EMI - Detectors and Electro Magnetic Interference

This is getting to be a big problem, one that basically did not exist for me years ago. Cell phones, Bluetooth, wireless this and wireless that, EMI is everywhere and getting worse.

Detectors are radio receivers and so how to pick up that very faint target signal while excluding this blizzard of EMI is a chore for the engineers. Some detectors seem very resistant, others not so much.

I let three detectors I very much liked go away because of EMI issues. The Fisher F75, Garrett Infinium, and White's V3i. The Infinium was less an issue as it is not so much intended for urban use. The F75 I did use a lot out of town, but finally the fact it was useless in town made me let it go. The V3i in particular irritates me as I love the detector and really want to own one and use it, but I just got tired of turning it in, trying all the tuning tricks, then putting it back in the truck. It just is not worth the battle when I can just grab another detector that works just fine where the others will not.

From now on the ability to ignore or easily tune out EMI is tops on my list of requirements. I do not care how great a detector is in theory - if it will not operate in my own front yard then the heck with it. The only detectors that I give a pass are those made and marketed solely for prospecting as extreme sensitivity and remote areas define that category. But even the prospectors know about EMI and the days when you may as well turn the detector off.

All machines have EMI issues in certain times and places. But what detectors were so bad you just gave up and got rid of a detector you would otherwise have kept? If you had a detector you liked, but let go solely because of EMI issues, please take this opportunity to let people know. My goal here is not to bash or otherwise beat up on any detector or brand. But this is a serious issue and time we start making notes on it. Telling people they are not tuning their detectors right is not the answer either. I do not have to tune my cell phone properly to eliminate EMI and I am not going to fight detectors any more on this issue. They need to be designed with easy means for dealing with EMI or go back to the drawing board. At the very least, offer an anti-interference coil for models prone to EMI issues.

Steve Herschbach
DetectorProspector.com

Yes siree Steve, you got that right...........
Had a number of current machines over the past few years that everyone raves about. For me they were not that great, EMI killed them, could never run past 50-60%. And even then the noise at times drove me nuts. Why would I use a top end machine when a Tesoro not bothered by the EMI would get the same depth and make for more peaceful hunting. I gave up and quit those newer machines, sold them off. The last VLF machine I kept and used that worked excellent without EMI issues was the Discovery Baron. Almost kept that one but, after using my PI more and more felt comfy enough to sell it. My PI handles EMI extremely well and its very peaceful to use. So that's all I am hunting with now, love my latest build. Wouldn't mind letting you try one after I build a few more over the next few months.

So maybe when the manufacturers get the EMI issues figured out, I'll buy a new VLF detector again.

DeepTech Vista X with 3 search coils.
Works for me

I feel your pain, I live within 5 miles of a busy Air Force base and the USAF can make any detector I use have a melt down. At first I blamed the Mfg's for poor quality, then realized it was not the detector but the Air Force that was effecting my detecting, they have a couple of planes the drive my detectors nuts, kinda wonder what these invisible waves are doing to my mind and body. Hey instead of blaming Abby our dog, I will blame Uncle Sam.

Tom B Wrote:
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> I feel your pain, I live within 5 miles of a busy
> Air Force base and the USAF can make any detector
> I use have a melt down. At first I blamed the
> Mfg's for poor quality, then realized it was not
> the detector but the Air Force that was effecting
> my detecting, they have a couple of planes the
> drive my detectors nuts, kinda wonder what these
> invisible waves are doing to my mind and body.
> Hey instead of blaming Abby our dog, I will blame
> Uncle Sam.


Ever wonder why so many people have headaches, or hear voices in their head? I'm tired of 1000 channels of movies beaming thru my head along with constant chatter beaming out of everyone when they on their cell phones. ...............
There's no escaping it....LOL
The world was once a quiet place...........

