Coil detection depths

[TrpnBils]

Couple things... my main focus, as some of you have seen lately, is dealing with iron infested sites because they seem to be common around here. I probably haven't had my stock coil on in two weeks because I've been using the 6" in sites like that. It seems to me that any target I dig out of my iron sites is at about 5" or less in depth. In one site that includes coins as old as the 1790s, so I have to figure there are coins still deeper than that but masked by the nail bed. I know all that interference from nails will compromise depth, but IN GENERAL, at a clean site with moderate mineralization, what is considered to be the maximum target depth for the three coils? We always hear about the CTX pulling stuff that was too deep for other detectors, but I have yet to see this. With my stock coil I rarely see depths on my screen deeper than 6-7" even in clean ground. I think the deepest recovered target with that coil was a measured 11" this summer (which was impressive to me because it was a large cent in a hole with about half a dozen nails).

I get that there are a lot of variables contributing to the question I just asked, so any answer is an estimate or ballpark answer, but I'm curious as to what the general consensus is. I'm also considering getting the 17" sometime in the coming year for the rare clean area I can find, but I want to maximize my depth regardless of what coil I'm using. Part of that is learning to deal with the feedback and noise from manual sensitivity, and I'm working on that, but I'd like to know roughly how far I am from achieving that depth I've always read about.

 

[sprchng]

Dirt type probably has more to do with the depth one gets than the trash embedded in that dirt so depth will vary greatly from one location to another, mineralization and iron content being the most important factors.Therefore , the generalization that coil depth is proportional to coil diameter is as close as you can probably come to a blanket statement covering depth although , I don't think the 17" will get you 17" of depth in most soils while both the 11" and 6" can certainly hit their diameter in depths in decent soil.

 

[TrpnBils]

Man I must not have deep targets in my area or something then because I've probably only seen 9-12" depths on my meter about half a dozen times.

 

[tcornel]

I use the 17" as my standard coil. I was impressed a couple weeks ago when it picked out a couple pennies among iron nails. One hole was 4" deep and had 3 nails in addition to the penny. It will go up to elbow deep if the soil conditions are just right. 10 to 12 inches are pretty common.

It seems that I rarely use the 11" coil. If the site is too trashy I drop to the 6".

 

[Jason in Enid]

I think that soil composition and moisture level plays the biggest factor in what depths you can recover targets at. For me, I have hit dimes and quarters at 9 - 10 inches with the stock coil. I have hit them at 12" with the 17 coil, and I have hit them at 7-8 with the 6 inch. I have hunted side-by-side with AT-Pro users who I would call over to compare signals and they could not hear anything or at most they got an iron grunt, but nothing they would ever dig. Not every site is going to have super deep coins, and conditions today may not let you see the deep ones, but next week or month, you may.

There is not a direct correlation of coil size to depth. Now, if you are talking large targets, things are totally different. I have dug 3 foot holes on the beach for a beer can

 

[TrpnBils]

right - like I said I know there's a lot of variables in play here. More looking for something even as simple as what some of you guys have given, which is "I've found coins X inches deep with this coil".

Is a foot too ambitious for the 6" coil? Just about certainly yes.
Is 8"? Probably.
Is 6"? It seems like that should be possible under the right conditions.

I'm figuring maybe once I work over some of these iron sites I have and just bit the bullet and dig as many nails as possible to get them out of the ground I might need to just completely clear an area and go over it again with the stock coil.

 

[bklein]

Are you wondering about whether the ID displays targets as more than 11" deep or are you saying the detector doesn't detect deep enough?
Mine with the 11" coil has found targets way over 11" but I don"t know if I ever have seen a depth reading over 11". I don't pay much attention to the depth reading most of the time.

 

[TrpnBils]

Neither really - I'm more wondering if I cover a given area thoroughly with, say, the 6" coil how much deeper I can expect to hit with the stock coil if I go over it again and then the same with the 17".

 

[Bryan V]

I have run my 17" coil a lot this year and I would guess it gets not much more than an inch more depth than the stock coil.
I have never dug a dime past 10" with either of the bigger coils. Lots of 9" coins with both coils.
My ground is fairly mineralized with recommended sensitivity running in the single digits to low teens.
I have to run in manual sensitivity and put up with ground noise to get the deep coins.
I hardly ever use the 6" coil. I have hit coins to up to 8" with it but I just don't have the patience for it.
If it's trashy I just put on my 11" coil and slow down. The 11" coil is hard to beat.
Bryan
AKA Cabin Fever

 

[Champ Ferguson]

I agree that soil mineralogy and moisture are the major factors. Around most of my sites, top soil is measured in inches, like 4-6 and is underlain by a dense clay layer. You just don't find metals in that clay unless it has been disturbed. Now move over a bit onto a riverbottom and the topsoil depth can go to feet. When they excavated for our jail recently, they went down 8' to lay the footers and the officer in charge of the jail told me it was beautiful organic rich topsoil at that depth. Hunting in the shallow clay sites, I use my stock coil, but in deep rich soils, I hunt the 17.

