ground moisture and mixed mode

[Downdeep]

Ran into an interesting scenario recently.

While playing around with the V3 and the "test penny" in my yard when I first got the machine, I found that it appeared that mixed mode would detect and ID the penny better than discrimination with similar settings. The ground was moist at this time but not saturated.

Last weekend myself and a friend with a Safari went to a yard to hunt relics. He got some bullet readings which I checked with the V3 in relic mode using mixed mode audio. Oddly, I got high iron readings instead of the consistent 50's-60's VDI readings I am accustomed too with bullets. The ground in which he got the signals was very saturated, so much so that when he dug the holes they filled with water. The bad readings disturbed me and also brought on a few comments about minelab vs whites

So, when I got home I did some testing. My spot where the penny is in my yard is pretty much saturated too, not quite as bad, but still quite wet. I was amazed that with the same mixed mode relic settings I had used in the first paragraph above, I got the same results as in the yard with the bullets. The penny ID'd as high iron, not a penny at all. I switched off mixed mode audio and went back to standard discrimination. Voila! Penny ID...not 100% consistent, but most certainly enough for me to dig without question.

Theory is then that using mixed mode in saturated ground may cause problems. Does anyone else have experience with this?

 

[TheMarshall]

Hello Deepy.

Has someone been fiddling with the mixed-mode program...........?

You have proved that another program gives the right results, so reload the original copy of Relic and check again.

Help me if you will, "What is a high iron reading"?

High tone? High VDI ? Some numbers please, and what were the Analyser's order of frequencies?....TheMarshall.

 

[Downdeep]

original relic wouldn't touch the penny. I had to up the sensitivities and the gain. I was only using the relic program, with and without mixed mode audio turned on. I think I read what you wrote to mean you thought I was using the mixed mode pro??

High Iron meaning VDI readings / graphing slightly below 0

With the bullet....
Analyze showed middle freq high, pinpoint showed same, which it would with lead. The search screen showed blocks below 0 on all frequencies, with middle freq. fading last, of course. Odd, huh!

I keep editing cuz I'm doing other things on the computer and keep saying things wrong on here!

 

[Monte]

The other differences was performance you received by hunting with All Metal as well as, or in lieu of, motion discrimination only.

Let's take the last one first. When searching in Mixed Mode the All Metal channel is a primary mode and with enough sweep speed the Discriminate mode will override it. That's the theory behind Mixed Mode function, but it will vary between the particular models that employ it. I found that searching in Mixed Mode with the XLT different from the MXT and both different from the Vision/Spectra V3.

More effects come from the ground moisture condition, and that is directly related to the ground's mineral make-up. First, consider ground that is essentially dry and free of any moisture. If the ground mineralization is very uniform from surface down to let's say 10" then it will have a rather uniform affect on the generated electromagnetic field.

Now let us picture that same ground after a sprinkler system has watered it for maybe an hour, or after a steady, gentle rain. Both conditions that might get the ground wet to very wet, and soak he upper 3", leaving the lower 7" dry. You now might have a fairly wet condition and water conducts electricity and that alone can affect some operation, depending upon the coil used, detector used, and settings used. Also, the ground make-up that was very uniform to 10" deep might be chemically changed such that the upper 3" of ground, now being wet, can be a little different to very different from the lower 7" so far as the mineralization status is concerned.

Here in Northwestern Oregon we have a lot of areas that are very mineralized. Using a manually adjusted ground balance detector, you can note the differences in the GB setting at the same location between a very dry (and hard) ground condition in the summer, or having only the top 2" or 3" rather wet from showers or sprinkler systems, and from being very saturated during the winter to early spring when we have our "rainy season." The ground can sometimes be so saturated and soggy that you sink down and 'slosh' as you walk thru a grassy site.

There is still no perfect detector, or perfect condition all the time. You just have to pick the right detector and/or settings and/or search coil for the particular site and conditions. On occasion, ground can be saturated to the point that it is very wet all about a buried desired target and that can potentially enhance the target signal. Sometimes, however, the target is iron and the result is increased good-target masking. On occasion the change in mineralization might benefit us, and other times it hampers overall performance.

Sorry if this wasn't any help.

Monte

 

[Downdeep]

I think I understood that..

To put it into exceedingly simple terms I believe you are saying Yes, that can happen?