Frequency on gold

[jangles]

I'm confused and maybe some experts can set me straight. I see gold detectors with freqs like 71 khz and some "gold detectors" with freqs like 18khz I understand the lower the freq the deeper it will find a target (if it's large enough) however the higher the freq the better on small gold but not as deep, so how come the sovereign gt with up to 1.5-25khz is getting a bad rap as a gold hunter when units like the fisher gold bug pro run 18khz? Mind you I don't plan on gold hunting I'm just trying to understand the freq on gold as the freaks are all over the place...what gives?
Thanks

 

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[Steve Herschbach]

I would hang onto that Compadre. It easily outperforms my $5795 Minelab GPX 5000 by a huge margin, like several times the depth I might get under optimum conditions on a similar size target.

 

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[ToddB64]

"Frequency on gold" thread by jangles

Thank you to all, always learning.

ToddB64 it's a good thing you did, getting permission to reprint this information. A very good explanation.

Terry, thanks for the videos, it's always nice to see an explanation as well as hear it.

Steve, you really do explain things well. With you and Nuggetshooter323's input on smaller coils I think I'll get the 6.5" for my GB2. I have a good range of hearing, is there a particular set of headphones you recommend for the GB2?

Mike

Thanks Mike ! ...........Todd

 

[ToddB64]

THE PROPERTIES OF GOLD AND HOW GOLD DETECTORS WORK

Hi !

I've been doing a little research on the properties of Gold. I always thought Gold was non-magnetic (Not attracted by a magnetic field.), but didn't know why. I discovered it's because gold and a few other materials are diamagnetic, meaning they are repelled by positive, or negative, magnetic fields. This is explained in Lenz's law, but I'll paraphrase here and say that all materials are diamagnetic and this property always makes a contribution to a greater or lesser degree insofar as a material's response to magnetic fields.

When materials have a different form of magnetism, such as ferromagnetism, the diamagnetic property exhibits little force. A few examples of metals that display stronger diamagnetic force are gold of course, copper, bismuth and mercury.

Somehow manufacturers design their detector circuits to report signals from metals that have a stronger diamagnetic force, gold being a good example here. Could someone offer an explanation of how this is done, in laymen's terms so the majority of us can understand, without revealing company secrets perse ? To make it easier, let's just focus on VLF Gold detectors....OK ?

Thanks to all who reply on this ! I hope Dave J. and Monte V.B. will give it a try !

ToddB64

 

[Terry Soloman]

Hi !

I've been doing a little research on the properties of Gold. I always thought Gold was non-magnetic (Not attracted by a magnetic field.), but didn't know why. I discovered it's because gold and a few other materials are diamagnetic, meaning they are repelled by positive, or negative, magnetic fields. This is explained in Lenz's law, but I'll paraphrase here and say that all materials are diamagnetic and this property always makes a contribution to a greater or lesser degree insofar as a material's response to magnetic fields.

When materials have a different form of magnetism, such as ferromagnetism, the diamagnetic property exhibits little force. A few examples of metals that display stronger diamagnetic force are gold of course, copper, bismuth and mercury.

Somehow manufacturers design their detector circuits to report signals from diamagnetic metals, gold being a good example here. Could someone offer an explanation of how this is done, in laymen's terms so the majority of us can understand, without revealing company secrets perse ? To make it easier, let's just focus on VLF Gold detectors....OK ?

Thanks to all who reply on this ! I hope Dave J. and Monte V.B. will give it a try !

ToddB64

Whether paramagnetic or ferromagnetic, all metals conduct electricity and create electromagnetic fields. Low frequencies have better sensitivity to copper and silver, while higher frequency detectors are more sensitive to natural gold.

 

[nuggetshooter323]

I remember Jerry Gould, inventor of the Bazooka Gold Dredge, wrote an article where he was talking about magnetic properties of gold under the right conditions. If you put electromagnets on the bottom of a sluice, without the electricity, the magnets will of course hold black sand. But with a current to the magnets, gold sticks to the black sand that is sticking to the magnets. I always thought that was kind of intresting.

