EMI and my Equinox 800 - unusual?

[brianc053]

Hi everyone. For the last few weeks it seems like almost every location I detect causes significant EMI with my Equinox 800. I'm trying to decide whether this is normal, bad luck/bad locations, or whether there's something wrong with my detector.

Today I went into my backyard and took the embedded video. It's about 2 minutes long (could have been shorter, sorry), so if you are able I'd appreciate it if you would please take a look and let me know what you think.

If you can't view the video then let me summarize some points for you:

- I have a few hundred hours using my Equinox, so I'm reasonably experienced. The behavior recently seems different than it was earlier in 2020 (but the locations are different so by itself my "feeling" about a difference isn't enough to go on).

- I always do a Noise Cancel after startup, holding the coil in the air as I was taught.

- In the video below my phone is in airplane mode, so it's not my phone causing issues.

- Two things happen in the video below that are confusing me:
1. when I move the detector over my buried household electrical wire (the one running underground from the pole to my meter) the detector goes nuts. Is this to be expected, or surprising by itself? I ask because I have read about users who can detect right next to electric fences or under power lines with no issues. I'm not one of those users; I seem to have issues with any power lines.

2. In the video I cycle through the frequencies, including 4khz (I'm on the latest version of the software. 3.0 I think?). 4khz goes nuts with EMI, but strangely none of the other frequencies go nuts...except for Multi. I thought 4khz was NOT included in Multi-Frequency. If it's not included in Multi, then why does Multi go nuts but 5khz, 10, 15, 20, 40 are all pretty clean?

Something just seems...off here. In the field I've resorted to using single frequencies at many locations over the last month or two in order to eliminate EMI. I'm still able to locate targets in this way, but I know I'm missing out on the benefits of Multi-IQ.

Please share your thoughts, and ultimately if you can tell me whether you think this is normal (and I'm just detecting in bad locations) or whether I have a problem, I'd appreciate it.

Thanks.

- Brian

 

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[DizzyDigger]

I have no idea how well your underground line is shielded, but
in my detecting experience (I don't have an EQ) you're going to
get EMI most anytime you pass the coil over underground power
lines. It will be worse when the ground is wet.

Also, that power line is heavy gauge copper, so the coil (an antenna)
is going to react to it.

As to why it's most prevalent at 4khz I have no idea.

 

[McKinney_5900]

It is a curious question as to why multi, which doesn't use 4 khz, has troubles.

 

[Treasure_Hunter]

It will happen with underground and overhead power wires, overhead especially if they are the high powered over head lines, the ones that carry hundreds of thousands of voltage across the city and state.

 

[cudamark]

Yes, it's common around power lines, wifi, electric fences, etc, and something you're going to have to live with. I'd try different modes and reduce the sensitivity quite a bit to see how much help that might do. I can only conclude that it's the mix or blend of frequencies that are causing it to go crazy in multi and not in the other single frequencies. Make sure when you do the noise cancel, you do it right over the worst area. You can also manually toggle up and down the noise cancel dial to see if one setting is better than another instead of letting the machine do it for you. It doesn't always guess correctly as to which one is best.

 

[Donut]

Do you have one of those smart watches.are you near a car with in built in wifi.
4 khz is closer to 5 khz and the interference is in the lower spectrum and that is why it’s doing it in multi. You showed it didn’t cause interference in higher single frequencies.
i have places that do similar. I just go to single frequency in those areas.
also you may need to lower the sensitivity even down to 10 or down from 20 until it settles down.
make sure your cable connection is snug.
Doug

 

[vferrari]

To directly answer the questions in your video:

What you showed is completely expected when you bring the coil in proximity to a an active power line. And what you observed with individual frequencies is not surprising. There are workarounds that I will discuss below, but basically your options are limited if you want to detect right on top of that buried line. Frankly, based on what you showed in the video, you have several good single frquency options and there may be a Multi Mode that fares better in that situation, but I will get into that later.

To explain why what you saw in multi and single frquency is not unexpected, I have to clear up a huge misconception that is bascially the fault of Minelab's confusing marketing statements. ML's awkward cartoon marketing diagrams were a misguided effort to oversimplify a complex technical concept, and made it appear that Multi was comprised of 5, 10, 15, 20, and 40 and measurements confirmed that this is just not the case. While I cannot confirm how this came to be but I suspect it is what you get when you try to mix the engineers with the marketeers. Marketeers know that people always think more is better so there is a general misconception that a 5 frequncy multifrequency approach is better than a two-frquency when that couldn't be further from the truth. If you transmit five frequencies simultaneously, you have to divide your detector power between those five frequencies which limits the signal strength transmitted into the ground. You can create a spectrum of frequencies by simply combining two or three frequencies together and you limit the power loss in that event. When you delve into specific information provided by the ML engineers and backed up by spectrum analysis measurements of the output of the Equinox in different modes, it becomes apparent that the multifrequency spectrum is NOT comprised of the 5 (now 6) individual frequencies. It is indeed comprised of two different frequencies combined together and processed in different ways for each mode to provide coverage across the spectrum from 5 khz to as high as 100 khz. So the five/six individual frequencies have nothing to do with the Multi IQ spectrum. I can and have dedicated entire threads on this specific topic here and on other forums and don't plan to re-hash that here in further detail, so you are just going to have to take my word for it. This has been verified by several people doing measurements and has been subtly confimed by ML in their tech talk articles.

Therefore, it is indeed possible for 4 khz AND Multi to be affected by the EMI while the other individual frequencies appear relatively unaffected. It is also common that the lower frequencies 4 and/or 5 khz and sometimes even 10 khz tend to be more adversely affected by powerline EMI than the higher frequencies. So what you are observing in your yard with powerline EMI is not unusual.

