Minelab GPX-4000 Service Manual download pdf (Page 40)

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• Do not try to eliminate what might appear to be

a faint, isolated ground noise by balancing the

detector over the target because you may be

‘balancing out’ the target response from a deeply

buried metallic target. It is better to Ground

Balance around the target without going across it,

then switch to Fixed and try Pinpointing.

• Dig all target signals, even in previously detected

areas. The GPX-4000 has superior ground

balancing and depth so it is possible to find

new targets in well-worked areas where other

detectors have been unable to cope with the high

degree of mineralisation and/or salt.

• In some goldfields, a response may be received

from a concentration of orange/reddish dyke

material or clay. Remember, a metal target will get

louder by moving the coil even centimetres closer.

• If detecting areas of extremely variable

mineralisation, detect along the ground contours

rather than across them. This will often stabilise

the effect.

• In heavily mineralised areas the operator may

need to sweep the coil 10 – 20 mm ( ½" – 1")

above the ground. This should give a more stable

Threshold and less ground noise.

• Very sudden or large changes in the mineralisation

of an area may produce a signal from the detector.

Usually this signal is very broad, and often only

present in one direction.

Follow these hints and

techniques for better

detecting and happy

prospecting that will help

you to utilise the power of

your GPX-4000.

Detecting Tips

Identifying Target Signals

• Metallic targets will usually give a ‘solid’ sounding

signal when the coil is swept across the object

from any direction. A metallic target generally

produces a short, sharp and mostly symmetrical

signal. Ground noises usually give a broad uneven

signal when the coil is swept from different

directions and often may only give a signal from

one direction and no signal on the return sweep.

• If you are not sure if the sound is ground noise

or a target signal, you should investigate. Scrape

a shallow hole about 70 - 100mm (2½" - 4") deep

over the suspected target. Sweep the coil over

the hole at the original ground level. Do not dip

the coil into the hole. If the signal has decreased

in volume or is less defined, it is probably ground

noise. If the signal remains the same or becomes

louder, it is likely a metallic target. If you are still

not sure, make the hole deeper and repeat the

process.

• A ‘halo effect’, which may be built up around a

buried metal object, makes the object appear to

be larger to the detector than it actually is. This

will be reduced once the target is disturbed from

its position in the ground (e.g. a small object,

detected at a substantial depth, may be more

difficult to detect once disturbed from the ground

and lying in the loose dirt. If the object is reburied,

the ‘halo effect’ will not be present).

For Maximum Gold

Recovery

Keep the coil as close

to the ground as

possible.

Listen carefully.

This is more important

than looking.

Slow down, do not

rush, take your time.

Have a positive mind

set, and imagine a

nugget at every next

sweep!

Remember that

covering a small

section of ground

thoroughly will be

more productive than

randomly searching a

larger area.

Big Gold

Big Gold gives a much

different response to

the smaller shallower

pieces. The signal is

often quite broad, and

there is very little pitch

variance.

False Signals

If false signals are

occurring as you sweep

the coil, check that they

are not produced by

any metal that you are

carrying, such as your

pick, battery or steel toe

boots.

Move the coil closer,

and then further away

from your body, in

order to check if the

signals are coming from

these items. If they are,

increase the distance

between the coil and

these items.

Avoid carrying metallic

objects in your pants

pockets as these are too

close to the coil.

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Minelab GPX-4000 Service Manual Page 40

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