ADVANCED TRAINING

Very interesting air traffic animation. Thanks for sharing, TN.

The one thing ive always complained about...... Nox air testing. Having used most of the MLs this one seems all over the place. Wouldnt be so bad...... but it goes from a positive to a low negative even so you cant really get a feel for the average. Ive also found no problem being able to hunt near most Xcals...... which requires to noise cancel with most of my other machines. Over time with say the explorer or ET we got a feel for which channel (combined freqs) would work best where.

Tom..... when you said you could get 13.5" on a dime with the Nox..... was that the new program or old?



Edited 1 time(s). Last edit at 12/13/2018 11:33AM by dewcon4414.

Thank you for the suggestion and for helping me understand if this was possible.






Geotech Wrote:
-------------------------------------------------------
> EPL II Wrote:
> --------------------------------------------------
> -----
> > On my Equinox, I can AUTO noise cancel and get
> a different number each and every time I use the f
> unction
> > (I can push the button 5 times and get five diff
> erent numbers that the machine settles on) Is EMI
> / silent EMI
> > causing it to change that much in a matter of mi
> nutes?
>
> Probably means the EMI is close to equally prevale
> nt in those channels so it's a random choice. If y
> ou don't trust the auto-select, put it in all-meta
> l and do it manually.
>
> > Is there any way to incorporate an onboard diagn
> ostics / EMI monitoring system to constantly adjus
> t
> > (ever so slightly) the frequency or frequencies
> being transmitted?
>
> Ground and target signals would screw it up.

I guess 4" can be a pretty significant loss of depth....... and thats before you even try and GB it..... which frankly is as confusing as noise cancel with this machine. So if the noise cancel is selecting a different channel each time....... why would we think manual wouldnt do the same? Yes i find 2 channels this time....... but if i go back and test again, would that change or is manual more consistent/accurate?

One thing I have noticed.
Etrac FBS will when doing noise cancel be more apt when performing noice cancel again multiple times, to go to the same channel. EQX is it pot luck it seems when doing. I have compared EQX and Etrac in same sites standing more of less in the same spots holding detectors off the ground. Noted differences above.



Edited 1 time(s). Last edit at 12/13/2018 01:45PM by tnsharpshooter.

Steveg……. My concerns with nickels (or any mid and/or low conductors) at this site is:
* Are deep nickels even being detected.
* If so...… are the ID's correct.
* If not..... are the ID's mostly "up-averaging". . . . . . or are they "down-averaging". Or...……… are they departing the non-Fe spectrum..... and dropping down into the Fe range.

The neat thing about high-conductive coins is...… they have a tendency to "up-average" at the deeper depths. (((Deep nails may also do this))). This is to say; a "High-Coin" will up-average to "High-Coin". Sooooooo….. "Hi-Coin" falses to "High-Coin". Not a big problem. The user may/may-not know it. There is a tell-tale: The 'false' high-coin audio will sound more washed-out/blurred/smeared. Unfortunately...… a deep nail may false to "High-Coin"..... AND ALSO sound more washed-out/blurred/smeared audio response. Soooooooo…… how can the operator tell.

In summation:
* When a high conductor falses to 'high'; usually...…. this poses zero problems.
* When a (say) a nickel falses higher (into the pull-tab range)……. or falses lower (into the chewing gum foil range)…… nickels go: "missed".

{{{{{Then you have bad dirt...… whereby; everything deep ID's as 'iron'.}}}}}

Because of the instant/sudden shock of a change-for-the-bad increase in EMI at this particular site...…. I never had the chance to test my mid (and low) conductor theory at this site.

------------------------------------

dewcon = new and old program

EMI conditions can easily change...… even several times within the body of one second. It does not matter if you perform a auto noise-cancel..... or a manual noise-cancel. You may find that...….. one minute.... the best noise channel is 3. The next minute..... the best noise channel is 4. And the next minute.... the best noise channel is 1. So-on/so-forth. Auto noise-cancel will find this..... just as easily as manual noise-cancel. (((So why even perform a noise-cancel))).

