What is better for picking through trash and detecting deeper targets?

[BH505Man]

I've heard conflicting opinions as to what is most effective in detecting in a trashy area and being able to lock on and detect the deeper good targets... a faster recovery speed or a slower recovery speed. What is your experience on this and why?

 

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[eman1000]

The answer depends on how "trashy" the site really is and how likely targets are deep. At a "machine gun" site where the targets are so numerous that the audio is information overload to your ears. I would take faster recovery speed over slower recover speed ( in conjunction with smaller coil and slower & tighter sweep) Assuming the site is not that Trashy but has moderate amount of trash and I suspect targets could be located deeper than 6-8" then I might start with a larger coil and slower recovery speed.

If I can only hunt the site once - Faster recovery speed. If I can hunt multiple times I will hunt a trashy site until it is cleaned up enough I can either run a larger coil and/or lower recovery speed. I find less of a difference in actual depth based on recovery speed than I do the machines ability to give me accurate VDI information. I'm more apt to run a larger coil or different machine across a site that adjust recovery settings but if I only had 1 coil and 1 machine then I would clean the site with faster recovery and then hunt from a different direction with a slower recovery speed.

I think this article sheds some light on the problem if I'm allowed to link to it. https://www.dankowskidetectors.com/painful_truth.htm

 

[bigscoop]

I've heard conflicting opinions as to what is most effective in detecting in a trashy area and being able to lock on and detect the deeper good targets... a faster recovery speed or a slower recovery speed. What is your experience on this and why?

Faster recovery speeds provide less depth, decreased target information, and decreased returns, this is what allows the processor to work faster. Slower recovery speeds increase depth and provide the most returns and the most target information possible, which is why the processor needs to work slower. So when hunting trashy areas it's a constant balancing act, as it all just depends on the amount of trash, the type of trash, the size of the coil, the speed of the coil motion, etc. Sensitivity is also part of the balancing act, as too much sensitivity can actually make targets appear larger in the search field by creating something similar to that of a halo effect around the target. This will usually result in poor/harder target separation and an increase in clipped and blended target responses, pinpointing will also become more difficult.

 

[sphillips]

I am in the same situation. I have permission to detect a house that was built in 1901 that has 120 years of trash. I have detected the front yard 4 times, first time I came up with an 1896 V nickel. Nothing old since then, just modern coins and the normal trash.Cant take a step without getting a signal of some kind.

 

[bigscoop]

I am in the same situation. I have permission to detect a house that was built in 1901 that has 120 years of trash. I have detected the front yard 4 times, first time I came up with an 1896 V nickel. Nothing old since then, just modern coins and the normal trash.Cant take a step without getting a signal of some kind.

Super trashy and deep just don't don't go hand in hand regardless the machine. The way I handle these type of situations is to pick a small section, say a 30x30 foot block and then I use a small coil and I proceed to try to slowly pick it apart with a recovery speed of about 6 and around a 15-18 sensitivity. The other thing I will do sometimes is to first use the larger coil with a faster recovery speed and I'll go for all of the easier targets first. The worst situations are those places that are heavily infested with non-ferrous trash, these type of situations can drive you and your machine absolutely batty. In these situations you can't use very much sensitivity because that will only create something of a hallo effect around these non-ferrous targets which has the same effect of making them appear even bigger, which only compounds the problem.

 

[sphillips]

Super trashy and deep just don't don't go hand in hand regardless the machine. The way I handle these type of situations is to pick a small section, say a 30x30 foot block and then I use a small coil and I proceed to try to slowly pick it apart with a recovery speed of about 6 and around a 15-18 sensitivity. The other thing I will do sometimes is to first use the larger coil with a faster recovery speed and I'll go for all of the easier targets first. The worst situations are those places that are heavily infested with non-ferrous trash, these type of situations can drive you and your machine absolutely batty. In these situations you can't use very much sensitivity because that will only create something of a hallo effect around these non-ferrous targets which has the same effect of making them appear even bigger, which only compounds the problem.

Thx Big scoop, I learn something every time you post!

