Nulling on my CTX - only in a couple lots.

[westers]

Hi all,

I'm hoping somebody can give me some tips on a nulling problem I'm having. I'm running GH's ground coin on auto sensitivity in a mineralized area. I'm having a hard time getting any target signals at all. Mostly nulls out - not overload. When it does whisper a peep, I dig and it's always something interesting.

My machine runs like a champ everywhere else and does amazing things for me. I'm hoping somebody can give me a few things to try in this troublesome location.

Thanks,
Will

 

[jas415]

Large coil or the small 6", fast sweeps or very slow, open or discrimination? If you are running a program with discrimination, then I suggest going to an open patter with no discrimination. In fact, I use the 'toggle' feature to switch between two programs, one with and one without. I use a small coil and open GH 4 tone pattern. In really, really heavy nail places I have found (comfort zone) that in the Auto + sensitivity, I feel I get almost ZERO diggable signals, as it seems the iron overwhelms all other signals. Yes I do find stuff that way but it is seldom. But switching to 'open', GH patterns, 4 tone, 6" coil, I am able to pick around things and I get quite a lot of good targets to dig. I essentially am slower that a turtle on places like that with the CTX. I tried a new F75 with the small coil and it seems to do better only in it is so darned fast it will ht EVERY target there and sound off, while the CTX seems to digest everything and find the programmed targets we are actually looking for. But the same 'cold molasses' sweep speed is required as there are so many targets.

 

[Big Boys Hobbies]

Mineralized soil is tough to detect in for sure. How fast are your sweep speed? On the CTX since it processes so much you really really have to slow down. Sounds like you could be could be swinging to fast.

 

[flysar]

I also detect in highly mineralized soil. Using A+3 sometimes I see no more than 12 Sensitivity. Regardless of settings, I've tried them all, and with an open screen I get nulling as well sometimes with a non-ferrous target number but rarely are they repeatable, if it is repeatable I dig it. I've been told by Minelab and experienced folks on here that an open screen is not all metal, only the pinpoint mode is and more than likely it is my high FE soil that is causing the nulling. Even using PP I do not hear a tone where you hear all the nulling. Slowing down and running the small coil helps but I've also found some deep 6+" silver coins with the stock coil and have accepted the fact that I can't do much about the nulling. I have tested other machines in the same area and I hear similar nulling with no additional targets found.

Here's the link to my discussion... http://www.findmall.com/read.php?86,1965431,1965431#msg-1965431

HH

 

[Digger]

As you know, nulling is caused when something under the coil is detected, but the properties are not programmed into your "accepted" list of targets. I can't comment on what target values you have discriminated out or accepted, because I build my own discrimination patterns based on the types of targets I'm hunting for, vs. the targets I don't want to dig. Ground Coin is best implemented when you are hunting in areas with high levels of mineralization because it will keep an accepted target from smearing the target icon across the display. By keeping the accepted target icon smaller, it helps to properly identify the coin. As others have mentioned, you might need to slow down your swing to allow yourself better audio separation. High Trash Separation is good at sorting out accepted targets by giving the TID indications of the strongest accepted target. Since High Trash ignores rejected ferrous and non ferrous targets, no matter how strong of signal they produce, I use quite a bit of discrimination with it. Sure, it will null out a lot. But it allows me to sweep quicker, allowing me listen for a beep while covering more ground. I also find that High Trash gives a much more stable TID when I use it in mineralized soils (compared to Low Trash or even Ground Coin). If there is a lot of trash in a mineralized site, I'd opt for High Trash. If the targets are few and far between, I'd probably use Ground Coin. JMHO HH Randy

 

[westers]

Thanks, all for the info - very thorough and incredibly helpful. My swing speed is as slow as I can get it while still moving the coil for activity to show. I've tried every swing speed down to there, so I think I can eliminate this variable.

I have been using the stock coil. I very recently bought the 17 from the awesome BigBoysHobbies, so I will likely need to wait a bit b4 springing for the 6". The small coil is definitely on my radar b/c I feel the places I'm mulling likely hold the best potential for great finds. I think most detector it's have swung a time or two and walked away. I'm determined to stick with the sites.

Digger, is there a particular program you CSM point me toward in the files available here in the forum? I've spent much of my time trying to learn as much as I can b4 fiddling a ton with my own settings. Also, beyond the forum posts, which are awesome, and the manual, are you aware of any books in print that cover the CTX particularly well?

Thanks again, all.

Will

 

[Digger]

Will, I am not aware of any books currently available, for the CTX. However, in addition to the programs Harry has provided at the top of these posts, there are quite a few programs over on the CTX Classroom (link is at the top of this forum). And using the Search function of this forum will take you to anwers to specific applications and questions. There are a lot of well-versed CTX users on this forum who have spent thousands of hours using their CTX's and helping others better understand what makes it tick.
As I've said many times in the past.....there isn't any magic formula for setting up your CTX. With the variance in ground mineralization levels, the differences in the types of targets we might be searching for, the types of "trash" that is likely adjacent to those targets, the targets we want to ignore, our individual styles of hunting, the number of tones we want to hear, the number of bins we want to have the CTX analyze, one group of settings that I would recommend as being able to maximize the potential of your CTX in your sites would be misleading, at best. I'm not trying to avoid the questions you have, but I honeslty believe that taking a stock program and setting the Patterns to accept and/or Reject the targets we desire, setting for the types of tones we want to hear (Fe or non-FE), setting the number of tones we want to audibly decipher, setting the Sensitivity at Auto without an offset, let the CTX ignore the effect of the mineralization (without enabling GB) and practicing with some familiar targets is the best way to learn. I highly recommend building a coin garden in your backyard, to practice in. Toss down some coins and the types of "trash" you might encounter in a hunt. Sweep over the targets at varying speeds, to see how quicly you and your CTX react. Listen for the subtle differences between the tones of flat coins and coins on edge, or the differences in how an adjacent target can disguise the target tones. Learn how to pinpoint a target to improve your separation skills. After you've become familiar with what is provided in those settings, change things up to better suit your particular needs. Maybe you will do better with fewer tones....maybe more tones. Maybe you'd like 50 tone Conductive better than Combined? If you seem to be getting along well and want to run a little "hotter", try using Auto + on the Sensitivity, to improve your depth of detection. If your sites are highly mineralized and you are getting a lot of falsing, you may even have to lower the Sensitivity with Auto - . As I said, the combinations are endless. But trying different settings and combinations of settings will eventually get you to where you want to be. JMHO HH Randy