Cross-machine master charts
Coil Size vs Depth Chart: Coverage, Separation and the Trash Penalty
Quick answer
Coil diameter roughly sets detection depth on large targets and ground covered per sweep, while smaller coils separate adjacent targets and hear small gold better. A 6 inch coil suits dense trash, 9 to 11 inches is the all-round size, and 15 inches suits open fields and beaches.
Coil choice is the cheapest meaningful upgrade in the hobby and the one most often skipped. A second coil costs a fraction of a second machine and changes what the machine finds more than most settings do. The trade is simple to state and hard to accept: diameter buys depth on large targets and ground coverage, and it costs you the ability to tell two nearby targets apart.
That last point is the one that matters on real sites. Old parks, house sites and picnic grounds are full of iron and aluminium, and a large coil under those conditions sees a coin and a nail two inches apart as one confused signal. The coil size selector weighs trash density against coverage for a given site, and the Equinox coil compatibility chart covers which coils physically fit which machines.
Top pick
Minelab EQX 11 Coil (11 inch)
The 11 inch Double-D is the size that does everything acceptably, which is why it ships as the stock coil on the Equinox 700 and 900.
Price was accurate when this page was compiled and changes often.
On this page
What does coil diameter actually change?
Four things move together with diameter, and only one of them moves in the direction most buyers expect.
Moving from a 6 inch coil to a 15 inch coil roughly doubles the ground covered per sweep and adds depth on large targets, while making two targets a few inches apart read as one.
| Coil size | Depth on a coin | Ground per sweep | Separation in trash | Sensitivity to tiny targets |
|---|---|---|---|---|
| 5 to 6 inch round | Lowest | Lowest | Best available | Highest |
| 10 by 5 elliptical | Slightly below stock | Long footprint, narrow width | Very good | High |
| 8 to 9 inch round | Good | Moderate | Good | Good |
| 11 inch round | Good to very good | Good | Fair | Fair |
| 12 by 9 elliptical | Very good | Good | Fair | Fair |
| 15 inch round or 15 by 12 | Best on large targets | Best | Poor in dense trash | Lowest |
Depth on small targets does not follow diameter. A small coil concentrates its field, which is why the smallest gold often reads better on a 6 inch coil than on a 15.
Which real coils fit this pattern?
Published sizes and, where the maker prints them, published weights. Coil weight is not a detail: it sits at the far end of the shaft, so an extra half pound at the coil feels like far more than an extra half pound on the handle.
Minelab publishes 10.68 oz for the EQX 06 with its skidplate and 1.46 lb for the EQX 15, a difference of roughly a pound at the worst possible point on the shaft.
| Coil | Size | Published weight | Job it does |
|---|---|---|---|
| Minelab EQX 06 | 6 in round Double-D | 10.68 oz with skidplate | Dense iron, old house sites, tight spots |
| Minelab EQX 11 | 11 in round Double-D | Not published in the listing | General detecting, the stock coil |
| Minelab EQX 15 | 15 by 12 in Double-D | 1.46 lb with skidplate | Open fields and beaches |
| Coiltek 10 by 5 NOX | 10 by 5 in elliptical Double-D | Not published in the listing | Iron-infested ground with some coverage |
| Coiltek 15 inch NOX | 15 in round Double-D | Not published in the listing | Large open ground |
| Nokta LG15 | 6 in Double-D | Not published in the listing | Trash separation on The Legend |
| Nokta LG35 | 13.5 by 12.5 in Double-D | Not published in the listing | Covering ground fast on The Legend |
| Garrett 5 by 8 DD | 5 by 8 in Double-D | Not published in the listing | Working between nails on AT machines |
| NEL Hunter for AT Pro | 12.5 by 8.5 in Double-D | 17.2 oz with coil cover | Coverage upgrade for the AT Pro |
Weights are quoted only where the manufacturer listing publishes them. Rows marked not published are left blank rather than estimated.
Why is a bigger coil worse in trash?
