Nexus 30" and 21" Concentric Coils For Minelab GPX

[Candigger]

Video depth test of Nexus 31"CC and 21"CC on GPX4500 in Iron Rejection - 10, with 1 kg. of small Roman bronze coins at 85 cm under ground.
I do realise there are no Roman coins in Australia, but surely there are other treasures to find apart from gold nuggets. Every land got its folktales of hidden treasures.
This video could give a hint to anyone interested in hoard and treasure hunting.

The hoard also represents a large size specimen with a lot of gold specs in it. This hoard is just as difficult to get as those species.

 

[Candigger]

All of the previously mentioned tests on both 21"CC and 30"CC are complete and available on You Tube for watching.

21"CC complete air test, same as 30"CC air test.
30"CC depth test on highly mineralised soil loaded with magnetite.
21"CC depth test on highly mineralised soil loaded with magnetite.
30" and 21" CC on 1 kg. of small Roman bronze coins at 85 cm in the ground and Iron Rejection at 10.
30" and 21" EMI suppression test 25 meters away from 50kV power lines and air test demonstration in that situation.

Here is the last EMI test.



Coming soon - 12"CC, 14"CC and 16"CC based on ABS construction with price range similar to all other brands and within the expected for ABS type coils.

 

[Araratgold]

Yep, an air test like this is meaningless if you can't run it over mineralised ground ! VLF's air test very well, but fail in the mineralised ground.

Show us the coil running in some nasty ground over some targets, without loss of depth, then we may get a bit more excited !

Rick

 

[Candigger]

Yep, an air test like this is meaningless if you can't run it over mineralised ground ! VLF's air test very well, but fail in the mineralised ground.

Show us the coil running in some nasty ground over some targets, without loss of depth, then we may get a bit more excited !

Rick

Here it is from 3 months ago and some quite nasty ground. Arable fields are particularly bad when loaded with magnetite and all sorts of other crap.

 

[Aussiedigs]

In the air test the detector head unit is closer to the coil than the can. Detecting with the shaft in a typical scenario at approx 45 deg it could be assumed the head unit will still be close compared to the coils supposed detection range. Is this an issue?

 

[Rush]

Here is the last EMI test.

Candigger another interesting video, well for me anyway.

Therefore in regards to your settings for both coils in this EMI test what was the coil switch position set too, was it switched in the Maximum Depth position or was it switched in the Hot Ground position which Hendo87 has named High Mineralised position?

 

[Candigger]

Here is the last EMI test.

Candigger another interesting video, well for me anyway.

Therefore in regards to your settings for both coils in this EMI test what was the coil switch position set too, was it switched in the Maximum Depth position or was it switched in the Hot Ground position which Hendo87 has named High Mineralised position?

The coils work near power lines only in Hot Ground mode. In Hot Ground mode the coils are also very sensitive to small gold.

 

[Candigger]

In the air test the detector head unit is closer to the coil than the can. Detecting with the shaft in a typical scenario at approx 45 deg it could be assumed the head unit will still be close compared to the coils supposed detection range. Is this an issue?

No, because the head unit is static to the coil and the distance is considerable. The coil cables are intentionally cut to length so the detector shaft will have to be extended at full distance, so that the head unit will not interfere.

 

[hermann]

HI there, A year ago I was robbed including my 19" evo coil, so I needed another biggish coil, so my lovely wife bought me a Nexus 21" cc coil. THen I did some gardening at home and pulled a muscle or hamstring in one of my legs and that was about 3 weeks ago, so no gold hunting for me. However, I did go to the golden triangle to test this coil in very mineralised ground , on a 58gm piece of lead 450mm down. I asked a friend to join me and I told him to take his best detector and coil with him , he has a lot of detectors and coils . He decided to take his GPZ 7000 with a 10" round X Russian coil, he knows the 7 and the 10" coil very well, Graham could just hear the 58grammer , then it was my turn with the 21" cc . and my speaker was screaming at me . my 5000 was set in normal and the Nexus coil switch was in maximum depth. In these settings I could not detect the surrounding area, the machine was too noisy, I then flicked the coil switch over to hot ground and the machine became very stable and I could still hear the 58grammer loud and clear. the coil works also in cancel and DD, but not as powerful as in normal. I just hope that my leg problem gets better soon so that I can chase some lumps of gold.