 

[sube]

Super trashy and deep just don't don't go hand in hand regardless the machine. The way I handle these type of situations is to pick a small section, say a 30x30 foot block and then I use a small coil and I proceed to try to slowly pick it apart with a recovery speed of about 6 and around a 15-18 sensitivity. The other thing I will do sometimes is to first use the larger coil with a faster recovery speed and I'll go for all of the easier targets first. The worst situations are those places that are heavily infested with non-ferrous trash, these type of situations can drive you and your machine absolutely batty. In these situations you can't use very much sensitivity because that will only create something of a hallo effect around these non-ferrous targets which has the same effect of making them appear even bigger, which only compounds the problem.

This just does not sound right your detector is operating a fixed field you can't raise or lower it's set and can't be changed more power less power and so on.
Buy adding more sensitivity you are going to make the big targets louder and the small targets louder and you can always turn your volume to max and lower your volume in your headphones so if those big targets are loud and the small targets are faint changing sensitivity will not change this at all one will be loud one will be faint.
But running low sensitivity will only make the faint targets fainter not as loud by running less sensitivity.Running higher sensitivity the bigger targets will be louder and so will the smaller targets .
As long as the machine is stable why not use more sensitivity to here the fainter targets.
To bad we don't have a gain setting on the nox like the ctx maxing gain makes all targets the same in volume faint or loud.
As far as halo effect on larger targets because of using to much sensitivity you could say the same of smaller targets to .
Show me in a video where at low sensitivity you can hear both faint and big targets sweeping over them ,then show me by using higher sensitivity you will not hear the fainter target.

Going back to the ? from the member here recovery speed means nothing to me past 4 inches all the minelab coils for the nox separate the same 6 11 12x15 at 4 inches get deeper like 5 in muti none separate try with a dime and pull-tab 3 inches a part one to 4 inches good separation at 5 you will only here pull-tab i still don't know what all the hype is on separation and recovery speed. Here's a vid you tube ((((((((((separation 0011 )))))))). sube

 

[bigscoop]

This just does not sound right your detector is operating a fixed field you can't raise or lower it's set and can't be changed more power less power and so on.
Buy adding more sensitivity you are going to make the big targets louder and the small targets louder and you can always turn your volume to max and lower your volume in your headphones so if those big targets are loud and the small targets are faint changing sensitivity will not change this at all one will be loud one will be faint.
But running low sensitivity will only make the faint targets fainter not as loud by running less sensitivity.Running higher sensitivity the bigger targets will be louder and so will the smaller targets .
As long as the machine is stable why not use more sensitivity to here the fainter targets.
To bad we don't have a gain setting on the nox like the ctx maxing gain makes all targets the same in volume faint or loud.
As far as halo effect on larger targets because of using to much sensitivity you could say the same of smaller targets to .
Show me in a video where at low sensitivity you can hear both faint and big targets sweeping over them ,then show me by using higher sensitivity you will not hear the fainter target.

Going back to the ? from the member here recovery speed means nothing to me past 4 inches all the minelab coils for the nox separate the same 6 11 12x15 at 4 inches get deeper like 5 in muti none separate try with a dime and pull-tab 3 inches a part one to 4 inches good separation at 5 you will only here pull-tab i still don't know what all the hype is on separation and recovery speed. Here's a vid you tube ((((((((((separation 0011 )))))))). sube

I think you're misreading what I wrote. As for the halo effect I spoke of, if you run a high sensitivity, say with a 6" coil, and you get multiple non-ferrous "larger target signatures" under the coil at the same time then those larger "halos" becoming more difficult for the processor to separate. If we lower the sensitivity, and thus reduce the size of the halo effect, then target separation becomes easier for the processor. So this is directly related to the op's question. And yes, when you increase sensitivity the returns will be stronger from both the faints and the closer targets, but only to a point because sensitivity doesn't only effect targets, it also effects everything else in the search field. A sensitivity adjustment is just a filter, nothing more, it is basically telling the processor how much information the user wants to hear. Just because you can't hear it doesn't mean that the processor isn't still having to process all that information because it is, but it's only letting you hear that portion of it that you elect to hear when you adjust that sensitivity filter. Too much sensitivity can also confuse the processor too.

