GPZ And Salt

[Jonathan Porter]

18 hours ago, cobill said:

JP,

I have watched all of your Minelab GPX videos and thoroughly enjoyed them. But, there was not much info on the ground noise discussion we're talking about and there is nothing available on this subject, anywhere on Youtube on the GPZ to aid us in the USA. I wish you could put something together to "train" your friends from across the pond.

My question, related to ground noise issues comes from last weeks GPZ outing at Rye Patch, Nevada where there was significant rains and salty soil. Moisture was at least 2" deep from the surface. I received some "guidance" from so-called experts and ran the following settings:

High Yield/Normal, Sens 18, Vol 9, Threshold 12, Threshold Pitch 60, Vol Limit 12, Auto GB, Smoothing OFF. Using headphones.

I had the Knowledge Base Article with me in the field, but didn't use it. The result was I heard ground noise frequently and slowed down to a crawl. I always GB with the ferrite and only found shallow bits of iron shavings from a dozer and other junk.

What would you recommend?  

Clueless in Colorado,

Bill

Hi Bill, Salt is always going to be a problem, especially if you want to also achieve depth. Deeper targets are slow responses, salt signal kills slow signal responses. My advice on salty areas is to try your most sensitive modes first and go down from there, in this instance it would be High Yield, then General then Xtra Deep Normal before I changed any of my other settings.

Your Threshold is too low, stick to 27 especially if Audio Smoothing is in the Off position, I would also recommend using Semi Auto mode because Salt signal messes with the Ferrite Balance in Auto mode. 

There is a huge difference in Salt signal if you go from Normal to Difficult, this also might have been a good option for you dependant on the ground in your area. A lot of people shy away from Difficult especially in quieter soils because there is a perceived depth reduction, however on Half ounce nuggets Difficult actually gives a better signal response than Normal does in any of the Normal modes (HY, Gen or XtraDeep). 

Minelab introduced the Ground Smoothing mode in the last update, this mode was specifically designed for Salty ground conditions, essentially they are Motion filters so there is a depth reduction when you select either Patch or Salty mode so I tend to avoid them but it does smooth the machine out a lot.

Finally, having a controlled swing speed helps immensely with Salt signals, try not to suddenly vertically lift the coil as this exacerbates the salt signal immensely. To confirm it is salt signal just lift the coil from detect height to abover your head, as the coil transitions from your waist height to shoulder height you should hear a moaning sound, the level of salt signal is determined by how loud this response is. The other way is to place the coil in the air out in front of you with the coil parallel to the ground then rotate the coil from left to right and listen to the audio response, the greater the noise the greater the salt levels. This will help you to decided how aggressive you need to be in reducing sensitivity via the Gold/Ground type Modes or the use of the Ground Smoothing filters.

Hope this helps

JP

 

[Steve Herschbach]

What JP said. I worked a lot of salt ground with my GPZ. My solution most often was to really slow down, extreme coil control. There is a moan that develops as JP has mentioned. I would “swing into the moan” and use the moan as the speed control. In other words as it developed I slowed until the moan stayed low and steady. The moan is not an issue per se I literally kind of rode it and the main thing was just keep the audio steady. A target still lifts above the low level moan. Yeah depth is impacted but I still dug gold. I had no choice as I spent a lot of time out in that Nevada desert and rain seemed to find me somehow anyway. So much for deserts!

GPZ Ground Smoothing Options

GPZ Detecting Difficult Ground

[Steve Herschbach]

I got to where I had this down pat and so when the new Patch and Salt ground smoothing modes came out except for experimenting I normally just powered through using coil control.

Gullies in particular give a direction response but you can run into it anywhere. The coil will groan going one direction and go silent in the other direction. The moan I was not as worried about as it formed a "false threshold" that I managed carefully. The other direction however my interpretation is that the signal is "going negative" and detuning. So if possible try and orient to where the "moan one way, go quiet the other" evens out as much as possible. In gullies this usually means swinging parallel to the gully bottom instead of across the gully or up and down the gully wall.

In places where I was stuck with a groan going one way and silence another, I double swept each time and only paid attention on the "moan swing".

I worked areas this way that I am sure would have sent most GPZ operators packing. I am not saying performance is optimal but I will say a GPZ running at 50% (or whatever) still puts gold in the vial.

I ran into this all the time beach detecting with various detectors. Garrett Infinium for one. Swing the coil from beach to water, and a tone would develop one way and the machine detune/go silent the other way. The easy fix was just flip and hunt away from the water then turn around and hunt back to  the water, instead of hunting parallel to the water. Or just hunt "into the moan". So I have experienced a similar effect with saltwater situation before I ever laid hands on a GPZ such that when I ran into it with GPZ I just reverted to beach hunting habits.

[flakmagnet]

I am going afield here but I noticed with the Eq 800 that going from water to beach and back I would get a fair number of hits in a good area, but to my shock when I ran parallel to the water I got an entirely different set of very good hits as well. Crazy...

