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NOX 800 Iron BIAS question
Posted by: greenmeanie
Date: March 07, 2018 07:04PM
Why does Minelab default the NOX 800 Beach IRON BIAS to a 6 but park 2 mode to a 0? I would think the park would have more IRON then at a beach?
SO before I lower my Beach IRON BIAS I thought I would ask if there is another reason for this being so high in beach mode.
Or is it they predict for Black Sand?



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NOX 800

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Re: NOX 800 Iron BIAS question
Posted by: sgoss66
Date: March 07, 2018 08:16PM
greenmeanie -- lower iron bias is supposed to be used to facilitate better iron unmasking. Low iron bias takes "mixed" low tones and high tones -- which may be due either to co-located iron and non-ferrous targets, OR due to a nail along with some falsing off the tip of the nail -- and it "accentuates" the high tones (as I understand it). Whether the "high tones" happen to be nail falses, OR emanating from the non-ferrous member of a co-located target scenario, the machine will "accentuate" the high-tone portion of the signal when iron bias is set low. As such, it's giving you a better chance of hearing any non-ferrous intermingled with iron while sweeping through trashy areas, aiding in attempts to unmask. Meanwhile, high iron bias does the opposite; on a "mixed" target, it trends any high conductive signal near iron toward an iron ID -- with the idea of reducing falsing (but potentially missing non-ferrous targets co-located with the iron by minimizing any hints of their presence).

SO -- the amount of bias you choose depends on whether your primary goal is to avoid falses, OR whether you want maximum ability to unmask (though likely digging more iron in the process).

From that perspective, it makes sense to me to have bias LOW in Park 2 -- as Park 2 is a mode (given its affinity for lower conductors) I would use in an unmasking scenario. Meanwhile, it makes sense to me to have iron bias higher at the beach, since it would be more "stable"/less "falsy," and my focus is not so much on "unmasking" in most cases at the beach.

Don't know if that helps any, or not...

Steve



Minelab CTX 3030
Minelab Equinox 800
Garrett ProPointer AT
Lesche hand digger
Lesche 38D Ground Shark "King of Spades"

Norman, OK

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Re: NOX 800 Iron BIAS question
Posted by: greenmeanie
Date: March 07, 2018 09:39PM
I think I see what you mean.
Thanks for the help.



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NOX 800

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Re: NOX 800 Iron BIAS question
Posted by: Cutaplug
Date: March 07, 2018 11:27PM
Quote
sgoss66
greenmeanie -- lower iron bias is supposed to be used to facilitate better iron unmasking. Low iron bias takes "mixed" low tones and high tones -- which may be due either to co-located iron and non-ferrous targets, OR due to a nail along with some falsing off the tip of the nail -- and it "accentuates" the high tones (as I understand it). Whether the "high tones" happen to be nail falses, OR emanating from the non-ferrous member of a co-located target scenario, the machine will "accentuate" the high-tone portion of the signal when iron bias is set low. As such, it's giving you a better chance of hearing any non-ferrous intermingled with iron while sweeping through trashy areas, aiding in attempts to unmask. Meanwhile, high iron bias does the opposite; on a "mixed" target, it trends any high conductive signal near iron toward an iron ID -- with the idea of reducing falsing (but potentially missing non-ferrous targets co-located with the iron by minimizing any hints of their presence).

SO -- the amount of bias you choose depends on whether your primary goal is to avoid falses, OR whether you want maximum ability to unmask (though likely digging more iron in the process).

From that perspective, it makes sense to me to have bias LOW in Park 2 -- as Park 2 is a mode (given its affinity for lower conductors) I would use in an unmasking scenario. Meanwhile, it makes sense to me to have iron bias higher at the beach, since it would be more "stable"/less "falsy," and my focus is not so much on "unmasking" in most cases at the beach.

Don't know if that helps any, or not...

Steve

Do you think salt water would produce a false like iron too maybe? I don't have any salt water near me but would be curious to see if the 800 would go bonkers in salt water if iron bias was set to low.

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Re: NOX 800 Iron BIAS question
Posted by: sgoss66
Date: March 08, 2018 12:07AM
It's a good question, Cutaplug. I have only been beach detecting once...for a week in Destin, FL this past fall. Ironically, I was using your favorite machine -- the E-Trac! Anyway, the salt mineral effect on the machine seemed to be very low tones, like 01s and 02s on the conductive side...so it is "falsing," but it's not "high-tone" falsing. But, with that said, I'm not sure if iron bias might play a role, there, or not, when dealing with salt mineralization. My guess is "no," but not sure...