 

[sube]

I think you're misreading what I wrote. As for the halo effect I spoke of, if you run a high sensitivity, say with a 6" coil, and you get multiple non-ferrous "larger target signatures" under the coil at the same time then those larger "halos" becoming more difficult for the processor to separate. If we lower the sensitivity, and thus reduce the size of the halo effect, then target separation becomes easier for the processor. So this is directly related to the op's question. And yes, when you increase sensitivity the returns will be stronger from both the faints and the closer targets, but only to a point because sensitivity doesn't only effect targets, it also effects everything else in the search field. A sensitivity adjustment is just a filter, nothing more, it is basically telling the processor how much information the user wants to hear. Just because you can't hear it doesn't mean that the processor isn't still having to process all that information because it is, but it's only letting you hear that portion of it that you elect to hear when you adjust that sensitivity filter. Too much sensitivity can also confuse the processor too.

Do you have a video showing this . sube

 

[sube]

This is what happens the field is narrow shallow and gets wider the deeper you go thereby seeing the dime and pull-tab so if the nox is a low conductor metal detector it will pick the pull-tab . As i said what does recovery speed do for you where the good coins at depth are 5 inches or more. sube

 

[bigscoop]

View attachment 1922330 This is what happens the field is narrow shallow and gets wider the deeper you go thereby seeing the dime and pull-tab so if the nox is a low conductor metal detector it will pick the pull-tab . As i said what does recovery speed do for you where the good coins at depth are 5 inches or more. sube

The field doesn't get bigger or smaller when you adjust sensitivity up or down, the field actually remains the same size, all the sensitivity "filter" is doing is either decreasing or increasing the amount of activity in the field that reaches your headphones. Sensitivity isn't increasing or decreasing power output, it isn't making the field larger or smaller. When you increase sensitivity you're allowing more of the weaker returns and disturbances to be heard, and when you decrease sensitivity it's only allowing the stronger returns and disturbances to be heard. "Recovery Speed" is actually best thought of as being a filter behind the sensitivity filter, this filter adding additional filtering to those returns that get processed/classified. Run too much sensitivity and you start to confuse and overwhelm the processor, which directly effects its ability to efficiently separate targets. I did a video on "clipping" but if I had been running too much sensitivity I wouldn't have been able to separate those two items, a pull tab and a coin.

 

[bigscoop]

Backing up a bit let's touch on something else. Let's say we have notched out nickels, the processor still has to process these rejected returns because if it didn't it wouldn't know that the user has requested not to hear those selected returns. So the processor is still having to process those returns, it's just not allowing the user to hear them at the user's request. So here again, each notch selection is just acting as another filter, but these items are still being detected in the search field and getting processed.

 

[bigscoop]

Take a fairly large man’s gold class ring, or a fairly large woman’s sterling silver ring, both having thinner bands but wider settings. Now slowly rotate them around as you move the item under your machine’s coil one at a time, if the VDI readings on your machine remain fairly tight as you rotate each ring then that machine is more heavily weighted to conductivity, however, if the range of VDI readings grows much wider and more erratic as the broad portion of the ring is turned toward the coil then that machine is more heavily weighted to size and shape. All of this matters when hunting heavily trashy areas, and especially true when those areas are heavily infested with non-ferrous trash. Iron is much easier to deal with.

 

[sube]

The field doesn't get bigger or smaller when you adjust sensitivity up or down, the field actually remains the same size, all the sensitivity "filter" is doing is either decreasing or increasing the amount of activity in the field that reaches your headphones. Sensitivity isn't increasing or decreasing power output, it isn't making the field larger or smaller. When you increase sensitivity you're allowing more of the weaker returns and disturbances to be heard, and when you decrease sensitivity it's only allowing the stronger returns and disturbances to be heard. "Recovery Speed" is actually best thought of as being a filter behind the sensitivity filter, this filter adding additional filtering to those returns that get processed/classified. Run too much sensitivity and you start to confuse and overwhelm the processor, which directly effects its ability to efficiently separate targets. I did a video on "clipping" but if I had been running too much sensitivity I wouldn't have been able to separate those two items, a pull tab and a coin.

