Minelab GP 3000 Metal Detector User Manual

⚠️ AN IMPORTANT MESSAGE FROM MINELAB

Minelab asks detector operators to take all due care regarding the environment. Minelab stresses the importance of being responsible when recovering targets.

BACKFILL EVERY HOLE YOU DIG.

Care and consideration during and after target removal, especially backfilling holes, ensures continued access for prospecting and treasure hunting. This maintains the pristine condition of natural areas with minimal damage.

Minelab is committed to preserving the natural environment so that gold prospecting and treasure hunting can continue to be enjoyed. Every prospector, treasure hunter, and Minelab staff thank you for your efforts in protecting the environment.

?️ DETECTOR CARE AND SAFETY

The 'GP 3000' is a high-quality electronic instrument designed for professional gold prospecting, with electronics encased in a rugged housing. Follow these care instructions:

• Keep the detector clean and dry. Ensure all electrical connectors are clean and dry.
• The control box is water-resistant but not waterproof; avoid getting it wet.
• The coil is water-resistant and can be used in rain or wet conditions, but do not immerse it in water.
• Regularly replace items like teardrop washers and skid plates for longevity.
• Do not expose the detector to high temperatures or leave it in direct sun for extended periods. Shading is recommended. Do not leave the detector in a closed vehicle, especially in the sun.
• The coil housing can wear through if scrubbed on the ground; use a replaceable skid plate to protect coils.
• To prevent dirt ingress between the coil and skid plate, use silk tape (e.g., Leukosilk®). Other tapes may reduce sensitivity.
• Keep the control box and coil away from petrol or oil-based liquids. If contact occurs with corrosive substances (salt, salt water), wash with fresh water.
• Clean the detector with a damp cloth and mild soap detergent; do not use solvents.

Glossary of Common Terms

Halo Effect

After a metal object has remained undisturbed in the soil for a considerable amount of time, diffusion occurs around it, making the object appear larger to the detector.

Hot Rocks

Individual rocks with high mineralisation compared to the surrounding ground, which can cause false signals as the detector cannot ground balance on them.

Interference

Electricity or radio waves in the detection area causing instability or chattering of the detector's threshold. Common sources include power lines, underground cables, radar, other detectors, and thunderstorms.

Mineralised Ground

Ground containing minerals that can cause false signals. Heavily mineralised ground requires different processing than neutral or lightly mineralised ground. Ground with heavy salt concentrations requires separate processing.

Monoloop Coils

Coils where multiple strands of wire are wound in a single loop, creating a cone-shaped search field.

Non-Ferrous Metals

Metals not containing significant levels of iron, such as Gold, Silver, Copper, Brass, Lead, or Aluminium. They are non-magnetic.

Pinpoint

The method used to locate the precise position of a target before digging, utilizing the search coil's windings.

RX (Receive)

Refers to the response or electromagnetic field received back by the coil, used by the control box circuitry to detect a metal item.

Salt

High salt content in the ground affects ground balance similarly to mineralisation but causes a negative (-) response instead of a positive (+) one. Special filtering techniques are needed.

Search Coil

The circular plate swept across the ground that transmits electromagnetic signals into the ground and receives responses.

Search Pattern

The area of ground scanned by the coil during a sweep. The pattern varies depending on coil style (Double D or Monoloop) and Coil mode.

Target Response

The electro-magnetic effect generated by a metal target under the influence of the TX field.

Target Signal

The audio signal (or change in threshold) caused by a metal target as the coil passes over it.

Tracking

The Automatic Ground Balance function where the 'GP 3000' continuously adjusts to compensate for changes in ground mineralisation.

TX (Transmit)

Refers to the transmit signals or electromagnetic pulses sent into the ground by the coil.

Control Box

Encloses the detector's electronic circuitry, originating TX signals and interpreting RX signals. Contains all user-selectable functions.

Discrimination

The detector's ability to estimate if a target is ferrous (iron/steel) or non-ferrous (non-magnetic).

Double D Coils

Coils with two overlapping windings shaped like 'D's. Offer stability in mineralised ground, good depth, sensitivity, and thorough search patterns.

