Will The Next Gen Detectors Address Emi ???

[Digalicious]

39 minutes ago, F350Platinum said:

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.

 

Doesn't that program notch out everything but very high conductors? If so, that could very well explain why it is much more quiet. More specifically, most of the EMI was notched (filtered) out.

[Digalicious]

47 minutes ago, F350Platinum said:

 

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.

 

 

4 minutes ago, Digalicious said:

Doesn't that program notch out everything but very high conductors? If so, that could very well explain why it is much more quiet. More specifically, most of the EMI was notched (filtered) out.

I just went out in my backyard and confirmed this.

I have 3 high power lines running parallel to the back of my yard. I set up a custom program that notched out everything below silver/copper. In no disc, ground disc, or ferrous disc mode, the detector was noisy with a jumpy ID. I switched to that custom mode which notched out everything below copper/silver, and the EMI noise was gone.

[Erik Oostra]

3 hours ago, dogodog said:

Erik, Thanks!!! I had a feeeeeeling this was the Evil that haunts us all. My soil is bad enough, the extra noise is horrible. And I hunt with average sensitivity. Now go make someone's day!!!!😃

4 hours ago, Erik Oostra said:

I reckon you're spot on Dogodog with the issue being WIFI related.. Both my Nox and D2 go mental on a beach near a backpacker hostel when their WIFI is on.. There's also a powerline with a box nearby which never causes any interference.. 

I must point out that this is the only spot on the island the D2 does this.. I've used it around a huge telecommunications tower which drove the Nox crazy but not the D2.. Maybe the hostel's got an extra large WIFI transmitter to beam down to their private beach? It's weird that it only happens here but I know for sure that when their WIFI is turned off both the Nox and D2 behave themselves..  

[Digalicious]

24 minutes ago, Erik Oostra said:

I must point out that this is the only spot on the island the D2 does this.. I've used it around a huge telecommunications tower which drove the Nox crazy but not the D2.. Maybe the hostel's got an extra large WIFI transmitter to beam down to their private beach? It's weird that it only happens here but I know for sure that when their WIFI is turned off both the Nox and D2 behave themselves..  

Yep. The intensity of the EMI changes from minute to minute, hour to hour, and day to day. That means a valid comparison of noise cancelling abilities would most importantly entail both detectors being compared on the same time and day, and less importantly, both detectors using a similar weighted SMF mode. For the latter, in high EMI, the SMF mode used wouldn't usually matter, because all SMF modes would suck lol...BUT, if you're in an area in which the high EMI is mainly around a particular frequency, then the weighting of the SMF can matter when it comes to EMI mitigation.

But wait, there's more! The recovery speed can also have a huge impact on EMI mitigation. So, the detectors would also have to be using similar recovery speeds.

EDIT:

I worded that last paragraph imprecisely. I should have said that changing the recovery speed can give the illusion of EMI mitigation. Meaning, the recovery speed doesn't legitimately reduce or increase EMI noise.

[midalake]

4 hours ago, Chase Goldman said:

Yes, I would.  Deus 2 seems to deal with it better than any other SMF machine

Yes. In my limited EMI world, the Manticore works as the D2 does.  

As a side note. I hear very few people using Manticore and EMI in the same sentence. 

[UT Dave]

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?

One of the absolute worst parks for EMI is the one closest to my house.  I have to run the Nox at 20Khz and sens 16 to get it to quiet down.  Maybe I'll take them both over there this afternoon and do a side by side to satisfy some of my curiosity.

- Dave

[Digalicious]

45 minutes ago, UT Dave said:

 

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?

One of the absolute worst parks for EMI is the one closest to my house.  I have to run the Nox at 20Khz and sens 16 to get it to quiet down.  Maybe I'll take them both over there this afternoon and do a side by side to satisfy some of my curiosity.

- Dave

You have to reduce the sensitivity to 16 even in 20khz? Wow. That's some serious EMI. In my worst EMI sites, all SMF modes are terrible, 5,10, and 15 are almost as bad, 20 khz does much better, and at 40 khz the EMI is virtually gone. BUT, that is with maximum or close to maximum sensitivity.

