Frequently Asked Questions

General Detecting Questions & Tips.

Frequently Asked Questions

The experienced detectorists at Minelab have put together a comprehensive list of FAQs on how to use a metal detector. These also contain many pro tips for metal detecting.

You may find the answers to your questions by reading the FAQs here. Of course, if, after reading through this information you still have a question, please feel free to contact us.

General Detecting Questions and Tips

Can Minelab Metal Detectors Tell What A Target Is Likely To Be Before I Dig It Up?

Yes, Minelab metal detectors have the ability to ‘discriminate’ between different types of targets. The discrimination feature on Minelab detectors measure two target properties, ferrous properties and conductive properties.

Ferrous properties refer to how much iron is in a target and therefore how strongly it’s attracted to a magnet. Ferrous targets tend to be trash, so can be discriminated/masked out based on their ferrous properties alone by the detector. Conductive properties refer to how well a target conducts electrical current and therefore responds to a metal detector’s magnetic field. Trash like nails and foil have different conductive properties to valuable targets like coins and rings. In this case the metal detector can make a judgement as to whether the target is trash based on conductivity.

The process for configuring the discrimination settings and the method used to indicate treasure or trash varies across the Minelab range of detectors.

What Effects Do Different Operating Frequencies Have?

As a rule of thumb, the lower the frequency used by the detector, the deeper it can penetrate the ground. At low frequencies however, sensitivity to small low conductive targets is reduced. The higher the frequency, the higher the sensitivity to small targets, but will not penetrate as deeply. In general, gold detectors operate at higher frequencies (to find small nuggets), while coin and treasure detectors work at lower frequencies for deeper penetration. The exception to this is MPS type metal detectors that are sensitive and deep seeking simultaneously.

How Do Different Coils Affect The Performance Of A Metal Detector?


The size of a search coil can influence the detection depth or sensitivity of a metal detector. The larger the coil, the deeper it detects, but will have less sensitivity to small targets. Conversely the smaller the search coil’s diameter, the more sensitive it becomes but looses detection depth.

Smaller coils are lighter, easier to control and may be chosen for their ability to negotiate difficult terrain or undergrowth. They are also an advantage in areas of high trash.


The most common coil shapes are conventional solid round coils, elliptical shaped coils and the open web coils. The main reason for the change in shape is to conform to a physical requirement, i.e. an elliptical coil can be pushed around bushes or between rocks easier than a round coil and open web coils move through water easier and are lighter. Conventional round coils are often more stable and perform better and are particularly popular for gold prospecting.


The three most common types of coil windings are Concentric, Double-D, and Monoloop. The difference between these coil types is the pattern the wire is wound within the search coil.

Concentric coil

A Concentric coil has an inner circle and an outer circle wire winding. Its search pattern is cone shaped and can be useful for accurately pinpointing a target. Concentric coils tend to be noisier in highly mineralised ground and require more over lap of sweep for thorough ground coverage.

Double-D coil

Double-D coils are the preferred coils for most detecting. They give a blade or chisel shaped signal that covers the ground more uniformly and once an operator becomes accustomed to the signal, pinpointing can be very accurate. Double-D coils are also preferred for their superior ground balancing ability.

Monoloop coil

Monoloop coils have one winding of wire around the circumference of the coil, which is used to both transmit and receive. The signal pattern of the Monoloop coil is cone shaped, requiring more overlapping. In extremely heavily mineralised grounds they can be more difficult to ground balance, however they tend to provide slightly better depth than the Double-D coils.

How Often Should I Clean Out My Skidplate?

Dirt, dust and moisture can be trapped inside the skidplate leading to false signals and poor performance. To maintain peak performance of your Minelab detector, it is recommended to clean out the skidplate quite regularly.

How Do I Know If My Coil Is Waterproof Or Not?

Check the coil selection guide to find the most suitable coil for your detecting needs.

What Advantages Does FBS Have Over VFLEX?

  • Highly accurate Discrimination
  • No need to Ground Balance
  • Superior Depth on large targets
  • Very stable operation on salt beaches
  • Superior Iron see-through (CTX 3030 is best)
  • Maximum depth on a broad range of target sizes

What Are The Recommended Impedance Values Of Headphones For Each Detector?