In my crappy picture above it is only showing the field of the coil it is fixed can't be changed nothing to do with sensitivity recovery or anything it is fixed .I was only showing the field of the coil .
As you can see the field is tighter closer to the coil as we get farther away the field widens thereby seeing bought targets so if there are two targets under the coil no separation happens .
The field is fixed high sensitivity or low recovery fast or slow will not change the field where separation happens is where the field is tighter letting you see one target at a time such as closer to the coil not bought.

Thanks for the vid but what i am seeing is the coin and tab are at the boarder line of separation what happens if you go deeper.
Change that coin to a dime for a fair test or penny the quarter is much more conductive then the dime to the tab i know i am nick picking but what i am saying is you can't have separation when two targets or in the same field at the same time unless one is in a weaker part of the field. Thanks you for the vid . sube

 

[bigscoop]

I get what you're saying, and have done the same with various/different targets numerous times. And sensitivity does matter a great deal as too much sensitivity can actually decrease the machine's ability to detect the space between the two targets, thus making it more difficult for it to identify that separation. I practically live in super trashy areas these days, most of this being ground that is super infested with non-ferrous targets of every nature, even with the small coil and iron eliminated I still frequently encounter that machine gun effect due to all of the non-ferrous targets. That's how bad this ground is in many places, and yet I'm still able to ferret out good targets with pretty consistent results and my sensitivity setting has a great deal to do with that. BUT, it can also depend on the machine, as well, and what I'm actually searching for.

Per example, I’ll be going over to my local old trashy park later this afternoon to a couple of heavily infested non-ferrous sections. Now if I was going over there to coin shoot I’d take the Nox, but this afternoon I’ll be trying to pluck a few pieces of gold and silver jewelry from all of that non-ferrous crap so I’ll be taking the Sov. Gt. Why? Because the Nox is more heavily weighted to size and shape, whereas the Sov is more heavily weighted to conductivity.

With the Nox, if I were to attempt to pluck gold and silver jewelry from these non-ferrous mine fields then I’d have a real problem attempting to do this because gold and silver jewelry can show up anywhere on the Nox’s very narrow non-ferrous scale, this further complicated due to it's heavily weighted size and shape defaults, this all just depending on how the item is positioned in the soil and the size and shape of that item. However, with the Sov Gt, this range isn’t near as broad on it’s much wider VDI scale as the Sov is more heavily weighted to conductivity, this machine’s true variable tone also providing more information as to a target’s size and shape and density, all of this providing much tighter readings and lot more target information, something the Nox can’t provide.

The trade off, however, is that the Sov requires slower progress in these super trashy non-ferrous areas and it’s application is more tedious. So I’m not going to be able to cover near as much ground as I can with the Nox. And here again, my sensitivity settings will be crucial.

And one more thing worth noting, the vast majority of the targets I recovery from these areas are less then 5" deep, and I've got to acquire a pretty good window in order to do that, which means that I want the narrowest target signatures possible. Now I will recognize a few deeper targets but because this is a public park I have to pass on them because in order to reach them I'd have to create more noticeable holes/plugs. However, if I were water hunting, which I also frequently do, I could then pursue these deeper targets without that same concern and most of these deeper targets are simply recognized by the "clipping" and not a full lock on those targets until I've gotten all of that other crap out of the way.

