Missing Gold In " Difficult Ground Type" GPZ

[hawkeye]

Interesting thread over on Rob's forum:

http://forums.nuggethunting.com/index.php?/topic/11962-what-are-you-missing-gpz/

These settings have been discussed extensively, but I have never seen a post indicating significant amounts being missed by running in "Difficult".  Seems strange to think you could miss targets by trying to run quiet so you could better hear whispers.  Still baffled by GPZ.

[Steve Herschbach]

 

More aggressive ground balancing shuts up ground noise and also shuts up gold nuggets that share the same target response as that ground. Running in Difficult will without a doubt miss gold that might be detected in Normal. Running a detector noisy while in Normal can also cause gold to be missed due to noise fatigue. The art of metal detecting comes into deciding which to use and when. There is no exact answer because it depends both on the ground and the operator. All I can say is that whenever you can run the least aggressive ground settings or timings that one can apply comfortably.

If you can make the detector run quieter but not completely tune out the gold that is great. What is being pointed out here is a more aggressive ground setting will simply tune out some gold completely. My favorite example is the GPX 5000 Fine Gold setting. It does indeed shut up some of the very worst hot rocks, and this along with the Fine Gold name caused a lot of people to just leave their detectors in Fine Gold. The machine runs quiet, gold gets found, great!

But Fine Gold is not a good name as the setting has nothing to do with Fine Gold. What it should be called is Highly Aggressive Ground Timing. Gold easily detected by the GPX Normal setting will fall into a hole created by the GPX Fine Gold timing and be missed entirely. Yet running Fine Gold in hot rock infested ground can deliver nuggets missed due to all the false signals from rocks. Like nearly all things metal detecting, a trade off.

Salt settings are the same issue. Alkali ground and wet salt beach sand produce a conductive reading. This reading is exactly the same as the reading from very small or very deep gold. If the machine is constantly signaling from the salt, employing a salt mode will eliminate the salt signal, but also eliminate some gold signals. The ideal machine will allow just enough reduction in salt signal as is needed and still allow as many gold signals as possible, but there is an overlap where you have to choose one or the other. Preset timings are an all or nothing approach where in many cases some degree of finer adjustability would be desirable.

A metal detector gets signals on conductive or magnetic targets, so we have ground minerals, salts, non-ferrous metals and ferrous metals plus electrical interference all wanting to make that machine go beep. The responses do not fall into neat categories but have huge ranges of overlap in the real world, far more so than air tests ever reveal due to the ground and adjacent items skewing results. A detector uses filters to deal with unwanted signals but every filter has a cost. Just eliminating electrical interference (EMI) can cause targets to be missed. Ground elimination of any sort eliminates certain signals. The more filters you apply and the more aggressive they are, the more good signals get tossed out also. The challenge for engineers always is finding a new filter or new way to get desirable targets to respond while somehow eliminating undesirable targets. It is a giant overlapping gray zone.

So to repeat -  whenever you can run the least aggressive ground settings or timings that one can apply comfortably. If you get right on a patch, going hot and noisy may turn up gold missed by well behaved quiet settings.

[DDancer]

That article also had some interesting things to say about the use of Extra and normal as well *have to try that*.  Steve reiterates a solid point that seems to get forgotten when it comes to filters of any type. 

There is no one beat all end all so experiment :)

My experience in WA is that difficult is the more normal (pun) way to go however I found that moving from High Yield to General in the difficult mode works best for hunting patches especially at sense settings over 17.  I'm talking outside the USA of course so it may not be a valid point for this forum's US prospectors.  The use of Extra works well after rains down under.  Normal ground type was experimented with down in OZ however there were only very limited areas that it could be used in.  My partner used High Yield more than me and we both scored bits of each others patches the other would miss~ though I generally found the largest deep ones and he the most smalls.  Mind that was mostly work in Difficult~ Normal and Severe did not net  much of anything except some rework.  My thoughts.

[hawkeye]

Thanks for your input Steve.  On paper it all makes sense to me, but when it comes time to make those "trade off" decisions in the field a person (at least I do) starts to do a lot of second guessing.  This is where experience kicks in.  Little experience, more second guessing.  Throw in the sensitivity and audio decisions to be made and you have more stuff to second guess. 

In my situation I am usually detecting in the winter months in areas that have been pretty well pounded over the years.  My expectations of finding multi-gram nuggets are low.  With the SDC 2300 I did find sub-gram nuggets in those areas, not a great deal, but enough to keep me interested.  I had similar expectations when I bought the GPZ 7000, but I expected to find some deeper sub gram nuggets.  This past winter I found nuggets with the Zed, again not in big numbers, but to my surprise not any below approximately 6".  Less than I found with the 2300 the year before.  I have spent a lot of time thinking about why my productivity didn't increase with the 7000.  I wonder if I spent too much time fiddling with the settings while second guessing, something I didn't have to do with the 2300.  In fact, at one time I seriously considered selling the 7000 and sticking with the 2300.  But, I am again all fired up to give it another go this winter.  Go figure?

