Gotta ask this question

Carl-NC said:

No, not really. Silent EMI is interference you cannot hear. It is literally "undetectable interference that the only way to know it exists is your detector having poor performance." OTOH, yes, silent EMI is EMI that is still there, just no noise.

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There are so many factors that can affect detector performance, and if it is undetectable, how do you even know it is there? How would you know when it is a problem? I understand that silent EMI is EMI you can't hear, but if it is undetectable how would you even know it causing a problem?

I ran a BBS with a metal detecting forum before the Internet was public. People from all over the globe would dial-in to T&T's BBS and discuss detecting. I don't ever remember people talking about EMI much less silent EMI. If my detector chattered I sent it in for repairs LOL.

Now I'll admit during my BFO days I didn't really get into detector designs or functions much, but I don't remember ever having EMI issues with my TRs or VLFs. Not until I bought my first Fisher, an F75 LTD, did I experience EMI chatter. I thought the detector was faulty. Once I found out that was the way Fishers run I sold it and never owned another.


I don't mean to make it sound like I'm doubting you Monte or you Carl, I'm just the type that questions everything until it clicks. I would question Henry Ford about his claims about the model T until I had a grasp on the answer. So far I've gotten a lot of explanations of how it could exist, but not a one on being able to prove it is there.

Detector said:

There are so many factors that can affect detector performance, and if it is undetectable, how do you even know it is there? How would you know when it is a problem? I understand that silent EMI is EMI you can't hear, but if it is undetectable how would you even know it causing a problem?

I ran a BBS with a metal detecting forum before the Internet was public. People from all over the globe would dial-in to T&T's BBS and discuss detecting. I don't ever remember people talking about EMI much less silent EMI. If my detector chattered I sent it in for repairs LOL.

Now I'll admit during my BFO days I didn't really get into detector designs or functions much, but I don't remember ever having EMI issues with my TRs or VLFs. Not until I bought my first Fisher, an F75 LTD, did I experience EMI chatter. I thought the detector was faulty. Once I found out that was the way Fishers run I sold it and never owned another.


I don't mean to make it sound like I'm doubting you Monte or you Carl, I'm just the type that questions everything until it clicks. I would question Henry Ford about his claims about the model T until I had a grasp on the answer. So far I've gotten a lot of explanations of how it could exist, but not a one on being able to prove it is there.

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The best way is noticing your detector is not hitting any deeper targets. I have a site a buddy and myself had hit many times and found very little silver. I think I had found one Merc and one Rosie. One day I go by myself cause he is out of town. I started hitting deep wheats and silvers just one after another. It made no sense except they were the deepest I had dug there. Something, I suspect silent EMI had been affecting our detectors, and that particular day it was not as bad. Those deep coins were not just missed. There were to many.

Detector said:

There are so many factors that can affect detector performance, and if it is undetectable, how do you even know it is there? How would you know when it is a problem? I understand that silent EMI is EMI you can't hear, but if it is undetectable how would you even know it causing a problem?

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That's the real issue: you may never know it's there or causing a problem if you can't hear it. There are 2 ways you can test for it: (1) see if a test target is detectable at the full depth you expect; (2) change the frequency offset (if the detector has this feature) and see if it gets noisy.

Now I'll admit during my BFO days I didn't really get into detector designs or functions much, but I don't remember ever having EMI issues with my TRs or VLFs. Not until I bought my first Fisher, an F75 LTD, did I experience EMI chatter. I thought the detector was faulty. Once I found out that was the way Fishers run I sold it and never owned another.

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The T2/F75 were spin-offs of the White's MXT, which was probably the first hyper-gain detector design. Now everyone is making hyper-gain detectors, and this a major reason why silent EMI has become an issue.
Dankowski deserves credit for shining a light on this problem. Very few people (even detector designers) knew what was going on. BTW, I see you don't care much for Tom. I visited him a few years ago and found him to be unpretentious and not at all egotistical. Very pleasant guy who has an exceptional understanding of detectors. I later found out that when I visited he was field testing an Equinox prototype. He carefully hid all evidence and didn't breathe a word about to me, so I also consider him to be very trustworthy. Just my 2¢.

