Another EMI Nightmare

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Another EMI Nightmare

Post  mulgadansa on Fri Oct 16, 2009 4:09 pm

Gday All
Out last week and came across another hazard for the detectorist.
Apparently on the more established minesites they are going away from flying electromagnetic surveys to search for anomolous areas within their tenements adjacent to their existing mines. They have "loops" of cable on the surface that carry high voltage in the order of 30k-40k and a reciever in a bore underground at varying depths in hundreds of metres. These loops are around half a kilometre to one kilometre on each side so there's a fair bit of ground within the area being surveyed. They pulse the loops and then interogate the data from the receiving sensor. The loops are a single cable about one centimeter in diameter and look pretty innocuous just lying there on the ground.
Well I've got to tell you that if you're within the loop, or for that matter within a couple of k's of it, it's good night for detecting. The 4500 went ballistic. Persevered for about ten minutes and then they must have switched it off, as the detector ran as smooth as silk after that.
I guess a similar sort of thing would happen if they're flying EM surveys.
Like we need more problems detecting???
cheers
Brett
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Re: Another EMI Nightmare

Post  adrian addonas on Fri Oct 16, 2009 5:43 pm

Reckon that method has been around for a while. I guess us little blokes had better get used to the second gold rush already evident on most goldfields. The small but active explorers are as busy as little bees at the moment. Many have attracted capitol from the big players to get out there and find it Every where I go in my part of the world there are drillers geos and tracks everywhere. Last year we were working up a remote gully when the plane with the long tail appeared over head. Back and forth a marvel of endurance flying. Caused a little bit of interference on the 3500s so on one pass I stuck the coil in the air and pointed it at the plane. Love to know what that did to his readings’

love that photo MD All the best AA

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Re: Another EMI Nightmare

Post  gildedprospects on Fri Oct 16, 2009 6:17 pm

adrian addonas wrote:Caused a little bit of interference on the 3500s so on one pass I stuck the coil in the air and pointed it at the plane. Love to know what that did to his readings’

They're probably drilling right where you were standing right now

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Re: Another EMI Nightmare

Post  adrian addonas on Fri Oct 16, 2009 6:26 pm

bloody hope so we got nothing the whole length of the gully.

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Re: Another EMI Nightmare

Post  Guest on Sat Oct 17, 2009 11:26 am

My wife and I watched one of the planes doing a survey over parts of greater Bendigo for several days last year.
Scared sh#t out of cattle, sheep, roos and wildlife.
I was about 200 feet above ground and went back and forth at about 100metre intervals every 7-10 minutes.

Robert

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Re: Another EMI Nightmare

Post  mulgadansa on Sat Oct 17, 2009 2:41 pm

Gday AA
Hey, if you do happen to get back to that spot where you waved the wand at the plane, let us know if they've done anything at that particular spot only. They'd be spewing if they did!!!
cheers
Brett
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EMI IN DA GROUND

Post  Guest on Wed Oct 21, 2009 11:07 am

Next Time Ya Find One of those Illegal HV Loops (Dangerous to people and animals) ya can fix it up with a good set of bolt cutters with insulated handles. HE,HE,HE n Chuckle Chuckle.

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Re: Another EMI Nightmare

Post  mulgadansa on Wed Oct 21, 2009 4:16 pm

What!! And end up looking like GildedProspects avatar???
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EMI

Post  Guest on Wed Oct 21, 2009 5:17 pm

OHhh yehhh maaann, wot a way to go dude, no pain no gain, light my fire, light my fire, yee haaa!!!
Don't need much insulation to keep out 30kv. inch and a half of rubber should do it or ya could take to it with an axe, make sure it got a wooden handle and ya wearin rubber soled boots with no nails n yr Insurance policy is up to date.

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EMI N HV LOOPS

Post  Guest on Fri Oct 23, 2009 10:05 pm

Actually I am not too sure what that big loop could achieve?
Even if it was being used for ground resistivity or conductivity I doubt that any usefull information could be obtained and why use HV when there is natural earth currents flowing through the ground anyway. All you need is low voltage and a means of measuring these natural voltages and currents. Measuring these between several points at varying depths over a grid marked area will give a good indication of the general ground conductivity and provide enough information as to where conductive ore deposits may be.

Maybe these big loops are antenas for communicating with Aliens, they would have as much chance of doing that as finding gold.

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Re: Another EMI Nightmare

Post  echidnadigger on Sat Oct 24, 2009 12:51 am

They don't make anti interference coils for no reason?
Shock horror they actually work around pulse type electrical interference.
And their sensitive but don't tell anyone.
Example: 50 meters from an electrical fence you have no hope with the std DD let alone a large mono. Set up a anti coil and you can get comfortably within 5 feet. There not just built for salt their built for interference.
I know a lady that only uses an anti coil exclusively and she blows me out of the field every time. Go Figure?
A tip for the day: If you have an anti coil on, don't pee on the fence to test if its turned on. LOL
PS. Coiltek seem to have the market on this type of coil in my opinion.
Brett.
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Re: Another EMI Nightmare

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