Regarding the noise cancel (sometimes called frequency shift).

To the best of my knowledge, all the detector is doing, is sampling the signal at very slightly different frequencies. I'm not talking differences as large as let's say 5 khz, but rather more like differences of 0.1 khz. So if there is 13 channels, the actual difference in khz among those 13 channels is very little. If the frequency shift was significant, then it's no longer noise cancellation. Rather, it's avoiding EMI by using a completely different frequency.

On a high EMI site, flipping through the different channels manually, will in general, show that each channel is noisy. Granted, sometimes a particular channel may seem slightly more quiet, but that's only temporary due to the randomness of EMI in frequencies, harmonics, and intensity. As such, sampling the channels for a longer time, doesn't change that fact, nor should it make the EMI mitigation any better. If the long press does make it better, then I suggest it is done via software "trickery" using one or both of the software trickery methods that I previously mentioned.

Detector manufacturers have been trying to address EMI for many years. I would think that if one of the manufacturers succeeded in a way to legitimately accomplish that, then not only would they profusely advertise the new noise reduction software technology, but also patent the crap out of it. I haven't seen either of those occur. 

It seems to me that with all the random aspects of EMI, claiming to mitigate EMI via software, would be like claiming to be able to count the bubbles in a boiling pot of water. So for all the reasons that I've mentioned here and in my previous posts in this thread, I believe that any metal detector noise reduction that seems to work, is actually an illusion based in software "slight of hand" tactics.

 

[Jeff McClendon]

I don't like how metal detector companies have used the words Noise Cancel for a process that at best is only Noise Reduction. 

I have owned single frequency VLF detectors that operate at 15 kHz or less that were absolutely unusable at some local sites even 10 years ago. These detectors only had very slight frequency shifts which helped very little. Using them now would be a joke. The same goes for all of the pulse induction detectors that I have ever owned. If you think EMI is bad using a VLF at a site, try using a pulse induction detector with a mono coil at that same site. The only recourse is to try an Anti Interference DD coil which will significantly reduce EMI interference but also overall sensitivity too.

I have used all of the Vanquish models, the Equinox models, the Legend and Deus 2 at the same sites I referenced in the previous paragraph. If I insist on running them at maximum sensitivity, I won't be able to distinguish between random EMI audio responses/target IDs and actual target responses no matter how many times I do a noise cancel (reduction). I can switch to 20 or 40 kHz single frequency and crank up the sensitivity some BUT due to ground mineralization, I will lose a ton of depth and target ID accuracy.

So, instead of freaking out or thinking a bunch of negative thoughts, I just lower the sensitivity and stay in the most quiet simultaneous multi frequency mode available that I can find and start detecting.

[Digalicious]

Jeff,

The more posts I read of yours, the more I'm grateful that I don't have to deal with the hot ground that you do. It seems that under your ground conditions, and on the high EMI sites, using a single frequency to stabilize the detector due to EMI, isn't even a viable option. Ouch.

In your EMI sites and SMF mode, by about how much are you having to reduce the sensitivity to stabilize your detectors?

 

[Jeff McClendon]

1 hour ago, Digalicious said:

Jeff,

The more posts I read of yours, the more I'm grateful that I don't have to deal with the hot ground that you do. It seems that under your ground conditions, and on the high EMI sites, using a single frequency to stabilize the detector due to EMI, isn't even a viable option. Ouch.

In your EMI sites and SMF mode, by about how much are you having to reduce the sensitivity to stabilize your detectors?

 

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. All three detector models do not have the same base sensitivity/gain just like they don't have the same sensitivity increment levels. The Equinox models in general are much more sensitive to actual smaller sub gram targets (which includes EMI and ground noise) with the Legend being a little less sensitive to the same targets and Deus 2 even with the 9" coil being significantly less sensitive to the same sub gram targets. So, it doesn't surprise me to hear Deus 2 users reporting less EMI compared to the Equinox and Legend. Whether that is because Deus 2 has better shielding, lower overall gain, a combination of both or some other X factor.......who knows.