If there is one thing we can all agree on, it is just how addictive metal detecting can be. Whether it’s gold prospecting, treasure hunting on the beach or searching fields for lost Roman artefacts, once you get started it’s hard to stop. For beginner detectorists, once you have learnt your machine, adding a different coil to your arsenal is a great option to improve your detecting odds and productivity.
However, with so many different coil types out there, it can be a daunting task to select the best one for you. Today we’ll take you through the different coil sizes, shapes and construction to help you pick the best one for you and your detecting.
SIZE
The size of a coil can influence the detection depth and sensitivity of a metal detector. A good rule of thumb is ‘the larger the coil, the more ground you can cover and the deeper it can go’. This sounds like the be all and end all, but the extra depth comes at a price. Large coils have less sensitivity to smaller targets and a greater susceptibility to Electro Magnetic Interference (EMI), meaning you may have to notch that sensitivity right down, depending on the interference of the location.
On the other hand, smaller coils have greater sensitivity to smaller, shallow targets and are less susceptible to EMI. There’s also the added benefit that small coils can fit in very confined areas.
For coin and treasure detecting, the larger coils are best where you want to cover large areas quickly, where smaller coils are great if you’re in areas with lots of shallow targets mixed in close proximity with undesirable iron targets.
For gold detecting, generally you will be in remote areas that have little to no EMI, so a large coil will give you more ground coverage with maximum sensitivity and depth. While smaller coils will provide increased sensitivity to small nuggets close to the surface.
SHAPE
Coil shape can be an important factor. Circular coils are the most common because they are stable and offer the best performance, while different, non-circular shapes are used where there is a need to conform to a particular physical requirement.
Elliptical coils are easier to manoeuvre around bushes or between rocks, while still covering the same amount of ground as a circular coil of the same size.
Open web coils are lighter and reduce drag for aquatic hunters to pass through water.
COIL CONFIGURATION
The three most common types of coil configurations are Concentric, Double-D, and Monoloop.
Concentric coil
The concentric coils transmit winding is around the outside of the coil, the receive winding is in the centre, producing a cone shaped pattern. While this configuration does require more sweep overlap, it tends to be the most accurate when pinpointing targets.
Double-D coil
A double D coil has two overlapping wire windings in the shape of two D’s, this sends out a signal centralised to the coil in a blade or chisel type pattern. The Double-D configuration provides good stability, great depth, superior ground balancing and an expanded search pattern that requires less overlap. If you are hunting in areas with high EMI or salty environments like the beach, the Double-D coil may be the best choice.
Monoloop coil
The Monoloop coil features a single winding around the outside of the housing that both transmits (Tx) and receives (Rx) signals, producing a large cone shaped pattern and typically giving the best depth. Although the Monoloop coil can provide better depth than the Double-D, the monoloop can be more difficult to ground balance in heavily mineralised soils where the Double-D reigns supreme.
SMART COILS
Smart coils contain circuitry that interacts with the detectors control box, unlocking many advantages for the user. The early smart coils, such as the ones designed for the Minelab X-TERRA detectors, would change the Tx frequency of the detector, enhancing it for various detection scenarios like gold fields and beach detecting while still being an excellent treasure detector.
Today’s smart coils include features such as advanced signal boosting, which enables faster target response and increased depth. Along with digital processing, smart coils also improve immunity to electrical noise, sensitivity to smaller, deeper targets and normalised target ID’s across all coils available for a detector.
An additional coil can completely transform your detector and drastically increase your productivity. Whether you prioritise ground coverage, depth or sorting the trash from treasure, there is one to suit your detecting style. Happy hunting!
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