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#3→→ GROUND BALANCE --- Some can be, some can't. ... Another Lengthy Post.

November 04, 2020 11:03AM avatar
GROUND BALANCE

Some are partial and some are full control. And then factor in Search Coils.confused smiley

It seems like most average metal detecting Hobbyists don't really understand what it means, what it is, and what benefit we might achieve if we make such an adjustment with some metal detectors. A good share of the more Avid Detectorists are also a bit lost when trying to understand how it might or might not have a bearing on performance in a Discriminate mode as well as All Metal. The problem with understanding 'Ground Balance' is while we think we know how all those metal detectors out there are supposed to work based upon their available adjustment settings, most of the time it is unknown because the manufacturers, and even the design engineers, don't fully explain the circuitry design, the limitations in their designs, and I even think a few detector makers just don't understand a few things regarding how they make it work.

Have I lost you? Okay, go read some other forum posts, but first .... do YOU know how YOUR detector was designed and actually works when it comes to 'Ground Balance?'

What is 'Ground Balance' that's been around on hobby-based detectors since George Payne engineered the White's Coinmaster 5 Supreme about 1974/75. It was the 'original' VLF Ground Cancelling detector that lacked any Discrimination. That came later. with their Coinmaster 5D ... hint abut the letter 'D'. Prior to this, most conventional TR's operated at, or very close to, 100 kHz. You had, by the latter '60s and very early '70s, basically a choice between a BFO (Beat Frequency Oscillation) model that produced a frequency or pitch change, and the Transmit / Receive, or TR that worked at a fixed frequency and produced a volume or loudness change. At first or the same time they were called IB designs for Induction / Balance which is Transmit / Receive in the more popular lingo.

With our hobby-based TR's you needed to position the search coil close to the ground and adjust the Tuner control for a proper slight-audio 'Hum' or audible Threshold sound. Then, for best performance sweep the coil side-to-side while maintaining a uniform coil-to-ground relationship in order to maintain that slight audio Threshold 'Hum.' Why? Because ground minerals have an effect on the Electro-Magnetic Field that radiates around the Transmit winding.

If the search coil is moved lower, towards the ground, the audio Threshold Hum will usually diminish or go silent, into the 'null,' and you will lose detection ability as well as depth. That is because there is now a greater ground mineral effect on the EMF, especially the more intense or strongest portion of that field closer to the coil.

If the search coil is raised away from the ground, which then reduces the amount of negative ground mineral effect on the EMF, the Threshold Hum will increase or get louder. Why did the Threshold either 'null' and go silent or increase and get louder? Because the TR detector was then 'Out-Of-Tune' and to restore proper operation, the search coil needed to be returned to the former position from the ground to hear that slight audio Threshold Hum,or, they would soon at either a push-button or toggle-switch so the operator could manually re-tune the detector at a new coil position to a proper Threshold setting, or they added auto-tune circuitry to automatically re-tune to a proper Threshold level Hum.

Adding switches or circuitry helped make life easier because it was not as difficult to maintain a Threshed 'Hum' since you didn't have to pause to manually adjust a Tune control. which was most often a two-handed operation to hold the detector and adjust the control. So new adjustments or circuitry was helpful, but the issue causing the problem was still there ..... the ground generalization. How could a design engineer help us out on that problem so we wouldn't have to constantly adjust and re-adjust and keep a proper coil height, or deal with terrain texture challenges, such as sweeping over a dirt mound or sweeping over a depression or hole. Causes that were similar to lowering a coil or raising a coil with relationship to the ground.

By this time we had Discrimination added to our TR detectors making them a TR-Disc. model. Unfortunately,, with that 'progress' made in detector design, we lost some in-the-field performance with many, perhaps most, TR-Disc. models because the lower-end Disc. setting was rather high. Some were rejecting Iron Nails at that minimum setting and others might accept them, but wouldn't adjust much lower. They mostly lost their ability to handle Iron nails like a good, conventional, non-Discriminating TR. Those early start TR';s essentially ignored Iron Nails

For example, note the 'perfect' '42' Points scored in my evaluations using a very basic Compass Coin Hustler I. A one-knob detector to turn it On and adjust a functional Threshold audio Hum. That's it. No Discrimination, no Sensitivity, no other controls at all. Very 'basic,' and, back in those very late '60s and early '70s years, they found a lot of good targets in all sorts of places, to include those with a lot of Nails and other Iron debris. Were thy as easy to use as what we have today? Well, maybe not, but they were simple and if you wanted to find stuff you simply learned how to adjust the detector, maintain a proper coil height, and make sure you maintained the best Threshold 'Hum' you could.

