Detecting "exercise" was eye-opening...now what?

[TrpnBils]

I was reading this article on Detecting365 this morning and decided to try this little exercise because I find that most of my coins, even with my etrac and now my 3030 are coming at no more than about 6" deep: http://detecting365.com/exercise-china/

If you don't want to read it, essentially what it says to try doing is this:

1. Dig a deep hole in a clean patch of ground
2. Place a target at the bottom at a measured depth (suggested is a silver dime, 3 ringer, etc)
3. Cover and see if you can find it.
4. If not, mess with the depth until you can start to get a signal and adjust settings to see if you can clean it up at all

Really the idea here is to see what we can do to get a little extra depth or at least interpret a deep, iffy signal that we KNOW is good a little better.

Anyway, the author says that he's hitting a silver dime at 8" pretty easily with an Etrac and an F75. I KNOW that people say new test gardens, air testing, and all that sort of thing don't give you the depth that a long-buried coin will, but hear me out. Full disclosure: I have never built or used a test garden before but I have been detecting for about 10 years or so, so I have nothing to compare this to. So I dug my hole to 9", stuck a clad Rosie in there (and later replaced with a Merc...same results for both). Coin was in there flat. My recommended sensitivity was 18 and I was running auto+3. I couldn't even begin to hear anything at all at 9". I brought it back up to 6" and got nothing. I brought it up to 4" and got a muddy signal finally. Again, I get that I will lose SOME depth on a fresh bury, but even the author of that article is saying he's hitting at 8" on a fresh bury. As I mentioned before though, most of my finds come from no deeper than about 4-6".

Things I tried (one at a time, each time returning to my default settings) to gain depth without luck:

• Jack up sensitivity (even manual 30 didn't hit it but it was so noisy I might have and not known it)
• Wide open screen (even with discrimination there was only very minimal)
• all four audio options
• High trash, low trash, ground-coin, ferrous-coin
• ground balance
• noise cancel
• manually move through every channel

What the heck is going on here? Shouldn't I be hitting stuff deeper than this? It really makes me question everything I thought I knew about this detector in the field....

 

[trojdor]

If your auto+3 sens was 18, then you've got some moderately problematic ground....and/or some potent EMI.
People with clean ground have no idea how much either hurts both depth and ID.

Regardless of what some author states in his on-line article, you really can't compare operation and/or performance in your ground with anyone else in the world.
Well...maybe with the guy standing next to you...or you next door neighbor.

Combine that with the fact that Minelabs do not like fresh buries...at all...and that sounds about right for your test.

You say you're limited to around 6" target depths in actual coin recoveries...(that shows you how much a fresh bury loses in your ground)
I know lots of guys in certain areas of Colorado and New Mexico who say the same thing...that they also feel limited to the 6" (ish) depth in much of our dry mineralized ground.

Shoot, I know of a couple areas that many machines have trouble with a coin on top of the ground...with dirt so red you'd think you were in OZ.

Still, if you feel that something might be wrong, find a fellow digger in your 'neck of the woods' (especially if he swings a CTX), and go compare signals.
I think you'll probably find he's getting similar depths in similar soil. If not, you might try a different coil to see if there's a problem...

Just out of curiosity, what part of the country do you live in and hunt?

HH,
mike

 

[TrpnBils]

It was suggested by somebody else that maybe my connection isn't tight. I know for a fact it isn't because I only screw it in 2 or 3 turns so it's held in place. I never thought that might have an impact on depth. I am going to try that and see what happens. Also contacted a friend of mine who is a detector dealer and we are going to compare 3030s on Monday if this doesn't get better by then.

I'm in the eastern panhandle of WV, by the way!

 

[trojdor]

It was suggested by somebody else that maybe my connection isn't tight. I know for a fact it isn't because I only screw it in 2 or 3 turns so it's held in place. I never thought that might have an impact on depth. I am going to try that and see what happens. Also contacted a friend of mine who is a detector dealer and we are going to compare 3030s on Monday if this doesn't get better by then.

I'm in the eastern panhandle of WV, by the way!

