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Fisher Impulse AQ Discrimination Explanation

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3 hours ago, ALEXANDRE TARTAR said:

Now, I focus on the development of gold nuggets metal detectors, I test my models with 2 different evolving technonologies.

In all cases the outcome will be for this year.

Very exciting, Alexandre!

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On 12/26/2019 at 1:02 PM, ALEXANDRE TARTAR said:

Iron is detected in all-metal mode by its characteristic double beep (provided the sound is at the limit of detection). This double beep is also present in Tone mode.

After reading the above I was under the impression that iron and steel could be rejected by the user once they had become familiar with it's tonal clues.  Elsewhere LE.JAG had posted a photo of an outing showing all of the recovered targets.  I have cropped and resized that photo which has created the graininess.  My concern are the number of rusty steel crown caps to the right in the photo.  Beaches I detect are heavily littered with these and multitudinous digging 15-20 inches is not going to help efficiency or my back.


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If you go to the original post in this thread I explain why expecting to not dig any ferrous with this type system is unrealistic. Even VLF detectors struggle with many bottle caps. Bottle caps are a mixed target and some literally have a non-ferrous liner or coating. PI detectors do not discriminate based on ferrous/non-ferrous but on different time constants or signal decay rates. Like any discrimination system increasing target rejection can affect target signal strength and therefore depth. There is some kind of ferrous target at every possible resultant time constant and all you can do is maximize gold ring returns while minimizing ferrous returns. This must all be done while also attempting to retain maximum depth so it is a judgement call where trade-offs will be made at the discretion of the operator. Some people will choose all metal for maximum performance but dig more trash. Some will choose to minimize trash with some resultant loss in performance and loss of some good targets. Most will be somewhere in the middle depending on location and settings. It’s a choice each person will make for themselves.

I think getting expectations too high will be damaging and one reason I started this thread was to be sure people are realistic about pulse induction discrimination at this stage of development. There is no way I am going to be disappointed as I simply want better than what I have had in the past and I am sure Alexandre is going to deliver. The results however will be very dependent on the exact beach location and the particular mix of ferrous targets. I expect at some locations hardly any ferrous will be recovered. I also expect some places with an unlucky set of circumstances will still see you digging plenty of trash to get the gold. Operator patience in learning the detector will of course matter a lot and those who have hunted more by ear than by numbers will be ahead in the game.

I think the more experienced pulse users with realistic expectations are going to love the Impulse AQ. I also think there will be some who get it thinking it is a VLF type discriminator and they will end up disappointed and blame the detector. Anyone having any doubts in this regard should simply wait it out and not be first in line to buy one.

I also think the best results will come from high mineral locations where VLF detectors struggle the most, favoring west coast and volcanic island hunters. Hunters in Florida pure white sand where VLF detectors work as well as is possible will see less benefit compared to something like a CTX 3030 with a 17" coil. PI detectors do best compared to VLF detectors where the ground conditions are the worst

Again, I do not have nor have I ever had an Impulse so this is my best explanation of what I think is realistic based on my having been involved in this type of detector for about as long as they have been around. When I was a dealer I believed in undersell and over-deliver and never regretted it. I do not have a horse in this race at all. But the fact is I very much would like Fisher to do well with this machine and continue to offer competition while advancing the technology. That will only happen if people are properly educated about what to expect so as to not have any unpleasant surprises.

Fisher Impulse AQ metal detector

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I totally agree with Steve on the above. Anyone going from a VLF to the Impulse may be in for a bit of a surprise. Even though the Impulse sounds like it will offer new advancements in both depth and discrimination, it's still a PI. It will most likely require 100's if not 1000's of hours to fully understand it's potential.

You're still going to dig lead weights, bottle caps, pull tabs, etc. And a greater depths. But as you put in the time with the Impulse you may be able to avoid certain types of trash just like other PI's based on target response and other audio clues.

We know the Impulse is going to see the biggest gains on mineralized beaches where VLF's struggle. But on mild beaches the VLF with target ID might still be the go to detector.

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9 hours ago, LowTide said:

After reading the above I was under the impression that iron and steel could be rejected by the user once they had become familiar with it's tonal clues.  Elsewhere LE.JAG had posted a photo of an outing showing all of the recovered targets.  I have cropped and resized that photo which has created the graininess.  My concern are the number of rusty steel crown caps to the right in the photo.  Beaches I detect are heavily littered with these and multitudinous digging 15-20 inches is not going to help efficiency or my back.


