GMP lack of depth

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LRB1975
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GMP lack of depth

Post by LRB1975 » Wed Sep 03, 2014 8:57 am

Hi,
I have been using my GMP for a little while now, and although I am making finds, I noticed that I don't seem to be finding much at depth. Everything seems to be to maybe 3-4 inches max unless it's big iron x;
I watched XP explained again last night and decided to air test mine and compare to what the Norfolk Wolf was doing. With the same settings as he air tests with, I get nowhere near the depth that he does.
Measuring mine with a ruler, and using a George 3rd penny I only get a very faint signal at 7.5 inches with the coin parallel to the coil and nothing after that. On the video, he seems to be be getting a loud and clear signal at about 12 inches.
I also tried my Henry 3rd cut half laying on the grass and seems to only just pick it up at 4 inches.

What do you more experienced GMP users think of this?
Have I got a problem with my machine or am I doing something worng :-L
Thanks.


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Re: GMP lack of depth

Post by Fusion » Wed Sep 03, 2014 9:44 am

You didn't say which George 3rd penny you were using, but regardless, they are all huge, and any decent machine should airtest one at 12 inches.
:(

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Re: GMP lack of depth

Post by redwulf500 » Wed Sep 03, 2014 10:03 am

hi a while back i buried a victorian halfpenny at a measured 11inches to test a different detector , my gmp with 11 inch coil picks it up with a faint signal with settings iron thresh auto - sense 1 oclock - iron vol 11 oclock silencer 0. so it would pick a georgian coin in air easy..red

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Re: GMP lack of depth

Post by Bazza » Wed Sep 03, 2014 6:14 pm

Funny enough was only talking to a friend at a club meet about the same thing.
Very rarely find anything deep with the GMP , although it is excellent at very small shallow items.
My Garrett AT Pro goes far deeper when run in comparison.

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Re: GMP lack of depth

Post by LRB1975 » Wed Sep 03, 2014 8:37 pm

Thanks for the replies. The coin I tested with was one of many I tried, but I get no signals at all after 8 inches, which is bad really as when you take into account that you are swinging above the ground and with undulations in the soil you are probably losing 2 inches, you aren't going to find anything deeper than 3-4 inches in the ground. Even less if it's sideways on.
What definitely made me think I wasn't getting depth was when I got a good signal and took out a spade full and put it to one side, when I tried to pin point it with the detector in my spade full, I couldn't find it unless I flattened it out X(
Not sure what to think of it apart from I'm feeling like I am missing a lot of targets!
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Re: GMP lack of depth

Post by Tomo » Wed Sep 03, 2014 9:24 pm

The thing is you can't have it always lol. 18 kHz is exactly what it is and as you say, great for smaller precious items like hammy's and alike with lightning fast recovery between iron but won't give you depth unless it's well compact damp pasture etc.
For depth you need a lower kHz machine, 12, 8, 4 etc.
For comparison my mate had an explorer for years and always swore it was the bee's knee's which they are for depth but dire on recovery speed. Quite a few members had goldys and deus's and always picked the hammy's up. He decided to take the plunge with a deus and on his first dig, 3 hammy's on the trot and now he wouldn't swap it for the world lol.
What I'm saying is you pick your machine to what type of hunting you do and what you would like to find.
Goldys at 18khz won't give you any great depth but will suck up hammy's and the like between iron no problem.
Lower kHz machines will go deeper but but might miss the shallower lighter items if you go too fast same as multi frequency machines.
Don't forget if it's fresh plough your testing it on then most machines will struggle to see through the air in the soil.
Sorry for waffling on but in the end you select a machine for your requirements :D
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Re: GMP lack of depth

Post by cheeseaddict » Wed Sep 03, 2014 9:44 pm

I switched to a 13" ultimate coil and found I could increase sensitivity much hotter. The previous poster is correct- the higher frequency does mean it is better at finding " smaller items deeper" that other items may miss. Lower frequency machines may go to a greater depth overall. One major positive for the GMP is the fast recovery speed.

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Re: GMP lack of depth

Post by Tomo » Wed Sep 03, 2014 10:07 pm

Numanoid wrote:But 3-4 inches tomo ?
Come on, a maplins £39.95 machine will go 3 inches,
A £600 machine with fantastic reviews should be going double that even at 18 kHz.
There has to be a problem, either the settings are wrong or the machine/ coil is at fault.
What type of ground are you searching to get 4 inches, stubble, plough etc. Is this on diff permissions too
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Re: GMP lack of depth

Post by Allectus » Wed Sep 03, 2014 10:19 pm

Tomo wrote:The thing is you can't have it always lol. 18 kHz is exactly what it is and as you say, great for smaller precious items like hammy's and alike with lightning fast recovery between iron but won't give you depth unless it's well compact damp pasture etc.
For depth you need a lower kHz machine, 12, 8, 4 etc.
For comparison my mate had an explorer for years and always swore it was the bee's knee's which they are for depth but dire on recovery speed. Quite a few members had goldys and deus's and always picked the hammy's up. He decided to take the plunge with a deus and on his first dig, 3 hammy's on the trot and now he wouldn't swap it for the world lol.
What I'm saying is you pick your machine to what type of hunting you do and what you would like to find.
Goldys at 18khz won't give you any great depth but will suck up hammy's and the like between iron no problem.
Lower kHz machines will go deeper but but might miss the shallower lighter items if you go too fast same as multi frequency machines.
Don't forget if it's fresh plough your testing it on then most machines will struggle to see through the air in the soil.
Sorry for waffling on but in the end you select a machine for your requirements :D
Yep, spot-on T. They are what they are...very good & responsive for shallow hammered etc, but, they don't punch with great depth. I only use mine(rarely now) when I'm trying to find a hotspot in a large field where speed is important. ::g

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Re: GMP lack of depth

Post by Tomo » Wed Sep 03, 2014 10:34 pm

Numanoid wrote:Not me matey, been there done that with the gmp and moved on.
Read the original post ::g
Lol my bad. It's late I-)
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Re: GMP lack of depth

Post by LRB1975 » Thu Sep 04, 2014 5:51 am

Thanks for all the input.

