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Choosing the Right
Coil for the Job
Coil Size and Depth
A larger coil will typically find targets buried deeper
in the ground, but they can be less sensitive to
smaller targets. A smaller coil is typically more
sensitive to small targets, but does not go as deep as
a larger coil.
Mineralisation
A Monoloop coil will often have improved
performance over a Double-D coil but can be more
difficult to Ground Balance and therefore possibly
more noisy. A Double-D coil is often more stable in
heavily mineralised areas.
Terrain and Vegetation
A small coil can be easier to manoeuvre through
thick scrub or rough terrain. A smaller coil is also a
lighter weight than a larger coil.
Discrimination
In areas where discrimination is required, a Double-
D coil is needed for discrimination to work. In high
trash concentrations, a smaller coil is preferable.
Search Pattern
A Double-D coil will typically provide a 'blade-like'
detection pattern from the toe to the heel of the coil,
which gives excellent ground coverage. A Monoloop
coil has a detection field that is typically cone
shaped, which requires overlapping of sweeps to
ensure thorough ground coverage.
There are five main things
that you should consider
when deciding which coil
is best for your terrain and
target:
Small,
Shallow
Nugget
Large, Deep
Nugget
Highly
Mineralised
Less
Mineralised
Open
Ground
Heavy
Scrub
Iron
Disc.
10" x 5"
Elliptical
Double-D
15” x 12"
Semi-Elliptical
Double-D
18” Round
Double-D
8” Round
Monoloop
11” Round
Monoloop
15” x 12"
Semi-Elliptical
Monoloop
18” Round
Monoloop
In some circumstances,
non Minelab Double-D and
Monoloop coils will work
on the GPX-4000. However,
there are limitations which
means that some functions
will not work properly.
In some cases the use of
coils not designed for the
GPX-4000 may cause the
detector to be unstable and
noisy.
