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By Steve Herschbach
What we are discussing is usually called "Recovery Speed" by most manufacturers. From the White's XLT User Manual:
"Recovery Speed - Speeds target responses, so several targets that are close together can each respond.
When a metal is detected, it takes a fraction of a second for the detector to process the signal before it can respond to another metal target nearby. The time it takes to process the first metal target signal so that the second metal target signal can respond is called RECOVERY SPEED.
There are advantages and disadvantages to fast (high numbers) and slow (low numbers) RECOVERY SPEEDS. Faster RECOVERY SPEEDs work well in high trash areas. However, they will have some difficulties with very deep targets as well as double responses on shallow targets. Slower RECOVERY SPEEDs do not work very well in high trash areas. However, they will have better responses on very deep targets. Slower speeds also have more definitive discrimination sounds. A custom setting needs to be found that suits the preferences of the individual and the conditions in the area. As a general rule, the closer together the metal targets are in an area, the faster the recovery speed should be. The more spacing between targets, the slower the speed should be. Don't use the fast speed if you don't need to.
In very trashy areas it is recommended to switch to a loop smaller in size than the standard 9.5 inch black loop. Smaller loops offer better separation between targets. However, larger loops detect deeper and cover more area with each pass. RECOVERY SPEED combined with a smaller loop can be used to search severely trashy areas."
Just to confuse people White's decided to call it "Recovery Delay" on the V3i. A low recovery delay equates to a fast recovery speed.
From the White's V3i User Manual:
"Recovery Delay - 1 – 200 200 = slowest. Additional and separate (beyond filtration) selection for the signal response time. Short response time benefits performance in high trash by providing better target separation. A longer response time allows a larger window to detect deeper targets. Ideal Recovery Delay is dependent on Ground Filter selection, ground mineralization, trash density, and your average sweep speed (how quickly you move the search coil)."
It would seem detector manufacturers abhor standard terminology, even the same manufacturer! XP has decided to call Recovery Speed by an even newer term - Reactivity. From the Deus User Manual:
Regarding the VLF detectors.Can someone answer for me what constitutes a VLF with good discrimination?.I feel to discriminate that speed is a factor as well.Otherwise no matter how good,if a target is next to iron it will read off a good hit.
The Deus has fast reactivity,so is this now a good discriminator.Between ferrous and non ferrous?. How does this compare to say the Nokta Impact for speed discrimination.
Thanks in advance
While looking around on the Minelab site I came across this article by Bruce Candy. It will certainly be a re-read for some but for me it was a first.
There is much more than just Minelab in the article. It included ground balancing, discrimination, gold detectors, coin detectors and a host of other related issues with knowing some of the technology about target detecting.
It doesn't yet include ZED technology but does explain why it is so hard to have a gold detector that discriminates. (When you discriminate you lose targets!)
By Steve Herschbach
This is an informal survey, just out of curiosity. For those of you who have been out prospecting in the last year (back to Sept 2014) and actually have found gold nuggets, what detector or detectors did you find the gold with? The poll is not meant to prove anything. I am just wondering what detectors are most commonly in use now for finding gold nuggets by those who are actually finding the gold.
I am posting this on the most of the active US forums so please do not post your answer in more than one place. In a week I will compile all the answers from all the forums and post the results back to each one. Thanks in advance for you participation.
I own a number of units but so far in the last year my gold was found with the Minelab GPZ 7000, SDC 2300, and a few nuggets in trashy areas with the Makro Racer.
Thought I'd start a topic of a different nature.
What detector/s would you like to see reintroduced and why, and maybe a new feature or two if you dare.
The reason I'm starting this is because there's been some real fine units come and go over the years, and I think some are worthy of some new time in the limelight.
Why should it be reintroduced?
New features that would be nice:
Okay, this is really hard, but I'm going to limit it to 3:
Model: Sovereign GT
Why should it be reintroduced? Still one of the best discriminating beach/shallow wading machines ever made
New features that would be nice: A more compact control box that was at least weatherproof so i didn't have to chest mount the control box.
Model: Goldmaster 3
Why should it be reintroduced? Seems like the appreciation for the GM3 came after it was long gone.
New features that would be nice: Auto Tracking option like on the GMT, and would be awesome to add a lower frequency to make it a bit more versatile for relics, hotter soils etc. Sort of like a GMT/MXT hybrid but in the old style chest mountable control box.
Model: Diablo uMax
Why should it be reintroduced? So I could try one, and see what all the fuss is about :-) But seriously, a very lightweight "utility" gold machine should sell well, as long at it works.
New features that would be nice: A Disc mode with ground balance like the original lobo so you could use it for coins, jewellery and relics
By Steve Herschbach
This subject comes up so often it is time to get it into its own thread so I can just link to it in the future.
It is best to think of metal detectors made for prospecting as "nugget detectors" as that is the truth of the matter. Nuggets have some size to them.
Metal detectors are electromagnetic devices, and as such can detect items that are conductive and non-magnetic, like gold, or non-conductive but magnetic, like magnetite. Or both, like metallic iron.
When dealing with gold you are dealing only with conductivity. The more conductive the mass, the easier it is to detect. In general what this means is bigger is better. Any detector has a limit to how small an item it can detect.
Here is the kicker. Multiple undetectable targets do not add up to create a detectable target. I do not know how many times I've seen or been told of people throwing a vial of small gold on the ground and running a detector over it and declaring the detector will not find gold because it does not pick up the vial of gold. Or people thinking the detector has a problem.
Let us say that on a scale of 0 - 10 zero represents an undetectable piece of gold, and 10 one that really beeps. 0 + 0 + 0 + 0 + 0 still equals zero. So lots of tiny gold is just as undetectable as a single piece of tiny gold. You need a single conductive mass.
Fine gold usually has a coating, and putting a bunch of fine gold in a vial still results in little or no signal. If the gold is super clean and packed tightly you will get a weak signal. Melt it all together, and now it goes beep.
Another way to look at it is take some fine gold and pour it in a pile. Get a multimeter and test your little pile of gold for conductivity. It is hard to get much current if any through a loose pile of gold.
So bottom line is you might have 5 ounces of fine gold right under your feet, and you will walk right over it with your metal detector. Rich gold ore where the gold is finely dispersed in the rock will be hard to detect or undetectable. Wiry or spongy masses of gold are hard to detect.
Jewelry hunters run into this when trying to detect lost necklaces. A fine chain is very hard to detect as each link is undetectable and the connection between the links is poor enough the signals does not add up to much. Often all you can detect is the clasp. Rings even display this issue if the weld breaks. A complete ring really gives a great signal. Break the ring, it will be very hard to detect.
Now once an item is detectable, it does add up. 10 + 10 = 20 so two large nuggets in the same spot are easier to detect than each by itself. If each link in the gold chain can be detected, then it will add up into a more detectable target. A fun trick with target id detectors is to tape 5 nickels together and run them under the coil. They will read as 25 cents!