 

[ToddB64]

"Frequency on gold" by Mike > Steve Herschbach's Post #3

I would hang onto that Compadre. It easily outperforms my $5795 Minelab GPX 5000 by a huge margin, like several times the depth I might get under optimum conditions on a similar size target.

Steve......Are you being serious, or pokin fun at me ?

I'm sorry, but it was an air test and those were the "coil-height-above-target" measurements I got, as my wife can attest. I couldn't believe it at the time and even looked under the plastic bench to see if there was a hunk of metal laying on the outdoor concrete patio slab under there; I also felt around under the bench seat to make sure there wasn't a metal frame or suport bar.....I found nada !

In addition, I had to go faster with the coil swing as the coil height above the target increased, in order to maintain a signal and that signal only happened as the coil passed over the tiny ball-bearing, so it couldn't have been rebar in the concrete (16 + inches below the bench seat) being perfectly aligned with the ball....that would be a stretch-of-the-imagination I think !

Guess my Compadre is just a good one ! I don't know what else to say , except I will hang onto it.

ToddB64

 

[Steve Herschbach]

Hi Todd,

Well, I guess I was messing with you a bit. I will come right out and say it. It is impossible that your Compadre was detecting a 1/32" (.0312") ball bearing at 19". I am not saying your detector did not signal on something. The key if you want to go along with me on this is that the detector cannot have been picking up that target at that distance, even in an air test. That being the case you can try and figure out why it was doing what it did and what it was picking up. Or just accept that the test was flawed and move on.

First thing to do is reverse your test. Place the detector on a table with the coil hanging about a foot off the edge and stationary away from any metal. Put the bearing on the end of a wood stick or plastic rod. Wave that under the coil and note the response. Be sure you do not wear a watch or ring etc. on your hands near the coil when doing this.

 

[ToddB64]

Steve,

Actually, I'm glad you challenged my original test results. I should have recognized those results were bogus in the first place, instead of making a dxxx fool of myself !

So I'll re-do the test as originally performed just to see if my memory was playing tricks on me, as I didn't write down any results the first time , then I'll repeat the test with the setup you suggested, except I'll be using a test frame I made pictured below......it's all wood, plastic and rubber (no metal.).

I'll report the new test results asap.

ToddB64

 

[Steve Herschbach]

Honestly your test results are not near as important as your enthusiasm and gusto for setting up test scenarios. I'm impressed with your test bench. Only issue to look out for is Electromagnetic Interference (EMI). Tip of the hat you you!

 

[jmoller99]

I have a Compadre. Its actually quite good for small gold (like necklaces). It runs at 12Khz, which is partly why. However, it has no ability to deal with ground balance issues (or adjustable in much of any way). There are mods you can make to deal with some adjustabilty, but I'm happy with it as it is. I don't use it for prospecting, because I have other detectors that are better at finding gold.

 

[Jim Hemmingway]

Honestly your test results are not near as important as your enthusiasm and gusto for setting up test scenarios. I'm impressed with your test bench. Only issue to look out for is Electromagnetic Interference (EMI). Tip of the hat you you!

ToddB64... I'm with Steve's remarks above. I find your meticulous approach refreshing. We've all overlooked things or made outright blunders when posting to the forum. Please don't be concerned and do continue with your contributions here. All the very best.

Jim.

 

[Lanny in AB]

ToddB64... I'm with Steve's remarks above. I find your meticulous approach refreshing. We've all overlooked things or made outright blunders when posting to the forum. Please don't be concerned and do continue with your contributions here. All the very best.

Jim.

Wow--now you've got another expert weighing in--lucky for that--Jim really knows his stuff!

All the best,

Lanny

 

[ToddB64]

2nd Test Results With 12kHz Compadre and Bic Ball Tip.


Post #29 by Steve Herschbach:Honestly your test results are not near as important as your enthusiasm and gusto for setting up test scenarios. I'm impressed with your test bench. Only issue to look out for is Electromagnetic Interference (EMI). Tip of the hat you you!

Post #31 by Jim Hemingway:ToddB64... I'm with Steve's remarks above. I find your meticulous approach refreshing. We've all overlooked things or made outright blunders when posting to the forum. Please don't be concerned and do continue with your contributions here.
All the very best.
Jim

___________________________________________________________________________________________

Thanks Steve H., jmoller99, Jim H and Lanny for your comments !

