Will The Next Gen Detectors Address Emi ???

[Digalicious]

10 minutes ago, Jeff McClendon said:

I can run them between 70 to 90% of maximum and they will be quiet enough to detect with using most of their SMF modes. Running Deus 2 at 90% using the 9" coil is like running my Equinox and Legend at 80% using their 11" coils as far as the EMI interference experienced. I can run the Legend and Equinox up to 85% using their smaller elliptical coils at those sites. 

I previously mentioned coil size in mitigating EMI. In my experience, going from the 11" round coil, to the smaller elliptical, has a huge impact on reducing EMI noise. I would estimate a 75% reduction. For example, when I do EMI tests in my backyard near those three high power lines, I pretty much have to use the round 11", becuase the smaller elliptical coil picks up so little EMI to begin with, that testing with it wouldn't provide very tangable results.

With that said, I also wonder why exactly the smaller coils are less suspectable to EMI. More specifically, is it simply a matter of the small coil's much tighter field being more "closed" and impenetrable to the EMI?

[CPT_GhostLight]

3 hours ago, UT Dave said:

So far, for me in my urban parks the Manticore does seem to handle EMI quite noticeably better than my Nox 800.  I have not had them both out at the same time to compare though.  But in a couple of parks where I have had to run the Nox in 20Khz and lower sensitivity below 20, I have been able to run the Manticore in SMF at 20+.  Actually have not had to leave SMF in a park with the Manticore yet.  Which is quite different than I was accustomed to with the 800.

I speculate it's got to be more than just the long press, which I believe simply automates the process of running through the channels looking for the quietest one.  Pure speculation but because the Manticore does seem so much better, I think there has to be more to it.  Perhaps the increased TX improving the signal to noise ratio?

 

I was expecting Manticore owners to chime in here as much of the new patented coil design of the M-Core was designed to help fight EMI. I suspect a lot of their new designs incorporate EMI mitigation to compensate for their higher transmit power.

 

[CPT_GhostLight]

28 minutes ago, Digalicious said:

I previously mentioned coil size in mitigating EMI. In my experience, going from the 11" round coil, to the smaller elliptical, has a huge impact on reducing EMI noise. I would estimate a 75% reduction. For example, when I do EMI tests in my backyard near those three high power lines, I pretty much have to use the round 11", becuase the smaller elliptical coil picks up so little EMI to begin with, that testing with it wouldn't provide very tangable results.

With that said, I also wonder why exactly the smaller coils are less suspectable to EMI. More specifically, is it simply a matter of the small coil's much tighter field being more "closed" and impenetrable to the EMI?

There has been much discussion posted about how small coils handle EMI better. It's mostly physics. Smaller coil, less ground and EMI samples to analyze, less filtering required by the processor, more efficient operation.

[Digalicious]

4 minutes ago, CPT_GhostLight said:

There has been much discussion posted about how small coils handle EMI better. It's mostly physics. Smaller coil, less ground and EMI samples to analyze, less filtering required by the processor, more efficient operation.

Ok, but doesn't all that fundamentally come down to the effects of a tighter and smaller field?

On a similar note, I see so many posts on other forums and Facebook pages, in which the hunter is using a stock 11" round coil (or larger) in a high EMI and park like trashy site, then asks what to do about the EMI noise. The typical replies I see to such scenarios, is to lower the sensitivity or use a SF. But a better solution for that scenario, would be to use a smaller coil such as a 9x6 or 10x5. Those coils won't be nearly as suspectable to EMI as the 11" round coil, will have much better unmasking and separation characteristics, and the sensitivity won't have to dropped nearly as much.

[Jeff McClendon]

16 hours ago, Digalicious said:

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.

 

Like Chase mentioned, I would rather detect than make a video and suffer the consequences of having someone critique it the way Simon's was above.

I am not seeing anything wrong with Simon's videos by the way. They do show a noticeable reduction in audible and visible effects of EMI. 

Thank you Simon for posting them.

[jasong]

56 minutes ago, Digalicious said:

With that said, I also wonder why exactly the smaller coils are less suspectable to EMI. More specifically, is it simply a matter of the small coil's much tighter field being more "closed" and impenetrable to the EMI?

It's because coils are antennas too, meaning they can couple with both magnetic and electric fields. Generally, with loop antennas for receiving EM radiation, the rule of thumb is that bigger diameter = more sensitivity. It's more complicated than that since certain sizes/shapes are more sensitive to certain frequencies, 1/2 frequencies, 1/4 frequencies, etc, but that's a basic idea anyways. Close to a loop, the magnetic field dominates, and sensitivity is a matter of flux density, so smaller coils are more sensitive to smaller targets, but less sensitive to EM. Well, with PI's anyways, I don't know a lot about VLF's, but a loop is a loop.

