Why My PI works great for gold.

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04-18-2016, 02:30 PM
Post: #1
Why My PI works great for gold.
(This post was last modified: 04-18-2016 02:33 PM by Sven TreasureLinx.)
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The Mirage PI that I build, now and then I get a question why its so good finding gold and not silver. Why is it not deeper than general purpose PI's finding silver vs. gold?
Sometimes its tough explaining it in simple terms when asking what kind of PI should I buy. I found a report by White's, copied and pasted here the main reason


The pulse repetition rate (transmit frequency) of a typical PI is about 100 pulses per second. Models have been produced from a low of 22 pulses per second to a high of several thousand pulses per second. Lower frequencies usually mean greater transmit power. The transmit current flows for a much long time per pulse, however, there are fewer pulses per second. Higher frequencies usually mean a shorter transmit pulse and less power however, there are more transmit pulses per second.
Lower frequencies tend to achieve greater depth and greater sensitivity to items made from silver however, less sensitive to nickel, and gold alloys. They typically have a very slow target response, which requires a very slow coil sweep speed.


The Mirage PI is a high frequency detector-
Higher frequencies are more sensitive to nickel and gold alloys however, less sensitive to silver. They may not penetrate quite as deep as the lower frequency models regarding silver however, can be used with a faster coil sweep speed. Higher frequency models are generally more productive for treasure hunting because the faster sweep speed allows more area to be searched in a given time, and they are more sensitive to the ultimate beach find, gold jewelry.

There are several more calibration settings that also make it more sensitive to very small gold nuggets and jewelry that's Pulse Delay and Pulse Width.
Sweep speed of the Mirage can be a small snail crawl or faster VLF pace. With the SAT control can be used as a motion recovery control. Set at 75%, you can swing like a normal VLF machine.

Have to get out and use it more, tired of digging the tiny foil bits with the VLF. I can more or less tune the foil out and still find the small gold.

Nokta Impact, Deteknix Quest Pro,Teknetics Mark 1
Self built Mirage PI's --- they work great!!
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04-18-2016, 10:00 PM
Post: #2
RE: Why My PI works great for gold.
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That, Sven, is some really good info. I have buckets full of foil and pulltabs.

Ed/ODF

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04-18-2016, 11:05 PM
Post: #3
RE: Why My PI works great for gold.
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Thanks for the lesson on PI detectors. Makes sense. Sometimes you have to give up one thing to get another thing--kind of like more disc, less sensitivity I guess. Since components are so little and light now with integrated circuits, small boards etc. couldn't you get both high and low frequency rates for the pulses in one machine, maybe with a switch to go from one to another? Or would that mean two of everything including coils etc to complicate things? Would be a killer if it would work.

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04-18-2016, 11:40 PM
Post: #4
RE: Why My PI works great for gold.
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Circuits are completely different as are the search coils.
But don't let the loss of depth on silver fool. With my 7" coil, it will get the depth
of an 8-10" coil on a VLF machine. So not too shabby.

Nokta Impact, Deteknix Quest Pro,Teknetics Mark 1
Self built Mirage PI's --- they work great!!
Free Vintage Metal Detector Catalog Downloads, Tips, Mods
http://www.treasurelinx.com/home1.html
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04-19-2016, 08:07 AM
Post: #5
RE: Why My PI works great for gold.
(This post was last modified: 04-19-2016 08:10 AM by updownup.)
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Sounds like a awesome machine and I have seen some of your postings of the gold found with Mirage. As all your work, the machine looks professionally built. Think this machine would be bonus for anyone's arsenal. Good job Sven, thanks for information.

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04-19-2016, 06:38 PM
Post: #6
RE: Why My PI works great for gold.
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I don't think many hunt the beaches to find silver anyways, it's the yellow they want. So, not being able to hit as well on silver wouldn't faze me, but...

Don't think I'd be able to enjoy a VERY slow swing speed. The beaches around here are super competitive, and one must try to cover as much ground as possible, before the competition muscles in during peak times, which makes maximum coverage important.

Where I think your unit would excel, is in the micro jewelry hunting niche, Sven. Would you agree with that?

Joe

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04-19-2016, 08:36 PM
Post: #7
RE: Why My PI works great for gold.
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(04-19-2016 06:38 PM)NjNyDigger Wrote:  I don't think many hunt the beaches to find silver anyways, it's the yellow they want. So, not being able to hit as well on silver wouldn't faze me, but...

