Tweaking the GB for a tad more depth.

[KurtB]

I have a couple of spots that the 3 kHz coil has found me some nice old coins. I don't think the amount of trash will allow me to use a larger coil effectively. Could you explain how to tweak the ground balance to gain a little more depth? I have read that it can be done and I would like to try it. Do you adjust up or down on the scale? I guess that maybe a little GB lesson might be needed. In my area I usually GB around 32-40. Thanks to any that might be able to help.

 

[rifleman]

Some people like to set the ground balance a little on the positive side. I usually just ground balance to try and get the tones as even as possible. A correctly ground balanced detector allows the detector to not see the mineralization of the ground, kind of making the ground somewhat invisible to the detector. When your detector is balanced correctly for the ground you are hunting in, you will find the deeper targets because the ground is not masking them. When I am hunting in areas without a lot of trash, I ground balance and then put the detector in auto GB mode. This way as the ground changes, the detector compensates for it. I turn the auto GB off when X-ing over a target. In area with a lot of trash, I find a clear area and GB the machine, then GB it every 15 minutes or so. The FAQFAQ section explains GB pretty darn good. Re read it if you have not looked at it for a while. I printed out all the info in the FAQFAQ section and put it in a binder. I re read it from time to time just to remind me of the correct way of doing things and to refresh my memory in case I start hunting an area that is different than where I usually go. Nugget hunting is a good example, I don't get to the gold fields too often, so a re read is in order before I head out to the field.

Good hunting, John K

 

[sport.pilot]

John,

Are you saying you leave your detector in the GB mode while hunting or did you mean you put it in tracking mode (which is really a continuous auto GB as I understand it) and then hunt? Thanks.

Darryl

 

[rifleman]

I meant that I put it in tracking mode when hunting. If there is a great deal of junk, I ground balance and leave the tracking mode off. In tracking mode, the detector tracks the difference in the mineralization of the ground and adjusts the GB automatically. When there is a lot of junk, I believe that it can cause problems in the auto track mode, that's why I leave the auto track off in those type of areas. If you are continuously swinging over one target trying to see if it looks like one worth digging, turn the auto track off. The auto track can and will null out your target if left in that mode while swinging the coil repeatably over one target.

Good hunting, John K

 

[KurtB]

So if I GB at 35 and want it on the positive side, all I have to do is set it at 37 or 38? Or would it be 33 or 32? Thanks for your help.

 

[Digger]

Ground Balance is basically the detector's ability to compensate for the adverse effects of the ground. The numbers represented by setting the GB do not really represent the actual mineralization of the ground. They might better be thought of as a pre-established number, representing the ground phase required by the X-70 to compensate for the effects of mineralization. The most positive GB setting on the X-Terra 70 is the setting of 1. And, this represents the most highly mineralized ground compensation setting achievable by the X-Terra 70. As the ground phase levels decrease, you will be able to use less-positive GB settings up to a point you might reach the least positive GB setting of 90. I think of properly setting the Ground Balance as the most basic form of discrimination in that the GB setting "discriminates" out the ground effects. Your job in setting your GB is to neutralize (balance) the effects of that mineralization. It is a bit confusing in that the words used to describe mineralization and GB settings seem opposite of what you would expect. A setting of 1 is the most positive GB setting you can have with the X-Terra 70. And, the more mineralized the ground, the more positive setting you will need. A setting of 90 is the least positive GB setting of the X-70. And, the lower the mineralization, the less positive setting you will need. So, as mineralization increases, a more positive GB setting (lower X-Terra GB number) will be required to neutralize it. And, as the mineralization decreases, a less positive GB setting (a higher X-Terra GB number) will be required to neutralize the lower mineralized soil.

I like to tweak the GB a bit positive. That means that I am changing the GB setting so that the detector thinks there is less mineralization in the soil than the Automatic GB told it there was. To me, it makes the X-70 more responsive to deep targets and seems to be more sensitive to small ones as well. To do this, I will use Auto GB, then go to manual GB and press the - button a couple times.


