Hot soil: frequency & reactivity

[Skiron]

Hi guys,

In my area, and using tracking GB with default ground sens (6), I' getting high 60s to low 70s for ground phase number while sweeping in most areas...unfortunatelly I'm a lite user (ws4 only until Christmas) so no ground mineralization bars to appropriate judge that soil, but I've noticed that my garrett carrot sounds off whenever it touches the ground or even more inside the holes I dig with no obvious remaining target if that's a clue, so I guess that the soil is indeed very hot and mineralized...

So, I read a lot about prefering a higher frequency (eg 18/25 khz vs 8 khz) in hot mineralized soils in order to penetrate deeper, and also a lot of advices to use higher (>2.5/3) reactivity in such hot grounds.

My question is: In such a hot ground with tiny metal soil particles (minerals) all over the place....doesn't the greater wave length of a lower frequency (8khz) penetrate better between the soil particles giving better depth performance vs the higher frequency witch with the smaller wave length will hit every little particle compromising depth?
I would suppose that in very mineralized grounds, the lower frequencies would penetrate deeper due to wave length, without hiting every little tiny soil particle that higher frequency with short wave lengths would do.....isn't that the case? What I'm missing..?

Also, why higher (e.g >2.5/3) reactivity settings work better in such hot environments?
These areas are highly mineralized as stated above, but have medium/little iron contamination (e.g not hearing iron in every swing) so I would prefer to run reactivity @2 or @1 or even @0 in order to achive maximum depth....Could someone explain why in hot mineralized ground the higher reactivity is prefered?


Have a great day!

Regards, Argyris

 

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[signal_line]

"Because I said so." LOL

Well, think about what reactivity does. It is like taking a snapshot of the ground. A wider setting ("0" or "1") takes more ground in the picture, more mineralization. Kinda like a bigger coil does not work as well in that type ground. So by using a faster reactivity, lees ground mineralization is captured.

As for frequency, i have heard it both ways--low frequency is supposed to be better, but some say the opposite. So just have to use a test target or find a weak signal and adjust to the best signal--not always the loudest, but the one you can hear the best.

 

[docweiser]

Without giving away too much of what I am working on let me give an example and a suggestion for what it is worth. The conductivity of the ground will be a variable in how the transmitted wave travels through the Earth. Some frequencies do better in some conditions but the actual signal travels a lot further than one would think. Trying to tune the machine to "see" at its best relative to the conductivity of the soil you are searching is pretty much limited by the design of that machine.

Something you can do is bury different objects in that soil at various depths and play around with your settings, often the signal you want is there it's just not being interpreted as such.

Hope that helps.

 

[Skiron]

"Because I said so." LOL

Well, think about what reactivity does. It is like taking a snapshot of the ground. A wider setting ("0" or "1") takes more ground in the picture, more mineralization. Kinda like a bigger coil does not work as well in that type ground. So by using a faster reactivity, lees ground mineralization is captured.

As for frequency, i have heard it both ways--low frequency is supposed to be better, but some say the opposite. So just have to use a test target or find a weak signal and adjust to the best signal--not always the loudest, but the one you can hear the best.

So, lower reactivity setting (0-1) has the same effect such as using a bigger coil = reading greater ground area = reading more ground minerals simultaneously as targets = masking the real target underneath.....
While higher reactivity is able to get between the mineral signals and hit the real target...... pretty simple explanation if I understood it correctly...thanks signal line!

 

[Skiron]

Without giving away too much of what I am working on let me give an example and a suggestion for what it is worth. The conductivity of the ground will be a variable in how the transmitted wave travels through the Earth. Some frequencies do better in some conditions but the actual signal travels a lot further than one would think. Trying to tune the machine to "see" at its best relative to the conductivity of the soil you are searching is pretty much limited by the design of that machine.

Something you can do is bury different objects in that soil at various depths and play around with your settings, often the signal you want is there it's just not being interpreted as such.

Hope that helps.

Thank you docweiser,

Regarding an appropriate real time test in my hot ground as described in my first post, and let's say that the test target will be a US silver dime...what should I expect regarding depth? What's the "standard pass test" value regarding depth in such hot conditions...?
Based on all I have read, I will give it a go with Tracking Ground Balance, reactivity @2,5 (silencer off) and will try 4 different frequencies...8khz, 12khz, 18khz and 25 khz...should I expect to hit that dime @9''

 

[docweiser]

There is no standard test IMO - the transmitting signal goes well beyond 9 inches so the ability to discern the difference between that conductive dime (dipole) and the conductivity of the ground are the limiting factors. So again, this is machine dependent. Of main importance is not necessarily the frequency but the transmitted signal and how the receiver interprets (processes) the return signals.

