Field Test Report on the Minelab X-Terra 70 Metal Detector
It was quite a surprise to receive a phone call from Minelab asking if I would consent to test the X-Terra 70, I always assumed the majority of tests were carried out "in-house"; so after gaining an assurance it would be an honest "no-holds barred" test, I agreed.
Minelab’s name has been synonymous with multi-frequency machines with the exception of the Musketeer, so why have they opted for the single frequencies and more to the point how effective will they be and will the x-terra 70 cut the mustard? The idea of using multiple coils to alter the frequency to obtain optimum performance on differing ground conditions and also sizes of objects sought is quite an innovative step.
Being the X-Terra flagship so to speak, for the purpose of the test, the 70 came equipped with the standard 7.5KHz 9inch concentric (for the 70 only)along with the extra 3KHz and an 18.75KHZ 9 inch concentric coils and also included was an 18.75KHz 10x5 wide-scan elliptical.
It is powered by 4 x 1.5V alkaline, or 1.2VNiMH rechargeables, giving between 20-25 hours use, and having a constant icon showing the battery state and a descending tone every 60 seconds denoting low batteries.
The assembly itself was quite straightforward and performed in minutes by following the comprehensive manual. This detector is by far the lightest to handle and well balanced of all the Minelab range. Construction is to a very high standard and considering the amount of functions it has to perform it is surprised me how light and compact the push-in control box proved to be. On completion of assembly in its grey livery and weighing in at 3lbs, the 70 really does look and feel the business.
The Control box and its functions
Most readers normally skip this part of the report to get to the actual testing because of the longevity, but considering that this is the place where it all happens its inclusion is most important. The manual comprehensively covers this with the use of 40 odd pages, so for my sake and yours I will keep it as brief as possible and cover just the essentials! Further in depth information will be given during the actual testing.
There are 10 touch key-pads below the ample sized liquid display read-out, with the power on/off pad which is sited to the left of this and at first glance this array could look complicated to a first time user. However a great deal of thought has gone into the ergonomics of the layout and by use of logical grouping of the controls, this simplifies the operations. (As can be seen by the photo).
Working from the left hand side below the LCD, the keypads and their functions are as follows:
Mode, this function switches between coin/treasure and prospecting modes and also activates target ID stabiliser (press and hold for 3seconds). The Auto is used for the auto-ground balance and noise cancel.
Patterns, scrolls through the coin and treasure mode’s discrimination patterns (3 and 1 All-metal) that can be used with the factory presets and/or owner’s preferences.
All- Metal, no Discrimination. Can also be used to switch between All-metal and Discrimination and also Prospecting mode and All-metal.
-/+,reduces or increases settings, used in conjunction with menu select.
Menu select, allows adjustment to the Sensitivity (1-30), Volume (1-30), Threshold (-5 - + 25), Tones (4+multiple)and Noise cancel (-2 - +2), Iron mask (0-20).
Pinpoint, (VCO, non-motion)) does what it says, it also gives a depth reading and an update on target ID when in use. Tracking is disabled when Pinpointing and the button is also used to exit the menu to begin detecting when all adjustments have been made.
Ground balance, has a scale from 0 to 90. Press for manual adjustment, alternatively, press Ground Balance and then press Auto for Auto balancing, or else hold for 3 seconds to obtain Beach mode.
Tracking, Tracks the ground and updates the Ground balance whilst giving a continuous readout. Can be de-activated by re-pressing.
Liquid Crystal Display readouts.
Once again there is an awful lot of information given on the screen, so bear with me! The screen itself is of ample size enabling clear at a glance read-outs, even for those of us using spectacles.
Along the top row are a number of icons to designate what function is being used, this includes battery condition, headphones, target ID stability, coin/treasure mode, prospecting mode, tracking, and beach.
Icons on the left hand side will indicate whether you are using all-metal, one of the three discrimination patterns or the iron mask (in prospecting mode).
The rest of the left hand side is taken up by the Target ID, with numbers ranging from -8 to 48. These numbers are also utilised when making adjustments to other functions such as Sensitivity, Iron mask etc.
To the right of the target ID is the round Menu scale, giving the list of settings, (Sensitivity, Threshold, Volume, Noise cancel and Tones) that can be adjusted for personal preferences. The ten segmented Menu scale works in conjunction with the numeric target ID in giving the value of the selected setting. it is also used for the pinpointing mode to illustrate how close the coil is to the target.
On the far left is the Depth Indicator which has been designated a set of arrows, the more arrows, the deeper the target.
Finally, along the bottom row is a series of 28 Discrimination segments (, -8 to 0 are ferrous +2 to +48 non ferrous) which will show which signals are being accepted or rejected. This is also used to display the amount of Iron Masking (0 - 20).