Sound like a good plan...let us know what you find out!


mike

 

[TrpnBils]

Went out in the dark to try this out because it would drive me nuts all night if I didn't. I got slightly better results, but I'm still not totally convinced.

One thing I am noticing though... if it is working right and I'm getting the appropriate "marginal" signals for the edge of detection, I'm not digging a whole lot of what I should be digging. At the edge of detection here the merc was ringing in at 12-35. I know the Etrac was a little unstable with FE numbers, but I thought the 3030 was better at it. I don't care either way, just as long as I know what to look for!

 

[trojdor]

One thing I am noticing though... if it is working right and I'm getting the appropriate "marginal" signals for the edge of detection, I'm not digging a whole lot of what I should be digging. At the edge of detection here the merc was ringing in at 12-35. I know the Etrac was a little unstable with FE numbers, but I thought the 3030 was better at it. I don't care either way, just as long as I know what to look for!

I'm going to let you in on a secret about the CTX...

If you're still getting ANY stable, repeatable ID numbers, that's not an 'iffy' signal... ...you're still not nearly deep enough...

It's not an 'iffy' signal until the ID jumps all over the place in what (at first glance) looks like completely random junk noise.
This effect happens earlier/worse in mineralized ground like you and I have.

Many times you'll get a tone without ANY ID, and any ID presented can appear to jump all over.
When you get a signal like that, slow WAY down...shorten your swing to just an inch or two...and watch the bouncing ID cursor/numbers....ALONG WITH THE DEPTH NUMBERS.
Note that the depth numbers stay stable and accurate long after the TID numbers try to 'jump ship'.

(BTW, once you've experimented in your ground, you should learn what represent coin size objects at 'iffy' depths.
For me, in my ground, these iffy signals typically start at around 7.5 - 8 inches.
If I get the same iffy signals at some other extreme...say 4 inches or 13 inches...target probably not coin sized.)

Circle the target to see if you can clear up the signal any.
Try to imagine a really bad pistol shot trying to hit a bulls-eye. The shots will be all over the target, but if you keep looking closely, they'll start to form a general pattern as to where they're trying to hit.
The 'iffy' CTX signals are the same way on the CTX screen. (Of course, target trace is ON to help with this 'screen visualization' as much as possible.)

For instance, if the target cursor/FE numbers cluster near the bottom half of the screen...probably iron. If FE occasionally jumps well over the 12 line as well as under...probably non-ferrous.
If the target cursor/CO numbers tend to generally hit/cluster near the right-hand half of the screen, probably a high conductor, towards the middle/left...a low conductor.
Every now and then even a bad marksman hits the bulls-eye. Iffy signals are the same way. Every now and then you might get something like a nice 12:42 13:45 back to back for a couple of swings.
If that happens, stop and dig now...before that silver dime gets away.

It requires lots of practice, time, and patience...just like playing a musical instrument...but after you've put in the time, you can start to get some serious extra depth out of your machine.

One thing you do need to realize with those 'just out of range' numbers, is that sometimes the best you can do is to classify the really deep target as probably either ferrous or non ferrous.
This is not an entirely bad thing, as really deep non-ferrous targets are unlikely to be modern trash. I've yet to dig a pull tab at 12", for instance.
It's more likely to be coins that other hunters have simply missed.

I suggest you experiment with the different separation modes in your ground to see which gives you the best depth and ID info at depth.
In my ground I get the best depth and ID with High Trash, but that means nothing unless you're going to hunt along side me...test your ground for the best settings.

Finally, you can supplement this technique with the excellent Pinpoint Trace/Lock hunting mode that has been discussed here before.

