X-Terra Tips & Tricks

Elliptical high frequency accessory coil.

Silver coins found with X-Terra.

10.5in double D medium frequencyaccessory coil.

26 TREASURE HUNTING October 2006

The following applies either

totally or in part to the X-Terramodels X-30, X-50 and thenew X-70 and is intended to

provide some useful tipsobserved during many months of "real­life" field testing. It is also intended toprovide some additional - and what isoften difficult information to come by ­relating to which coils to use, where touse a specific type, and once fitted toyour detector, which sweep speed mightbe used to best effect. As always, this isintended to be only a guide and youmight find that an X-Terra in your localsoil conditions works best with a similar

or completely different set-up.All three coil types (ie Low, Medium,

and High Frequency) are compatiblewith the X-Terra 70; two frequenciesMedium and High are compatible withthe X-Terra 50; and just the Medium(7.5kHz) frequency works with the X­Terra 30.

1. Iron IdentificationAt times in some mineralised soils or

over conductive salt certain larger thannormal iron shapes can fool the discrim­ination circuit (common in all detectors).Examples of such iron include round andholed pieces, square wheel nuts, and ifthe iron is not fully rusted through.

This might happen more if, as a moreexperienced detectorist, you are usingeither no discrimination or have just oneblock segment discriminated out (ie -8on the X-70).

Simply switch to pinpoint, as the X­Terra 70 will still update the ID inpinpoint mode. When you have estab­lished the exact centre of the target, scanover and back as tightly as you can. If thenumbers showing are minus numberswith an accompanying very low soundthe target is iron. Typically, what alsomight occur is for several of the depthindicating arrows to illuminate all atonce, plus the ID can show high fortynumbers such as 44 and 46.

If there are absolutely no minus num­bers and the tone is very high then youprobably have a silver coin (especially ifthe numbers are from 42-44).

All of the above can be achieved inabout three seconds as the buttons on

the X-Terra 70 front panel are laid out todo this very quickly and easily.

2. Iron Location & Target CentreFrom its shape and position in the

ground, iron can be a difficult target topinpoint exactly. What tends to happen isthat you obtain" one-way" signals due tothe" eddy currents" travelling along and"falling off" the end. This is especially thecase if the iron object is a straight orslightly curved item such as a horseshoefragment.

These can be troublesome signals forthe detector user as they can take unwar­ranted time to investigate. However, withX-Terra 70 all that wasted time can be

saved by using the following method.Simply switch into all metal and

move the coil a few millimetres to the left

of the "original signal". If a signal isreturned with a low dull tone and hollow

sound, with the usual negative numbers,it is iron. Non-ferrous targets such ascoins don't "move" in that fashion and

always produce positive IDs. Thismethod may take a few attempts to getright but practice for a while and itbecomes very easy to do.

3. Prospecting Modeto Identify Iron

Sometimes even using the abovetricks might still have you suspecting thatyou are onto a good find, but it is dis­guising itself by giving out high numbersand high (possibly "strangled") audioreturns. It could happen on coins that areon edge, sideways to the coil, or for itemsnew to you that you have never foundbefore and therefore are not familiar with

their responses.Simply press MODE AUTO and

allow the detector a few seconds to settle

down in Prospecting Mode at Iron Mask5 (Pre-Set). Then scan across the targetslowly and listen to the threshold return.If the signal continues and does not cutout the target is non-ferrous. If the signaldoes cut out the object is rusted and youcan move on to look for the next target.Don't forget to change back to CoinsMode.

4. Prospecting Modeto Pinpoint & Gauge Target

The Prospecting Mode on the X-Terra70 isn't just an all-metal mode! It isdesigned to detect difficult targets in dif­ficult soils with better depth and

sensitivity compared to the DiscriminateMode.

