Jason, early this morning our local metal detecting club had our monthly Club Member Outing. During the course of the day I had the pleasure to take a few breaks and discuss various detector/detecting topics with some of the newer members. Not just new to the club, but new to the hobby. Newer? Yes, some have been infrequent to only moderately active for 1-4 years, but even they still consider themselves 'new' to the hobby because they still don't understand their detector. Matter of fact, on days like today I am amazed at how many don't understand some of the very simple things many of us consider 'basics!'
One of the topics that came up had to do with 'wetness' and the effects it might have. So, if you don't mind, I'll lend my views to your query:
"What is the difference between dry ground, ground saturated with fresh water, and ground saturated with salt water's effect on a metal detector and how it perceives what a target is."... Actually, you've included three 'best case' scenarios, and at the same time you've left out a couple of important ingredients in these recipes. That is, you have referred to a waterless state, a freshwater environment, and a saltwater environment, but you have failed to stipulate what the ground mineral make-up or mineralization level is!
So, for the fun of it (and to help get an understanding of water's effects and/or potential effects), let's look at this question a little differently first. Let's re-state the question to be"
"What is the difference between a non-wet environment, a fresh water environment and a salt water environment?"
To answer that we would need something like a non-metal tub about 3'-4'square, and have it resting about 2-feet off the ground so that there would not be any mineralization to factor into the test.
Use a plastic tub that is at least 6" deep, and 8"-12" preferably, and use a Styrofoam block to keep a coin positioned about 3" below the top of the tub.
Affix the 2"-3" foam block with glue to the center of the empty tub. Place a coin on top of the foam block. Turn the detector on with the settings you would plan to search with and sweep the coil over the tub. Keep it level with the top of the tub. You can tightly string some twine across the top to maintain a uniform coil presentation and not 'dip' below the top edge of the tub. Note the audio response from the coin. Compare it with the single you get when sweeping over the empty tub without the coin on the foam block.
That 'testing' shouldn't take too long!
Next, fill the plastic tub to within about an inch of the top of the tub without the coin on top of the foam block. Now you have a 3"-4" square plastic tub filled with freshwater. Again, turn on your detector and sweep over the tub of fresh water and note any effects. Then, place the coin on top of the foam block and it is now about 3" below the surface of the water line, in a total freshwater environment. As before, turn the detector on w/o changes and sweep over the tub and not any responses.
Finally, remove the coin. Add an ample amount of salt water to taste
uke: such that it would come close to duplicating the salinity of the saltwater environment you have in mind. Remember, there's a LOT of water in that tub so you'll need a heavy dose of salt! Stir well to dissolve it all.
Once again, w/o the coin in the water, sweep the coil over the top of the plastic tub and note any responses you might hear.
The last step at this point would be to place the coin on top of the foam block and re-scan the coin in the salty environment and sweep over it to note any difference in response.
Try this with your discrimination set at the minimum setting, too!
"I have heard that saltwater can carry a slight electric charge. When you use the term "moisture conductivity", Are you referring to the electrical conductivity of the ground or something else.".... Do you ever take a bath in salt water? I am sure that ever since we were young our parents and educators have told us not to use any electrical appliances when we're in the bath, shower, pool, etc. Why? Because water can carry a charge (conduct electricity) regardless if it is fresh or salty.
"Moisture conductivity" is just that. The ability for water to conduct electricity. But it is also true that when we make the distinction for the water to be 'salty' or 'salt saturated,' we are adding to the conductive properties of the water.
Usually, you're electromagnetic field won't have any serious challenges from
only fresh water, but salt water is definitely a low-conductive matter that we might have to deal with in our course of detecting.
"I have definitely noticed a difference in how my detector operates over dry ground versus wet ground.".... Yep! Watered-down ground can be a problem to work as well as occasionally a pleasure to hunt.
"Saltwater soaked ground definitely being the worst for my MXT's operation.".... I, too, have had more challenges getting good performance out of my MXT's from saltwater soaked ground, but not in every case. Here in Oregon, the coastal beaches I hunt from time to time are quite mineralized. As you get out into the 'wet zone' you have to deal with the negative mineralized ground and the positive conductive wet salts. What helps me the most with the MXT is using the right coil for the conditions.
"I know it was spoken of in the manual, and that there is a switch setting for salt soaked ground. I have still had trouble with the MXT in the salt mode.".... As have I, but remember, you might be dealing with some bad
ground as well as the low-conductive salts.
"Although this does not have much to do with my question. I simply want a better understanding of waters effects on the operation of the MXT, And maybe some tips on better taking advantage of the MXT's power in conditions that are wet.".... Well, here's what I do. First, I make sure that when I am beach hunting, fresh or salt water, I try to stay in a uniform strata of ground and water. I will hunt parallel with the water, as a rule, rather than towards-and-away. I frequently check both my ground balance setting and my discrimination setting as I move to the next 'zone' closer to or farther from the wet area.
I almost exclusively use a Double-D (widescan) coil for me searches. In the open beach areas I favor the round, 10" EXcelerator. Due to the high mineralization we have at the coast, I usually GB in the Normal mode and then I 'Lock' the established GB. In the DRY coastal beach sand, just like working our nasty, highly mineralized freshwater beaches near Portland, I set the Discriminate level at 'minimum' to allow the most punch.
As I get into the 'wet zone' on a freshwater site, I know that I need to check and adjust the Ground Balance. On the saltwater coastal environment, I want to make sure I have an adequate GB for the high mineralization, then I use the Discriminate control and gently increase it just to the point where I cancel (reject or discriminate) the low-conductive wet salts.
To accomplish this, I bob the coil towards and away from the surface, going from about 6" down to