I think a lot of research could be put into reducing noise just with proper coil design. Some detectors seem to still be using generic sorts of coils from decades ago that appear to have very little modern design consideration for EMI reduction included.

For top tier detectors (definitely the $6-$10k gold detectors anyways) I think the entire control unit should be carbon fiber too. Both for weight reduction, but also because it's conductive and thus has the potential to act as a shield itself. I can detect my phone while off next to the side of the 6000 control box, it clearly lacks any shielding at all. 

Same for coils, for PI's anyways, I'm curious if carbon fiber tops/sides and plastic bottoms might be a good method to shield without gaining weight - maybe even losing weight. This is stuff I've mentioned for over a decade though - knowing Minelab reads the forums - and they don't seem to do it ever though, so maybe it just doesn't work. 

I think the whole concept of a "noise cancel" button is obsolete though. Modern computing power is in abundance for cheap on chips today. No reason EMI filtering/noise cancelling/channel scanning can't go on in the background 24/7 and auto adjust as needed rather than press a button. IMO anyways.

[Digalicious]

4 minutes ago, jasong said:

It's because coils are antennas too, meaning they can couple with both magnetic and electric fields. Generally, with loop antennas for receiving any signal, the rule of thumb is that bigger diameter = more sensitivity. It's more complicated than that since certain sizes/shapes are more sensitive to certain frequencies, 1/2 frequencies, 1/4 frequencies, etc, but that's a basic idea anyways.

 

Thanks for that Jasong.

That's what I meant by questioning if the effect was simply due to the smaller / tighter field, or something else in addition to that (like the coil shape as you mentioned).

[phrunt]

17 minutes ago, Jeff McClendon said:

I am not seeing anything wrong with Simon's videos by the way. They do show a  noticeable reduction in audible and visible EMI.

Thanks Jeff, as you know the video was filmed to show the Vanquish was operating at a higher gain more stable than the Nox in that particular EMI environment and I was wondering at the time if it was due to it's elliptical coils.  The video clearly shows the noise cancel at the point I started the video working as the EMI is crazy with ID numbers going wild, the noise cancel completes and that stops, no more false ID numbers, just slight EMI blips, I then move on testing other modes to try find one as stable as the Vanquish.  It was filmed 3 years ago or something and the intended purpose was not to suit Digalicious's argument that noise cancel does not work or I would have focused more on proving it does work in the video, but a side effect of that video was it shows for a short time that noise cancel did indeed stop the Target ID falsing.

If I wanted to prove it does work I could go and film it now, but I know it does so there is little point, I'm not wasting my time doing that video for someone that is intent on believing it doesn't' work.

Noise cancel works fantastic on detectors like the GPZ and even older 4500 too.  The Manticore noise cancel appears to work very well.

[Digalicious]

12 minutes ago, jasong said:

 

I think the whole concept of a "noise cancel" button is obsolete though. Modern computing power is in abundance for cheap on chips today. No reason EMI filtering/noise cancelling/channel scanning can't go on in the background 24/7 and auto adjust as needed rather than press a button. IMO anyways.

The cheap power chips haven't just been in abundance "today". They've been around for a good couple of decades. Yet, the engineers haven't incorporated real time EMI filtering. I think they haven't done so because it wouldn't make any difference. More specifically, in high EMI, all the channels are affected about equally, because the frequency is so close in each channel. Put another way, if the EMI is filtered out, there would be a heck of a lot of good targets that would also be filtered out. One example of that, is how F350 posted about the Silver Slayer program eliminating EMI. It eliminated EMI because that program notches out everything below copper / silver, and since most EMI IDs below copper / silver, the EMI noise was notched out and silenced. That works great if a hunter is cherry picking for the highest conductors, but not so great for everything else.

[Digalicious]

6 minutes ago, phrunt said:

 

If I wanted to prove it does work I could go and film it now, but I know it does so there is little point, I'm not wasting my time doing that video for someone that is intent on believing it doesn't' work.

Noise cancel works fantastic on detectors like the GPZ and even older 4500 too.  The Manticore noise cancel appears to work very well.

My point is NOT that it doesn't work. My point is that IF it does work, it's going to come at a significant performance hit in other aspects. I made that quite clear numerous times throughout this discussion, yet I'm still be misquoted.