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How Deep Do Today's Detectors Go Compared To Older Technology?

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I would like to see a test on large nuggets between a GPX in its deepest setting with the 19" Evo mono against a GPZ in its deepest setting with the 19" DOD.

 

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50 minutes ago, PhaseTech said:

In milder/medium mineralisation I'd be using the biggest DD you can get your hands on and Sharp timing.

Right on the money!

I've had good success on old deep patches doing just that with an 18" Coiltek DD.

Jim Stewart and I found that using DD coils larger than 18" (on SD/GP detectors) gave minimal advantage and any slight depth advantage was outweighed by the inconvenience factor. Apart from the obvious size and weight issues, this includes deep false signals caused by mineralisation when running in "sharp" timing.

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Hi Nenad, I do have a DD 24" and have tried it in sharp before just not on ground known for deep nuggets. Talking about a larger mono (22" coiltek) coil,  reminded me of a video that showed the difference between Enhance and normal timings on big gold. 

 

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Actually just found this video test between a GPZ and GPX on an undug target using larger coils.

 Hopefully Nenad does not mind me posting his test here on this forum and subject.

There appears to be very little difference between both the GPX and GPZ on this target.

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14 hours ago, flakmagnet said:

Slightly off topic but highlighted by PhaseTech's post - Am I wrong or has there been precious little attention paid to the Sharp timings on the GPX models? That timing is extraordinary if used in the right way in the right environment. I do wish someone who has had experience using it would publish a short note on how it was to work with and their results with it. 

Pretty much all I ever ran while in Alaska with my GPX was the Sharp timing. I generally run the most powerful timing the ground will allow, and Sharp is one of the most powerful Timings on the GPX. From the Minelab GPX 4000-5000 Manuals & Timings Charts:

“Sharp is similar to Normal but creates a more powerful detection field. It is capable of an improvement in depth, but is more susceptible to interference and will increase the severity of false signals in difficult grounds. This timing is best used in quiet conditions and can work well in combination with Deep Search Mode with a reduced Rx Gain setting. Sharp is an excellent tool for pinpointing faint signals due to the very "sharp" signal response. Sharp will work best with DD coils in most gold field locations.”

Sharp works well if the ground allows, and not well if the ground objects. I get the impression people pick timings based on internet posts or what a friend said, when they should be using the method outlined in the chart below to discover the best timing for the ground they are on. There is no “best” timing. The detector must be adjusted to fit the conditions. “The best timing is the deepest timing with no ground noise”.

Minelab GPX Timing Selection Chart - Click on image for larger version

minelab-gpx-choosing-correct-timing-larg

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Earlier in this thread, someone mentioned that VLF  depth  hit its peak depth years ago.  I have to disagree with that. Look at the depths the VLFs coming out of Eastern Europe are attaining.   This past summer I did some depth testing with my Rutus  ALter 71 on a freshwater beach.  I buried a silver half dollar  20 " deep in the dry sand , but the detector in deep mode (  not the super deep mode), close to max sensitivity,  disc at 40, one tone, 11" dd coil, and I get a repeatable signal.    How many VLF detectors from years ago could hit that?  No visual ID , but the audio gave a nice repeatable signal.  The Detech Chaser looks like its even deeper than the 71.  However  some of these machines are very fussy to set up,  and have their quirks also. But that comes with the territory.  The Russian AKA  machines are also very deep, but challenging to balance to  higher mineralized ground.  But if you spend a lot of time using these depth monsters , you will dig deep!.  

 

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22 minutes ago, Redneck said:

How many VLF detectors from years ago could hit that? 

No way to say without doing direct head to head tests. Possibly more than you are assuming.

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34 minutes ago, Redneck said:

Earlier in this thread, someone mentioned that VLF  depth  hit its peak depth years ago.  I have to disagree with that. Look at the depths the VLFs coming out of Eastern Europe are attaining.   This past summer I did some depth testing with my Rutus  ALter 71 on a freshwater beach.  I buried a silver half dollar  20 " deep in the dry sand , but the detector in deep mode (  not the super deep mode), close to max sensitivity,  disc at 40, one tone, 11" dd coil, and I get a repeatable signal.    How many VLF detectors from years ago could hit that?  No visual ID , but the audio gave a nice repeatable signal.  The Detech Chaser looks like its even deeper than the 71.  However  some of these machines are very fussy to set up,  and have their quirks also. But that comes with the territory.  The Russian AKA  machines are also very deep, but challenging to balance to  higher mineralized ground.  But if you spend a lot of time using these depth monsters , you will dig deep!.  

 

Sorry to burst your bubble but (Almost) any modern machine with an "All Metal" threshold will signal on a large coin at that depth, No ID but you will know it is there. depending on the current EMI.

One thing I'd like to point out is that detecting in dry/power sand is comparable to doing an Air Test and as such has no real world benefits/Value

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Tony (an old detecting friend) has inherited Jim Stewarts coil winding expertise. They spent a lot of time together in the workshop at Laanecoorie Park experimenting with ground loops, different coil configurations, etc. He also communicates regularly with Rowan (Nuggetfinder)

Tony has wound a number of concentric (coplanar) coils for the GPX and demonstrated some of them to me at the Laanecoorie test site earlier this year. Here's one not yet painted:

mlicTv0.jpg

On deep targets this type of coil clearly outperformed (depth wise and size for size) all the other coils we tested. These included flat wound and DD's.

Tony related how, using this type of coil he had clearly heard a 14 oz colour deeply encased in solid ironstone (in WA, dug up with a Makita jackhammer) when no other coil he tried could hear it, even when partly excavated.

Although we didn't test one on the day, Tony is of the opinion that this type of coil (size for size) will outperform the GPZ on deep targets:

H9TdRQO.jpg

So far I'm unable to bribe him into making me one :sad:

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That coil reminds me back in the A2B days the large concentric coil made by Dtex (spelling may be incorrect) was the coil for depth and was no slouch in sensitivity. It would be great to see these aftermarket coil manufacturers be given the green light for Z coils, I think they would do what they`ve done to the PI coils and by now maybe we`d have a selection of coil sizes and performance gain coils that push the depth boundaries even further.

Hopefully whatever it is that stops these innovative people doing so is overcome.

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