Iron, that blasted ferrous-based annoying material that was human-formed into a metal object that causes us fits, just as rusty tin, round iron washers, and most crimp-on Bottle Caps still do. If looking at a Discrimination range, or better still a Conductivity scale, you will see that all that pestering ground mineral is pretty bunched up way off on that lower left-side on the upper portion of a phase angle were we find things like nails and such. That's where the ground mineral would be, down lower, and we wonder what to do with that ground mineral so it can be ignored and not cause up problems?

George Payne, the savvy design engineer working at White's at the time, figured out how to accomplish cancelling the effects of the ground mineral by tuning out the ground, but to do so, detectors worked best if they operated at a Very Low Frequency than the 100 kHz or so of the currently popular Tr and TR-Disc. models. Thus came the new term, VLF, and it described most detector that operate in the 1 kHz to 30 kHz frequency range. Initially, most worked very low, like somewhere around 1.75 kHz to roughly 5 kHz.

White's Electronics brought out their first, the Coinmaster 5 Supreme, and Garrett Metal Detectors soon followed with the DeepSeeker VLF, and that started a popular use of the term 'VLF' which initially meant the detector worked in that VLF range of 1-to-30 kHz. But quickly we had another new term that was brought into use, and that was All Metal. Before we usually used the very popular TR's that ignored most Iron nails and responded well to most non-ferrous targets. We were not looking for 'ALL' of the metal targets. And then with TR-Disc. models that didn't adjust very low, most ferrous trash was rejected so, again, we were not really hearing ALL metal, to include both ferrous and non-ferrous.

But once we had a VLF detector that canceled the ground, or balanced to the ground, or ignored the ground mineral signal, the new VLf's would beep on EVERYTHING out-of-context with the ground, and that meant ALL metal targets be them ferrous or non-ferrous. For devoted Relic Hunters back in the day that was great! They could go out and find all sorts of iron and non-iron stuff. For the average and greater-number Coin Hunting Hobbyists, hearing and recovering everything was just not fun. The needed to be able to reject common trash, to include Iron. thus came the 2-Mode detectors called a VLF / TR-Disc.

Search in the All Metal Accept VLF mode and not worry about the ground mineral issues and coil height, or not quite as much, and then when a target is located and Pinpointed, move the coil to the side, switch to the TR-Disc. mode, then carefully work the coil back over the targets and listen for: 1.. A nulling out of the Threshold or 2.. A 'Beep' or 3.. No change in the Threshold audio.

You ignore the Discriminated trash with #1 and then you would recover all #2 and #3 conditions.

Fast forward and today we have all sorts of detectors that might or might not have a Threshold-based All Metal mode, and most models with a Discriminate mode. Not an old traditional TR-Disc. design, even though they are still operating with the TR principle, but in '78, the same George Payne, then working for Bounty Hunter, brought us a new nifty name, Synchronous Phase discrimination, or SPD, and that was just a nice way to introduce VLF-Disc. The ability to search in a Ground Cancelling mode that also Discriminate unwanted trash.

That really made life easy, or kind of. we could then ignore the ground and ignore unwanted junk, but to accomplish that marvelous task the search coil had to be swept very, very briskly. It would almost look like a golf club swing, but that early circuitry required that in order to process both the ground signal and target signal, then extract th ground signal and pass along the target signal. That's the simple explanation.

Some manufacturers then made 3-Mode detectors with VLF or All Metal, and VLF-Disc, under different names, and even a former TR-Disc. mode to be used w/o the brisk sweep speed. That continued until 1982 and 1983 and we saw three new introductions to the detector world, as well as two more well-known names. in 1982 we got the talents of Dave Johnson in the Fisher 1260-X which gave us our first really notable slow-motion detector with quick-response and fast-recovery. No more brisk coil whipping and a lighter and more comfortable package.

We also had the new start-up company called Teknetics, where, once again, George Payne brought out the first Target ID detectors in the Coin Computer 9000 and 8500 top-end models Brisk sweep, yes, but usable technology .... if you don't get too carried away with it, referring to visual Target ID. And then not too long after they went to the 'B' versions, the 9000 B and 8500 B, which meant they were the first devices with both Target ID and audio Tone ID.

