Metal Detector Coil Types

Unraveling the Secrets of Coil Types to Unlock the Full Potential of Your Metal Detecting Adventures
Written By: Marc McDermott
Last Updated:

Understanding the different metal detector coil types and configuration is essential for both beginners and experienced hobbyists looking to maximize their finds. While many people may be familiar with the basic operation of a metal detector, not everyone realizes the crucial role that the detector’s coil plays in successful treasure hunting. The coil is responsible for transmitting and receiving signals, and its type can significantly affect the detector’s performance, sensitivity, and ability to discriminate between various targets. 

In this article, we will explore the importance of coil types in metal detecting and provide a comprehensive guide to the most common and specialized metal detector coils available. We will discuss the basic principles of how coils work, delve into the advantages and disadvantages of each type, and offer insights into selecting the right coil for your specific detecting needs and goals.

By the end of this article, you will have a better understanding of the diverse range of coils available, and how to choose the best one to enhance your metal detecting experience.

Concentric coils

Concentric coils are the most common type of coil found on beginner and intermediate metal detectors. This coil type is designed with two or more circular wire windings, with one coil nested inside the other. The inner coil serves as the transmitter, while the outer coil acts as the receiver. The transmitter generates an electromagnetic field, which is affected by the presence of metal objects. When the field is disrupted, the receiver coil detects the change, and the metal detector alerts the user to the presence of a metallic object.

Better Target discrimination

Concentric coils are known for their excellent target discrimination capabilities. They can differentiate between different types of metals, allowing the user to focus on specific targets such as coins, jewelry, or relics. This can help to reduce the time spent digging up unwanted items like trash or iron nails.

Better sensitivity in less mineralized soil

In areas with low mineralization, concentric coils offer increased sensitivity, particularly to smaller targets. They are well-suited for detecting small coins, jewelry, or other valuable items in parks, playgrounds, or sandy beaches where the soil is less mineralized.

Limited depth in highly mineralized soil

One of the main drawbacks of concentric coils is their limited depth detection in areas with high soil mineralization, such as goldfields or salt water beaches. The interference caused by the mineral content in the soil can reduce the coil’s sensitivity, making it difficult to detect objects at greater depths.

Uneven detection field

Concentric coils generate an electromagnetic field that is strongest at the center and weaker towards the edges. Think of it like an upside down cone. This results in an uneven detection field, which can cause the metal detector to give inconsistent signals when scanning over an object. This may lead to missed targets or false readings, requiring the user to pay closer attention to their scanning technique.

Double D coils

Double D coils, often referred to as DD coils, are designed with two overlapping D-shaped wire windings, giving them the appearance of a capital “D” placed back-to-back. These coils have separate transmitting and receiving windings, with the transmitter typically being the outer D-shaped loop and the receiver being the inner loop. Double D coils generate a more focused and uniform electromagnetic field compared to concentric coils, allowing for better performance in certain conditions.

Better performance in mineralized soil

Double D coils are known for their ability to perform well in mineralized soil conditions. Their focused electromagnetic field allows them to maintain stability and sensitivity even in areas with high mineral content. This makes them an excellent choice for gold prospecting, salt water beach hunting, or searching in environments where soil mineralization poses a challenge.

Better Target Separation

Double D coils also excel in target separation, which refers to their ability to distinguish between multiple targets that are in close proximity to each other. Due to the focused and uniform electromagnetic field generated by the overlapping D-shaped windings, DD coils can more accurately pinpoint the location and depth of individual targets.

This makes them particularly useful when detecting in areas with a high concentration of metal objects, such as trash-littered sites or historical locations with numerous relics. The enhanced target separation offered by Double D coils allows hobbyists to efficiently recover valuable finds from cluttered environments, where concentric or mono coils may struggle to differentiate between closely spaced items.

Lower sensitivity to small objects

Compared to concentric coils, double D coils may have reduced sensitivity to small targets, particularly at greater depths. This can make it more difficult to detect tiny coins, jewelry, or other small valuables when compared to the performance of concentric coils. However, the enhanced performance in mineralized soils may outweigh this disadvantage for many users, depending on their specific detecting goals and environment.

Read our full article about DD vs concentric coils.

Mono coils

Mono coils, also known as single-loop coils, feature a single wire winding that serves as both the transmitter and receiver. These coils are found in pulse induction (PI) metal detectors, where they generate a single, continuous pulse of electromagnetic energy to detect metal objects. Mono coils are typically circular in shape, although some variations exist.

One of the main advantages of mono coils is their ability to detect targets at greater depths compared to concentric and Double D coils. This is particularly useful for detecting larger objects or when searching in areas where targets are expected to be located deep underground.

Mono coils are generally less effective in mineralized soil compared to Double D coils. The single-loop design can be more susceptible to interference from minerals in the soil, which can result in reduced sensitivity and increased false signals. As a result, mono coils may not be the best choice for detecting in areas with high mineral content, such as goldfields or relic sites.

However, it is important to note that pulse induction metal detectors equipped with mono coils can still provide excellent performance in mineralized soils, as the PI technology is inherently better at handling mineralization.

Factors to Consider Based on Goals

Different coil types are best for different types of hunting and different environments.

Coins & Jewelry

When searching for coins and jewelry, it is important to consider a coil that offers good target discrimination. Concentric coils are generally suitable for this purpose, as they perform well in less mineralized environments, like parks or yards, where coins and jewelry are often found.


Relic hunting often involves searching in areas with high mineral content and requires coils capable of detecting targets at greater depths. Double D coils are an excellent choice for relic hunting, as they provide better performance in mineralized soil and have enhanced ground coverage, allowing you to cover more area with each sweep.

Gold prospecting

Gold prospecting often takes place in highly mineralized environments, such as goldfields. In these conditions, a Double D coil or a pulse induction coil, like a mono coil, would be more suitable due to their ability to handle mineralization and offer greater depth detection.

Soil conditions

The level of mineralization in the soil affects the performance of metal detector coils. Double D coils and pulse induction coils, like mono coils, are better suited for highly mineralized soil, whereas concentric coils are more appropriate for less mineralized environments.

Ground coverage

If you plan to search in large open areas, a coil with enhanced ground coverage, such as a Double D coil, is beneficial for scanning more ground in less time. 

Detector compatibility

When choosing a coil, it is essential to ensure that it is compatible with your specific metal detector model. Not all coils are designed to work with every detector, so check the manufacturer’s guidelines or consult with experienced users or retailers to verify compatibility.

Budget constraints

Lastly, consider your budget when selecting a metal detector coil. Coils can vary widely in price, depending on factors such as brand, type, and size. It is essential to find a balance between your desired features and your budget, ensuring that you choose a coil that meets your needs without breaking the bank.

Additionally, you may want to consider investing in multiple coils to enhance the versatility of your metal detector and adapt to different detecting conditions and goals.

Final thoughts

In summary, choosing the right metal detector coil is crucial for optimizing your detecting experience. Concentric coils are best suited for detecting coins and jewelry in less mineralized environments, while Double D coils excel in mineralized soil and provide enhanced ground coverage, making them ideal for relic hunting and gold prospecting. 

Understanding the importance of selecting the right coil for your specific detecting goals and environment is key to successful metal detecting. By considering factors such as your target items, soil conditions, detector compatibility, and budget constraints, you can make an informed decision and ensure that you have the right coil for your needs.

Finally, we encourage metal detecting hobbyists to experiment with different coils to discover which type works best for their specific detecting goals and preferences. By trying various coil types and sizes, you can fine-tune your detecting setup and maximize your chances of uncovering valuable treasures. Happy hunting!