I've got a signal but there's no find in the hole!

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sweepstick47
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I've got a signal but there's no find in the hole!

Post by sweepstick47 » Wed Jun 12, 2019 6:42 pm

A familiar claim made by newbie detectorists searching a beach for the first time.


Much has been said concerning what is often described as spurious or false signals. They can arise due to the presence of ‘hot-rocks’ and coke etc. but the anomaly must be very confusing for those new to beach detecting when these spurious signals cannot be attributed to the presence of ‘hot-rocks’. The following is intended to outline one particular cause frequently responsible for creating the following question :-

“ why do I get a signal that when I dig it, the hole is empty but it still gives a positive signal”.

Setting the scene (couldn’t spell scenario). :D

Whilst operating on wet salt sand conditions, a detectorist receives a signal which is then investigated by the usual removal of sand. This fails to reveal a ‘find’ either in the hole or in the removed ‘spoil’ but on swinging the coil over the hole, a signal is produced implying the target lies deeper. More sand is removed and the hole is widened but each time the result is the same, no find appears, and a positive signal is received when checking the hole.

Once this procedure has been repeated several times to locate the ‘deep’ find, the hole getting ever deeper and no find being extracted, it is at this point that the detectorist’s mental state is becoming the source for serious concerns!

It is assumed that the culprit is not due to the presence of a ship’s anchor 8-| or similar located a couple of feet under the chosen digging spot, With that possibility dispensed with, the real cause should become apparent after carrying out the following simple check procedure:

1. Whilst operating on an area of salt wet sand with a stable and correctly ground balanced machine, select a signal free area of about a couple of feet square or so.

2. Remove two or three spade/scoops of sand from the centre (doesn’t matter if it fills with sea water) check the ‘spoil’ for a signal - (there should be no signal received).

3. Without changing detector settings, now sweep the coil over the dug hole and bingo!! ..…..…..…. this time a signal is produced.!

The reason for this is straight forward when it’s considered that by digging a hole and removing sand, the balance of minerals in the sand is changed. This imbalance is registered by the coil /detector circuitry resulting in the detector producing a signal (beep)! It will be known that such signals have become known as ‘spurious’,‘false’ or even a ‘ghost signal’. Regards ss47


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Re: I've got a signal but there's no find in the hole!

Post by mitch » Wed Jun 12, 2019 8:54 pm

Thanks for that SS, but if that is the case why have a reputable company like minelab gone to all that technological trouble to offer two preset beach modes specifically for wet sand when they know this will be forever changing on wet sand. Its a great explanation, but even as a newcomer, I dont buy it and think it really must be down to something else. if like in your scenario, you remove a couple of spadefuls of sand and ‘then’ have a signal when you didnt at surface, whether its mineralisation or not you should have still had a signal at first anyway, the mineralisation is still under the dry sand. This would mean that all the machine is capable of is ground balancing the top couple of inches which is obsurd, especially when beach mode 1 is for both dry ‘and’ wet sand. Does this mean that when diving or snorkelling its not possible to ground balance at all because whatever the ground balance of the seabed is, it will be affected by the surrounding seawater and be essentially useless as a machine. Mostly the problems are of signals dissapearing after digging, not appearing after digging a non signal hole. if your theory was right this would have to have the opposite effect ie: ground balancing the lower half of the hole only before pulling sand out and that doesnt make sense.
Anyway, any info helps us all and its good to take everything into consideration so thanks again and i’ll just keep plugging away and gaining more experience
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Re: I've got a signal but there's no find in the hole!

Post by Me and my boy » Wed Jun 12, 2019 9:05 pm

But most importantly.

1/ check back of spade, I’ve had a hammered coin stuck to mine once and couldn’t find the signal for ages.
2/ as Terry from the detectorists said “always re check you hole ” I found a piece of coke yesterday, through it in the hedge, walked on. Then on the way back past got a signal. It was a clipped cut half on the surface😮
3/ check your muddy boots, I heard of a builder finding a gold coin( think it was Roman) on his boot

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Re: I've got a signal but there's no find in the hole!

Post by Easylife » Thu Jun 13, 2019 12:07 am

A real target normally sounds much sharper than a ghost target. ::g
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Re: I've got a signal but there's no find in the hole!

Post by Saffron » Thu Jun 13, 2019 12:28 am

Good post SS.

But I am sure that on some beaches the problem is very small bits of aluminum, due to being so small the detector claims that they are much deeper than they are, then when you dig out a large spadeful of sand you bury them deeper than they originally were so the detector can not now find them.
But in this case the signal does disappear when you dig the hole.