Electromagnetic Field

The field generated by the search coil, pulsed into the ground. A metal target disturbs this field, causing an audible signal.

False Signal

Signals that sound like target signals but are caused by other factors like incorrect ground balance, hot rocks, or coil impacts.

Ferrous Metals

Metals containing iron, attracted to magnets.

Ground Balance

The detector's ability to compensate for ground mineralisation, minimizing ground noise and maximizing sensitivity. The 'GP 3000' has automatic ground balance.

Introduction

The 'GP 3000' incorporates new technological advances and control functions, resulting in a detector that combines stable and effective ground balancing with depth and sensitivity.

About This Manual

This manual introduces the detector's features and provides step-by-step directions for assembly, adjustment, and basic to advanced detector use.

1. Introduction: Basic overview of the 'GP 3000' and this User's Manual.
2. Assembly: Details and instructions for assembling and adjusting the 'GP 3000'.
3. Battery: Information on the rechargeable battery pack, installation, use, and performance.
4. Controls: Familiarization with the 'GP3000' control panel features.
5. Detector Operation: Essential reading for all users, regardless of experience.
6. Detector Techniques: Basic and advanced techniques for effective use.
7. User Information: Glossary, user guides, technical specifications, warranty, and troubleshooting tips.

Accessories

Search Coils

The 'GP 3000' is supplied with 'GP 3000' 1100 and 'GP 3000' 1800 coils, specifically designed for its technology. Additional coil sizes will become available. Smaller coils offer greater sensitivity to small targets and are more maneuverable, while larger coils provide greater depth. Consult your Minelab retailer for the full range. Note that coils not specifically designed for the 'GP 3000' may have limitations and could cause instability or noise.

Batteries

Spare 12A/hr batteries are recommended for extended trips. A smaller, lightweight 4.5A/hr battery is also available, offering approximately 3-4 hours of running time and weighing 968g.

Corporate Clothing

Minelab offers quality clothing such as caps, shirts, and jackets. Inquire with your local dealer.

Introducing the Minelab 'GP 3000'

The Minelab 'GP 3000' utilizes "Dual Voltage Technology" (DVT), based on military Bi-polar technology. Key features include:

• NEW Low-Noise circuitry
• NEW battery harness
• NEW "Smart Point" diagnostic port
• DVT technology for optimum depth and sensitivity in all soil types
• Long-life 12A/hr Gel Cell battery
• Selectable Tx (transmit) modes (Soil Switch) for optimum performance in different soil conditions
• Selectable Rx (receive) modes (Coil Switch) for greater sensitivity and less susceptibility to interference
• Heavy Duty Bungy Strap

Compared to its predecessor, the 'GP extreme', the 'GP 3000' handles heavily mineralised and salty ground conditions with greater ease, opening up new detecting areas. Its new Low-Noise circuitry provides a smoother threshold, enhancing the ability to hear faint signals from small and deep targets, allowing users to revisit "worked-out" areas and find missed gold.

Minelab thanks you for purchasing their most advanced gold detector and is confident it will lead you to success in your quest for gold and treasure.

Contact Minelab

Minelab welcomes feedback. For questions or comments regarding the 'GP 3000' or other Minelab products, contact your local Authorized Minelab dealer or write to:

Minelab Electronics Pty Ltd

PO Box 537 Torrensville Plaza, South Australia 5031, AUSTRALIA

Email: ho@minelab.com.au | Tel: + 61 (8) 8238 0888

Minelab USA

2700 E Patrick Lane, Suite 11, Las Vegas, Nevada 89120, UNITED STATES OF AMERICA

Email: minelab@minelabusa.com | Tel: + 1 (702) 891 8809

Minelab International Limited

Laragh, Bandon, Co. Cork, IRELAND

Email: minelab@minelab.ie | Tel: + 353 (23) 52101

Visit the website for the latest information: http://www.minelab.com

Warranty

Repairs

If the detector requires service, fill out the Minelab Service Repair Form (or a photocopy) and enclose it with the detector. Provide as much detail about the fault as possible to assist service engineers.