Steve



Minelab CTX 3030
Minelab Equinox 800
Garrett ProPointer AT
Lesche hand digger
Lesche 38D Ground Shark "King of Spades"

Norman, OK

Re: NOX 800 Iron BIAS question
Posted by: jas415
Date: March 09, 2018 08:38AM
Steve, I hunt mostly heavily trashed out demolitions around Houston. So, using the logic of 'I want to hear those coins around nails' I would use a lower Iron bias, a lower recovery speed and a medium to high sweep speed? Or a higher recovery speed, with a 'CTX style medium to slow sweep speed? That is the way I have it set up and what I am trying to do but I get no depth at all, maybe 8" at the deepest. But, there just may not be targets deeper! Yes, getting lots of coins and non-ferrous, and sometimes digging 'naily' targets, but switching to the lower freqs seems to be giving me a better idea of iron false at depth using 5 and 10 kz. The higher freqs dont seem to aid that much with bouncy numbers or tones. And, the depth gauge is absolutely no help at all, virtually every target is at least half the depth read with sense at 22-23.
Tks

Re: NOX 800 Iron BIAS question
Posted by: anbenson
Date: March 09, 2018 09:56AM
Since I've got my Equinox I've used it almost exclusively at the beach. I run my iron bias at zero and here is why. My beach has a lot of minerals and you would think that running a higher iron bias would help. However, what I have noticed is that on deeper targets the ground starts to consume the target, so the signal actually sounds worse and eventually goes away the deeper it is. If you lower the iron bias the signal is able to come through better and this is especially true on small low conductive items like small rings. Just a side note, if your hunting a highly mineralized beach like S, Cal. or some beaches in Hawaii you should be using the ground balance features the Equinox offers (I personally like tracking). It runs so much quieter on difficult beaches. Minelab may have the iron bias set high on beach mode simply to avoid having to GB on 90% of the beaches in the world. IMO I would ground balance and lower the iron bias to get better results.

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Re: NOX 800 Iron BIAS question
Posted by: sgoss66
Date: March 09, 2018 10:25AM
jas --

Yes, on the iron bias. If you are trying to "unmask" coins that are "hidden" by the presence of nearby iron, a lower iron bias is what you want. That's the short answer. LOL! Here's the long one...

Let's define, for the purposes of discussion, ANY situation in the ground where you are getting a mix of low tones and high tones as a "mixed target."

Obviously, one type of "mixed target" arises from a coin lying in close proximity to a nail. However, SOME "mixed targets" occur simply because you have a nail (low tone) that is giving you some high-tone "falsing." In other words, not "two separate targets in the ground," but instead ONE target (the nail) that "confuses" the machine a bit, presenting some high-conductive traits within the "receive signal" being seen by the coil, along with the more dominant, low-conductive iron response. (Obviously the degree of this falsing depends upon sensitivity or "sparkiness" of the machine, the frequency being utilized, etc.)

In a PERFECT world, we'd like to have a super-sensitive machine, yet one that does NOT "false" on nails, but instead correctly IDs them ENTIRELY as iron -- and only gives us the "high-tone/low-tone mix" when there are actually two co-located targets. But, we don't have that ability yet. SO, this is where "iron bias" enters the picture, being a tool that can "help" a bit.

If all we want to do is "eliminate falses," we can run iron bias up high, and what we are telling the machine is "on mixed targets, instead of letting me hear iron tones AND occasional high tones, eliminate the high tones...i.e. 'bias' the response toward all iron tones/IDs." This can be good, in that you won't be bogged down by the "sparkiness" of the machine, and you can focus only on the clear, solid, repeatable high-toning targets -- while ignoring most of the nails (as those nails will now ID more solidly as low-tone iron). HOWEVER, the obvious downside is, you will miss some partially masked coins -- because, again, you have told the machine (with your iron bias setting) to "de-emphasize" any high-conductive response that is occurring near primarily iron targets.

ON THE OTHER HAND, if we want maximum unmasking ability, we can run iron bias down low, and in that case what we are telling the machine is "anytime you are seeing some high-conductive response near an iron target, EMPHASIZE those high tones for me; allow them to bleed through." In other words, "bias" the machine toward an emphasis on high tones, in any "mixed target" scenario. The benefit of setting up the machine this way is, obviously, if your "mixed target" happens to be a coin next to a nail, you will be allowing the "coin response" part of the signal to be emphasized -- and thus making it more likely you HEAR that co-located coin. Therefore, low iron bias settings allow you a much better chance of digging "partially masked" coins. HOWEVER, the obvious downside is, you will dig more nails, as again -- high-tone "nail falses" are also a "mixed target," and your low iron bias setting is, again, telling the machine "emphasize" THOSE high tones, also, just the same as it would any high tones associated with a partially masked coin.

SO -- obviously, it's a trade-off. And the answer of "where to set the bias" depends upon what you are trying to do, what your goal is at that time. Do you want to hunt "quiet," and dig ONLY the solid coin hits? OR, are you hoping maximize your unmasking capability in a heavily hunted, nail-infested site?

After all that long-winded response, the point is -- in your speicif case that you described, running iron bias LOW gives you the best chance of digging any partially masked coins in your very trashy site, but it will come with the downside that you will likely dig more "falsy nails." I think you are seeing this, based on your post.

