Detector Depth Testing - Larger Gold

[Deepseeker]

I can't wait to see the results of whichever method/target type you use Nenad. I know the 5000 with the NF 25-DDX coil will ping an ounce of round lead deeper than a Z with a 14" coil on it in Normal, but I've never seen a comparison with the Z with the 19" coil or a large aftermarket coil on it. Having said that, a hackly piece of the same weight may prove the Z far superior?

I guess there's always the nagging questions in my mind too about how do you compare something that only has a Normal/Difficult choice of settings, to something like the 5000 that could be using Normal/Sharp, and a multitude of other tweaks as well? My ultimate dream-test comparison though on large deep targets, would be between the 5000 running an 80cm Detech concentric, and a Z running its deepest possible coil and settings combination. I'm thinking about springing for a Detech 80cm concentric for the 5000, but if something could convince me that the Z was capable of more, I would seriously consider a Z instead. Mrs D and I are fortunate enough to have just purchased a small part of the old Berlin Flat goldfield. A flat, deep part where a couple of biggies were found back in the 1800's, and my fetish with big and deep is burning more than ever. I just want to ping one ridiculously huge one before I kick the bucket, and if I have to dig my own deep grave to find it then so be it :goldnugget: :inlove:

Any controlled comparisons would be great to see :Y:

Deepseeker, I'm convinced that if you want to seek out larger nuggets stick with your 5000. We're not very social out there in the goldfields or anywhere else for that matter but we do meet quite a few people and occasionally share campsites with other prospectors. I've been watching closely since the GPZ7000 turned up and without doubt we consistently bring home more deep larger nuggets with the GPX4500 than anybody else we've come across swinging a 7000 in the same conditions.

Thanks Moneybox, that is very comforting to hear. And, Goldtalk Leonora I think Phasetech's heading sums it up, basically it's just about the best way to go about a maximum depth test with different coils and detectors, his biggest requests being for comparisons on large deep targets.

I know depth isn't everything, and I do remember J.P once making a comment about not understanding people's fascination with depth. I do get that- there are of course far more small nuggets in most goldfields than there are large ones, and indeed even though I've never detected in WA, from what I've read on here and other forums it does seem that most gold is found relatively shallow there. But some goldfields, like around Rheola in Vic for example, there mostly aren't any "patches" or "runs" to follow, and panning won't reveal much to you either. Sure, nobody with a handheld metal detector is going to ping the 9 foot deep ones that historically seem to have been a rather common depth for seriously big finds around that area, but there were also plenty found at shallower depths that by metal detector standards in general is still very deep.

 

[Deepseeker]

:lol:

One of my targets is a gold wedding ring from a past marriage - burying it is somehow therapeutic.....

 

[Big Johno]

Hi Nenad,
You made an interesting point that has raised my interest, point being use a target suspended above the coil being swept on the ground. I find that fascinating so today Im going to detect until I find a target, carefully measure the max height of the coil over the target, dig the target record the depth and add to the max height, then place the target on the ground and try your idea of sweeping the ground under the suspended target and see if the distances are the same above the ground as below the ground in undisturbed soil. I had never thought to try that, be fun. It would soon give credence to how accurate air testing is. Also as we all know so many variances make a difference to testing but if its just to use as a comparison on the performances of coils and machines then any method is OK really.
Cheers Johno

 

[Big Johno]

OOPS TYPO ERROR,
Meant to say "place target above the ground and swing coil below" layful: :8
cheers johno

Hi Nenad,
You made an interesting point that has raised my interest, point being use a target suspended above the coil being swept on the ground. I find that fascinating so today Im going to detect until I find a target, carefully measure the max height of the coil over the target, dig the target record the depth and add to the max height, then place the target on the ground and try your idea of sweeping the ground under the suspended target and see if the distances are the same above the ground as below the ground in undisturbed soil. I had never thought to try that, be fun. It would soon give credence to how accurate air testing is. Also as we all know so many variances make a difference to testing but if its just to use as a comparison on the performances of coils and machines then any method is OK really.
Cheers Johno

 

[SteveG]

Sorry but I don't see the point of using coins as targets, unless you are trying to detect coins.

