A Basic Guide To Metal Detector Coils
iDetectorist sends out HUGE thanks to Sam Luedke and Tony Pasquale from Kellyco Detectors. Tony has over ten years experience in the industry and has written books on metal detecting such as: “A Beginners guide to the Minelab Sovereign and Excalibur Series”. Read more about Tony at his Kellyco page.
Tony stepped up to answer some questions related to metal detector coils.
iD: A basic question to start things. What exactly does the coil (or “loop”) of a metal detector do?
Tony: The search coil transmits the signal and receives back information to communicates to the control box.
iD: There are a lot of different kinds and varieties of coils available, such as Double D, Concentric, Eliptical, and Widescan. Can you tell us about these varieties.
Tony: The concentric type coils are the standard coil design that that searches very deep in the very center of the coil diameter, however will not search the whole diameter of the coil at full depth.
The Double D (DD) type coil searches almost the whole diameter at full depth and is also excellent at canceling out ground mineralization. The elliptical style coils can come in either the DD or the concentric style, however they are oval in shape instead of round. This allows the user to search closer against things such as trees and fences etc.
iD: The age old question – does size matter? Why would someone choose to use a small coil rather than a larger one or a larger one rather than a small one? Are there situations where a particular size would be better?
Tony: Yes, size does matter a great deal. If you are searching a more open ground such as a field or beach, then you can achieve better depth and ground coverage with a larger search coil. A smaller search coil is beneficial for searching areas that are very congested with items in the ground and are more precise and also smaller coil are more sensitive toward smaller items.
iD: Any advice that you would give a coin shooter for coil selection?
Tony: Most coin shooters prefer a smaller coil because they are more precise.
iD: What about a relic hunter?
Tony: Most relic hunter prefer a larger search coil because they hunt in more remote ground and getting the extra depth is a help because civil war relics are very deep because they are hundreds of years old.
iD: A beach comber?
Tony: Beach hunters also mostly prefer larger coils to achieve a greater depth and ground coverage.
iD: Someone looking for gold nuggets?
Tony: Typically gold prospectors prefer an smaller elliptical style search coil because they are very precise and extremely sensitive.
iD: Thanks again! If someone is interested in getting an accessory coil for their metal detector, why should they contact Kellyco?
Tony: Because we are absolutely the largest and the most experienced metal detector dealer in the World!
For more information be sure to visit Kellyco Detectors and be sure to tell them iDetectoris sent ya!
That was a great aticle.
Glad you liked it! Hopefully I’ll have more interviews and articles of interest in the near future!
And again, thanks to Tony @ Kellyco!
I used to own a “King Cobra” metal detector that I just loved. I had three coils for it; a 2″ coil, a 9″ coil, and a whopping 18″ coil I believe. The 2″ coil actually let me get right up on park equipment poles without “singing.” Found a lot of coins and rings that way. I used the large one for fields and such without a lot of obstacles. Nowadays I use a White’s DFX with the “Big Foot” search coil. That coil lets me cover a lot of ground quickly, and I have yet to miss a target according to friends who have followed behind me with “regular” coils.
HIGH MR. CRIST THE CHIPMONK IS HEAR, I’M A 69 YEAR OLD NAM-VET AND 35 YEAR TH’ER. 4 YEARS I’VE BEEN LOOKING FOR OTHER USERS OF A KING COBRA METAL DETECTOR ( BY GOLD MOUNTAIN TECHNOLOGIES IN DESOTO, TEXAS 75115 )LIKE MYSELF WHO MAY ANSWER A QUESTION FOR ME! MY 8 INCH 15 KHZ CONCENTRIC COIL TOP AND BOTTOM HAS SEPERATED ( EXPIRED GLUE I GUESS? )I’VE TRIED DIFFERENT TYPES OF INDUSTRIAL WATERPROOF GLUES WITHOUT SUCESS AND WANTED TO RE-WATERPROOF AND SEAL IT AGAIN FOR A NAM-VET WHO LIKE TO TH. ANY RECOMMENDATIONS? ALSO DO U STILL HAVE ANY OF YOUR OLD COILS 4 SALE? THANK YOU MR. CRIST GOOD HUNTING AND HAVE A BLESSED EVERY DAY
Okay, That is a informative interview. Now if I only knew if a coil like the whites super 12″ Concentric Coil reaches deeper than let’s say the Jimmy Sierra 12″ Concentric Coil. I quess what I am wanting to know is which design works best? The pancake style or the double ring type coil?
Steven – Now, I’ve swung a 5” coil around before, and a 12” coil. But a 2” coil and an 18” coil? Quite an extreme. I bet the 2” felt like no coil at all, and the 18” felt like swinging a hoola hoop.
Daves – I gotta admit I don’t know much about White’s products. I did a quick search about the Jimmy Sierra products. The dual field coils look pretty impressive. For those that aren’t familiar with them, check here: http://www.jimmysierra.com/loopsZ.htm.
Maybe someone else will jump in with some info?
I really wasn’t trying to compare manufactures of coils as much as I am trying to figure out the design of a coil and with that which of the designs actually work best for deep coins. Is a double ring coil better at sending and recieving information as compared to a conventional coil? I only mentioned the two manufactures as a illustration or figure. ie: fiq 1 and fiq 2 for this question, since both are a 12 inch coils.
I know the White’s Super 12 is a basic “spider” designed concentric coil. The design of the Jimmy Sierra coil is new to me. I’m not sure if it’s a standard DD coil or some kind of variation of a DD.
If by double ring you mean Double D (DD), then there are situations when it would be better than a same-sized conventional (concentric) coil. Generally DD coils better handle tougher ground conditions, or more highly mineralized ground. These conditions might include red clay like in the southern US as well as volcanic dirt in the north west, sandy conditions in the south west where you might find gold, and “black sand” beaches.
“Generally” speaking, in more neutral ground a concentric coil will get better depth, but as the ground conditions get worse the DD coil will start performing better.
Do keep in mind though that as you get a larger coil your sensitivity for smaller items like coins will decrease at depth. The really big coils will go deeper, but with less sensitivity for smaller targets. That’s why the little coils are more sensitive for small targets. But it’s give-and-take because they don’t go as deep.
I might see if Tony can peek in and respond for clarity!
Hope this helps. If not, I’ll keep trying!
Hi Wayne, You have done a fine job of answering the question regarding DD vs concentric coil design. I dont know if I can add much. The DD coil as you stated has the advantage of a larger window so it covers more ground. However, it sacrifices some depth when compared to a mono coil when used in easy soil. Mono coils do go deeper, but not in higher mineralised soil. just as you pointed out. As for the 12 whites mono vs the hotshot that we made, the edge on sensitivity is with the hotshot also the weight. However, we no longer are able to make them as our engineer mfg. died 2 years ago. If you have one you are lucky. they can be repaired if need be, but not made any longer. good luck Jimmy
Jimmy, thanks for dropping by and sharing your expertise!