You may be detecting smoothly/quietly. Then...…. all of a sudden...….. the detector experiences electric-shock...… goes crazy...… and for no apparent reason. (((As with the case of my 90' x 80' parcel …. stated above))).

Overall...……. the best thing you can do is; do the best you can with EMI mitigation...… and go hunt. At some sites...…. you may need to perform a (manual or auto) noise cancel more frequently...…. or less frequently; Site dictated.

Yes...…. all detectors are susceptible to EMI …….. silent or audible. PI, VLF or otherwise.

Yes...…. It is possible for a detector to (behind the scenes) be constantly looking/seeking the best EMI-quiet channel...… then continuously (and quietly..... without the operator knowing it)…… switching to the quietist channel...…….. even as fast as every second; YET/HOWEVER...….. I do not want to see this methodology. This would merely be a band-aid…… and accepting a certain level of mediocrity. This would fix the 'effect'...… and would not be fixing the 'cause'. WHAT IF...….. (through something called: 'Engineering Controls')……… the electronics could be designed in such a fashion whereby noise-cancel channels are not even needed...… due to technology that is immune to EMI...… from the get-go.

This EMI topic has just made me purchase a CZ-5; it should be here in a few days. I'm going to start going back over sites that I've hit super hard with my latest and greatest detectors and see what happens using the CZ-5.

tabman

tabman……. this brings up a interesting dilemma.

What if:
* You learn the CZ presents/provides the least amount of EMI...… in nearly all of the sites that you hunt.
* BUT...… what if the CZ is one of the worst units for carpets of nails. . . . . . . . which is (possibly unsuspectingly) where you mostly hunt.
* Or...…… what if you are a relic hunter...….. and the CZ is great on high-conductors, good on medium-conductors, and poor on low-conductors.

If we are going to go CZing, there is a can of new worms. I still have a couple 3Ds in the litter of detector puppies and various coils. As I recall coil size impacted EMI significantly with CZs and the newer coils handled it better than most older ones. Does that track with your experience Tom? Of course, size matters with any system, but my increasingly unreliable memory says it was more so with CZs than many other units.
Over the years I've had a couple 5s, some 7s and a 6. So I am somewhat familiar... As I again recall, it took a lot of reading and practice to learn how to ID nails and caps with them. There is a ton of great info in the forum's old posts and online on how to use CZs. Tom's DVD are gold there too! In fact I am going to re-watch them now!

Past(or)Tom
Using a Legend, a Deus 2, an Equinox 800, a Tarsacci MDT 8000, & a few others...
with my beloved, fading Corgi, Sadie



Edited 1 time(s). Last edit at 12/13/2018 04:54PM by Pasttom.

Tom,
Is there something in the works that you know of?


NASA-Tom Wrote:
-------------------------------------------------------
> Yes...…. all detectors are susceptible to EMI ……..
> silent or audible. PI, VLF or otherwise.
>
> Yes...…. It is possible for a detector to (behind the scenes) be constantly looking/seeking the best EMI-quiet channel...… then continuously (and quietly..... without the operator knowing it)…… switching to the quietist channel...…….. even as fast as every second; YET/HOWEVER...….. I do not want to see this methodology. This would merely be a band-aid…… and accepting a certain level of mediocrity.This would fix the 'effect'...… and would not be fixing the 'cause'. WHAT IF...….. (through something called: 'Engineering Controls')……… the electronics could be designed in such a fashion whereby noise-cancel channels are not even needed...… due to
technology that is immune to EMI...… from the get-go.

Yes.... yet; on a small-scale. Hopefully...…. it'll evolve.

NASA-Tom,

Understood, on all counts. Thanks for the thorough answer.

A question -- in your experience, if a particular machine tends to "up-average" high conductors at depth, is it reasonable to assume mid conductors will also up-average at depth, or is it possible that a given machine might UP-average high-conductive coins at depth, while also having a tendency to down-average mid-conductive coins at depth?