The manual not only illustrates the above, but also sensibly allocates the page numbers for that particular function; where it explains everything into far greater depth. The amount of functions could have meant that this would have been a difficult machine to grasp, but fortunately the manual is first class and explains everything with an easy to follow format for the new owner.
Coil and frequency selection.
As mentioned previously the X terra 70 came equipped with different frequency coils that the control box recognises. At the moment all the coils are standard 9inch concentric with the exception of the 10x5 elliptical wide-scan. So if we look at these first to find the best applications for the individual frequencies.
3KHz.
This coil has a serial number with the letter L (to denote it is low frequency). The lower frequency isn’t so affected by mineralisation as much as the higher ones. It is also able to recognise iron to a greater degree, thereby giving better iron discrimination. Its forte is the larger deeper items. However, relatively speaking, it does struggle on the smaller items.
7.5KHz
This coil hasthe letter M to denote the medium frequency and is the best all- rounder for general detecting and most soil conditions.
18.75KHz.
Once again to save any confusion this coil has been designated the letter H to denote its high frequency. (Without these letters there is no way for you to tell which frequency that you have chosen). The higher frequency is more affected by mineralisation and iron, however it is definitely sharper on the smaller targets; i.e. sceattas, gold Celtic quarter Staters and the smaller sizes of hammered coins.
18.75 KHz Elliptical wide-scan.
This is the boy for getting in amongst the nails and rubbish and pulling out those tiny items. You won’t be going for depth where this will be used, because the conditions won’t allow it; but because of its size and being a wide-scan, it isn’t so affected by mineralisation. The signals are sharper due to the concentrated electro-magnetic field pattern it produces.
As can be seen, coil selection should be thought about. I’ll change that, Ground conditions should be thought about and the appropriate coil to suit them is then selected. I generally spend an initial period of around 4hours or so testing the detector at home with differing objects, not only to gauge the performance but also familiarise myself with the controls. So far as it was possible to ascertain, Sensitivity and Discrimination worked really well, and the actual changing to a different mode or adjusting different settings was no longer down to, “what *** page was that on!”
Out on the fields.
I do not own or use a test bed, buckets of “mineralised” soil or buried objects and stand over them waving a detector, adjusting it to unrealistic detecting levels and then claiming how good it performs; these conditions are completely false. The true test of a detector is in proper detecting conditions at proper sweep speeds. It is impossible to simulate this in your back garden. The only real value of using these test beds is in familiarising yourself with your machine, nothing more.
Due to the time of year, fields were quite hard to come by and the summer heat-wave didn’t help matters either, but I did manage to get out on a few of my sites. The first of which had in the past produced a smattering of medieval finds in amongst a fair amount of iron contamination; high levels of mineralisation was a given, which is normal for this area of the County. There had been a thunderstorm two days previous so at least I wasn’t going to break my back digging!
The process of Setting up the machine.
I initially started with the 18.75KHz coil (for the small hammered coins), switched on the machine and by pressing the Menu select , Sensitivity appeared on the screen. I adjusted the level using the + and – pads to 16 and with continuous pressing of the menu select, adjusted the signalvolume and threshold and decided to try 3 tones. Hitting the pinpoint pad brought me out of menu select. For Ground balancing, Switch to Patterns and select All-metal and then Ground balance. Lifting the coil 4inches or so and lowering it a few times, listen for either a rise or fall in tones, not threshold. Adjust with the plus and minus buttons so that there is a slight transition from low to high tone as the coil rests just off the ground. I checked the reading by using Auto ground-balance (AU appears on the screen, followed by the appropriate number when balanced), I found that the machine erred on the side of caution by a couple or more digits each time, thereby making the machine more stable. Finally, press Pinpoint, select Patterns and decide which discrimination pattern suits your requirements. I found that by rejecting with the plus and minus buttons -8 to +2, I could expect the threshold to null over iron and I wouldn’t be losing any cut hammered and I could toggle the All-metal pad as a further check.
That’s it, looks complicated? In actual fact by familiarising yourself at home before you venture out, it isn’t that long before it becomes second nature and once you have the main features of it set up, you normally only have Sensitivity and ground balance to contend with each time.
Now to get Detecting.
To begin with the 70 was behaving itself, nulling out over Iron and registering the odd good target, but on good targets the meter was jumping around as if it had a thorn in its foot! The readout was signalling a variation as high as 6 digits or more on the return sweep, not a lot of good if you actually wanted to reject that target! However, this problem isn’t just attributable to the 70, as the high level of mineralisation has this effect on most of the metered detectors tried here. Normally it is a question of lowering the Sensitivity to regain a modicum of stability, but with the 70, by pressing and holding Mode Auto, whilst in “coins” this utilises a set of filters for the more mineralised ground. This also helps to stabilise the target ID numbers and gives the corresponding icon on the screen. A clever bit of work by Mr Minelab! This did solve the problem to some extent, but even so the amount of iron encountered meant changing down to the Elliptical coil.