As for your recovery speed, I'd run it high, at this trashy site, since you are trying to "unmask." BUT, again -- as you note -- there is a trade-off there, as well. High recovery speed means less depth, in general, while lower recovery speed allows greater depth (at slower sweep speeds). NO, you will not get "max depth" if you run recovery speed high. BUT, similar to running iron bias low, a high recovery speed will maximize your machines ability to "see" a coin located very close to a nail. Basically, you can think of the analogy of "snapshots..." If I imagine recovery speed from the analogy of telling the machine to take more "snapshots" in a short period of time, and if I shorten my audio/tone response so that I can HEAR each one of these more rapid snapshots, then I have a better chance of hearing multiple, closely adjacent targets, instead of letting one target's audio response potentially "bleed over" and "stifle" the response of the nearby target (as would tend to happen with slower recovery speed and the associated "longer" tone responses).

You are worried about depth loss, with high recovery speed -- BUT -- at a really trashy site, it's hard to get max depth ANYWAY, due to the density of targets. If you have reason to believe there are deep coins there AS WELL AS shallower coins that are masked by trash, then you might need to hunt the site multiple times, at different recovery speeds and sweep speeds, in order to recover as many of the targets as possible. With that said, eight inches of depth, at high recovery speed, is really pretty good, from my view. In other words, not a HORRIBLE loss of depth, but with the benefit of much better unmasking capability. One thing you might do, is do some testing on coins you have buried at various depths; run them at high recovery speed and faster sweep speed, and see how deep you can detect the coin...and then, lower your bias and re-run the coins, at a much slower sweep speed. You will then be able to get a rough idea of the effects of fast recovery, high sweep speed, vs. slow recovery, slow sweep speed. Knowing these "bounds" on either end of the machine's capability, will help you to make a more "educated" decision on how you want to run your machine that day, based on your goals, the type of site, the amount of trash present, etc.

Finally, you asked about sweep speed. That's a tough one, and I'm still trying to work that one out -- testing to see how to match sweep speed to recovery speed.

Here's what I can say. If you run your recovery really low, like minimum, you need to sweep REAALLLY slow, to get max depth. If you run your recovery high, you need to run FAST sweep speeds, to get maximum depth. BUT -- what I haven't yet figured out is, if I am running fast recovery speed, and I am NOT concerned with maximizing depth, but instead focusing on maximizing unmasking capability in dense trash, is it best to sweep SLOW, so as to give the machine the BEST chance to hear all targets that are in close proximity to each other? YES, a faster sweep speed will yield maximum depth when running high recovery speed...BUT...my "inkling" is that the slow sweep speed combined with high recovery WILL give maximum SEPARATION ability. I still need to test this, though, to be sure. It seems obvious that slower sweep speed should maximize separation ability using high recovery speed, BUT -- I want to make sure that slow sweeping does not in some way harm the ability of the machine to "do its thing" (accurately, effectively report on all targets) when running high recovery.

Again, what I feel fairly certain of is slow sweep speed with low recovery speed maximizes depth (and is in fact the DEEPEST way to run the Equinox), while high sweep speed with high recovery speed also maximizes depth for that recovery speed (though, not as deep as slow recovery, slow sweep speed). BUT -- I still need to verify my sense that SLOW sweep speed with HIGH recovery speed might maximize unmasking ability of the unit (while sacrificing some depth). This is how it SEEMS so far, but I need more testing with higher sweep speeds and co-located targets, to verify this to myself...

I know this is "long winded." But I hope it helps a bit...

Steve



Minelab CTX 3030
Minelab Equinox 800
Garrett ProPointer AT
Lesche hand digger
Lesche 38D Ground Shark "King of Spades"

Norman, OK

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Re: NOX 800 Iron BIAS question
Posted by: Jason in Enid
Date: March 09, 2018 11:48AM
Brilliant response Steve!

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Re: NOX 800 Iron BIAS question
Posted by: sgoss66
Date: March 09, 2018 01:15PM
Very interesting/good info, anbenson. This will be helpful for me THIS fall, when I try my hand for a second time doing some beach detecting...

Steve

Quote
anbenson
Since I've got my Equinox I've used it almost exclusively at the beach. I run my iron bias at zero and here is why. My beach has a lot of minerals and you would think that running a higher iron bias would help. However, what I have noticed is that on deeper targets the ground starts to consume the target, so the signal actually sounds worse and eventually goes away the deeper it is. If you lower the iron bias the signal is able to come through better and this is especially true on small low conductive items like small rings. Just a side note, if your hunting a highly mineralized beach like S, Cal. or some beaches in Hawaii you should be using the ground balance features the Equinox offers (I personally like tracking). It runs so much quieter on difficult beaches. Minelab may have the iron bias set high on beach mode simply to avoid having to GB on 90% of the beaches in the world. IMO I would ground balance and lower the iron bias to get better results.



Minelab CTX 3030
Minelab Equinox 800
Garrett ProPointer AT
Lesche hand digger
Lesche 38D Ground Shark "King of Spades"

Norman, OK

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