Also, the issue you raised, about the scenario where a machine up-averages a high conductive coin, but to a more "washed out" or "falsy" tone -- AND TENDS TO DO THE SAME THING, tonally, with NAILS, is a most difficult situation. Your question about "what to do" in that scenario is a question I'd love a slightly more "intelligent" answer to, than MY answer -- which is to "dig it all," if it's deep, at certain high-quality sites, especially once "better" signals are thinned out substantially. But I'm not convinced that a "more intelligent" answer exists...

Steve

This is a fascinating topic which (ironically) I think should really be titled ‘basic training’ rather than advanced because it is so important for every detector owner to know that most, if not all detectors {{{typically}}} will not pick or keep the ideal channel for EMI minimization. Accepting this as a given, this basic question came to mind: what is the easiest way to depth test a target (such as a dime) in the field, park, beach, woods, etc., while hunting, without carrying a yardstick or guestimating while swinging the coil above the ground? A method that’s quick, easy and fairly accurate so you can test the EMI channel/depth as often as necessary. I know some of you guys may have already thought about this, ideas?



Edited 1 time(s). Last edit at 12/14/2018 11:25AM by Gary in Daytona.

Gary in Daytona brings up a good point. What method (s) are used to test for the best channel selection?
Do you bring a yard stick or cloth tape ? Or, is the difference in channel selection so obvious that eyeballing it works?
Do you air test vertically or horizontally (oriented to the ground).
How often do you re-test?
Etc,...

Could you please give a brief step by step of your method? Thank you!

Dean

Gary...….. Since the top of the coil is nearly exactly the same sensitivity as the bottom of the coil...………,,,,,,,,,,,,,, and...……… I wave a dime over the top of the coil (for testing)…….. subsequently, I have graduated/incremented markings indexed on my lower coil stem. ((( I'm a bit surprised Mfr's have not done this yet. )))

Steve...… In the Rcpt Ack of F75LTD Proto thread...…. I explain just exactly this phenomenon. But...…. in a nutshell...…. from my low/no mineral Florida dirt; what I have discovered is: soil with oxides of iron..... will cause nearly all detectors to 'up-average' the ID of any/all conductive bandwidth targets...…. until the target becomes too deep; in which: now the target's ID will become 'iron'. Bad mineralization will also do exactly this.
If a non-ferrous target is near a solid iron object; there is a much higher propensity for the targets conductive ID to be pulled down; hence, 'down-averaging'.

In regards to 'washed-out high-tone' audio responses from deep nails......vs...…deep coins.,.,.,.,.,.,.,.,...… there is no steadfast scientific resolve. At times...…. I think I have figured something out; …….. then...……. I end up digging up a bunch more nails.,.,.,.,.,.,.,.,. zeroizing my theory. The only 'better' methodology.... is to have technologically advanced equipment that 'holds on' to accurate ID's at greater depths.

Regards marking the lower rod, I use one inch masking tape circles one inch apart. Beware...you can loose nearly an inch of depth (air test) from testing from the top of the coil vs the bottom on some coils so verify.

EMI is a rather complicated subject. Some coils need time to sync to ambient temperature so they chatter badly the first 15 to 20 minutes of the hunt then settle down, so you have to make allowances for that and re-evaluate after the first 30 minutes. Coil size has already been mentioned.

Most EMI deading zones have boundaries. They can be relatively small areas to large long ribbons hundreds of yards long but maybe only 10s of yards wide, depending on the source. You walk in and out of them. That is important to know as setting change on either side of the boundaries, and surprisingly, the boundaries can be very sharply defined.

Some detectors tell you about EMI differently than others. The F75 has the FA mode. You can be stable in Default and Boost and switch to FA and hear the constant machine gunning, Some detectors like the Xterras and F44 mute. By that I mean the audio responses are muted in the deadening zones. You can tell something is wrong. The FBS units get squirrel pitched audios,like the audio is off an octave or something. The V3 has the noise meter so you can actually check and see how much noise is picked up. Some detectors like the CZ just go dead.

