I believe you are referring to these coils being used on the MX-5, correct? Going back to when the original MXT was first released, I got mine with the 'Shooter' DD coil
[size=large]'thinking'[/size] it might provide me some benefit in the trashy sites I hunt that have a lot of metal structures and pipes associated with the building rubble, not to mention the urban Coin Hunting that also deals with pipes and the like such as in playgrounds, working around older irrigation piping, and hunting close to chain link and other metal fences.
I already had White's 6½" Concentric coils on other models, such as the Blue Max 600's on an XLT and 6000 Pro XL, a 5.3 Black Max on a modified IDX Pro and Blue Max 350 'Snooper' on a Classic ID, so it would maybe give me some benefit in performance. At the time back then I was able to get out hunting very often, daily putting in 2 to 6 hours of hunting and more on my days off. I compared the 3-filter MXT w/Shooter to all the other models, both 4-filter and 2-filter detector performance and the various Concentric coils to the elliptical DD coil.
The 'Shooter' coil was short-lived and I parted with it less than a month's time. Once I mounted a 6½" Concentric on my MXT I was mode than pleased, and the same held true with all of the MXT 'family' that share the same search coils, to include the M6, MXT Pro and MX-5.
slingshot said:
[size=medium]Does anyone know which coil can get closer to metallic barriers like poles, benches without overloading.[/size]
I prefer the 6½" Concentric to the elliptical 4X6 DD, and remember that with either search coil, working close to metal structures really calls for doing two things:
1.. Work a search coil WITH the metal object to maintain a consistent coil-to-object relationship. Do NOT sweep a coil towards and away from an offending metal object or you're more likely to get overloading and/or impede recovery time for nearby desired small targets. For example, if there is a metal sprinkler line running along several inches under ground, position the search coil as close as possible to the metal pipe, reducing the Sensitivity a little if needed. Then, maintain a uniform coil-to-object relationship and work the coil along the route of the metal object and listen for a response from any nearby potentially good target. Do NOT sweep across the sprinkler line or towards-and-away from the like.
Once a desired distance has been searched with the coil maintaining the same relationship to the offending metal object, back the coil away from 1" to 2" and repeat. Keep the 1" to 2" coil-to-object distance and move the search coil evenly along the route of the metal object. Again, when the desired length of search has been covered, move the coil away another 1" to 2" and search the area a little farther away from the metal object that can mask a desired nearby target. Do this until you have efficiently covered the ground for a distance up to 8"-12" away from the sprinkler line.
You can use this same search technique to work all of the ground close to a metal fence by keeping the coil as close as possible to the fence then slowly and methodically working the search coil along the length of the fence line maintaining a uniform coil to metal object distance. Then move the coil away 1"-2" and repeat the process of covering the ground along a fence row, working 'strips' of ground along the route of the fence until you are 12" or so away from the offending metal.
If you are dealing with things like round poles in a playground, old clothesline piles and similar encounters, do the same thing by getting the coil as close as possible to the metal pole, then moving the coil around the pole. This is best accomplished by the operator slowly side-stepping their way around the pole and maintaining a very consistent coil-to-pole relationship. It is also much easier to do with the more uniform EMF of as Concentric coil than it is with a Double D designed coil.
Then, after the first trip around the pole, move the search coil back an inch or so and repeat the search process.
2.. Remember to use the smallest coil available, and reduce the Sensitivity/Gain when very close to the metal object, but increase it when possible as the coil is worked farther away from the metal.
slingshot said:
[size=medium]Seems like the shooter coil would if you approach from the sides. But, I don't want a shooter coil if the round eclipse coil will match performance.[/size]
Keep in mind that the 'Shooter' coil is a Double-D design and that can work against you to some degree. A Concentric coil has a very uniform EMF about the coil and is consistent from any direction outward from the coil. The Double-D design complicates things because from one side of the coil you have the primary Transmit winding, and from the other side of the coil you have the Receive winding. The main "working part" of the DD coil is the overlapped area running fore-and-aft down the center area of the coil. A Concentric coil has a much more uniform field and that is why they can provide tighter, more consistent numeric VDI's from a left-to-right and then right-to-left sweep. The DD coil design doesn't work that way and approaches from opposite directions can have differing results.
That's why Concentric coils are noted as being more consistent and having tighter VDI read-outs compared to Double-D type coils. Additionally, DD's are also known to have more difficulty dealing with/rejecting ferrous objects when compared with a Concentric coil design. So my strong suggestion is to go for the 5.3 Eclipse and enjoy better all-purpose performance, and for those concerned with depth-of-detection, a Concentric will usually get slightly better depth than a comparably-sized Double-D coil.
Monte