 

[washgravel]

After reading Hermann's results in the Detech CC coil discussion in regards to the Nexus 21" CC coil I thought I should ask my questions here since this is related to the Nexus 21"CC coil.

As Hermann mentioned for his test with the 21" CC coil on his 5000, when it was set in Normal (timing) and the coil switch set in Maximum Depth, he could not detect the surrounding area as the detector was too noisy and I expect also due to the detector's Coil/Rx position set in Mono?

He also mentioned the coil works in Cancel and DD so does either with the detector set in Normal and the coil switch still set in Maximum Depth continue to be too noisy over the surrounding area?

And when he flicked the coil switch to the Hot Ground position the detector became very stable and could still hear the 58g target at 45cm, however could he still detect the surrounding area with the Coil/Rx position still set in Mono?

Also could either or both Cancel and DD hear the 58g at 45cm as loud and clear as Mono with the coil switch set in the Hot Ground position?

 

[Candigger]

After reading Hermann's results in the Detech CC coil discussion in regards to the Nexus 21" CC coil I thought I should ask my questions here since this is related to the Nexus 21"CC coil.

As Hermann mentioned for his test with the 21" CC coil on his 5000, when it was set in Normal (timing) and the coil switch set in Maximum Depth, he could not detect the surrounding area as the detector was too noisy and I expect also due to the detector's Coil/Rx position set in Mono?

He also mentioned the coil works in Cancel and DD so does either with the detector set in Normal and the coil switch still set in Maximum Depth continue to be too noisy over the surrounding area?

And when he flicked the coil switch to the Hot Ground position the detector became very stable and could still hear the 58g target at 45cm, however could he still detect the surrounding area with the Coil/Rx position still set in Mono?

Also could either or both Cancel and DD hear the 58g at 45cm as loud and clear as Mono with the coil switch set in the Hot Ground position?

These questions can be answered only by Hermann.

To make it more clear of why some of those results occur I need to mention the following;

The Nexus CC coils with their dual cables are working as two coils in one package. In Maximum Depth the coils work like Mono coils with every expectation of a Mono coil behaviour - best depth, noisy ground problems ect.
In Hot Ground the coils work like CC/DD with typical behaviour of a CC/DD coils including good sensitivity to small gold.

The reason this was included in the Nexus CC designs is that the GPX detectors limit the depth when used with CC and DD coils due to the added self capacitance of the RX cables and loops.

In general what you can expect from any Nexus CC coil is the best possible depth that can be expected from equivalent size Mono coil, when switched to Max. Depth on some targets even better.
In Hot Ground Mode the best depth one can expect from a concentric coil with all of the features of a CC coil.

Two coils CC and Mono in one package.

When Nexus CC coil is in use one does not have to change coils for the different soil types. Just flick the switch and go from CC to Mono coil or the opposite.

Any claim that generic CC coil is as deep as the same size or even bigger Mono coil is bogus. It can not happen with the GPX unless the coil can work as pure Mono, which currently only the Nexus CC coils can do.

 

[washgravel]

In Hot Ground Mode the best depth one can expect from a concentric coil with all of the features of a CC coil.

Any claim that generic CC coil is as deep as the same size or even bigger Mono coil is bogus.

Candigger what Mono (round) coil size do you think your 21" CC coil would be equivalent too when set in Hot Ground Mode with the GPX switched in DD or Cancel..... or even Mono if Mono is capable to handle hot ground with the coil in the HOT Ground Mode setting?

 

[Candigger]

In Hot Ground Mode the best depth one can expect from a concentric coil with all of the features of a CC coil.

Any claim that generic CC coil is as deep as the same size or even bigger Mono coil is bogus.

Candigger what Mono (round) coil size do you think your 21" CC coil would be equivalent too when set in Hot Ground Mode with the GPX switched in DD or Cancel..... or even Mono if Mono is capable to handle hot ground with the coil in the HOT Ground Mode setting?

