Better Understanding GPZ 7000 Zero Voltage Transmission ( ZVT )

[Steve Herschbach]

A new Treasure Talk blog by Jonathan Porter.

"Following on from my last blog about the GPZ 19 coil, here are some further tips to help you get the best from your GPZ 7000, irrespective of which coil you are using.  The GPZ 7000 is not difficult once you come to terms with the way the technology performs over the ground. It is a blend of behaviours which are dictated by ZVT technology, the Super-D coil design and the detector’s ability to tap into the full gamut of target information, thanks to being able to run a very low noise floor without any major trade-offs to audio stability."

Read the rest at http://www.minelab.com/usa/go-minelabbing/treasure-talk/better-understanding-zero-voltage-transmission-zvt

[Reno Chris]

Interesting that rather than maximum gain, JP promotes more a moderate approach to sensitivity, or as he says it: "Conservative Sensitivity and target Volume settings".

[Woody]

In my opinion the target volume setting has a significant effect on the GPZ abilities in saturable ground when used with lower sensitivity settings and threshold.  Just my observations on the ground I swing on.

[DDancer]

I find it kind of funny myself that its taken this long for this kind of info to have come up in topic.  In 2015 I made the same observation with Target Volume and sensitivity.  Combined with Threshold it really kicks target id up a notch especially with depth on small stuff~ .5 grams or less~ however it does lend to higher incidents of the howlies in salt and high iron grounds.  Backing off sensitivity does not overly effect any change in high saturation grounds but Target volume and Threshold do.  Part of the combination I learned only this year by swapping info with another (read on).

I only ever shared the observation with a few others and it generally fell on deaf ears at the caravan parks.  However with novices to the Zed I do share the info as I set them up ~ pitty I never get any feed back there :(  as they are pretty much one time events.  This pretty much why I've never really talked about settings here.  I also figured others knew but kept it under wraps as its hard to demonstrate easily.  Something that comes with experience.

That said I did have one success in passing the information, even got feed back when I met the guy again at the same park, this last season *2016*.  His issue was a bit different though.  Seems he had purchased one of the first batch of Zeds that came out and was impressed with its sensitivity to his pick among other things.  He'd damaged his Zed and sent it back to have it replaced by another unit~ standard operating procedure by ML and one I disagree with~ only to find the new unit did not perform like the original~ could not hear his pick.  Apparently he made some video with his new unit and a friends original unit and sent the complaint in to his dealer along with the replacement unit.  Got another new unit and same results.  Another complaint and another unit and again same result.  When I met him he had his latest unit and while we talked he was about to scrap it as well thats when I shared my settings and information.  Couple of weeks later we met again and he was most pleased.  The new unit now worked like the original and I even learned a bit as we traded observations on combinations of Target Volume, Threshold and Sensitivity. 

As to his original machine I suspect he messed with the settings initially but forgot them and for whatever reason he and his friend did not set their units up exactly when they made the complaint video but that's my thought.

Thanks for reading.

DD

[Norvic]

Like all machines, it is the operator that makes it, early on in my use I used the reset function a bit because I`d get it out of "wack" ie  my fiddling would produce results that lead me to believe the Z had a fault. Returning to the factory default taught me I was the fault, once this is accepted by a operator, the machines potential can be exploited.

The Z has a ability that is still amazing me, and I suspect that will be so for many more years. My message to new chums is leave it in its default if it is not getting you gold, your simply either not putting it over gold or not hearing what it is telling you plus of course not going slow and low. Detecting gold is a mental exercise, if your not feeling positive are frustrated and lost your patience better to sit under a shady tree and drink, but for the new chum it is very hard to get this and even harder to get this message across to them.

Not necessarily to just the new chum either, I`ve learnt a lot from my son who hasn`t got a 1,000th or more of the time I`ve had behind a detector. He kills me consistently.

[Tortuga]

3 hours ago, DDancer said:

I find it kind of funny myself that its taken this long for this kind of info to have come up in topic.  In 2015 I made the same observation with Target Volume and sensitivity.  Combined with Threshold it really kicks target id up a notch especially with depth on small stuff~ .5 grams or less~ however it does lend to higher incidents of the howlies in salt and high iron grounds.  Backing off sensitivity does not overly effect any change in high saturation grounds but Target volume and Threshold do.  Part of the combination I learned only this year by swapping info with another (read on).

