Depth Tests For Big Gold Nuggets.

[Baldy]

I heard that some big DD were on the way and I said to my self..mmmm Something is up..Very Interesting Guys..

 

[Candigger]

So the lesson is if you set up looking for fly s__t you won't hear the deeper lumps. Depth is all in the settings and how well you can cover the ground (if you walk fast you walk past)

It's always one or the other, never both at the same time. I strongly prefer the deeper lumps to the fly poo.

 

[Candigger]

Ok everyone is talking about DD vs mono coils for GPX. I wonder why no one is considering concentric coils for GPX or the PI detectors in general. Is there any downfall for the use of concentric configuration in PI?
Concentric would have TX the size of any mono and some RX inside that will provide some discrimination like with the DD.

 

[EVIE/BEE]

Ok everyone is talking about DD vs mono coils for GPX. I wonder why no one is considering concentric coils for GPX or the PI detectors in general. Is there any downfall for the use of concentric configuration in PI?
Concentric would have TX the size of any mono and some RX inside that will provide some discrimination like with the DD.

I don't know of a PI machine that has target discrimination. Maybe our Minelab agent will give us the technical reason why not.
I detected full time for several years and never walked away from a target without knowing what it was. Even when you know it's ferrous you still stick your magnet over the hole and it disappears.
I was only shocked once when i was 100% certain i had a gold target, waved the magnet and it disappeared. I checked the magnet moments later and found a piece of ironstone with a gram of gold encrusted in it. Gold does give a distinct response but the view is that the best discriminator is the operator... walk away at your peril.

 

[autitch]

Ok everyone is talking about DD vs mono coils for GPX. I wonder why no one is considering concentric coils for GPX or the PI detectors in general. Is there any downfall for the use of concentric configuration in PI?
Concentric would have TX the size of any mono and some RX inside that will provide some discrimination like with the DD.

Candigger, there aren't any commercial concentric coils available for ML GPX machines. You would need to build one yourself if you thought they would be of value.

AuTitch

 

[Candigger]

Ok everyone is talking about DD vs mono coils for GPX. I wonder why no one is considering concentric coils for GPX or the PI detectors in general. Is there any downfall for the use of concentric configuration in PI?
Concentric would have TX the size of any mono and some RX inside that will provide some discrimination like with the DD.

Candigger, there aren't any commercial concentric coils available for ML GPX machines. You would need to build one yourself if you thought they would be of value.

AuTitch

I know that there are no commercial CC available for GPX. I don't understand why. Everyone makes DD for some discrimination or for what ever other reason, but no one does CC. I find it puzzling.

 

[Candigger]

Ok everyone is talking about DD vs mono coils for GPX. I wonder why no one is considering concentric coils for GPX or the PI detectors in general. Is there any downfall for the use of concentric configuration in PI?
Concentric would have TX the size of any mono and some RX inside that will provide some discrimination like with the DD.

I don't know of a PI machine that has target discrimination. Maybe our Minelab agent will give us the technical reason why not.
I detected full time for several years and never walked away from a target without knowing what it was. Even when you know it's ferrous you still stick your magnet over the hole and it disappears.
I was only shocked once when i was 100% certain i had a gold target, waved the magnet and it disappeared. I checked the magnet moments later and found a piece of ironstone with a gram of gold encrusted in it. Gold does give a distinct response but the view is that the best discriminator is the operator... walk away at your peril.

I deeply share the same point of view, BUT the old timers have left piles of crap on many places. There can be more gold in there, if one can get around the trash. And did't Reg mention something about cans meter deep with his huge 38" mono.
I have seen a video from a couple of Ozzie chicks digging gold. So they have shown a pile of trash at least 20 targets that they have collected to get only to a couple of small nuggets. That seems pestering business to me as so much time is lost recovering bs instead of gold.