Warranty Coverage

• The 'GP 3000' control box has a 2-year warranty covering parts and labour.
• The 'GP 3000' 1100 and 1800 coils have a 1-year warranty against malfunction.
• Warranty commencement is the date of purchase.
• The warranty does not cover damage caused by accident, misuse, neglect, alteration, modifications, or unauthorized service.
• Refer to the Product Warranty card for specific details.

Owner is responsible for all transport costs to Minelab. Repaired detectors are returned freight free.

NOTE: This warranty is not transferable or valid unless the enclosed warranty registration card is returned to Minelab Electronics Pty. Ltd. or an authorized distributor within 14 days of purchase.

Service Repair Form

This section describes the information required on the Minelab Service Repair Form for returning a detector for service. The form typically includes fields for:

• Today's Date
• Detector Model and Serial No.
• Purchased From and Purchase Date
• Faulty Part(s)
• Description of Fault
• Owner's Name, Address, Phone (Day/Home), Fax, Email

Detailed descriptions of faults are crucial for efficient repair.

Assembly

This chapter provides details and instructions on assembling and adjusting the 'GP 3000'.

Unpacking Your 'GP 3000'

The 'GP 3000' is shipped with the following main components:

• A. 11" Double D Coil with Skid Plate and Fibreglass Lower Shaft
• Other components as depicted in Figure 2.1 (Contents of the 'GP 3000' pack).

Complete Assembly Instructions

You will need to assemble the 'GP 3000' from its various components:

Assembling and fitting the armrest

1. Place the two armrest halves on either side of the upper shaft, ensuring bolt holes align.
2. Slide two nylon bolts through the holes and screw nylon wing nuts onto them a couple of turns.
3. Slide the 'T' section of the control box into the armrest (battery plug at the rear). Tighten wing nuts by hand.
4. Attach arm rest straps using the press studs on both sides of the arm rest.
5. Push arm rest straps through the slots in the neoprene arm rest cover, then push the cover over the arm rest.

Attaching the handle and bungy cord

1. Slide the handle onto the upper shaft and position it comfortably. Tighten the two screws in the handle base.
2. Slide the bungy cord knuckle of the bungy cord onto the upper shaft.

Assembling the Intermediate and Upper shaft sections

1. Slide the intermediate shaft into the end of the upper shaft and snap into place.
2. Check that the coil has a skid plate attached.
3. Check that the coil pivot end of the lower fibreglass shaft has two teardrop washers installed. Note: Washers should always be full thickness and replaced regularly as they wear out.
4. Push the lower fibreglass shaft into the mounting brackets on the coil, ensuring the spring clip at the rear faces the rear of the coil.

Attaching the coil

1. Line up the holes in the coil with the pivot end of the fibreglass shaft.
2. Push the nylon bolt through the holes and fit the nylon wing nut, then tighten by hand. Note: Do not over-tighten the nut, as the coil housing may be crushed or damaged.

Attaching the lower fibreglass shaft

1. Slide the lower fibreglass shaft into the intermediate shaft.
2. Adjust shaft length and coil angle for comfort. Minelab recommends a shaft length for a comfortable sweep of approximately 2 meters. Secure the lower shaft by locating the spring clip into the intermediate shaft holes and hand-tightening the locking nut.

Securing and connecting the coil cable

Always ensure the control box is turned OFF before connecting or disconnecting the coil.

1. Wind the coil cable around the shaft and plug the coil connector into the control box socket. Ensure the cable is wound firmly without strain, leaving enough slack near the coil for angle adjustment.
2. Fasten the cable into position using the provided Velcro straps.

Fitting and connecting the battery pack

1. Fit the battery into the back pack pouch.
2. Connect the headphones and the power cable to the appropriate sockets in the battery cap.
3. Put on the back pack.

If the coil cable is able to move around, especially near the coil, it can be 'seen' by the detector, causing confusing random noises.

Use only the 6v DC battery supplied.

Salty Environments: The 'GP 3000' can detect deeper in salty environments. However, high salt content can cause interfering signals that may not be fully balanced out by automatic ground balance. Hint: Change Soil switch to Salt setting for salty environments. Use specially designed 'GP 3000' range of coils.