 

[sube]

Again i want to learn show vid where to much sensitivity looses the target using a stable setting . As far as i see raising sensitivity and lowering it only affects bought targets the same louder or quite if it sees bought targets there still there.
Plus one on the sov gt as can be said of any fbs
The nox is suppose to be a great separator (recovery speed) not seeing it past 4 or 5 inches in muti. sube

 

[bigscoop]

Again i want to learn show vid where to much sensitivity looses the target using a stable setting . As far as i see raising sensitivity and lowering it only affects bought targets the same louder or quite if it sees bought targets there still there.
Plus one on the sov gt as can be said of any fbs
The nox is suppose to be a great separator (recovery speed) not seeing it past 4 or 5 inches in muti. sube

The Nox does have good target separation, but because of it's priority defaults (size & shape) and its very narrow VDI scale, it isn't all that good (capable) at classifying potential gold and silver jewelry items because when it comes to gold and silver jewelry there there are no consistencies in the various sizes and shapes of these items, unlike coins, where each denomination is pretty darn consistent.

As for the sensitivity issue, just lay a quarter on a clean section of ground and see how the target signature gets smaller and larger as you decrease and increase the sensitivity, this only becoming even more exaggerated the closer the item gets to the coil.

Now, with that same quarter and clean ground, start with a high sensitivity setting and see how high you can raise the coil before you start losing the return, this space (depth) will continue to decrease as you continue lowering the sensitivity. But you're not making the field smaller, you're just filter out more noise which includes those weaker target returns. Increase the sensitivity and you'll start getting those deeper (weaker) returns on the quarter again.

As for a video, I'll have to think on that because it would be a rather complicated and long topic. Maybe I could do a series on hunting super trashy areas and address each issue in its own video? Interesting idea that I'll have to ponder over.....

 

[vferrari]

The Nox does have good target separation, but because of it's priority defaults (size & shape) and its very narrow VDI scale, it isn't all that good (capable) at classifying potential gold and silver jewelry items because when it comes to gold and silver jewelry there there are no consistencies in the various sizes and shapes of these items, unlike coins, where each denomination is pretty darn consistent.

As for the sensitivity issue, just lay a quarter on a clean section of ground and see how the target signature gets smaller and larger as you decrease and increase the sensitivity, this only becoming even more exaggerated the closer the item gets to the coil.

Now, with that same quarter and clean ground, start with a high sensitivity setting and see how high you can raise the coil before you start losing the return, this space (depth) will continue to decrease as you continue lowering the sensitivity. But you're not making the field smaller, you're just filter out more noise which includes those weaker target returns. Increase the sensitivity and you'll start getting those deeper (weaker) returns on the quarter again.

As for a video, I'll have to think on that because it would be a rather complicated and long topic. Maybe I could do a series on hunting super trashy areas and address each issue in its own video? Interesting idea that I'll have to ponder over.....

I can agree with many (most) of your points and descriptions of how targets respond when varying sensitivity etc., but as an engineer familiar with signal processing, I have to disagree with your characterization of sensitivity as a filter and also your argument that the compressed VDI scale of the Equinox as somehow limiting the classification of jewelry or even coins and your previous statements that the limited VDI scale somehow indicates an inferior discrimination implementation or is simply inferior to 100-segment ID implementations.

The former comes down simply to terminology I believe, because your description of how sensitivity affects target signal return strength is accurate. But sensitivity is not a filter so much as a gain level adjustment. The problem is that detector manufacturers are inconsistent in their use of terminology of such features such as sensitivity, gain, and transmit power which are improperly used interchangeably and which results in confusion. Sensitivity as implemented in the Nox simply limits the amplitude (amplification) of of the raw target signal (which is received and sampled at the various operating frequencies) before it is digitized and applied to the digital signal processor. A filter would limit the bandwidth (range of target frequencies) that are let into the signal processor - such a filter could be used to limit noise or to notch out specific types of signals.