Here are links to a few posts I've made in the past, concerning GB and why I like to run my X-70 a bit "positive".

http://www.findmall.com/read.php?55,516096,516258#msg-516258

http://www.findmall.com/read.php?55,581121,581135#msg-581135

http://www.findmall.com/read.php?55,557122,557179#msg-557179

http://www.findmall.com/read.php?55,554084,554386#msg-554386


JMHO HH Randy

 

[KurtB]

Thanks Digger. That is exactly what I was looking for. I thought I remembered it seeming backwards or something. Got it now. Thanks again.

 

[sport.pilot]

Kurt,

I have hunted for gold nuggets for years with a Gold Bug 2 - in my opinion, the finest and most sensitive small nugget machine around, bar none. I have hunted with the X-70 for gold nuggets and meteorites in AZ, with good success as well. I generally hunt a small area with the small 6 inch DD coil. Although I have the larger elliptical coil, the smaller coil is more sensitive to small gold nuggets. If I find small nuggets, I then go back over the area with the elliptical coil hoping for larger ones. If I have time, I take out my Minelab GP Extreme and use my 16 inch Nugetfinder coil in search of a deeper larger nugget. When using the Gold Bug 2 or the X-terra 70, I always hunt in a slightly positive mode. You will need to develop and fine tune your listening skills to put your detector in the correct slightly positive ground balance mode. The X-70 is the perfect detector to help you develop this skill. Set you detector up to hunt by first making sure you are in a location free of metal or hot and/or cold stones. Then, run the noise cancel procedure, go into AM mode, hit ground balance, then the auto mode switch, and the detector will ground balance itself correctly as you pump it up and down. Keeping it in the ground balance mode, hit the + button one time and pump the detector up and down approximately 6 to 8 inches or so, keeping it close to the ground at the end of the down swing. Listen to see if you can hear a slightly positive pitch on the down swing. If not, hit the + button for one more notch and repeat the process. With careful listening you will hear a very slight increase in pitch as you pump the detector toward the ground. This, in my opinion is what you are looking for to put you detector in the slightly positive mode. Depending on the ground, you may need to hit the + 3 times. I believe that hunting in the slightly positive mode gives you better depth. With practice you will be able to make the adjustment without any difficulty. If you hunt in the fixed GB mode, get in the habit of regularly checking you ground balance to be sure it is where you want it. After a while, it will become second nature and you will be more successful in hunting for nuggets, meteorites, coins. etc. I hope this helps. Good luck,

Darryl

 

[KurtB]

n/t

 

[skad71]

I read an article from Des Dunne from Minelab UK and as far as getting more depth that you shouls bump up the GB one number from where it auto ground balances at.He said that by doing this and running in two Tones seems to help.

 

[majesus]

Hi Digger,

I am doing some reading to learn how to optimize the settings/calibration on my new Xterra 70. I was reading your advice on tweaking the GB and I want some clearification on the following points you mentioned:

A setting of 1 is the most positive GB setting you can have with the X-Terra 70. And, the more mineralized the ground, the more positive setting you will need. A setting of 90 is the least positive GB setting of the X-70. And, the lower the mineralization, the less positive setting you will need. So, as mineralization increases, a more positive GB setting (lower X-Terra GB number) will be required to neutralize it. And, as the mineralization decreases, a less positive GB setting (a higher X-Terra GB number) will be required to neutralize the lower mineralized soil.

I like to tweak the GB a bit positive. That means that I am changing the GB setting so that the detector thinks there is less mineralization in the soil than the Automatic GB told it there was. To me, it makes the X-70 more responsive to deep targets and seems to be more sensitive to small ones as well. To do this, I will use Auto GB, then go to manual GB and press the - button a couple times.