Troubleshooting

Use the following table for suggested solutions to problems:

If returning your detector for service, supply as many details as possible about the fault to enable quick and efficient rectification by service engineers. Return the detector in a cardboard box with the Service Repair Form, including your name, address, phone number, purchase date, and serial number.

Technical Specifications

Patents Apply. In the interest of product improvement, Minelab reserves the right to make changes without notice.

Battery

The 'GP 3000' is supplied with a 6v DC rechargeable battery pack plus both mains and vehicle chargers. This chapter provides details on battery installation, use, and performance.

Battery and Charging

The Battery

The 6v DC rechargeable battery provides approximately 14-15 hours of operation when fully charged. It can be recharged at any time. Fully charge the battery before storage and do not leave it discharged for more than one day.

CAUTION: Never use a 12v DC battery, as this will damage the detector and is not covered by warranty.

Low Battery Indication

A series of signal pulses at 0.5-second intervals indicates when the battery level drops below the desired power for full function.

Important: When charging, the battery must be kept in an upright position.

Charging the battery

1. Turn the detector OFF before disconnecting the battery.
2. Disconnect the battery cable from the detector and connect it to the appropriate charger.

Caution: Do not leave the mains charger on for extended periods, as this may reduce battery life.

Battery Chargers

Two types of battery chargers are supplied: Mains and 12v Vehicle Charger.

Mains Battery Charger

Charges the battery from local mains (AC) power outlets.

1. Connect the mains charger to a mains outlet.
2. Switch the mains outlet ON.

Check the charger nameplate: 500mA chargers recharge a flat battery in approx. 20 hours; 1000mA chargers do so in approx. 10 hours. Partially discharged batteries require less time. For a 500mA charger, allow 1.5-2 hours charging per hour of use; for a 1000mA charger, allow 0.5-0.75 hours per hour of use.

Vehicle Battery Charger

Charges the battery from a vehicle's cigarette lighter socket.

1. Connect the charger to the cigarette lighter socket and turn the ignition switch to Accessories.

This supplies 12v DC power, converted by the charger for the battery. A red LED indicator flashes during charging; it may appear constant when the battery is flat and slows as it charges. Allow approx. 10 hours for a full charge.

If the vehicle's battery voltage drops below 11v, the charger will stop operating. Ensure your vehicle battery is in good condition before camping in remote areas. Run your engine above idle speed for at least 30 minutes daily to keep the vehicle battery charged.

The Vehicle Battery Charger is designed for vehicles with a negative earth electrical system. Connecting to a positive earth system may blow the fuse and prevent the LED indicator from lighting.

Detecting Techniques

Hints and techniques for better detecting and happy prospecting, utilizing the power of your 'GP 3000' with DVT.

Check your footwear

Note: When detecting, do not wear steel cap boots or shoes with metal eyelets!

Some user tips:

• Wear the battery in the supplied backpack to place it at the furthest practical distance from the coil.
• Ensure the shaft length is not set too short.
• If the coil is too close to your body, it might detect your pick, the battery, or other carried metal items. If false signals occur, check for metal items you are carrying. Move the coil closer and further away from your body to test if signals originate from these items. Increase the distance if necessary.

Motion detection

The 'GP 3000' is a 'motion' detector; the detector must be moving over a target to detect it.

Parallel Sweeping Procedure

Figure 6.1 Parallel Sweeping

• Sweep the coil over the ground in a side-to-side motion.
• Keep the coil parallel to and at the same height from the ground at all times. Lightly skidding the coil can sometimes help, depending on mineralisation.
• Do not raise the coil at the ends of each sweep, as this reduces detection depth and may cause false signals.

Covering the search area

Figure 6.2 Search path & Figure 6.3 Search area from 3 directions

• As you move forward slowly, the search pattern should resemble a snaking path.
• To ensure thorough searching, approach the area from 3 different directions.

Overlap each sweep

• Each sweep of the coil should overlap the area covered by the previous sweep for full coverage.
• Be aware of the coil's search pattern and overlap sweeps accordingly.
• See also Pinpointing Technique, pages 43 and 44.

