Questions On Garrett ATX - VLF Alternatives For Porous Gold

[idahogold]

Always Carry a .45 00 imo! 

[Shelton]

Boys, you are ground balancing ATX or trying to search after ground balance factory reset?

 

 

[Glenn in CO]

14 hours ago, Steve Herschbach said:

What machines are you using Glenn?

We are using the White's GMT. The area we hunt is mostly mild ground with hot rocks that will give a overload signal on the detector. I believe the Gold Bug 2 would do as well or maybe even better because of it's high operating frequency. Some of this type of crystalline gold specimens we find becomes invisible when using a PI detector. It would be great if a PI detector or some new technology would be able to detect this type of gold as it would open up the area we are hunting in because of the increase in depth and manage the hot rocks better.

[Steve Herschbach]

Have you tried your gold on either the SDC 2300 or GPZ 7000? They will not match a hot VLF but are the best of the alternatives.

[Glenn in CO]

36 minutes ago, Steve Herschbach said:

Have you tried your gold on either the SDC 2300 or GPZ 7000? They will not match a hot VLF but are the best of the alternatives.

We tried the SDC 2300 and had the same results. We tried the TDI with a small 7.5 Dual Field coils and still cannot detect that type of gold, but we haven't had the opportunity to try the GPZ 7000. The other thing I failed to mention is the area has a abundance of nails which makes using a PI a little less attractive, but finding a nice gold specimen that a VLF would miss would be a trade off I could deal with.

[Steve Herschbach]

Again, I would not expect the alternatives to match a hot VLF in absolute terms. And it is shades of gray, not black and white, since every specimen is unique. The basic question being presented here is what alternative to a hot VLF has the best chance of finding at least some of the types of specimens we are talking about. A redesigned TDI might do it or the QED by all accounts. But sticking with current mainstream devices in my experience the SDC 2300 is about as good as it it gets at the moment. I actually think based on what I know about the technology that the GPZ 7000 is superior, but it needs a smaller coil to really exceed what the SDC 2300 can do. The SDC is a very fast PI but it is still a PI. Pulse induction by definition has a delay between the transmit and receive modes designed to eliminate the responses from bad ground and hot rocks. The type of gold we are talking about falls into that short delay area. It is ironic but it is the ability to react to bad ground and hot rocks that gives a high frequency detector its ability to find porous and wire gold.

The GPZ is not a PI, but a hybrid that employs constant current electronics with time domain processing. The GPZ truly is more a super VLF than a PI detector. That is why it struggles with salt ground and hot rocks the SDC and other PI detectors can ignore. That is also why it is inherently more capable of detecting the type of gold we are talking about. It is why I am anxious to get a small coil for the GPZ.

What is needed is a very fine degree of tuning to ride the fine line between reducing ground and hot rock signals while still retaining as many gold signals as possible. The two overlap. Part of the problem I am seeing is detectors like the SDC and GPZ having a few preset tuning positions. What is needed is more like an infinite potentiometer that would allow the operator to achieve very tiny adjustments in order to get the degree of differentiation needed when dealing with the ferrous/salt/gold overlap area.

In theory the pulse delay on a PI can be shortened to the point where the responses are indistinguishable from a VLF. The delay gets so short that for all practical purposes there is no delay. The ability to make that adjustment is one way to do things. In the GPZ it is done more through post detection processing of the signal. The technology is there, we just need finer control over it. At the end of the day however, just like how for every gold jewelry item there is a aluminum item that reads the same, there will be gold that perfectly overlaps with certain ground and salt responses. Eliminating the undesired item eliminates the desired item with it.

[aufarmer]

I actually had a little better luck with the TDI, but wasn't happy with the depth.  I am hoping the new Minelab may perform well.  I did finally see a video of someone air testing some gold nuggets with the XP Deus and new round HF coil, and thought he was getting good response from a .05 gram nugget.  It has me thinking I may go with the new elliptical HF coil if it is sold with a detector.

[Steve Herschbach]

The new Minelab at 45 kHz and the new DEUS HF coils I expect to do well on small and porous gold, but be right back to struggling with bad ground and hot rocks. At the end of the day they will be high frequency induction balance detectors, that will be in the White's GMT and Fisher Gold Bug 2 realm when it comes to performance, but with the caveats that come along with that.

The TDI can with the right coil and some mods can run very hot on small gold.

[aufarmer]

Is a SDC or GPZ capable of even detecting a solid gram piece of gold at 10 to 14 inches?  I guess if they couldn't do that fairly often then with the gold I am working with I should probably just stick with a VLF.  Maybe I'm expecting too much out of a PI to begin with.

[Steve Herschbach]

There is a misunderstanding that often occurs when people consider PI detectors. They are by definition designed to deal with hot rocks and mineralization that a VLF cannot deal with. If you are having no issues with ground mineralization and hot rocks, then yes, it may be that you expect too much of a PI. In air tests a hot VLF will often out detect a PI if both are running identical coils. The same would be seen in extremely mild ground. If you ever get into real bad ground or intense hot rocks, then you learn to appreciate what a PI can do.

In general PI detectors do not detect deeper than VLF detectors in absolute terms. What they do is lose depth less quickly as ground mineralization increases. You can have a VLF and PI detect a nugget at the same depth in low mineral ground. Then with much more mineralization the VLF loses a lot of depth, and the PI only a little depth. Now the PI is going 50% deeper than the VLF. Add even more mineralization, and the VLF is getting less than half the depth it was in the low mineral ground. The PI also loses some depth, but again, not near as much, and now detects twice as deep as the VLF.

It is all relative to the ground mineralization, and is why air testing prospecting machines PI versus VLF is leaving out the most important factor.