And of course all of it is frequency dependent.

I love this topic because I'm so affected by it.

HH
Mike

Mike...…… well stated.

Dean; My systematic methodology for EMI mitigation is a follows:

After you perform a auto noise-cancel (as your 'starting point')……. IF your unit has 'auto' noise-cancel:
Find the one (or two...or three) EMI best channels (with least audible EMI)…… by manually selecting each channel.
Then..... set the detector down on the ground.....on its detector stand...... with the coil vertical. This places the coil perpendicular to the stem/rod.
Air-test a dime over the top of the coil...… looking at your graduated/incremented 'inch marks' on the stem/rod.
Switch between the 'known' best EMI channels on the detector...… and repeat waving the dime over the coil.
Note which noise cancel channel presented the best air-test depth.

Done!

Now...…. you may wish to change to 'other' channels that may be more noisy..... just for your own educational/tuitional curiosity...… to verify they are indeed worst/least performers.

Then go hunting. Be VERY keen/sensitive to any 'changes' in audible EMI. IF you hear a change; perform the EMI mitigation process all over again.
OR...…. if you hear no changes whilst detecting...…. it is a good idea to check your air-test status/performance...… about every 15-20 minutes. This is the best you can do. Yes..... there are plenty of occasions whereby EMI can change status multiple times..... and...… all within the body of one-second! You cannot control this. (((However; Technological engineering controls... might))).

Mike Hillis brings up a exacting phenomenon. That being...….. EMI is weird. It's in the air...…. and may be in a very discrete, well-defined corridor. You may encounter severe EMI exactly where you are standing; yet, move over 10-feet to your left...… and the EMI is gone. (((Makes me think of discrete-corridor microwave energy; yet, it's not. EMI is more white-noise/broadband in nature))). RF energy radiates/dissipates at a rate of inverse 6th Root; yet, EMI dissipation 'appears' to NOT follow this physics principle... on many occasions.

No-one has mentioned the (older) Nexus machines. Those who have used them report they are good in poor EMI environments. And as an engineer and Geotech1 regular, I have seen why. Quite simply, Georgi has designed the machines so they transmit a strong signal. Usually with a combination of higher voltages applied to the coil, and use of a tapped transmit-coil winding, so it functions like a simple transformer (an auto-transformer). The net result is he's perhaps applying 30 Volts to his coil, compared to more common levels of 5 to 10 Volts. This increases the signal-to-noise ratio, resulting in the interference being less obtrusive. It also makes other sources of electrical noise, like the front-end amplifier circuit, the receive-coil wire resistance, less important, too.
There are doubtless negatives, too. Increased power-consumption being an obvious one.

Making improvements to the 'receive' side of things is still beneficial, of course.

Pimento...…… Yes, with the advent of very low-power consumption units.,.,.,.,., coupled with hyper-gain Sensitivities...….. sets up a bed for EMI. . . . . . . . a bad combo for SNR. Yesteryears higher power to the coil..... presented MUCH better SNR & EMI mitigation. (((This is a form of better: Engineering Controls))). And...…………. with today's better capacitance (rechargeable) batteries; I'd like to see a reintroduction of more voltage to the coil...…. so as to 'overpower' the EMI. If I have to change batteries one extra time...… in the field...… this sure beats multiple, multiple, multiple EMI mitigation procedural executions.

Higher coil voltage/power is also nowhere near as detrimental to run-time as most people assume. The "most of the power goes into the coil" thought process is so very wrong.
Take a frugal machine like a Fisher F75, for example. Total power drain is about 50 milliAmps at 6 Volts, so 300 milliWatts. The power put into the search-coil is under 20 milliWatts [I'll try and find a better figure later]. If you doubled the coil voltage, the coil power would go up to 80 milliWatts. So total power draw would probably increase by 90 milliwatts (allowing for inefficiencies), taking it to (300+90) = 390 milliwatts.
This would drop the run-time down from 40 hours to 30 hours. So not ruinous.



