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Gold depth
Posted by: laplander
Date: December 07, 2017 07:12AM
Here the latest treasure talk with regards to detecting gold in mineralized soil.https://www.minelab.com/anz/go-minelabbing/treasure-talk/gold-depth-is-always-relative-to-ground-noise

I think its relative to all detecting whether its gold or silver / mineralized soil or iron infested ground.

HH Jeff

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Re: Gold depth
Posted by: Jason in Enid
Date: December 07, 2017 08:56AM
Quote
laplander
Here the latest treasure talk with regards to detecting gold in mineralized soil.https://www.minelab.com/anz/go-minelabbing/treasure-talk/gold-depth-is-always-relative-to-ground-noise

I think its relative to all detecting whether its gold or silver / mineralized soil or iron infested ground.

HH Jeff

Yep, the concept has been around since the beginning of the hobby but I have found that many users still don't understand how traditional ground balancing works or how FBS (and yes I know the EQ isnt FBS but it seems to use the same base theory on ground minerals) works to eliminate mineral noise. This is also why so many times in the CTX forum that users have to be told to stop using the GB function.

If you already understand the theory, you can skip the rest of this. If not, read on.

Modern VLF detectors work on the concept of the transmit coil and receive coil signal being in balance. When you lower the coil to the ground (with no targets) it gets a response back from the minerals. This response is a shift of the signal being received compared to what is expected (what is transmitted). So you turn a GB dial and shift that signal back to "normal" until you are no longer getting a response. The downside is that weak targets which would only shift the signal a little become lost. The practical result is that you lose depth on targets and lose sensitivity to small targets. The more you have to increase GB, the worse your performance becomes.

Then you have Minelab FBS ground cancelling technology which is completely different. First, the FBS sends a signal like the VLF but it reads the response like a Pulse Induction. This allows it to ignore ground minerals to much higher degree than standard VLFs. BUT, minerals do still have an impact so its compensated for by lower the sensitivity to adjust for increasing ground "noise". It still transmits at full power, it simply adjusts the threshold that something must meet before going on to analysis. For some of you other old timers, think it like the squelch on a radio. When you have a lot of static you can turn it up to clear the signal YOU HEAR and just hear the person talking to you. Or if the talker is a long way away, their signal is very weak so you can turn down that squelch and simply listen to the talker along with the static hiss.

Auto sens is letting the detector automatically adjust that "squelch" level, manual is setting it yourself if you want to try to find that signal mixed in with the noise. If you turn on the GB feature you are adding in that signal shifting on top of everything else. If you have REALLY bad ground, it can be the only way to have a chance to detect. If you don't have bad ground, you are going to lower the detectors performance. The GB on FBS is not an auto-trac. If you set it, then the ground mineral amount changes a few feet away, you are no longer in that optimum GB zone. So as the engineers have said, don't use it unless you have to.

Now, will all this hold true on the EQ? Possibly. Possibly not. Since they are still operating on that same "X - Y" signal analysis, I tend to think it will, but we'll just have to wait and see how much it has changed.



Edited 2 time(s). Last edit at 12/07/2017 09:02AM by Jason in Enid.

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