DeepTech Vista X with 3 search coils.
Works for me

Which in your opinion is worse...EMI that you can hear on your machine...that causes it to go crazy and chatter, etc. Or EMI that you can't hear...that you assume your machine is running quiet as a mouse...but is still being hindered a lot by the EMI...particularly in depth capability?

I say that because even pulse machines are bad about EMI. If you've ever ran a Minelab GPX they are probably one of the worse at it, because they are so sensitive. I swear an air plane can fly over so high that you can barely see it, and the GPX will get warbly. Mine would even pick up the electricity in the atmosphere before and after a thunderstorm. Try taking a Whites TDI or Infinium around a GPX too...seems the GPX ain't as bothered by the other two, as they are by it. At the big hunts in Virginia, often times people would see you in an area digging relics, and they would try to swoop in on you and root you out of your little hot spot. If they got too close, I would hit that frequency scanner button on the GPX and it would put their machines into chatter overdrive from hades. It was quite comical to see the look on their face but they always got the point and would change directions faster than when they came in.

That's why I have never owned an f-75..I was turned off by the reviews common theme...bad emi.
But even my gb pro, which is stated too handle emi well, is often affected. I run in all metal when prospecting, and always figure out real quick that my phone is on.

With the advent of tight-footprint elliptical DD coils...... requiring a high order-of-magnitude engineered gain settings to achieve acceptable depths...... comes EMI issues.

Good informative posts and really like the part of EMI that you can't hear that makes you miss that gold coin or diamond ring. Guess if hobby was too easy no one would do it...As far as F70-F75-T2 etc. didn't last long with me as the EMI drove me bonkers..Now the F5 even though less expensive does not seem to have these issues and one of the best ID units I ever used so go figger...

Dan-Pa. Wrote:
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> Good informative posts and really like the part of
> EMI that you can't hear that makes you miss that
> gold coin or diamond ring. Guess if hobby was too
> easy no one would do it...As far as F70-F75-T2
> etc. didn't last long with me as the EMI drove me
> bonkers..Now the F5 even though less expensive
> does not seem to have these issues and one of the
> best ID units I ever used so go figger...


Dan-----If I remember right you have owned/used both the Omega & F5.------Which one of those two detectors handled the EMI problem the best?

Everyone just loves a Deus,... when I encountered it's silent and depth deminishing EMI handling design.
It went up for sale!!

It's like driving a car within city speed limits with a broken speedometer. You haven't got the foggiest idea.

So I didn't buy the next best thing, I bought an F75, it doesn't handle EMI silently.
These days I know when I'm getting depth and when not.
I don't mind running it at 30/40/50 sens, it has awesome depth for coins even at these settings.

i.e. fixed the speedometer problem LOL

HH
Johnb

Hi,,A few years ago I built a device to capture only a very small amount of the electromagnetic radiation we are all plagued with....Ironically it was enough to light a small light bulb and any approaching storm with lighting many miles away would make the light get brighter with each lightning strike....Most of the EMI issues I have encountered seem to follow the power lines...With the advent of cell phones and the wireless Internet EMI is only going to get worse...The new high-power 4G base stations use stronger signals to function better.....They are not in the same frequency range as detectors but intermediate frequencies etc. do come in to play and cause EMI issues.....Under the current detector platform I do not see EMI going away anytime soon.....Basically were stuck and out of luck kinda like a duck stuck in the muck.....JJ

I do not accept that I must choose between a noisy detector affected by EMI and a silent detector with depth affected by EMI. Proper frequencies and shielding should minimize both problems.

Hi,, hey Steve I believe most of the EMI is introduced via the detector coil (antenna) which in most cases is already coated with shield paint etc....I can't even listen to my AM radio here because of EMI issues...It's not legal according to the FCC rules & regulations but they won't do anything about it....Go figure can you say $$$$.....JJ

Where'd Dan go? ha ha-----Question for anybody------Does an RFI choke filter (on cable) help any at all?