Hope this helps, and wasn't too painfully long to read...

mike

 

[TrpnBils]

Mike - thanks for the excellent read! I would rather read a dozen in-depth, lengthy responses like that than see pictures of what everybody's finding....that really helps in my understanding of it and helps me improve. I think it's interesting...I had my Etrac for about 2.5yrs before I sold it and got this 3030. I was really good (IMO anyway) with it and knew how to address the subtleties of what it was telling me. I have only had the 3030 since February/March and although I knew it was a different detector, I never expected the learning curve to be this high based on what I knew from the Etrac. I still feel like I'm throwing a hail mary every time I go out because I feel like I'm only confident in digging the best, clearest signals. For example, while I was reading your response there I was thinking about some of what I see on my screen with target trace. I have noticed there are a lot of signals that, if I was going on audio alone (i.e. using my Etrac) I would have dug. With target trace on though, I have not dug certain signals that sounded decent but had a lot of "splatter" on the screen. I remember reading several times that "splatter" indicated dispersed rust, so I'd move on in search of something more clear. Wonder what I've been passing over!? I'm kind of tempted to turn trace off for awhile to see how it goes.

Right around when I switched to the 3030, a good friend of mine went from the AT Pro to an Etrac because he had seen how well I was doing with it. I've been working with him on it but I was telling him the other day there's certain things that I can't really explain about how to interpret signals and that it's just something you have to "see for yourself". I can think of two major times with my Etrac that were serious "a ha" moments for me where it completely changed how I looked at situations or signals. I have yet to have one of those moments with my 3030 (granted, my hunting time is maybe 1/3 of what it was last year - my son was born in November. Now I just have to get him interested when he gets older so we can go together!)

Anyway - I wanted to ask you...you mentioned the "pinpoint trace/lock hunting mode that has been discussed here before". Are you talking about the videos that sube has been posting where he's getting poor trace marks until he uses pinpoint mode? If not, could you link something so I can see what you're talking about? I've read through about two years' worth of stuff on here since getting my 3030 so I'm sure I've seen it, just not sure I'm thinking of the same thing you're talking about!

Thanks again!

 

[Johnnyanglo]

="What the heck is going on here? Shouldn't I be hitting stuff deeper than this? It really makes me question everything I thought I knew about this detector in the field...."

Your results are the reason why having a test garden is so important to finding the truth. You can listen to second-hand stories or get the answer for yourself.
In Washington State dirt a buried dime is gone at 7" and no repeatable audio beyond 5.0" in AUTO+3 with the CTX and E-Trac.

In the same dirt a buried dime is fringe at 7" with occasional hits every 2-3 coil passes in MAN-30 with the CTX and E-Trac. At 6.5" the dime is almost diggable.
So, to reliably get a dime in Auto+3 keep the dime buried less than 5.5". To reliably get a dime in MAN-30, keep the dime buried less than 6.5".

If you watch the cursor, a dime signal will begin to jump about deeper than 4.5" ... such as, 11-45 to 01-33 to 11-37 to 01-44. But the general area of jumpiness is within the non-ferrous zone; this is your clue to dig even when at the same time the audio is blanking on every third pass - the TID is hinting the target is non-ferrous. So dig it.

It is also worth mentioning that the CTX-3030 and E-Trac behave very similarly - their sensitivity is nearly identical (as is there related depth capability).

It is interesting to note that while MAN-30 gives perhaps a 15-20% increase in depth in the dirt, you can go even deeper All-Metal Pinpoint. That is, where AUTO+3 has checked out at 6.5" on a buried dime (random audio hits) the AM PinPoint easily centers the audio over the target. Granted in All-Metal there is no ferrous/non-ferrous discrimination, but remember the TID cursor is probably jumping around in the non-ferrous zone if it's a coin (that's your clue). If you have a fringe signal switching temporarily to Pinpoint can help center the target as it is another 15-20% deeper than even MAN-30.

Now that is in slightly mineralized Washington soil. The FBS detectors will show greater detectable distance in the air than the ground, even getting more than 12" in MAN-25 and 7.5" in AUTO+3 on the same dime. Yes, AUTO+3 cuts detectable distance by nearly 40% as compared to MAN-25+. That shouldn't be shocking. AUTO sensitivity is a happy medium of averaged signal processing to ensure stability. You get easy detecting without the sharp blips and crackles of MANUAL, but at a price.

But when you compare AUTO to MANUAL in the soil, the difference drops to half that of the in-air distances, in other words the difference in capability is less dramatic thanks to the overpowering effects of soil minerals. If you want to get an extra bit of depth, switch to MANUAL, but if ear fatigue is bothersome go back to AUTO. You'll be losing 15-20% of the total depth capability but you'll be keeping your sanity.