Edited 1 time(s). Last edit at 12/14/2018 07:44PM by Pimento.

Does how high the gain is set change how EMI tests are done? Meaning do you run it wide open to check for the channel with the least EMI or do you run it half gain or just whatever you normally hunt at

Now Tom....... how does this play out in the water? Will it be more thru the coil from the earth? I know some like the Xcal have shielding ..... some of the Xcals even have a third wire which comes off the board that i assume is ground it for some reason. Neither works very well because on some Xcals you will get a bit of noise from when the water hits those knob stems. Joe (ole beach nut) has also stated when he placed the pods inside his rubber suit .... depth improved.

Thank you, Tom! I will give it a go this weekend...after making graduation marks on the lower shafts.

Dean

NASA-Tom --

Understood. Thanks for the reply. I know exactly what you refer to about the tendency, eventually, once you reach a certain (machine-dependent) depth, that IDs for all targets trend toward "iron" ID's. I learned of this phenomenon, and locked it into my brain, years ago, through extensive test-garden testing here in Oklahoma's irony-red clay...where such phenomenon is readily apparent. That's how I learned to choose detectors, for this dirt -- i.e. how deep, through test-garden verification, can a given machine "hold on" to reasonably accurate IDs of coins, before crossing over to "iron ID." The best ones in my dirt? Minelab's FBS machines, the Fisher Gold Bug Pro/F19, and the Equinox. The worst? Almost all other single-freq units, nearly all of which could not maintain a non-iron ID on a coin, with stock coil, beyond about 6"...

BEFORE you reach that "everything becomes iron ID" point, though, it's good to know that it's usually a consistent "up-average," across the board, for most/all targets at "fringe depth." I would have guessed that, however up-averaging (in my dirt) is not so noticeable on FBS units, which I have used for most of my time detecting. Hence, I don't have the "mental database" of such behavior as solidly in place as I otherwise might. That's why I asked. BUT, I DO see this up-averaging behavior much more clearly, on the Equinox.

I also appreciate the additional tidbit about the potential for "down-averaging," with non-ferrous targets residing near iron objects...

Finally, understood, about the difficulty in attempting to decipher "up-averaged" coin high-tone "falses" versus deep nail "falses." That is the MOST difficult part of detecting that I have experienced...ANYTIME I am 100% focused on deep coin hunting, it's easy for me to trend toward becoming too "aggressive," and I start digging abnormally greater number of deep nails. The only thing I have learned to do, when "fringe-depth coin hunting," is either put up with the nail-digging as being "part of the game," or -- turn up, JUST A HAIR, the "mental discriminator" between my ears, until the quantity of deep nails being dug is reduced to an "acceptable" level, based on mood/mindset at the time (while knowing that I'm also likely risking missing a coin that way)...

THANKS!

Steve

Steve...… your very last paragraph is worth 'framing'! This is SO true. You can even witness this from when you first start to hunt (before your fatigued)……. to the last part of the day...of your hunt; when you become more engaged in 'cherry-picking' mode.

Dew...…. Once a coil is submerged in the water...…. the bulk of EMI will go away. Interesting thing about beach hunting is...….. beaches are usually further away from EMI generating sources; hence, beach hunting (in general) produces less EMI; subsequently...…. Sens can be increased.

Pedlar…. Absolutely! The higher the Sens settings...… the higher the propensity to be EMI impeded. You need to set the Sens high enough..... (deep into the EMI)….. in order to have the best/most ability to mitigate. An example..... (and directly related to exactly this EMI issue)……… = If I can not hunt a site with a Sens setting of '22' (or higher) on the EQX (((due to EMI)))...… then the EQX goes back in the trunk of my car. Same holds true for other brands of detectors. ((( This is also to say: I am not a clad hunter. )))

Pimento: Correct. And...… if I remember correctly...… the CZ only has 27mW going to the coil. Very low power; yet, power consumption was merely 'average' (acceptable). But..... overall power consumption was fairly high...… for many reasons. (( Especially when comparing analog..... vs.... digital platform. ))

Can EMI change the way a high conductor sounds and the VDI same for low conductors .The reason I ask is some days I kill nickels and get maybe one silver other days I get silvers and Penny's with no nickels running the same noise channel .Also will EMI give high conductors better depth than low conductors and vice versa
on certain days depending on the EMI that's present .

