X Coils. What Is X? X Equals Ferrite, Ferrite Equals X

[Jonathan Porter]

A common subject that has come up recently with all the coil discussions is X signal and what it portrays. This thread is to put some clarity on what X means to the GPZ 7000 end user and why you should use your Ferrite.

When the 7000 was released its software was designed to automatically calibrate for a component in the ground called X signal, there is no need for me to go into the scientific aspects of what X is and nor am I qualified to do so however, in the case of the GPZ, it is NECESSARY that the Ferrite be used and operators, no matter what or where the ground is they are working, should make it part of their daily detecting regime even if they can’t discern or understand the need for it.

The GPZ has the ability to ‘balance’ out X signals, to do this you need to activate the Quick-Trak button on the front of the handle. When you press the button you are also activating the regular ground balance that any high end gold specific metal detector uses, initially when the button is triggered tracking is forced or sped up briefly, this also means the GPZ 7000 is doing two things at once when the QT button is triggered. On the first release software the Auto Ground Balance mode was trying to actively cancel out X signals as well as G signals running in parallel with each other, to some extent the G balance will also try to balance out some X signal if the X signal is loud enough but overall the detector requires X balance to cancel out X signals effectively. The issue with the release software was the X balance was too lively and was being too easily dragged away from accuracy by Salt signals and Saturation signals of which WA and Victoria are well know for (most gold fields suffer from these signals).

Minelab then released the Ferrite to help operators to let the detector ‘SEE’  what X signal really was in Salty and Saturable ground, during the release WA and Victoria had suffered a long and extended rain event so the ground was water logged, Salt is conductive so therefore is exacerbated by moisture. Because of the water logged ground during this time it caused lots of early complaints from GPZ users. Not long after this Minelab also developed a software update to slow the Ferrite balance down so it would not be so readily dragged away by those pesky signals, this helped a lot but I was still advocating using the GPZ in Fixed GB mode. At a later stage another software release was provided that allowed the user to use a SEMI AUTO mode where once the Ferrite Balance was completed the X balance would be FIXED whilst allowing the G balance to continue to actively track the regular ground balance, this is my preferred and advised mode.

X signal in the ground is not like G signal, it is in varying subtle degrees but is not as VARIABLE as regular ground G signal, the reason a GPZ makes a signal on X is because since the last calibration the temperature of the electronics has shifted or if in Auto GB mode other signals in the ground have confused or altered the X balance calibration. The only real way to tell if your calibration is OUT or WRONG is to use the Ferrite to confirm if this is so, which is why it is so vital you make it part of your daily routine.

NOISE:
Noise is any sort of audio signal that should not be there, noise competes with targets plain and simple. The less noise you have the more obvious targets will sound and the deeper your detector will run or more accurately the deeper you’ll be able to discern a target (assuming you are also using the optimised Ground type and Gold modes for the ground you are searching and the size of nuggets targeted), all targets under the coil are being energised by the Tx evenly at all times relative to coil position, however user choice of settings, calibrations and coil control have a huge impact on the outcome. If the ferrite balance is out then a signal off any X in the ground is going to join the audio and potentially compete with you being able to discern a target signal.

X SIGNALS and X COILS
The GPZ 7000 is a very versatile metal detector, if can be used even if the Ferrite calibration is WAY OFF as is evidenced by users who refuse to update their detectors or who refuse to use the Ferrite (or both), or if users are using X coils that make a signal on the Ferrite regardless of doing a Ferrite balance. I am a purist so will always check my Ferrite balance because even 0.1% less noise in the audio is an advantage in my opinion. 

The X coils do actually balance out the Ferrite over the receive winding part of the coil (not as cleanly as a ML coil but acceptable), but they do manifest a LOUD signal in another location that any savvy X coil user will soon identify unless a mod is done during manufacture (I am unsure of coils made in the last month or so but it is easy to tell). The manufacturer was unwilling to do the mod due to feedback from customers not complaining, the resistance was based around the mod adding a lot of weight to the coil (gets the coils up into Minelab coil weight territory, isn’t that interesting?). I am unsure how he went about removing the Ferrite signal or the mod required to do so and am not at liberty to discuss why a ferrite signal happens in the first place. The reason I was pushing so hard for the mod was to try and get the X coils across the line for PERFORMANCE parity with ML coils in the hopes of accessing the dongle, the X coils showed potential but needed to be refined, in the end the current option was decided upon and I was no longer needed.

As it currently stands any coil that makes a noise on the Ferrite (especially a LOUD noise) will by default make an unacceptable signal off X signal in the ground, operators will not really notice this signal as it will blend in with general ground noise responses, believe me it is there and it is COSTING you depth!!

I do not use the X coils in Clermont because of these main reasons, our ground is saturable and the X coils saturate much more readily than the Minelab coils, most of my coils have the mod so X signal is not such a problem but a couple of them do not so they don’t get used either, with the larger coils I always use GENERAL/DIFFICULT and every X coil I have used makes touch and knock noises, some are acceptable (The Spiral wound ones seem best) but in most cases General/Difficult is out thereby negating the advantage of using a larger coil for larger deeper nuggets. 