Hi, If you are referring to a snap-together ferrite choke core similar to what Radio Shack sells the answer is no no & no...These are only good for common mode interference like you might encounter in computer circuits etc...I even tried different permeability cores with only limited or negative results...JJ

Hi Jimmy----Yeah, that's the one I was asking about/referring to.---Guess I can save my money on that one then.------Thanks

Hi,,, hey D&P-OR, I can only speak from my own experiences with the choke and my negative results....I have read where some people said it worked for them....I know me and EMI don't like playing in the same sandbox together....Sunspots cause EMI too, overall it's seems to be a party out there with electromagnetic interference....I got one spot that can only be worked on Sundays because of EMI....I'm thinking it's something to do with a store and what ever they are running there????....JJ

Let us not forget the smaller coil......


[www.dankowskidetectors.com]

((( Thank you Tri )))

I think Minelab has put some thought into shielding. I have a Sovereign GT that I absolutely love for wet sand hunting. I recently picked up a Sovereign XS-2A box to back up the GT. After all the beach is a two hour drive for me. If my GT quits I can just switch out the box. So I got the box and switched it out on my GT set up to try it. The EMI from my house was severe compared to the GT. This was outside my house in the driveway. I had to drop the sensitivity to auto to even test it. So from my little observation the manufacturers have taken steps.



Edited 1 time(s). Last edit at 09/17/2013 10:56PM by goodmore.

Unfortunately the power lines and many products that use power create spurious emissions some of which are the same frequency as our detectors. Even with a good band pass filter you are still letting anything in thats on the same frequency as your detectors receiver circuit. There is absolutely nothing you can do to stop it other than turning down your gain. If the power company could just put filters on the lines we'd be much better off. Steve, I worked at Elmendorf for 7 years tracking and mitigating EMI for the elephant cage antenna. The power company was always the biggest offender. The only way to stop the noise was to show them where the problen was and make them fix it.

Been down the exact same road as you, with the F75. Good machine, but, too jumpy & skitterish for my tastes. EMI was a terror in my urban spots, too. Why pay for all that power when I can't go past 30% of its full sensitivity?! Only ONE brand has it ALL in my dirt...Minelab. Followed closely by the older CZ's. Every other model I've used suffered from one or all of the following; lack of depth, erratic VDI, incorrect VDI readings at depth, EMI susceptibility, etc. And believe me...

I'd love to swing something lighter & cheaper, but, for coin hunting (which is my forte), nothing beats a ML in my neck of the woods.

Joe

yukonbuck Wrote:
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>There is
> absolutely nothing you can do to stop it other
> than turning down your gain.

Or just do what I did - sell the offending detectors. My Fisher F75 SE was terrible with EMI. My Fisher Gold Bug Pro is extremely EMI resistant. Many detectors handle EMI pretty well so it obviously can be done.

I have a beach with bad EMI when the wind really blows. It affects about any detector ive tried to use during high winds. Some of the issues may well be quality control as well. We buy these new detector and have no idea initially if the way its functioning is correct. Sometimes you just have to know someone close whose been using one with a little experience. It might just be a bad machine. Seems like there are a lot of those now days right out of the box.

Dew

Yes, EMI can be pretty bad w the F-75 in the city, though the first one I had was just plain horrible. The second one I purchased was from Tom and works worlds better. There are little things to know regarding the setting that can help.

Even though I may still have EMI issues with it, I'll never get rid of it as that one machine has made some of my best finds. And that tiny 5" coil with BP horsepower will still trump my DEUS in the heavy iron.

Dew, believe it or not when the wind blows sand across the surface of metal it causes emi. I suppose it could cause emi by blowing across itself too. It usually comes in the form of static discharge after the blowing sand builds enough energy up then discharges from one medium to another.especially if there's a lot of metal around.I have seen this before when hinting emi.

Of all the machines I've used in the last 15 years, the gold bug pro and etrac were the best at handling EMI, but the gold bug pro was the winner.

It seems that higher freq machines are better. Must be some strong harmonic from 60Hz power that resonates on the lower freq machines???