The chart below shows the affect each change in MANUAL and AUTO sensitivity has on target detectability in air. If you use AUTO+3 regularly it is if you were hunting in MAN-14 (the max is MAN-30). Again, in the soil the difference isn't that dramatic, but still has impact on depth.

You'll notice that the reduction/increase in sensitivity with each MANUAL adjustment is linear. The actual forumula would be:

[pre] Max Depth = 0.3945*(MAN Value) + 2.187 [/pre]

Which means the slope is about 40/100 or 40%, every 1 change in MANUAL value yields 0.25" depth increase (in the air). That is, if you go from MAN-15 to MAN-19 (a change of 4 values) you get 1" more depth. If you go from MAN-20 to MAN-30, a change of 10, you get 10 x 0.25" = 2.5" more depth (in the air). Assuming bad soil it is more likely that in the ground any change would be about 15-20% less variable. So, from MAN-20 to MAN-30 you might get you 2.0" more depth (in the ground) instead of 2.5".

Recall that a buried dime in MAN-30 is maxed out at about 7.0", so dropping to MAN-20 might put you around the 5.0" depth mark, depending on your soil conditions.

You'll be happy to know that the rate of change in AUTO is about the same, 0.25" per AUTO value. Over the range of 6 values (-3 to +3) the change of 6 x 0.25 = 1.5" change. In other words, AUTO+3 changed to AUTO-3 will drop your depth in the air by 1.5". Knowing that AUTO+3 is like using MAN-14, then dropping to AUTO-3 is like using MAN-10 or so, where the dime in air is maxed out at 6.0" instead of 7.5" at AUTO+3.

What have we learned? If you want to exceed the capabilities of AUTO+3 use MAN-15 or higher, then you'll get more depth. From MAN-15 to MAN-30 (the max) you'll gain almost 4" in depth in the air and perhaps 3" in the ground.

Anything else? Well, if you're looking for that Rosie dime in moderately mineralized soil, and you know it has sunk deep, say at least 6.5" down, then AUTO+3 will miss the target about 80% of the time and will miss it 95% of the time at 7.0" down (that's if you use audio alone ... the TID may hint its location down to 7.0", even when the audio is silent as described above).

If you want to go deeper, get a bigger coil or change to a single freq VLF detector. Can you get a dime deeper than 7.0 inches? Yes, if your soil is more mild, but probably the increase won't be identical to air (12"), perhaps in coral sand you can get near 12" but for most of us clean soil is probably maxed out at 10" or so on a dime. So, forget about getting any dime-sized target in moderately mineralized soils deeper than 6.0" without being extra slow, extra careful, watching the display, listening for the occasional tone every third sweep (non-repeatable), and keeping the DD coil centered for max depth while using MAN-30 (and no Discrimination - nope, none at all or all bets are off).

Hope this helps you find those deep coins,

Johnnyanglo

 

[trojdor]

Mike - Anyway - I wanted to ask you...you mentioned the "pinpoint trace/lock hunting mode that has been discussed here before". Are you talking about the videos that sube has been posting where he's getting poor trace marks until he uses pinpoint mode? If not, could you link something so I can see what you're talking about? I've read through about two years' worth of stuff on here since getting my 3030 so I'm sure I've seen it, just not sure I'm thinking of the same thing you're talking about!

Thanks again!

Sorry it took so long to respond...weather has been perfect for hunting (which is rare around here in the summer).

Jonnyanglo alluded to it in his well-reasoned response to your OP, when he mentioned going even deeper in the All-Metal Pinpoint mode.

Firstly, make sure the Target Trace Pinpoint option is enabled...(note that is separate from your basic Target Trace option)
Then make sure 'pinpoint lock' option is enabled.
With the coil held at roughly your swing height, click the pinpoint button to lock into pinpoint mode. (Clicking again when done exits from pinpoint mode)

Not only is the audio now All-Metal, Non-Motion...your screen still gives you target ID info...with trace info.
Sort of a deep non-motion, Visually Discriminating mode. Lot's of guys use this trick to squeeze every bit of depth from the CTX...but note that you'll hear every little piece of metal in the ground. (no audio disc)
Same rules of watching where the iffy signals want to group on the screen.