The Prospecting Mode features anadjustable Iron Mask of 0-20. Even onmaximum setting of 20 most low-con­ductive non-ferrous targets will still bedetected while rejecting small nails,pieces of wire etc. But the real beauty ofit is that it pinpoints really well (literallywith pin-head sharpness) and allows theoperator to trace exactly the real shapeand size of the target. It therefore pro­vides way more information to thesearcher in this mode than the Discrimi­

nate Mode. Used in conjunction withone another, there is a lot of valuabletime-saving information available. I'mnot saying you should work in Prospect­ing Mode all the time, but used wiselyand correctly it will save the searcher alot of time.

5. Tone (Expanded 99)Checking certain signals in "99 Tone

Expanded Range" (there are not 99 tones,but a wide range of tones) in a modernpark/beach setting that produce known"pull-tab" numbers is a good way toidentify the new square pull-tab and theold fashioned round two-part (tear-drop)ring pulls.

Coins flat on to the coil and ringsshould produce one tone with a onenumber ID. During testing it was foundthat modern square tabs and ring pullsproduced 2 to 3 tones and also producedtwo or more ID numbers. This effect iseven more enhanced with a HF coil but

does also work (but not as effectively)with all coil types.

The High Frequency coil is especiallygood at this task because it sees the smalldifferences between trash targets with agreater degree of accuracy. This extrainformation is relayed to the detector 01Flex) and in turn displayed as multipleIDs. This is because the coil" sees" thetabs or ring pulls varying shapes as eithercurves or holes, and correctly deducesthat there are a few different eddy-cur­rent flow patterns occurring in the target.There is a mild side effect in that coins at

an angle, especially shallow ones, couldgenerate two tones; but you will quicklylearn to dig those signals because theirIDs should be higher and not those asso­ciated with trash, which are usuallylower.

X-Terra 70

front panel.

The trick described above is a tech­

nique that takes a lot of experience to usewillingly, and may not be for the "fainthearted".

6. PatternsA good technique that I use person­

ally is to work in Pattern 1 with justblock minus 8 rejected (X-Terra 70).Manually ground balance to a slightly"positive" effect; adjust sensitivity until itbegins to chirp or chatter and then backoff by two numbers. So, if 26 was justbeginning to get a bit noisy, reducedown to 24 where the chatter should

stop.Another method I use is to "scrub"

the ground surface (coil covers are easilyreplaced). It is actually very easy (andquiet - no ground noise) to work in thismanner. It is also highly effective as youare literally on the ground and any depthloss by reducing sensitivity is compen­sated for by the fact that you are nowcloser to the targets in the ground.

It can be slightly noisy (junk noises)as more iron will tend to break through,but so will the low conductive marginaltargets. You could then store into Pattern2 rejected blocks minus 8, and minus 6,and into Pattern 3 store all the ferrous

blocks rejected: -8, -6, -4 and -2. Afterthis, check any doubtful signal whilescrolling through all three patterns. Asignal might not reject if it is ferrous inPattern 1, but might in Pattern 2.

Again, it is all down to speed andhow quickly you can correctly analysetarget signals. The more junk you can IDin the fastest possible manner, the more

Des Dunne

you will make productive use of yourtime looking for the good targets. Takeanother look at Point 4 above and use

that to analyse your targets.

Advantages of Concentric& Double-D Coils

With a choice of coil frequency andconfiguration, it is important to under­stand the differences between aconcentric compared to a DD coil. Aconcentric coil has a tight field of detec­tion that is great for isolating goodtargets in high trash areas; it also allowsfor excellent pinpointing abilities. A con­centric coil can be a lot thinner

physically as the internal windings don'toverlap; hence the reduced weight.

A concentric coil puts out a conicalsearch pattern, which tapers down atdepth. For accurate ground coverage,you therefore have to overlap yoursweeps by a third of the diameter of thecoil in order to avoid missing any targets.

The advantages of DD coils are thatthey send out a blade like signal almostfrom tip to toe even at full depth. Youtherefore only have to overlap yoursweeps by about an inch, enabling youto cover the ground a lot quicker.

DD coils also have better rejection ofground noise, and are less sensitive toground changes, so the need to usetracking ground balance is reduced. So,for open areas with higher mineraliza­tion and generally less targets (like largebeaches and pasture), a DD coil may bepreferred. For smaller areas that are fullof junk like parks and old gardens, stickto a concentric coil.

