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Iron Masking.........Getting more with less discrimination
Posted by: Larry (IL)
Date: February 07, 2008 12:06PM
I have been running my discrimination to accept +10 to +94 for many years and I have been very happy with it set that way. It rejects iron and foil and lets the good targets come through...........well that is what I thought.

I had a White's Beach Hunter ID collecting dust so I traded it for an Explorer XS to "play" with, hoping to find some of the deep targets that I might have missed with the DFX. The Explorer has done very well the several times that I have had it out. I found a 1875 seated dime, several other silver dimes, Indian and wheat cents. I have used the XS in yards that I have pounded with the DFX many times and I was convinced there was nothing left except really deep targets. What a rude awakening. All of these finds were not deep at all and should have been found with the DFX. Then the light bulb glowed brightly over my head. All of the targets I found with the Explorer were NOT deep and had iron near the target. The DFX was doing just what I told it to do. Reject the iron.............. but when the iron was rejected, so was anything that was near the iron because of the audio blanking.

I was hunting with the Explorer as most of the Explorer users do............very little discrimination. The Explorer is a very noisy detector and I got tired of listening to the constant calliope music, not to mention that my arm was killing me after just a couple of hours of detecting......BUT, it was finding stuff that I missed.

So this year I will reduce the discrimination down into the iron range. I will accept -30 to +94, rejecting +95 to start with and I may have to go as low as accepting -70. I will have to listen to the iron tones, but by doing so, I will also be able to hear the targets near, over and under the iron. This years goal is to fine tune the iron discrimination pattern to reject most of the iron, yet not miss those good targets being masked by the iron.

One known problem with accepting down to -70 is when I set the DFX down to recover a target, the audio goes bonkers because of the sensitivity to just about everything. One solution is to press one of the arrow keys or menu key to take the DFX out of the search mode while digging. Squeezing the trigger will resume search mode. Even this gets to be a hassle when using the DX-1 probe. So somewhere between -30 and -70 lies the magic number of stability, for me, when the DFX is sitting on the ground.

My other goal this year is to get the DFX set as close to the Explorer as possible and then do side by side testing of deep targets and see for myself just how much deeper the Explorer really does go. There is no doubt the Explorer has a depth advantage, but I don't think it is as much as many believe. Come on spring.........




Larry, I think it has more to do with the Explorers DD coil than the amount of Disc on the DFX
Posted by: Chris(SoCenWI)
Date: January 26, 2008 11:34PM
Registered: 2 years ago
Posts: 508

Almost all the places I hunt with the explorer that have been hit hard with others yield many coins; almost always masked by trash. Very seldom get a target that is not near another chunk of trash.

Let us know what you find out.

Chris



Posted by: desmond
Date: January 24, 2008 02:02PM
Registered: 2 years ago
Posts: 131

I actually accept everything, and dig everything deep. I had a large cent read +95. Maybe I'm missing stuff, maybe not. I still seem to do better with the best data then any other frequency. Finally ventured out to a different park in Brooklyn last Thursday before the freeze.. Found a 3 ring civil war bullet, a merc, a 1864 Indian on the surface (no metal detector needed), and a cut reale in beautiful shape. RUM on one side, and most of PHILLIP on the other. I'll post pictures soon. Still going to get me an Explorer sometime, but nothing beats research. Des in Brooklyn



Re: Iron masking
Posted by: Gary ( KY. )
Date: January 24, 2008 03:44PM
Registered: 6 months ago
Posts: 428

Des

Great finds there at that park.

I wonder what the 1864 Indian was doing on top of the ground. Strange.

Maybe another detector had found it, and then lost it , you suppose.


Gary



Posted by: Larry (IL)
Date: January 24, 2008 02:24PM Moderator
Registered: 2 years ago
Posts: 1,354

I'm looking forward to the pic's Des. Hearing everything in the ground and digging everything is the only way to get everything, or at least, most of everything.



Posted by: Pap
Date: January 24, 2008 09:36AM
Registered: 2 years ago
Posts: 532

Well spoken, Larry. I really believe that masking is a bigger problem than people understand with all detectors running a fairly high level of discrimination. The program I run most of the time accepts down to -30. I will admit that I am not one who really works at locating deep (over 7 inches) coins. And I also believe that the Minelab does go somewhat deeper on silver. I have friends that use them and I know in relic hunting they do occasional hit targets that I can't reach. Or at least the response I get wouldn't necessarily cause me to stop and dig. I know there was a program or two a few years ago that opened all the VDI numbers along with some other changes that I always intended to try but never did.
Pap



Posted by: dewcon4414
Date: January 22, 2008 08:48PM
Registered: 1 year ago
Posts: 173

What I've found is if you bury a coin at 8"... say a dime by removing a chunk of soil ensuring not to disturb the ground, then because of wrap around that dime will read around -84. Put a plus in front of that and what do you think? Like the explorer coins do fall in the negative range thats also why they hunt in say -30 IM.