I have plants at the places I hunt regularly a dime at 8 inches I will tune my detector to the best channel to get the best response on the dime


The air test on the dime is a great ideal especially when you can't find a clear place to ground balance at least you can tame some of the EMI and know how your detector will act in the area your hunting great tip . Thanks . sube

NASA-Tom Wrote:
-------------------------------------------------------
> Gary...….. Since the top of the coil is nearly exa
> ctly the same sensitivity as the bottom of the coi
> l...………,,,,,,,,,,,,,, and...……… I wave a dime over
> the top of the coil (for testing)…….. subsequently
> , I have graduated/incremented markings indexed on
> my lower coil stem. ((( I'm a bit surprised Mfr's
> have not done this yet. )))
>
Ahh, perfect and easy to do ... and agreed, that would be very useful. Thanks Tom

sube…….. That's an interesting thought; however, EMI only impedes/inhibits. I have yet to see a case whereby EMI 'enhances'. . . . . . regardless if it selectively enhances low-conductors, high-conductors.... or the full-spectrum broadband conductors.
However; there 'may' be cases where EMI "less affects" (less impedes/inhibits) detection of a certain conductive spectrum; yet, I doubt this. EMI is not discriminatory...…. it is more 'go/no-go' (broadband white-noise). . . . . . however, I do not have scientific data …. to generate theory-to-proof case model.

New ADVANCED TRAINING data as follows:

* Folks are thinking that: AIR GAP + BURIED DEPTH = DIRT DEPTH. This is not true. For those that followed the: Rcpt Ack of F75 LTD Proto thread........ a Decade ago...…..,,,,,,,,,,, presents probably the largest "remembered" example of the F75 (especially with 'Boost Process' BP Mode) having/giving/presenting a large air-gap forgiveness ability. The F75 LTD would (in my Florida dirt) detect a clad dime to 11.0" deep...….. AND...…… you could also still detect the dime ….by raising the coil up to 5" more inches above the ground.... before zero-detection. This would (implicate) equate to: 11" + 5" = 16". This is NOT true...…. and is a false assumption. Interestingly...…. if I pushed the clad dime to 12.0" deep...…. I would then have to scrub the coil on the ground ….. in order to detect the clad dime. If I pushed the dime to 12.1" deep...… it was completely undetectable. This is to say: The F75 LTD does indeed present tremendous air-gap forgiveness. One of the best air-gap forgiving detectors that I have ever tested. BUT...…. once again: AIR GAP + BURIED DEPTH...…. does NOT equate to total dirt depth capabilities of any particular unit. Some units will be better/worse in this phenomenon. Mineralization is the primary inhibiting culprit.

Now...…… as far as the Tarsacci……….. it is hard to say...……… as data is still quite preliminary. As far as /// In regards to...… the 8-Gram gold ring in the wet-salt....buried at 14" …. plus 7" air-gap. I would like to say...… the Tarsacci follows the same rules/principles of physics; yet/however...… when the wet-salt is tuned out...…. the wet-salt then (and only then)…. nearly looks like 'air'. Sooooooooooooo………….. 14" of 'nearly looking like air'..... plus the additional 7" of air-gap.,.,.,.,.,.,.,.,.,.,.,. it's hard to pontificate/speculate what the reality truly holds. Shoving that 8-Gram gold ring deeper is the only way...…. that would present real/hard/exacting/irrefutable data.

Alain Loubet…… with the XP-Series units...….. certainly presents some: defying-rules-of-physics "looking" phenomena.
Dimitar thinks differently also (as does Alain)...… so...…. maybe the Tarsacci ……. with its out-of-the-box thinking ……. can do things 'differently'. Real-World testing will 'present'...….. and preside.