Different coil types? What are the advantages/disadvantages?

[ryan_p]

I'm just starting to learn that there are many different shapes and types of coils.

What are the advantages/disadvantages to these?
Concentric vs DD?
Elliptical vs round?
Solid vs Open?


Thanks

Ryan

 

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[Loco-Digger]

I am a fan of the DD over the concentric, see the pics below.



As you can see the concentric coil will take more overlapping of swings to get max depth over an area.

Coil size is much more important of a factor.

Large coils for target sparse areas The larger the coil the more depth can be expected in most areas
Small sniper coils for trashy areas Due to their size they get better target separation than larger coils.

Solid vs open. Open can get hung-up is some sites, but may also get you into places where a solid coil is too big.

Elliptical vs round. Elliptical are narrower and may be narrow enough to get into a tight spot where as a round coil my be too big.

I have 4 coils for my F75LTD

12" x 15" nel butterfly coil for target sparse areas which allows me to cover more ground quicker than using a smaller coil
Stock DD I still use it, just not as often as I once did.
Nel sharpshooter. My main choice for most sites since it is smaller then the stock coil and get better target separation without much loss of depth.
5" DD sniper coil. This coil gets amazing depth for it's size and is the best for trashy areas.

 

[Happy_Hour]

Monoloop & Coaxial Search Coils

 

[sprailroad]

No need for me to add, Loco-Digger pretty much covered it.

 

[Terry Soloman]

You find elliptical coils on gold prospecting machines, because the are easy to maneuver around rocks, cactus, and brush. They are almost always "DD" or "Widescan" design.

"DD" coils are much better in high-mineral soils, red clay, and sands, however, they are not as deep as concentric coils in Moderate-to-Light Mineral soils and sands.

While many say larger coils help them cover more area faster, I have a much different outlook. While small "Joey" coils can be swung rapidly - like a jet fighter - in high garbage areas while still giving fantastic separation and depth (7"), large 11" - 15" coils are used for depth, and are like flying a huge Galaxy C-5-A. A big coil has a much slower swing speed when swinging for deep targets at low to moderate kHz-freq's. Sure, you can swing one like a fighter jet, but you will not get the same performance.

The secret is knowing which tools you need for the type of detecting you do. Since there (right now) are no real "all around" metal detectors, you need several if you do saltwater beaches, woods and farm fields, parks and permission's.

 

[Charlie P. (NY)]

You got some great answers.

Solid vs. Open is mostly cosmetic (internal wiring is identical) but there are times a solid is easier to get down & close. Like in brush-hogged goldenrod. A skeletal coil hangs up in the stubble.

Concentric vs. DD can be a personal preference. I started serious detecting with a DD and prefer it - because I know how to use it and hunt trashy sites where (I feel) it has an advantage. Likely a Concentric fan is just as favored of their choice for their own reasons.

 

[ryan_p]

Thanks everyone! This helped a lot