The searchcoil is the most vital part of a hobby detector’s/prospector's equipment.   It is the device attached to the control housing, which "connects" the metal detector to the ground beneath it. The searchcoil contains a transmitter and a receiver, which enables the detector to retrieve and interpret information about a detected target.

Searchcoils are available in several shapes and sizes, to meet a variety of ‘hunting’ needs.  Generally speaking, small searchcoils are designed to detect small shallow objects, while large searchcoils are used to find large, deeply buried objects.  An all-purpose detector is usually equipped with an eight or nine inch searchcoil, practical for scanning parks, playgrounds, beaches and other popular coin-hunting locations.

Changing the search coil on your metal detector is the next best thing to buying a whole new machine!  Most metal detectors come with a standard search coil that is good for general use – finding the broadest range of targets in the broadest range of environments.  But search coils come in all shapes and sizes, and it's possible that merely changing the coil on your detector will lead you to a host of new targets in that previously, “hunted out” area.

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 coils have inner circle and outer circle wire windings.  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 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 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 sometimes be more difficult to ground balance, however they tend to provide slightly better depth than the Double-D coils.

Typically, a larger coil will find targets hidden deeper in the ground, but they can be less sensitive to smaller targets.  A smaller coil is typically more sensitive to small targets, but does not go as deep as a larger coil.  A Monoloop coil will often have improved performance over a Double D coil, but can be more difficult to ground balance and therefore possibly more noisy.  The Double D coil is often more stable in heavily mineralized areas.

Larger coils require more open ground whereas smaller coils can be easier to guide in tight bush or rough terrain.  Obviously a smaller coil is also lighter weight than a larger coil.

In areas where discrimination is required, a Double D coil will provide a more accurate ID.  In high trash concentrations, a smaller coil is preferable.

There is really only one way to find larger gold nuggets and deeply buried treasures, and to do that you need to do one very important thing, you MUST use Larger Diameter Search Coils with your metal detector.  Search coils that come with your metal detector are fine for surface to average depth targets that are within reach of those coils, but it is no secret to metal detector users who have been using larger size search coils as they are the ones finding the deeper larger Gold nuggets and recover hidden treasures of gold and silver!