An impossible and insane thought ???

[sinclairuser]

When it comes to SNR one thing i have noticed, is that the same circuit can have quite different SNR depending on board layout.
sorry if that's obvious here, but some of the projects i have built over the years, prove some are not aware of the phenomena.

[mcgov51]

Gentlemen Thank You All for the exchange of ideas and theories that you personally believe is the future, please continue, please.Who knows what unlikely statement, even from a simplistic old far* like me, might lead to a light bulb moment for one of you if given
a fair chance?
All Of You - Please understand . . . I love this hobby just as much as you do and only want to see this country make it as good as it
can be.
Considering the best of the best are still bred and educated here tells me this is our best shot to take the next step even though a
leap seems to be overdue.
We now have a great conversation going on here . . . let's continue and allow each other enough room to contribute without being
ridiculed.We all have different levels of life and professional experience . . . we can benefit from each other . . . if we choose?
I am told we have already reached our limit with the technology we have been using. I am not suggesting to turn MD'g into GPR but
I am curious and hopeful it could be more than it currently is? So are thousands and thousands of others . . . many of which have left
the hobby dissatisfied. Shouldn't we be dazeling people with achievement and drawing people into this hobby? Don't misunderstand
me, we are in a pretty good place with what we have . . . especially in comparision to 30 years ago. This hobby has enjoyed
many advancements for sure . . . but the voice still being heard out there seems to be saying . . what have you done for me lately?
Mr. Dave J. - WOW . . . and I have a CZ-20/21 & a 1266X with a Depth Master Champion . . . a type of analogue audio booster / filter.
It's the little things like this that grab my attention and cause me to wonder.
Mr. Carl C - NC - Appreciate your knowledge and devotion to this hobby by Adm'g this gathering place for the worlds best.
Apparently I did get off on the wrong foot here, didn't mean to upset or unnecessarily bother anyone . . . Sorry.
Mr. Carl C. - Completely forgeting the now proven not so good idea to double depth . . . for the moment . . .
AND ALL OTHER CONTRIBUTORS . . .
When speaking of audio I/O and manipulation, I don't think you will disagree, a lot more is possible with digital than analogue and with
much better results and . . .
Without a doubt MD'g is becoming . . . more and more . . .digital.
What exact kind of filter . . . I don't know? I am not an engineer. We are probably talking about a noise reduction / elimination circuit ?
I guess the basis of my . . . some kind of improved noise filter / circuit? suggestion . . . is to find a way to use it to combat the below and
above ground unwanted noise we all experience . . . especially at the beach and high mineral areas like VA and the Gold Fields.
I think . . . adequate technology has been here and available for years ?
If room on the PCB is an issue for an additional circuit let me suggest this . . . I built computers for a period of time . . .
For many years the biggest bottleneck / hangup / problem with the computer as a whole working unit was that they would freeze up.
Why? The video card . . . it could not keep up and was not optimized to perform at a level to match the rapidly advancing speeds of the other parts.
It became the weak link because you can only get so much memory on one card with a fan and that's it. So someone had the simplistic thought to
make 2 complete cards designed to run as one by being cabled together and very capable of keeping up with the advanced speed of any of the other parts.
They call it shotgunning
The same thing in theory ( 2 PCB's ) could be utilized inside of a MD Control Housing for any thing necessary . . . couldn't it?
It's simplistic thinking like this that sometimes saves years and promotes rapid advancement. Where there is a will . . . there is a way.
Wouldn't this by itself allow for deeper / maximum hunting at todays current coil capabilities? And perhaps allow for taking a shot at what it might take to further
depth as a possible next step.

[mcgov51]

Then . . . before I fell asleep last night I had a simplistic thought . . . we already have Iron & Target Disc. to include Notching which acts a lot in the way we are discussing how to combat noise . . .

Would it be possible ? to have a 2nd and Seperate Disc. Circuit . . . Multi. Level just like we already have . . . But Just For Noise ?

I believe the kind of noise we are discussing here has one common characteristic to it . . . Motion . . . It does not require any . . . it is there in full
avengeance without any motion of the coil.

This could be a golden key to open the door ? . . . Just Food For Thought.

HH TO ALL NO MATTER WHAT YOU ENDEAVOR BUT ENDEAVOR.
Life is short and we only get one shot at this.

[Overtheedge]

"... the best of the best are still bred and educated here ..."
Not sure where here is, but I find that more than a bit arrogant.