 

[user 12139]

So, I am planning some videos for this year, and the two videos that have been most requested are:
1. A very small gold shootout type video
2. A larger gold shootout (this is by far the most requested)

I have been wanting to do a larger gold shootout video for some time, but the problem I see is that every gold target is unique, and the detectability of two 10 gram bits can be very different, depending on purity, density, shape, texture etc. Also, how to present the targets. So I'd like to discuss and get your thoughts.

With targets, I think using a consistent benchmark is probably the most meaningful, and I was reading some very old posts last night and came across a post where it was suggested that an Australian 50c coin is the closest to 1 ounce gold (on average). The beauty of this is that others can repeat the tests and while there will be other variables, at least the targets will be consistent. There has already been playing with 50c coins last year, so I think that is a well established reference.
The 5c coin is another good one, and I have used a 5c coin as a quick check on GP/GPX machines for years. Using an 11" Mono, about 36cm on a GP machine, 37/38cm on a GPX 4000/4500, and up to 39cm in Fine Gold on the 5000. (These are all just from memory, haven't really checked in a while).

So, 50c, 5c, and the logical one in between is the 10c coin.

Now how to present targets. There are advantages and disadvantages of all of the following methods:

1. Ground balance and place coil on ground and sweep target over the coil - probably the easiest, but doesn't take ground signal into effect, apart from the initial ground balance.

2. Dig a hole and bury the target at a specific depth - main problem with this is not being able to alter the target depth. Also a little time consuming digging multiple holes, and also each hole is in different ground.

3. Dig a trench at an angle in the ground, place a tube in there and push the dirt back in. This is a good method apart from the fact that a section of the ground is disturbed. But at least all surrounding ground is still natural, and you can alter the target depth very easily

4. The other method which allows sweeping the coil over the ground with zero disturbance, but still allowing you to alter target depth is by suspending the target above the coil. The coils search field is still doing the same thing it normally does, and whatever is happening to the field under the coil should be the same as above it.

I think 4 is probably the best, and the good part is that is can be done anywhere with relative ease, just need a simple method of suspending the target - even a leaning tree branch will do. Just not sure how others feel? Would you be happier with option 3 with the target under the dirt??

Keen to hear your thoughts on this, and is there another common target I should use? I don't want anything super big.

IMO, if your looking to find gold, then test using gold. Otherwise take up fishing or coin collecting.

If you dont use gold;
1) you cant distinguish which detector or coil combo best deals with gold permeability, porosity and host impurities.
2) you'll compare nothing but the detector or coil combo reactance to signal size and any slight ground variance between targets

As for target presentation, do it where you expect to find gold... and all targets in the ground, just as you expect gold to be when you find it. Any test where its not a true representation of this is in my book pointless

 

[PhaseTech]

Hi Nenad,
Also as we all know so many variances make a difference to testing but if its just to use as a comparison on the performances of coils and machines then any method is OK really.
Cheers Johno

Exactly.

Thanks Moneybox, that is very comforting to hear. And, Goldtalk Leonora I think Phasetech's heading sums it up, basically it's just about the best way to go about a maximum depth test with different coils and detectors, his biggest requests being for comparisons on large deep targets.

Yes, for my own interest as well, but when I look at my YouTube stats, comparison tests are the most popular by far.

Thing with spherical weights is that it is astounding how quickly the weight increases with the "size" even though we all know it is simply going up proportional to cube of diameter. These are a bunch of fishing sinkers so all 6.5 mm & above will have a 2mm hole thru them. All below have a split.
Also the detectability is based on the surface area and conductivity of the target not the density or weight so whilst a sphere of say 30mm dia might weigh 8x the weight of a 30mm coin it would only be detected maybe 50% deeper

Very true. People would probably get very surprised at the depth you can detect a 140g lead ball, i.e. they would expect it to be detected a lot deeper. But that is kind of the point of doing this.

Sorry but I don't see the point of using coins as targets, unless you are trying to detect coins.

As I said, coins are a known and consistent target, so are better for comparative testing. Whereas with gold, a 1g nugget can be more detectable than a certain 6g piece. So if I do a test with a 6g prickly reefy bit, and get poor depth, someone will go out and test a 6g lumpy piece and get it heaps deeper and think, oh that Nenad doesn't know what he's doing layful:
Let me put it another way. If I got four 12" Mono coils, and tested them on a 5c coin - three of the coils could detect the coin to 38cm, and one of the coils could detect it at 41cm.....which coil would you want?

