Minelab GT 16000 Ground Tracker

Introduction

The Minelab GT 16000 Ground Tracker represents a significant advancement in high-performance metal detection technology. Building upon the success of previous models, Minelab engineers have developed a detector featuring true automatic ground balancing without compromising sensitivity. This manual provides detailed instructions for assembly, operation, and maintenance of the GT 16000.

General Description

Unlike many detectors that use fixed ground balance settings or reduced sensitivity, the GT 16000 utilizes a microprocessor to perform automatic ground balancing with precision and speed, mirroring manual operation but continuously and tirelessly. This Automatic Ground Tracking allows users to cover more ground more efficiently. The detector is designed to be user-friendly, enabling novice users to achieve results comparable to experienced operators. Key features include high sensitivity, superior ground noise rejection in mineralized soils, rugged construction, and a variable discriminator. It offers selectable audio output modes, including a signal booster and an 'enhance' mode for identifying small objects. The unit can be configured for either shaft-mount or hip-mount operation.

Basic Operation

Assembly Procedure

Upon unpacking, verify that all included parts are present: Instruction Manual, Warranty Card, Control Box, Main Shaft, Arm-rest, Search Coil and Cable, Lower Shaft, Bag, Extension Cable, and Skid Plate. It is advisable to retain the original packaging for future use. Complete and mail the warranty card.

Assembly Steps:

1. Slide the Lower Shaft (containing the Search Coil and Cable) into the Main Shaft to a comfortable position, ensuring it 'clicks' into place. Secure by tightening the locking nut by hand.
2. Slide the Arm-rest onto the back of the Main Shaft, ensuring it 'clicks' firmly at a convenient position. The arm-rest can be adjusted by bending it.
3. Attach the Control Box to the Main Shaft at a suitable distance from the handle grip for easy access to controls. Ensure connection surfaces are clean.
4. Wind the Search Coil cable around the shaft, securing it with tape to prevent movement and snagging. Connect the cable plug to the socket on the Control Box.
5. Attach the Skid Plate to the Search Coil to protect it from abrasion and wear.
6. Install the batteries as described in Section 2.4.

Figure 1: GT16000 Assembly Diagram shows the connection of the main components: control box, shafts, arm-rest, and search coil.

Start-up Procedure in Basic Search Mode

Ensure the detector is correctly assembled and all cables are secure. Adjust the Arm-rest, Control Box, and Search Coil angle for comfortable operation.

Figure 2: GT16000 Control Panel illustrates the layout of controls including Volume, Ground Balance, Soil Switch, Discriminator, Sensitivity, and Threshold.

Recommended Control Settings:

• SOUND Switch: "Normal"
• GROUND BALANCE Switch: "Track GB, Motion"
• SOIL Switch: "Normal"
• DISCRIMINATE Knob: "All Metal"
• SENSITIVITY Knob: Approximately 80% of maximum.

Hold the Search Coil level, facing away from metallic objects. Turn the Volume Knob clockwise to switch on the detector. The unit will begin operating after a few seconds. Adjust the Threshold Knob to a soft, comfortable audio level. Readjust the Volume Knob for a comfortable listening level when sensing a large metal object. The Threshold may need further adjustment.

To rapidly Ground Balance, hold the RESET switch in the 'Up' position while moving the coil between 3 and 10 cm above the ground. The sound will diminish as the coil moves. Once the sound almost vanishes, the detector is ground balanced. Release the RESET switch. The detector will automatically ground balance with use even if the RESET switch is not manually engaged.

The detector will now Automatically Track the ground balance without loss of sensitivity as ground conditions change.

Headphone Socket

Located on the bottom right of the front panel, the headphone socket accepts most 1/4" mono and stereo headphones. Using headphones disconnects the loudspeaker, conserves battery, and reduces distraction from external noise. Set any headphone stereo/mono switch to 'Stereo'.

Batteries

The GT 16000 features an automatic battery low alert, indicated by a distinct 'pip' sound at approximately 20-second intervals. This indicates about 15-20 minutes of remaining battery life. The detector uses eight 1.5-volt AA penlight batteries. Alkaline batteries are recommended for their leak resistance. Remove batteries if the detector will not be used for an extended period. Rechargeable NiCad cells provide approximately 6 hours of use when new, decreasing by about 45 minutes after 300 cycles.

Figure 3: Battery removal and installation shows how to access and replace the battery packs within the control box.