To fully appreciate the differences in the coils I am going to include the settings I use so GPZ operators can benchmark what I am experiencing with their own settings.

SETTINGS
Audio Smoothing: OFF
Ground Smoothing: OFF
Sensitivity: 9
Threshold: 27
Gold Type: HIGH YIELD (To experience Knock and rub noise use GENERAL/DIFFICULT)
Ground Type: DIFFICULT
Volume: 6 to 8 for Headphones (either through a B&Z booster or GPZ direct), 12 for WM12
Ground Balance: SEMI-AUTO

Conclusions and Suggestions:
At no stage have I said the X coils are unusable just user beware. In quiet ground they should be OK and in variable ground, like I operate in here, they are usable but twitchy. I have found gold with them but choose not to use them full time in my areas due to the above issues and my being fussy about noise. I did during supervised testing (under duress I might add for the very reasons that have been borne out online) find gold in ground I frequent, I expressed that I was impressed that I was able to find gold with them in such a flogged area and that they showed potential which was borne out by my continued involvement till I was no longer needed.  I have since been back to that area with customers on training and as always have found gold over the same ground as is typical of Clermont thanks to its high variablity ground.

My favourite X coils are the flat wound ones because they seem to handle our ground better and have less touch sensitivity, however they are a LOT heavier. In essence they are what they are and did not meet required standards to be officially recognised, which is a shame because I too desperately want to see more coil options for the GPZ.

JP

X Coil 2021 News

[Andyy]

Excellent review and much appreciated.  I will keep this in mind when reviewing the 10 inch X coil.

 

[afreakofnature]

Out of curiosity, are the Xcoils SuperD coils?  If not, wouldn’t that be part of the ZVT technology?  And if its not necessary to have a SuperD, could you explain the two techs and how they work together or don’t need to work together?  Could SuperD work on nonZVT detectors?  Are you getting where I am coming from?    After chatting with my friend just now they must be SuperD coils in order to work. (edited)

If there are refs for this already, just let me know and I’ll read those instead of having to write a lengthy explanation.  

Thanks JP!

 

[Jonathan Porter]

The X coils are DOD wound (SuperD is the name Minelab give for that configuration), you need that style of coil for ZVT to work properly. The Spiral wound X coils have a flat Tx and a traditional Rx, because of the spiral they seem to behave a bit like a monoloop with a signal kind of coming off the side edges of the coils as well as the traditional receive points where the windings cross each other.

Electronically they are flawed with what Minelab would consider to be too much saturation signal (Tx is most likely too close to the ground relative to the Rx in an attempt to save weight and simplify design and expense), the windings also allow too much knock and rub energy through the windings causing noise especially in General Difficult. Because they are hand made there will also be discrepancies and inconsistencies between coils which I also noticed with my coils. If Minelab made such a coil they would be constantly having to replace them under warranty. I gave all this advice when I was testing them to both the manufacturer and the importer. 

JP

[afreakofnature]

Thanks for answering my question JP!

[sturt]

Hi JP. Been watching a lot your work out in the scrub during the years. Thanks for your time very helpful. I`m over in the WA side and need to put my bit in. Even though new to this forum I have gone through the 4500 to 5000  to 7000 series over the years. I look at the posts from persons telling me how good the new x coils work but to me over here I work over old grounds flogged over the years full of hot rocks and minerals. Most areas have been scraped by blades to flatten the ground and get the coils as close as possible to the ground. I am picking up small nuggets usually within 50mm from the surface. The average size is 0.1 grams. I will include a photo of some pieces collected from the Leonora area four weeks ago. So it may take all day to get a gram but I enjoy the struggle, then every now and then out pops a beauty. I use the ML14" coil with the skid plate bouncing on the ground (carefully).  I have to run in difficult all the time, high yield, sensitivity 20, threshold 1, vol 12 with the VM12 unit, ground balance auto, all smoothing off. The coil works nice and quiet as long as you balance properly at the start and take your time.

I have picked up a lot of small stuff that people and machines have left behind. Any nuggets greater that 1 gram set the machine off so loud that it wakes you up with a fright. In high mineral ground give it a try. 

All in all the ML14" suits me to a tee. Okay a bit heavy, but I swing without needing a harness and the coil takes a lot of punishment from me. Enjoy the bush out there all, cheers Sturt.

 

[Northeast]

Thanks for the post JP. 

Although it seems like some of the early issues may have been ironed out is always nice for a potential consumer to know the teething problems a new product has had and potential issues that may still arise for some purchasers depending on ground conditions or if the patch lead, etc aren't quite up to scratch. 

Although I no longer own the Z, if it were still in my hands I know I couldn't bring myself to 'cut the cord' as it were.  The risk versus the reward would be just too big for me at the present time.  I think you mentioned in one of your earlier posts about the possibility of "coil not connected" being too scary to contemplate - I am definitely in that category  ?

This is also not a slight on the X coils, their manufacturer or Davsgold.  Obviously there are many happy purchasers experiencing little or no issues and finding good quantities of gold in flogged patches.  But there are 2 sides to every coin and it is good for potential purchasers to see the flip side so they can make a fully informed decision.  

Cheers, NE.