"... a lot more is possible with digital than analogue ..."
Utterly false for many aspects of electronics. Digital can only simulate analog. Classic example is in the communications field. Digital TV has a much shorter range per kw than NTSC. Like MDing, just transmitters and receivers.

"... I don't know? I am not an engineer."
Some, perhaps many of us ARE engineers or electronic technicians.

"... The same thing in theory ( 2 PCB's ) could be utilized inside of a MD Control Housing for any thing necessary ... "
You might wanna look inside several of of the newer MD designs.

I might not always agree with mikebg, but SNR is mighty important and not just because I'm also a ham. BUT, there is a limit to how much noise can be eliminated. If you don't minimize noise in the front-end, you are gonna have problems with it further down the circuit.

Digital is not the universal panacea you imagine it is. And in the end, everything digital MUST be converted back to analog for homo sapiens to interpret. TANSTAAFL Therefore we introduce more noise during each conversion.

"... a simplistic old far* like me ..."
Ain't nothing wrong with simple and I might beat you on the old issue.
eric

[mcgov51]

Gee that was classy. Strangers can sometimes say the darnest things.

Again, If you don't want to contribute to this dialogue then please ignore the post.

I am hopeful to see this thread continue, if not on this open site that values
Freedom of Speech then in the back rooms of those responsible for creating what we use.

Oh . . . and "HERE" is the U.S.A.

[Gwil]

Just to return to the "sixth power/64x" question for a moment: people have been arguing about this for years. It seems to me that someone, somewhere must have done the obvious experiment of connecting an oscilloscope to a suitable point in a detector and checking how the target signal diminishes with increasing distance. That should settle the matter. If they read this I hope they will post the results and then we'll know where we are.

[mcgov51]

Good Question Gwil . . . and since beginning this post I have been trying to form an opinion of what is the answer in regards to power . . . ?
Because it seems a lot of good work has already been done and yet . . . I do not think . . . there is a clear winner?

Both extremes have been explored . . . ( well more than explored ) made to succeed . . .

A Lot More Power . . . Various contributors addressed the "Rule of 64" and some High Powered PI Work by Mr. Eric Foster was noted.
Or Less Power . . . At least incrementally . . . Mr. Dave J. -
Back in the early 1980's, I was happy to get 7 1/2 inches air test out of the 1260-X. Not bad for a motion discriminator of that era. Nowadays with the Tek and Fisher SE's the air test limit is about twice that. Every now and then I ask myself how I doubled air test depth while actually reducing power consumption, rather than running the thing on a truck battery and having a leaf blower aimed at the cooling fins on the searchcoil. The answer: half an inch at a time, fifteen times in fifteen different ways.
--------------------------------------------------------------------------------------------------------------------------------------------
I've read what he has said 4 times and I'm still going over it . . . It takes me time.

All I know is if your target is at 18" and your coil cannot detect beyond 12" ( no bounce for your RX to receive ) then you need to go home.
And it seems as though that strata depth has been picked clean many years ago.

I understand deep ground signal & noise ( from below & above the ground ) can be a major challenge . . . which is why I raelly enjoy hearing
the experts toss something out to us even in some non-descript generic way . . . I understand how secretive this stuff has to kept but . . .

In regards to noise . . . it's a shame you just can't hook up an Equalizer to the audio circuit and just dial it out . . .
Music has more tracks and channels than a MD . . . right ?
Mr. Dave J. says before we can go any deeper the noise has to be eliminated . . . and who can argue with that ? High Powered or Low Powered.

I imagine coil shielding is as good as it can be ? I did not realize (before I got into this hobby) that so many above ground forms of EMI existed
and caused as much havoc as it does ?

Utt OH ? Here it comes? I'm having another simple spell . . .

There are so many things on that beach . . . cell phones, short wave marine, micro wave, satelite everything, walkie talkies, wi-fi everywhere . . . how come those items do not become affected ?

None of them are shielded ( that I know of )? And they operate across much greater distances not just 12" ?

[Dave J.]

Just to return to the "sixth power/64x" question for a moment: people have been arguing about this for years. It seems to me that someone, somewhere must have done the obvious experiment of connecting an oscilloscope to a suitable point in a detector and checking how the target signal diminishes with increasing distance. That should settle the matter. If they read this I hope they will post the results and then we'll know where we are.