Explanation of Controls

3.1 VOLUME Knob and On/Off

The detector is switched ON by turning the knob clockwise past a slight resistance point. The best audio results are typically achieved with the knob set between half and maximum, especially when using headphones.

3.2 SOIL Switch

This switch has two positions: 'Normal' and 'Difficult'. Use 'Normal' for clear ground. Select 'Difficult' for ground with high concentrations of ironstone or mineralization. The 'Difficult' setting slightly reduces sensitivity. If excessive noise persists, reduce sensitivity using the Sensitivity knob.

The detector may emit a high-pitch 'chirp' if it overloads, which can happen when the sensing head is too close to a large object or very 'hot' ground. If this occurs, move the head further away or set the Soil Switch to 'Difficult'.

3.3 SENSITIVITY Knob

Turn clockwise for maximum sensitivity. For most ground conditions, a setting of 80% of maximum is recommended. Adjust downwards in poor ground conditions (heavy mineralization or ironstone).

3.4 SOUND Switch

Offers three audio output modes:

• Normal: Standard response where signal loudness increases with signal strength.
• Boost: Amplifies the output signal for greater depth penetration in quiet soils. May cause spurious noise in variable ground.
• Enhance: Designed for small to medium nuggets in variable ground. It alters the frequency of the response, making the ear more sensitive to subtle changes. May be less effective in grounds with many 'hot rocks'.

3.5 THRESHOLD Knob

Set this knob to a point just past where the tone is audible, but not so loud as to be irritating during prolonged use. In 'Fix GB, Non-motion' mode, press the RESET switch before setting the threshold.

3.6 DISCRIMINATE Knob

This control aids in gold prospecting. It is 'off' or in 'All metal' mode when turned fully anticlockwise. The discriminator is disabled in 'Fix GB, Non-motion' mode.

• Turning the knob clockwise to setting '1' enables ferrous/non-ferrous discrimination, with ferrous objects producing a distinct sound.
• Further clockwise turns increase the range of materials discriminated.
• Increasing sweep speed can improve discrimination depth.
• The discriminator automatically adjusts its power based on ground interference, providing reliable discrimination depth even in 'hot' ground. An audible 'object' sound is always heard without loss of sensitivity.

Ground Noise Rejection

The GT 16000 excels at rejecting ground noises. Proper ground balancing is crucial for detecting valuable targets.

4.1 Automatic Ground Balancing (AGB)

The Ground Balance Switch offers three modes: 'Track GB, Motion', 'Fix GB, Motion', and 'Fix GB, Non-motion'. The RESET switch can be used to force rapid ground balancing in 'Motion' modes.

Figure 4: Automatic Ground Balancing (AGB) procedure illustrates the process of using the RESET switch and coil movement to balance the detector to the ground.

The AGB procedure is recommended for the 'Track GB, Motion' mode, which is suitable for most searching. In 'Fix GB, Motion', the AGB procedure may need to be repeated more often in variable ground.

4.2 Automatic Ground Balance Tracking (AGB Tracking)

This mode is selected using the 'Track GB, Motion' setting on the GROUND BALANCE switch. The 'Motion' aspect means a signal is only heard when the Search Coil moves relative to a detected object. This mode continuously adjusts ground balance as ground characteristics change, minimizing spurious noises and maintaining effective detection depth. It offers an average ground balance setting for the recently covered area, smoothing out ground noises while providing a clear target signal.

While the 'Track GB, Motion' mode can be used without the RESET switch, it can be beneficial to use it if ground conditions change suddenly. The detector may temporarily inhibit AGB tracking when it recognizes an object sound, but tracking resumes shortly after. For maximum effectiveness in highly variable ground, use 'Track GB, Motion' with the 'Enhance' sound mode.

4.3 Searching Modes

The Ground Balance Switch determines the search mode:

• Track GB, Motion: Recommended for most ground conditions. Automatic ground balancing and tracking.
• Fix GB, Motion: Ground balance is fixed after an AGB procedure. Suitable for areas with many ferrous objects where continuous adjustment might be preferable.
• Fix GB, Non-motion: Static mode with fixed ground balance. The signal is maintained when the coil is stationary over a target. The discriminator is disabled. Useful for pinpointing or searching small areas in hot ironstone conditions.

Detection Tips

5.1 General

For optimal performance, the GT 16000 should be ground balanced with the search coil approximately 2 cm (1 inch) above the ground and maintained at this height during sweeps. Consistent coil height is crucial to avoid confusing sounds and loss of depth.

