimination, compared to where the target audio comes from when using All Metal or zero discrimination. While X-ing the coil back and forth over the target, make a mental note of a pebble, blade of grass, leaf or something else that is directly above where you think the target is buried. Do that in your Discriminate mode as well as in All Metal. What I've found is that many "trash targets" will not "beep" in the same exact spot while X-ing over it in both modes, in all directions. The audio tone of iron (particularly wrap around iron tones), has a tendency to "move" to the outer edge of the coil instead of remaining directly below the center of the coil. If, while X-ing" over the target, the location of the strongest audio tone remains in the "consistent location" using both All Metal and Discriminate, get out the digger! Just be aware that coins on edge or coins with adjacent targets nearby can (and will) respond with inconsistent audio and visual TID. HH Randy
Posted By: Digger on December 07, 2010 11:46am
Thanks for the complete explanation of your "harmonic tone differences" technique that you talked about many times in your posts. Too bad the hunting season is over for me because I am excited to test it out. Spring will have to do in my case. One question, will this technique work with trash items besides iron, i.e. can slaw, pull tabs, etc?
Thanks again and Happy Holidays
Posted By: chuckciao on December 08, 2010 01:25am
Interesting you should mention this Randy, I have noticed when trying to pinpoint or retrieve a target with the DVT MPS Gold machines that if a target is proving difficult to locate/pinpoint then 9 times out of 10 it will be ferrous.

I would say it is to do with magnetics, a non-ferrous object will create an eddy current when stimulated by the detectors transmit field but not react magnetically to the field like a ferrous item will (like a magnet will be physically attracted to a piece of ferrous metal and vise versa), therefore a non ferrous item will generate a cleaner more mellow audio response, whereas a ferrous item will create a more confused raucous response when in the all metal mode.

Looks to me like the multi tones can be very beneficial in identifying or should I say "making an informed decision" on what the target is.

Thanks for the interesting read, definitely food for thought.
Posted By: Jonathan Porter on December 08, 2010 03:06pm
Chuck, Good question. The principle behind listening for the harmonics while using multiple tone, zero discrimination will work with any targets. The key to separating and identifying each of those targets is (in the case of the X-TERRA) each target having a different notch value. If you have two targets with the same notch value, they will both provide the same audio tone and will only notify the user that there are two individual targets with comparible conductive values. However, if any two targets have different notch values, they will provide two distinct audio tones. The closer the notch values, the more similar the two tones, and the more difficult to differentiate. The reason I recommend trying this for deeply buried iron is because those small iron targets can (and will) provide a "wrap around" response that can only be distinguished by using different audio tones for each target notch and slowing down the sweep speed, allowing the X-TERRA to process each target individually. While simultaneously dragging the coil toward your feet, you add the separation capability of "top to bottom" as well as the "side to side" separation provided by X-ing over the target. When this is accomplished, the iron target will provide property information that is more aligned with it's ferrous value, resulting in those deep harmonic tones. I hope this answers your question. HH Randy
Posted By: Digger on December 09, 2010 11:29am
Jonathan, Your comment ""making an informed decision" hits the nail right on the head, so to speak. The more information we have access to and are capable of understanding, the better decisions we can make in regard to "dig or not to dig". Understanding the functionality of a detector is of the utmost importance. But as a hobby detectorist, I view the act of detecting more as an art than a science. So again, your comment "making an informed decision" is an excellent definition of how I apply this process. HH Randy
Posted By: Digger on December 09, 2010 11:39am
What if there is a nail and a coin together? How can you tell the difference between the wrap around tone, and two separate items?

Are we taking a chance that the junk has a coin next to it?
Posted By: RyanChappell on February 01, 2011 03:20am
The manner in which a detector will respond to adjacent targets depends on how far the targets are separated, the elevation of each target and the size of each target.

Sensitivity setting can also impact your results. Running with a higher than necessary Sensitivity setting can (and will) cause a large "bad" target to mask any signal created by a smaller, adjacent, good target. By lowering the Sensitivity, using the small DD coil and working it very slowly, programming the X-TERRA with multiple tones and minimal discrimination, you will be better able to hear separate signals for each target.

For separating horizontally adjacent targets, (side by side) the 6-inch DD coil is the best candidate for the X-TERRA due to it's small size and DD (knife like) detection field. When you hear a tone, slow down the sweep and work the area from various directions. Eventually you will find the direction that maximizes the separation.

Unfortunately, when a larger "bad" target is directly over a smaller "good" target, you'll not likely get a signal from the smaller target due to the strength of the signal generated by the larger target, closer to the coil. If the "good" target lays outside the parameter of the "bad" target, you may be able to hear the tones generated by the "good target when swept from the proper direction. The problem is, we never know what direction that might be. And again, it depends on the size of the targets and where they are located in relation to each other. To hone your skills, you can duplicate this experience via airtests using a coin and various "bad" items (of different sizes) that you have around the house. You may find a large nail directly over a coin will not allow the coin to produce a signal you can decipher. But if you allow the coin to protrude outside the perimeter of the nail, you might find the right combination of sweep speed and coil direction required to detect it. A smaller nail and a larger coin will not produce as great of challenge.

To help reduce the effects of "wrap around" tones, I might suggest you run in a Pattern mode with only +48 rejected. I believe the most ferrous notch and the most conductive notches are "narrower" than the others. So even though you are rejecting the largest, most conductive targets by setting +48 to reject, a silver dollar sized coin (and smaller) will still provide a conductive reading that is accepted. I might also suggest running with a slightly negative ground phase setting. This will fool your X-TERRA into thinking the ground is less mineralized than it really is, and allow the targets to be more easily identified. To accomplish this, properly set your ground balance and before locking it in, press the + pad two or three clicks. (I know that sounds backward. But by increasing the ground phase number, you've actually programmed the detector to have a negative ground balance.)

Designing and building a detecor is a science. Operating the detector is an art. Until a manufacturer comes out with one that has X-Ray vision, we must maximize the information that the software provides to us on the display and through the audio sounds. Anywhere we hunt, we are taking a chance that a piece of junk has a coin next to it. In many of the places I hunt, that in itself is the primary challenge. Having detected for nearly 38 years, I am convinced there are more old coins still out there due to target masking, opposed to unattainable depth. So in my opinion, it is worth the time and effort to slow down the hunt, chose the best coil for the job and implement the skills I've developed in proper "coil management". By doing this, I will greatly increase the odds of separating adjacent targets and hearing the sound generated by the "good stuff".

Hope this helps answer your question. HH Randy
Posted By: Digger on February 16, 2011 02:12pm
What an great lesson here! You have just shaved off 6 months of learning curve for me! and countless others! THIS NEEDS TO BE IN THE MANUAL!!!!! I tried this on about a dozen different targets and dug them all and EVERY SINGLE TIME IT WORKED!!!! I will never hunt the same again! Thank you so much Randy!
Posted By: antandshell on April 09, 2011 01:52pm
Thanks for the feedback. I appreciate your comments and am glad that this "lesson" is working well for you. HH Randy
Posted By: Digger on April 12, 2011 06:12am
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