You know, as I sat down at my computer to post these results of my second test with the Compadre and Bic ball tip, I was feeling a bit embarrassed and not very enthusiastic about "eating crow". Yes, my new test results were drastically different ! But when I read the above comments by Steve and Jim, it warmed my heart and swept away all those negative feelings....your encouragements were powerful medicine !

Now, when I did the first test with the Bic ball tip, I didn't think the Compadre could signal the steel reinforcement mesh in the concrete patio were I had my setup, since the patio surface was 16 inches below the plastic bench seat I was using as a test table and the reinforcement mesh was down in the concrete at least another 2 inches. However, upon further investigation, that was a wrong assumption on my part !

So I didn't use the test rig pictured in my post #28 for the second test. I decided to go out into the yard and put the ball tip in a 4" x 4" x 1/2" deep cardboard lid from a jewelry box and set the lid on the grass. Then I scanned the ball and the distance where I could still get a signal was an estimated 2 inches max. for this air test and would be less in the ground depending on the amount of mineralization. However, these test results were close enough for me to see if the 12kHz Compadre could signal on a 1/32" dia. steel ball at all and that gives me some idea of the depth range I might expect on a piece of gold of the same approximate size in a matrix of sand, soil and gravel in the Creeks.....in other words about one inch ! Of course, the depth range will increase as the size of the gold increases and more eddy-currents are generated.

I bought .5g of #6 mesh gold (20-22 Karate, 83-93% pure) to practice on with my Compadre. I received (5) pieces of gold, each weighing .1g , as weighed on my electronic pocket scale after calibrating. I will be doing some air tests and "in-ground" tests with one or more pieces of this gold inside water-tight plastic pill bottles and will report the results in the near future.

Happy Hunting My Friends !

ToddB64

 

[GarretDiggingAz]

Todd,

Thanks for your enthusiasm. I still have yet to do these tests for my ATG. I'll eat crow. They say you should do these tests so you have a general idea on what to expect. I keep saying ill do this and haven't of course. I'm sure I'm not alone in this. So the crow feast begins. Lol.
I'd hate to think that I'm waiting to hear a crisp tone for gold and discover after doing an air test and garden test, that I should've been listening for a whisper or zip and don't have an ID# on display. I've heard this happen. So kudos to you. You've lite a fire under me to do my homework to see what I should expect and not to expect something that may not be the case when it comes to small gold.
I've seen my detector go over gold (not my personal one) and it detected it with a solid tone and read 43 if I remember correctly. So that's what I've come to expect. I've picked up small lead pieces about the size of half a pinky nail. Had a tone and an ID in the 40s. Never thinking it could react differently on the smaller stuff.
So thanks again for letting me know I'm not doing it correctly. So this week hopefully I'll find a decent enough piece of gold to test with (panning). If nothing else I'll try the ballpoint pen test.

 

[Rawhide]

All Im going to say is Zippers have made me look silly more than once. But you got me going to do a air test with the small coil now. Been trying to find a nugget for two years. If .22 call shell casings were nickels, I would be able to retire. Great post.

 

[63bkpkr]

This is truly a great thread so I hope I do not muddy it up. Depth of detection in air is an interesting heads up on a comparison method with any detector/coil combination and what that combination is capable of but we do not use the detectors this way in the field. In the field the conditions are variable from foot to foot of mineralized section of ground and if we are lucky we do not have a heavy iron composition that will totally distort/destroy a VLF machines signal.

My GMT setup includes these three coils and I commonly use the 4 x 6 DD shooter coil. While detecting "solid bedrock" {see Bedrock 101 by Lanny} with the GMT/4 x 6 setup I would obtain signals through 6"-8" of rock
and after panning the deposit that had accumulated between cap rock and bedrock I would steadily locate finds like this. I'm wondering if the composition of the host rock somehow aided the signal from the coil to sniff out these flakes, the machine is just this good, there is actually rebar in the bedrock or just why the signal went so deep. Of course this is just one of the infinite situations all of us face when we are "out there" looking for the yellow metal and at times there seems to be no clear, non changing method that we can steadily depend on to work time after time, seems we always have to tweak the system to get it to function..............63bkpkr

 

[NJnuggetpirate]

This following is in reference to VLF (induction balance) detectors. PI (pulse induction) is a different thing entirely where frequency is rarely discussed except as relates to electrical interference.