October 2006 TREASURE HUNTING 27

X-Terra Tips & Tricks

Chart of typical UK coin values on X-Terra 50X-Terra SOlD's

COINYEARID NUMBERTONERESPONSE

Pound199430 MedPositive

20p

200118 LowPositive

lOp

199215 LowPositive

5p

199009 LowPositive

2p

199621 MediumPositive

1p

198536 MediumPositive

sovereign

191618 LowPositive

Gold sovereign

191427 MediumPositiveSilver florin

191445 HighPositive

Silver shilling

187939 MediumPositive

Roman copper

-33 MediumPositive

Roman copper

-27 MediumPositiveRoman bronze

-06 LowPositiveHam silver coin

142516 MediumPositiveHam silver coin

167218 MediumPositiveHam silver coin

155221 MediumPositiveHam cut

?09 LowPositive

Ham cut-?

06 LowPositive""""

""'"-"'E--;'.m ... v:~."

Coil Type & Sweep SpeedTo take things to an extreme, you

could crawl along on your hands andknees, push the coil in front of you andstill make good finds. Similarly, youcould charge along swinging the coil as ifcutting grass and make more finds. Asyou know there are many detector mod­els available, mostly using different coilsizes, various coil shapes, different oper­ating frequencies etc.

Each may have to be used differentlyto work to best effect (learning curve)but, of course, will still make decent findsif no real thought or effort is put intousing them.

With the X-Terra some of those coilchoices now come in the form of the coilsdescribed in this article and - for the firsttime from one detector manufacturer ­

the opportunity to change the detector'sdetecting parameters by using a differentcoil with changeable frequencies is onoffer - V Flex.

So, while you could detect merrily allday long and not do anything different,you would still make finds. But, if you are"really dedicated" and/or perhaps a"purist", you might then deliberatelymatch the detector and search coil to

your appropriate site. Using the circularMed-Freq, Hi-Freq, DD Med-Freq, andLow-Freq coils (or elliptical Hi-Freqcoils), each may have to be employed atdifferent speeds/lengths of sweep togenerate good signal return from targets.For example, the stock 9in circular7.5kHz Medium Frequency coil seems towork best with a "moderate" sweepspeed. It reacts across the range of highlyconductive to low conductive targetswithout any "undue gaps or anomalies".

The 9in circular Hi-Freq coil seems to

Broken Roman silver coin.

28 TREASURE HUNTING October 2006

prefer a faster sweep speed. The Hi -Freqelliptical appears to work equally as wellwith either a slow, medium, and/or fastsweep. The Low Freq coil, on the otherhand, appears to prefer a slow sweep forlow conductive targets and a fast sweepfor high conductive targets.

Depending on which coil is beingused at any given time, some care andconsideration should be put into the waythat a site is searched. For example, if youwere using the Med -Freq coil in a chosenarea, you could sweep north to south at amoderate sweep and extract any goodresponses. You could then work east towest at a quicker sweep with a High­Freq coil to determine if anything hadbeen missed.

Many searchers "crisscross" patchesin this fashion to ensure that everythingpossible can be found during an initialsearch; after all, it could be many monthsbefore a return visit is possible.

Wet salt water sand searching (singlefrequency units) usually dictates a slowsweep speed with reduced sensitivity tominimise false signals. A good plan istake a notepad and pencil and writedown your findings as they occur. Learnas you go and try to remember as muchabout a particular search and/or coil asyou progress through the day. You maynotice" trends" developing and you willlearn from that. For example, the highfrequency is reported as being "toosensitive" to tiny aluminium shards in

modern city park settings that use grassmowers etc. But a dedicated searcher

would definitely use a coil/detector ofthat type to search a Roman site for lowconductive bronze coins. The Hi-Freqcoil works very well in a salt water envi­ronment and it has been reported that itsuse there has resulted in the finding ofmany gold chains which are "difficult tar­gets" for some set ups.