Controls

It is important to familiarize yourself with the features of the 'GP 3000' control panel. A few minutes spent reading this chapter will be a worthwhile preliminary to detecting.

Detector Sounds

Threshold and Tone

This is the background sound produced by the detector. The level is set using the Threshold control, and the tone is set using the Tone control.

Target Signal

This is the abrupt change in tone and volume of the threshold sound when a target is detected.

• Maximum level is set by the Volume control.
• Amount of tone variation is set by the Signal control.
• If the tone falls first and then rises as the coil passes over a target, it generally indicates a small target.
• If the tone rises first and then falls, it generally indicates a large target.

Ground Noise

Irregular noises difficult to pinpoint, caused by changing ground chemistry or 'mineralisation'. These effects are greatly reduced when the Balance switch is set to Tracking.

Tune Indication

An initial beep sounds while the detector tests frequencies for stability. The threshold may become quiet or chattery. Three sharp 'beeps' indicate completion.

Low Battery Indication

A series of signal pulses at 0.5-second intervals indicates low battery level.

Control Functions

There are two control panels: the rear panel and the front panel.

Rear Panel

Figure 4.1 Rear Panel

• Tune: Reduces electromagnetic interference.
• Iron Discriminate: Selects between All Metal or Disc modes.
• Soil: Optimizes detector for different soil conditions (Normal, Sensitive, Salt).
• Coil: Changes coil's electromagnetic field for different environments (Double D, M/Mono, Cancel).
• Balance: Selects between Fixed or Tracking ground balance.
• Coil Connector: Port for connecting the coil.

Power (On/Off) Switch

Figure 4.2 Power (On/Off) switch

This switch turns the detector's power ON and OFF. Note: Always switch the detector OFF before connecting/disconnecting the coil or battery pack, and when not in use.

Boost (Shallow/N/Deep)

Figure 4.3 Boost switch

Enhances signals from different target types:

• Shallow: Amplifies signals from small, near-surface objects, ideal for 'quiet' ground. May also boost ground noise.
• N (Normal): Responds to all signals without boosting; suitable for general detecting.
• Deep: Smooths threshold and target signals, making small changes easier to hear, suitable for large targets at depth in 'noisy' ground. May mask very small, near-surface targets.

When Boost is changed, Threshold may also need adjustment.

Threshold

Figure 4.4 Threshold control

Adjusts the background audio signal or 'threshold' level. Set just above the point where the threshold is audible and stable, ideally a smooth, gentle hum. Prolonged use should not be irritating.

Small or deep targets may cause only small variations in the threshold. If set too high or too low, these variations may be missed.

Figures 4.5-4.7 illustrate threshold levels relative to audible signals.

Level Adjust Control

Figure 4.19 Level Adjust control

Allows selection of sensitivity and likelihood of a target being discriminated as ferrous (in Disc mode). Affects response to ground mineralisation versus metal targets.

• Fully anti-clockwise: All targets detected, but some iron may give a normal signal.
• Fully clockwise: Little iron detected, but some small non-ferrous targets may be mistaken as ferrous.

Turning anti-clockwise increases the signal strength required for iron discrimination. Level Adjust also affects Tracking mode. Setting it fully clockwise makes it unlikely to 'balance out' genuine targets, though ground noise may still cause false signals. Setting it fully anti-clockwise effectively balances out ground noise but may miss faint target signals.

HINT: It is usually best to dig out all targets and use discrimination only where excessive rubbish makes digging everything impractical.

NOTE: Discrimination functions work with strong, positive target responses. Weak responses yield normal 'all metal' signals.

Iron Discriminate (All Metal/Disc)

Figure 4.18 All Metal/Disc switch

Selects between discrimination or turning it off (All Metal). In All Metals, signals vary in volume and pitch but don't indicate metal type. In Disc mode, a strong ferrous (iron) response causes the threshold to be 'blanked' or silenced.

NOTE: If a target response is too weak for discrimination, the detector gives a normal target signal.

