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Achieving good Ground Balance when using the 'Smooth Class of Timings'

January 14, 2011 03:35pm

Jonathan Porter
Jonathan Porter metal detecting gold

For my fourth blog on Treasure Talk I want to pass on some of my experiences about achieving a good Ground Balance (GB) when using Smooth, Enhance or Fine Gold. As most of you will know by now the 'Smooth Class of timings' were developed for the GPX Series to allow the use of a Monoloop coil in highly mineralised soils. The timings do this by removing a lot of the ground signal, however in doing so they also remove a small amount of the target signal too, dependent on Ground Balance position, target orientation and more particularly size and shape of target.

The reason it’s suggested a Monoloop coil is better for performance is they provide better real time raw feedback of the ground conditions without any physical ground ignoring features (such as the immediate association of a second winding or the constraint of smaller windings, as is the case with a Double-D coil). Therefore Monoloops are dependent on the Timing selected to help deal with mineralisation.

Because the Smooth class of timings remove so much ground signal it can be a little hard to fully appreciate just what is going on once the detector is balanced to the ground (Balancing the detector just means telling the detector electronics what is ground so it can presume that position is the zero point (or null) thereby not making any “noise” on that position). As you can imagine, because the timing removes the bulk of the ground signal the detector has less to work with when actually balancing, a little like when balancing in benign ground (this is why Minelab recommend detecting in Fixed Ground Balance). As such the GB becomes more critical because as mentioned before the timings remove some of the target signal as well, therefore the GB can be easily knocked off position.

Typical smooth class timings ground

Typical ground where you would use one of the smooth class of timings

What I have discovered is this, if the GB is out by even a small percentage point it can be enough to severely impact on a faint good target signal, so it pays to come up with a precise GB regime that helps prevent this. Detectors are not black and white devices; there are myriads of shades of grey where interpretation of the audio comes down to the experience and receptiveness of the listener/operator. Part of that procedure is in understanding the processes, or if you like physical limitations of the electronics you are using. As space is limited here, suffice to say there are a number of important practices required to achieve these aims.

Steps to achieving a good ground balance with the “Smooth Class of Timings”

  • Expose the Monoloop coil equally to the ground when raising and lowering the coil (each part of the underside of the coil should be at equal height from ground at the lowest part of stroke).
  • Only use short steady strokes of less than 50mm after main balance is achieved (after noise is reduced by more than 80%).
  • Once audio goes quiet, release the Quick-Trak Button then depress the Quick-Trak Button again resuming the short strokes at very slow speeds (This can be done a number of times during the process if you like, so long as you allow for the forced GB timeframe of 5 seconds).
  • Continue pumping the coil slowly for at least 5 seconds after there is no audio variation.
  • Hold the coil motionless at bottom of the stroke (as close to the ground as possible without touching it) once GB is achieved, then release the button with the coil still held stationary (important).
  • Make sure you don’t brush or bump the Quick-Trak Button during detecting as even the slightest knock can throw the GB off position, the moment the Quick-Trak Button is triggered the detector goes into a rapid forced GB, even a nanosecond is enough to shift the GB position slightly, thereby taking the edge off a faint deep target.
  • Lastly when a target is heard or a slight variation is heard re-balance nearby, you will be amazed how often a signal will improve after re-balancing even when there is no audio variation as the coil is brought towards the ground.

There is a lot more I can impart on this subject, so I encourage those of you interested to ask more specific questions below.

Jonathan Porter


Hello JP

Thank you for explaining GB in more depth. I've been doing sort of the same thing and have good success eliminating some "noise" here in WA. However, can you elaborate your third point "so long as you allow for the forced GB timeframe of 5 seconds". Is "forced GB" the same as "main balance"?


Posted By: on January 16, 2011 11:43am
Hello Barnie, the Forced GB I was talking about is part of the GPX 5000s programming to help assist in achieving an efficient GB procedure. When the Quick-Trak button is pressed and held (this pertains to all timings chosen) in the Fixed GB mode or simply pressed and released in the Tracking mode there is a brief five second period where the detector has a forced very fast GB that is much faster than any of the Tracking speeds, this is a time saving measure to quickly take the detector from a (worst case scenario) completely out of tune state to somewhere near tune so when the forced GB is finished the fine tune slower speed of the GB can do the rest.

Sometimes I find it more efficient to trigger the Quick-Trak button a couple of times when getting the GB precise, especially during the initial stages coming from a completely out of balance state. However it is not a good idea to release the button to fix the GB during this forced GB stage especially when you are working in the Smooth Class of timings as the Forced GB could easily change the last spilt second and throw the GB off the optimum position.

Best method is to only trigger the Forced five second process when the detector is still making noise as the coil is raised and lowered to the ground, once things quieten down keep the button depressed or wait at least five seconds so you can be sure the GB has settled down to a more manageable speed.

To elaborate further, Forced is just a speed rating during the GB phase, GB is automatic (driven by software) on the GPX 5000 with different speeds to suit different occasions (Menu operator selectable, Fast, Medium, Slow).

If in Tracking mode the speed of the GB is fixed at the speed selected in the menu, if the Quick-Trak button is triggered (pressed and released) then there is a brief 5 second fast forced section before reverting back to the chosen speed.

