Minelab Gpx17 (17x13) Mono Coil Now Or Wait For Nf 16x10 Mono

[phrunt]

22 hours ago, GR Guy said:

If NF wire the 16x10 like the 12x7, it will be closer to a 14x9 Coiltek in wiring

Is that because of the 12x7’s lack of edge sensitivity you’re saying that?

[strick]

Late to the thred Dutchman PM sent on the 17 inch coil...

That NF 12x7 sure is a smooth running coil and does well on small gold but I've found the Coiltek 10x5 to be the better of the two on the smaller stuff...It really surprised me on a heavily hunted patch that had been gone over with the NF 12x7

strick  

 

 

 

[Dutchman4]

3 hours ago, strick said:

Late to the thred Dutchman PM sent on the 17 inch coil...

That NF 12x7 sure is a smooth running coil and does well on small gold but I've found the Coiltek 10x5 to be the better of the two on the smaller stuff...It really surprised me on a heavily hunted patch that had been gone over with the NF 12x7

strick  

 

 

 

Thanks for the feedback. 

Finding a 0.023 gram nugget, at around 1 to 1.5" deep, with the NF 12x7 is small enough for me and I have no need or desire to find anything smaller than that.  If one didnt already own the 12x7 then the 10x5 might be a consideration but for me there is no need to own both.

[PhaseTech]

On 1/6/2024 at 7:22 PM, GR Guy said:

If NF wire the 16x10 like the 12x7, it will be closer to a 14x9 Coiltek in wiring which is $200 cheaper.

Technically true, but a 16x10 is hardly enough length for the true patch hunters in WA. 12" and 14" just isn't long enough is the feedback that I've got. They want coverage and would probably prefer an 18" length coil. 

[PhaseTech]

My experience with the GPX17 is the following:

- You give up a little sharpness on smaller bits at depth, but it is still crazy sensitive on shallow targets

- It does give a little more depth, but only where mineralisation doesn't create more noise

- Obviously not as light as the 11", so I found I need to start using a bungy. 

- I've had a little success with it in more open ground, which for me is in the older pine forest areas, but the ground needs to be super dry, which is quite rare as it's always in shade and covered in a layer of pine needles! In the native vegetation it is just way too overgrown to swing it nicely. 

If you have open ground where you can swing it, and don't have other detectors with big coils, then I think it's a good addition to the kit. 

[Jonathan Porter]

Biggest issue with going larger coils with an extremely sensitive PI is the conductive signal. Open areas like WA are really bad for conductive signals and will punish an operator if they go too big. You can use a GPX 5000 with a large coil for prospecting which is less prone to conductive signals but then you lose that tiny nugget sensitivity of the GPX6000 which can be the on;y clue to a good patch or gold being in the area. The GPZ7000 has the same limitation which is why NuggetFinder built the Zsearch 17x13, a good compromise between sensitivity and coverage in vast open spaces.

I’ve used one of the early proto 16x10 Nugget Finders in WA and found it to be a very nice blend of quiet running and good coverage with very good depth, it’s like a plumped up 12x7 Xceed. It’s still a work in progress and had to be put aside all of last year due to a number of factors. There are only so many hours in a day, the demand for the 12x7 was off the charts and still is by all accounts.

JP

[Dutchman4]

3 hours ago, Jonathan Porter said:

Biggest issue with going larger coils with an extremely sensitive PI is the conductive signal. Open areas like WA are really bad for conductive signals and will punish an operator if they go too big. You can use a GPX 5000 with a large coil for prospecting which is less prone to conductive signals but then you lose that tiny nugget sensitivity of the GPX6000 which can be the on;y clue to a good patch or gold being in the area. The GPZ7000 has the same limitation which is why NuggetFinder built the Zsearch 17x13, a good compromise between sensitivity and coverage in vast open spaces.

I’ve used one of the early proto 16x10 Nugget Finders in WA and found it to be a very nice blend of quiet running and good coverage with very good depth, it’s like a plumped up 12x7 Xceed. It’s still a work in progress and had to be put aside all of last year due to a number of factors. There are only so many hours in a day, the demand for the 12x7 was off the charts and still is by all accounts.

JP

Can you please give technical explanation of "conductive signal"?  Is that a ground condition?

[Jonathan Porter]

19 hours ago, Dutchman4 said:

Can you please give technical explanation of "conductive signal"?  Is that a ground condition?

Not so sure about my ability to be too technical 😊 but in essence conductive signals are salt signals created by moisture in the ground. Even in the desert there is sub soil moisture and particularly in goldfields because gold weathering from host rock involves a lot of clays being formed. The rocks on the land contain minerals, those minerals get absorbed by water after rain, the water then flows to the sea and evaporates leaving the minerals behind, that is why the earths oceans are salty. 

During rain events in the goldfields the weathered country also has concentrations of minerals on the surface of the ground this is due to oxidation just like rust on your car, when those concentrated minerals get damp the conductive signal increases dramatically and in some instances to the point that a metal detector is unusable or a coil that can handle conductive signals has to be used (like the DD coil supplied with the GPX6000).

When conductive signals are present the response they create masks or hides edge of detection deep signals, the detector also becomes very swing speed dependant so a slow Motion filter becomes problematic (called recovery on a lot of coin machines), the GPZ 7000 has a Motion filter called Ground Smoothing when applied you can hear the threshold becoming more erratic and unstable but depth is lost so I never use it and instead focus on my coil control.