The following is a brief descriptionabout the various new X-Terra coil types.

lO.5in DD 7.5kHz Med-Freq X-TerraAccessory Coil

The new 10.5in DD medium fre­

quency accessory coil for the X-Terraseries, although a tad heavier than the9in coils, has a more professional feel toit and also provides increased depth andperformance in the field and wet saltsand areas on the beach. The extra width

provides a sure-footed even sweep,essential for exact and accurate groundcoverage. It also provides a markedincrease on "in-ground" depths on tar­gets - especially deep targets that couldbe missed with a smaller coil.

Over salt wet sand the coil is smooth

and it is perfect for beach work as itglides like a hovercraft across the wetsurface thanks to its rounded edges.Above all else, it provides 100% stabilityin this difficult environment. Increased

depths are achieved while sensitivity isretained, even to the smaller difficult

targets typically reserved for a multi-fre­quency machine.

Discrimination and pinpointing areas accurate as with the standard coil. To

fully utilise X-Terra's V Flex asset, thislarger coil turns all the X-Terra models,including X-Terra 30, into a more accu­rate, sensitive and truly deep-seekingdetector.

lOin x 5in DD 18.75kHz Hi-Freq Ellip­tical X-Terra Accessory Coil

The performance on the beach withthe HF coil was very surprising, as a fre­quency of 18.75kHz is actually quieterand punches deeper than those ofaround 5kHz, in certain types of miner­alised soil. I was lucky enough to find afew new storm cuts and dug out a few"keepers". Admittedly, they were notmuch, mostly old coins from the pre­decimal era and modern copper coins,which were bursting out with iron corro­sion.

On stubble this coil is very confidentand the masking of smaller targets fromnearby iron is minimal. A much rustedplough share gave a reject sound but anaccept signal was heard and 2in awaywas a small copper coin. Sensitivity tosmall low-conductive hammered - not

necessarily deep but at awkward angles ­and on-edge coins is just as good as flaton and during testing some coins werefound either completely on-edge or atdifficult angles; but they gave unmistak­able sharp, dig me type signals.

Listen out for Low Tones and Low ID

numbers (eg 8, 10, 12, 14, and 16).

9in 3kHz Low-Freq X-Terra AccessoryCoil

The 9in concentric 3kHz coil for the

X-Terra 70 is a coil designed specificallyfor those who would like to increase

overall depth and target responses onhigh conductive targets. The 3kHz fre­quency will give you a depth advantageon certain specific targets such as copperand silver items of any SIze, large golditems including gold coins, and certainhigh conductive relics such as oldweaponry; it could be an ideal hoardfinder if evidence of a scattered hoard

was present. In addition, the 9in concen­tric design gives you exceptional targetseparation, and excellent pinpointingabilities. As with all the other X-Terra

accessory coils, it is waterproof andcomes with a free coil cover.

Coil IdentificationThe Medium frequency coils are

identified by an "M" before the serialnumber, the letter "H" denotes the Highfrequency, and an'T' identifies the Lowfrequency coils. On the off chance that"the dog eats your homework" and theserial numbers from your coils, there is avery clever way the Minelab boffinsdevised in X-Terra's software to allow youto visually see on the screen the particu­lar frequency of a possibly unknown coil.

With the detector turned on, pressMenu/Select once and then press andhold the Patterns button for about 5 sec­onds - the frequency of that coil shouldbe visible and this enables you to knowexactly which type of coil you have.

Des Dunne

The author using an X-Terra 70 with 10.5inDD coil.

Note: some information contained

here might not be applicable to the X­Terra 30 model as it operates on just onefrequency (7.5kHz Medium Frequency).

As stated, this information is derivedfrom thousands of hours of X-Terra tests.

It mayor may not apply to your particu­lar location.

If you would like to share somethoughts or would like to see more infor­mation on X-Terra, I may be contacted at:

minelab@minelab.ie

Telephone: 00 + 353 + 23 + 52101Or write to: Des Dunne, Minelab

International, Laragh, Bandon, Co. Cork,Eire. I TH I