If we look at performance comparisons between detectors, and consider:

- Each detector processes emi differently. One detector might be more aggressive with noise cancelling, while another detector might take a more subtle approach. As such, the performance of each detector can vary depending on the type, and intensity of emi. Ditto for varying ground conditions.

- Intentional or unintentional misuse of a detector's settings

- Detector reps, Nomads, and salespeople that maintain bias.

- A defect with a detector. Which is why others have to be able to confirm or deny the result.

Those are just a few factors that I can think of off the top of my head right now, but I'm sure there are more. So, it seems to me that the typical detector comparisons we see on YT, are most often meaningless.

I found this interesting. It is a report that talks about, what is referred to as "geologic noise" that shows that the geomagnetic field on the earth does indeed affect a metal detector. Also referred to as "Interference".

In fact, it talks about a few specific areas, such as Bosnia, that it can get so bad as to make a metal detector almost useless.

https://www.researchgate.net/publication/3204098_Effects_of_soil_electromagnetic_properties_on_metal_detectors

I don't doubt there could be interference we are unaware of, I'm just thinking it may not be so mysterious, but simply a natural testable explanation.

Unfortunately, as has been mentioned, not much can be done to shield a detector from magnetic interference so where it comes from is more informative than anything.

I did find the frequency of the geomagnetic field is roughly 2 kHz, but the GOe of the geomagnetic field is only about half a gauss. For reference, a refrigerator magnet is about 100 gauss.

When I was very young my best friend's Dad was a TV repairman. I learned a bit from him and one thing was about degaussing a television. Back when they had tubes, over time, the geomagnetic field of the earth would start to discolor the color TVs. I'd use a homemade degausser just a coil of wire, to bring the colors back in line.

Just thinking for the EMI that s filtered out via algorithms/filters/frequency shifting etc. would be better termed as Silenced EMI. Just my opinion LOL.

woodbutcher said:

Seems everytime something new comes out and there's a problem I read posts from guys who have all the answers. ..Fair enough,maybe they're right but maybe not. .. But now this ( silent EMI) seems to be all the talk,and the reason these guys are saying the D2 has issues..And I've read that the equinox also suffers from (silent EMI) now..Seems to be the diagnosis if your machine isn't upto par nowadays..
Ok,here's my big question,,,if the EMI is silent how does anyone know it exists,,,and I've never heard of noisey EMI so what the hell, I mean where are these new theories coming from?

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About 5 months ago, Sharp Shooter did a video with a D2 and a standard Deus to illustrate silent emi.

You may think it's EMI but it just may be climate change lol . sube

Carl-NC said:

That's the real issue: you may never know it's there or causing a problem if you can't hear it. There are 2 ways you can test for it: (1) see if a test target is detectable at the full depth you expect; (2) change the frequency offset (if the detector has this feature) and see if it gets noisy.

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On this, we'll just have to agree to disagree. I just feel there is far more simple answers to poor depth than EMI, be it silent or not. I experience poor depth at times in the middle of nowhere, where I can run my sensitivity at full with no EMI.

The T2/F75 were spin-offs of the White's MXT, which was probably the first hyper-gain detector design. Now everyone is making hyper-gain detectors, and this a major reason why silent EMI has become an issue.
Dankowski deserves credit for shining a light on this problem. Very few people (even detector designers) knew what was going on. BTW, I see you don't care much for Tom. I visited him a few years ago and found him to be unpretentious and not at all egotistical. Very pleasant guy who has an exceptional understanding of detectors. I later found out that when I visited he was field testing an Equinox prototype. He carefully hid all evidence and didn't breathe a word about to me, so I also consider him to be very trustworthy. Just my 2¢.

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I don't have a problem with Tom and I give him respect for his apparent knowledge, I just found his site to be more a fan club than a place to ask serious questions. It may have changed, I haven't been there in over 20 years.