The third entry, and the one that has been more important to me, also came in 1983 when Jack Gifford, also an engineer and founder of Tesoro Electronics, introduced his Inca in July of that year. It was the 'other' notable slow-motion, silent-search, quick-response / fast-recovery model, to rival the Fisher 1200's from '82, but the Tesoro circuitry design was far superior at handling Iron Nails and similar typical ferrous trash that the Fisher's struggled on with a lot of clicks and chirps and rough-sounding noise.

Okay, I might have wandered a little off the main topic, but it was to point out that thanks to ground mineral challenges and the effort made to handle the ground mineral that's out there, everywhere, these are the things that brought us to where we are today. Mainly using TR circuitry models that mostly work in the VLF range, and provide some form of control to handle ground mineralization.



What Type of Ground Balance does YOUR Detector Have?

Let me insert this one comment here. A lot of manufacturers do not tell you how a detector's circuitry works with GB, if it is fixed in-circuitry, controlled in-circuitry, internally adjusted with a trimmer, manually or automated GB, and for sure a lot do not disclose if the Ground Balance, internal, automated or manual, is a function of an All Metal mode, an All Metal Pinpoint mode, and if automated or manual GB is also tied in with the Disc. mode's GB setting. I'll tell you that I DO know what I have learned myself or had disclosed to me, but I'll also let you know I am NOT sharing that info. If you're comfortable with how your detectors work, fine. If you're not sure, it might be an interesting experience to track down an authoritative answer. thinking

There can be:

► Ground Balance that is all handled "in-circuitry" and you have no control.

► Ground Balance that is adjusted with an internal GB trimmer, and this is also called a 'Fixed Ground Balance.'

► Automated GB, also called Ground-Grab or Fast-Grab or other terms, that requires a bobbing of the search coil from about 6' to 1" from the ground.

► Manual Ground Balance that is adjusted by the detector operator.

► With some detectors that have a Manual GB control tied in with the Discriminate mode, you can also make a functional GB adjustment when in the motion-based Disc. mode that I termed 'Power Balancing' about 1980. Here's a hint: For about 40 years now I have been able to 'Power balance' some of my favorite detectors for different ground mineral conditions. During that 40 years, there are many makes and models that do not provide that capability.


Models with a Preset or Default Ground Balance ... and what that read-out is:

Many makes of detectors will display a numeric Ground Balance, or a Ground Phase, read-out at turn-on. For example, with the White's MXT series, the default turn-on GB read-out is '83.' The M6 lacks a visual display but White's used the same circuitry design from the original MXT to make the M6 and it, also, turns-on with a GB of '83.' The MXT series and the M^ have a toggle to activate "Tracking' you can bob the coil to establish a GB for that particular ground make-up, then let the detector 'Track' to changes in the ground (I never do) or toggle to the center 'Lock' position to hold that GB reference (I always do).

The issue I personally had with the MXT Pro and All-Pro (same detector) models I had was that I was used to using detectors with a Manual GB control, and the high-dollar MXT Pro / All Pro does not have a manual GB control. Nor do the MX Sport or MX-7 models. It's Automated GB and 'Lock' or allow it to Track. Or ----- a user can turn the detector and, with some models like the MX-7, have it start out at the previous GB setting IF it was 'Locked' at the time the detector shut-down.

That was one of the things I liked about the MX-7, kind of like I have my XLT. I have the Auto-Trac turned 'Off'' and when I turn on the XLT and quickly pull the trigger, it starts up as I was last hunting and that includes the Ground Balance setting. So it is with the MX-7 and I leave the Tracking in 'Locked'. I hunt a lot of places with so much metal trash it's difficult to find a clean sport to GB, so .... I find a more mineralized rock at that site, or for all of the areas around where I live, and I Ground-Grab for the more mineralized ground in that area. It's 'Locked' so the MX-7 'saves' that setting. Turn it on a week later and a thousand miles away and it it at the last saved and locked GB setting. I can always do a Ground-Grab to update to whatever a location might be, and when 'Locked' that GB is then saved.

Some makes and models have an automated Ground Balance function, but they don't have a Threshold-based All Metal mode, such as the new Garrett Apex. It only has the programmed Discriminate modes plus a Threefold All Metal Pinpoint function, but is otherwise silent-search. But has the GB feature. Then some models do have an All Metal mode and Discriminate modes and both an automated GB as well as manual GB, like the Simplex + or T2+.