There's a lot a factors that influence depth (as others have posted) and a lot of the fun is figuring out which apply and how much each applies to a particular site.

 

[jas415]

Around Houston, there are 'iron ore' driveways and parking areas. In that stuff I am lucky to get 3" deep with any coil. In the really trashy sites with lots of nails, I really really slow down and pick around the edges. I find that a normal swing speed will get almost zero targets. If i really slow down, I can get the tweeks and then I investigate them. In really trashy areas I can usually depend on 5-7" depth with the small coil. I also find that my machine is a male machine, it lies about how deep it will go. I see depths on a sweep of 9-11 inches but in pinpoint they are more often about half that. The actual dug depth is a lot more close to the pin point depth.

 

[sube]

Here's my take on depth the 6 is average 6 to 8 inches with a rare 9 inches , the stock will go to 8 to 10 with a rare 12 inch find the 17 i have not used much well go 10 to 12 with a rare 14 inch find these are with dime size coins .Now with that said the only thing that well change these depths is ground minerals the more mineralization the less depth.

Just as a small piece of iron will above a coin mineralization is doing the same either the iron or ground signal is stronger than the return signal of the coin .

Now manual sensitivity well be deeper than auto manual at 15 will be just as deep as auto plus 3 at 22 you can look at it this way you can get 40 percent more depth with manual as compared to auto and you will gain 10 to 20 percent more depth in pinpoint sizing than manual .

Now if you run manual hot say 30 with the 6 which i can do in my ground most of the time .People will tell you it will false more because you are say 8 point's over what the machine is suggesting .The reason it is falsing more is because you are going deeper seeing more nails or iron now it will have more noise than auto because it is seeing more ground minerals another words it see's everything .

EMI and ground minerals is where the noise is coming from . I aways set up my sensitivity by watching what my curser is doing if the curser is bouncing all over the screen it's to high i will set it where the curser is stable and not jumping all over the place regardless of how noisy it is for the best depth .

Now people continually say more sense equals more falses wrong i will be making a video showing this , there are only two types of falses you will get a false directly over the target and the one that is throw en from the target. I will show this in the video that being at 5 in manual or 20 will false just the same the only thing that helps falsing is your fe line .But the fe line will not get rid of the throw en false regardless of where it's set.

The one that's throw en from the target will give the perfect audio and curser placement on the screen a dig me hit but when you pinpoint it moves up to 6 inches away there's no target under the spot where that high tone is coming from if there was a target there it would be what your #s and trace would say .Now if there was a target there any target that nail that's 6 inch away throwing that false can't happen because the target that's under the coil will be the dominate target signal .So when you pinpoint and it's not there and ends up being 6 inches away move on. This is the one everybody chases

Now a false that happens with a target under the coil such as Jeffs video will usally double false such as a nail .
This false is easy to get rid of by the double high tone or looking at the screen .sube

 

[IDXMonster]

AGREED Champ,figuring out what to do with what you have...and THEN having a machine that is ABLE to make most if not all of those needed adjustments is huge. I think it was quantified over on Dankowskis forum at one point where he thought only 5-10% of coins have been recovered,and that most of that equation was based on ground conditions and the ability of a machine to see the target in the first place. Then the operator has to be savvy enough to interpret the info,IF the machine can give ANY indication that a coin may be there.

Jeff,it doesn't sound to me like you're doing anything wrong,it takes some time to become one with any machine for sure. I spent 3 years with my IDX,then modded it and then another year. The things I learned from the start to when I effectively stopped using it were really mind boggling. Some guys never get that far,they're not inquisitive enough to follow something to the N-th degree. You are the person that the CTX needs....the guy that will make the machine all it can be,in time. I'm also that guy. I also have a cutoff point in a site where I will walk away,at least for awhile,because I've tried everything I can think of and have learned and yet, there is nothing there. Your old site with the 1700s coins at 5" is a real temptress...common sense says coins must be there below 5" but you're going to go through hell to make sure. As long as YOURE OK with it, digging ANYTHING that sounds or looks like a possibility may be the only way through the gauntlet. For that certain situation,the CTX may not have the surefire answer,it may be a scientific impossibility for any machine or coil to tell without a doubt that a coin is there. So you step further out on the limb with the CTX as a guide in hopes of finding that once in a lifetime find. And that time out on the limb will teach us stuff about how things operate at the very fringes of recovery.

I know I haven't really helped you one iota but I can relate to what you're going through as almost everyone who dares hunt a site like yours can. From day one it has blown my mind that there are SO MANY nails of all kinds in the ground...EVERYWHERE!! Getting through/around/under them has been a challenge for sure. Maybe a rototiller to at least mix things up?