Gold can easily be used in the sliding tube set-up, but the targets that get buried, if they are not gold means I can leave them there, and go back another day.

 

[reynard]

Hi nenard i like your idea of using coins. If you can get hold of pre 1945 coins they have a high silver content and would give a good comparison. I like the pipes into the side of a bank idea , at least you can take your targets with you. Also you are detecting over undisturbed ground, even if you don have the halo. Good luck .
Jim. erfect: :Y:

 

[Meerkat]

As I said, coins are a known and consistent target, so are better for comparative testing. Whereas with gold, a 1g nugget can be more detectable than a certain 6g piece. So if I do a test with a 6g prickly reefy bit, and get poor depth, someone will go out and test a 6g lumpy piece and get it heaps deeper and think, oh that Nenad doesn't know what he's doing layful:
Let me put it another way. If I got four 12" Mono coils, and tested them on a 5c coin - three of the coils could detect the coin to 38cm, and one of the coils could detect it at 41cm.....which coil would you want?

Gold can easily be used in the sliding tube set-up, but the targets that get buried, if they are not gold means I can leave them there, and go back another day.

I agree Nenad a consistent target such as the coin is best for comparative tests.

Also even for a larger target test then use several 50c coins attached together somehow on top of one another to produce extra thickness or side by side for a larger surface area?

 

[Goldtalk Leonora]

Cheers Deepseeker....I'm still not sure what he wants to actually achieve.

My experience with testbeds goes something like this........it is irrelevant what type of target you use. It doesn't matter if you bury them...run them down an inclined pipe or bury them into a bank of a creek. A testbed can only supply a constant target...and it really does not matter what that target is. All a testbed can provide is a place for someone to get some confidence that their machine is working...and a place where people like me can show the 'payoffs' or trade offs with using different detector settings. They do not (in my opinion) have any relevance to actually finding a native gold nugget in situ and I would never use them to compare coils etc. In fact it's easier to show how rubbish most detectors are at finding gold!! With the utmost respect to Nenad and others, I think that far too much importance is placed on testbeds and the real world practicality of detecting is often not included into the equation. What I mean by that is fairly simple....I can tell you the settings on any frontline detector that will give you maximum depth...no probs...but I can also tell you that you won't be able to use them/it....so whats the point! I'll duck for cover......

 

[dubbles]

Its always fun to see different tests with the gpx series,as you say there's a few variables to take into account,but still an interesting exercise.looking forward to your videos Nenad,every detectorist will have their own take on them!

 

[Moneybox]

Tests like this are always fun. We ran a competition here with I think about 16 targets, the locations clearly marked with paint, buried at various depths and spread far enough apart so throughout a big campsite so several could be detecting at the same time with their choice of machine or machines. Everybody, about 30 of us received a list of targets by type and number, they just had to place the target location in the checkbox. We were camped at the same site for a week so so everybody had plenty of time to test each location.

The results were clear, we have no idea what's down there regardless of your weapon of choice. We had nuggets ranging from 1g to 120g, the odd piece of steel including a can, lead bullets and a wheel weight, hot-rocks and I don't remember what else. Anyway only one person a newbie found the 120g nugget and correctly identified it.

No target was deeper than 250mm and several detectives picked a hot-rock as a nugget.

It's good if several people can be involved in the testing because we all identify sounds differently. Of course the target is only part of the puzzle. It's the mineral content of the ground and EMI that alter our results as much as the target its self.

 

[Tathradj]

When I do get out and about,
My first target, I peak the machine on it first then
dig it up.

If it is a small bullet or such, I know how my machine
is performing in that soil profile/coil combination.

if it is a piece of steel, I move onto the next until I find
some thing that is non ferous and small.

No good doing this over a screamer, Too much over load.

And that can change very quickly.

But as in burying a test target, When I do, I wet the soil a bit and pack it down hard.
It can be an indicator as to how your machine is performing and not
to mention quite a bit of fun as well.

Detecting is a fickle thing at that but oh so much fun. erfect: erfect:

 

[PhaseTech]

Nenad, if you need a field assistant, youve got my number

I already had you at the top of my list, judging by how enthusiastically you dug the holes when we did that little test patch at Jupiter Creek