Now, if you're in serious mineralization...like I am...you will notice that the height above the ground you hold the coil will affect the threshold tone you get when you lock into pinpoint mode.
This is because the CTX does a 'ground grab' when you pinpoint. This can cause an annoying threshold shift as you lower/raise the coil.
If there's too much (or too little) threshold, just click off and click on at a slightly different height above the ground until it's satisfactory.

If it's really bad, one thing you can do to help eliminate the pinpoint threshold shift, is to turn on GB and carefully/precisely ground balance.
That will eliminate the ground/tone shift when you lock pinpoint.
However...You've got to be very, very precise when ground balancing though...as if you're off (even a little) it will adversely affect depth.

I check to see I've got it right (after balancing), by first locking pinpoint on the (clean) ground and listening for a change while I raise the coil...
...then quick off/on while holding the coil a foot or two off the ground, and listening while I lower the coil.
If there's any tone change, re-do the balance until there's not.

You know you've got it right when you can hear multiple faint signals every pass of the coil.
(One other interesting thing to note, is that even if you now turn GB back off, at this point the threshold shift effect still won't be as bad as it was before you GB'd.)

Another slight oddity to the CTX, is if you do a noise cancel after GB, it tends to throw the GB off, and you'll need to redo it.

Good luck, and post pics of those deep, old coins you find.

mike

 

[jas415]

It would be nice to be able to set up two patterns, using the 'toggle', with a primary pattern for searching, and a backup for maybe a 'confirmation pattern' for deep iffy signals.

 

[GKMan]

Terrific thread! The knowledgebase here is outstanding. This morning after reading this thread I decided to go out and as I have always called it "run full bore" which is at 30 manual sensitivity but in this case I kept a closer eye on my conductive ID.
I went back to a place that I have detected many times and have found five Connecticut coppers previously along with my 3500 - 5000 year old copper adze. Yes, it is a pretty awesome place to detect. I found an Indian Head but I can't attribute that to anything with regards to this thread here. But then I ended up recovering a 1723 King George I coin. It was a ttarget that I may normally pass by, but the conductive looks pretty stable to me and so I dug it. It really paid off.

Johnny I really appreciate that graph. I have known for a long time how powerful using manual sensitivity is. But after awhile it gets tough trying to deal with the snap crackles and pops running such a hot machine. Without this thread today I wouldn't have been running the way I was so big thanks to everyone..
[attachment 332946 FB_IMG_1467652883437.jpg]

 

[Johnnyanglo]

="Johnny I really appreciate that graph. I have known for a long time how powerful using manual sensitivity is. But after awhile it gets tough trying to deal with the snap crackles and pops running such a hot machine"

For those who don't regularly use manual sensitivity the audio reactivity can be bothersome, as you said, and that deficit can prevent some detectorists from escaping the relative tranquility of AUTO+3.

One method is to sweep through a likely target rich area in AUTO+3 and clean out the low-hanging target fruit. Then, the next visit, use MAN-30, or whatever sensitivity level the reactive soil will allow via the popping audio that you can withstand. If you are sure the deep stuff is valuable, the last step would be to remove the unwanted ferrous from a gridded area, as the nails and elongated iron are going to silently mask the deeper non-ferrous (without making an audio peep), you'll never even know the non-ferrous is hidden next to the ferrous. But that takes quite a bit of labor - but if you know there may be deep silver coins and you want the best opportunity at recovery then that's the approach to take.

On the other hand, for those looking for freshly dropped coins in a park or recent jewelry losses at the beach, then AUTO+3 will find most of it adequately with a lot less audio confusion.

 

[trojdor]

Terrific thread! The knowledgebase here is outstanding. This morning after reading this thread I decided to go out... ended up recovering a 1723 King George I coin. It was a target that I may normally pass by, but the conductive looks pretty stable to me and so I dug it. It really paid off.
]

Sweet !