What a difference! After re-ground balancing, the smaller size and the widescan configuration made a lot lighter work of the conditions; it was even possible to edge up the Sensitivity a couple of notches. Obviously it was necessary to work at a lot slower pace and really listen for the tones as well as the read-out on this type of ground Amongst the finds I was pleased to have pulled not only a cut half but also a cut quarter; this was more like I expected from this site.
I’ve recently acquired permission to search some forestry land, finds consist mainly shotgun cartridges until you come upon small areas which will give up anything from modern, right back to Roman and Celtic. One teensy weensy problem, the soil can be so acidic it normally eats everything. I’ve had big lumps of lead that can be rubbed with the finger and you end up with it in powder form!
Did I mention Mineralisation, No? Well it’s there in abundance, even more so after a good downpour, and in addition, there is also an aerated layer of pine needles to a depth of around three inches to get through first. Who needs a manufactured “test bed” when you’ve got this?
Any high frequency machine I have taken in the forest has struggled with the conditions. Finds are always near surface and the actual target signals are not the sharp crisp ones that are encountered on clean ploughed soil. I needed something that would punch through the mineralisation and top aerated layer, but it must also be capable of finding the smaller stuff if it is there. The 3KHz would punch through better, but would it be able to find the smaller thin sectioned items? I think not. The better choice would be the 7.5KHz and work in Prospecting mode. This mode is in reality a near enough true All-Metal with a “proper” threshold, with the added advantage of having an iron mask; however this needs to be handled with care as even moderate settings of this will discriminate gold (Quarter Staters and upwards)!
Having set up the ground balance, threshold and tones, the display only shows the amount of iron mask being used (0-20), I initially ran it about 5 which proved quite adequate. On the coil approaching a “good” target, there was a distinctive smooth rise in the threshold, which gradually decreased after the centre of the coil had passed over it. However, if it was iron, there would still be the smooth increase, but it would then suddenly cut short and null, followed by the regaining of the threshold. Surface or near surface finds would cause it to scream out, but if it was iron this would be followed by the nulling. This was a handy way of (partially) identifying cartridges in the absence of the digital read-out which is disengaged in prospecting mode giving instead the value chosen for the iron mask settings. The other method was to toggle back and forth on the all-metal pad which would then give a read-out.
Well it certainly worked, boy did I find cartridges and at some depths! This was expected, but I also managed to recover a virtually whole Roman enamelled bronze mount that was too deep and beyond the reach of my friend’s machine to register a signal. My next find was the wackiest I have ever dug, but nice just the same. It also helped me to realise the capabilities and also the limitations of the iron mask. It must be remembered that any form of discrimination will only work to a certain depth. Beyond that depth, depending on which machine is used, it will give one of two signals; either an iron signal or a good one, irrespective of the metal located. Could this be the reason for some of the outrageous claims that are bandied about? Back to the wacky one, it was a “big” signal and I ended up chopping through small tree roots down to about 2 foot (well somewhere, thereabouts); the more I dug the more I was sure it would turn out to be an humongous lump of iron, but in a forest? Finally I uncovered the top portion and lifted it out by the handle, it turned out to be an early steam engine railway lamp with the glass still intact and not only that, but there was another one in the same hole. I’ve had a few hoards in my time but never a hoard of old railway lamps! About three foot away a smaller item gave a signal, it turned out to be a button of the Eastern Counties Railways. On researching back home, this consortium was only in operation for this particular line from 1843 to 1845. Not bad for a day’s testing of a new machine!
The next field to be visited had the chance of finding Celtic and Roman, although initially used, the 18.75 KHz concentric coil had to make way for the smaller elliptical widescan. This came up trumps in providing an assortment of finds including some rough 4th century roman bronzes and fibulae. Its recovery speed in these conditions could never be considered slow, but it also wasn’t what you would call lightning fast, however by being aware of this and sweeping accordingly, the sought after items down to the very smallest can still be retrieved even in the worst of situations.
It is pointless to try and grab too much, set the Sensitivity level to suit the ground conditions; if not, all that happens is that the display read-out becomes more erratic. Although the Sens. goes up to 30, I think I managed to get it to 20 on the odd occasion and as low as 12 at other times. Set it right and you will find, set it wrong and you will start to struggle.
