'ghost' signal

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Trenchie
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'ghost' signal

Post by Trenchie » Sat Jun 06, 2015 10:36 pm

Had a really odd thing happen today ... my 705 picked up a nice clear deep signal (target ID 38/40, depth 10"+). After making sure I was directly above the target I started digging, and digging, and digging... every few inches I checked the hole both in normal mode and pinpointing mode which still indicated I was bang on target. But very oddly the garrett pro pointer wasn't giving any kind of signal. Thinking the target was further down below and just out of the pro pointer's range I kept going down and doing more checks. At 15 inches down (with a hole now about 8 inches across) the signal from the detector was perfectly clear, and still dead centre above the hole, but yet the pro-pointer was still silent everywhere within the hole. Feeling somewhat perplexed, I checked the pointer and then I even replaced the batteries, but yet still nothing from the pointer and yet the 705 was still sounding a good target.

Unfortunately time was pushing on and in the end I had to concede defeat and reluctantly back filled the hole, gutted :E

It was all quite bizarre, I'm certain there was something down there, but yet I trust the pro pointer also but yet it was telling me there was nothing.

I can only summize the signal (possibly large) was just below the range of the pro-pointer at the base of the hole, which was some 3 or 4 inches deeper. This would put the target at at a depth of at least 18inches down. I've not knowingly had a signal that deep before, but if it is the case, then that's impressive in itself.

Anybody had similar things happen or perhaps thoughts on what was going on? help!!
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Re: 'ghost' signal

Post by alfaowner » Sat Jun 06, 2015 10:44 pm

I'd be 99.5 percent certain that it's deep iron ::g

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Re: 'ghost' signal

Post by syzygy » Sat Jun 06, 2015 10:45 pm

not very sure then?

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Re: 'ghost' signal

Post by Koala » Sat Jun 06, 2015 10:52 pm

You can pick up a large diameter cast iron pipe at a meter or so. Tin can can be two spades deep. If I was a betting man I would go for plough shear or horseshoe.

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Re: 'ghost' signal

Post by Spiker1968 » Sat Jun 06, 2015 11:11 pm

I have had a similar thing with my Gold Bug DP, it's as if the detector is getting a signal from the hole, starts with a faint signal and gets stronger the bigger the hole gets. Only happens on pasture land, never on ploughed. Another strange thing I have found with my Nokta fors Gold is that my forearm gives a real good signal and i know there is no metal in there. Sorry I havn't really answered your post but other things can give a signal other than metal.

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Re: 'ghost' signal

Post by newseeker » Sun Jun 07, 2015 5:15 am

i would say if your pinpointer was not picking anything up at 18 inches, as a pinpointer would pick up a large object at quite a distance, then your original signal you picked up was buried in the spoil. And your detector was now seeing the hole as a target.
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Re: 'ghost' signal

Post by fred » Sun Jun 07, 2015 6:59 am

2,500 Saxon coins in a lead box? :D :D :D
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Re: 'ghost' signal

Post by northwalesT2 » Sun Jun 07, 2015 3:16 pm

I had this happen to me once...youd dug too deep.
The target would have been in the side somewhere near the first 7 inches. Although pin pointing said i was directly above it in the centre of coil and i dug about 1 1/2 foot down.only to finally realise the find was in the side only a few inches down...so either that or you walked away from a roman hoard .sorry mate lol

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Re: 'ghost' signal

Post by Trenchie » Sun Jun 07, 2015 6:04 pm

newseeker wrote:i would say if your pinpointer was not picking anything up at 18 inches, as a pinpointer would pick up a large object at quite a distance, then your original signal you picked up was buried in the spoil. And your detector was now seeing the hole as a target.
I forgot to mention that I continually checked and double checked the spoil as I went. Not sure how you mean how the detector would pick up the hole as a target? Hmm is there another force at work here that I had no clue about.. x;

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Re: 'ghost' signal

Post by Trenchie » Sun Jun 07, 2015 6:05 pm

northwalesT2 wrote:I had this happen to me once...youd dug too deep.
...so either that or you walked away from a roman hoard .sorry mate lol
admittedly, the thought has been haunting me!

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Re: 'ghost' signal

Post by Trenchie » Sun Jun 07, 2015 6:06 pm

Spiker1968 wrote:I have had a similar thing with my Gold Bug DP, it's as if the detector is getting a signal from the hole, starts with a faint signal and gets stronger the bigger the hole gets. Only happens on pasture land, never on ploughed. Another strange thing I have found with my Nokta fors Gold is that my forearm gives a real good signal and i know there is no metal in there. Sorry I havn't really answered your post but other things can give a signal other than metal.
I was actually on ploughed, but the signal did come through clearer after I had opened up the hole.

