the searcher
FIELD TEST
After a short time playing with the various controls
I realised this is a more advanced detector than I had
initially assumed and although the basics were straight
forward enough, my first part of the test needed to be
make a cup of tea and read through the instruction
manual. The manual explains every control clearly with
both descriptions and diagrams and also goes some way
to suggesting the conditions under which the various
modes or setting are to be used.
Controls
All functions are accessed through the keypad and are
conveniently positioned within easy reach of your thumb
for convenience whilst in use.
The diagram (next page) is reproduced from the
instruction manual to give Control layout and descriptions.
Minelab X-Terra 70
Spec sheet
Operating modes
Coin & Treasure: Tone ID, Meter ID Motion with
Threshold.
Prospecting: VCO motion with Iron Mask & Threshold.
Frequency
3, 7.5 & 18.75 KHz
(coil dictates frequency)
Standard Search coil
9" Concentric coil (7.5KHz)
Weight
1.3kg (2.9lbs)
Battery type/life
4 X ‘AA’ /approx 20hrs
Accessory search heads
9" Concentric 3KHz
9" Concentric 18.75KHz
10 x 5" Elliptical ‘DD’ 18.75KHz
10" DD 7.5KHz
When I tested the X-Terra 50 a couple of months ago I
was impressed with its performance so when Minelab sent
me the new flagship of the X-Terra range, the X-Terra 70
I was more than happy to put it through its paces. This
was mainly because I wanted to see whether it performed
any better than the 50 or whether it is the same machine
with the odd extra whistle and bell added. I also requested
that the new 18.75 KHz ‘DD’ or widescan, elliptical coil
be sent as well as the standard coil as I felt many serious
users would be interested in the higher frequency
alternative.
Not long after arrival the ‘70’ was assembled and ready
to go. The stem and control box are exactly the same as
the X-Terra 30 & 50 so it is the same lightweight (1.3kg
2.9lbs) chassis and the same build quality. The same 4xAA
battery set up is also used. The stem colour is described
in the manual as ‘Dulux Notre Dame’- which is grey to
you and me! (Minelab have even given the colour reference
number -36672 so if you scratch the stem all you have to
do is nip down to B&Q and buy a tin. 10/10 for attention
to detail Minelab!) Seriously though the grey, sorry Notre
Dame is an attractive and appealing colour finish.
Uses
The X-Terra 70 has two main detecting modes; Coin &
Treasure (C&T) mode and a Prospecting mode. It also
accepts coils of three different frequencies – 3 KHz,
7.5 KHz (supplied as standard) and 18.75KHz making
for a very versatile detector indeed.
The C&T mode is designed for general purpose use
(and beach use when the beach Ground Balance is
activated) and has meter and adjustable multi tone audio
ID. The operator can select 1, 2, 3, 4 or 99 tones for true
audio ID. Discrimination in this mode is in the form of
28 individual blocks along the bottom of the screen.
Any one of the blocks can be accepted or rejected to
suit your requirements. As with this, and any other
detector, utilising this notch Discrimination system
caution is advised so as not to reject wanted targets.
The Prospecting mode is a more specialised mode
and although designed with gold prospecting in mind
is useful for achieving greater depths and/or Sensitivity
to smaller objects. It is also an advantage in areas of
higher mineralization (pasture being a good example).
In this mode there is no form ID, simply an audio signal
to indicate an accepted target. Discrimination is of the
more traditional accept/reject scale. The level of which
is displayed together with a numeric counter.
The Prospecting mode takes a bit longer to master,
but it’s worth it, more on that later.
Air testing
For an initial air test the detector was used in factory
presets except for the Sensitivity which was pushed up
as high as possible whilst still remaining stable. This was
done for both modes as Sensitivity is adjusted separately
for each.
There is no point boring you with pointless air test
results other than the depth difference in each mode.
Coin & Treasure
Prospecting
Pre decimal
penny
24cm
40cm
Cut half
(hammered silver)
13cm
19cm
The Prospecting mode was considerably deeper although
recovery speed is a little slower in this mode suggesting
it would struggle on junky sites.
The Searcher July 2006
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Illustration from the Instruction Manual with permission from Minelab
In the field
The first field was; you guessed it, the
pasture field. This time though it was
deliberate as I know what to expect in
terms of finds and it would be a perfect
place to compare the two detecting modes.
I began in the middle of the field with
the Sensitivity at 25, and Discrimination set
to reject from -8 to -2. There are three ways
to Ground Balance; Auto, Manual or Track.
Track is by far the easiest method, simply
press Track and the detector will constantly
track the ground. Manual Ground Balance
will generally offer a slight depth
improvement. To use this method press
Ground Balance then raise and lower the
coil from about 10cm to the ground and
using the + and - buttons. Adjust until there
is little or no change in the high and low
tones. Auto is the same but is self adjusting
as you raise and lower the coil.
Having three ways of Ground Balancing
may seem a little complex or even
unnecessary but in practice it is very simple
and ensures any level of user can achieve
satisfactory Ground Balancing.
With both modes set up I began detecting
in the C&T mode. The Threshold remained
stable apart from the odd, very fast null,
a sweep or two in All Metal confirmed this
was iron. Before long a crisp high tone was
heard. This turned out to be two pre
decimal pennies laid together from a
depth of about 14cm. A little further on
a lower tone and a reading of 18 produced
a fragment of the aluminium alloy that
litters this site.