If the Tracking switch is in the Fixed position, the forced GB only happens if the button is held in, once the Forced GB is over then the detector will revert to whatever speed is chosen in the menu until the button is released again.
Posted By: Jonathan Porter on January 17, 2011 10:07am
hi jp.i live in the golden triangle of vic, and bought a GP 3500 a few months back(first) and after god knows how many 22 bullets and two sub grams of gold ,i am looking to go to a GPX 5000, the ground round here is looking like the locusts turned into rabbits (flogged out)even in scrub my den dog would have problems getting into.Im under no illusions of getting rich just tryin to justify to the other half an extra 3 or so grand. I have bought a 15 inch dd and a baby dd for the GP 3500 under advice that a mono wont cut it in this noisy ground .Would these coils run ok on a GPX 5000.Or would u suggest selling these for a mono I have read your settings for a mono would a dd be much the same. cheers
Posted By: cougarcans on February 05, 2011 08:26pm
Hello Cougarcans, stepping up from the GP 3500 to a GPX 5000 will bring you in line with all the people who are out there "flogging" the ground your seeing around the goldfields, which means you'll be on a much better footing with a greater chance of finding a few more bits of yellow than you have been up to date.

It sounds like the GP 3500 has put you well along the way to becoming reasonably well practiced in the arts of electronic gold prospecting but you perhaps now need to get on par with the technology that is currently available? Namely the new "Smooth Class" of timings in the GPX series of detectors.

The GPX 5000 has three such timings, Smooth, Enhance and Fine Gold, two of these timings were available in the previous GPX detectors but they have now been further refined in the GPX 5000 along with the inclusion of the New Fine Gold timings. As you have already discovered, the mineralisation in the Golden triangle can be extreme, to the point where you have to revert to the use of a DD coil, by going to a DD coil you automatically degrade the performance of your detector by quite a few percentage points.

The beauty of the GPX series is you can maintain the use of a Monoloop coil which offers the most out right depth performance of the two types of coils then with the use of the "Smooth Class" of timings reduce the amount of response generated by ground minerals whilst still maintaining in some cases near 100% depth or at worst case no where near as much as that lost with a DD coil relative to ground noise.

To put it another way, the minerals in the ground can mask nuggets, in your case with the GP a DD coil will help control some of those non target type responses but not all, it will however lose depth on all targets compared to a Monoloop coil. The GPX 5000 allows you to use a deep seeking coil but with the help of the timings also ignore the mineralisation far better than a DD coil can with far better outright performance.

If the conditions allow you can easily set up the GPX 5000 to work exactly the same as the GP 3500 including the use of DD coils. Some examples are, Cancel mode will still work well with the DD coils you have on hand around high interference areas or Conductive Salty environments, or the Mono mode will still convert a DD coil to a pseudo mono mode, in DD mode you have reasonably effective discrimination.

All the timings available to you with the GP 3500 are still present (except for the old Salt timing which has been replaced by a much improved Salt/Gold timing) so in every way the GPX 5000 will offer what has gone before. The only recommendation I would make is the "Smooth Class" of timings are not well suited to DD coil use unless you are working in Cancel or Mono mode and then there is a performance degradation. So to take full advantage of what the GPX 5000 has to offer it is best to use a Monoloop coil, one is supplied with the detector to get your started.

At the end of the day it comes down to what you're prepared to spend on your hobby, I can only advise you on the merits of what the technology has to offer, to that end I think the GPX series are right up your alley with the GPX 5000 being right at the top of the list.
Posted By: Jonathan Porter on February 07, 2011 10:53am
Hi after years of mucking about with old technology I upgraded to the GPX 5000' Can I get away with factory presets on the mono in Victoria.. this is a lot different to the VLF and TR machines I'm used to. Appreciate a response Phil
Posted By: philip.j.thompson on February 08, 2011 08:50pm
G'day Phillip, yes you can stick to the Factory Presets (FP), so long as you gain an understanding of how the timings work. Main thing to remember is the "Smooth Class of timings", Sensitive Smooth, Enhance and Fine Gold are designed for Monoloop coils and deal very effectively with mineralisation.

To access these timings you need to select a timing on the front end cap on the Soil/Timings Switch, two are dedicated timings which are Enhance and Normal, the other is Special which activates whatever timing is selected in the menu under the Special heading (5th from the top in the Main Menu using the Function Select dial), both Sens Smooth and Fine Gold are located in there with Fine Gold being the FP selection from Factory.

When using the "Smooth Class of timings" it is recommend you keep the detector in Fixed Ground Balance (GB) and use the Quick Trak button on the handle to GB the detector. When in Fixed you need to hold the Quick Trak button in and then pump the coil as described above. The Smooth type timings handle variable ground really well so you don't need to be ground balanced as often as other timings. Unlike VLF detectors it is not recommended leaving the GB slightly positive or negative as this will cost performance, always try to get the null exact (no noise either way).

For more information on your detector might I advise you get hold of a copy of our "The SETA Project" DVD (available at most good prospecting outlets or at ), although this video is primarily based about the GPX-4500 there are a lot of similarities between the two detectors.

Hope this helps,
Posted By: Jonathan Porter on February 09, 2011 10:33am
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