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Well, here we are, 40 years or so along from
the first metal detectors. We've been through many variations
of detector design, each adding something extra to the quest to find
non-ferrous metal items in the soil.
One of the more recent innovations has been
multi-frequency detectors - these offered a substantial increase in
depth over the previous generation of single-frequency vlf machines.
There is no doubting that such machines have aided many detectorists
in discovering some superb finds. However, multi-frequency machines
have one major downside - they null out over iron. This becomes a
problem on sites where there is a lot of iron trash in the soil -
and that is the case on most sites that are of interest to
detectorists - human civilisation through the ages has always made
extensive use of iron. This inevitably means that sites of
habitation, where interesting metallic finds can be discovered, are
littered with iron trash. On such sites, multi-frequency machines
struggle because the large amount of iron in the soil causes the
detector to basically "shut-down" a large percentage of the time.
Enter, the new breed of single-frequency
machines. These started off with the Tesoro Lobo SupaTraq, followed
by the White's MXT and the XP GoldMaxx. Detectors with much faster
response and very quick recovery times. We were now getting
somewhere, since the detectors could now 'see' non-ferrous targets
much closer to iron trash in the ground.
As a natural progression from such detectors,
along came the Teknetics T2 - made by First Texas under the well
respected Teknetics brand. This detector was designed by a team of
engineers, including John Gardiner and Dave Johnson - who also designed the Lobo
and the MXT. The T2 offers the latest microprocessor technology,
giving yet another boost to response speed and recovery times.
Only one year after the T2 came out, this same
design team had tweaked the T2 formula to arrive at another, more
powerful, detector - the Fisher F75. Fisher have always had a
reputation for deep detectors, and since First Texas had bought out
Fisher in 2006, they launched the successor to the T2 ( or,
more correctly - big brother, since the T2 is still available aswell) under the
Fisher brand - a fitting decision, since the F75 offers all the
benefits of the Teknetics T2, along with a 20% increase in power and
depth.
The Fisher F75 is currently the
ultimate in super fast response, single-frequency metal detecting.
This machine is basically a "MXT on steroids" as far as operation is
concerned. There is, however a world of difference between the MXT
and the F75 - the F75 offers a much faster response, quicker
recovery times, greater depth and better ergonomics than the MXT -
the only thing missing is the auto-tracking - a shame, but not the
end of the world.
The F75 has been designed to be
superbly balanced, so that, even though it isn't the lightest of
detectors, it feels as though it is when in use. You can happily
swing this detector all day long and not even realise it. The arm
rest is adjustable for all arm sizes - no need for a strap. The
large display is easy to see and adjustments to settings are made
with just one push button and one rotary knob. The only other
controls being the trigger switch for ground balancing and
pinpointing, plus the main on/off and volume knob located on the
side of the battery box.
In the photo above, note the
blanking grommets inserted in the adjustment holes for the arm rest. The F75
offers various positions for the arm rest, which is useful for
adjusting the machine to your exact requirements. However, the
unused holes give a possible entry for moisture to get into the
innards of the detector and are best covered up either with
grommets or insulation tape.
The F75 comes supplied with
close fitting covers for the display and battery box, which offer
excellent light rain protection. There is a stereo headphone socket
located at the top of the battery box and the detector runs on 4 x
AA batteries - with a superb 30 hours plus from each set of
batteries.
The F75 offers 3 main modes of
operation: Discrimination; Motion All Metal and Static All Metal.
The most commonly used mode will be discrimination, this offers 4
different processing modes for the target signal:
dE - the default discrimination
process - the best for new users
JE - jewellery process - makes
the detector more sensitive to small and low-conductivity targets -
more 'hyper', but the best mode for the more experienced user.
bc - bottle cap process - more
useful for American users.
PF - ploughed fields process -
a tweaked mode for uneven ground - some users may prefer this.
I, personally, prefer the JE
process - this certainly makes the F75 more noisy to use,
particularly in iron infested areas, but it is worth it for the
increased sensitivity to smaller targets. The F75 in JE mode is very
reminiscent of using a White's GMT - except for the fact that the
F75 has got decent iron discrimination, whereas the GMT has not.
The F75 also offers various
different tones for use - from 2 versions of monotone, through 2
tones, to 3 tones, 4 tones and finally delta pitch - a version of
multi-tone.
My personal preference is for 2
tones (2F), since this gives a low pitch tone for iron.
All alterations to settings are
easily accomplished with the settings button plus the rotary knob.
Unlike the T2, the F75 remembers your setting when switched off and
will start up with the same settings the next time you go out
detecting. The F75 also offers a permanently backlit display, which
can be useful for people going out detecting on evenings.
Sensitivity is adjustable from
1 to 99 - it's best to run this as high as you can put up with - I
generally run at 85 - 90 - anything over 82 will give you more depth
than the T2.
Discrimination is adjustable
from 0 to 65 - lower settings are better, but noisier - I generally
run at 0 setting.
Ground balancing is easily
achieved with the "FastGrab" setting - just push the trigger forward
and bob the coil 0 to 6 inches or so above the ground a couple of
times for the auto setting. You can then make manual adjustments to
the ground balance, if you wish, but I have not found the need to.
The F75 comes fitted with an 11
x 8 inch biaxial coil - which is basically a 2D widescan coil with a
much tighter active area down the centre of the coil - giving
greater depth penetration than standard widescan coils.
This is an excellent coil, but
can be difficult to use in stiff stubble. At the moment, this is the
only coil available for the F75, but other, accessory, coils should
be forthcoming in time.
Overall then, the Fisher F75 is
a well balanced, easy to use detector. It can be noisy, especially
over iron infested sites - but this is where it excels, since it
will find the targets that others have missed due to masking by iron
trash. A superb detector.
Pro's: *
light and well balanced detector - * very sensitive with
extremely fast recovery speed - * decent depth - * runs
on only 4 x AA batteries - * easy to set up - * good
discrimination and good choice of tone id modes - * easy to
read, informative meter - * useful ground mineral information.
Con's: * only one
coil available at the moment - although it is a decent coil, it
suffers in stubble - * springs in battery compartment are a
little weak.
Gary, 2007.
Useful links for the Fisher
F75:
Tom Dankowski's informative
forum:
www.dankowskidetectors.com/discussions/
Andy's Fisher F75 site:
www.fisherf75.com/
There is also an active forum
on Findmall, called the Fisher F75 Classroom. (see links page).
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