 

[Reg Wilson]

Recently saw a photo of a big slug (about 4 kilos) found not long ago at a depression era campsite in Victoria riddled with metallic rubbish. A six ounce piece led to a slow and meticulous clean up of the area, resulting in the recovery of the nugget. This was in a well known and supposedly 'flogged' big nugget site where the trashy area had been avoided for decades. The 'Beggary Lump' (86oz) was found at Wedderburn in a similar situation in the early eighties, and a 250 oz 'thumper' at Patchy flat near Dunolly in the early nineties.
Candigger, the 38" coil is a mono, so the edge of the coil can be used to pinpoint once the target is out of the hole. A pinpointer is handy for when the target is still in the hole.

 

[autitch]

Ok everyone is talking about DD vs mono coils for GPX. I wonder why no one is considering concentric coils for GPX or the PI detectors in general. Is there any downfall for the use of concentric configuration in PI?
Concentric would have TX the size of any mono and some RX inside that will provide some discrimination like with the DD.

Candigger, there aren't any commercial concentric coils available for ML GPX machines. You would need to build one yourself if you thought they would be of value.

AuTitch

I know that there are no commercial CC available for GPX. I don't understand why. Everyone makes DD for some discrimination or for what ever other reason, but no one does CC. I find it puzzling.

Its puzzling in deed that there isnt a CC coil for the GPX available and I sense there are commercial and not performance reasons why this may be the case.

Coil innovation has been very slow to come to market. ML stifled coil improvements for a long time by having a patent on the use of Litz wire which has now expired. The coil manufacturer that did licence the use of Litz wire during the patent period Im sure would have had specific conditions imposed on its use. Essentially, coils have changed little during ML Pi era. In recent time, the flat wound coils have been brought to market to compete with the latest ML machine platform. This flat winding coil winding technique and its benefits have been known for over 20 years however it was withheld from being available to the retail market for a very long time. One can only assume that this was done for commercial reasons as sales of existing technology coils continued to meet the commercial objectives of the coil manufacturers. During that time, there were no other detector platform on the market capable of disrupting the sales of the existing technology coils either. This is no longer the case since the arrival of the GPZ. Hence we are seeing some new coil development coming to market. These developments are going to be interesting as they have the potential to extend the practical life of the GPX machines.

Interestingly ML has practically prevented existing coil manufacturers from making aftermarket coil for the latest GPZ platform. One can only assume this has been done for commercial reasons as they seek not to have any competing coil technology disrupting sales of their flagship detector.

 

[ozziegold]

Recently saw a photo of a big slug (about 4 kilos) found not long ago at a depression era campsite in Victoria riddled with metallic rubbish. A six ounce piece led to a slow and meticulous clean up of the area, resulting in the recovery of the nugget. This was in a well known and supposedly 'flogged' big nugget site where the trashy area had been avoided for decades. The 'Beggary Lump' (86oz) was found at Wedderburn in a similar situation in the early eighties, and a 250 oz 'thumper' at Patchy flat near Dunolly in the early nineties.
Candigger, the 38" coil is a mono, so the edge of the coil can be used to pinpoint once the target is out of the hole. A pinpointer is handy for when the target is still in the hole.

Hi Reg,

Yes I did hear about that one from near Dunolly, late last year.

But have you heard about or seen the photo of the 8 Kilo long slug found after that one.

Tarnagulla district I hear??

Cheers ozziegold

 

[EVIE/BEE]

It depends on you're motives Candigger. It can be satisfying to find gold amongst the rubbish. You know no one else can be bothered, all the better for me. :goldnugget:

 

[Redfin]

.

Tarnagulla district I hear??

I heard a couple

 

[Reg Wilson]

The photo I saw was of a long slug that looked like it may have been acided. It looked pretty clean for gold that I have seen from that area. I do not doubt that it is authentic, but did not hear of a larger piece.

 

[Redfin]

Gossip at the Bakery Reg,

 

[Candigger]

Its puzzling in deed that there isnt a CC coil for the GPX available and I sense there are commercial and not performance reasons why this may be the case.