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Re: 'ghost' signal

Post by Trenchie » Sun Jun 07, 2015 6:09 pm

Koala wrote:You can pick up a large diameter cast iron pipe at a meter or so. Tin can can be two spades deep. If I was a betting man I would go for plough shear or horseshoe.
I'm leaning to something like this. It would make me feel (along with the cold beer I'm sipping) much better about yesterday.. lol

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Re: 'ghost' signal

Post by newseeker » Sun Jun 07, 2015 11:54 pm

Trenchie wrote:
newseeker wrote:i would say if your pinpointer was not picking anything up at 18 inches, as a pinpointer would pick up a large object at quite a distance, then your original signal you picked up was buried in the spoil. And your detector was now seeing the hole as a target.
I forgot to mention that I continually checked and double checked the spoil as I went. Not sure how you mean how the detector would pick up the hole as a target? Hmm is there another force at work here that I had no clue about.. x;
its something to do with the the large disturbance in the soil matrix that can cause it to pick a large open hole sometimes, i think there was some explanation in norfolk wolfs advance detecting book, if i remember. I gave the book to someone a while ago so i cant confirm it, ive also read about it on the net. Like someone mention it could of been a surface target near the hole throwing you off its difficult to say ive had this before also.
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Re: 'ghost' signal

Post by killer140269 » Mon Jun 08, 2015 12:20 am

I've had same with deep iron with the x terra 70

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Re: 'ghost' signal

Post by sweepstick47 » Mon Jun 08, 2015 12:53 am

newseeker wrote:
Trenchie wrote:
newseeker wrote:i would say if your pinpointer was not picking anything up at 18 inches, as a pinpointer would pick up a large object at quite a distance, then your original signal you picked up was buried in the spoil. And your detector was now seeing the hole as a target.
I forgot to mention that I continually checked and double checked the spoil as I went. Not sure how you mean how the detector would pick up the hole as a target? Hmm is there another force at work here that I had no clue about.. x;
its something to do with the the large disturbance in the soil matrix that can cause it to pick a large open hole sometimes, i think there was some explanation in norfolk wolfs advance detecting book, if i remember. I gave the book to someone a while ago so i cant confirm it, ive also read about it on the net. Like someone mention it could of been a surface target near the hole throwing you off its difficult to say ive had this before also.
I think the problem of 'no target in the hole' can be explained as occurring in heavily mineralised soil. That in itself producing the initial 'false signal' and the reason for digging for a target. As there is no target found and the hole is deepened/enlarged, this creates a negatively imbalanced field which the search-coil 'sees' and the detector reacts to by producing a 'good' response.
Hope this made sense before you fell asleep!! :D All the best ::g ss47
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Re: 'ghost' signal

Post by newseeker » Mon Jun 08, 2015 1:09 am

That's a good explanation ::g At least it keeps us on our toes :)
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Re: 'ghost' signal

Post by Snuzzz » Mon Jun 08, 2015 9:08 am

Had this a few times. Last time in the middle of an open field at around 2ft I hit a land drain....

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Re: 'ghost' signal

Post by sweepstick47 » Mon Jun 08, 2015 10:22 am

[/quote]
I forgot to mention that I continually checked and double checked the spoil as I went. Not sure how you mean how the detector would pick up the hole as a target? Hmm is there another force at work here that I had no clue about.. x;[/quote]
its something to do with the the large disturbance in the soil matrix that can cause it to pick a large open hole sometimes, i think there was some explanation in norfolk wolfs advance detecting book, if i remember. I gave the book to someone a while ago so i cant confirm it, ive also read about it on the net. Like someone mention it could of been a surface target near the hole throwing you off its difficult to say ive had this before also.[/quote]

I think the problem of 'no target in the hole' can be explained as occurring in heavily mineralised soil. That in itself producing the initial 'false signal' and the reason for digging for a target. As there is no target found and the hole is deepened/enlarged, this creates a negatively imbalanced field which the search-coil 'sees' and the detector reacts to by producing a 'good' response.
Hope this made sense before you fell asleep!! :D All the best ::g ss47[/quote]

Edit: To witness this phenomenon, as a trial, it can be 'forced' when on the beach by checking an area on wet sand to ensure no target is present, then dig out a couple of spades worth of sand and scan the hole......hey presto, a 'false' signal caused by the imbalance created by the 'negative' hole and the surrounding 'positive' wet sand. My comments will hopefully help new-comers to the hobby who experience the problem inland or on the beach, I realise that experienced users will be well aware of this effect. Cheers ::g ss47
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Re: 'ghost' signal

Post by Trenchie » Mon Jun 08, 2015 3:05 pm

Thanks for the replies. I noted the soil was quite mineralised and so what you are saying is quite possible.

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