large coil PI detectors

XLV

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ive seen 40"x40"rug coils used in the gold fields and in the philippines ....my question how large a coil would be needed to avoid all trash ....what i see 40"x40" is worthless in trashy areas ....my guess would be more then 10' x 10 ' ....the depth is not the problem am only interested in the top 2 feet of dirt .....what size coil would avoid all bottle tops and soda cans ..the target would be of gallon size or bigger ...????? any infor would be helpful
 

ARC

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Aug 19, 2014
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JW 8X/ML X2/VP 580
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"my question how large a coil would be needed to avoid all trash"

Two words...

"good luck".

I am not sure that "bigger is better" applies to a coil avoiding trash.

A soda can is gonna ring like a trash can and vise versa when searching for larger items... your not going to be able to discriminate moderate sized trash and a "chest of gold" so to speak.

The only thing I can say is... your gonna have to dig it all... which... on the bright side...

Will...

Turn your little muscles...

Into big muscles. :)
 
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XLV

XLV

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AARC are u sure about that .... what i seen with a 40"x 40 " coil aluminum bottle caps are only seen in the first few inches of soil and a aluminum soda can on the wet salt sand beach 18" .....i never used or seen a 10 foot coil ...but a crushed soda can is what max 2 oz of aluminum there has to be a limit of how deep a larger then 10 foot coil could see it ....am not trying to discriminate ,,,, its like a coin machine finding a 1 gram nugget most machines the signal to weak so u just ignore it ...
 

ARC

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Well I happen to own a large coil... :)

When I say larger lol... 24 x 48.

Fisher Pulse skid... modified of course.

I will hit on foil... soda cans... ANYTHING under it.... cans to even a propane tank at 3 + foot... SO.... I only speak / know... from my own personal experience with THAT coil.

This coil... will also hit a cannon buried 12 foot under sand if set / conditions are right and it were to pass over it.
 
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XLV

XLV

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the target minimum in weight would be 5 kilo to max 100 kilos ... so a bottle cap a few grams like a coin and the size of large coin and a soda can 1/75 the weight or less and 1/10 the size or smaller ...the area of a 10 foot coil is 125 x greater then 12" round coil .... to me maybe am missing something..... but something dosnt add up
 
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XLV

XLV

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AARC thanks for the information i dont know of any one that used bigger then 5 foot square maybe somebody has ....where am at the beach is a trash site so ill try anything
 

ARC

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Well here is some advice...

IF you have a suspect spot... First "clean" area of all small stuff etc with regular detector / coil... removing any interference will increase your odds of "seeing" deeper etc anyway.
 
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XLV

XLV

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AARC thanks for the ideas i was planning on either using the coil behind a 4 wheeler upland or from a flat bottom raft on the beach edge i see your from florida i guess u know the first 2 feet is what counts
 

ARC

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AARC thanks for the ideas i was planning on either using the coil behind a 4 wheeler upland or from a flat bottom raft on the beach edge i see your from florida i guess u know the first 2 feet is what counts

Actually...

I will tell you atruth I realized young about beaches...

They move... like the desert.

Move as in... they are in a state of constant change.

Which... is sort a frustrating and a liberating thing at the same time if you peer into the logic of my statement... heh

So... Example...

Walk out on patch of beach sand... work it hard.. nothing.

Same EXACT patch... 2 weeks later... and its like 4th of July in your ears.

So... with this in mind... you can safely ascertain that it MAY be there... and it MAY NOT... be the day. :)

Follow ?

That's why there is nothing like a good ole storm to "stir" things up and reshape the possibilities. :)
 
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XLV

XLV

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where am in negros i call it sand tide in one place i seen 1/4 mile of beach 6 feet deep going out in the sea removed by the current over a one year time period ......yes the beach moves like the dessert ....thank god one of my sites is in a bay area
 

Mitch Dickson

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Mar 23, 2013
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Well you got me. Looking for a lost car? HEHEHE! If your detector is digital with all sorts of bells and whistles, displays and touch buttons, it's probably mostly useless. This is how we did it back in the day. Get you a 1260X Fisher with dual discriminate. Replace the pots with precision 10 turn pots. Set the primary disc circuit at the edge of iron and steel. Once those are tuned out, hunt till you find a pull tab. Set the second disc just at the edge where it gets poppy but is still in. Hunt till you get a signal, pull the trigger to disc #2 and if the signal goes out you dig it!!! You see it is between iron and aluminum. That way you get all nickels and gold rings. If it's poppy, it's a pull tab. If it's a clear zip, it is a coin! An old man with an old analog 1260X will clean your tot lot pretty quick :) Just about as good at the beach!
 