Anything that old around here is made of stone...

mike

 

[TrpnBils]

="What the heck is going on here? Shouldn't I be hitting stuff deeper than this? It really makes me question everything I thought I knew about this detector in the field...."

Your results are the reason why having a test garden is so important to finding the truth. You can listen to second-hand stories or get the answer for yourself.
In Washington State dirt a buried dime is gone at 7" and no repeatable audio beyond 5.0" in AUTO+3 with the CTX and E-Trac.

In the same dirt a buried dime is fringe at 7" with occasional hits every 2-3 coil passes in MAN-30 with the CTX and E-Trac. At 6.5" the dime is almost diggable.
So, to reliably get a dime in Auto+3 keep the dime buried less than 5.5". To reliably get a dime in MAN-30, keep the dime buried less than 6.5".

If you watch the cursor, a dime signal will begin to jump about deeper than 4.5" ... such as, 11-45 to 01-33 to 11-37 to 01-44. But the general area of jumpiness is within the non-ferrous zone; this is your clue to dig even when at the same time the audio is blanking on every third pass - the TID is hinting the target is non-ferrous. So dig it.

It is also worth mentioning that the CTX-3030 and E-Trac behave very similarly - their sensitivity is nearly identical (as is there related depth capability).

It is interesting to note that while MAN-30 gives perhaps a 15-20% increase in depth in the dirt, you can go even deeper All-Metal Pinpoint. That is, where AUTO+3 has checked out at 6.5" on a buried dime (random audio hits) the AM PinPoint easily centers the audio over the target. Granted in All-Metal there is no ferrous/non-ferrous discrimination, but remember the TID cursor is probably jumping around in the non-ferrous zone if it's a coin (that's your clue). If you have a fringe signal switching temporarily to Pinpoint can help center the target as it is another 15-20% deeper than even MAN-30.

Now that is in slightly mineralized Washington soil. The FBS detectors will show greater detectable distance in the air than the ground, even getting more than 12" in MAN-25 and 7.5" in AUTO+3 on the same dime. Yes, AUTO+3 cuts detectable distance by nearly 40% as compared to MAN-25+. That shouldn't be shocking. AUTO sensitivity is a happy medium of averaged signal processing to ensure stability. You get easy detecting without the sharp blips and crackles of MANUAL, but at a price.

But when you compare AUTO to MANUAL in the soil, the difference drops to half that of the in-air distances, in other words the difference in capability is less dramatic thanks to the overpowering effects of soil minerals. If you want to get an extra bit of depth, switch to MANUAL, but if ear fatigue is bothersome go back to AUTO. You'll be losing 15-20% of the total depth capability but you'll be keeping your sanity.

The chart below shows the affect each change in MANUAL and AUTO sensitivity has on target detectability in air. If you use AUTO+3 regularly it is if you were hunting in MAN-14 (the max is MAN-30). Again, in the soil the difference isn't that dramatic, but still has impact on depth.

You'll notice that the reduction/increase in sensitivity with each MANUAL adjustment is linear. The actual forumula would be:

[pre] Max Depth = 0.3945*(MAN Value) + 2.187 [/pre]

Which means the slope is about 40/100 or 40%, every 1 change in MANUAL value yields 0.25" depth increase (in the air). That is, if you go from MAN-15 to MAN-19 (a change of 4 values) you get 1" more depth. If you go from MAN-20 to MAN-30, a change of 10, you get 10 x 0.25" = 2.5" more depth (in the air). Assuming bad soil it is more likely that in the ground any change would be about 15-20% less variable. So, from MAN-20 to MAN-30 you might get you 2.0" more depth (in the ground) instead of 2.5".

Recall that a buried dime in MAN-30 is maxed out at about 7.0", so dropping to MAN-20 might put you around the 5.0" depth mark, depending on your soil conditions.

You'll be happy to know that the rate of change in AUTO is about the same, 0.25" per AUTO value. Over the range of 6 values (-3 to +3) the change of 6 x 0.25 = 1.5" change. In other words, AUTO+3 changed to AUTO-3 will drop your depth in the air by 1.5". Knowing that AUTO+3 is like using MAN-14, then dropping to AUTO-3 is like using MAN-10 or so, where the dime in air is maxed out at 6.0" instead of 7.5" at AUTO+3.