Because the coil cannot report on targets individually, only on what lies under it. A 15 inch coil passing over a silver dime and a rusted nail three inches apart has both inside its field at the same moment, and it returns one blended signal that usually reads as iron. Narrow the coil to six inches and the two targets enter and leave the field separately, so you get two distinct responses and a chance to dig the right one.
This is why experienced detectorists take small coils to good sites and big coils to empty ones. A picnic ground that has been hunted for forty years is not short of depth, it is short of separation: the easy targets are gone and what remains is masked by trash. The Minelab EQX 06 Coil (6 inch) or the Coiltek 10 by 5 NOX Search Coil on that ground will out-find the Minelab EQX 15 Coil (15 inch) comfortably. Reverse it on a ploughed field and the big coil wins on coverage alone.
How much ground does each coil actually cover?
Coverage scales with effective sweep width, not with coil area, because you overlap each sweep. A 6 inch coil swung with sensible overlap covers roughly half the ground per hour of an 11 inch coil, and about a third of a 15. On a small permission that does not matter. On five acres it decides whether the site gets covered this season.
The honest way to plan it is to put numbers on it before you go. The coil coverage and sweep time calculator converts coil width, sweep speed and overlap into hours per acre, and the search grid planner turns a site into lanes so it gets covered once properly rather than three times badly. Both are more useful than another opinion about coil size.
Do coil covers matter?
Yes, and they are the cheapest insurance on the shaft. A coil cover costs a small fraction of a coil and is the only thing between the winding and a buried brick. The Minelab EQX 11 Coil Cover and the Minelab EQX 15 Coil Cover are the matched Minelab parts, and the Equinox Control Box Cover does the same job for the screen, which scratches long before anything else on the machine fails. Replace a cover when it wears through rather than when the coil starts falsing.
Sources
- Minelab EQX 06, EQX 11 and EQX 15 coil specifications
- Coiltek NOX coil product specifications
- NEL Hunter coil product specifications
- Minelab Equinox 700 and 900 instruction manual
Frequently asked questions
What size coil should I buy first?
A small one, because the stock coil on most machines is already the all-round size. The 11 inch that ships with an Equinox covers general detecting well, so the gap in your kit is separation rather than coverage. A 6 inch Double-D such as the EQX 06, or an elliptical such as the Coiltek 10 by 5, will find targets on hunted-out ground that the stock coil blends into the iron.
Will a 15 inch coil find deeper coins?
On large targets in clean open ground, yes, by a useful margin. On coin-sized targets the gain is smaller than most buyers expect, and on trashy ground the loss of separation usually costs you more finds than the depth gains. Buy the large coil for ploughed fields, pasture and dry beach, not as a general upgrade.
Does coil type matter as much as coil size?
It matters differently. Double-D coils give a blade-shaped detection field that handles mineralised ground and separates targets well, which is why nearly every current machine ships with one. Concentric coils give a cone-shaped field that some hunters prefer for pinpointing. Most modern coil choices in this catalog are Double-D, so size and shape are the decisions left to you.
Can I use any coil on any machine?
No. Coils are tuned to the machine electronics and use machine-specific connectors, so they are not interchangeable between brands and often not between models of one brand. Minelab publishes which of its coils fit which bodies, and the Equinox coil compatibility chart on this site sets that out. Fitting the wrong coil at best does nothing and at worst damages the machine.
Is an elliptical coil better than a round one?
For working between obstacles, usually yes. An elliptical such as the Coiltek 10 by 5 keeps a long footprint for coverage while staying narrow enough to slip between iron and along fence lines. Round coils give a more predictable detection field and are easier to pinpoint with. Many people end up with one of each and choose by site rather than by preference.
Researched, not professional advice. This page is compiled from published specifications, manuals and owner-review consensus, not hands-on testing. Target ID numbers, depth figures and settings vary with soil chemistry, moisture, target size, depth, orientation and firmware version, so treat every figure here as a starting point and verify it against your own machine's manual and your own ground. As an Amazon Associate we earn from qualifying purchases.