Imagine you are trying to "see" a metal can through a wall in your home, what's the first thing the transmitted signal hits and what will this do to mask the return signal you want and how do you get around that?

 

[Skiron]

Don't know if I fully undestood this, but in your example, the detector should first hit the wall and gives wall's signal (like ground minerals), but in order to also hear the metal can signal, I should either eliminate the wall signal or differentiate the can signal in order to distinguish between the two.....something like using goldfield program which "notches" the specific ground signal in order to accept above or below that....right?

Based on this approach, in a hot soil like mine, everything has to do with appropriate ground balance, and not reacticity setting or frequency setting so much...

 

[docweiser]

Bingo Enough said from me.

 

[docweiser]

Actually I will add one more thing but I think you already know this.

The signal returned to your current machine under the circumstances you described DOES include the dime in the data-set.

 

[Skiron]

Yes, so it's all up to make the machine understand and differentiate the dime signal vs the hot ground signals...either completelly eliminating the ground and still hear the dime (the ideal scenario), either hear both of them but be able to distinguish them.

You got me thinking that, when we all say that in a hot ground (with ground phase 65 for example and full bars), preset GB of 90 will affect depth, actually higher default gb of 90 (instead of 65) doesn't affects depth, but just eliminates both ground and target's signal, even if the detector received BOTH signals in the circuit...ground and dime.
Additionally, when we manually lower the GB at 65, we hear the dime not because we gain some depth, but because we let the machine accept both the dime and the ground signals and make them "hearable", and it's up to us/machine to differentiate the two signals to be able what is what and dig....

Practically, in my hot ground, I can lower the GB manually at low 70s to hear the already "received by the circuit" dime, but I will have problem to differentiate it from the already accepted ground minerals.

(now it's up to me to interpreat all the information above to figure out the right setting for this hot ground I have....xmmmmm)

 

[docweiser]

Processing By human ear or machine.

 

[HuntinDog]

That's some very interesting thought.
Now if I can make it work for me.....

 

[docweiser]

That's some very interesting thought.
Now if I can make it work for me.....

You can

 

[signal_line]

Yeah, it would be cool to have a learning function that finds the best parameters automatically.

 

[vferrari]

Detector reactivity to ground phase is subject to a lot of competing factors including mineralization levels, coil size, detector recovery speed (reactivity setting), transmit power, sensitivity, and operating frequency. So you can only really speak in generalities because the combination of factors is daunting.

For mineralized soils, it is best to lower transmit power to prevent transmit signal "scatter" by the soil mineralization high beams in fog analogy). TX2 is standard, so lower to TX1 if you can (white HF coils have fixed TX power) and defintely avoid TX3 in high mineralization. Raise sensitivity, EMI permitting, to compensate for the depth loss but if you are already running at 93 to 95, then raising sensitivity above that doesn't do much for depth.

The Deus Reactivity setting is tricky, it doesn't really take "snapshots" as described previously, it just processes the target signal faster so you can better detect the next adjacent target. The tradeoff is usually depth or target signal clipping which nay make smaller profile or deeper targets less detectable or audible to the user. As far as performance in mineralized soil, it is a mixed bag which also depends on mode (gold field vs. the discrimination modes like Deus Fast) so there is no one size fits all answer as to whether lower or higher reactivity is better in mineralized soil. Some field experimentation and tweaking is required at the hunt site.

Same goes for frequency. I would simply set frequency consistent with the targets of interest rather than worry about mineralization. Lower frequencies to maximize depth overall, especially with larger or higher cobductive targets like copper clad and silver coins and higher frequencies (18 khz and greater) for small targets lije jewelry and buttons and mid conductors like gold, nickel, lead, brass, and aluminum.

Although mineralization affects ground phase, you cannot infer the degree of mineralization present solely from the displayed ground phase number. You need the Fe3O4 bargraph to know the mineralization level.

You can positively or negatively bias your ground balance setting off nominal to eek out some more depth but it will come at the expense of more ground noise (negative bias) or quiet your detector at the expense of depth (positive bias). So pushing ground balance setting "negative" vs. the actual measured ground phase by 3 to 5 points may gain some minimal depth but the detector will likely be chatty with ground feedback. This juice is not typically worth the squeeze IMO. I don't ever really see a need or advantage to pushing GB to a positive bias. You just lose depth. I also typically just run tracking GB on Deus by default. It works pretty well, especially in mineralized soils, with no real downside.

HTH

 

[signal_line]

Yeah, it would be cool to have a learning function that finds the best parameters automatically.

Early versions might only run this function once at start-up but with faster electronics someday maybe every target is analysed for best signal.