If I remember right, I was a regular but never posted. I always questioned the choice of detector he used for someone supposed to be so versed in detector technology. He had made a comment, well, in his case they're 15 paragraph statements, about how the old Tesoro Inca was a better detector, in his opnion, than the new Whites Eagle Spectrum. Well it just so happen I had used and swore by the Tesoro Inca for many years myself, but bought a Whites Eagle Spectrum that was a game changer for me, so I dared post my difference in opinion. Holy Cow! You'd think I was posting personal attacks against his family. People came out of the woodwork to call me an idiot and that I didn't know anything about detectors, Tom was the "God" of metal detecting.

Now I may not have a degree in detectorology, but I was swinging with the first of them. Back when we addressed Mr. Garrett as Charles. I have been in several of the old detector mags and a book for my contributions to the hobby of metal detecting, and I started possibly the very first online metal detecting forum in North America in the 80s, so I'm not totally an idiot when it comes to metal detecting. I was a bit put off that Tom didn't ward off his attack dogs, but more relished the entertainment.

But that was many years ago. As you can see, I'm over it LOL.

For this reason, I give respect where respect is due, but not just because of the name. If I sound crude it is not intended, but I do have a problem holding back my thoughts or opinions just because of who someone is. We all make mistakes and I question anything until I am given something that changes what I know.

woodbutcher said:

Seems everytime something new comes out and there's a problem I read posts from guys who have all the answers. ..Fair enough,maybe they're right but maybe not. .. But now this ( silent EMI) seems to be all the talk,and the reason these guys are saying the D2 has issues..And I've read that the equinox also suffers from (silent EMI) now..Seems to be the diagnosis if your machine isn't upto par nowadays..
Ok,here's my big question,,,if the EMI is silent how does anyone know it exists,,,and I've never heard of noisey EMI so what the hell, I mean where are these new theories coming from?

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Woody, I think its possible, you can't see or hear an electric current but just touch an open line and your reminded real fast. And as far as not knowing about it in the past, we learn about new things all the time. Back in the day it may not have not been so prevalent and with all the increase of electronics these days that could cause or at least contribute to it. I haven't read all the comments but if I read correctly, Dankowski, if he suspects silent EMI he will do an air test on site. I might give that a try.
I have had a few experiences lately that has me wondering. At a recent yard permission, a 30s build I could not get a target over 3 in. deep. I dug over 4 bucks in clad and just 2 wheats. I blamed it on the dry ground and ask the lady if I could stop back late fall when the ground has a good soak. Now when swinging, in all metal I could hear iron but the machine was chatter free. But when I would put my machine down to dig it would go nuts. I would try facing the coil in a different direction but that didn't help. And this happens on alot of places I hunt. Now my last yard permission, same thing, almost 3 bucks in clad, a Merc and one wheat. Not a target over 3 inches. Also the machine would chatter away when set down. Two days later I go back, we had no rain, I changed nothing and started digging almost another 2 bucks in clad from the same area I had been over but this time I was hitting 6 and 7 in. coins. And guess what, no chatter when I set my machine down that day. And one thing to note, I usually don't see much depth loss in dry ground, maybe a little, For me it seems to up average the #s a bit. And makes digging a pain. Just some of my thoughts. Mark

markinswpa said:

Woody, I think its possible, you can't see or hear an electric current but just touch an open line and your reminded real fast. And as far as not knowing about it in the past, we learn about new things all the time. Back in the day it may not have not been so prevalent and with all the increase of electronics these days that could cause or at least contribute to it. I haven't read all the comments but if I read correctly, Dankowski, if he suspects silent EMI he will do an air test on site. I might give that a try.
I have had a few experiences lately that has me wondering. At a recent yard permission, a 30s build I could not get a target over 3 in. deep. I dug over 4 bucks in clad and just 2 wheats. I blamed it on the dry ground and ask the lady if I could stop back late fall when the ground has a good soak. Now when swinging, in all metal I could hear iron but the machine was chatter free. But when I would put my machine down to dig it would go nuts. I would try facing the coil in a different direction but that didn't help. And this happens on alot of places I hunt. Now my last yard permission, same thing, almost 3 bucks in clad, a Merc and one wheat. Not a target over 3 inches. Also the machine would chatter away when set down. Two days later I go back, we had no rain, I changed nothing and started digging almost another 2 bucks in clad from the same area I had been over but this time I was hitting 6 and 7 in. coins. And guess what, no chatter when I set my machine down that day. And one thing to note, I usually don't see much depth loss in dry ground, maybe a little, For me it seems to up average the #s a bit. And makes digging a pain. Just some of my thoughts. Mark

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Totslly agree. In fact, many of my questions started with me asking what has changed to cause all the EMI. Especially when you still have a detector that 20 years ago was quiet as a mouse, but now suffers EMI a lot. Obviously, something in the surroundings has changed, and not just detectors being more sensitive. That could be some of it, but it doesn't explain away my now noisy detector. I happen to think a lot comes from motion detectors and wireless routers.

The reason I believe this is that I really notice bad EMI at schools now. Places I have been hunting for years, and with detectors that now have EMI issues that never had before. Well, I guess unless you throw in "Silent EMI" and I just never heard it before now.

MuddyMo said:

I don't know if this is emi or what but I have days when many strong over the air tv stations won't come in. A lot of those times, for a few hours, I'll start receiving stations from other cities that I usually never get ANY signal from Crazy things go on in the atmosphere whether man made or mother nature.

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I imagine that is like HAM radio, after they are all signals transmitted in the atmosphere. With ham radio and CB the bands open and close according to sunspot activity which will affect the different ionization layer strength and height above ground. Thus on some days/nights you can only hear close up ham and CB stations. on other days you can hear stations across the country or from other countries. We call this skip. I am guessing it can work with TV stations to a lessor degree.

I am thinking that there are some guys that just love to be the first to report a flaw in a new detector. It was like back in the 1990's some pointy head found out that a new intel chip had an error.

The Pentium FDIV bug is a hardware bug affecting the floating-point unit (FPU) of the early Intel Pentium processors. Because of the bug, the processor would return incorrect binary floating point results when dividing certain pairs of high-precision numbers. The bug was discovered in 1994 by Thomas R.


so some are looking for fame doing the same with a new detector. I wonder who was the first person to report that the waterproof equinox 800 leaked?

maxxkatt said:

I am thinking that there are some guys that just love to be the first to report a flaw in a new detector. It was like back in the 1990's some pointy head found out that a new intel chip had an error.

The Pentium FDIV bug is a hardware bug affecting the floating-point unit (FPU) of the early Intel Pentium processors. Because of the bug, the processor would return incorrect binary floating point results when dividing certain pairs of high-precision numbers. The bug was discovered in 1994 by Thomas R.


so some are looking for fame doing the same with a new detector. I wonder who was the first person to report that the waterproof equinox 800 leaked?

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LOL I remember that. I was running a BBS on a 80486 at 66 MHz at the time. I was then hired in 1995 as the Network Administrator by HCA (Hospital Corporation of America) for our local hospital where I had access to the best of the best. Worked there until I retired 2 years ago.

Q: What algorithm did Intel use in the Pentium's floating point divider?
A: "Life is like a box of chocolates." (Source: F. Gump of Intel)

maxxkatt said:

..... Thus on some days/nights you can only hear close up ham and CB stations. on other days you can hear stations across the country or from other countries. We call this skip. I am guessing it can work with TV stations to a lessor degree.

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Skip occurs on AM, I believe TV is in the FM range and you don't get skip.

MuddyMo said:

Skip occurs on AM, I believe TV is in the FM range and you don't get skip.

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This is true.

yeah, I wasn't sure. is it because the wave lengths are too short and don't reflect off the ionosphere?