Posted by: RTIZONI
Date: January 22, 2008 06:51PM
Registered: 7 months ago
Posts: 32

Very good information Larry.

I noticed this some days ago and that was some of my doubts when i post a question about frequencies and asked "who decides what will be showed on the screen when using two frequencies". Since then, i start to use 15MHZ or 3MHZ, with high VDI and sensibility, and after read about the Explore users using a slow sweep, i start to set recovery and sweep speed very lower, and if the idea is to go slow i start to use 4 sometimes 5 filters and accepting from -40 to +95 keeping the hot rock rejection in around 16. That worked for me, and after being out only 3 times using this set, i could find much more good targets than i did before.
My intention was to make the DFX show me as much separation as possible in the VDI numbers i set to be accepted, even showing some of the iron, but letting me decide what is good or not.
Next Saturday after hunting i will post my pictures,i still got to find a way to take pictures with good definition.



Posted by: Larry (IL)
Date: January 22, 2008 04:29PM Moderator
Registered: 2 years ago
Posts: 1,354

Thanks for the program you used Doug. I didn't much care for the 1400 DD either. I do like the Excelerator 10X14 DD though and the 10.5 DD Excelerator is now my stock coil for the DFX due to the high mineralization I have to deal with.


Oops, you are using a DD with the DFX? N/T
Posted by: Chris(SoCenWI)
Date: January 26, 2008 11:37PM
Registered: 2 years ago
Posts: 508


Posted by: monindou
Date: January 22, 2008 03:55PM
Registered: 2 years ago
Posts: 61

Hi guys,

I used a DFX for many years, until last fall when I got an SE and gave my son my DFX. I always ran as open as I could - sometimes switching into All Metal from these settings:


Program: "Let's Rock (EEPROM DP Silver)"
"BASIC ADJUSTMENTS"
TARGET VOLUME= 63
AUDIO THRESHOLD= 15
TONE (Audio Freq.)= 231
AUDIO DISC. = ON
SILENT SEARCH= OFF
MIXED-MODE= OFF
A.C. SENSITIVITY= 82
D.C. SENSITIVITY= 60
BACKLIGHT= 0 (except at night : )
VIEWING ANGLE 25

****** Pro Options ******
"AUDIO"
RATCHET PINPOINT= OFF
S.A.T.SPEED= 7
TONE I.D.= ON
V.C.O.= ON
MODULATION= OFF

"G.E.B./TRAC"
AUTOTRAC= ON
TRAC VIEW= OFF
AUTOTRAC SPEED= 8
AUTOTRAC OFFSET=0
TRAC INHIBIT= ON
COARSE G.E.B.= AUTO
FINE G.E.B.= AUTO

"DISCRIMINATION"
DISCRIMINATION EDIT: Reject: +94 and +95
BLOCK EDIT :Reject: -95 thru -41 Accept: -40 thru +93
LEARN ACCEPT = OFF
LEARN REJECT= OFF
RECOVERY SPEED =10
BOTTLECAP REJECT=4
HOT ROCK REJECT= 0 (I've played with 10 & 20 too, those are good for super bad ground in my area)
SWEEP SPEED= 1
GROUND FILTERING = 3

"DISPLAY"
VISUAL DISCRIMINATION= ON
ICONS= ON (ya, I like icons and I wish the SE had ICONS, that would help transition to the machine)
V.D.I. SENSITIVITY= 95 (but having it set this high skews the VDI numbers, running them considerably higher which I think is important, I'll try to explain later on)
D.C. PHASE= ON
GRAPH AVERAGING= ON
GRAPH ACCUMULATE= ON
FADE RATE= 10

"PREAMP GAIN"
PREAMP GAIN= 3 (I could never go to 4, no matter how low I set AC Sensitivity so I compensated by running high AC)

"MULTI FREQUENCY METHOD"
2 FREQUENCY (Best Data)= OFF
2 FREQUENCY (Correlate)= ON
V.D.I. NORMALIZED= ON
1 FREQUENCY (3kHz)= OFF
1 FREQUENCY (15kHz)= OFF

*******************************

About the skewed VDI's caused by a high VDI Sensitivity and using a more open Discrimination pattern:

First let me say that I learned a long time ago to following the "when in doubt dig it" rule. This is important because I live in and hunt on Missouri River valley ground. Some of the places I hunt where flowing river from before the time that Lewis and Clark came through my area until the 1870's and later. It's a real tough gumbo soil, hard to dig wet or dry. And for some reason silver tends to simply "disappear" in it. I can't tell you why except to say that it's some sort of "mutant mineralization caused by thousands of years of dissolved natural salts, salient material, and decayed organic matter that in combination cause the hallo to disappear into darkness".

Knowing that some of the spots had to hold coins and relics and hunting in different DFX factory programs I started finding things little by little. So instead of goofing around changing one program for the next I started goofing around and found that upping VDI Sensitivity caused coins to go well beyond their text book range. So much by accident I triggered the "crazies" that triggered the

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