Figure 5: Maintaining Search Coil parallel to ground illustrates the importance of consistent coil height during sweeps.

5.2 Pinpointing an Object

Familiarize yourself with the detector by digging all object signals. This builds experience with audio signals and ground noises.

To pinpoint small objects with 'double-D' coils, use the 'Fix GB, Non-motion' mode. Reset the detector near the object. Pass the head slowly over the object, holding it at the maximum sound position. Draw a line on the ground along the shaft's direction. Repeat this from a right angle to obtain a second line; the intersection indicates the target's precise location.

Figure 6: Hole and overburden description shows how to prepare a site for excavation by removing topsoil.

Figure 7: Finding an object illustrates the process of locating a small object by repeatedly halving soil samples.

When an object is removed, lay the coil nearby and pass soil samples over it to locate the object. This process may affect ground balance in 'Track GB, Motion' mode. Always fill in excavated holes to prevent hazards and environmental damage.

5.3 Recommended Technique

Scan areas with broad, even sweeps, keeping the detector head at a constant height (approximately 2-3 cm) above the ground, adjusted for ground conditions and obstacles.

Figure 8: Recommended searching technique shows overlapping sweeps and searching from multiple directions to identify gold.

If gold is found, search the area from three different directions, as ground noises can vary and mask signals. Searching from multiple directions helps ensure that signals are not missed.

5.4 Ground Noises

Distinguishing between target signals and ground noises is key. Mineralized ground can produce broad, low-volume signals. Charcoal can sound like a metallic object when close to the surface.

Hot Rocks: Rocks rich in iron can produce strong audio signals. If unsure, use the 'Difficult' soil setting and reduce sensitivity. If the signal persists, break the rock and test each piece. This helps determine if gold is present.

Negative Hot Rocks/Ground Holes: These cause a reduction in sound as the coil passes over them. The detector may produce a signal when recovering from this loss of sound, which can be mistaken for an object. Use 'Fix GB, Non-motion' mode to identify these by the drop in sound intensity.

5.5 Clay Domes

These are regions of soil mineralization that can be confused with signals from deep nuggets. To identify them, remove about 4 cm of soil in a 30 cm diameter circle. Attempt to ground balance the signal. If ground balance is achieved, it is likely clay, as metal objects do not typically allow for ground balancing when brought closer to the coil.

5.6 Searching for Gold

To find gold, search areas known for coarse gold or likely gold-bearing fields. Coarse gold ranges from grains of wheat to many grams. Nugget-bearing areas often result from broken-down gold reefs containing quartz and ironstone.

The GT 16000 offers significant advantages in prospecting, allowing rapid scanning and efficient ground coverage, especially in areas with heavy ironstone concentrations, which often accompany gold. The detector's ability to maintain accurate ground balance in these conditions allows for both depth and coverage.

Proper Care of Your Detector

The GT 16000 is a high-quality electronic instrument. Proper care involves common sense:

1. Do not leave batteries in the control box if the detector is unused for over two weeks to prevent damage from leaks, which would void the warranty.
2. Avoid leaving the detector in direct sunlight for extended periods, especially in hot temperatures. Cover it from direct sunlight.
3. Use a skid plate to protect the search coil housing from wear. Replace the skid plate when worn.
4. The provided bag protects the control box from dust, mist, and rain, and cushions it from knocks. Use the bag whenever possible.
5. The control box is water-resistant but not waterproof. Avoid unnecessary wetting. Keep it away from petrol or oil-based liquids.
6. If the search coil is used in salt water, wash it with fresh water afterwards.
7. Keep the unit dry and clean. Avoid getting sand into shafts or nuts. Clean with a damp cloth and mild soap; do not use solvents.

Warranty and Service

The GT 16000 comes with a one-year parts and labour warranty for the control box and a three-month warranty for the search coil. Refer to your warranty card for details. Contact your supplier or Minelab for service.

Specifications (GT16000 Ground Tracker)

Note: Specifications are subject to modification without notice.

Accessories and Options

A full range of accessories and options is available, including replacement instruction books, padded headphones for noisy areas, pick-belts, and lightweight carry bags for protection and convenience.

Minelab's NEW "BIG SIGNAL" amplifier is designed to amplify weak signals, increase depth detection, and improve sensitivity. It is compatible with all Minelab detectors and fits most other brands/models.

If parts, service, or accessories cannot be obtained from a local dealer, contact Minelab directly via phone.