Maybe something to think about. Bearing in mind I am probably going to get these new coils for the 23 and 7 myself, people should at least consider, a lot of people are saying something along the lines of "my detector is out of warranty anyway, so I`m not risking anything fitting these new coils", but, it is Minelabs policy to not repair any modified Minelab detector. I daresay that if you were to send a out of warrenty 2300 or 7000 back to Minelab for repair and Minelab saw you were running a unsanctioned coil, they wont repair the detector. You could end up with a 4K or 10K detector that all it`s good for is to fill it with concrete and use it as a anchor.
Like I said, I am probably going to get the coils myself, but I will be doing it with the idea that if either detector fails I will probably have to throw it away, and that`s on me and no one else.
I have no reason to suspect the coils are going to cause any damage and I wish Coiltek and davsgold nothing but success with these new coils.
By Steve Herschbach
This is not about detector versus detector. It is just a video questioning if small coils are always better in trash, and whether concentrics are always better than DD coils at handling ferrous targets. Too bad about the wind noise. Good stuff though illustrating there are no magic answers.
For detailed information see this article VLF Concentric Vs DD Coils
By Steve Herschbach
VLF detectors can come with DD or concentric coils. This is similar to but not quite the same thing as DD versus mono on a pulse induction detector. There are three basic coil types in wide use, Concentric, Double D (DD) and Mono. A VLY detector transmits and receives simultaneously and so there must be both a transmit coil and a receive coil. A pulse induction (PI) detector can alternate between transmit and receive and so one coil can be employed as both transmit and receive in an alternating fashion. There is confusion on this but simply put VLF (induction balance or continuous wave) detectors do not employ mono coils. A VLF can only employ the concentric or DD options. A pulse induction coil can work with all three types.
Metal detector coil types illustrated - concentric vs DD vs mono
VLF 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 concentric, 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.
About Search Coils by Dave Johnson
Search Coil Field Shape by Dave Johnson
Coil Basics by Carl Moreland
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. The DD is the better prospecting coil for bad ground. Concentrics do well on milder ground.
A note on coils. The blade like knife edged detecting pattern depicted in DD marketing ads is largely myth. Electromagnetic fields radiate and simple coils cannot focus them into beams. A round concentric coil has a search field shaped like a soccer ball cut in half. A similar size DD coil will have a search field more like a football cut in half lengthwise. If you ever doubt this, just fire up your detector with a DD coil, flip it over, and run a coin under the coil noting where the signal fades at different locations under the coil.
Finally, depth is more related to coil width than coil length. Think of a 5" x 10" coil as a stretched out 5" coil, not as a skinny 10" coil. That is why when listing elliptical coil sizes you will often see me putting the small number first. Marketers do it the other way around so you tend to think you are getting more than you are.
Fisher F75 with 10" Elliptical DD Coil
Fisher F75 with 10" Elliptical Concentric Coil
Dilek has mentioned this on some of the forums that a new coil offering for Impact much like what is given on Anfibio package. Looks like the coil is indeed loaded to Nokta’s site now.
There are a couple lots on Ebay where the seller includes a Tesoro Widescan (DD) 5 3/4 inch coil with plug modified/replaced to operate on a Fisher Gold Bug (the new generation Gold Bug, not the 1990's versions). I'm wondering if anyone here has heard about the possibility of going the other direction -- putting a Fisher Gold Bug / F19 / Tek G2,G2+, Tek Greek series coil on a Tesoro?
Nugget Finder is coming out with some new DD coils for 2019
I look forward to hearing about them once released.
COMING IN 2019 - DDXSEARCH
A new Range of DD Coils for 2019
Sizes will Include 15" Round, 19" Round & 25" Round
-Spiral Winding - Lightweight - Excellent Signal Response
-Quiet Operation in Highly Mineralised Ground
- Fantastic Ground Coverage at Maximum Depth