I only ever shared the observation with a few others and it generally fell on deaf ears at the caravan parks.  However with novices to the Zed I do share the info as I set them up ~ pitty I never get any feed back there :(  as they are pretty much one time events.  This pretty much why I've never really talked about settings here.  I also figured others knew but kept it under wraps as its hard to demonstrate easily.  Something that comes with experience.

That said I did have one success in passing the information, even got feed back when I met the guy again at the same park, this last season *2016*.  His issue was a bit different though.  Seems he had purchased one of the first batch of Zeds that came out and was impressed with its sensitivity to his pick among other things.  He'd damaged his Zed and sent it back to have it replaced by another unit~ standard operating procedure by ML and one I disagree with~ only to find the new unit did not perform like the original~ could not hear his pick.  Apparently he made some video with his new unit and a friends original unit and sent the complaint in to his dealer along with the replacement unit.  Got another new unit and same results.  Another complaint and another unit and again same result.  When I met him he had his latest unit and while we talked he was about to scrap it as well thats when I shared my settings and information.  Couple of weeks later we met again and he was most pleased.  The new unit now worked like the original and I even learned a bit as we traded observations on combinations of Target Volume, Threshold and Sensitivity. 

As to his original machine I suspect he messed with the settings initially but forgot them and for whatever reason he and his friend did not set their units up exactly when they made the complaint video but that's my thought.

Thanks for reading.

DD

I'd like to hear about what settings you use, if you don't mind sharing. 

[DDancer]

I have to make an amendment to what I've said.  On reviewing my settings notes I have made a small misnomer on what I call Target Volume in the previous post.  To me Target Volume is not one setting, Volume, but 2 settings: Volume and Volume Limit.  My apologies.  To be clear adjustments in Volume Limit have a strong effect on volume of a target.  Limit adjusts the cut off point of all targets much like threshold based on strength of signal; this adjustment also increases ground noise at higher levels.  Small targets light up louder at higher limits in my observation.  Adjustment to Volume goes down a notch for various increases in Volume Limit. Touches to the Threshold occur next.  Sensitivity is then adjusted for stability. For each location I go to my first few small targets are used for tweaking to that locality then I just move along in a stable configuration for the rest of my stay.  In areas with large variations of ground noise, Lake Austin mainland is a good example, I will work out where the big changes are and schedule them like a new area while sticking to the settings for areas I can work.

Tortuga my actual settings generally start out thus:  Volume 10, Volume Limit 16-18, Threshold 10, Sensitivity 17-19.  That usually in High Yield/Difficult *Australia conditions* with low smoothing turned on after I have made a few small tweaks to Volume limit and sensitivity for environmental noise with smoothing off.  I get a stable operation then I find my targets to tweak on.  When I'm in an area I know nothing about and on walk about I set up in General/difficult instead.  To be fair this last year I worked more in General than High Yield.

My sensitivity 16-20, bad ground 8-15
Volume 10-15, bad ground 6-10
Threshold 3-10, bad ground 10-15
Volume limit 15-18, bad ground 6-14

Addressing the topic its my opinion that ZVT as explained detects targets in the transition state between field polarity shifts.  Adjustments that I've put forward in effect are what I feel as best to get the most response from target signals as I am looking for the best window between the field shifts for detector response.  Sensitivity, while important, does not really affect that window of detection.  How loud the window is and its cut offs define the frame of the window and how much the detector can see out the window.  In my opinion because ZVT does not operate on a conventional PI base window of send and listen ( a sensitivity based system) but on a basis of continuous read looking for the best view does get better results with lower sensitivities.

Again thanks for reading.

[Norvic]

12 hours ago, DDancer said:

 

My sensitivity 16-20, bad ground 8-15
Volume 10-15, bad ground 6-10
Threshold 3-10, bad ground 10-15
Volume limit 15-18, bad ground 6-14

 

DDancer,

               Reading through your posting, one thing has stood out your threshold settings are in the range I use,  or close to I vary between about 0-15 (audio smoothing off, varying sensitivity) most are using threshold settings in the 20`s which with audio smoothing off is way too high for me. I cannot understand how one would pick up those slight changes with such a high threshold. Works for me and obviously works for you. My volumes in the same range, is it a variance that our machines have?

[vanursepaul]

Hello mate,i have been using

HY --DIFF--THRESH-31--SENS 15-20--SMOOTH-LOW-OFF--VOL 9--I use JPs dual speakers and booster--

when i canget away with it--- gen--thresh 31---sens-20---smooth-off---vol limt-9

i didnt really understand the vol limit part---but i will tweak a little---

Norvic i have found some squeakers with my threshold at 31 that werent worth the time it took to pinpoint them all over the hole ----they make it through just fine----teeny GB 2 bits----the only good thing i can say about recovering them is that i hope it is good practice to get the bigger ones when they come along

[Jonathan Porter]

Just posted this on an Aussie forum to put my opinions out there and felt it should be put on here too in the hopes some of the info will help forum members here.