Soil (Normal/Sensitive/Salt) switch

Figure 4.20 Soil (Normal/Sensitive/Salt) switch

Optimizes detector for different soil conditions and targets:

• N (Normal): Versatile for all areas, including highly mineralised soil. Good sensitivity to various nugget sizes.
• Sensitive: For small nuggets, especially in highly mineralised soil. Offers stability for closer ground use in excessive ground noise. May not work well in salty ground and may reduce depth for large nuggets.
• Salt: For areas with high salt content, neutral or heavily mineralised. May be less sensitive than Normal or Sensitive in highly mineralised areas without salt.

Signal Pitch

Figure 4.12 Signal control

Adjusts the pitch response of the target signal. Figures 4.13 and 4.14 show pitch variance. At minimum, pitch variance is reduced; at maximum, it is increased.

Tone

Figure 4.15 Tone control

Adjusts the tone of the threshold to a comfortable level for hearing. At minimum, it's a low tone; turning clockwise increases pitch. A high pitch may be fatiguing but is better for identifying faint signals.

Volume

Figure 4.8 Volume control

Sets a maximum limit on target signal loudness. Figures 4.9-4.11 illustrate volume levels.

• Maximum volume: Signal is unaltered, proportional to target size/depth.
• Half volume: Signal unaltered for small targets, limited for larger ones.
• Near minimum volume: Limits all signals, potentially losing most targets.

NOTE: Threshold should be reset after adjusting Volume.

Iron Discrimination

Discrimination distinguishes between metal objects, helping identify targets. The 'GP 3000' rejects iron while detecting non-ferrous metals, useful in littered goldfields.

Figure 5.3 illustrates discrimination levels. In 'Disc' mode, a ferrous target signal blanks, while a non-ferrous signal is steadier.

Ground Balancing Procedure

Figure 5.2 Setting the ground balance

Move the coil 20-100mm above the ground and change Balance from Fixed to Tracking. Fast ground balance takes 5 seconds (coil must be moving). Continue moving the coil until ground noise stops. A persistent signal may indicate a target. If so, move to a new location and repeat. The detector is 'ground balanced' when there's no change in threshold while raising/lowering the coil. You can then select Fixed or Tracking for detecting.

Use Tracking in mineralised or variable ground. Use Fixed in mild ground, switching to Tracking temporarily if noise increases. Do not test targets by switching to Tracking when the coil is above them.

HINT: Repeat ground balance if ground conditions change rapidly.

Tune

Figure 4.17 Tune control

Reduces electromagnetic interference. Automatic tuning starts by pressing the Tune switch. The process takes approx. 60 seconds, indicated by three beeps. Tune initially with Coil switch in Double D or M (Mono). If interference persists, switch to Cancel and re-tune.

Tuning Procedure: Hold detector at waist height, coil vertical. Move coil in a half-circle around your body. When interference is loudest, stop, hold motionless, and press Tune. The detector selects the best frequency. Keep coil motionless and clear of metal objects during tuning.

IMPORTANT: When tuning near other detectors, take turns. Do not tune two detectors simultaneously.

Operation

However experienced you are at using a metal detector, it is important that you read this chapter to understand how to use the 'GP 3000' to its full capacity.

Quick Start Instructions

1. Set Coil switch to Double D.
2. Set Soil switch to N (Normal).
3. Set Balance switch to Fixed.
4. Set Iron Discriminate switch to All Metals.
5. Set Boost to N (Normal) for general detecting.
6. Set Volume to maximum, and Signal to 2 o'clock.
7. Turn Power switch ON.
8. Adjust Threshold control so a faint sound is heard.
9. Adjust Threshold Tone to suit hearing.
10. To tune: Hold detector at waist height, shaft horizontal, coil vertical. Move coil in a half-circle around body until interference is loudest. Hold motionless and press Tune switch. Tuning takes approx. 60 seconds (indicated by three beeps).
11. For Discrimination: Change Iron Discriminate to Disc and set Level Adjust to mid-range.
12. Set Ground Balance: Move coil up and down. While moving, change Balance from Fixed to Tracking.
13. Once ground balance is achieved, switch back to Fixed.
14. The detector is now ready for operation.

