Dutchman4

1 hour ago, Skookum said:

I’m still struggling with depression from the loss of the plans for smallest 8x6 NF coil. 

I have the 12x7 Exceed and it has more than enough sensitivity so the only reason IMO to get a smaller coil is for access into small spaces.

I am considering to build my own battery pack for GP3000.

I plan to eliminate the Coiltek Battery/Regulator unit.  It appears the OEM battery supplies 6V and the Coiltek Battery/Regulator recommends 6.7V for GP series.  I can choose to use Lithium-Ion battery cell at 3.2V with two in series producing 6.4V or choose Lithium-Polymer battery cell at 3.7V with two in series producing 7.4V.  My question/concern is that a fully charged Lithium-Polymer cell can reach 4.2V so twice that is 8.4V so is that too much voltage to supply directly to the GP3000?  I assume the GP3000 has an internal regulator for the incoming battery supply.   

I  just looked in my GB-PRO-DP manual and it shows only one washer for the 5" round and also the 11" oval.  Not sure about the 5x10.

Despite the problem it still appears to be useable though.  From the looks of the fail pattern it could be a display driver or cable problem also, maybe?  Maybe a gentle reseat of the cables could resolve it.  The screw heads in the picture appear to be corroded like this was a salt water beach machine.  Good luck.

So I picked up a GP3000 a few days ago including an assortment of coils.  This NF 17x11 is the only mono coil in the bunch and it appears to be an older model with a fiber glass body.  Do any of you old timers have any experience with this coil regarding depth (on 2g+ nuggets) and stability vs the more modern coils?

1 hour ago, Drillerdave said:

Ceril, you are welcome to borrow my 7000 and/or the 5000 to see for yourself if they are any advantage to you on your patches. The 7000 has both the stock and 19” coils and the 5000 has many coils. The largest Evolution is 12” 

That is generous of you Dave and I may take you up on that offer when I make a return trip to the patches.  At least it will settle my mind on what could be at depth.

39 minutes ago, kingswood said:

Thats pretty cool.

A 3000 with a 24x12" ufo mono may be worth swinging over those areas.

Kingswood,

I see in your list that you own the GPX6000 and GP3000 so you would know if the GP3000 with the 24x12 ufo mono would have a depth advantage over the GPX6 on larger gold.  If this advantage is minimal then I will just get the 17x13 mono for the 6000 and hope it adds some depth over the stock 11.

3 hours ago, Rob Allison said:

Hi Ceril,

    Over the last 20 years, there has always been discussion on older PI's going deeper with larger coils.  Normally, someone would get a unit modded more for depth and use a large coil.  The 2 detectors I always heard were the best for overall mods were the Minelab GP 3000 and GP 3500, but there is much debate even on these.  

I'm not sure who stated the Minelab 17" elliptical would only get like 1 inch over the stock 11 inch, which I find that very hard to believe.  Also, there are so many depth exaggerations out there, I would say you would get a bit more depth on a sizeable nugget like 1/4 or better.  

Rob

Hey Rob,

So it appears you are saying that a stock GP3000, with the right coil, wont have a significant depth advantage over a 6000 with the 17x13 coil, on 3g+ nuggets.

1 hour ago, kingswood said:

Yeah i had the same thought too 🙂

If convinced its virgin ground, then would be interested to know the depth the larger bits found with the 6000 were found at.

It is obvious to me that these patches are virgin ground since I am finding multiple nuggets up to 2.5 grams in size that should have been found by any PI machine and probably most VLF also.  

The average depth of these nuggets was 5 to 10 inches.

I have a GPX6k that I have had good success with over the last few years.  I have found several patches that yielded in the range of 8 to 15 nuggets each with biggest ones at 1.7g and 2.5g.  I have considered going back to these patches and start layering off the surface to gain more depth but that sounds like a lot of work.  I have also considered getting the 17x13 coil for the 6k to gain more depth but the reported depth gain appears to be only about 1 inch over the stock 11 coil if that is true.  Another option I am considering is to purchase an older Minelab PI and combine it with the best coil for depth, so that I can use it to go over patches (that I have cleaned out using the 6k) to find larger (3-5g and larger) nuggets at depths deeper than the 6k is capable of.  So just to be clear I want a machine that is dedicated/configured for increased (at least 3+ inches deeper than 6k) depth on larger gold, has a stable threshold and the ability to handle ground mineralization and hot rocks better than the 6k.  It does not need to be an all around machine that can also find smaller shallow gold since I have the 6k for that, but if it can then that would be a bonus.  I want to limit my budget to a max of $1500. 

After some research and input from friends I have been advised to consider the following models:

SD2200D - Reported to be one of the deepest machines Minelab has made.  Apparently the extra depth is due to the detector power supply being unregulated and the full voltage from the battery is available to the coil.  Are Lithium battery packs, either commercial or home made, adaptable to this machine?  On an unregulated machine I would think that a lithium battery would be preferred.  At the same time I read that using mono coils on this detector is not practical because they generate too much ground noise and to use DD coils instead.  A DD coil cuts the width of the coil in half with an associated loss of depth so I am confused how this machine can be deep when only using DD coils unless very large DD coils are recommended.  I would like to limit max coil size to between 15-18" round.  I would prefer to limit cost to between $600 and $900 on such an old machine in case it dies and the faulty component is no longer available.  I have the skills to troubleshoot to the component level and make repairs on older "through hole" technology PCB's as long as the components are marked and available.  What is the best coil for depth on this machine?

GP3000, 3500 - I dont know much about these machines and if they would meet my requirements for depth, stability, etc.  Would this be a better choice than the SD2200D?  What is the best coil for depth on this machine?

