Detector Depth Testing - Larger Gold

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.

Wouldn't using lead (sinkers etc) be better for targets? From my experience lead gives the most similar target sound to gold, whereas coins sound very different.

Can't wait to see them. :goldnugget: :goldpan:

#3 would be my choice Nenad.

I would also like to see symmetrical tests, both with same depths but with different soil types to see what differences they may create.

I agree option 3 would be my preferred choice and also I think lead is a better option as well. Not wanting to make it too hard for you Nenad but could you make lead copies of 50, 5 and 10 cent coins for this test that way we would be all familiar with the size and could easily replicate if we so desired. After that feel free to try to spend them down at your local. Look forward to seeing the result either way. Cheers mgh. :lol:

https://www.prospectingaustralia.com/forum/img/member-images/3960/1587177416_tube.jpg

Take a look at this setup. You can easily change your target or have several targets made up on the end of a piece of PVC.

https://www.prospectingaustralia.com/forum/viewtopic.php?pid=550385#p550385

Would the orientation of the coins over / under the coil make a difference... ie. flat or edge wise to the coil. And how would you control them? Round lead sinkers come to mind as a consistent size and weight.

This is a cool backyard setup.
https://youtu.be/vqK_z4pc7ts

I have a straight sided bank with a level top. I drill 1" holes 300mm in at different depths from the flat top , 50mm, 100mm , 150mm, 200mm; 3/4 " poly fits into the holes and I put my targets on the end of the poly; push it in ; then wave the detector over the top. Detecting in solid ground.

I really like Moneyboxes #6 post proposal.

I agree 5c & 50c are great targets.

Can I suggest a coke can crushed into a flat disc as the next one up as that is another one easily replicated & it will be a big step up in depth vs 50c - maybe double

Another reason I suggest the alu can is that I suspect it will go close to being the minimum size target that the detector can detect at its all up maximum depth ie I am not sure a saucepan would be detected much deeper than the alu can.

Alu can might not fit in the tube proposal though.

I can detect a can from 4ft away :awful:

I like the drill into the bank approach so the earth above is natural

I think two 1 oz nuggets , one porous and one solid , have them fixed to a polypipe and slid into drill holes

G'day

The problem with depth testing in the ground is similar to air air testing, there are of course other variables that come into play apart from the distance the object can be detected by the coil that will effect the outcome of the test, in the air test I only see this as a means to see that your detector and coil is operating as it should and nothing more, depth testing in the ground to be accurate has to emulate the conditions as close as you possibly can to a real life long buried targets, any disturbance of the soil makes the test inaccurate, any object that is not of the same form or of similar characteristics as far as density of the matter will also make the test inaccurate.

So in effect coins and similar objects are an easy target for most detectors as they have a flat wide surface area that is easy for the detector to see, few nuggets are like that and we all know when we do find a flat nugget they usually scream, rounded dense nuggets also give a good signal but odd shaped uneven surfaced nuggets can be very vague and in some cases are very iffy signals even when not buried very deep.

In effect the targets have to be pretty much as close as possible to natural nuggets, if actual gold nuggets cant be used then something as close to it as possible would give you the most accurate response, by memory I believe tungsten is the closest to gold in its density and in the absence of that then lead would be the next best thing as a test subject but of course the lead targets would have to be formed in a similar fashion to real gold nuggets.

In ground targets have to be placed in situ with minimal disturbance of the covering soil, and the reason for this is that undisturbed ground has layers of mineralisation long laid down over time, and there could be several layers I suspect, once these layers are broken the object buried becomes easier to hear, this is the reason that when we get an iffy response and we start to dig it the signal can develop from a maybe there is something there to a more positive yes I have a target there.

I think the best form of test is the drilling into the side of a bank where the above layers of soil remain undisturbed and also with using targets a close as possible to the gold ones that we are chasing, that would be as close to emulating real life conditions that we encounter in the field, apart from all this there are other factors such as soil moisture, soil temperature and also the halo effect that long buried targets can also display.

cheers

stayyerAU

Moneybox, yes that is what I'm referring to in my No. 3 method.

SteveG, lead is actually less conductive than gold, but this more comes into things when testing very small targets, as everyone knows the GPX's can struggle with very small lead, but gold of the same size is easily detected. Larger lead will be no problem for GPX's, so I think for comparative purposes it should be fine. My thinking with coins was more so that others are able to replicate the tests themselves, but if we go for spherical lead targets, I can put up the diameter and weight which should be quite consistent.

Ozzie, you are right, for consistency coins should be flat, so probably not suited to the sliding tube.

So what I'm thinking is maybe a combination of targets, with in-ground tests the obvious preference.

Test 1 - A sliding tube set-up, but use spherical lead targets to avoid any orientation issues.

Test 2 - 5c and 50c coins buried flat, at a fixed depth. Maybe even two of each, at slightly different depths.

I think a coke can is a good idea, but rather than squash it, might just cut off the bottom, so that it has a set diameter.

I'll have to think of a spot that is close enough to the car, away from traffic, and has pretty mineralised dirt.

Now the other tough one is settings! If you use the same settings with different coils, there are less variables, but it may not be a true representation of how each coil would be used. I see a lot of detector tests where the unit is chattering like crazy or picking up so much ground signal, that you'd never be able to run like that when actually detecting. So maybe I should keep things on the smooth side for each detector/coil combo and make sure it is not getting excessive ground signals. Then whatever the results are, you know you can probably push things and squeeze a little more out of it.

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:

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

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

Deepseeker said:

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:

Click to expand...

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.

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

I have a series of test targets i made from 50/50 lead/tin solder, each in a small plastic zip-lock bag with a strip of ribbon so they can be easily found & retrieved. (When buried vertically).
I prefer to use the horizontal hole in an embankment test as it offers the least ground disturbamce.

Hi Phasetech,

I have a lot of experience with testbeds.

What exactly is it you are wanting to achieve out of them? What is the point behind your videos?

cheers

Tony