This is certainly a frequent problem on beaches in the Bristol Channel, due to the debris from when Weston pier burnt down in addition to the normal remains from drinks cans.

Evan

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Re: I've got a signal but there's no find in the hole!

Post by fred » Thu Jun 13, 2019 2:57 am

Not all detectors normally suffer from ghost signals on beaches but plenty do. This has generally been put down to their inability to cope with the excessive mineralisation of the wet and salty environment. However, even normally stable machines can be made to misbehave if you don't set them up correctly.

Once you have a decent beach machine the only real answer is experience. Firstly in setting up the detector properly and then, as Easylife said, in interpreting the signals. :D
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Re: I've got a signal but there's no find in the hole!

Post by hammy20 » Thu Jun 13, 2019 8:35 am

Hi, many times have gone below 18" chasing "ghosts",can't physically get any deeper? Probably on the Lincolnshire beach i go to use it is large lumps of iron from old promenade railing? No hot rock issues.Kirby grips are the main nightmare B|

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Re: I've got a signal but there's no find in the hole!

Post by Magnas » Thu Jun 13, 2019 10:26 am

sweepstick47 wrote:
Wed Jun 12, 2019 6:42 pm
3. Without changing detector settings, now sweep the coil over the dug hole and bingo!! ..…..…..…. this time a signal is produced.!

Regards ss47
I was on Helensburgh foreshore for a few hours yesterday and was experiencing this almost to the point of distraction. Unlike Dumbarton foreshore just a few miles further up the Clyde, Helensburgh seems to have a layer of coke that varies from a couple of inches below the clay to much deeper, while still being detectable.

My machine is a Garrett 400i and though I'd be the first to say it's a very good beginner's machine it does have some obvious limitations. The ground balance is factory set. On wet sand I can tweak the sensitivity and cut the lower iron signals and get by whilst acknowledging that I'm probably missing some targets that more capable machines would find.

Yesterday, the penny eventually dropped and the 400's 'Iron Audio' came to my rescue. By leaving it on I was able to convince myself that those ringing signals at 83/84 weren't worth my time if there was even a hint of iron grunting. No doubt I missed some good things but by using some mental discrimination I was able to have a good time and did manage to persevere long enough find a nice little good luck token. Which reminds me I need some ID help though that's for another thread.

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Re: I've got a signal but there's no find in the hole!

Post by Bors » Thu Jun 13, 2019 10:34 am

hammy20 wrote:
Thu Jun 13, 2019 8:35 am
Hi, many times have gone below 18" chasing "ghosts",can't physically get any deeper? Probably on the Lincolnshire beach i go to use it is large lumps of iron from old promenade railing? No hot rock issues.Kirby grips are the main nightmare B|

JH

CS4Pi.
This is the down side of a Pulse machine as you`ve encountered with those grips as far as digging deep just to find a hair clip.
But ! Pulse machines are NOT affected by " Mineralisation effects" , as there is no discrimination mode on board to be affected. So "Ghosting " in the term used on this thread will not happen .You might be hearing other sounds, but it will not be ghosting .

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Re: I've got a signal but there's no find in the hole!

Post by ROCK HOPPER » Thu Jun 13, 2019 11:15 am

On one of my local beaches using Pi machine at the far end of the beach clumps of clay roll out of the cliff and all of them will give a good signal but when opened there is nothing there.
Using my Detector Pro Wader I will get a good signal but when dug there is no signal in the hole or in the sand pile but if I spread the pile flat I will get the signal back again.

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Re: I've got a signal but there's no find in the hole!

Post by Bors » Thu Jun 13, 2019 11:21 am

u;@ I should imagine that`ll be the very " minute metal particles " in the Clay giving that effect. Without being able to Analyze the Ground,or deposits, in a lab with the suitable machines to do the measureing, were all left wondering in most situations like that.

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Re: I've got a signal but there's no find in the hole!

Post by mitch » Thu Jun 13, 2019 11:35 am

I also think that as a lot of people have this same issue and we are posting the problem scenarios from different beaches, I don't think the issue will ever be resolved because of this. What the issue is on one beach may not be the issue from the other beach. Until every ones machine is taken to the same beach to compare the problem, it will be forever a proverbial pain in the coil. The only simple explanation in my eyes is practise makes perfect.
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Re: I've got a signal but there's no find in the hole!

Post by Bors » Thu Jun 13, 2019 11:49 am

u;@ Very True ::g

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Re: I've got a signal but there's no find in the hole!