GPX4500, 4800, 5000 -  A GPX4800 or 5000 with a NF 15" round evo mono coil (or similar) looks to be the best and the most expensive option.  I might have to look for a long time to get a below market value price on one.

Please advise,  regards,  Ceril

The discovery of the crash site is quite a story.

Thanks for sharing,  Ceril

The next ones will come easier, at least it did for me.  Keep it up.

Interesting way to store electric energy

I'm still of the opinion that if you own a 6000 then you don't need an Axiom and also the other way around.

9 hours ago, GotAU? said:

Buy your glasses soon- they sell out fast and unfortunately the price gouging has already started.

I was in Idaho for the 2017 eclipse and it was wonderful.  Better in person than on television for sure, everyone should see at least one in their lifetime!  So this one will be number three for us including the annular eclipse that passed through Utah a couple years ago. We are going to be west of Waco on a friend’s ranch for it- and have the week off for spring break to take our time coming home. Will be traveling through New Mexico and AZ and hopefully will have some time to use the detectors along the way home too.

I used a Baader solar filter on my lens for the three bright solar images I took leading up to totality, if you zoom close, you can see sun spots on the sun.   No filter was necessary on my camera nor to look at it directly during totality on the last photo to the left.

 

I was up in Spokane, WA for that 2017 Eclipse also.  It got quite dark and cooled off considerably.  We were in park next to a river and as soon as it started getting dark the Canadian geese' that were sunning themselves on the grass, walked to rivers edge and swam over to an island to roost for the night.  Then some minutes later when the sun came out again they came back on shore and resumed sunning.

I lived in Mesquite, NV for 3 years and joined GSSN club, they have claims in Gold Basin/Lost Basin, AZ and also in Johnnie, NV.

I found some nuggets in Gold&Lost Basins but it was one of the harder areas to find gold for me.  I had better luck on the Pale Burro claim in the Johnnie district and the surrounding areas. 

I'm 5' 10" and measured 19.25 inches.

Two different scenarios are being described here:

1.  The original question was "what would happen if one was to turn a PI on without a coil connected?"  In this case I would also expect that nothing would or should happen because there is no load (coil) and there should be no current flow.

2.  What would happen when "hot swapping a coil" or better said swapping a coil when the detector is turned on.  In this case the load (coil) is being disconnected and/or connected with the detector on and hopefully the detector is designed to withstand this but I would consider this risky with any piece of electronic gear that has an external load connected with a cable or wire. 

On 1/27/2024 at 1:28 PM, phrunt said:

Plenty of electronics were built to last, especially old Japanese equipment, I have 20+ year old amplifiers that work as good as the day they were made and plenty of other old electronics still working fine, even an original Pac Man handheld game from the early 80's, I have original Xboxes, about 10 of them from 2001 to 2005 in age that are still going strong, all I've had to do is replace the lasers on some that certain brands were prone to pack up, and change a few capacitors that die with age and remove the leaky clock capacitor that Microsoft could have used on purpose as a ticking timebomb to kill all old Xboxes as it will kill them all if not removed. 

The early GPX series detectors are rock solid, great quality PCB's, with the parts like switches that can wear out easily replaced with parts from a local electronics store.  I think they'll be going strong for decades to come yet if looked after, kept away from moisture and salt although the painted PCB's also help with that, so that's an added bonus to Minelab trying to protect their design by the crude painting method 🙂

I have refurbished 80's vintage high end audio amplifiers by replacing ALL the electrolytic capacitors and they will work brilliantly for another 20 to 30 years.  Electrolytic caps age, leak, swell and degrade over time.  

Thanks for the suggestions but I have found all my gold in dry and mostly comfortable conditions and prefer it this way.  I could make an exception if I was missing a significant amount of gold by choosing to hunt only dry ground but it appears from most comments that dry ground provides the best overall metal detector performance for both VLF and sensitive PI like the 6K.

Prospecting is a recreational hobby for me that lets me enjoy the outdoors at the same time.

I wouldn't plan a camping trip or a day at the beach if it is forecast to be wet or windy and it's the same for me regarding prospecting.

Now I am a bit confused, there is JP's very detailed technical explanation of how "conductive ground" can negatively affect detector performance and at the same time there are (non-technical) observations in the field that support the opposite result.

17 minutes ago, phrunt said:

or in mild ground they enhance performance.  Nothing is more exciting here than hitting a gold area after fresh rain, rains pretty infrequent in my gold areas however once a good dumping has taken place the ground lights up.

Is this because of the mechanics of water erosion removing overburden or is there a technical explanation?

1 hour ago, RONS DETECTORS MINELAB said:

All soils can react differently, I would say try lowering the gain and see if you can get a smooth threshold, if no success then try the DD coil.

A large signal should stand out from ground noise in most cases, but not all.

Thanks Ron,

My real question is this:

I don't like to metal detect for gold during or after it rains in the desert for a number of reasons but mainly I don't like to dig and recover targets in wet or damp soil and I don't like to walk around with muck on my boots.  I am retired so I can choose when to go prospecting based on if I like the weather or not.

So I just want confirmation that some wet or damp soils can increase ground noise, requires lowering of the gain and results in reduced depth and performance.  From your response it appears that you confirm this to be the case and this will be yet another reason for me to plan my prospecting trips so as to avoid wet or damp soil when I can.

On 1/9/2024 at 12:22 PM, 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

So based on this information, am I correct to think that using the 6000 (with a mono coil) in wet or damp soil, from lets say a recent rain event in the deserts of the western US, would hinder the performance of the detector and it would be best to wait some days for the soil to dry out again?

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