This image is from
of a test report carried out on volcanic sand



do not confuse the volcanic sand
with the other white or black sands
It's not the same thing at all

on the volcanic sand setting
you lose the multi tone
it automatically switches off (mute mode)

then you set the rejection of iron
by the rejection knob

you have the choice
push the rejection = you will lose big gold rings
and lose deep (we're talking about volcanic sand)

cut only the volcanic sand and dig out

the tester of this report who knows well / his beach
prefer to cut only volcanic sand
and dig everything
I would've done the same thing

on its beaches / never prospect
the report (in gold) is going to be huge
the test hunter plans to make more than 500gr per month
when he has the right beach conditions
here, the test was carried out at one season
or normally it does not chase ..... and you see the result
saw this first test over 6 days

I think , It's possible..




but in this case, you have to dig a lot
and clean everything
again, once / the volcanic beaches
are virgin // they have never been prospected
no detector works on this sand
tried vlf / multi frequency / TR
or other pi

so I think on this type of sand
there is interest in making a little effort

but it is not compulsory
you can push the rejection all the way
you will still find gold (but you will have less ...)

you can also use volcanic sand mode
on normal white or black sand
the iron cut will be even stronger
than in Ton & Mute modes
you will still find gold (but you will have less ...)

It is a choice to make
the thing to remember is that AQ
can find gold / there or nobody can do it ...

it's up to you to find the right settings
according to the sand conditions
and depending on the efforts you are ready to make
to always find more gold



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I posited the question and I feel the replies have been wonderful, Kudos to the time and detail in your replies.  I believe perspective buyers will have learned a great deal, especially in the reply from LE.JAG.

My question is based on experience of detecting black sand beaches filled with gobs of iron/steel trash.  Once in a great while a PI detector will be spotted in these locations, but you only see a person use them one time because the digging becomes intolerable. 

Based on some past postings my perception is that an Executive Summary of this detector would be:  A detector capable of detecting deep gold on black sand saltwater beaches while ignoring and seeing through/past iron/steel trash.  This perception was created by the level of exuberance centered around this capability.

Thank you one and all!

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There are two basic mindsets at work in metal detecting. There are some that prefer to maximize returns per dig by using discrimination and who are willing to give up depth to have good discrimination. Then there is the power crowd who tends to go for power first with discrimination being a secondary concern, more a bonus than anything.

Nearly all park detectorists fall into the discrimination camp. Nearly all serious gold prospectors fall into the high power camp. Beach and relic hunters swing both ways. However, the trend I have seen is that as shallower finds play out and good valuable finds remain at depth, people turn to power over discrimination. A fine example are the Culpepper relic hunters. That is tough ground that really impedes VLF performance. They cleaned things out with VLF, but then nearly everyone switched to pulse induction as the shallow VLF finds depleted out.

Beach detecting is no different. Nobody is going to dig a ton of junk for pennies. But when a beach gets to where a VLF no longer is making many good gold finds you have only two options. Go somewhere else, or break out the big guns. That means pulse induction.

The real question then simply becomes which PI unit to use. I have always favored PI detectors for gold prospecting and beach detecting. VLF detectors have always been more like playthings in my world; it's the PI detectors that put pounds of gold in my pockets.... and yes, I dug many more pounds of junk to get there! :smile:

This is pretty much a rule of detecting. People will do what is easiest. If a VLF means you make good finds while digging less junk that is what people will do. But there comes a time when the VLFs no longer produce, unless you are willing to chase recent drops. At that point some people will go the next step and use PI detectors. And even then there is an eventual end. I have seen many nugget locations go though this cycle. VLF first, leave most of the trash. Then in come the PI detectors. The mindset changes. As long as you can find junk gold still can be found! Ever hear of target masking? So people continue to attack the location, digging everything. And a day comes when you can't even find trash anymore. The location goes quiet as a mouse. Then people start moving rocks and scraping the surface to get the coil closer to the gold!

It's actually inevitable and it will happen on any beach where gold can be found. It is only a matter of time.

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According the most experienced manta/AQ user of them all, LE.JAG, the eep old stuff is found on hard pan where it can’t sink further. When this is at the limits of detection, than all metal, working deliberately and using the powerful and low noise circuitry to give you a return from targets no other detector can reach. 

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