Conductive signals are made worse by larger coils, this is because the conductive signal is seen from a very long way away from the coil. In wet conditions you can see this for yourself by lifting/raising the coil from ground height to above your waist, you will hear a loud long drawn out moaning sound as the coil is moved through an arc. So a smaller coil is recommended when the ground is damp which does not help ground coverage when patch hunting in wide open spaces.

The other issue is damp mineralised clays, those can have a complicated effect on a metal detector, especially a highly sensitive machine like the GPX 6000, or GPZ 7000. They produce a combination of conductive signals and another effect on micro magnetic particles in the soils which are impossible to ground balance out, these signals can sound very target like both sharp and shallow sounding and also broad and edge of detection deep sounding. The wetter the ground the worse they are.

A key to identifying these is coil control and sweep speed. There are a few immutable things about a motion detector, if using a consistent range of motion relative to the depth of a target (that’s the amount of distance the coil needs to be swept relative to the ‘lead in’ and ‘tail out’ positions of a target, basically from the point the threshold starts to change from the left to right and the other point going back the other way from right to left), then two factors have a bearing on a “real” target over a ground generated one.

One is the height of the coil relative to target, in other words the closer you get to a target the louder it should get (very dependant on ground effect (for another discussion another day)) and the speed of the sweep. If the range of motion is maintained but the sweep speed is halved then theoretically the target response should effectively double. A conductive target like response will not do this and will get quieter not louder. In other words, in damp conditions slow down.

The reason we move the coil is because the detectors are motion detectors (coil needs to move relative to the target to generate a response), the coil movement is all about the receive aspect not the transmit, moving the coil allows you to investigate any weak fields created by a target, the receive coil of the detector needs to move through the field created by the target, these fields will be thousands of times weaker than the transmit so require careful coil control to manifest properly. Hence why it’s so important to have good coil control, being prepared to vary and control the sweep speed and maintain a good range of motion when investigating edge of detection targets.

Accurate ground balance, consistent coil height, good range of Motion and constantly tweaking the swing speed are all vital skills for working successfully with a metal detector, especially in conductive areas. You get all these things into alignment and deep targets jump out at you.

Hope this helps
JP

[flakmagnet]

Thank you JP, you always make sense.

[Dutchman4]

4 hours ago, Jonathan Porter said:

Not so sure about my ability to be too technical 😊 but in essence conductive signals are salt signals created by moisture in the ground. Even in the desert there is sub soil moisture and particularly in goldfields because gold weathering from host rock involves a lot of clays being formed. The rocks on the land contain minerals, those minerals get absorbed by water after rain, the water then flows to the sea and evaporates leaving the minerals behind, that is why the earths oceans are salty. 

During rain events in the goldfields the weathered country also has concentrations of minerals on the surface of the ground this is due to oxidation just like rust on your car, when those concentrated minerals get damp the conductive signal increases dramatically and in some instances to the point that a metal detector is unusable or a coil that can handle conductive signals has to be used (like the DD coil supplied with the GPX6000).

When conductive signals are present the response they create masks or hides edge of detection deep signals, the detector also becomes very swing speed dependant so a slow Motion filter becomes problematic (called recovery on a lot of coin machines), the GPZ 7000 has a Motion filter called Ground Smoothing when applied you can hear the threshold becoming more erratic and unstable but depth is lost so I never use it and instead focus on my coil control.

Conductive signals are made worse by larger coils, this is because the conductive signal is seen from a very long way away from the coil. In wet conditions you can see this for yourself by lifting/raising the coil from ground height to above your waist, you will hear a loud long drawn out moaning sound as the coil is moved through an arc. So a smaller coil is recommended when the ground is damp which does not help ground coverage when patch hunting in wide open spaces.

The other issue is damp mineralised clays, those can have a complicated effect on a metal detector, especially a highly sensitive machine like the GPX 6000, or GPZ 7000. They produce a combination of conductive signals and another effect on micro magnetic particles in the soils which are impossible to ground balance out, these signals can sound very target like both sharp and shallow sounding and also broad and edge of detection deep sounding. The wetter the ground the worse they are.

A key to identifying these is coil control and sweep speed. There are a few immutable things about a motion detector, if using a consistent range of motion relative to the depth of a target (that’s the amount of distance the coil needs to be swept relative to the ‘lead in’ and ‘tail out’ positions of a target, basically from the point the threshold starts to change from the left to right and the other point going back the other way from right to left), then two factors have a bearing on a “real” target over a ground generated one.

One is the height of the coil relative to target, in other words the closer you get to a target the louder it should get (very dependant on ground effect (for another discussion another day)) and the speed of the sweep. If the range of motion is maintained but the sweep speed is halved then theoretically the target response should effectively double. A conductive target like response will not do this and will get quieter not louder. In other words, in damp conditions slow down.

The reason we move the coil is because the detectors are motion detectors (coil needs to move relative to the target to generate a response), the coil movement is all about the receive aspect not the transmit, moving the coil allows you to investigate any weak fields created by a target, the receive coil of the detector needs to move through the field created by the target, these fields will be thousands of times weaker than the transmit so require careful coil control to manifest properly. Hence why it’s so important to have good coil control, being prepared to vary and control the sweep speed and maintain a good range of motion when investigating edge of detection targets.

Accurate ground balance, consistent coil height, good range of Motion and constantly tweaking the swing speed are all vital skills for working successfully with a metal detector, especially in conductive areas. You get all these things into alignment and deep targets jump out at you.

Hope this helps
JP

That was plenty technical for me, Thank you. 

Maybe even more reason for me to wait for the NF 16x10 coil to be released since the NF 12x7 is inherently quieter than the stock 11 inch, unless that is only because it is smaller (less sq inches) and sees less ground. 

Regards,  Ceril