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  #1  
Old 02-08-2013, 10:15 AM
Doc_Holiday Doc_Holiday is offline
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Default Detection Depths VS Soil Moisture

Greetings all,
I am extremely new at MDing as I purchased an AT Pro a couple of weeks ago (though I constructed a kit MDer using an AM transitor radio in the 60's).
I live in a semi-rural area in central Virginia on a property developed in the late 50's. I have found approx. 75 coins on my property and keep finding them in areas I have gone over 3 times now. Originally, I used Standard Mode, but quickly progressed to Pro Coin mode (which is far superior) and employ a PP which decreases spent time and increases success by a factor of 4+. Yesterday, among finding clad, I found a '42 washington in an area I have gone over probably five times. Other than becoming more effecient due to time spent detecting, I have, seemingly, noticed clearer signals at greater depth as the soil dries out. Has anyone else noticed this phenomena? Also, the clad coinage always appears the exact same color as the ground soil I find it in, but the 90% silver coinage always looks silver and by far cleaner. Has anyone experienced this?
Thanks for your input.
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  #2  
Old 02-08-2013, 10:23 AM
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I find it quite the opposite...I'd prefer wet ground.

I think you're just getting more proficient with your machine. NASCAR drivers don't do 200mph laps on their first day.

Congrats on the silver.

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Old 02-08-2013, 02:49 PM
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Most MDers report deeper signals with damp soil.

It probably depends on how mineralized the soil is and what detector you are using. I think that the moisture reduces the effect of minerals in the soil, and increases depth.

Yes silver usually comes out shiny, because soil prevents oxygen from passing over the coins. Now if a silver coin has been submerged it turns black, even if it is under the mud, as the water allows enough oxygen, nitrogen, and sulfur compounds to contact the surface of the coin.

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Old 02-10-2013, 06:28 PM
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Our money used to be worth something, and it was valuable. And, it was made out of valuable material. We thought nothing of it being silver, because it was money, and that's what they made it out of. It's all there was. The old silver coins hold up well in the dirt because they were made with a precious metal. I remember how excited I was when I saw my first clad coin. I was about 15. I was collecting coins at that time, and the population was still using Morgan & Peace dollars, & Franklin halves. Now all people use is quarters, dimes & pennys, & a few nickels. I remember my dad was so discusted with the clad coins, he tried to explain to me that our money was nothing more than tokens now.

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Old 02-10-2013, 08:40 PM
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Quote:
Originally Posted by LocoPilot750 View Post
Our money used to be worth something, and it was valuable. And, it was made out of valuable material. We thought nothing of it being silver, because it was money, and that's what they made it out of. It's all there was. The old silver coins hold up well in the dirt because they were made with a precious metal. I remember how excited I was when I saw my first clad coin. I was about 15. I was collecting coins at that time, and the population was still using Morgan & Peace dollars, & Franklin halves. Now all people use is quarters, dimes & pennies, & a few nickels. I remember my dad was so disgusted with the clad coins, he tried to explain to me that our money was nothing more than tokens now.
1) Should a coin contain 100% of its worth in the metal it is made from. The answer is no. This is cost inefficient, and requires the government to set the price of precious metals. We actually want our coins to have little melt value, but attain their value from the country's promise to pay.

2) In the 1940s silver was only worth $0.35 an ounce, not that far off from what the copper value of a silver coin is today.

3) People don't use pennies, businesses do. When is the last time you as a customer used a penny toward a purchase? Businesses use them in much the same way tax tokens were used long ago.

4) They should get rid of the paper $1 bills, and eventually $5 bills. Then redesign the coin system to work like it did 90 years ago, when you could carry $75 in (2013 value) as easily as you carry $3.00 in change today.

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  #6  
Old 02-10-2013, 08:43 PM
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My depth performance craters here in Texas in the summer when soil gets dry. Moisture is a good thing. martin
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  #7  
Old 02-10-2013, 10:09 PM
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I prefer hunting in moist ground because it is easy digging and easier on the grass, but to be honest I really can't seem to tell the difference in dry or wet soil when it comes to depth. I usually hit most of my silver around 5 inches roughly and have dug pennies and dimes at 7 inches, in both dry and moist soil. Unless I'm just missing something and I could be, because everyone I have ever spoken to seems to believe they get deeper targets in moist or ground that is wet. We have harsh ground around here lots of iron mines. So I can see the logic behind the idea; however one difference I do notice on my detector in dry ground is that the VDI reading is affected. Dimes and even pennies for some reason will often come up as quarters sometimes, in moist or wet ground, but in dry ground the VDI seems more accurate and I really don't seem to notice a loss of depth. I do have to examine the sounds and signals a little closer in dry ground and maybe hit the target at a different angle, to determine if I need to dig or not because the VDI is a little different. Last year I dug silver every month but September only cause I didn't go out, but in August I dug 10 silver coins my record for a month was 14 which I did on 2 occasions, both in wet months but my August count wasn't that bad. I'm still pondering the whole concept right now.

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  #8  
Old 02-10-2013, 11:00 PM
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Moisture really helps, though soupy-wet can have a negative impact both on depth and your enjoyment digging in it.

When you search an area for a second or third time, if you approach it from a different angle, you are going to get different results. Masked targets can suddenly become unmasked, simply by coming at them at a different angle.

Top

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  #9  
Old 02-11-2013, 01:34 AM
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Greetings Doc, how's Wyatt? ...

The simple laws of physic apply here... key work is “CONDUCTIVITY” ... the moisture in soil gives you more depth with your metal detector because water is a much better conductor of electricity they dry soil allowing your metal detector's signal can penetrate deeper into the ground when the soil is moist... allowing you to detect deeper targets than when the ground is dry.