Under my roof right now, since I brought in my travel units to charge up tonight for some hunting tomorrow, I have the following:

1- F5
2- Apex
1- Racer 2
1- Vanquish 540
1- FORS CoRe
1- FORS Relic
1- Midi Hoard
2- Simplex +
1- Omega 8500
1- T2 +
1- MX-7
2- Bandido II µMAX
1- Silver Sabre µMAX


Of these some are staying put and the others, mainly brand new for the testing, are going to be sold. Of those that have been on-hand and one new model that I am hanging onto, 4 of them have a GB adjustment function that IS tied in with the Discriminate mode as well as All Metal. I shared that with UtahRich last evening but for most readers, that might not matter. To me, it does. Some of my models don't, but that's okay, too, because I know what they can do as designed, and having the assortment I do lets me pick-and-choose which detector/coil combination I want to grab for a particular site or needed task. Translated, this paragraph simply suggests detectors can differ in operation, and it's best if the operator spends the time to learn and know the strengths and weaknesses of the detector(s) they intend to use.


Now, What About Search Coils and Ground Balance ???:

When I read Forum Posts and people relate what they used, where in general they hunted, and what settings they used as well as the Ground Balance read-out, that last bit of information might not means a lot unless I knew what detector was used as well as which search coil. Then, I would know how THAT detector & coil reported the Ground Phase read-out, and at that point I just need to know how that compares to what unit I am using and the coil mounted. Did I lose anyone yet?

Let's say OrgonGregg has his MXT Pro at a site and turns it On in the Prospecting mode and sees the Ground Phase reads '83', but I am 30 miles away with one of my Garrett Apex devices and turn it on and report that my Ground Phase read-out is '93.' What does that suggest to you? Does it give you any idea who is over the more mineralized ground? No, it doesn't. All it tells me is that at 'turn-on' (without doing any GB procedure) both the MXT Pro and Apex were showing their default GB number.

Most manufacturers will say they use a piece of ferrite to determine the default GB read-out, but each manufacturer, and likely different models, use a different GB reference number. Part of that can also be related to the spread of the VDI display they use, how they consider the Ferrous / Non-Ferrous break-point, or ??? What we do know is that manufacturers do things differently. We also know that some models do not show any display reference to a 'Ground Balance' or 'Ground Phase' setting, and/or the particular model has the GB 'controlled' in some fashion so the consumer can't hear any subtle change they might make with a control.

Out of my list above, those models would include the Minelab Vanquish 540 and the Nokta / Makro Midi Hoard. All the rest let us see a GB setting or hear the effect of a GB setting. That's good to know, but it is also important to know that Ground Balance adjustments are also tied in with the particular search coil attached at the time. Changing a search coil will also result in a different GB read-out or search mode behavior.

Here are some examples of Ground Balance differences, and I'll only use the models that have a GB read-out. Here is the 'default' GB read for those models:

82.70 -- F5
93 ------ Apex
90.00 -- Racer 2
90.00 -- FORS CoRe
90.00 -- FORS Relic
90.00 -- Simplex +
82.9 ---- Omega 8500
90.60 -- T2 +
69 ------ MX-7 (Note: I went to Default start-up 5 times to see the same default read-out. I am surprised.)

As you can see, the 'default' turn-on GB settings can differ from model-to-model. But when you make a GB adjustment for specific ground, that might bring the detector into the best operating ability, but that is fr the particular coil mounted at the time. Change search coils and adjust the GB over the very same spot, and the GB read-out will generally differ. Here are some results.

I have an ugly-looking rock on-hand that I brought home from an 1870's era gold mining site. I use it to help 'calibrate' or 'adjust' the GB trimmers for a lot of "turn-on-an-go" detectors that rely on an internally-set Ground Balance. This heavy rock measures about 7" long, 5" wide and 2¾" thick at the greatest measure. It's big enough to effect a lot of the EMF to get a decent GB setting adjustment. Here are the GB readings over this very same mineralized rock using the different search coils on-hand for the models evaluated. I show the model with their default GB setting:
:

82.70 -- F5 w/5" DD .. 67.0, w/7" Concentric.. 78.7 and w/11" BiAxial.. 82.1

93 ------ Apex only w/6X11 DD, using different frequencies: 5 kHz.. 91, at 10 & 15 kHz.. 93, at 20 kHz,, 94, and at MF.. 93.