Frequency does two things. First, the target itself. Higher frequencies hit harder on small targets. Not gold per se, small targets. Take a common BIC type ball point pen, the type where the entire pen is plastic except for that little ball in the point. No other metal. A good gold detector will pick that ball up. A coin detector, you can write your name on the bottom of the coil and get no signal.

Low frequencies do not detect deeper. That is a broad statement with no meaning. In air tests high frequencies will detect farther, and on small targets a low frequency detector will miss it is obvious the higher frequency detector goes deeper.

The second thing frequency does is change ground response. Low frequencies do not react to ground and hot rocks as much as high frequencies. So that hot Gold Bug 2 also picks up ground and hot rocks better, and this means it gets very poor depth on larger targets in highly mineralized ground. It gets great depth on large targets in the air or in no mineral ground, but add mineral and the depth drops rapidly.

Detectors that work under 10 kHz hit very well on coin size targets and have a low ground response, making them great coin machines, but they have poor small item sensitivity. Detectors over 20 kHz are hot on tiny targets but have more issues with ground and hot rocks. Detectors in the teens are chosen as a best all around solution for do it all detectors. People used to coin detectors find them "noisy" as they tend to chatter on small targets and ground that a coin detector, designed for smoother operation and depth on coin size targets, will ignore.

People always ignore one thing when they go on about the Minelab multi-frequency detectors. They focus on the so-called high frequencies employed. It does not matter. What does matter is those detectors are designed to find silver coins and are tuned and act like lower frequency detectors. Do not let specs blind you to reality. If multi-frequency were good for nugget hunting Minelab would make multi-frequency nugget detectors. They do not, nor does anyone else. The nugget machines run at one frequency to put all the power into one frequency instead of sharing it among multiple frequencies. I am not saying the Minelab units will not find gold - my CTX 3030 is a jewelry killer. But it is not a hot nugget machine.

There is another thing frequency does, and that is deal with electromagnetic interference (EMI). Some frequencies like the 30 and 40 kHz range get avoided due to interference issues.

Finally, the nugget market is saturated and most serious, that is to say "been at it awhile", nugget hunters already have their detectors. The AT Gold does just fine compared to other mid-frequency detectors. The thing is it also does no better than anything else out there for years. So nobody is rushing to replace the detector they have with the AT unless they need a waterproof nugget detector, a rare requirement indeed. Most guys hunt in deserts. People mention what they have and what has been around for years and the AT is a new kid on the block. Bottom line is as a nugget hunter, take away the waterproof, and it is just another good detector along with a half dozen others.

To sum up, the higher the frequency, the better the response on small targets, and the better the air test. But the higher the frequency, the more response to ground and hot rocks. The two work against each other, and a detector has to balance the two parts of the equation. Mid frequencies are basically just the best compromise. Multi-frequency units just think of as lower frequency units and you will be fine.

Steve Herschbach
DetectorProspector.com

Steve I'm curious are you a expert on metal detectors

 

[Steve Herschbach]

Steve I'm curious are you a expert on metal detectors

I consider myself a student of the subject.

 

[NJnuggetpirate]

I consider myself a student of the subject.

With all serious you are more to a teacher standard my friend

 

[Jim Hemmingway]

NJnuggetpirate... I would venture say that Steve Herschbach is the most highly regarded and respected individual in the metal detecting / prospecting community in modern times. He possesses a very well documented history of unparalleled successes in the gold prospecting field over several decades... in Alaska, Australia, and gold areas of the West.

Steve willingly shares his expertise and has helped me and countless others over many long years... a completely unselfish individual... whose remarks / advice are unequivocal and unbiased with regard to brands.

I've known Steve for a lot of years now... and I hope this doesn't embarrass him too much... but heck... he has earned and deserves this acknowledgement for his many longterm contributions within this community.

Jim.