One thing to remember is that EMI noise cancel really is only applicable on a mode basis and is not universal. By that I mean that you have to noise cancel in each mode you use. If you start out with Park 1 and noise cancel and subsequently switch to Park 2, then you need to also noise cancel Park 2 because it uses a different multifrequency spectrum. Similarly, it is a best practice that you noise cancel for each individual frequency you use if you Noise Canceled in multi first.

This might explain why you are having trouble getting the machine to quiet down after just a single noise cancel (unless you are indeed doing a noise cancel on each mode shift) My suggestion on a structured way to deal with EMI is:

1. Find a quiet site to detect, or failing that, find the quietest part of the site to detect. Avoid power lines, cell towers, wifi and other RF transmitters, cell phone interference, florescent lights, etc You obviously don't have a lot of control over this but do what you can. Sometimes time of day and weather conditions matter. Humidity can affect corona discharge from high power lines and sometimes power usage or radio usage is limited to working hours on weekdays or during certain limited hours. Same with electric fences and invisible dog fences. Sometimes you have no choice because the emitter is on 24/7.

2. If the site is not quiet, noise cancel your preferred mode and then reduce sensitivity as low as practical.

3. If you find you are having to reduce sensitivity too far (i.e., 15 or less) then try a different Multi IQ mode to see if you find a quiet mode. Remember to noise cancel the new mode.

4. If finding a quiet Multi mode that doesn't require you to excessively lower sensitivity is not happening, then experiment with single frequency modes. It really doesn't matter what mode you start from (other than the default disc, tones, and recovery speed settings) because once you go to single frequency, the Multi IQ multifrequency/signal processing "personality" profile becomes non-existant. Also, note that when you are in single frequency, Iron Bias filtering is no longer available and it becomes more important to get an accuate ground balance to avoid ground feedback. Be sure to noise cancel in single frequency.

5. Make sure you are experiencing EMI and not chatter due to ground feedback (typically only heard as ferrous grunts registering -9, -8, -7 TIDs when operating with no disc - i.e., horseshoe mode). Low recovery speed can also result in more ground noise chatter. The chatter in the video was definitely EMI.

Anyway hope this helps you tamp down the noise at your new sites. Worst case, just put it in a quiet single frequency where you can run with a decent sensitivity setting and swing away with confidence.

Good luck and happy hunting.

 

[brianc053]

Thank you everyone for the comments, and for the universal guidance that what I'm seeing is not that unusual. I was genuinely worried that I needed to send my detector (or coil) in for service.
To clarify, I did the test in my backyard for illustrative purposes and because I knew exactly where the power line was, so it was easy to control.
In the "field" (and at various locations recently) I have experienced similar issues and wasn't able to control the situation. In one place (where the gold ring was) there's a dog fence. In another place (Yale lock, cigarette case, standing liberty quarter) I'm less certain as to the source of the EMI, but it appears there are buried electrical lines and there's also a nearby cell tower.

I'm comforted knowing that I'm not alone in having to adjust the detector to the situation. I've gotten comfortable switching to single-frequency mode (though vferrari I didn't know I needed to noise cancel again - thanks) and I'm still finding targets with single-frequency (the liberty seated dime was found this way).
I would have been more worried if you guys all said 'whoa that's weird, my detector purrs like a kitten in that situation'.

Vferrari thanks for your science explanation. I follow it all, as my undergrad is a BS in Physics. Makes total sense to me.

And as we all know because we're looking in the Equinox forum, this is another reason this detector is great. It gives us options that lower-end detectors (ahem ahem...the Vanquish) don't give us.

- Brian

 

[Donut]

Their are a lot of EMI signal out there. Cell towers, microwave transmitters TV. Transmissions. And others.
When I was in the Army during one of my radio classes (communication/ radio repair and crypto. I was given a demonstration on radio signals and I was to say the least amazed.
So from what I’ve seen things can be fine one second and messed up seconds later. In the demonstration a wire was moves 6” three miles away. I was taken to the other location and they showed me what they did. I was amazed.
Doug

 

[Slimpickins]

Try single freq. 15Khz lower sens and ground balance

 

[DizzyDigger]

Their are a lot of EMI signal out there. Cell towers, microwave transmitters, TV Transmissions. And others.
When I was in the Army during one of my radio classes (communication/ radio repair and crypto. I was given a demonstration on radio signals and I was to say the least amazed.
So from what I’ve seen things can be fine one second and messed up seconds later. In the demonstration a wire was moved 6” three miles away. I was taken to the other location and they showed me what they did. I was amazed. Doug

I spent the last 10 years of my working life as a sales rep. in the very small
field of EMI/RFI/EMC (Electromagnetic Compatibility), more specifically we worked
with RF shielding, test and measurement. I sold test chambers, antennas, amplifiers,
etc., all used for measuring EMI/RFI emanating from a device.

You're 100% correct...the amount of ambient RF and microwave noise has
increased exponentially with all the new technologies. There are signals
at frequencies from DC to daylight..everywhere.

It would be interesting to pick a spot in the suburbs of any major city,
set up a signal analyzer with an ultra wideband antenna, and then run
a full spectrum scan from say 1 KHz up to 40 GHz.

Yep, I agree..people would be amazed to know just how much crap
is floating about us 24/7.

 

[CoinFetcher]

The responses are really long, and I don’t want to read them, but I will give you my experience with the machine.

You need to go somewhere with no powerlines, so not a neighborhood, not a city park with a lot of lighting infrastructure, and you need to test your machine there..

Leave your cell phone/recording device in the car, just get the hell away from electromagnetic interference, and only then can you properly test your machine..

If you want to detect in areas with high electromagnetic interference, then you’ll need to adjust your “sensitivity” down to where the noise stops