GPZ 7000 Tip From JP On Ground Noise Problems

[cobill]

When I was out detecting in Rye Patch last month with the GPZ I had a really hard time dealing with the wet/salty/mineralised soil. I just re-read an eye-opening tip from JP on another forum and was wondering if anybody else was keeping their coil off the ground. 

http://golddetecting.4umer.net/t21493-how-to-remove-noise-from-debris-gpz-7000

JP recommends to not scrub the ground and keep the coil 20 to 30 mm off the ground when swinging the coil.

Bill

[Tortuga]

I just figured with the extra power that came from this detector, there'd be extra noise. I don't mind it too much, although I do have to dig a little sometimes in hot ground just to make sure it's not a target.

[Reno Chris]

I was recently out in some of the Northern Nevada salty ground gold areas and tried raising the coil on my GPZ - I wish I could say it was a big success, but it was not. I ran for a bit with the coil as high as150 mm (six inches) off the ground and it was still pretty bad. The detector was groaning continuously, and I was listening for tone changes within the continual groan. I've run the GPZ over salty ground with reduced sensitivity, in difficult ground setting, even in severe ground setting. Severe helped a little but I figure if I have to raise the coil 6 inches, turn the sensitivity way down and run in severe ground setting - and the GPZ is still not in a decent ground balance, well I might as well get my GPX 5000 out of the closet and use it in salt mode, as I'd probably be better off. I've had a couple of exposures with the GPZ and Northern Nevada salty ground in the couple weeks after a rain and all I can say is that salty ground is not the strong point of the GPZ. The next version of the GPZ really needs a salt mode. Damp, salty soils ground balance much differently than moderate to high iron soils that are well drained.

 

With a couple of exceptions, the ground out there In the Northern Nevada gold fields has comparatively little iron, and when dry, they are not difficult to detect. However, we've had a wet time with periods of thundershowers in recent weeks, and it does take several weeks or a month of dry weather to dry out the soil down to a depth where the salt is not a problem. Not all the ground out there is salty, so in times like these when we've had rain, one should focus one's detecting in the better drained areas with less salt. So what did I do? I just put up with all the moaning and groaning and figured I needed to return to the locations with heavy salt in the soils when the ground eventually dries out.

[Steve Herschbach]

That is so weird. I just spent over an hour typing up a post on this subject at http://www.detectorprospector.com/forum/topic/970-minelab-gpz-7000-a-super-vlf-saturable-soil-tips/ and after I post it I come up for air and see this!

I agree the benefit is not as much as I would have hoped Chris. The point is not that raising the coil eliminates the problem and I suppose if everyone has a GPX 5000 sitting around that is an alternative. The point is simply what can you do if faced with the situation to possibly help alleviate it? A dedicated salt mode is the easy preferred solution, but that also comes at a cost as my other post mentions. In my case I prefer some noise to total elimination of the salt signal but I think we can all agree being able to choose what level of salt rejection works best for each of us via a "Salt Reject" control would be preferable.

For now if you have a GPZ 7000 and run into saturable ground or salt ground you can employ these tips as best you can, use a different detector, or just go somewhere else.

Be fun to have you run your salt mode quiet GPX 5000 against my moaning groaning GPZ to see what is better on found targets.

[LuckyLundy]

Today, I was out hunting and dug up a deep 1 grammar and them I was attacked by EMI's. It was just to much for me and I refused to hunt in High Smoothing and called it a day, only one hour into the hunt! High Yield/Normal is the preferred modes, but it doesn't like wet ground...dryer the better! Here's today's color and went home, until the next hunt and hope the ground and air is better!

Rick

[Jonathan Porter]

Salt should not be confused with Saturable ground, they are different but sometimes are together in the one place such as in WA where the ironstone is prolific in the salty areas. Lifting the coil will not assist a real lot with strong salt signals (you can hear the salt signal right up to waist height), so it is much better to just slow the sweep speed down and use a Gold mode that is less impacted by it, going from High Yield to General to Extra Deep or Severe. 

 

Severe was developed for highly saturable ground types not salty ground but it does help a little.

 

Hope this helps,

 

JP

[flakmagnet]

These threads are a real online schoolroom.

 

Very appreciative of the member input and also the willingness to add clarifications

where they are needed. There is so much new information flying around about

the 7000 that it is easy to misread what is being talked about (at least by me),

so the time taken to add clarifications is most appreciated.

[Reno Chris]

Be fun to have you run your salt mode quiet GPX 5000 against my moaning groaning GPZ to see what is better on found targets.

 That's an option that can be made to happen. I was even thinking of trying the SDC 2300 which also does have a salt mode.

 

JP is right that slowing the sweep speed way down does help a lot, and while I did not mention that in my post above, I did do that, I does make a big difference and it is a technique I was using. It doesn't completely solve the problem, but makes a much bigger difference than raising the coil.

 

I guess another option is to wait a month or two and return (at least to noisy patch areas) when the ground is fully dry.

[nvchris]

Ive been having great success in NorNV's alkaline, wet, variable ground by running the threshold silent. (both the Zed and 2300)

 

 

If I were to use my 5000 in theses conditions it would be tracking and enhanced instead of salt mode.

[cobill]

Chris, running the threshold silent is an interesting choice. My main questions about running the GPZ coil an inch above the ground was three-fold:

 

1. I was always taught to scrub the ground with my coil because it increased the detectable depth on targets, and had done that with all my GPXs and never had a problem with ground noise...maybe I was just in low mineralisation, dry soil?

.

2. Does the GPZ coil have to be run an inch off the ground due to it's design and sensitivity? I had not read that until JP's post.

 

3. Has anyone found a solution to reducing the noise while using the GPZ in wet and salty soils

 

Looks like I'm going to have to re-learn everything with this new GPZ 7000 detector!

 

Bill