What have we learned? If you want to exceed the capabilities of AUTO+3 use MAN-15 or higher, then you'll get more depth. From MAN-15 to MAN-30 (the max) you'll gain almost 4" in depth in the air and perhaps 3" in the ground.

Anything else? Well, if you're looking for that Rosie dime in moderately mineralized soil, and you know it has sunk deep, say at least 6.5" down, then AUTO+3 will miss the target about 80% of the time and will miss it 95% of the time at 7.0" down (that's if you use audio alone ... the TID may hint its location down to 7.0", even when the audio is silent as described above).

If you want to go deeper, get a bigger coil or change to a single freq VLF detector. Can you get a dime deeper than 7.0 inches? Yes, if your soil is more mild, but probably the increase won't be identical to air (12"), perhaps in coral sand you can get near 12" but for most of us clean soil is probably maxed out at 10" or so on a dime. So, forget about getting any dime-sized target in moderately mineralized soils deeper than 6.0" without being extra slow, extra careful, watching the display, listening for the occasional tone every third sweep (non-repeatable), and keeping the DD coil centered for max depth while using MAN-30 (and no Discrimination - nope, none at all or all bets are off).

Hope this helps you find those deep coins,

Johnnyanglo

Quite a trove of information here! Thank you for the effort you put into shedding some light on this - I appreciate it a lot!

That graph is revealing. I knew with the Etrac a manual number was more sensitive than an auto number of the same value, but I hadn't read that specifically about the 3030 until now. It makes sense, given that the auto numbers are an average as you mentioned. I think my problem is I just need to learn how to interpret fringe signals better. For that matter, I need to learn how to interpret mixed signals better. I've basically been ignoring anything with a "smear" on target trace figuring that it was rust. The other night though, in a clean patch of ground, that dime was definitely coming up with a notable smear on the screen.

One other thing I'm wondering about... I was able to compare this to another 3030 today and saw the same thing so I know it's not just mine. With the Etrac, it was well established that the deeper a coin went the higher the FE numbers went but that was supposedly fixed with the 3030. At fringe depths both last week and again today in two different locations (counties apart) the conductive numbers went way down. It's been mentioned in here that numbers will fluctuate at the fringe, but it was pretty solidly sticking in the low 30s. Is that typical?

 

[TrpnBils]

However...You've got to be very, very precise when ground balancing though...as if you're off (even a little) it will adversely affect depth.

I check to see I've got it right (after balancing), by first locking pinpoint on the (clean) ground and listening for a change while I raise the coil...
...then quick off/on while holding the coil a foot or two off the ground, and listening while I lower the coil.
If there's any tone change, re-do the balance until there's not.

You know you've got it right when you can hear multiple faint signals every pass of the coil.
(One other interesting thing to note, is that even if you now turn GB back off, at this point the threshold shift effect still won't be as bad as it was before you GB'd.)

Another slight oddity to the CTX, is if you do a noise cancel after GB, it tends to throw the GB off, and you'll need to redo it.

Good luck, and post pics of those deep, old coins you find.

mike

Regarding ground balance, I don't see that discussed too much about the 3030. Even though it has the option, I usually see people just suggesting that it gets left off. You said yourself here that if it's not done right you can actually lose depth. Do you ground balance AND noise cancel at every site? I generally noise cancel at least once at each site, but almost never ground balance unless the soil is particularly bad, but maybe I should start.

As far as doing the balancing right to avoid losing depth, is that just a matter of using the double-check of seeing if the threshold changes after balancing that you mentioned above?

 

[TrpnBils]

It would be nice to be able to set up two patterns, using the 'toggle', with a primary pattern for searching, and a backup for maybe a 'confirmation pattern' for deep iffy signals.

If you did this, what would your "confirmation" screen look like? I use minimal discrimination as it is....use wide open as confirmation or something else?