 

[TrpnBils]

AGREED Champ,figuring out what to do with what you have...and THEN having a machine that is ABLE to make most if not all of those needed adjustments is huge. I think it was quantified over on Dankowskis forum at one point where he thought only 5-10% of coins have been recovered,and that most of that equation was based on ground conditions and the ability of a machine to see the target in the first place. Then the operator has to be savvy enough to interpret the info,IF the machine can give ANY indication that a coin may be there.

Jeff,it doesn't sound to me like you're doing anything wrong,it takes some time to become one with any machine for sure. I spent 3 years with my IDX,then modded it and then another year. The things I learned from the start to when I effectively stopped using it were really mind boggling. Some guys never get that far,they're not inquisitive enough to follow something to the N-th degree. You are the person that the CTX needs....the guy that will make the machine all it can be,in time. I'm also that guy. I also have a cutoff point in a site where I will walk away,at least for awhile,because I've tried everything I can think of and have learned and yet, there is nothing there. Your old site with the 1700s coins at 5" is a real temptress...common sense says coins must be there below 5" but you're going to go through hell to make sure. As long as YOURE OK with it, digging ANYTHING that sounds or looks like a possibility may be the only way through the gauntlet. For that certain situation,the CTX may not have the surefire answer,it may be a scientific impossibility for any machine or coil to tell without a doubt that a coin is there. So you step further out on the limb with the CTX as a guide in hopes of finding that once in a lifetime find. And that time out on the limb will teach us stuff about how things operate at the very fringes of recovery.

I know I haven't really helped you one iota but I can relate to what you're going through as almost everyone who dares hunt a site like yours can. From day one it has blown my mind that there are SO MANY nails of all kinds in the ground...EVERYWHERE!! Getting through/around/under them has been a challenge for sure. Maybe a rototiller to at least mix things up?

Yep, I don't think I"m doing anything wrong in this regard at all, just wondering for curiosity's sake what other people are getting as far as depth goes. I think it's exciting and encouraging to think that below the nail bed potentially lies another untapped stash of coins. This place I'm thinking about is a hay field that hasn't been plowed in 10+ years but lots of guys who have seen me hunting it tell me I'm nuts because they tried it a long time ago and there was way too much iron. There is, but the Etrac cut through a lot of it and now I'm working it with the CTX once the grass that was allowed to grow there uncut last year gets pushed down a bit. They logged an area behind this field last spring, so they had equipment parked on it for a few months and it really packed the dirt in and ripped the hell out of the site. Hoping that this year they'll plow it to loosen it up a bit and pull up some deeper coins. For all the big copper I've pulled from there along with CW relics I know I haven't even begun to get it all. There's a LOT of nails! lol

 

[Ben Town]

How about pinpointing with the 17" coil?
The stock coil on the 3030 does good and I would guess the 6" is a snap up the 17" is one big coil and I'm just courious how it pinpoints.
I plan on getting both before spring.
BT

 

[TrpnBils]

6" pinpointing is great. The coil is about the size of a normal plug anyway so you don't really even need to X the pinpoint. Just get the best pinpoint signal and dig.

 

[Jason in Enid]

The 17" pinpointing is fine. If you can pinpoint with the 11" then you can pinpoint with the 17". If I'm using the 17, I'm normally out in a field so not trying to dig super tight plugs anyway, but I've never had a problem with the target not being where I dig.

 

[IDXMonster]

Using the "wiggle back" method is what I use with all 3,no problem at all. The 17" coil is still very precise at telling you where the signal is,especially in Auto. It's not a big fuzzy blob that you have to take a guess as to where anything is,no worries. Wiggling something that big does take a bit of extra effort but it's not a deal breaker by any means...

 

[Champ Ferguson]

How about pinpointing with the 17" coil?
The stock coil on the 3030 does good and I would guess the 6" is a snap up the 17" is one big coil and I'm just courious how it pinpoints.
I plan on getting both before spring.
BT

Its tougher, or at least it was for me. It definitely takes a bit of practice to get as good as you can get with the stock coil, but after a hunt or 2 you should get to that point. (I always use sizing pp)

 

[Porschephile]

I think that soil composition and moisture level plays the biggest factor in what depths you can recover targets at. For me, I have hit dimes and quarters at 9 - 10 inches with the stock coil. I have hit them at 12" with the 17 coil, and I have hit them at 7-8 with the 6 inch. I have hunted side-by-side with AT-Pro users who I would call over to compare signals and they could not hear anything or at most they got an iron grunt, but nothing they would ever dig. Not every site is going to have super deep coins, and conditions today may not let you see the deep ones, but next week or month, you may.

There is not a direct correlation of coil size to depth. Now, if you are talking large targets, things are totally different. I have dug 3 foot holes on the beach for a beer can

Almost my experience exactly...