Effects Of Ground Balance On Target Depth?

[LipCa]

Steve,

Every since you posted that you lose depth when you ground balance, It is in the back of my mind........

"Ground balancing is a filter and not all that different that the way the discrimination system works. The ground signal or salt signal (or both) are identified and then tuned out. The ground effect is still there, but the detector subtracts it from the overall signal. The key word there is "subtracts". Ground balance methods work by subtracting part of the signal, and all subtractive methods create depth losses of some sort the closer any detected item gets to the "hole" created by subtracting the ground or salt signal. Signals are not perfect but spread over a small range, and so eliminating any signal usually means taking out a small range of signals. "

I have always tried to keep my detectors ground balanced while using them.... Now I wonder if I should?

 

Can you put my mind at ease......

[LipCa]

Maybe I wouldn't have heard the signals anyway because of the ground and it's a wash?

[Steve Herschbach]

Bingo. You do not lose depth when you ground balance on ground that requires ground balancing. You gain depth by eliminating the ground signal that is blocking the target signal. If you are detecting the ground, you can't detect the target.

However, by employing any filtering system (discrimination, audio smoothing, ground balancing, etc.) where it is not required you are going to block possible responses that do not need to be blocked.

This is easily seen with the White's TDI which allows you to turn the ground balance on and off. In air tests (and low to no mineral ground) you gain depth by shutting the ground balance off. As the ground gets worse and ground signals intrude, they mask target signals. At that point engaging the ground balance eliminates all the ground noise allowing you to hear the targets. It does cost you depth in absolute terms, but it is a moot point because eliminating the ground signals is paramount.

This page Link deleted since Findmall Forum update broke all old links has some depth tests with the TDI and ground balance on and off. The settings:

Air = Gain max, Ground Balance Off, Pulse Delay 10, Frequency 12 o'clock, Conductivity All, Threshold hum.
Low = Gain max, Ground Balanced at between 7-8, Pulse Delay 10, Frequency 12 o'clock, Conductivity LOW, Threshold hum.
All = Gain max, Ground Balanced at between 7-8, Pulse Delay 10, Frequency 12 o'clock, Conductivity ALL, Threshold hum.

Check out the chart paying particular attention to the Air vs All measurements. The air depths are close to what you will get for depth using no ground balance in "no mineral ground" i.e. pure white Florida coral sand. The chart also highlights how in low mineral locations an MXT may be the better choice.

For machines that have the capability however it is important to know this because running ground balance where it is not needed does rob depth. And in very low mineral ground savvy VLF operators can sometimes gain depth by purposefully offsetting the ground balance control. If the ground is not signaling over a wide range when you change the setting, is it better to set lower or higher? It depends on the targets sought and knowing how your machine performs inside and out. Hint - if your detector has a ground balance control that goes from 1-10 then take a quarter and a nickel. Air test both at GB setting of 2 and GB setting of 8 and observe what happens.

Double dark secrets of the pros...

[Steve Herschbach]

This is a big issue with Minelab GPX detectors. All the "Timings" are is different preset PI ground balancing schemes designed to deal with different ground types. The settings get progressively more aggressive to deal with more difficult ground and hot rocks if you encounter them. You should always run the least aggressive setting that gets the job done.

However, some people who do not know their machines and what exactly those settings are doing. Others like myself may know better but fall into bad habits. On the GPX 5000 the Fine Gold setting is a bit of a dream in many severe ground conditions. Bad ground and rocks just disappear! It works so well in bad ground it is tempting to just leave the machine in Fine Gold all the time.

However, Fine Gold is a very aggressive timing (filter) and I promise you without a doubt it will tune out and miss certain gold types. If you are running Fine Gold in ground where the Normal mode runs acceptably, you are missing gold. Period. My go to settings in mild Alaska ground were Sharp for large deep nuggets and Sensitive Extra for small gold.

Prospectors who can deal with some hot rocks and some ground noise, mainly by mental filtering through tonal differences, can run more aggressive timings like Normal in at least limited small areas that deserve the extra effort. They may dig more hot rocks, but the location if good will most likely also reveal more gold that was previously hidden by aggressive timings.

The GPZ 7000 is no different. Here is a thread from a bloke in Australia that has discovered the joys of the Normal versus Difficult ground setting, along with the price to be paid in bad ground by way of noise - but also more gold found.

It is often not that you want to hunt like this in general. But if you have a 20 ft by 20 ft area that has really produced, and have a machine with multiple ground setting options, going hot and just dealing with the noise will often reward the operator. Tip - super slow and absolute coil control especially height over the ground.

GPX owners - click on the chart below to get the larger version and read the box in lower right (Best Timing) and do pay attention to the depth chart. Note that you can actually turn the ground balance off on a GPX, but I never found ground mild enough to allow it. Beach hunters in Florida take note....

[Steve Herschbach]

Specifically in your case Harry, do a manual reset on your ATX whenever moving to new ground to start fresh and be sure you do not have overly aggressive settings locked in from the last location. This is critical as the ATX does "remember" the last settings used.

Factory Reset

All changes made to the ATX settings are saved when the unit is switched OFF. To return all settings back to Factory values, press and hold the RETUNE/ PINPOINT button while switching unit ON.

ATX FACTORY/DEFAULT SETTINGS

Mode: Motion
Discrimination: Zero discrimination (1st LED)
Sensitivity: 10
Threshold: 7
Volume: 10
Ground Balance: Neutral
Ground Track: OFF

 

[strick]

This is very good thred and everyone should read it. It needs to be pinned or something. I try and run in normal as much as I can with the 7K 

strick

[LipCa]

I can finally get some sleep!

Thanks Steve

[Steve Herschbach]

1 hour ago, strick said:

This is very good thread and everyone should read it. It needs to be pinned or something. I try and run in normal as much as I can with the 7K 

I agree. I should ask more than I do (as editor in chief I don't) but I often change thread names and locations so that the subject line reflects the content of the thread. It aids people doing searches later. I don't alter thread content however unless to perhaps fix a spelling error for somebody or to add links. That said, the thread name has been changed with apologies to Harry but thanks as always for getting it started!

[Desert Dawg]

Any idea of what the "new form of ground balance" on the not yet seen CZX may be? Supposed to go much deeper than current vlfs.

[Steve Herschbach]

Something tells me that is a closely held proprietary secret!