Why cant my GPX4500 pick this gold up?

[filternozzle]

I have a small part of a very thin 9ct gold ring, 3/4" in length and weights 0.31g. What I would like to know is why my GPX cant pick this up at all? I have tried every Soil timing, and adjusted RxGain, Stabiliser and Target vol. GB on and off, Discrim on 1 and turned off. 10x5 DD coil in DD and Mono, 11" AI coil in DD and Mono and finally a16" Mono. All to no avail. I have a friend who tried with a TDI Pro using a 14x10 Razerback coil could get it with GB on and off. Best performance with it off. Can anyone give an answer? Could it be anything to do with the fact the GPX doesn't pick up coke?

 

[narrawa]

At a guess id say it may well be the angle your waving it over the coil??....sounds silly i know, but long thin items have a tendancy to do this on the PIs. Presented to the coil on one angle and its not seen...changing the angle 90% should give a positive signal. When i say long....3mm x 1mm on the GPX range will signal better in one direction/angle than another.

Use a small to medium mono coil in one of the smooth timings, which are optomised for small gold and FP the detector. Factory Preseting the detector is one way of eliminating user error.

 

[steve herschbach]

Is there a break in the ring? If not, the GPX should easily pick it up laying flat. If the ring has a break in it, that is another story.

 

[filternozzle]

This is part of the ring, it has been flattened and measures 20mmx2x0.5mm. I have tried all the timings , I have tried all angles and even touching the coil. I have tried FP and other settings. The coils used: 10x5" DD, 11" Anti Interference, 11" DD, 16" Mono. I could not raise any sort of response at all.

 

[narrawa]

Try cutting up a pull tab to mimick the size and shape....if that dont work than its off to Minelab.??

 

[filternozzle]

Try cutting up a pull tab to mimick the size and shape....if that dont work than its off to Minelab.??

I'm confident there is nothing wrong with the detector. Those out there that have a GPX might like to replicate with 9ct gold or a similar conductor that measures 20mmx2mmx0.2mm and post their findings.

 

[steve herschbach]

What do you mean part of the ring? I still need to see exactly what we are talking about. Got a photo?

You can stop with all the coils and settings unless you are having fun. When did you get the 4500? How long have you used it, and have you been sending things successfully with it?

 

[filternozzle]

What do you mean part of the ring? I still need to see exactly what we are talking about. Got a photo?
You can stop with all the coils and settings unless you are having fun. When did you get the 4500? How long have you used it, and have you been sending things successfully with it?

I found the ring in the wet sand on a beach, it was badly damaged in that it was squashed up. I cut a section out of the ring and flattened it and the dimensions are as described. I will take a picture and see if I can upload later. I have been using the GPX4500 regularly as my first choice of detector since February 2012 both inland and on wet sand beach. My other machines are the Nautilus DMC IIB which I use when the GPX is not, also have the CTX3030 which only gets used if I'm detecting in the rain.

 

[steve herschbach]

Sorry for all the questions but I just wanted to establish you have had the GPX 4500 a while and that it is working correctly, which does indeed appear to be the case.

If you have cut a section out of it and it is no longer a hoop but is now a wire then it all makes sense. Lots of detectors have a problem with that.

http://www.findmall.com/read.php?26,941386,941386

http://www.findmall.com/read.php?18,1008602

 

[filternozzle]

[attachment 260606 0.31g9ctgold.jpg] Here is the photo Steve Weight 0.31g

 

[filternozzle]

If you have cut a section out of it and it is no longer a hoop but is now a wire then it all makes sense. Lots of detectors have a problem with that.






I agree with you Steve, I was just asking why is it the TDI can get it but not the GPX??

 

[steve herschbach]

The TDI does pretty well on small stuff. Not all detectors are perfect at all things. But some excel one way or another.

Use your smallest mono coil. Soil timings on sensitive, fixed tracking. On the menu select sensitive extra, Audio QUIET. Gain 12, motion very slow. By running the audio in quiet and using the very slow motion setting you can reduce the EM interference and minimize ground noises. The tiny targets then stand out loud and clear. If there is still some EMI or ground noise reduce the gain a little.

