The search coil is one of the most important components of any metal detector — it’s the part that transmits and receives electromagnetic signals to locate buried targets. Choosing the right coil can dramatically improve your success, whether you’re hunting for coins, relics, jewelry, or gold nuggets.
Understanding coil size, shape, and configuration helps detectorists match their gear to the terrain and type of treasure they’re after. Below, we break down how each factor affects depth, sensitivity, stability, and overall performance.
Coil Sizes
Coil size has a direct effect on detection depth and target sensitivity.
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Larger coils (e.g., 13”–15”) penetrate deeper into the ground, making them ideal for finding large or deeply buried targets such as caches or relics. However, they are less sensitive to tiny targets and can be heavier and harder to maneuver in tight or trashy areas.
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Smaller coils (e.g., 5”–8”) provide exceptional sensitivity to small targets like fine jewelry or small nuggets. Their lighter weight makes them easier to swing for long sessions, and they excel in trash-filled sites where their smaller detection footprint helps isolate good targets among junk.
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Medium coils (around 9”–12”) offer a versatile balance of depth and sensitivity, suitable for general coin and relic hunting.
When selecting coil size, consider the type of detecting you’ll be doing most often — depth and ground coverage vs. precision and maneuverability.
Coil Shapes
The shape of a coil influences its stability, coverage area, and how it handles specific terrains. The three most common types are round, elliptical, and open-web designs.
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Round coils are traditional and known for their overall stability and performance. They provide even depth and sensitivity across the coil and are favored for gold prospecting due to their balanced electromagnetic field.
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Elliptical coils have an elongated design, making it easier to navigate around rocks, bushes, or stony terrain. They’re great for uneven ground or tight spaces where control and target separation are key.
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Open-web coils are designed with cutouts that reduce weight and drag. They’re especially effective when detecting in water or for long hunts where fatigue can be an issue.
Each shape has practical benefits depending on where and how you detect — round coils for power, elliptical for agility, and open-web for comfort and hydrodynamics.
Coil Configurations
The three most common types of coil windings are Concentric, Double-D (DD), and Monoloop. The difference between these coil types is the pattern the wire is wound within the coil.
The coil configuration refers to how the wire windings are arranged inside the coil, shaping its electromagnetic field. The three most common configurations are Concentric, Double-D (DD), and Monoloop.
Concentric Coil
Concentric coils use two circular windings — an inner transmit coil and an outer receive coil — creating a cone-shaped search pattern.
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Excellent for pinpointing targets with precision.
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Ideal for moderate ground conditions with low mineralization.
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Requires tighter sweep overlap for complete coverage.
However, they can become unstable or noisy in highly mineralized soil.
Double-D (DD) Coil
The Double-D coil features two overlapping D-shaped windings, offering a blade-like search field.
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Provides superior ground coverage and stability in mineralized or salty soils.
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Maintains good depth and sensitivity.
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On Minelab GPX detectors, DD coils allow Iron Reject to discriminate ferrous from non-ferrous metals.
They are also less affected by electrical interference and perform well on wet sand or noisy environments.
Monoloop Coil
Monoloop coils are designed for Pulse Induction (PI) detectors such as the Minelab SD, GP, and GPX series.
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The single winding acts as both transmitter and receiver, producing a deep, cone-shaped detection field.
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Offers superior depth over DD coils in many conditions, though it requires more precise ground balancing in highly mineralized soil.
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Ideal for gold prospecting in remote areas where depth is more critical than discrimination.
Choosing the Right Coil
Your ideal coil depends on your detector type, target size, and ground conditions.
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For coin and relic hunting, a medium Double-D coil provides a balance of depth and stability.
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For gold prospecting, round Monoloop coils often offer the deepest reach in mineralized soils.
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For beach and saltwater detecting, go with an open-web DD coil for stability and reduced drag.
Matching your coil to your environment maximizes performance and helps ensure that you never miss valuable finds buried beneath the surface.
Whether you’re coin shooting in a park, chasing relics in old battlefields, or prospecting for gold in mineralized ground, choosing the right coil can make all the difference. At Serious Detecting, you’ll find a wide selection of coils from leading manufacturers — including Minelab, Garrett, Nokta, XP, Coiltek, NEL, and Detech. Each brand offers unique coil sizes, shapes, and configurations engineered to match different detectors and hunting styles. Explore our collection to find the best coil for your specific detector and detecting conditions, and get ready to uncover more depth, precision, and performance on every hunt.