Jan 07, 2013, 12:54 AM
Frequency on gold
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?
Jan 07, 2013, 03:27 AM
Great post. I got my detector which has 18 kHz. I've been told by others in mining supply stores that I've got a good detector. ATG.
Yet I never see it suggested as a gold hunter. Mostly I see the PI's like the minelab. Then also the Gold Bug 2. Or the tesoros.
I was researching my detectors based on frequency as well. Thinking the lower the better. For depth that is. Then as you stated there is, higher freqs finds smaller gold.
You can drive yourself crazy trying to decide on this. Reality is. All detectors find gold. You've got to be swinging over it to detect it. Depends on size and depth.
I figured that I'd get a detector that can find pickers at 6-8" then from there I'd dig and pan some samples of area.
Hope that helps some.
If you're looking for a detector for gold and want to spend the money on it. Then I'd check out some prospecting clubs in areas that you'd like to hunt. See if you could try or even borrow/rent one of the detectors they are using. To see if you like it. Them go from there.
Jan 07, 2013, 09:24 AM
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.
Last edited by Steve Herschbach; Jan 09, 2013 at 07:58 AM.
Find me at DetectorProspector.com
Jan 07, 2013, 05:56 PM
Thanks for all's help, I guess those GPX's are P.I. units!
Jan 08, 2013, 01:12 PM
Peace Through Superior Firepower
In minerlized ground with a VLF, it's going to be seldom if ever that your going to detect a picker at 6-8". Reality is more like half that or less, but instead of having an expectation of depth, have none. Just channel all your attention through your detector, your technique, and the terrain. You should be concentrating hard enough to actually fatigue yourself just in it of itself. I have to rest every 1 1/2 hours just from keeping my concentration so high. One of the best books I ever read on the correct technique was "Zip, Zip", by Larry Sallee. For GMT and Goldmaster user's it's required reading, but any nugget hunter can benefit from it.
Originally Posted by GarretDiggingAz
Last edited by nuggetshooter323; Jan 08, 2013 at 01:30 PM.
Jan 08, 2013, 09:20 PM
Yeah sorry about saying picker. Not familiar on sizes to terms. Picker for me is like a half size for fingernail. Lol.
I've got more reading to do. Just when you think you've read enough. Read some more.
I find when I'm swinging I'm trying to pick out which of the multiple tones is the target I want. Does get tiring.
My boy covered a 20'x30' area compared to my 10' straight run. After digging up trash (iron mostly) and tabs I had to call it quits for the day. I try to tell him slow and low. Treat it like painting a wall. Have some overlap. He swings and steps. Ughhhhh. Oh well. Practice makes perfect.
Mar 15, 2013, 01:19 AM
X's 2 on "Zip Zip" 272 pages of detector/ and operator know how. I'm on my third time reading it
Originally Posted by nuggetshooter323
Mar 15, 2013, 11:50 AM
Make America Great Again!
I just wanted to bump this post again because it is so darn good!
Originally Posted by Steve Herschbach
Mar 15, 2013, 01:11 PM
frequency on gold
Thanks for all the good info. Steve you said among other things in your post:
"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."
Does this mean the mineralized ground is deflecting the signal before it gets to the desired target or just masking the target signal by overwhelming it with the mineralized / hot rock signal. Make sense?
Last edited by delnorter; Mar 16, 2013 at 12:25 AM.
Mar 15, 2013, 11:09 PM
And threads like this are why i love this forum!
Mar 16, 2013, 12:55 AM
Married,3 Sons,5 Grandkids,Night College,Home Study, 25 yrs. Gear Industry,Co-Owner Drapery Business
Originally Posted by delnorter
I've got your answer ! It appears in one of Clive James Clynick's books, titled "Site Reading" for Gold and Silver, beginning at the bottom of page 20 and completing at the top of page 21.
Due to Copyright laws, I must receive permission from Clive before posting the paragraphs here and I'm sending him an Email today.
Anyone owning a copy of this book can re-read the answer at their convenience if desired and perhaps these folks might recall the explanation Clive got from "B.B. Sailor".
I'll be back to report asap.
Last edited by ToddB64; Mar 16, 2013 at 01:09 AM.
Reason: Shifting text and underlining book title.
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Mar 16, 2013, 09:27 AM
Peace Through Superior Firepower
I'll tell you how I understand it, and Steve can correct me if I'm wrong. The harder the ground rejection circuit has to work, the less depth you get. That's why a lot of nugget hunters using a VLF, use a smaller coil in highly minerlized soil. It "see's" less minerlization at one time, so the ground rejection doesn't have to work as hard.
Originally Posted by delnorter
Mar 16, 2013, 11:02 AM
"or just masking the target signal by overwhelming it with the mineralized / hot rock signal."
It is actually simple. Ground balancing is just another discrimination circuit at work. It is also referred to as ground rejection. The detector discriminates out the ground reading. Targets that read the same as the ground are also eliminated. Targets are masked by the ground. The more ground you must discriminate out the more target masking occurs.
Low frequency detectors react less to the ground so there is less need to discriminate out the ground. But they miss tiny gold. So crank up the frequency, now you hit the tiny gold, but the ground gets more reactive. You apply more ground rejection to eliminate the ground signals, but now deeper targets are getting tuned out. Two opposing effects at work.
Salt can be a ground signal on alkali flats or salt water beaches. Tiny gold items read like salt water. You can use low frequency or PI detectors that do not pick up salt water but they miss the tiny gold chains and earrings. You can try an MXT to hit the items, but now you pick up the salt. You can flip on the Salt switch on the MXT to eliminate the salt reading, and now you lose the gold! Two opposing effects at work.
There are many items in the ground that you want to dig that generate a signal that is the same as the ground reading and so are missed by tuning out that ground signal. What makes a Minelab GPX 5000 special are the timings, which are nothing more than a set of ground elimination settings designed to reveal as many targets as possible. Each timing rejects a certain type of ground and also rejects a certain number of good targets. Changing timings will reveal targets that another timing was eliminating.
Detectors work perfectly in the air. They do actually detect the ground. Prior to ground balancing circuits being developed you just lived with no depth due to the ground hiding everything. Ground balance was a game changer, but people would be amazed at what still remains in the ground due to ground balance systems themselves eliminating targets. Add the use and limitations of regular discrimination circuits and the sky is the limit for guys like me. There is no lack of good detecting left to be had out there.
And yes, small coils help eliminate all types of target masking, including ground effects. Putting a large coil on a VLF often results in less effective depth, not more. Counter-intuitive but true. Especially with high frequency units.
Last edited by Steve Herschbach; Mar 16, 2013 at 11:45 AM.
Find me at DetectorProspector.com
Mar 16, 2013, 11:32 AM
Make America Great Again!
Here is part of a lecture on Discrimination and Ground balancing, and PI vs VLF detectors given by Steve Gholson, at the Minelab Technology Training Center in Arizona. Not all of it applies, but some does. I hope you find it helpful:
Mar 16, 2013, 03:52 PM
You really are the master at explaining things so that they finally make sense! Both of your posts on here should be required reading for anyone that wants to understand frequency, the effects of ground, coil size, effects of salt, target size, depth capability, etc., etc.
Fantastic job Sir.
All the best,
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