GPX 4500 - Big target

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GPX 4500 - Big target

Post  Alain Soral on Thu Mar 02, 2017 1:18 pm

Hello,

I am alain soral, I am new in this great forum, I currently live in Morocco, but I am of Belgian origins. Here where I live, people run behind a slightly different objective, it is the big treasures buried by the ancient tribes (jewel-box, crock, Gold Statue ... etc).
In order to take our chance we have brought our GPX 4500, then the problems begin, the fact that our machine is designed to find also gold nuggets, each time we were forced to dig, picked up and eliminate all the targets of Small size (ring, corner, small pieces of aluminum ... etc), afterwards we look for the objects wanted (big target).
We are looking for a solution to ignore small targets.
A friend told me that it takes a frame coil (1mx1m or more), to find only big targets, it has a machine with frame (Lorenz deep max), but after some research we concluded that Minelab does not offer this type of coils for their machines. Even the largest coiltek 20x40 coil can detect small unwanted targets.
I read almost the whole forum, but I could not find a solution for this problem. Please suggest a suitable solution to ignore small targets.
Any intervention, would be welcome.

Cordially.

Alain Soral
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Re: GPX 4500 - Big target

Post  colour on Thu Mar 02, 2017 2:47 pm

If the ground conditions allow, salt-course timing with a large dd coil might help. Using this timing may result in a slight loss in signal response to smaller targets. Would also drop the stabilizer to 3 or less and adjust gain to suit conditions.
Happy hunting.
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Re: GPX 4500 - Big target

Post  deutran on Thu Mar 02, 2017 6:02 pm

Hi Alain
I would suggest very low Rx/Stab maybe 3-2 and run a large round mono high off the ground.
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Re: GPX 4500 - Big target

Post  Alain Soral on Fri Mar 03, 2017 10:54 am

Thank you for your quick response, we followed your advice, using a DD detech coil 21 '' x17 '' sef, with salt coarse mode, stabilizer 3, and gain 8,
But we still detected an alluminium bullet, and a piece of copper 0.5x0.5 cm. Thank you for your cooperation but the given solution did not work. If you have any ideas, do not hesitate.
Because I think this is the first item, which deals with this type of problem. And I trust this forum to settle this concern
thank you.

Alain Soral
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Re: GPX 4500 - Big target

Post  Alain Soral on Fri Mar 03, 2017 11:00 am

We also tested the 2nd solution, with a coiltek mono 22 '', but without success, the two solution did not work, other suggestion please

Alain Soral
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Re: GPX 4500 - Big target

Post  davsgold on Fri Mar 03, 2017 3:49 pm

G'day Alain Soral

You could try the largest DD coil you can get and run it in cancel mode, don't do this with a mono coil though as you won't get any targets to respond except very large at a very close distance.

cheers dave
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Re: GPX 4500 - Big target

Post  deutran on Fri Mar 03, 2017 5:38 pm

Alain Soral wrote:We also tested the 2nd solution, with a coiltek mono 22 '', but without success, the two solution did not work, other suggestion please
Hi Alain
I actually thought to use the 22" so I'm out of ideas.Maybe pm Jonathan Porter(JP) he'll have some idea.
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Re: GPX 4500 - Big target

Post  adrian ss on Fri Mar 03, 2017 7:15 pm

I suggest that the GPX4500 is not the correct detector for the job you are trying to use it for. They are not supplied with the coil size that you require for the depths that you are searching. They are designed to find small shallow gold and large deep gold  to around 3 foot max and  have timings and coils to suite that task.

The Lorenz and large frame coil would suit your purpose better, although these coils will miss a lot of individual valuable small gold items...unless they are contained in a large metal strong box or something similar.

Maybe trade the 4500 in on the correct tool for the job.
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Re: GPX 4500 - Big target

Post  deutran on Fri Mar 03, 2017 7:23 pm

Hi Adrian
I was thinking the same thing but figured after outlaying that sum for the 4500 there might be a solution for them.
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Re: GPX 4500 - Big target

Post  adrian ss on Fri Mar 03, 2017 8:35 pm

Doesn't one of the Minelab tectas have a Blanking feature to eliminate near surface targets??

Maybe you should use something like the:
Pulse Star 2.
Lorenz.
SSP5100
These are all supplied with large coils and operate at a low PPS for very deep penetration on large items.

You can also email Minelab Australia directly. They are very helpful.
service@minelab.com.au
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Re: GPX 4500 - Big target

Post  geof_junk on Sat Mar 04, 2017 7:14 pm

The targets you get and wish to ignore are small surface (less than 30 cm deep) bit. I would use a large DD coil and swing the coil over a signal if it is narrow signal, lift the coil 30 cm up if it disappears it surface junk. What you are after is a wide signal. I have done this locating Plastic pipe that had a brass Y - junction that was 75 cm deep in a farm. By the way this is the opposite of what lazy gold hunter do. As has been said there is other types of detectors even the two box coil type that is more suited for your task.
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Re: GPX 4500 - Big target

Post  adrian ss on Sat Mar 04, 2017 8:00 pm

I have a Whites  TM 808. It does find large items quite deep and does not respond to small surface rubbish and is not to bothered by ground mineralisation. It does have Ground balance control.

In use the coils of this detector are held at around knee hight above the ground, which is no doubt the reason it does not respond well to small surface rubbish or ground minerals.

The deepest item I have detected with mine was at approx 4 feet. The depth  determined by the method described in the user manual. I did not recover this item out of respect for my back plus I did not have a suitable digger for the job.
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