Quote

................

Here's some important clues to successful GPZ 19 use, do not use any sort of Audio Smoothing, deep targets do not improve much when increasing sensitivity or Volume so be conservative. If you are running the Volume above 8 it is akin to increasing the Sensitivity by 2 for every point you go up, so adjust your volume via another way if the threshold at 27 is too faint. You need to maintain as much volume variation between threshold and maximum volume to hear the full gamut of audio information from the detector.

The performance gains of the GPZ 19 coil over the GPZ 14, on the smaller gold especially, needs to have ground involved because the ground signal is what masks those targets when using the GPZ 14 coil. Think about it for a second, you're working a spot that has reasonable depth and your digging nice sluggy pieces from less than a gram to over 8 grams down to 14 inches, yet the ground is variable, you can tell its variable because you have enough sense to keep the Audio Smoothing at OFF so you can hear the magnetic behavior of the ground through the threshold. The magnetic behavior of the threshold is heralded by a slight very quiet stutter or rhythmic chirp as you move the coil along, in fact you have become so good at ZVT you can tell when your likely to hit a nugget when this rhythmic chirp is present because its an indicator of likely gold mineralisation, you're also experienced enough to know to keep the coil out of the Saturation zone. You can also tell by this chirp when your X balance (Ferrite Balance) is slightly off because the chirp gets stuttery and sporadic when the X balance is slightly is out. (I find it amazing how these so called expert detector operators have not once made any public comment about any of this :scratch: ).

Now that you've worked out the GPZ 19 coil makes less ground noise and less X signal therefore targets greater than 2 grams will actually be more obvious with the larger coil, you will then start to realise that an air test is just plain silly because like I just said it's the ground signal or lack thereof that is providing the performance gain over the smaller coil. Seems pretty logical doesn't it? OK so now you've worked out why the larger coil is providing a performance gain over the smaller coil, where do you go from here? its pretty simple if you follow some simple steps.

• Run the Audio Smoothing on OFF, otherwise your raising the noise floor of the detector and filtering out unrecoverable target info.
• Be conservative with the Sensitivity control, its a Super D coil not a Mono, treat it as such.
• You absolutely have to have the Ferrite Balance correct, otherwise in high X ground the X signal will compete with deep faint target signals (once again something I've not once heard or read of any of the experts commenting about).
• Good coil control, this means keeping the two Rx's at equal height from the ground and the correct range of coil motion in relation to the depth of the target.
• Volume needs to be carefully adjusted, it increases threshold jitteryness when raised above 8, look into your method of listening to the detector, the WM 12 speaker is rudimentary at best and requires too much Volume inclusion to assist when chasing deep targets (This is why I use a B&Z booster with twin speakers).
• If the ground is WET-through salt signals will be elevated, contrary to popular opinion mineralisation signals are reduced on larger coils but salt signals are increased, if the ground is wet-through salt signals will become an issue even if its not really evident when swinging the coil. To test for salt, lift the coil from the detect position to above your head in one fluid motion, as the coil transverses through its arc from waist height to above your head you will hear a moan signal proportional to the salt levels.

The GPZ 19 coil is not perfect it requires effort, more effort than what the GPZ 7000 requires which attracted plenty of negativity on this forum when first released (I don't see many of the Nay-Sayers coming forward and correcting their remarks BTW), I stand by my comments on ZVT because I've used the tech and its coils successfully. For someone to openly attack me without being prepared to discuss the way they use their detector is a whitewash of this forums so called open attitude towards peoples rights to having an opinion. I understand expectations were high, my providing material for the release was to show what is possible with this coil not to propagandize it for sales, to be accused of that is incredibly insulting especially after the many years I've been involved in this industry and my track record.

Minelab ask me for pictures and feedback as is their right, it is also their right to advertise their products in the way they see fit because they are a business that requires sales to be profitable, however they're not going to jeopardize their good name by making false claims. I seriously doubt they will make much money out of the GPZ 19 coil, it was incredibly hard to develop and very expensive to build, but it's what we all wanted. I suggest people get out there and start using it looking for gold not standing motionless on some piece of ground destroying your confidence and every one else's along the way!

JP