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Will The Next Gen Detectors Address Emi ???


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Digalicious, Just so you do not feel alone, noise cancels do absolutely nothing for interference. A week ago I did over 20 straight noise cancels in a really bad area with very little affect. Like I said I like to test. Also doing a noise cancel has no bearing on your machines finding ability. I think this might be a shielding issue not software?

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12 minutes ago, dogodog said:

Thanks for the info Chase, Some of my sites are so good, that's just not possible. Electrical interference just does not seem to be the problem. Would you walk away from sites that have a bunch of silver and colonial coins?

 

The only time I run multi is with the 800 and the 6'' coil. 99% of the time I run single Frequency, High EMI areas I'm forced to run 40KHZ. Anything from 4khz to 20khz is bad. I pretty much hunt early in the morning to avoid the worst of it. Sadly I've become fairly good at hunting in the worst of the chatter. But there are days where I just give up. 

 

 

That's all very similar to my experience.

My 9x6 coil or my 6" coil on my Legend, is much more quite in EMI than the stock 11" round coil.

In some of my best sites, EMI is so bad, that all SMF modes are practically unusable. I'm talking about so bad, that 5, 10, and 15 khz are still fairly noisy. 20 khz really begins to quite down the EMI, and 40 khz eliminates it completely.

Thing is, EMI is only getting worse by the day. So ya, manufacturers need to seriously address this issue ASAP.

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3 minutes ago, dogodog said:

Digalicious, Just so you do not feel alone, noise cancels do absolutely nothing for interference. A week ago I did over 20 straight noise cancels in a really bad area with very little affect. Like I said I like to test. Also doing a noise cancel has no bearing on your machines finding ability. I think this might be a shielding issue not software?

Oh I don't feel alone 🙂 See my other reply in this thread about no one able to produce a video of anyone doing a noise cancel, and the noise cancel actually doing anything.

I'm just about to write a post about why I don't think EMI can be mitigated via software. The only true way I can see to mitigate EMI is with shielding, but I suspect that shielding would make the coil very heavy and there would be a significant performance loss due to field warping.

 

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4 minutes ago, dogodog said:

Thanks for the info Chase, Some of my sites are so good, that's just not possible. Electrical interference just does not seem to be the problem. Would you walk away from sites that have a bunch of silver and colonial coins?

If I've I learned anything about metal detecting it is that there are no absolutes, your mileage may vary, and it is a constant battle of balancing tradeoffs.  The end part of my post was provided to be some hopefully helpful GENERAL advice for ANYONE reading this thread - it's what I do and what works for me may not work for you or others.  I don't believe in absolutes or "trap" type loaded rhetorical questions like the one above so I am not going to answer it directly.  I was careful to caveat my advice with "If you can avoid...." Only you can decide if the balance of risk (or waste of time) and reward is worth the effort for what might be there.   I rarely encounter a site, however, that I want to detect because of its potential that I can't somehow make the detector work despite noise.  If you have a better opportunity and can avoid the noise then do so, if you want to detect the site because of the potential payoff despite the noise headache and challenge, then do what you can to mitigate it.  Of course, I'm not saying walk away from potential treasure, that is ridiculous.  On the other hand, if the detector is just dead weight because it is generating noise, then just carry a shovel and pinpointer around and dig random holes if silver is there, you'd do better than just listening to EMI continuously.  It's the same philosophy as trying to exploit a polluted site.  You know there are keepers amongst the trash, it just takes patience, a fast machine, some coil control skills and an understanding that you are not going for depth but shallow "in between" keepers.  You don't give up, you just dial down sensitivity a little and go slow.  Basically, a similar drill to dealing with EMI.

 

17 minutes ago, dogodog said:

The only time I run multi is with the 800 and the 6'' coil. 99% of the time I run single Frequency

I guess I'm missing the context of the "only time I run multi" statement.  Why?  Because all your sites have EMI?  Just trying to understand why you limit the advantages that SMF brings to the game to a very niche situation? 

 

22 minutes ago, dogodog said:

Ground noise I welcome, and its very similar to Culpepper ground.

Why do you "welcome" ground noise? You lost me on that.

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30 minutes ago, Digalicious said:

I then posted the above on another forum, and asked anyone to post a video of themselves, or any other You Tuber, in which the noise cancel quieted down the EMI noise. As far as the replies go, many agreed that noise cancel did nothing for them as well, but no one produced a video that showed noise cancel actually doing anything. I posted the same thing on a Minelab and Nokta Facebook Page, and again, no one was able to produce a video, or provide a link to a video that showed noise cancel doing anything.

