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Mike Hillis

My Requirements For A Micro / Tiny / Small Jewelry Detector

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Hunting tiny gold jewelry in inland sites is just so different from mainstream detecting methods that unless you do it you don't understand the requirements.    

#1.   EMI stability.   Your detector has to be stone cold stable.  No spurious noise.  None.  The signals you are after are small tight signals and you can’t hear them if your detector is making spurious noises.

#2.   The detector needs to be able to keep its HOTs at low gain/sensitivity settings because:

a... You need to be able to focus on the right depth of signals and those tiny signals are not deep.  Most of the time they are just down in the grass roots.   You want to focus only on the top three to four inches of depth.   If you have to run your sensitivity at or near max all you are doing is masking the desired signal response with reports from all the other signals surrounding it and below it.  And in cases where the ground minerals are high, the ground itself will mask the response.  

b... You need to control the coil foot print.  In this type of hunting you don’t want coil edge surface responses.  You only want to hear what is directly under your coil.   Concentric coils work better at this than DD coils.  DD coils are ok but you get better footprints with concentric and tighter readings on your meter.

#3.  The higher the operating frequency, the more important the above become.  As the operating frequency goes up, the level of discrimination goes down because the trash targets hit harder and sound better.   In other words, the higher the operating frequency the better the trash sounds and responds.

#4.  Notch discrimination or some other form of discrimination that will allow you to focus just on the signal range you are hunting.   The only range of signals you are interested in are in the ferrous/non-ferrous boundary range and the foil range up to maybe the nickel reading.   All other signals are distractions.

I'm editing to add a number #5.   Tiny signal audio boost is a big plus if it can be deployed while keeping original signal response integrity.  

I'll close with this.....You can take a gold prospecting unit onto a woodchip playground or a sand pit and as long as it can handle the EMI you can hunt with it on normal settings.  But if you are targeting sites  where good quality, tiny jewelry is most likely to be present, you will be working a lot of turf sites where a prospecting detector's normal feature set isn't going to be very helpful. 

HH

Mike

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Great concrete advice - based on experience.  I know you aren’t into PI’s, but consider this.

The Manta PI, which is now in the process of final development by Fisher might make an interesting tiny gold finder.

It has a very short minimum pulse delay - 8μ seconds or so.  that should make it able to detect all but the tiniest gold, especially at the shallow depths you are talking about.  The sensitivity is variable and it ID’s or excludes all but huge ferrous as well as high conductors. the set point for that control is variable. 

The testing up to now of this device has been pretty  Much at the beach because it is designed to be a killer on gold in salt water.  It hasn’t - as far as I know - been tested in the environemnts you are talking about.  I suspect with the correct adjustment of controls it might prove a killer in the grass and in tot lots.

Maybe Fisher should let you test it for that.

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Hi Rick,

Anything can hunt a tot lot,   If you want to hunt tiny targets in a tot lot, just get a normal high frequency gold prospecting unit and have at it.  Totlots and sand lots you dig everything just because you can, its easy to dig everything.

Turf is where the restriction is at.   You can't dig everything in turf and you don't want to dig everything in turf.   It will look like the top of Hacksaw Ridge in a very short period of time if you try to dig everything in these turf spots.  

I had a Whites TDI for a season.  The two biggest drawbacks I had with the TDI was 1)  it lumped small non-ferrous and small ferrous targets together.   I couldn't tell a paper staple from an earring.   and 2) the ridiculous coil control it required to keep the ground from responding.   As long as the ground was flat and I kept the coil 3 inches or higher off the ground I had a silent detector but in uneven ground every irregularity made it report, which resulted in having to keep the coil even higher off the ground and, if I didn't keep my mind in the game, staying on top of identifying what was sounding off, the ground or a target,  I could end up chasing a ground surface irregularity like it was a target.   It did work well for high conductors, however.

So....the Manta PI would need to have small ferrous rejection, (no staple responses) with some form of ground balance to kill the surface irregularity responses, and some form of discrimination to limit what reports.    8 ns is extremely low and will be somewhat like hunting with a high frequency VLF.   Everything is going to report.   There will need to be some low conductive non-ferrous discrimination.   The only way you can do non-ferrous discrimination like this with a PI is by measuring multiple PI pulse delays:   Hits at 8 ns, still hitting at 11 ns, don't give an audio response.  Hits at 8 ns, decay is complete by 11 ns, give an audio response or a meter reading or whatever.   Last I checked they haven't started making these yet where you can dial in a bottom and a top pulse delay range.  

As of now the Whites V3/V3i is the only detector on the market today that can kind of do that by comparing the 22kHz and the 3kHz signals real time so that you can see and compare the results at the same time.   22kHz screams on everything,  the 3 kHz say mass, no mass.  Audio signal gives target size hints    However their coils aren't really built with a tight enough null so there is an inherent limitation to signal size beyond frequency limitations.  But it works.

If Fisher gets something designed that can hunt that environment I would be happy to prove it.

HH

Mike    

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Good view, Mike..., at Spectra is a dimensionally good-sensitive and stable Vrated and Emi resilient coil - it is the foundation for this detector ... For example 6x4 shooter is low RX gain is1050266751_iphoneMarec52018013_DxO.jpg.98e7e245d11bb7b5273ab94ebacc511b.jpg low sensitive to small things ...

well there are also differences in range at different frequencies and multi 3F
 
 
 
 
 
 
 

iphone 5S marec 6 001_DxO.jpg

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Thanks for the feedback Mike.  By the end of the year, I hope, you might get a chance to play with one!

 

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Thanks Rick.  Maybe so.  Maybe not.   I got a call from someone's shipping department a couple of weeks back wanting to send me something.  I was busy and focused on the task at hand only listening with half an ear and declined shipment.   I don't even know who it was that called or what company they were with.   I think I thought it was a phishing scam to get my info and in any event I was in a hurry to get off the phone and not loose my focus.  

El Nino77, that is some work you have done.  I'll have to take some time to review it closer than I have.  

HH
Mike

 

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