Don't think I'd be able to enjoy a VERY slow swing speed. The beaches around here are super competitive, and one must try to cover as much ground as possible, before the competition muscles in during peak times, which makes maximum coverage important.

Where I think your unit would excel, is in the micro jewelry hunting niche, Sven. Would you agree with that?

Joe

Slow swing? You can swing it faster than you think, about a foot a second, go slower for deeper items - It will give the PI longer to sample the target.
Micro jewelry yes but, like any other PI or VLF, small thin chains not good. But, it will find 3.2 grain gold nuggets. It will find the small charms, earrings VLF machines ID into the iron range most will not dig.

Nokta Impact, Deteknix Quest Pro,Teknetics Mark 1
Self built Mirage PI's --- they work great!!
Free Vintage Metal Detector Catalog Downloads, Tips, Mods
http://www.treasurelinx.com/home1.html
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04-19-2016, 08:45 PM
Post: #8
RE: Why My PI works great for gold.
(This post was last modified: 04-19-2016 08:48 PM by updownup.)
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From my experience, I agree covering as much ground as possible on wet and dry sand. But in the water you will have a slow sweep regardless. Sometimes, I have too stop hunting in the water because (Feels slow) and I want to cover more wet sand, easier recovery and more targets. However, we all know less trash and possibly more quality finds in water.

It's funny, if I did not find something real nice at the end of the hunt. I say to myself I should have stuck with the other type of hunting. (Water or Land) Guess because it could have been better. lol.

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04-19-2016, 09:16 PM
Post: #9
RE: Why My PI works great for gold.
(This post was last modified: 04-19-2016 09:17 PM by NjNyDigger.)
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(04-19-2016 08:36 PM)Sven TreasureLinx Wrote:  
(04-19-2016 06:38 PM)NjNyDigger Wrote:  I don't think many hunt the beaches to find silver anyways, it's the yellow they want. So, not being able to hit as well on silver wouldn't faze me, but...

Don't think I'd be able to enjoy a VERY slow swing speed. The beaches around here are super competitive, and one must try to cover as much ground as possible, before the competition muscles in during peak times, which makes maximum coverage important.

Where I think your unit would excel, is in the micro jewelry hunting niche, Sven. Would you agree with that?

Joe

Slow swing? You can swing it faster than you think, about a foot a second, go slower for deeper items - It will give the PI longer to sample the target.
Micro jewelry yes but, like any other PI or VLF, small thin chains not good. But, it will find 3.2 grain gold nuggets. It will find the small charms, earrings VLF machines ID into the iron range most will not dig.

Ok, I misread that. Fast swing speed, check. Hits smaller gold well, check. Inexpensive compared to Excals/Sovs/CZ's, check. I'd surely give one a shot. But on a cleaner beach only, as I really don't want to be digging down 2 feet for bobby pins & fishing sinkers, lol.

(04-19-2016 08:45 PM)updownup Wrote:  From my experience, I agree covering as much ground as possible on wet and dry sand. But in the water you will have a slow sweep regardless. Sometimes, I have too stop hunting in the water because (Feels slow) and I want to cover more wet sand, easier recovery and more targets. However, we all know less trash and possibly more quality finds in water.

It's funny, if I did not find something real nice at the end of the hunt. I say to myself I should have stuck with the other type of hunting. (Water or Land) Guess because it could have been better. lol.

You're right, much slower in the water, due to the resistance when swinging the coil, but, much better, too, as there's less junk to contend with, and less competition as well, since most hunters only work to the wet water line. This is the reason guys that scuba can go out and sometimes find 5, 6, or 7 gold rings in a hunt. They're literally able to go where no man has gone before, unless there are other divers in the area.

For some reason, maybe it was my mindset, I never did well in the dry sand. However, if one thinks logically, there's probably just as much treasure there, as there is in the wet and the water. Unfortunately, there's also a LOT more trash to sift through, also.

Beach hunting is a world unto its own. There are guys who can tell if a hunt is going to be productive based on which direction the wind is blowing, or how rough the surf is, and a million other things, which only comes after many years of experience. Me? I checked the low times and just went! Chuckle

Joe

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