I told ya

[Carl-NC]

What is the frequency of the oceanic magnetic field?

[ivconic]

If I answer you by telling you the exact value; you will ask: "How do you know, how did you measure?"
Point is; there is no exact fixed value and I bet you knew that before asking.
It can be measured in a period of time using proxy methods. Not directly.
But ok, let me accept this childish game and give you an asnwer.
Yes it is ultra low frequency range, 6-20Hz most of the time.
Satisfied?
But that has absolutely nothing to do with the topic.
Ocean activities also do not have a direct impact on the problem of metal detecting, but a "proxy" impact.
And that is the famous "mineralization" of soil, about which there is so much "farting" on the forum in all directions.
Have you ever asked someone what "mineralization" soil is?
(By the way, the effect referred to is not best described by the term "mineralization"... but it is a term that has somehow caught on in these circles of ours).
Literally; "mineralization" would mean the amount, type and nature of minerals in the soil.
But that's only part of the effect description. Just a component in the whole story.
Ocean activities therefore affect the soil, globally, and the soil then changes its "behavior" (properties) under these influences, which is later reflected in the behavior of the detectors on the same soil.
That is why, during the same day, different behavior of the same detector on the same soil and on the same targets is often noticeable.
And it doesn't have much to do with any "ocean magnetic field frequency" anyway.
Which is certainly low, falls within the described range... and look... what a "miracle"; somehow it falls into what you get after LPF/HPF filtering in a conventional detector!?
Carl, I guess you know me a little better, I won't play these games.
Read, research, there is so much published in numerous articles.
I spend days and hours searching and reading piles of articles published by various institutes.
Not because I have to and because someone is forcing me, at least not for the reason that I would later come here and show others how much I know... I don't really care about who will think what.
But for the reason that I am personally interested in it and I have a strong motivation to deal with such things and to learn as much as possible.
And I will always be happy to share what I know with others. But when some cynical circus clown appears, full of himself and begins to provoke... I suddenly lose the will to continue being there.
My time is too precious to waste it on such nonsense.
I thought I'd develop a serious topic here... but as always I see that it doesn't make sense, I give up.
There will always be some fool who annoys with his intrusions and turns the topic to the stupid side.
Stay healthy!

[ivconic]

But I didn't accidentally start this topic in the "Magnetometers" part of the forum.
Because I wanted to direct the story more in that direction.
But then some "PI expert" (clown full of himself with his piles of horschmidt) showed up and instead of realizing that this
is the "Magnetometers" part of the forum (where such clowns don't belong); he gave himself the freedom to come here and bore with his "super knowledge of everything and anything".
It made me very angry.
You practically have no place on this forum to "hide" and talk to people of good will.
Some "simulator effendi" with his "excessive knowledge of everything that exists" will already appear there...
I've "left" the forum "100" times so far ... I'm really sick of those.
I will no longer be silent and not react to those hideously ugly human figures.
I've had my say, I stand by it, and there's no way I'm going to change my mind.
And with this, I close this topic as far as I'm concerned.
I will not participate anymore.
All this has been repeated too many times over the years behind us.
Enough is enough.

[Carl-NC]

The reason I asked is because the article doesn't explicitly say, and it may be something you can actually test for. Set up a large TX loop, maybe 20m diameter, and put a sig gen on it. With different amplitudes & frequencies, see what happens with the detector when hunting inside the loop.

The Earth's field (including effects from ocean currents) is constantly fluctuating by small amounts, but nowhere near even 6 Hz AFAIK. The article suggests this is a tidal effect which (to me) would suggest a frequency of 23uHz, and I would immediately consider that to be much too low to affect metal detectors or even differential magnetometers. It also suggests the tidal effect to be 6000 times weaker than the ambient Earth field, which is around 56uT where I live. This would put the oceanic portion at maybe 9nT. A really good magnetometer could pick that out of the ambient field, but I doubt it's enough to affect a metal detector. But, again, it's something that could be tested.

I also didn't notice this was posted in the Mag forum, I only look at the "Last 24 Hrs" feed and don't pay attention to the forum location.