Post by sweepstick47 » Thu Jun 13, 2019 12:13 pm

Anyway, any info helps us all and its good to take everything into consideration so thanks again and i’ll just keep plugging away and gaining more experience
[/quote]

Hello mitch ::g Thank you for your reply. There will undoubtedly be many other newcomers to the hobby who are confused by the seemingly complex subject of ground mineralisation and the effects it can have when operating a metal detector (both on beaches and on inland sites).

There are several manufacturers who have introduced settings or operator adjustable controls to their machines in an attempt to counter the adverse effects of iron oxide. They are in effect somewhat of a compromise but subject to the skill and experience of the operator, they can and are currently being used to very good effect. ::g

Thanks again. Regards ss47
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Re: I've got a signal but there's no find in the hole!

Post by Ram76 » Sun Jul 14, 2019 7:41 pm

I was on the beach today, first ever time detectoring , I don't really know what I'm doing yet. I spent around 30min. I was getting signals everywhere though. At first I thought the sand minerals like mica were giving a false reading. I did try and dig a couple but didn't put much effort into it. I'll try again next week.

But as I said I was getting reading all over the place.

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Re: I've got a signal but there's no find in the hole!

Post by Junior » Sun Jul 14, 2019 8:52 pm

Ram76 wrote:
Sun Jul 14, 2019 7:41 pm
I was on the beach today, first ever time detectoring , I don't really know what I'm doing yet. I spent around 30min. I was getting signals everywhere though. At first I thought the sand minerals like mica were giving a false reading. I did try and dig a couple but didn't put much effort into it. I'll try again next week.

But as I said I was getting reading all over the place.
What detector were u using ? Woz it wet sand ?

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Re: I've got a signal but there's no find in the hole!

Post by Ram76 » Mon Jul 15, 2019 11:15 am

Junior wrote:
Sun Jul 14, 2019 8:52 pm
Ram76 wrote:
Sun Jul 14, 2019 7:41 pm
I was on the beach today, first ever time detectoring , I don't really know what I'm doing yet. I spent around 30min. I was getting signals everywhere though. At first I thought the sand minerals like mica were giving a false reading. I did try and dig a couple but didn't put much effort into it. I'll try again next week.

But as I said I was getting reading all over the place.
What detector were u using ? Woz it wet sand ?

C scope cs1m. Sand was fairly wet, not drenched but wet.

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Re: I've got a signal but there's no find in the hole!

Post by fred » Mon Jul 15, 2019 12:16 pm

Ram76 wrote:
Mon Jul 15, 2019 11:15 am
Junior wrote:
Sun Jul 14, 2019 8:52 pm
Ram76 wrote:
Sun Jul 14, 2019 7:41 pm
I was on the beach today, first ever time detectoring , I don't really know what I'm doing yet. I spent around 30min. I was getting signals everywhere though. At first I thought the sand minerals like mica were giving a false reading. I did try and dig a couple but didn't put much effort into it. I'll try again next week.

But as I said I was getting reading all over the place.
What detector were u using ? Woz it wet sand ?

C scope cs1m. Sand was fairly wet, not drenched but wet.

in detecting parlance 'wet sand' refers to the stuff below the tideline. It doesn't have to actually be soaking wet to be highly mineralised due to the salt saturation. ::g
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Re: I've got a signal but there's no find in the hole!

Post by gravelmonkey » Tue Jul 16, 2019 7:13 am

Bors wrote:
Thu Jun 13, 2019 10:34 am
hammy20 wrote:
Thu Jun 13, 2019 8:35 am
Hi, many times have gone below 18" chasing "ghosts",can't physically get any deeper? Probably on the Lincolnshire beach i go to use it is large lumps of iron from old promenade railing? No hot rock issues.Kirby grips are the main nightmare B|

JH

CS4Pi.
This is the down side of a Pulse machine as you`ve encountered with those grips as far as digging deep just to find a hair clip.
But ! Pulse machines are NOT affected by " Mineralisation effects" , as there is no discrimination mode on board to be affected. So "Ghosting " in the term used on this thread will not happen .You might be hearing other sounds, but it will not be ghosting .
Interesting! Took my Vallon Vmh3cs for its maiden outing on a beach yesterday, it has a 'mineralisation' mode. Had trouble with a patch of sand near the low tide zone, around 1.5mx1.5m, which I struggled to auto GB. Produced strong but 'ugly' signal- inconsistent in strength and specific location.

I suppose it could have been multiple, large objects at depth but I suspect that it was related to ground effects- the freshwater stream flowing under the sand or something relating to the geology, the anomaly appeared to line up with a fault or rock layer in the cliffs.

On a related note about ghost signals- thought my second target signal was a ghost after the hole turned up nothing, turned out to be a tiny flake of aluminium stuck to the back of my scoop!
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