90.00 -- Racer 2 w/5" DD.. 87.80 and w/7" Concentric.. 82.40

90.00 -- Simplex + w/11" DD.. 89.00 and w/5X9½ DD.. 87.20

82.9 ---- Omega 8500 w/11" DD.. 67, w/10" Concentric.. 78.5, w/7" Concentric.. 76.5 and w/5" DD.. 68.8

90.60 -- T2 + w/11" DD.. 86.8 and w/5" DD.. 82.0

69 ------ MX-7 w/6½" Concentric.. 73


From the above, it can be interesting to know generally what the GB readouts are that posters report, but the information wouldn't be that useful unless you know the coil used, and then know how that might relate to the detector and coil you are using. Search coil changes can make quite a difference in the GB and therefore in performance. That also points out why I like to tweak a preset GB unit, like my Tesoro Silver Sabre µMAX, for peak performance with the search coil I plan to use on it exclusively. This also shows why coil change can sometimes result in a detector falsing a lot or not being able to work well afield should the GB setting be significantly 'off'..

If this coming winter is going to keep you indoors a lot, maybe you could find two or three really challenging rocks and spend some indoor time getting to know your defectors better?

Enjoy what you have, learn what you have, and when the opportunity confronts you, get out and use what you have.

Monte

"Your EYES ... the only 100% accurate form of Discrimination!"

Stinkwater Wells Trading Post
Metal Detector Evaluations and Product Reviews
monte@ahrps.org ... or ... monte@stinkwaterwells.com
503-481-8147
Detector Outfit: A selection of my favorite makes and models, with the best coils mounted, for the tasks I'll take on.
Pinpointers: Pulse-Dive & ProPointer AT .. Headphones: 'Hornet' & 'Wasp' .. MS-3 Z-Lynk .. ML-80 .. N/M Green edition
*** All working well today to make memories for tomorrow. ***




Edited 1 time(s). Last edit at 11/06/2020 10:57PM by Monte.
Subject Author Views Posted

Some fun evaluations of 10 Brand New Detectors you can buy for $550 or Less.

Monte 194 November 01, 2020 07:56AM

#4→→ The Compass Coin Hustler and why the '42' Point high score?

Monte 64 November 05, 2020 04:55AM

Re: #4→→ The Compass Coin Hustler and why the '42' Point high score?

D&P-OR 46 November 05, 2020 10:50AM

#3→→ GROUND BALANCE --- Some can be, some can't. ... Another Lengthy Post.

Monte 70 November 04, 2020 11:03AM

Rambling a bit about: Ground Balance ... Target ID ... Search Coils.

Monte 40 November 07, 2020 11:42AM

GB, Target ID, Search Coils.

UtahRich 36 November 07, 2020 05:08PM

Re: GB, Target ID, Search Coils.

Monte 31 November 08, 2020 07:32AM

Great Post

OregonGregg 39 November 05, 2020 06:40AM

Re: #3→→ GROUND BALANCE --- Some can be, some can't. ... Another Lengthy Post.

EL NINO 42 November 05, 2020 03:36AM

'Thank You' for the kind comments. ---- I put 'SAT' on my to-do list.thumbs up N/T

Monte 27 November 05, 2020 03:50AM

Re: #3 another Lengthy Post. Great post Monte thumbs up Thanks for that informative lesson!!!!! N/T

Hombre 31 November 04, 2020 10:26PM

Randy, my pleasure. As always, I learned things myself.

Monte 39 November 05, 2020 03:47AM

#2→→ My comments on the 10 New Detector Models Tested ... Very Lengthy..

Monte 76 November 03, 2020 04:17PM

Re: Some fun evaluations of 10 Brand New Detectors you can buy for $550 or Less.

WM6 45 November 02, 2020 06:03AM

Re: Some fun evaluations of 10 Brand New Detectors you can buy for $550 or Less.

diggindeep 52 November 01, 2020 11:02AM

Back to you, Andrew.

Monte 53 November 01, 2020 02:30PM

Re: Some fun evaluations of 10 Brand New Detectors you can buy for $550 or Less.

Timbertodd 41 November 01, 2020 10:35AM

A quick reply to you 'Timbertodd.'

Monte 45 November 01, 2020 12:46PM

#1→→ Evaluation Scores w/Detectors and Coils ... plus the 100% performer.

Monte 108 November 01, 2020 09:38AM

Re: Follow-up #1.. Evaluation Scores w/Detectors and Coils

Kickindirt 44 November 02, 2020 12:31PM

Joel, an interesting guess .... but wrong. Let me comment.

Monte 56 November 02, 2020 01:37PM



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