Regarding the "compressed" range of the Equinox VDI, I have a different take because it appears to be an intentional design decision by Minelab to provide improved target ID stability and repeatability. Yes, there is less precision vs. a 100 segment scale, but I have found the precision of a 100 segment is somewhat worthless if the VDI is constantly bouncing around which is typical of most 100-segment detectors such as Fishers, Deus, and Nokta. Minelab made the conscious decision to prioritize stable and repeatable target IDs which can be used to advantage in detecting - for example, it is really an asset to have a clean nickel repeatedly ID at 13 rather than bounce around between 52 and 55, which is what I often see on my Deus. On my Deus pull tabls also bounce around in this region. On my Nox, pull tabs are either notoriously unstable (a giveaway) or stable but rarely if ever fall on a TID of 13. So in this case, the 50-segment Nox provides the superior TID implementation to help me sort through non-ferrous trash vs. a very capable 100-TID detector. Now if ML can retain the repeatability and stability of the Equinox TID and also increase precision (and perhaps add target information as they do with the FBS2 units with FE-CO target ID numbers) then that would be a great update and replacement for the aging CTX 3030 and eTrac FBS2 detector platforms. A Multi-IQ based detecting with the discrimination sophistication and target ID information implemented in the CTX but with the Speed and adjustability of the Nox would be a formidable high end unit. I am pretty sure Minelab is working on that and I am looking forward to it. Your statement that you can't classify silver and gold jewelry as a result of the fact that "there are no consistencies in the various sizes and shapes of these items" means that a 100 segment ID machine would also have no additional success in classifying these targets. In fact, due to the target ID variablity that results from these targets, I would argue that with a less stable 100-segment ID output, you would be hard-pressed to make any kind of consistent call. The gold items I have found with the Nox pretty much display a solid, stable ID (yes, that ID varies from target to target based on shape, mass, and whether you have a closed loop) vs. modern trash that rings up and bounces around in that range. Regarding silver jewelry, it will usuall ring up high regardless and I am not leaving any repeatable high tone in the ground regardless of target ID. Whether its a 21, 27, or 32, if it is repeatable, I'm just digging it and finding out what it is once I have it out of the ground

I completely agree with many of the points you have made above regarding the magnetic field characteristics of different coils and how sensitivity does not affect field strength, how too much sensitivity can actually reduce your ability to discern a target, etc. How lowering sensitivity can actually enhance you ability to pick up shallower keepers between trash targets (to the OPs original question). You are spot on.

You may disagree with the above, and frankly, that's your right, I am not going to engage in a prolonged debate about it like you are having with Sube on the other issues, because it is not really that big a deal - just disagree on calling sensitivity a filter and disagree that the limited VDI range on Equinox is a liablity- that's all. Otherwise, there is a lot of common ground so I don't want to take away from that with a debate. I just couldn't hold back any longer as you continued to call sensitivity a filter. I'm OCD, I guess.

 

[vferrari]

I've heard conflicting opinions as to what is most effective in detecting in a trashy area and being able to lock on and detect the deeper good targets... a faster recovery speed or a slower recovery speed. What is your experience on this and why?

I guess if I am going to post in this thread, I should at least answer the OP's question.

Similar to what others have said above - unless you are going to brute force yourself through this situation by digging all signals including trash, then you are going to just have to come to terms with the fact that you are going after shallower targets. It makes sense that the shallower targets still remain because they are invisible to older, slower machines.

Newer machines such as the Nox and Deus have higher, adjustable recovery speeds. Deus has superior iron filtering on top of that. So, using higher recovery can help with target separation and your ability to pick out targets from the muck. Don't overdo it on recovery speed, though, as you can end up overly limiting depth and can cause targets to clip into hard to pick up "blips".

Lowering sensitivity helps too - it has less of an affect on the shallower keepers you seek but does significantly lower the nulling or overload effect of ferrous trash targets picked up by the coil.

Use a smaller coil to limit the number of trash targets under the coil at any one time. I like the Coiltek 10x5 as it has great side-to-side separation at 5" width but has decent swing coverage at 10". If you really need a laser pointer, then use the 6-inch round coil.

Go low and slow - control your swing, you can really slow it down with the Nox even at high recovery speeds. Deus tends to need a faster swing with high recovery speeds. Learn coil control and ability to wiggle over a target to bring it out of the much of the surrounding ferrous targets.

HTH GL

 

[sphillips]

O I went back to the 120yr old home again today and detected the front yard. Park 2, sensitivity 18, recovery factory default. All trash except for two quarters, 1972, 1997. Yard is only about 50' X 50', so I intentionally drug every target thinking eventually it will be clean enough to start picking up good targets