[moodz]

I hate to say I told ya...
...
For years, I have been repeating the same story about something that is directly related to this and has a radical impact on our hobby, directly on the work of metal detectors...
I probably have at least 50 posts, scattered across many forum topics, where I wrote the same thing. No one ever paid attention to those posts. There was not ONE reaction... all these years.
You cannot fully understand the behavior of metal detectors in real conditions without knowing about this process.
Of course, you will already know everything and much more about the operation of metal detectors... in the simulator, of course.
I rest my case...

Take a chill pill Ivica .... your own post above admits to posting all over the place about this "issue". Then in the same breath you start attacking the "ignorance" and "simulator"

The pot calls the kettle black in IMHO.

I was only pointing out that these ocean current generated fluctuations ( whilst interesting and thanks for bringing it up ) are not at the top of the list in mitigating noise sources for magnetometers or any other sort of detector.
( also the 95% drop in detection distance of a magnetised hat pin from 800 mm to 40mm .... really ???? are we to believe that )

[pito]

What is the frequency of the oceanic magnetic field? = What frequency is Earth's magnetic field?

11.79 Hz
The earth's magnetic field has a frequency of 11.79 Hz (cycles per second). There is also a second frequency within the earth's ionosphere called the Schumann Resonance, which resonates at 7.83 Hz. This frequency is created mainly by lightning strikes… approximately 7 million per day.Aug 30, 2022

[moodz]

Just out of interest here is a paper from canadian researchers using a TEM system that has femto Tesla precision and can detect large conductive structures upto 2000 meters ( shows also detecting truck at 250 meters ).

nano = 10-9
femto = 10-15

many orders more sensitive.

Lamontagne_OnTime_EM_abstract.pdf

[Tinkerer]

Just out of interest here is a paper from canadian researchers using a TEM system that has femto Tesla precision and can detect large conductive structures upto 2000 meters ( shows also detecting truck at 250 meters ).

nano = 10-9
femto = 10-15

many orders more sensitive.

Lamontagne_OnTime_EM_abstract.pdf

Very interesting

[Tinkerer]

What is the frequency of the oceanic magnetic field? = What frequency is Earth's magnetic field?

11.79 Hz
The earth's magnetic field has a frequency of 11.79 Hz (cycles per second). There is also a second frequency within the earth's ionosphere called the Schumann Resonance, which resonates at 7.83 Hz. This frequency is created mainly by lightning strikes… approximately 7 million per day.Aug 30, 2022

And then there is the impact of the sun's magnetic storms on the earth magnetic field. Up to 1000nT.
And the daily variations from morning to evening in the tens of nT.
And all this depends on where on earth you are. For example, in Brazil, the earth magnetic field is less than half of Carl's location. About 22,000nT. And of a different angle to the earth's surface.

[ivconic]