Headphone specifications are not really critical in a metal detector as their audio circuitry does not produce Hi-Fi quality sound. e.g. Our detectors frequency output range is only circa 75 -1200Hz

Our audio circuits will drive most headphones from 16 – 100 + ohms.

Audio optimisation is also very subjective as everybody hears differently.

We endeavour not to confuse our customers with unnecessary technical specs because in reality there is no honest way to determine what headphones are best for you other than to try them.

If you have a detector with adjustable audio tones, such as a CTX 3030, we would also recommend you spend some time to ensure the detection tones are optimised for your hearing needs.

How Deep Will My Detector Go?

There is no specific answer to this question as it depends on the target size, orientation, metallic content, ground minerals and conductivity, electrical and ambient noise in the area and etc.

However we commonly hear of GPX Series detectors finding large gold nuggets at 3 and sometimes 4 feet deep, and CTX 3030s finding coins and rings at over 12 inches.

How Often Should I Send My Detector Back For A Service?

Only if it becomes faulty.

How Often Should I Ground Balance, Where Should I Ground Balance?

On some detectors you don’t need to ground balance at all. On others, users new to detecting are recommended to use the Ground Balance Tracking function.

In Tracking, the detector will automatically ground balance for you and remain in balance even if the ground minerals vary. On manual ground balance detectors like the X-TERRA 305 and X-TERRA 505, you need to ground balance at the start of every hunt, and re-balance periodically as required. Always ground balance on clean ground, away from metal objects.

Why Can’t My Detector Detect A Gold Chain?

Gold chains are very difficult to detect, particularly very fine chains. Each link of a chain can be very small and the detector sees each link as a separate target, so it can easily be missed. You are more likely to detect the actual clasp or any pendants that may still be on the chain as these are much larger than the individual chain links. High frequency detectors such as the Eureka Gold, or an X-TERRA 705 with an 18.75 kHz coil in prospecting mode, will often pick up fine chains better than most coin detectors.

Why Does My Detector Pick Up Some Coke?

Coke is carbon and as such can be quite conductive, just like a coin.

What Is Your Deepest Detector And Can It Detect Through Rock?

The GPZ 7000 is our deepest detector in all ground conditions and can detect through even highly mineralised rock.

I Would Like To Extend My Coil Cable, Can This Be Done?

No, cable characteristics are matched to coil windings at manufacture, so extending the cable will reduce the performance of the coil.

Can You Recommend A Good Coil For Trashy Ground?

Smaller coils are better for trashy sites, as they reduce the instances of detecting multiple targets at once. Concentric coils are generally better than Double-D coils for this same reason.

Check the coil selection guide to find the most suitable coil for your detecting needs.

Why Does My Detector Pick Up Signals In The Air?

Metal detectors pick up electromagnetic signals from underground metal objects. Similar signals can also be received through the air from other electromagnetic sources, such as power lines, radio transmitters, generators, etc.

How Will I Know If The Ground Is Mineralised?

If your detector is noisy when you are detecting, but goes quiet when you stop sweeping the coil, then it is receiving signals from mineralized ground. Perform a ground balance and continue detecting.

GPX series only: if it is still noisy then you may need to try an alternate soil/timing selection. All other detectors: if it is still noisy you would need to reduce your sensitivity to the highest stable sensitivity level.

Is It Possible To Miss Good Targets With Preset Discrimination Patterns?

The only guaranteed way to get every possible good target is to use no discrimination. However, digging every target can waste lots of time. Discrimination patterns are always a compromise between digging most good targets and ignoring most junk targets.

Sometimes I Dig What Seems To Be A Good Target And Then Cannot Find Any Metal, Why?

This can be caused by a number of reasons:

  • Sometimes rusty objects get broken up during the digging process
  • Metal objects can leach trace elements into the surrounding soil
  • Some rocks can sound like targets
  • Some targets get ‘lost’ or reburied during the digging process

Why Do I Sometimes Get A Signal At The End Of My Swing?

Usually because you are lifting the coil at the end of your swing. Always sweep slow, low and level for the entire swing.