This is where it seems to contradict. If you want your detector to be more "hot," wouldn't you want to tweak it for less mineralization than what the Auto GB is telling you? Ie, hit the "+" button to increase the number meaning calibrate on the side of less mineralization. If you hit the "-" you are telling the dector there is more mineralization in the ground then there is? Wouldn't that increase the discrimantion and be less sensitive? You want the system to be more sensitive, to see the deeper coins, so you need to make it not discrimante as much (let it see more of mineralsin the ground which could lead to more coins... )


Skad71 and Sport.Pilot say the opposite, to increase the GB number (hit the "+"):

This, in my opinion is what you are looking for to put you detector in the slightly positive mode. Depending on the ground, you may need to hit the + 3 times. I believe that hunting in the slightly positive mode gives you better depth. With practice you will be able to make the adjustment without any difficulty.

I read an article from Des Dunne from Minelab UK and as far as getting more depth that you shouls bump up the GB one number from where it auto ground balances at.He said that by doing this and running in two Tones seems to help.

 

[Digger]

I can understand the confusion as the posts do seem contradictory. Let me give it another shot...... I should probably have said: "running the detector with a more positive phase requires lowering the GB setting. I like to lower the GB setting a little, so that the detector compensates for the effects of a bit more mineralization than it does via Auto GB." If you consider compensating for mineralization as the most basic form of discrimination, it doesn't make much sense. But the same can be said about sensitivity. Running more sensitivity doesn't necessarily result in more depth. However, with the higher sensitivity settings I generally use, lowering the GB setting one or two clicks allows the actual targets to "stand out" from the falsing of mineralization or irregular sweeps. There are simply too many variables to make one definitive statement about settings. Soil, coil frequency, coil size, coil design etc. I just do what works for me at any particular site. My suggestion would be to learn (and take advantage of) the functionality available on the X-70 and establish the settings that work for you. When I first arrive at a site. I find a clear spot using the Prospecting mode. I Auto NC, Auto GB and then lower the Auto GB setting slightly. I hunt in all metal, multiple tone with as high of sensitivity as allowed (without falsing). Then I simply dig the targets that provide a consistent "location" and audio response. I use the TID to determine what I should be looking for in the hole. HH Randy

 

[Steve(MS)]

Generally with any detector with manual GB, a more positive setting tends to help with falsing issues.
A negative setting may actually help depth but may increase falsing or erratic signals.
Offsetting a little one way or the other shouldn't affect performance a great deal. Many of us tweak to get the results we like.

 

[majesus]

Thanks Digger for the input... I like the knowledge and help

I am curious to know a little more on the technicality of how the GB works, Is there an article I can read that gives some technicality on the theory of GB works? Interested to know how the machine actually goes about adjusting for mineralization in the ground?

 

[Jackpine Savage]

Here's a link to a short article by George Payne on Ground Balance.

George Payne on GB

Tom

 

[Neilo]

Generally speaking a slightly positive ground balance will high light weaker signals from either deeper or smaller targets. The only way to set your machine properly is on site with a tiny test target either a small nugget or lead shot are ideal. Bury the target in the ground adjust your ground balance to the point that you can hear the target the clearest.Remember the purpose of ground balance is to virtually see through the ground as though it doesnt exist. Also take into consideration your Threshold this will also help highlight weeker targets, once again the buried small target is the way to go to optimise the best setting. If running your machine on tracking mode (auto ground balance) go slow give your machine time to adjust to the varying ground conditions. When hunting for tiny nuggets a sweep speed of around 8 seconds is recommended It takes a lot of patience but it will pay off. seeya Neilo

 

[kansas]

Ok is see what your saying Digger. After you auto GB, and lets say it reads 40 you manualy turn it down to 39 or 38 by pressing the minus button. Thanks for the help.

 

[majesus]

Thanks everyone for the posts. Super Great info. It's like hitting that mid 44 target and finding out it's an old silver coin. AWESOME STUFF

Here's a link to a short article by George Payne on Ground Balance.
George Payne on GB
Tom

Perfect! Just what I wanted. I'll print it off as reading material. THanks so much.