Fisher F75 10" DD and 10" Concentric

[steve herschbach]

Detectors are more alike than different these days. One thing that can make a real difference is what coil the detector comes with. Two very similar models will be quite different if one comes with a 12" round mono, and another an 11" x 7" DD.

In this case the very same detector can be turned into two different detectors by changing coils. Here are a couple rarely seen on the F75 - the 10" x 5" DD and 10" elliptical concentric. A big difference between the Teknetics T2 and Fisher F75 was that the F75 came later and the ability to use concentric coils was added. The T2 can only use DD coils

Why DD or concentric? DD coils are all the rage these days. However, concentrics have more consistent detection patterns with less dead spots up close. Every notice how that DD coil goes wacky on shallow targets? And concentric coils are much better at identifying flat ferrous targets like bottle caps. Here it is from the guy that should know best, Dave Johnson, lead designer on the F75.

I like the 10" DD for the solid design, better for working in stubble or other locations where an open coil might hang up. The concentric just for being better behaved.

About Search Coils http://www.fisherlab.com/hobby/davejohnson/searchcoilsessayrevised.htm

Search Coil Field Shape http://www.fisherlab.com/hobby/davejohnson/SearchcoilfieldshapeApril2012.pdf

 

[Charlie P. (NY)]

There's all kinds of good reading at that Fisher essay library.

Happily we can have both! I like the DD for trashy sites - I find them easier to pinpoint with but that's what I started with (a DD and no display - audio only). It does "upgrade" iron into non-ferric regions on the display on occasion.

The Concentric is a little easier to fool with multiple targets, but the 6.5" elliptical that Fisher sells is my favorite coin hunting head,

 

[Clad2Hunt]

I use the 10" concentric with a jewelry pattern and it works great on small targets. I like it in the milder park soils and it hits hard when using je, 1F tones and push the discrimination up to 20. It causes the small foil to have a rough tone and any good target is clean and strong.

 

[steve herschbach]

I love that little concentric! I was just using it today's as a matter of fact. More like running a pinpointer than a coil. I even like the way it overloads on shallow targets. Just a great little coil, real fun to run. Works great in the new 2L mode.

I am a coil junkie. I have every Fisher coil for the F75 now plus a couple aftermarket larger coils. The 13" Ultimate and 15" x 12" DeTech.

 

[Coin Rescue Inc]

Last week I acquired a 10x5 coil.
From air tests It seems accurate up to 10".
Before the upgrade I used the 5" coil 99% of the time.
I am looking forward to using the 10x5. Anyone have experience with this one?

 

[steve herschbach]

That is the one I posted the photo of on my F75. I have a few hours on it now, really like it. Basically just a stretched out 5" coil, a smidgen more depth.

 

[GroundScanner]

I have been wanting a 10" DD coil from fisher for my F75se . I checked with a few dealers and they didn't have one . Does anyone know where I can get one ? Thanks , GS

 

[steve herschbach]

Almost nobody stocks them except for forum sponsor Big Boys Hobbies at http://www.bigboyshobbies.net/fisher-f75-5x10-elliptical-coil

 

[GroundScanner]

Thanks Steve. GS

 

[Fletch88]

I like concentrics better most of the time in the mild soils i hunt in. I especially love the stock concentic coil on the Omega! Haven't tried an 11" biaxial on it yet, but did try the 5" DD. it seemed very squirrely compared to the concentric.