Odd instance of totally defeating EMI.

[Ronstar]

I was back this morning in what we call the EMI Hell Zone with the intent of seeing just how much it might take to eliminate it if possible. I was running my standard settings of Park/F/M1, Sens at 25, Thresh at 5, 6 tones.
Once I began to hit the edge of the abyss and she started getting chatty I tried M2 then M3 with no appreciable difference. Went to 4khz and nearly quiet but not more than we are already used to so tried 10 then 15 then 20 and finally 40. 4khz is clearly the winner at this point. Thought about changing Sens and Thresh but then thought why not try Beach and Gold? I started to but realized those setting were all still at default so didnt want to spend that time redoing each main mode. Ok, lets go to Field and see what happens, still a bit chatty it did seem much quieter. Finally got a good 44-45 deep so thinking penny.
This time I stopped and thought what might it do if all the settings were the exact same in Field as in Park? Punched it over to Park and no signal sounding so back to Field and 44-45. What and why???
Dug the signal and pulled a second 1917S wheat at 5-6”!!!
Kept going and hit a solid 38. Could be a bottle cap…… back to Park, choppy numbers and sound. Back to Field and confirmed so dug. Out comes a rifle casing, most likely 30-30 or 32 Special. Head stamp is FA 4 02!!! Why didnt Park hit this when the area is, well a manicured park??? Kept going and deep 46 solid, nothing on Park so dug and pulled a 66 Rosie at 6-7”.

So the question is can EMI mess with one mode yet miss another? Isnt 4khz 4khz no matter what mode? Next thing to try is get a good signal in M1 then graduate up and see what happens. Oh you can bet I’m going back up tomorrow and restart with this new info in mind and see what if anything has been missed previously because of the heavy EMI.

One last observation for now….. dug a 7” large square nail with a rosebud head at close to 8”. Solid 48 in Field and 0 in Park.

 

[thepest]

It's Like reading an adventure novel the way you describe how you figured it out.... Sometimes those moments are worth more than any target... Great Day Indeed
And Now We All Know Your Secret detecting skill

 

[JCR TX]

Interesting. I have not ever seen a dramatic difference between Park and Field modes if set up the same. Park does seem to handle Al trash better, especially in M3 or 4 kHz. Field seems to handle iron trash better, especially in M3 or M1. It would be good to know your conclusions after you have gone back to the site and made some more Apple to Apple comparisons with carefully balanced settings. As far as overall EMI instability, higher levels of Audio Gain amplify it and faster Recovery speeds will too.

 

[JimmyCT]

Maybe a different type of filter made all the difference. Great find on the 1917S wheatie!!



This time I stopped and thought what might it do if all the settings were the exact same in Field as in Park? Punched it over to Park and no signal sounding so back to Field and 44-45. What and why???
Dug the signal and pulled a second 1917S wheat at 5-6”!!!

 

[Ronstar]

Ok, Day 2. Got exciting right off the git go!
Started out at a point where EMI has consistently been a pain. Ground balanced, let it find the quiet channel, set it on Field/F/4khz and started forward slowly. Nice and quiet, fingers crossed. I should note other than 6 tones, Thresh 5, and Sens 28, all other settings are simply Default. This applies to Park as well.
Not even 50 feet in I get a solid 42-44 hit deep. Switch to Park and chattery but not excessive and numbers jumpy but not locking on. Back to Field and still there. Dig. At 6” out pops a 1903 IH penny!!! Recheck hole and still something in there. Finally found the round clod that was buzzing and after cleaning the dirt off I get a small military button as well. Score!!

Continue on and get another solid hit at 46-48, 0 in Park mode and just jumpy numbers. (Now, keep in mind if I switch over to any of the M modes its pure chaos for chatter. Single freqs at 10 still noisy but less than 40.) Back to Field at still dead quiet and locked on. Dig. At 6-7” I see the silver dime, 1917 Merc in used shape but hey, right?!

I moved on to another area where the EMI is intense. I started getting good hits but it was mostly canslaw like aluminum pieces at 5-8” deep and some tiny. Nothing exciting dug but I was using a wandering pattern due to time constraints. Field ran at 99.5% dead quiet compared to Park at 80% quiet. M modes not even usable in that zone.

I’m noticing the VDIs are off from regular numbers but if solid hit, even one way, something is in there.
This area may be unique in its EMI Hell Zone and maybe what I’m experiencing will not work for you all but my theory is a trick in the bag is worth trying.
Going back to where the items above were found again tomorrow or Thursday and working a grid pattern.

On the back of the button is stamped “Superior Quality” and the shank is intact, Button is slightly smaller than a dime. Any help in identifying is appreciated.

 

[Picketwire]

I think the brass was from a military 30 US cartridge, also known as 30/40 Krag manufactured at the Frankford Arsenal in 1902. That's 121 years old. The button is a general service button that was introduced in about 1902 and is still in use. Congratulations on your finds! You seem to be killing it.

 

[JCR TX]

The button design is The Great Seal of the United States.
Thanks for posting your observations. Something is going on. It would be helpful to understand the interplay of that EMI and the Legend’s filtering in Park mode.

 

[Ronstar]

Thanks guys for the button info…. I dont get a lot of those here.