 

[trojdor]

Regarding ground balance, I don't see that discussed too much about the 3030. Even though it has the option, I usually see people just suggesting that it gets left off. You said yourself here that if it's not done right you can actually lose depth. Do you ground balance AND noise cancel at every site? I generally noise cancel at least once at each site, but almost never ground balance unless the soil is particularly bad, but maybe I should start.

As far as doing the balancing right to avoid losing depth, is that just a matter of using the double-check of seeing if the threshold changes after balancing that you mentioned above?

"I usually see people just suggesting that it gets left off. You said yourself here that if it's not done right you can actually lose depth."
And that's exactly why most people say to leave it off.

"Do you ground balance AND noise cancel at every site? "
No. I do always NC. (Sometimes multiple times in bad EMI.)
I frequently GB...especially if the ground is particularly bad. (But not always.)
However, I will also turn off GB after I've used it for a while to see how the detector is responding.
If it's acting 'nicer' after GB-ing for a while, I'll leave it off.

GB on the CTX is sort of a 'red-headed step-child'. (Apologies to any real or imagined red-headed step-children.)

GB was implemented in a less than optimum fashion;
1. It doesn't track the ground, so you've got to manually adjust it frequently if your ground changes.
2. Since you're usually using it to go deep, unfortunately the GB is more touchy when Sense numbers are high.
3. The actually process of calibration (raising and lowering the coil) doesn't always work properly...the algorithm seems to not be optimized.
4. Noise cancel can completely 'bork' the GB...forcing you to redo.
5. And finally, it seems to drift a little all on it's own...regardless of conditions.

Now that I've completely bad-mouthed it, it does help considerably when hunting in the pinpoint mode...as I explained in detail in the previous post.
So as quirky as it is...it's still a heck of a lot better than not having it.

And to answer your last question...yes, listen for any threshold change...however slight...in either direction (up or down). And be sure to check it occasionally if you leave it on for any length of time.

Finally...in general...
1. If you don't have bad ground...leave it off.
2. If you don't want the hassle of 'baby-sitting' it...leave it off.
3. If you don't do much with pinpoint mode...leave if off.
4. If you're not sure you need it...leave it off.

BUT,
If you want to squeeze the very most out of the CTX in mineralized ground...especially when hunting in pinpoint mode...use GB and learn it's quirky behavior.

HH,
mike

 

[Johnnyanglo]

My mileage on Ground Balance testing for the CTX was that it was way to easy to skew the algorithms by a bad GB, even though you are following the CTX manual exactly. I usually only made things worse - much worse, dramatically bad in fact.

There are no flashing lights that tell you that you've ruined your ground balance, you just silently lose depth and sensitivity. Unlike VLF machines which measure ground minerals differently, under most circumstances you are wrong to GB the CTX. But if you feel it is warranted, I'd suggest first burying a test target with known recovery signature and then double-checking audio/TID after GBing that indeed you can still obtain it at depth, just to be sure.

 

[TrpnBils]

Man....sure seems like a sketchy feature!

 

[Johnnyanglo]

"If you did this, what would your \"confirmation\" screen look like?"

I would recommend absolutely that two screen should be set, and toggle between them as needed. But when talking about "deep, iffy" targets and discriminated bins the rule would be less is better, meaning less discrimination is the goal. Think of discrimination as needing a determinate, a decision is made by the machine (a not particularly smart machine either). The determination requires shunting the raw data into different channels to conduct several comparison tests within the software. The determination will be whether to produce an audio beep or be silent. With weak signals the noise level is already high, ferrous minerals predominate, and the likelihood the algorithms will simply eliminate the weak target signal entirely looms large. If that happens, you walk unknowingly by what otherwise would be a deep, iffy signal with an open screen

So, the advantage is in your favor NOT to use ANY discrimination AT ALL when hunting deep targets (or small, shallow targets, really any target that produces a weak signal against, say, a mineralized soil matrix or iron strewn fields of nails).

Therefore, I'd have one screen pattern set to Open (no Disc) for that weak target and the other set to eliminate whatever bothers you most (perhaps high-tone blips from nails or disc set to eliminate all but to cherry-pick shallow coins, for example). But realize that in doing so you are losing some margin of depth/sensitivity, which is fine as long as you are aware of it and consciously choosing to do so.