If I think about it next time, I will try to take a video, but frankly I would rather detect then take a video of something to try to prove it to someone online.  When I need to invoke it, the D2 noise cancellation routine (frequency shift) does noticeably help compared to the Nox 800 and 900 noise cancel which generally seems futile unless I am trying to cancel out another nearby Nox.  The fact is, however, the D2 just runs more stable than either of my Nox machines in most environments, as a given.  Which means to me that XP took the time to get EMI mitigation right up front in the design rather than forcing the user to resort to in-the-field band-aids like noise cancel.

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When I was researching EMI, I found out EMI wasn't just about frequencies, but rather harmonics as well. It's also in a constant state of flux, and as such, is effectively "random". Not just random in intensity, but also random in frequencies and harmonics.

I believe it can be equated to having no signal input to a TV, and despite switching through every channel, each channel is full of white noise. So how can a detector get rid of random noise that is also in the state of flux without sacrificing performance? Did Fisher not try to do that with DSP on a follow up detector to one of their models? Many were saying that the new DSP model was "dumbed down", "was no longer sparky", "lost significant depth", "lost sensitivity to small targets".

It seems to me that the only way to mitigate EMI via software is to give up and just cheat. What I mean by "cheat", is have the noise cancel reduce the base (hidden) sensitivity, or dumb down the SMF so that it ignores most of the returned frequencies signals, and instead, mainly only processes the returned signal from 1 of the frequencies. If the long press on the Manti does indeed reduce EMI noise that the short press does not, then I think it's because the long press is doing one, or both of those things.

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6 minutes ago, Chase Goldman said:

If I think about it next time, I will try to take a video, but frankly I would rather detect then take a video of something to try to prove it to someone online.  When I need to invoke it, the D2 noise cancellation routine (frequency shift) does noticeably help compared to the Nox 800 and 900 noise cancel which generally seems futile unless I am trying to cancel out another nearby Nox.  The fact is, however, the D2 just runs more stable than either of my Nox machines in most environments, as a given.  Which means to me that XP took the time to get EMI mitigation right up front in the design rather than forcing the user to resort to in-the-field band-aids like noise cancel.

I'm not arguing that some detectors may be more quiet than others in EMI. Rather, I'm saying I have never experienced noise cancel to do anything, nor have I seen it do anything in the multitude of videos I've watched, in which the You Tuber uses various detectors. Whether it's Calabash, History Revisited, Gigmaster, Paystreak, Iffy, etc. It doesn't matter where they are, or what SMF detector they are using, they do a noise cancel, but the noise remains the same.

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Gotta say I second Chase's comments on the Deus 2, I don't know if the D1 had such EMI mitigation, but I've never really had a problem with EMI unless I was right over buried power (I'd probably not want to dig so that's a good thing), or directly under power lines. Everywhere else I've been able to shut it out almost completely and can find the D2 wide open.

One day I found that Rattlehead's Silver Slayer program dealt well with harmonics, I was right under some really noisy power lines, switched to his program on a whim, and wham - gone. Really freaked me out.

I haven't used anywhere near as many detectors as y'all have, but I bless the fact that I bought a Deus 2 just about every time I'm out. Not saying you need one or anything 😏 🤣 I love my Equinox 600, I can usually bypass most EMI with single frequency but the D2 is a whole 'nother thing. 🙂

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1 hour ago, Digalicious said:

On both my Vanquish 540 and my Legend, noise cancel does basically nothing. I've also watched countless detecting videos, and it didn't matter if they were using the 540, 800, Legend, or D2, because not once in any of those videos did the noise cancel do anything either.

Easy-peasy, I took the liberty of starting the video right at a spot showing noise cancel on the Nox working.  It's an old video I did some years ago showing the Vanquish working better in high EMI than the Nox, so you could go from the start if you wanted also, it's only a short video.
 

Noise cancel is also highly effective on the older GPX series detectors and the GPZ and I can easily be demonstrated working on them.

I still think frequency shift on older single frequency detectors like my T2 works best.

 

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Thanks for the video Vanquish / Nox video Phrunt, but honestly, I'm not sure what it accomplished 🙂

EMI audible noise is often reduced when the coil is on the ground, and you keep moving the nox's coil from on ground to in air. You also do a noise cancel, then as soon as it is finished, you immediately start pushing buttons / changing modes / settings...whatever.

A true test of noise cancel abilities, is having the coil away from the ground and stationary (which is exactly what the manual says to do). Then, press the noise cancel button, and without moving the coil or pressing any buttons, see if the noise is reduced. 

That's the type of video that I can't find. In fact, all I have ever seen from the You Tubers, is that they do the noise cancel correctly, but it does basically nothing. Granted, if someone did post such a video, I would also wonder if the noise cancel is actually "cheating" in one, two, or both of the ways I described in one of previous posts.

 

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