COIL SIZE VS. DEPTH QUESTION

[smithobx]

I WAS WOUNDERING IF THERE WAS A WAY TO ESTIMATE THE INCREASE IN DEPTH ONE WOULD GAIN FOR A GIVEN INCREASE IN COIL SIZE? For example, if you replace a 8.5 in. coil(56.7 sq. in. of area) with a 12.5 in. coil(122.6 sq. in. of area) you have doubled the size of the coil, but what percentage have you increased potential depth? My guess is 20 percent, if that much, or about 1.5 inches. Has anyone bench tested different size Garret coils on the same detector? Keep Swinging---John

 

[High Desert Jim]

A lot depends on your ground matrix. Heavy mineralization would hold you to 20% or maybe less. You may get close to 30 % if your mineralization is lighter.

There are a lot of variables, do you wear head phones, how skilled are you, will a slight variance in your threshold make you dig? If so, then your talking closer to 40 %.

There are other variables that that will make a difference, like sweep speed, and your persistence in trying to find those deep whispers that are the paydays for those of us who keep at it.

r/HDJ.................

 

[Bill G]

Go to Fisher metal detectors web sight @ www.fisherlab.com and read in PDF form Fisher Intelligence by Thomas J Dankowski. Read the part on coil size myths, it goes in depth about the subject and will probably answer your questions. Very good read and it applys to all detectors.

Take Care

Bill G

 

[Uncle Willy]

There are way to many variables to consider but a 12.5 over an 8.5 will generally get you 2-4 inches more in depth under ideal conditions. The size of a coil generally determines what it's depth would be under ideal conditions plus or minus a couple of inches. An air or bench test will give you a ballpark idea of what depth a coil will achieve under perfect conditions.

Bill

 

[smithobx]

Thanks guys for the information. I read the article you recomended and found it very informative, but I think, based on my experience, that the Garrett coil technology with the crossfire coils and double D far surpass other manufacturers in their ability to handle and discriminate multiple targets in the larger coil sizes. I base this on 18+ years of experience with my Garretts and my hunting partners Fishers and Whites. JUST MY OPINION-- thanks again --John