Coil innovation has been very slow to come to market. ML stifled coil improvements for a long time by having a patent on the use of Litz wire which has now expired. The coil manufacturer that did licence the use of Litz wire during the patent period Im sure would have had specific conditions imposed on its use. Essentially, coils have changed little during ML Pi era. In recent time, the flat wound coils have been brought to market to compete with the latest ML machine platform. This flat winding coil winding technique and its benefits have been known for over 20 years however it was withheld from being available to the retail market for a very long time. One can only assume that this was done for commercial reasons as sales of existing technology coils continued to meet the commercial objectives of the coil manufacturers. During that time, there were no other detector platform on the market capable of disrupting the sales of the existing technology coils either. This is no longer the case since the arrival of the GPZ. Hence we are seeing some new coil development coming to market. These developments are going to be interesting as they have the potential to extend the practical life of the GPX machines.

Interestingly ML has practically prevented existing coil manufacturers from making aftermarket coil for the latest GPZ platform. One can only assume this has been done for commercial reasons as they seek not to have any competing coil technology disrupting sales of their flagship detector.

I suspect the reason may be different, or at least not only marketing wise.
As I have seen ML DD coils they are balanced to near perfection, just like for IB detectors.
Now the trouble that I see with CC for GPX is that if a CC is to be balanced to perfection, first of all this is nearly impossible as CC are far more difficult to balance to very small offset than DD's.There is also the need for a feedback loop from RX to TX that is required to balance CC. This feedback loop will eventually form a coupling capacitance with TX and this coupling capacitance could be the limiting factor restricting CC from working with GPX as ML's are super picky on what coils can work with them.
Well this is my little electronic view in the matter. Perhaps someone more educated on PI gear will shed some more light.

 

[Reg Wilson]

Redfin, Ah, the bakery. Best coffee scrolls this side of the black stump. Pies are pretty good too. Brings back memories of when I lived at the Railway hotel for a year, back in 1990. Dave Chappell was the publican, a damned good bloke who can still be found at the pub on the odd occasions, chatting with the locals and reliving old times.
Found a lot of gold and had the best times of my life, with great friends.

 

[Reg Wilson]

Jim Stewart did a lot of work with big coils, and a DD that he took to WA failed to come up to expectations, because it had to be moved over the target so slowly to get a response that it made it impractical where as large monos tested at the same time and place performed much better as they had a better 'coil speed'.

 

[Redfin]

I still have a garbage bin lid that Jimmy lent my FIL.
Great bloke.

 

[Ded Driver]

Candigger, there's a reason for everything in the universe, and no doubt the coil manufacturers out there would have explored Concentric Coils on PI machines some time ago.;
here's at least a part of an explanation from Garrett.com
"Concentric
The concentric configuration consists of a TX coil and RX coil which are usually circular and
arranged as shown at left. The advantage of this configuration is that both the TX and RX coils
are wound as large as possible within a given searchcoil diameter. This provides the largest
possible detection field and greatest detection depth, making the concentric coil potentially
the most sensitive configuration available.
In addition, concentric coils also provide the most symmetrical detection field, allowing ease
in pinpointing and consistency in target identification. For these reasons, they are the most
commonly used searchcoil and will provide the best overall performance in most environments.
Unfortunately, this configuration is the most susceptible to interference from ground minerals,
which results in substantial loss of performance when used over heavily mineralized ground."

Note that this article appears to be mainly talking about treasure/relic detectors (vlf)

full article
https://www.garrett.com/hobbysite/pdfs/searchcoil_tech_sheet.pdf

 

[Candigger]

Unfortunately, this configuration is the most susceptible to interference from ground minerals,
which results in substantial loss of performance when used over heavily mineralized ground."

This is true only for CC used with VLF detectors and it is related mostly to interference with ground conductivity.In dry mineral conditions the CC used on VLF are actually a lot better than any other coil regarding small targets. Example - the Nautilus from USA.
PI got nothing to do with VLF. So the question regarding the lack of CC for PI machines on the market is still widely open. Ears burning here.