Use minimum discrimination, keep your sweep distance short and coil level with the ground... too long of a sweep causes you to lift your coil toward the end of your sweep and your detector’s single to go off to the side rather than into the ground... and keep your coil as low to the ground and level as possible.

Variations in any of these steps effects detection depth and could be why you missed some targets... or you simple did not bring your coil over the target.

It’s not rare to find great targets in areas you have hunted for years... not because your detector is better or because you’re using different settings, etc... but simple because you missed the targets previously... even if you’ve hunted the area repeatedly, and no matter how sure that you are that you correctly overlap your swings. We all miss targets... after all, we are only human...

Hope this helps.

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Silver Hawk

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  #10  
Old 02-11-2013, 01:40 AM
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Quote:
Originally Posted by Topdecker View Post
Moisture really helps, though soupy-wet can have a negative impact both on depth and your enjoyment digging in it.

When you search an area for a second or third time, if you approach it from a different angle, you are going to get different results. Masked targets can suddenly become unmasked, simply by coming at them at a different angle.

Top
Agreed...

Best Regards,
Silver Hawk

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  #11  
Old 02-11-2013, 01:00 PM
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Quote:
Originally Posted by Silver Hawk View Post
Greetings Doc, how's Wyatt? ...

The simple laws of physic apply here... key work is “CONDUCTIVITY” ... the moisture in soil gives you more depth with your metal detector because water is a much better conductor of electricity they dry soil allowing your metal detector's signal can penetrate deeper into the ground when the soil is moist... allowing you to detect deeper targets than when the ground is dry.

Use minimum discrimination, keep your sweep distance short and coil level with the ground... too long of a sweep causes you to lift your coil toward the end of your sweep and your detector’s single to go off to the side rather than into the ground... and keep your coil as low to the ground and level as possible.

Variations in any of these steps effects detection depth and could be why you missed some targets... or you simple did not bring your coil over the target.

It’s not rare to find great targets in areas you have hunted for years... not because your detector is better or because you’re using different settings, etc... but simple because you missed the targets previously... even if you’ve hunted the area repeatedly, and no matter how sure that you are that you correctly overlap your swings. We all miss targets... after all, we are only human...

Hope this helps.

Best Regards,
Silver Hawk
That's the problem. The laws of physics that is.

Let's first look at how target detection happens. The time varying magnetic field from the transmit coil causes a conductive target to develop a current (the so called Eddy current) in response to the transmit coil time varying magnetic field. This Eddy current causes the target to develop a time varying magnetic field around it and it is the arrival of this magnetic field at the receive coil that causes target detection.

Now, these magnetic fields --from transmit coil to the target and the one from the target to the receive coil-- have to propagate through the ground matrix. If the ground matrix was devoid of all mineralization, you'd be getting the same depth as when air testing the detector.

Unfortunately, there are two kinds of minerals in the ground matrix. There are magnetic (ferrous) minerals and there are metal salts (conductive salts).

The ferrous minerals, iron oxides, etc. don't react much differently with changes in ground moisture. They respond to the time varying magnetic field of the transmit coil with an in-phase field of their own and which is largely independent of moisture.

The metallic salts on the other hand, form conductive ions, only in the presence of moisture. There has to be enough water present to dissociate the metallic salts into its ionic components. Now, exactly how this causes a perception of extra depth is still a conjecture.

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  #12  
Old 02-11-2013, 05:55 PM
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I love moist soil.

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  #13  
Old 02-11-2013, 08:42 PM
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Quote:
Posted by Rudy
That's the problem. The laws of physics that is.

Let's first look at how target detection happens. The time varying magnetic field from the transmit coil causes a conductive target to develop a current (the so called Eddy current) in response to the transmit coil time varying magnetic field. This Eddy current causes the target to develop a time varying magnetic field around it and it is the arrival of this magnetic field at the receive coil that causes target detection.

Now, these magnetic fields --from transmit coil to the target and the one from the target to the receive coil-- have to propagate through the ground matrix. If the ground matrix was devoid of all mineralization, you'd be getting the same depth as when air testing the detector.

Unfortunately, there are two kinds of minerals in the ground matrix. There are magnetic (ferrous) minerals and there are metal salts (conductive salts).

The ferrous minerals, iron oxides, etc. don't react much differently with changes in ground moisture. They respond to the time varying magnetic field of the transmit coil with an in-phase field of their own and which is largely independent of moisture.

The metallic salts on the other hand, form conductive ions, only in the presence of moisture. There has to be enough water present to dissociate the metallic salts into its ionic components. Now, exactly how this causes a perception of extra depth is still a conjecture.
Yes! The perception of extra depth is a conjecture. I'm not convinced moisture gives you more depth but not convinced it doesn't either. We are not dealing with electrical charges but with magnetic fields which operate completely different. Water does conduct electrical current better but the question is, "How does it affect magnetic fields?" I really don't think it has much effect on magnetic fields if it did one's compass would work better when it is raining. Then again considering another variable is the iron oxides as they react to moisture. Once again I'm not convinced the magnetic field will perform better at better depths when the iron in the soil is wet, but not totally sure about it.

I lean toward the fact that moisture doesn't affect depth, but I could be wrong about that. Like I said my silver count doesn't seem to be affected during dry season, unless I just don't want to face the heat so I go out less. Now here is a question does the rain loosen the soil and allow the field to penetrate deeper? Will the magnetic field's distance be affected by how compact the soil is? If it is then that could account for the perception of extra depth in moist ground.

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  #14  
Old 02-12-2013, 12:17 AM
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Good info. I always wondered if the moisture had an effect as well.
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