 

 

 

[Steve Herschbach]

Probably the best thing going about the SDC 2300 outside its gold getting ability is the lack of options as far as coils and settings. No decisions to make, almost impossible to set wrong. No ground and hot rock noise to interpret.  I think it is the best beginners machine going were it not for that high price tag.

The SDC 2300 does use a version of the GPX Fine Gold timings and it therefore is not immune to the above however. Certain nuggets will get missed.

The fun thing about what we miss is that unless our buddy follows us and digs it up in front of us, we never know what we miss. I figure in over 40 years detecting I can now brag about missing more good targets than most people ever find!

[hawkeye]

Another area for improvement for me is target recovery time.  I spent way too much time on average recovering targets.  Big coil harder to pin point, lots of little pieces of wire and old tin cans, etc..  Big holes, moved a lot of dirt before getting the target in the scoop.  Sometimes the big hole wasn't quite on target and 12" hole was next to a target 2" deep.   Also, I dug at least one big a$$ hole per outing that was good sounding ground noise.  Good to have that Hermit Pick with the big scoop.  Damn that fever!

Oh, that feels better to get that off my chest.  Sort of group therapy for detectorists.  Thanks

[Roughwater]

I don't have Z but still a interesting thread.  Basic principles mentioned here seem to carry over into other detectors as well related to ground balance.  Maybe when the 8000z comes out I can find a good used 7000 as reduced prices? Likely by then the coils will also be reduced.  

 Not sure what happened though with Minelabs numbering system.  Seemed like when I bought a GP 3500 the new cost was roughly 3500 American dollars and similar with older and newer models.  But the 7000 started out at 10000 dollars?  I wonder if the original goal was for 7000 but got bumped up as it got into actual production?  Or was it just coincidence some of the other model numbers seemed to correspond with the asking price?

[ozgold]

Hi Hawkeye

Ive just come back from a 3 week detecting trip here in oz and was using normal and difficult ground type setting in very mineralised ground. Lots of hot rocks burnt out tree roots and stumps.

 When I find I signal with normal I would change to difficult to see if I could hear it in that mode.If no signal I would change back to normal and scratch the first 10-20mm of dirt, rocks or sticks from the surface and then try difficult again. If I then herd the faintest of signals I would scratch more material from the hole and check if the signal got louder I would then be pretty sure it wasn't ground noise and then commit to digging the target

this method has been tried many times on signals that are iffy in normal. With sum good results. Most faint signals herd in difficult AFTER 10-20mm was removed resulted in a target be it gold or metal. There was also still sum ground noise and carbon holes dug which gave a good target signal in difficult 

Normal setting is very busy and takes a lot of concentration. I have changed back to difficult to give my ears a rest and keep my sanity on many occasions and havel picked up a few bigger nuggets due to the more precise change in the threshold noise when in difficult 

I change to normal to difficult and severe on every signal,as I'm always experimenting with the machine

cheers ozgold

[normmcq]

 I totally agree with the normal versus difficult settings. I was in Northern Nevada over a year ago  trying to learn what worked best. I was in an area that I knew was productive and was experimenting with different settings. There had been quite a bit of precipitation in Northern Nevada and the alkaline soils were hard to deal with. I switched my Zed to normal and had to lower the sensitivity some to have some stability in the threshold. It wasn't too long before I got an iffy signal, I switched back to difficult and it was gone. Now I was very curious, I started scraping the soil off and switching back and forth between settings and scraping. I was down at least three inches before I could hear the signal in difficult, it ended up being a 2.52 dwt piece down about 15 inches. I'll stay in normal and make other adjustments to be there

[mn90403]

Recently I was hunting with some friends in Southern California.  Two of us had 7000s and one had a 2300.  The two with the 7000s were finding several sub-gram nuggets on ground I was near.  I think some were found on ground after I swung on it.  As a matter of fact I think one was found on ground I had started digging a hole and didn't get the target.

One user is a grinder and the other maintains a bit of space like I do.  The grinder keeps his machine at nearly default but turns smoothing up to high.  The spacer has similar settings.  The 2300 user found more nuggets than me also but not as many as the other 7000s.

They found more nuggets than me in kind of a 4-5/1 ratio and much smaller ones too.  I was switching settings from Steve's to default and a little of Bogenes' as well.  In the end I had the grinder put me on his settings which he NEVER (very slight) changes no matter what the ground it seems.

I could hear some subtle targets in this ground that were less obvious than the .4 and 1 grammer that I found but they would track out.  I was finding trash but my friends were constantly going to each other (I didn't want to see them by this time) and showing the next little nugget they found.  I was falling further and further behind in nugget count and getting more frustrated by signals that disappeared.

They were giving me advice and telling me where to hunt but this was not to be my hunt for the 2-3 days there.  I started doubting myself and the machine.

My question for anyone who has a 7000 is:

'Is there a 'flaw' in any units you have heard of that makes the machine track out targets or is this an operator error only observation?'

Mitchel