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GPX and EMI


smassey

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Hello all
I have been using my gpx 5000 for a while now and am under the impression the auto tune was to handle emi. After reading some of the posts I am confused. I am reading the 5000 is not good at handling emi. Can anyone explain this to me?
Thank you

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There are lots of different levels of EMI and it can come from different sources. The auto tune can handle low to moderate EMI, but if you are hunting in high EMI conditions like next to power lines or in a suburban area with homes around you, no, the autotune will not handle that. You'll need to put on a DD coil and use cancel mode. Check your operators manual for more info.

http://www.minelab.com/__files/f/22591/Instruction%20Manual%20GPX%204800-5000%20%284901-0096-2%29.pdf

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The GPX 5000 is great at handling EMI. It is not great at eliminating it. There is a difference.

Detectors employ a receiver circuit to discern incredibly weak electromagnetic signals. It is difficult to have a machine that is extremely sensitive and at the same time not pick up interference. It goes with the territory when owning very powerful metal detectors.

The handling part is good. Just push that button and wait a minute while the GPX studies the situation and finds the best setting to run as quiet as possible. In the field that usually is all there is to it.

But if you are in an area with heavy EMI (Electro Magnetic Interference) you may have no settings that are quiet. You can try tweaking the setting manually; that may help a bit. Lower your gain. high gain invites more EMI. Smaller coils almost always have less issues than large coils. Try a smaller coil. DD coils are generally better than mono coils. Try a smaller DD coil. There also is a special anti-interference coil you can buy which is almost guaranteed to solve the problem.

Last resort is use a DD coil and cancel mode. It also will solve the problem but really knocks the sensitivity back. Or break out the VLF.

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No, Lightning EMI cannot fry your detector. If you and your detector are actually struck by the lightening itself, yes, that certainly can fry your detector. The spike you hear moves at the speed of light, the same as the lightening flash (and normally you cannot see the flash during the daytime). The noise of the rumble or boom you hear moves at the speed of sound. When there are only a couple seconds between the EMI spike and sound of the boom, you need to turn off your detector and seek shelter, not because the EMI will fry your detector, but because you don't want to be struck by lightening.

Eliminating the lightening spikes is really difficult and I think you can commonly hear them from strikes 50 miles away.

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No, Lightning EMI cannot fry your detector. If you and your detector are actually struck by the lightening itself, yes, that certainly can fry your detector.

 

Good to know :)  I love this site!

 

strick

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Chris, I had a Garret up in Sierra Valley way back when...detecting in a playground. The thunderstorms were down by Quincy...anyway the detector stopped working and I sent it to garret. They said a capacitor blew and it was likely caused by the Lightning Storm...anyway, I don't detect near lightning storms anymore...

 

fred

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Hi Fred -

Sierra Valley (like Loyalton, Sierraville, Beckworth) and Quincy are at least 20 miles apart, so I have to say I am highly skeptical that a lightening strike at least 20 miles away could break a detector. Who knows for sure, but it sounds more like a capacitor that had problems to begin with to me - and bad capacitors do exist. Some years back Dell installed a bunch of them in their computers, lost a lawsuit because they kept failing and eventually paid out over 300 million dollars (My son used to repair Dell Products and about half the repairs he did were bad capacitors).  If a distant lightening strike can break a detector, the same kind of surge through the circuits when you swing over a very large metal object that overloads the detector could do the same. The other thing is that EMI decreases in power by the cube of the distance. So The EMI of anything (powerlines, etc.) decreases rapidly as you get away from it. Lightening releases huge amounts of energy, but from many miles away, the amount is far less.

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