As regards to the discrimination settings used, I had learnt a bit more since my first foray with the 70. I normally like to hear signals from iron rather than having the threshold null and then return; as this will give a faster recovery speed. However, as the 70 has quite an expanded discrimination range at the lower end, I used the first pattern rejecting -8 to+2 (cut quarters come in at 6): I also knocked out 44, 46, 48 at the top end to cope with hot rocks and any large iron that might break through. It was then just a matter of toggling between my primary search mode of All-metal and this pattern as a double check (both modes register the target readout).
The Pinpointing mode (voltage controlled oscillator) was accurate, obviously more so on coin sized objects; anything large can be made “smaller” by gradually edging the coil closer to the target whilst repeatedly pressing the pinpoint button. (tracking is off when pinpointing).
This is a machine that can be used all day with no aching arms at the end of it, which lends itself to keeping the coil low and level with the ground at all times. Another point in its favour is the display; everything on it is perfectly visible even in brightest sunlight.
Beach work
This was kept to a minimum on account of the hordes of people descending on my local beaches during the heat-wave: let’s face it, it doesn’t do our hobby any good if little Johnny runs crying to his dad with my shovel marks across his legs for slinging wet sand at me whilst I’m detecting. Don’t ya just love them cute little brats?
Late evening with the tide just right, found me using the 70 in the Beach mode, after trying each of the different coils, I settled for the 7.5 KHz. It was noticeable on the wet sand that Sensitivity levels needed to be dropped to maintain stability, after saying this, the xterra70 proved to be the deepest single frequency detector that I have used on wet and black sand. I did manage to pull a couple of cheap rings and a fair selection of coins from these areas, by gaining then dropping Sensitivity where necessary to try and keep optimum detection depths, and obviously it worked on the dry section as will any other machine. Finds on the dry were not that deep but the 70 was very stable giving precise readouts and tones that were repeated further down the beach with other coins found of the same denomination. Buried coke cans gave good distinctive high numbers or else overloaded the 70, so remained where they were for a change! The new one and two pence’s which have a quantity of ferrous were more tricky, but with judicious use of the front and back edges of the coil it was possible to eventually “suss” these, (that is if you have that much time and really want to go down that road for such a poor return). One final point, the transition line between dry and wet sand is where most detectors are fooled. The sudden change in conditions under the coil means that the detector is always trying to play “catch-up”. Assuming the user doesn’t have a rush of blood in using too high a level of Sensitivity, the 70 performs very well in handling these conditions. Yep, you’re not going to feel out of place using this one on the beach.
Conclusions
The majority of the testing for this report was carried out in West Norfolk, “the graveyard” for any high frequency detector using a concentric coil. The soil conditions here when clean, dictate the use of wide-scan coils; if ferrous ridden, then drop down to a smaller or elliptical wide-scan; (that is if you want more in the finds pouch).
In this respect the Xterra70 started with a handicap, as seen by my swapping the standard 18.75KHZ concentric coil for the smaller 10x5 wide-scan elliptical of the same high frequency. This particular coil performed well in coping with the mineralisation and getting between the bits of iron to find the goods. I will make this a recommendation to Mr Minelab, that hopefully he will eventually produce an 18.75 KHz wide-scan 9inch coil. It would definitely be a worthwhile extra for the 70, especially so for the British conditions.
The Xterra70’s forte when compared with other single frequency machines lies in the fact that it has many applications. Where others might excel having just a sole function, a change of venue and conditions will leave it floundering, necessitating the use of another specialised machine. As seen in this report, with its repertoire of different frequencies and modes, the Xterra70 has the ability to be used for all types of surroundings and all types of detecting. In this respect it can open new avenues for the detectorists who are constantly tied to the situation of waiting for the crops to come off the fields before they can detect.
I did literally throw the kitchen sink at the 70 and in even the most difficult of conditions it came back with the goods. I particularly liked the Prospecting mode and the 7.5 KHz coil to punch through the mineralisation on less “naily” ground. Depths achieved on the medium and larger size objects left other machines in its wake. The use of the Beach mode when ground balancing “inland”,on severe mineralised ground will help the detector, but be aware that this has a “swings and roundabouts” effect. You will gain by having greater stability, but you lose on depth and recovery speed, still, at least it gives you the option of being able to detect; rather than giving up on a bad job, which could otherwise be the case.
As with all detectors, in different surroundings with less mineralisation, the 70’s performance will increase. Even here at times it was noticeable when moving from location to location, the improvements in the meter readings and the ability to use higher Sensitivity levels, thereby gaining a tad more depth. Reliable people from other parts of the country have informed me of their success in using the xterra 70 and their settings and performances put mine in the shade; strange how they still want to come here to detect though.
John Lynn