Detailed Operating Instructions

Turn the 'GP 3000' On

Hold the coil away from the ground and metal objects, then switch Power to On. NOTE: When the 'GP 3000' is turned OFF, important information (e.g., tuning frequency and ground balance) is saved in internal memory. If detection recommences in the same location, re-tuning or re-ground balancing may not be necessary.

Set the Volume Control

Set Volume so target signals are clear and easy to hear, but loud signals are not uncomfortable. Pass the coil across a large target and adjust volume to a comfortable level, then test with a small target.

Set the Threshold control

Adjust Threshold until it is just audible through headphones. NOTE: Small surface objects and large deep objects produce very small threshold changes. Set correctly to ensure these targets are heard. Experiment with known targets to assist in setting controls.

Prospecting Techniques

The 'GP 3000' offers superior ground balancing, enabling detection of large objects near the surface in well-worked areas where other detectors struggle with high mineralisation and/or salt. Dig all target signals, even in previously detected areas.

For Maximum Gold Recovery

• Keep the coil as close to the ground as possible.
• Listen very carefully – this is more important than looking.
• SLOW DOWN! Do not rush; take your time.

Sudden or large changes in ground mineralisation can produce signals. In Victorian goldfields, responses may come from orange/reddish dyke material or clay. In Western Australia, pockets of dark orange/reddish colouration can cause signals. Detecting with contours rather than across changes can stabilize effects in variable mineralisation. In heavily mineralised ground, sweeping the coil 1-2 cm above ground may provide a more stable threshold and less noise. Charcoal can produce signals similar to metal objects; the signal vanishes if the charcoal is disturbed. If in doubt, scrape soil above the signal; if it strengthens, it's likely a target.

Identifying Target Signals

Metallic targets usually produce a 'solid', sharp, symmetrical signal. Ground noises are broad and uneven. Investigate uncertain sounds by scraping a shallow hole (70-100mm) and sweeping the coil over it at ground level. If the signal decreases, it's likely ground noise. If it remains or increases, it's likely a metallic target. Deeper holes and re-testing may clarify. Mineral noises can be directional.

A 'halo effect' can make buried objects appear larger. This effect reduces once the target is disturbed. Reburying an object will cause the halo effect to disappear.

HINT: Avoid balancing out faint ground noise, as it might also cancel a deeply buried target response.

Recovering the Target

Once a target location is sure, dig a small hole to preserve the environment. Always replace soil and grass. Essential digging tools include a spade, pick, shovel, or crowbar for hard ground.

1. Before digging, clear loose surface material and check the signal. If it's gone, the target is likely in the surface material.
2. If the signal persists, dig to approx. 50mm depth.
3. If the target is not visible, sweep the coil over the hole.
4. If the signal is not heard, the target should be in the dug pile.
5. Check the soil under the pile for objects.
6. Dig carefully to avoid damaging nuggets. Start digging approx. 100mm in front of the target.
7. Pile diggings carefully for searching.
8. If the target is in the removed soil, sweep the coil over the pile and pinpoint its exact position.

After recovery, sweep the hole again to ensure no other targets remain. If an object is found in a specific location, search the surrounding area carefully, as more objects may be nearby. If a target signal is heard, keep searching until the object is found.

REMEMBER: Always refill holes and dispose of rubbish properly to maintain a good reputation for metal detector users, ensuring continued access to prospecting areas.

Recovering Deep Targets

The 'GP 3000' has capabilities for surprising depth. For deeply buried targets:

1. Use cross sweeping to locate the target accurately.
2. Dig a hole approx. 100mm deep to insert the coil.
3. Continuously test the target location as you dig deeper.
4. Ensure the target is not in the hole's wall; you might dig past it. Re-pinpoint to check hole position.

Pinpointing

To find an object and reduce hole size, pinpoint its exact location. After confirming a target with ground balance, set Balance to Fixed for accurate pinpointing. Sweep the general area, noting where the strongest signal is received. Shorten sweeps to draw an imaginary line of the strongest signal. Line up the target at 90° from the initial direction and repeat. The object is where the two lines cross (see Figure 6.4).

NOTE: Pinpointing may not locate a target in the coil's centre if the Coil switch is set to M (Mono) or Cancel.