I am not saying this will work as there may be something about that particular piece the purity and the shape that the Minelab does not like. But these settings are hot on small stuff.

 

[filternozzle]

The TDI does pretty well on small stuff. Not all detectors are perfect at all things. But some excel one way or another.
Use your smallest mono coil. Soil timings on sensitive, fixed tracking. On the menu select sensitive extra, Audio QUIET. Gain 12, motion very slow. By running the audio in quiet and using the very slow motion setting you can reduce the EM interference and minimize ground noises. The tiny targets then stand out loud and clear. If there is still some EMI or ground noise reduce the gain a little.
I am not saying this will work as there may be something about that particular piece the purity and the shape that the Minelab does not like. But these settings are hot on small stuff.

These settings may be hot but not hot enough to get a response on this target.
I have a friend some distance away who owns a GPX5000, he has tried on a similar sized 9ct gold bit, using the 11" mono, his results are the same as mine.
So it would appear its the shape that is the problem.
I still think there is a tie up with the fact the GPX doesn't pick up coke in the ground, which is a low conductor, and not picking up this shape/size of gold.

I owned a TDI Pro before taking on the GPX and much prefer the GPX. However, hats off to the TDI because it gets this bit of gold very well even with a coil as large as 14"x10".

 

[steve herschbach]

This item is probably reading like a ground target and being eliminated by the ground balance. The same system that eliminates a coke reading. Your friend with the GPX 5000 can turn off the ground balance on his unit - see page 55 of the owner manual. I would be very curious to see if that allowed your little piece of gold to be detected.

If you read my detector reviews at Steve's Guide to Gold Nugget Detectors you will see I consider PI detectors as big guns for big targets. An over simplification for sure, but this highlights why I typically switch to VLF when chasing tiny stuff. Still, it has to be the shape and low purity here hurting you as I have seen a GPX find smaller nuggets than that. But they are round, which detectors like, and much higher purity.

The TDI does have a manual ground balance (wish I could do that on my GPX) and at the smallest delay setting can hit pretty small targets, and you found a scenario that highlights this. Proving once again no one detector does everything perfectly.

 

[filternozzle]

This item is probably reading like a ground target and being eliminated by the ground balance. The same system that eliminates a coke reading. Your friend with the GPX 5000 can turn off the ground balance on his unit - see page 55 of the owner manual. I would be very curious to see if that allowed your little piece of gold to be detected.
.

I'll get him to check with the 5000. However, I have tried with the Ground Balance 'on' and 'off' with the 4500 and we know the result. The TDI could get it with the ground balance both 'on' and 'off', which is pretty good. However, I still prefer the GPX for its overall performance.

 

[steve herschbach]

Oh yeah, I have run both the GPX and TDI a lot, and am an early TDI booster. White's TDI Coin Settings

I still like the TDI for in town use as it is so resistant to EMI. But when it comes to sheer depth it beats the TDI hands down. I do wish White's would come out with a waterproof version of the TDI, but last word was it is not to be. Maybe something better?

Bottom line is I will be swinging a GPX all summer, not a TDI.

 

[iron bark]

Hi all the setting steve said are good the only other thing is to run the target volume between 9-12 the higher you run it the noisier the detector is .With 4500 they are all different you can set 2 up all the same and 1 will run quiet and the other will be noisy so just have a play with the settings, are you using headphones or a speaker

 

[filternozzle]

Hi all the setting steve said are good the only other thing is to run the target volume between 9-12 the higher you run it the noisier the detector is .With 4500 they are all different you can set 2 up all the same and 1 will run quiet and the other will be noisy so just have a play with the settings, are you using headphones or a speaker

I always use earphones and generally have Target Vol between 10-12 - Always run with soft smooth threshold. I do believe its just one of those things, that particular shape and size is difficult for the GPX. Having used the GPX as my main detector regularly since Feb 2012 I am very happy with the overall performance and it will remain my first choice. I started this thread to try and find out the reason why the GPX cannot get this target as the TDI can grab it with no problem, it must be something to do with the way the GPX works.

 

[iron bark]

Yes I under stand once i found brass button that blanked out with a DD it was on a extreme even sent it to ML but as you say the shape and material good hunting