The shape of the search coil you use on any of your metal detectors will change the capabilities of your machine and, as a result, having several different types on hand will really enhance your treasure hunting experience. In fact, many metal detectorists feel that you can transform your metal detector into an entirely new machine simply by selecting different size and shape search coils as opposed to actually buying a whole new machine! There are two parts of a search coil to talk about when discussing their shapes. First is the shape of the search coil itself. The search coil itself will be either round or elliptical – most will be round. More important than this though is the internal construction. The way the wires are attached to the coil internally will take one of the three following forms – Concentric, Double D, or Coaxial – each giving your metal detector different capabilities. Let’s discuss each of these search coil designs, their benefits, drawbacks, and more.
Concentric circle search coils are probably the most popular design of search coil for metal detectors today. Most commonly used for finding smaller targets like gold, jewelry, coins, and relics that are generally found near the surface concentric coils are also excellent at target discrimination and pinpointing. They’re drawback? Concentric coils are easily compromised in heavily mineralized soils.
A Double D search coil is designed in the shape of two capitol letter “Ds” hence it’s name! Double D metal detecting search coils are reliable in heavily mineralized soils, like what you run into at the beach for example, and cover more ground in one sweep than other types of coils. They’re not as good at pinpointing nor as adept at target discrimination; although many of the newer DD coils being made today are.
Coaxial coils are probably the least popular search coil design type and are rarely found on metal detectors made today. While it’s detection depth is usually lower, the coaxial search coils are the best type of coil to use when you need to minimize interference from utility wires or other metal detectors. Coaxical coils are also great at pinpointing and discrimination even in areas with very heavy trash.
All shapes are generally available in all sizes (extra small/mini, small, medium, and large) and vice versa. Whatever size and shape search coil you buy for your metal detector though, be sure you’re purchasing quality search coils that are compatible with your metal detector in order to avoid violating any warranties or, worse, causing your machine to malfunction. You’ll also need to consider the type of metal detector you’re using, the frequency it operates on, and, as we mentioned, where you’re working, and what you’re hunting for. From there though you’ll easily be able to buy all the right shapes and sizes of search coils to find treasure wherever you’re metal detecting.