 

[Steve Herschbach]

There are so many reasons to hunt a location from at least two completely different angles. I don't think anyone one one pass going in one direction can ever be assured of getting all the targets. DD coils do seem to have a certain direction bias on targets as opposed to concentric coils which do not. Get a beep going left but none going right for instance. The salt thing is something but target orientation and masking are the two larger issues in most places. A coin on edge bangs going into the flat side but invisible cutting along the edge. Infinite variation there. And the countless hot rocks or trash that mask one way but reveal on another.

I think one pass and then another at 90 degrees gets most, but even then not all. There is a diminishing return. But a good nugget patch... I swear you can keep going at it from every angle imaginable and keep finding a bit now and then.

I knew a mad inventor once. He wanted to design a rotating coil array that as it slowly covered the ground generated a rotating magnetic field that essentially mimicked hitting the ground from multiple angles on one pass. The implementation would be a nightmare I think, but it is not a totally crazy idea.

[Norvic]

Going back a bit, the most reaction I`ve seen from salt, or sweeping over variable variable ground in a detector was the Bounty Hunter RB7or the Garret Deepseeker etc, the Z is a stable, easy to use beast compared to those early VLFs. For me those early VLFs were a top introduction to the importance of coil control, then and as Steve points out now. Coil control probably is the most important ability one can use to get the most out of detecting with any detector.

I doubt anyone ever will get that down to pat, every day I don`t get gold I believe it is because I didn`t use that coil/detector properly or I was not focused enough not because I didn`t go over gold.

[flakmagnet]

1 hour ago, Norvic said:

not because I didn`t go over gold.

A very tantalizing thought and I agree...focus is all.

[geof_junk]

5 hours ago, Norvic said:

Going back a bit, the most reaction I`ve seen from salt, or sweeping over variable variable ground in a detector was the Bounty Hunter RB7or the Garret Deepseeker etc, the Z is a stable, easy to use beast compared to those early VLFs. For me those early VLFs were a top introduction to the importance of coil control, then and as Steve points out now. Coil control probably is the most important ability one can use to get the most out of detecting with any detector.

I doubt anyone ever will get that down to pat, every day I don`t get gold I believe it is because I didn`t use that coil/detector properly or I was not focused enough not because I didn`t go over gold.

The old Garret Deepseeker I had found many coins in wet/salty ground at the beach. On one holiday in QLD I got over 50 gold rings from shore to waist high in the water. The method that I used was ground balancing in TR using the discriminating knob.  That got rid of all the moaning except from the competition.  

[cobill]

What I find interesting in this discussion is that when you change from Auto to Semi-Auto GB, you also should adjust your Threshold Pitch from a preset of 53 to below 40 for larger nuggets. These "nuggets" of information are really missing in the GPZ manual and somebody could write a book, like others have done for ML detectors. 

Jonathan Porter really knows the ZED inside & out!

Bill

JP said:

"The information following is my opinion only and is based around what you have ‘actually written’ assuming I have understood it correctly.

Semi Auto locks the Ferrite balance therefore there is no learning in Semi Auto Mode, Auto Mode learns but is a lot different to the original Auto GB mode in the first release software.  In essence in your case you are actually only ever using whatever you locked in originally relative to the temperature so there will be a lot of times where the Ferrite balance is wrong, an easy way to confirm this is to wave the coil over the Ferrite, if there is a BIG signal then your Ferrite balance is way out. IF there is a big signal that means the detector is going to make a noise on any Ferrite-like material in the ground which then means you are going to have unnecessary noise which will then compete with target signals especially deep edge of detection target signals.

You have mentioned ground noise, with Volume as high as you have gone the ground noise response will be extremely variable because you have taken a smooth information packed surface (your Audio Smoothing OFF threshold) and magnified it immensely, this means all the little variations are now very loud which then drown out any edge of detection targets. I note you have lowered your threshold from 27, this is a sure sign of what I am describing. The same could be said for lifting the sensitivity especially in combination with a high Volume setting, however increasing sensitivity can improve signal responses a lot, especially the smaller deep targets.

Deep big target signals are very similar to ground noise, they are slow responses that require careful coil control to be heard effectively. Increasing the Volume too much on any Minelab since the GPX series (Target Volume) will also lift all the surface signal responses potentially drowning out the deeper target signals. This is especially true for Low/High targets which we all crave so much. Using a lower Threshold Pitch really improves the Low/High signals especially below 40. Not having a correct Ferrite balance adds extra uneeded noise to your signal train, if you can remove it why wouldn’t you do so? Any noise that does not need to be there either through poor coil control or bad ground balance or bad Ferrite balance can cost you performance, this is my constant mantra when I am training in GPZ users. I am unsure how you’re actually listening to the detector so some of this information will vary especially with headphones.

Hope this helps and I hope I have not offended."

JP

[flakmagnet]

I agree Cobil, the people who buy a 7000 are generally not novices. It stands to reason that deeper information beyond the set-up manual would be a huge head start to understanding the true measure of this detector. JP's dedication to providing his detailed and hard-won knowledge to a huge segment of the detecting population is well documented - I suppose it is asking too much to hope MineLab would contribute to help fill this information void.