To answer accurately this question will have to go trough some digits.
I will use as an example some of my air test measurements.
All settings are FP, Mono, Fixed, Normal, Deep.
Coil 21"CC
Max. Depth/Mono - 330ml can at 145 cm
Hot Ground/ CC - 330 ml can at 140 cm, - 3.45%

Max. Depth/Mono - 600 gr. nugget at 135 cm
Hot Ground/ CC - 600 gr. nugget at 125 cm, -7.4%

Max. Depth/Mono - 5 grams gold ring at 75 cm
Hot Ground/ CC - 5 grams gold bar at 62 cm, -17.3%

Max. Depth/Mono - 5 grams gold bar at 60 cm
Hot Ground/ CC - 5 grams gold bar at 50 cm , - 20%

Max. Depth/ Mono - 0.5 grams Australian gold nugget at 19 cm
Hot Ground/ CC - 0.5 grams Australian gold nugget at 20 cm , + 5.2%

I have more detailed test table, which describes the tendency of loosing depth consistently when the coils are used as Concentric. In Mono mode they are deeper always, short of the 0.5 grams gold nugget case where the RX loop adds some small extra depth.

So to answer your question you will have to choose what type of target is the most likely for you to be interested in and then take into account the mentioned above results, which vary from 20% loss of depth to 5.2% gain of depth.

As a rule of thumb 10% smaller in diameter coil will exhibit 20% loos of depth. So in the worse result scenario this 21"CC in Hot Ground mode will be equivalent to a 19" Mono. If we take into account that the GPX depth changes are not linear with coil size increments then the 21"CC in Hot Gropund mode will be more equal to 19.5-20" Mono.

 

[hermann]

Hi Washgravel, With the coil switch in hot ground position and the detector in mono mode I could detect the surrounding area with no problems. Due to my leg problem at the moment I could not gather any more expierience with this high tech coil. I do have some information about settings that could make this coil even more interesting. Hopefully I will be out there learning more about this coil very soon.

 

[washgravel]

Candigger below I have added further info to your results above.

GPX 4500(All settings are FP, Deep, Fixed GB and in Normal timing) with Nexus 21" CC coil .

Air Depth Test Results

Max. Depth/Mono - 330ml can at 145 cm
Hot Ground/ Mono - 330 ml can at 140 cm, - 3.45% less
Hot Ground/ Cancel - 330 ml can at 130 cm, -11.5% less
Hot Ground/ DD - 330 ml can at 120 cm, - 20.8% less

Max. Depth/Mono - 600 gr. nugget at 135 cm
Hot Ground/ Mono - 600 gr. nugget at 125 cm -7.4% less
Hot Ground/ Cancel - 600 gr. nugget at 115 cm - 17.3% less
Hot Ground/ DD - 600 gr. nugget at 100 cm - 35% less

Max. Depth/Mono - 5 grams gold ring at 75 cm
Hot Ground/ Mono - 5 grams gold ring at 62 cm - 20.9% less
Hot Ground/ Cancel - 5 grams gold ring at 60 cm - 25% less
Hot Ground/ DD - 5 grams gold ring at 56 cm - 33.9% less

Max. Depth/Mono - 5 grams gold bar at 60 cm
Hot Ground/ Mono - 5 grams gold bar at 50 cm - 20% less
Hot Ground/ Cancel - 5 grams gold bar at 48 cm - 25% less
Hot Ground/ DD - 5 grams gold bar at 40 cm - 50% less

Max. Depth/ Mono - 0.5 grams Australian gold nugget at 19 cm
Hot Ground/ Mono - 0.5 grams Australian gold nugget at 20 cm - 5.2% more
Hot Ground/ Cancel - 0.5 grams Australian gold nugget at 12 cm - 58.3% less
Hot Ground/ DD - 0.5 grams Australian gold nugget at 20 cm - 5.2% more

 

[Ded Driver]

600gr nugget? solid or speci? if solid that's near 20oz .. I wouldn't be advertising having that laying about the house!
interesting results on the % loss on gold

 

[Candigger]

600gr nugget? solid or speci? if solid that's near 20oz .. I wouldn't be advertising having that laying about the house!
interesting results on the % loss on gold

It's the Tin/Lead simulation nugget that I use for tests. The thieves are welcome to steal it.

 

[Candigger]

Candigger below I have added further info to your results above.

GPX 4500(All settings are FP, Deep, Fixed GB and in Normal timing) with Nexus 21" CC coil .