I have no idea why Field shuts it down but thats two coins and a button now in an area jkline have hit pretty hard with everything from my F75 to his CTX3030. There is a couple places where the Garrett handheld has gone off at knee height above the ground.

Yes 30-40 Krag, no idea what I was thinking saying 32 Special….. partial case today I think may be 30 Carbine, stamped LC 43.

 

[Ronstar]

Last day to play in the HZ!!! This time I approached from well outside the area, running Park/F/M1 Sens 28 Thresh 5. Everything else in default. As soon as I started getting a bit of chatter I worked up to M2 then M3, no change. As soon as I went to 4khz it was 99% quiet as was 10 thru 40. Flipped over to Field (all else the same) and M1 just as quiet as Park 4khz.

As I pushed further in Park 4 started getting chatty enough that I was getting constant signals bouncing around. Switched to Field 4 and dead quiet. When I was at Ground Zero in the HZ it barely started chattering and about five more steps it was gone. Conclusion: Field 4khz is eliminating “my” EMI (whatever the source is no one seems to know).

Ok, started to walk back into the HZ and as I hit signals I would switch quickly from Field 4 back to Park 4 and noted no signal. Progressed up thru 10-40 and then M1toM3 and back to 4khz. Switch over to Field 4 and confirmed signal of 50 at four bars deep. Dig. Clad quarter with a zincoln attached to it. Did the same thing with two clad dimes close by and same results (but numbers were askew by two down, 44-45 instead of 46).

In the HZ I managed to dig quite a few zincolns, poptops and pulltabs as well so it does not eliminate that!!! I have no scientific explanation of why Field is quiet in the HZ but as long as it works I’m not complaining!!!! Out in the open where no EMI is present Field M series works basically same as Park M series.

 

[hodr]

I never really messed with the threshold setting. I noticed that it doesn't produce an audible tone until you get to 11 or 12. Is there a reason it's set for zero in all the modes except goldfield? Is it just a matter of erring on the side of caution for stability?

Has anyone done any tests to see what the difference in detection depth between 0 and say 5 or 10 in a low EMI area where you aren't experiencing falsing?

 

[Odanscoils]

I never really messed with the threshold setting. I noticed that it doesn't produce an audible tone until you get to 11 or 12. Is there a reason it's set for zero in all the modes except goldfield? Is it just a matter of erring on the side of caution for stability?

Has anyone done any tests to see what the difference in detection depth between 0 and say 5 or 10 in a low EMI area where you aren't experiencing falsing?

If I'm not mistaken.
Threshold only functions like a threshold in Gold mode.

 

[Picketwire]

Just because you are not getting lots of falsing does not necessarily mean that you are in a low EMI area. I do a lot of testing in my attached garage. There are multiple sources of EMI there. Consecutive frequency shifts on the Legend there give a different number almost every time. I have a 4khz program on my Deus that is very noisy there until I change the offset frequency one notch lower, then it goes silent although I know this is a high EMI area. EMI is hard to quantify. Just consider the hundreds of sources of it. I think the best way to minimize it is just like Ronstar is doing, comparing different settings on fringe targets. And what works one day may not be the hot setup the next. There is a lot of useful information about EMI on the NASA guy's forum too.

 

[Ronstar]

Ref Threshold. After the last update to 1.11 Thresh began working, I believe, as intended. Previous is was dead silent until 11 and then a lot of pulsing. Once the update occurred it would start very low volume and work up. Here, I can get to 5 and just hear it which kinda is what the manual suggests.
I cant get back to the area until next week to further experiment. One other thing I forgot to mention, when allowing the unit to search for quietest channel in that area it will stop numerous channels each time I did it (in succession just to see if same channel picked).

 

[Waterdog]

What machine was you swinging a Minelab equinox ?

 

[JCR TX]

Checking what Sub Forum this Thread is in will tell if you haven't been following Ron's Hell Zone saga.

 

[Ronstar]

Jkline finally was done water fishing and joined me dirt fishing in the HZ. His Legend is reacting some what different than mine. Its possible some of the sub settings are different so this continues.
Just the fact I pulled two 1917 wheats, a 1917 Merc, a 1942 nickel and a 1903 IH penny out of an area thats been detected to death tells me this has some merit. Especially since those hits were singular and fairly hard. Either way, its nice hunting quietly in an area that once was like hunting in a riot (noise wise).

 

[Odanscoils]

Ronstar.
Are you using the factory coil or the small one ?
I bought the pro package that came with both.
I'm anxious to learn More.
Please keep adding to this thread.

 

[Ronstar]

I was gone to Seattle area for a few days so sorry on the delay. I have both the 11”DD and the 6”. Going to get warm here shortly and by Monday wd will be down on the Lochsa River camping.
My next attack adventure will be to work and area with the small coil on the previous settings mentioned.
I will continue…….

 

[Odanscoils]

I will be Happy to continue following your Adventures.

 

[Odanscoils]

I was gone to Seattle area for a few days so sorry on the delay. I have both the 11”DD and the 6”. Going to get warm here shortly and by Monday wd will be down on the Lochsa River camping.
My next attack adventure will be to work and area with the small coil on the previous settings mentioned.
I will continue…….

I will be Happy to continue following your Adventures.