I know the machine is known for it's fast recovery and great for small items , even to the point that I have picked up fragments of lead that when I have had them in my hand with a little soil, I have struggled to find them. But even though, surely you should be getting the same sort of depth from one machine to another on an air test is set the same?

The land I have been on is the same permission, but different fields, but all are harrowed stubble, and only upright stubble on some headlands that are left for tree hedge cutting, but obviously not going to get as much depth on upright stubble anyway. If I hadn't done the air test, I would have said it was cause the top layer of the harrowed stubble was broken up and the conditions as was quite dry, but I have also been out since after some heavy rain and although I got more signals, still nothing deep.
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Re: GMP lack of depth

Post by Tomo » Thu Sep 04, 2014 7:24 am

First I'd check if your machine is V4 and second if N.Wolf is using the 9 inch coil or 11 inch coil as this makes a difference.
If he has the same set up then post his settings and I will test them on mine to check your machine is running fine.
We know an air test isn't a true test of the machines depth but for comparison between 2 identical machines it's ok.
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Re: GMP lack of depth

Post by king of the swingers » Thu Sep 04, 2014 7:44 am

i had same problem but i found i could get 8 to 9 inch if i used 11 coil .

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Re: GMP lack of depth

Post by Tomo » Thu Sep 04, 2014 9:38 am

I think alot 18 kHz machines struggle on stubble especially when your arm aches and you end up sliding it along the top of it lol
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Re: GMP lack of depth

Post by moxi69 » Thu Sep 04, 2014 1:45 pm

Numanoid wrote:I'll guess at, the lads machine needs a re-tune or something.
Years ago I had the goldmaxx1 and the power, can't ever remember only getting that poor a depth.
Can a machine be "retuned "?
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Re: GMP lack of depth

Post by Tomo » Thu Sep 04, 2014 5:02 pm

Ok following on from this I decided to bury yet another coin in the garden while the wife's at work.
Coin is George 3rd penny at a depth of 10 inches.
On the settings I normally run at I run the coil over the target.....nothing, zilch, non comprehende, not a murmur lol.
Ok it's a newly buried coin and not the same.
I then tried the following.
1. Turned the machine on at waist height away from any metal
2. Whacked the sense right up till it chattered and backed it off slowly till it was silent which was around 3 o'clock.
3. Whacked the ground right up until it chattered and then backed it off while tapping the coil on the ground until it went silent.
4. Discrimination at 11 o'clock
5. Silencer on 1

Retried the George buried at 10 inches and hey presto. The signal was quiet signifying good depth but was solid 2 way signal.

Tried a few silvers I buried a year ago and they were loud and clear as they'd had chance to oxidize giving a nice halo.
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Re: GMP lack of depth

Post by Fusion » Thu Sep 04, 2014 5:10 pm

Tomo: Though it probably doesn't make a vast difference, could you tell us whether you used a Second Issue (cartwheel) or 4th Issue penny?
:(

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Re: GMP lack of depth

Post by Tomo » Thu Sep 04, 2014 5:13 pm

Fusion wrote:Tomo: Though it probably doesn't make a vast difference, could you tell us whether you used a Second Issue (cartwheel) or 4th Issue penny?
The smaller George 3rd penny. Didn't want to use a cartwheel cos was too big


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Re: GMP lack of depth

Post by Fusion » Thu Sep 04, 2014 5:23 pm

Thanks. Every bit of ground is different, but even a 4th issue penny at 10 inches should be a viable target for a good machine. The original poster definitely has some machine problem. The fact it can only find a cut half at 4 inches in air is also way below par, I think 6 inches buried should be easy to find.
:(

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Re: GMP lack of depth

Post by LRB1975 » Fri Sep 05, 2014 8:34 pm

Many thanks for all the comments and help. If my machine has a problem, what can you do? Should really be ok, only purchased in late March this year so should be V4 and really only been out 'in the field' 6 times. I plan to try some more tests tomorrow to see what happens. x;
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Re: GMP lack of depth

Post by Tomo » Fri Sep 05, 2014 8:51 pm

It'll be fine. Air tests are never any good lol
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Re: GMP lack of depth

Post by Fusion » Fri Sep 05, 2014 9:23 pm

We're confusing the heck out of the original poster. Myself and others think his machine is totally duff, and needs going back while it's covered by warranties etc. And Tomo et al are saying it's just fine.
:(

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Re: GMP lack of depth

Post by PONK » Sun Oct 05, 2014 9:32 pm

just recently got the power, took to it like a duck to water. ::g
I have been digging deep , had a broken half a hammy liz 6d at 10"-12"
lead the size of old penny at about the same highish tones.
seems to depend what soil your on , heavy iron contamination, find mainly shallow finds.
ed1 pennies etc. ::g
nel hunter coil works well, ::g
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Re: GMP lack of depth

Post by LRB1975 » Mon Oct 06, 2014 8:47 pm

Hi Ponk,
Were you using the Nel Hunter coil when you found the half hammered coin? My GMP won't even register my Henry 3rd cut half at 5 inches, let alone 10 to 12 inches with the XP 9 inch coil. Saying that, my machine will find really small metal objects..I have actually found single lead shot from a shotgun and had it in my hand a barely been able to find it in the soil, but gives a really clear signal.
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