Air Depth Test Results

Max. Depth/Mono - 330ml can at 145 cm
Hot Ground/ Mono - 330 ml can at 140 cm, - 3.45% less
Hot Ground/ Cancel - 330 ml can at 130 cm, -11.5% less
Hot Ground/ DD - 330 ml can at 120 cm, - 20.8% less

Max. Depth/Mono - 600 gr. nugget at 135 cm
Hot Ground/ Mono - 600 gr. nugget at 125 cm -7.4% less
Hot Ground/ Cancel - 600 gr. nugget at 115 cm - 17.3% less
Hot Ground/ DD - 600 gr. nugget at 100 cm - 35% less

Max. Depth/Mono - 5 grams gold ring at 75 cm
Hot Ground/ Mono - 5 grams gold ring at 62 cm - 20.9% less
Hot Ground/ Cancel - 5 grams gold ring at 60 cm - 25% less
Hot Ground/ DD - 5 grams gold ring at 56 cm - 33.9% less

Max. Depth/Mono - 5 grams gold bar at 60 cm
Hot Ground/ Mono - 5 grams gold bar at 50 cm - 20% less
Hot Ground/ Cancel - 5 grams gold bar at 48 cm - 25% less
Hot Ground/ DD - 5 grams gold bar at 40 cm - 50% less

Max. Depth/ Mono - 0.5 grams Australian gold nugget at 19 cm
Hot Ground/ Mono - 0.5 grams Australian gold nugget at 20 cm - 5.2% more
Hot Ground/ Cancel - 0.5 grams Australian gold nugget at 12 cm - 58.3% less
Hot Ground/ DD - 0.5 grams Australian gold nugget at 20 cm - 5.2% more

Ok. In my description I forgot to mention the Hot Ground settings were all in Mono. Your addition that you got from my videos is correct and consistent with my records as well.

There is a little inaccuracy in the percentage calculations you presented.
For example 15 cm loss from 75 cm is 20%. not 25%.
7 cm loss from 19 cm is 36.8%, not 58.3%.

Example; If you add 15 on top of 60 = 75, the increase is 25%, but if you remove 15 from 75 the decrease is 20%.

Here are the correct figures;
Max. Depth/Mono - 330ml can at 145 cm
Hot Ground/ Mono - 330 ml can at 140 cm, - 3.45% less
Hot Ground/ Cancel - 330 ml can at 130 cm, -10.3% less
Hot Ground/ DD - 330 ml can at 120 cm, - 14.8% less

Max. Depth/Mono - 600 gr. nugget at 135 cm
Hot Ground/ Mono - 600 gr. nugget at 125 cm -7.4% less
Hot Ground/ Cancel - 600 gr. nugget at 115 cm - 14.8% less
Hot Ground/ DD - 600 gr. nugget at 100 cm - 25.9% less

Max. Depth/Mono - 5 grams gold ring at 75 cm
Hot Ground/ Mono - 5 grams gold ring at 62 cm - 17.3% less
Hot Ground/ Cancel - 5 grams gold ring at 60 cm - 20% less
Hot Ground/ DD - 5 grams gold ring at 56 cm - 25.3% less

Max. Depth/Mono - 5 grams gold bar at 60 cm
Hot Ground/ Mono - 5 grams gold bar at 50 cm - 16.7% less
Hot Ground/ Cancel - 5 grams gold bar at 48 cm - 20% less
Hot Ground/ DD - 5 grams gold bar at 40 cm - 33.3% less

Max. Depth/ Mono - 0.5 grams Australian gold nugget at 19 cm
Hot Ground/ Mono - 0.5 grams Australian gold nugget at 20 cm - 5.2% more
Hot Ground/ Cancel - 0.5 grams Australian gold nugget at 12 cm - 36.8% less
Hot Ground/ DD - 0.5 grams Australian gold nugget at 20 cm - 5.2% more

So according to the highest loss figure of 36.8% for that target in that setting the 21"CC coil will be equivalent in ideal case to a little over 17" Mono. In reality as GPX depth gradient is not linear the difference will be smaller and will be somewhere between 18-19" Mono.
The peculiar thing however is that 19" Mono will not necessarily compete well on the half gram nuggets. So this kind of calculation will probably fit better the bigger targets.

 

[Ded Driver]

600gr nugget? solid or speci? if solid that's near 20oz .. I wouldn't be advertising having that laying about the house!
interesting results on the % loss on gold

It's the Tin/Lead simulation nugget that I use for tests. The thieves are welcome to steal it.

tricked by the 'ol tin/lead nugget
I use them too, 60/40 solder

 

[washgravel]

There is a little inaccuracy in the percentage calculations you presented.

Maths was never my best subject as I thought I had figured out how you came to your %s then did the same for my results.