I continued across the paddock for the
next half an hour or so, digging various non
ferrous bits and pieces of various sizes. Two
52 |
The Searcher July 2006
things became apparent as I did this; Depth
and Sensitivity are very good, impressive
even. The second is that ‘iron reject’ is good
but the odd bit did get through which I put
down to the power that has been built into
the detector. Although this was not a big
problem as any iron signal was jumpy on
the meter and the audio was crackly or
‘woolly’ where as a non ferrous sound,
however faint, is solid and the meter
locks on… give or take a number or two.
The next step was to try the X-terra 70
in Prospecting Mode. And boy is this mode
a different animal! In this mode you are
working with a VCO (Voltage Controlled
Oscillator) whereby there is an increase
in volume and pitch when a target is
encountered. There is no form of ID, simply
an audio signal for accepted targets and
even then a slow sweep speed is required
to allow the Discrimination (or Iron mask
as it is referred to in Prospecting) to jump
in (it takes a fraction of a second and does
literally jump in). I found with larger bits
of iron this was no problem but with smaller
bits it could be fooled and these were
identified by switching back to C&T.
Using the two modes back to back did
prove successful. On a couple of occasions
there was no signal on switching back to
C&T and each time a deep non ferrous
target was uncovered. One particular
signal was interesting; a clear signal was
encountered and the iron mask would not
jump in no matter how I approached it.
Assuming it to be a good signal I double
checked C&T. There was the faintest of
signals, so faint it would have missed it
had I not already known of its presence. On
digging, a copper alloy scoop was unearthed
from a depth of about 15cm. This was
positioned vertically in the soil and so did
not provide a good surface area for the coil
to ‘see’. When you consider that the C&T
mode is very good in its own right, the
level of audio given by this object in the
Prospecting mode was impressive to say
the least.
I continued for the rest of the session in
Prospecting but finding it useful to be able
to refer back to C&T for reference, which
at the push of one button is no problem.
All target information in Prospecting has to
be gleaned from the audio and this is where
the learning curve lies. The more I used this
mode the more I liked it and couldn’t help
feeling that with experience I could use
this on all but the ‘junkiest’ of sites.
On arable land
Luckily an invitation to detect on some new
land cropped up during my time with the
70 so it was a chance to get on some arable
and pitch it against another detector.
It was rainy as I set out on my journey to
meet my friend Dave, and about an hour
later we were stood in the rain at the edge
of a sodden sugar beet field deciding what
to do next. The field was not our planned
venue as the farmer had decided that the
one we wanted was too wet to risk his
seedlings and offered us this as an
alternative. The field did not look very
productive but we had a go anyway.
I had fitted the 18.75KHz DD coil and
was soon scanning the field stepping
carefully between the young beet shoots.
The field did not seem to be particularly
mineralised so I pushed up the sensitivity
to 28 and used the C&T mode. Before long
the first positive signal gave a reading of
12 on the meter. This turned out to be the
percussion cap from a 12 bore cartridge.
A few steps further and a small button was
dug from about 9cm. From then on finds
were few and far between for us both.
The finds from the suger beet field. The copper alloy
object that eluded Dave's detector is bottom right.
With the rain coming down harder we
both stayed at the lower end of the field
close to our cars in case the rain should turn
torrential. I worked my way steadily across
the field for about half an hour and
unearthed a steady stream of non ferrous
items, the smallest of which was a little
copper alloy ‘blob.’ At one point Dave was
close enough to me to check a signal. This
was rather faint and the meter was not really
sure giving numbers from 15 to 19. To my
amazement Dave’s detector rejected the
target. I dug and extracted a small piece
of molten copper alloy from 10cm. I am
not about to name Dave’s Detector model
as this was only one example and could
have been a fluke but I can say its retail
price is within a few pounds of the 70.
Shortly after we were both soaked
through and called it a day. Neither of us
had anything spectacular. My finds total
though was 14 items and Dave had 8 so
the 70 had proved itself (although find
of the day was a 1904 halfpenny which
fell to Dave!)
Summary
With detectors such as this that edge
towards the top of the range, it is difficult
to do them justice in a short field test. There
are many features that cannot be covered
because editorial space will not allow. Also
because one needs more than a few hours
of use to realise its full potential. I can say
the X-Terra 70 is an excellent all round
metal detector. It has the Sensitivity and
Depth to satisfy the seasoned enthusiast
searching for the elusive ‘Sceat’ or tiny
hammered silver coins, particularly if
the 18.75KHz elliptical coil is used, yet
is suitably ‘turn on and go’ enough for
a beginner to use and get to grips with.
The Prospecting mode is not for the faint
hearted and will take time to learn. If you
are the impatient type, stick to the C&T
mode. Those of you prepared to work with
this alternative mode and master it, will
need to buy a bigger finds pouch! It will
only be the junky sites where difficulties
will be encountered when using Prospecting.
I am enthusiastic about this detector
and have negotiated that it stays with me
for a while longer with a view to submitting
a more Advanced test in the future.
TEST RESULTS
User Features – (Scores out of ten)
Ergonomics
(weight/balance)
8
Simplicity/user friendly
7
Build quality
9
Accessory search coil
compatibility
9
Arable land use
9
Pasture land use
8
Park land use
8
Dry beach use
8
Wet salt beach use
7
SEARCHER RATING
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