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XLV

XLV

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Treasure hunter thank u for the ad and the video ....i guess u didn't understand what i was getting at ( thats my fault sorry ) ... i need something that covers lots of ground fast ...in aussieland guys use 40"x40" rug coils dragged behind 4 wheeler ...on the beach edge u can't dig deeper then 2 feet so the depth who cares ...right now am holding the coil 2 feet off the ground looking and still running into soda cans this is killing my back and takes lots of time which i don't have because of the tide ...this unit in the video to me looks like belongs in a hollywood movie and looks like it needs 2 people to operate at a quick pace its probably great in a clean area ..the funny thing i almost drowned due to the amount of garbage in the sea when swimming i was trapped in it..i made the tv news ..... clean white sand beach are for the tourists only not treasure hunting
 

TheGreenBoy

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Well, i am using large 1.2m x 1m square coil on a deep seeking PI on a regular basis, looking for large militaria and underground objects such as bunkers, storage rooms and warehouses. The detector is capable to report large targets down to 4m, but with this settings it will react to small items too. So i usually set it up to ignore anything smaller than 0,5L beer can, it will still report large targets to 2m maximum - or multipe small ones covered with the coil, which should be resolved by different settings an by using smaller coil - i am using 38cm coil for that.
The art of treasure hunting somewhad differs from regular metal detecting....
 
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XLV

XLV

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Greenboy thanks for the info ...i guess if i got a 40x40 which is 4x the size of the coil i have now and did some fine tuning it would be possible ....thanks again
 

TheGreenBoy

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I am using coil made from thicker wire flat computer cable suspended on plastic frame made from 4 cm diameter plastic sewer water pipes. The frame is held approx. 0.5m abowe the ground, suspended on 4 ropes attached on a pipe i am holding across my sholders. The coil is on my right side, manvrable by the help of my knee and the detector in bag om my left. All plastic pipes are assembeled on a spot from 1m and 0.5m long pices. Walking inside the coil with the detector over the neck does not work for me, due to metal parts (batteries) moving and swinging in the coil's field setting off the machine.
 

stevemc

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Feb 12, 2005
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I have a PI coil that is 48” x 48”. It will go very deep on big metal objects. Through the air 35’ on a car. 25’ on a metal garbage can. Air on a beer can 8’. In saltwater about 12’. When I use it in the water I tow it about 12’ plus off the bottom, just to not get beer cans. It will not find tiny coins and pull tabs. If I take the coil and fold it over to be a half sized coil about 36” x 36” it still will go very deep and still will not find tiny things. If I fold it again to a 24” x 25” it will find tiny things, maybe not a gold alloy ring because it is not hot on that, too slow of a pulse. But it will go pretty deep on a big object. Just a 10” Pulse coil will go 5’- 6’ on a big iron object like a 24” iron anchor. I have dug that, and find gold alloy rings. I would assume a 10’ x 10’ coil would still pick up beer cans at any depth. Maybe if you can slow the pulse rate it will eliminate small stuff. I will try that and get back to you. It will still pick up beer cans (my detector) on as slow a pulse as I can go. Maybe not as deep? I will try that out. My big PI has automatic SAT self adjusting threshold, which helps when going over different types of soil, it does not have to be ground balanced. That will also allow you to have metal inside the coils detection range and it will quit sounding off, but it will be slightly less sensitive. It is like ground balancing with a target under the coil. So if you had a PI that has auto SAT, you could have a couple beer cans near the coil making it less sensitive. It would eliminate some tiny trash. Possibly could have enough cans in the zone to eliminate beer cans. I never tried that though as I would be counter productive, but could eliminate beer cans would help you. I will try that. And let you know.
 
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stevemc

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Feb 12, 2005
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I really important thing about a real big PI coil is, that to test it out you need to be far away from any big power lines. The big coil is like a big antenna dish. Can pick up pulses from a long way away. Will make a lot of quaking noises. And lower your detection ranges. Regular house is not bad but any power line is bad, the bigger, the worse it is. A big open beach should be good. Underwater it goes way down too.
 
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XLV

XLV

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I want to thank Greenboy and stevemc for there input ....Greenboy do u remember when u made the coil was the resistance and inductance the same as the stock coil ? if i remember right plus or minus 10% is ok ...i think my unit is 2 ohms 400 uh 15t.... minelab has a calculator for coils ...u also gave me a idea of sliding stand for my 20x20 like a table on a snow board ...ill experiment first maybe i don't need a new coil
 
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XLV

XLV

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stevemc i want to thank u for the in the saltwater info and the timing info it will help on the wet part of the beach i search and it gave me ideas if i search from a boat over the water ...your info is making me think that the 20x20 is big enough with a stand
 

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