Ok, sometimes my personal problems disturb me to the point where I become overly sensitive and aggressive... which is very unnecessary, I'm sorry.
...
Listen people, I wouldn't think of dealing with this issue; if I didn't notice those strange changes in the behavior of various detectors almost every time I go out into the field.
And I really talked about it everywhere on the forum, on various topics. To the extent that sometimes I even bored myself.
The problem is complex and does not consist of only one factor.
But since I started to deal with magnetometers in a little more detail; I noticed that the essence of the problem lies in the nature and behavior of the earth's magnetic field, on a global scale.
And it reflects locally, more or less depending on the location, as Tony noted.
A handmade magnetometer, be it an EPE from 2003 or my Euromag 3D from 2018 is able to "see" these fluctuations at great distances. "Excess" repeated several times becomes a visible rule.
While I'm working on Euromag 3D and the sensor tube is sitting on the table in the workshop, 50-100 meters from the road, cars pass by randomly. I also notice clear readings of the changes.
At first I didn't understand what it was about, I interpreted it as some local disturbances from the workshop. Until at one point I caught the rhythm of what was happening.
Once upon a time, I came across an article in which the author explains how he placed a sensor 2m from the top of the roof of the house, insulated it thermally and created a logging system
for long-term monitoring of the sun's activity. So I replicated it myself.
The results are phenomenal to say the least.
And only then you understand the mutual effect on everything that surrounds us.
And as someone who often goes out on quests with a detector; very often even then I see those changes in the form of changes in the operation of the same detector, on the same soil, and with the same targets.
During the day, the changes are to be drastic. Especially at times of the year when the sun drastically changes its activities during the day.
It is indeed so obvious and clear that there is no need to doubt it anymore. And no one anywhere has ever paid serious attention to it here among us detectorists.
...
"...( also the 95% drop in detection distance of a magnetised hat pin from 800 mm to 40mm .... really ???? are we to believe that )..."
You don't have to believe. This is not about belief but about facts. Checked multiple times.
There is a simple magnetometer project that is super sensitive and can prove this. I thought I'd post the whole project, but I'll wait for now.
I am convinced that all disagreements and misunderstandings lie in the fact that we are quite different in location.
And as Tony said; the mean reference values of the earth's magnetic field strength are different from location to location. At my location, the average reference values are 47-49000nT.
But I have been following this for a long time, since 2004 more seriously. And the news that the poles have changed location by a full 11 degrees is true.
The planet has changed its angle. Which also affected the changes in reference values at the locations. I have a benchmark "map" that is old and predates that.
I don't have a current situation. I couldn't find it online.
So both the ocean activities and the impact on the story are different.
In this sense, Qiaozhi correctly noted the year from which I referred. But then I found more recent data from 2018, which only confirms the claims.
...
Carl you are thinking right. What you suggest can be done with a giant helmholtz setup. But there is no need.
What do you think... why have I suddenly gained interest in the Compass Depth Doubler recently?!
Who says that metal probes must be connected at the output? A gigantic coil(s) can be connected instead.
I have already done some tests. The results are very satisfactory.
...
I have another example on this topic.
I wrote a long time ago about the Cscope 33XD and how, at certain times of the day, I very successfully locate a thin tube at a depth of 2.2 meters with it, so clearly that the device even
prints the exact depth on the LCD. And then at a certain time of the day, it is not able to measure the depth and the detection signal drops, so it cannot locate it even beyond 1.5 meters.
But when I added to that a hand-made high-power generator at 32.768kHz (clock crystal is all what I could obtain then), as far as 25 meters from the detection site; it didn't matter
what time of day or night it was, the device always clearly and accurately located the pipe and always printed the same depth value on the LCD.
...
These are several totally different and unrelated stories that at first glance have nothing to do with each other and to some it will seem that they have nothing to do with this topic.
But it's not like that. They all confirm one and the same thing.
Due to constant activity and changes in the earth's magnetic field, due to "fluctuations" as Carl said; targets in the ground... that is, the signal of targets in the ground,
which is often weak and thin; is often swamped by these changes.
There you go... written with plenty of value for further thought and investigation.
"..( also the 95% drop in detection distance of a magnetised hat pin from 800 mm to 40mm .... really ???? are we to believe that )..."
Yes, Moodz, I have a project for a simple magnetometer, this time not using the FGM type of sensor that is able to sense it.
"...are not at the top of the list in mitigating noise sources for magnetometers or any other sort of detector..."
You are both right and wrong here. It depends on other factors.
If you work next to the transformer station, then you are right.
Or if you work next to a train track, you're right again.
But if you work with a detector far in the hills, mountains, very far from any artificial source; then you are wrong. Then this becomes the main disruptive factor in the search.
I cannot speak generally for all of us. I am making assertions and observations here that are explicitly valid for my conditions.
And not only mine. Numerous colleagues throughout Eastern Europe and the Balkans are also searching in very similar conditions.
Interesting terrains are mostly in such places. Away from any artificial magnetic fields, interference, noise, etc.
And from numerous contacts with colleagues from the far north of the continent, I learned that they also have quite similar search conditions.
In one word; the number of such cases is not negligible.
It is large enough that this becomes a serious issue for further consideration.
...
Huge post!

[Detectorist#1]

ОК! All you are rights. This discussion is endless. One clever man, when the humanity discover that the atom is not smallest part of the nature, said - maybe the universe is limitless on macro and in micro direction. The factors that have influence on the metal detectors maybe also are endless. All solutions have to be used is specific areas and for specific targets.