The "law of 64" is fundamental magnetics physics, any "argument" comes from ignorance or misapplication. The 'scope work is a routine part of metal detector design engineering, been done untold thousands of times by probably thousands of engineers over the last 100 years. But, you don't need any of that. All you need to find out for yourself is a fairly sensitive metal detector, some coins, and a wooden ruler.

--Dave J.

[mcgov51]

As creator of this thread . . . I suggest we invoke "The Law of 7" . . .
i.e. 7 days of pondering what has been shared with us . . . let's give those
who choose to answer our daydreams . . . a rest. Sleep on it !

Thanks to All

[Aziz]

The "law of 64" is fundamental magnetics physics, any "argument" comes from ignorance or misapplication. The 'scope work is a routine part of metal detector design engineering, been done untold thousands of times by probably thousands of engineers over the last 100 years. But, you don't need any of that. All you need to find out for yourself is a fairly sensitive metal detector, some coins, and a wooden ruler.

--Dave J.

Dave, you are trying to force me to take a lot of blue pills again. Don't you? *LOL*


But you are wrong with the "law of 64".

Hey, let's start the Metal Detecting Nobel Prize (MDNP).
Anyone, who solves this issue (incl. the math proof), will get a MDNP and will be very much respected on all the metal detecting forums.

Deal?
(I'm not allowed to contribute, I'm in the Nobel jury committee .)

Cheers,
Aziz

[Skippy]

Speaking as one of the many engineers who has measured target signal vs.distance, I have seen the inverse 6th power effect. This was for a conventional DD coil, I can't comment on other arrangements, 2-box, figure-8 types etc. Once your target is at a distance of twice the searchcoil diameter, the 6th power is pretty accurate. At 1 to 1.5 coil-diameters away, it is less severe, I tend to use inverse 5.5 power in my calculations, as I did in my first post on this topic.. However, this isn't the real problem, 5th or 6th power is of little importance. The locomotive horn is the problem...

[mcgov51]

Neutralizing the EMI Locomotive:
Audio Channel:

1 = High-Tone Silver
2 = Mid-Tone Copper and other similar composite alloys
3 = Low-Tone Gold, Nickel and other composite alloys Little girls voice
that also fall into the low-tone range.

EMI Locomotive Proposed Possible Solution:

Silent No-Tone Channel used for EMI Cancellation Only
4a – Above ground
4b – On and below ground

Without any special sensor or microphone ( your Coil RX is good enough and already telling you what the assault is )
and away from any kind of target source *sample the noise source(s) . . . have a way to electronically map it.

If the MD had an available channel for this and had *a program to take the sample(s) results and then build & run a reverse
mirror image, then the noise(s) . . . “The Locomotive” would be gone and only the whisper of the little girl would remain ?

Yes . . . It would seem that a simple. . . very small iPad type CPU and App would easily do the trick and yes require integration but . . .

That’s what my simple mind tells me . . . I am not an MIT PHD Extraordinaire . . . but this will work.

That Locomotive has ruled those tracks long enough . . . wayyyyyyy too long.

[Qiaozhi]

. . very small iPad type CPU and App would easily do the trick and yes require integration but . . .

I'm afraid your simplistic view of metal detector technology is leading you up the garden path, at which there is a dead end.

Many so-called "impossible and insane" solutions that can "easily do the trick", or require you to "just dial it out", ultimately fail when you attempt to put them into practice.

Also, you cannot make comparisons with "cell phones, short wave marine, micro wave, satellite everything, walkie talkies, wi-fi", etc., as metal detectors work in the near-field region, which occurs about 1 or 2 wavelengths away. In the case of a typical VLF detector, this means the near-field region extends for about 30 km. The near field region is strongly reactive, and the field energy falls off (despite Aziz's protestations) as a function of . For radio wave propagation, a metal detector coil would need to be around 2 kms in diameter. Luckily we do not require such a large and impractical setup, as detector coils work by induction, like a transformer.

[Aziz]

Mr. Q!,

you would be mathematically talented to challenge and win the Metal Detector Nobel Prize.
Dare to challenge?

Aziz

[Qiaozhi]

Mr. Q!,

you would be mathematically talented to challenge and win the Metal Detector Nobel Prize.
Dare to challenge?

Aziz

I was tempted ... but then my "voice of reason" reminded me that I have other more important stuff to be doing, and not to get sidetracked. In fact, I shouldn't even be wasting time typing this message.