The importance of a bigger coil size?

[Skoivu]

Im getting a Garrett 250 for Xmas. It comes with a 6.5 x 9 coil, but I was thinking of getting the 9 x 12 coil along with it for the additional 80 bucks, as someone who hasnt metal detected before can you tell me if its worth it? Or maybe invest the extra money in a pinpointer. thanks.

 

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[Hosensack]

Of the two options, I would suggest pinpointer and if you don't have one a nice digging tool like a "lesche". The larger coil will give you a little more depth and cover more ground quicker, but if you are not recovering them properly it won't be worth the investment.

Learn the machine and proper recovery first, then switch up the coils a little...my guess is you'll probably go smaller first(sniper) once you get the hang of it.

If you don't have a dealer you are dealing with currently I can help you out on either option or give me a call if you need a more conversational explanation of the above.

Tom (Miller MDz)

 

[jmoller99]

For me, I use a bigger coil for relic hunting only. I use small coils or the stock coil for most things (small coils work better in trashy areas and can find smaller things that larger coils will miss entirely).

Create a detector garden in your yard and practice locating things with your new detector. It takes a lot of time to get to understand what your detector is telling you. For example, if you want gold rings you have to dig aluminum pull tabs - so bury a few at different depths in your detector garden so you know how your detector reacts.

 

[Michigan Badger]

Just about every THer has a slightly different opinion about coil size.

Here's mine.

The stock coil is the best size for the intended purpose of the detector. Most machines are made for general coin shooting and the stock coil is a compromise for most coins. The majority of coin finds are the memorials/wheats, nickels and dimes. The stock coil is the best size for these smaller sized coins (best depth + target separation for the most popular targets in the U.S.A. = the stock coil). In fact, if you contact any company (that bothers to respond to the public) you'll get this same thing from them (because that's where I got it).

Now, what about smaller or bigger coils?

Smaller coils are for greater target separation and smaller targets than the average. These always get less depth than the stock coil when it comes to the average coin finds.

Bigger coils are for greater depth on targets larger than the average stock coil finds.

As a rule, you can figure about 1 inch of depth to each inch of coil diameter (round coils, the others are more tricky to figure). However, this is not for all sized targets. The stock coil will go deeper on a target in it's range than will a larger coil built to function at maximum on targets larger than the stock coil's range.

Coils are antennas and the antenna must be factory tuned to the target. Larger coils are less sensitive than stock coils are when it comes to targets within the stock coil's range. However, targets larger than the stock coil's maximum depth range will be detected deeper with the larger coil. The antenna's (the coil's) physical size almost always means greater depth (not always) IF THE COIL WAS DESIGNED FOR THAT TARGET SIZE AND ALLOY.

And then if this weren't confusing enough you have the difference between the so-called "wide scan" coils and "concentric." The deepest coils are the "concentric." The widest area coverage coils are the "wide scan" (thus the name).

A round 10 inch "concentric" coil will usually detect a silver quarter at 10 inches deep (it depends on the quality of the detector's electronics). This same coil may detect a clad quarter at 12 inches. The type of metal is also important. But in some soils this same coil may not detect a clad quarter 4 inches deep (this is another factor).

Confused?

I've seen it where a 6 inch coil got better depth than a 10 inch coil on any size target due to iron masking (another factor). In some soils a big coil is nearly worthless due to taking in too much ground area at a time.

 

[U.K. Brian]

Coils are never tuned to a target as the different types, sizes and varying metal contents would make that impossible. What is needed is to be able to tune a coil to the detector which is an automatic process if a detector has a true ground balance control rather than "auto" ground balance which is in fact fixed. No ground balance ? Then for best results you have to open up the detector and adjust a trimmer.

Concentrics, which I tend to prefer, are not automatically deeper than DD types because the whole area of the coil can be considered as live and picking up the ground mineralisation whilst the double D types narrow central band means its much less affected so on bad ground may well outperform a concentric.

Problem is the ground balance on a detector doesn't balance out the mineralisation and nullify its effects which is what most people think. The negative/bad effect of the soil remains ....all thats happened is that a more positive reference point has been set which reduces the audio from the minerals but they haven't disappeared.

I would as suggested get some time in with the stock coil. You can then consider another size (or type) and many find that for their sites/conditions its better to drop a size than go bigger.

 

[Bart@Big Boys Hobbies]

Great replies here! Good thread!

 

[Skoivu]

Yes, very good replies. Although some of it has gone over my head its still given me some good advice that Ill think about.