((( Andrew......... I am more concerned about your DIRT! ))).

basstrackerman....... And THAT is a textbook-perfect example of the very premise (of my sleepless nights) of what I am forging to mitigate.

goodmore..........yes. ANY "wireless" device is substantially more prone to noise/EMI. And NOT to revert backwards from advancing the technological advancements; yet, I will NOT hunt with a wireless coil ...... and I will (especially) NOT hunt with wireless headphones. Latency has been (mostly) cured; yet, random blanking has not!

The T2/F75 platform...... were (still are) the most expressive EMI talkers in our detecting community. In fact...... they express EMI so well....... I don't ever recall experiencing any "silent" EMI on a T2/F75. If there was ANY EMI at all..... the T2/F75 would 'express'. I (kinda) liked this because..... you ALWAYS "knew" when there was troubles in the air. Nothing was 'silent' or hidden. You could easily measure how much performance loss you would have...for that day.

In order to progress forward........ I have had to look rearward.

Dew........ larger coils have brought about greater depth; yet, at some cost/side-effect(s).

Steve........ thanks for the Kudo's.

------------------------------------
In time........ all of my writings will make sense.

Not Minelab or Equinox related but to Tom's EMI observations; on Steve H's site there is an interesting discussion on the new Detech Arrow coil. This is intended to be an updated Bigfoot/Cleansweep type coil. It was stated that the original Whites Bigfoot for the DFX had a figure 8 coil winding that gave the coil very good EMI mitigation. Also the polarity of the windings were different than "normal". Maybe some of the looking back Tom is doing? Also it was mentioned to me by someone who should know that the Deeptech Vista X uses a reversed polarity for it's coil & that is a big part of it's high resistance to EMI interference. It would be great if the answer to the EMI problem was fairly simple but just overlooked.

Chris

Why can't EMI not be eliminated or reduced with coatings on the top side of the coil wires?????

Because nearly all EMI enters through the coil. (And not the coil wires.....of which.....are usually shielded).

NASA-Tom Wrote:
-------------------------------------------------------
> Because nearly all EMI enters through the coil. (A
> nd not the coil wires.....of which.....are usually
> shielded).

Yes Tom. To be more specific I was not talking about the wires from the box to coil.

My thoughts are to the windings in the coil itself. Why could there not be a shielding topside of the windings as you look down at the coil? .

Didn't Whites have that small diameter coil that could be used around metal fences? I remember it was thick and shielded on the top to prevent a signal from anywhere but the bottom of the coil. I never used one, but I remember seeing them advertised.

Tom,
Great info on this EMI issue, it is definitely eye opening. It make me kind of see we are using ‘guesstimate’ technology to automatically noise cancel on the Nox or any detector for that matter, when it is really requiring highly precise skills and technology to ascertain the true EMI / noise cancel setting for optimum detecting capabilities of the detector. And there aren’t many places that you don’t encounter EMI from a variety of sources including the aforementioned cell phones and other detectors. Now I understand why if you Noise Cancel a few times, you get different channels to operate on. Never made sense to me, but now it does.
I guess it would pay to just stop detecting for a few minutes when another detector passes by on the beach rather than move ahead walking over targets you can’t hear? Lots to take in… but for starters, I for one, am going to start paying much more attention to the manual ‘fine tuning’ of the noise cancel and checking it more often.

Tom, I guess outside of lowering sensitivity, there isn’t much we can adjust on the MDT8000 to help with EMI?

TIA

On the MDT 8000 using Black Sand ON helps settle the machine on most of the EMI that I have encountered. It also helps on ground with a lot of tiny Iron flecks to reduce falsing.

Chris

mida....... with current technology "shielding the top of the coil" would create a large/interfering 'null'..... of which..... would distort the overall footprint of the coil.

Gary.......the MDT is fairly good at mitigating EMI; yet, there is no mode/means/methodology that is user/operator adjustable .....to fix/mitigate EMI when you encounter it....on the Tarsacci. The only thing that I do is...... drop Sens to '5'. If I have to go lower in Sens....... I will switch to a different brand unit. There have been times whereby......I switched to a different frequency on the MDT..... with 'some' success in EMI mitigation. Sometimes a freq change can make the problem worse. When trying one of the other freq's...... IF this fixes the EMI issue....,,,,,,......,,,,,,.......,,,,,,,........ it now becomes a matter of: Did this freq change 'self-defeat' the intended conductivity of targets being hunted.
Chris....yes. Sometimes Black Sand "ON" can mitigate certain types of EMI. I have experienced this a few times.

Thanks Tom, it’s not a problem all that often unless I enter an area that I know has EMI from prior visits. And what you mentioned is what I try, and in the same order was well, except I try not to run very longs at 5, I’ll try other things first. (Black Sand, Frequency, rebalancing settings.) Some thing seem to work, some don’t just as you said, and in the case of frequency, it sure seems you can make it worse. I wonder if you’ve noticed if you have more EMI noise from the Beast rather than the original coil, I haven’t but thought I’d ask? Anyways, the experimentation continues…

There have been times where I 'think' I have encountered a slight more EMI with the 12" coil; yet, truthfully........ I do not think so.

goodmore Wrote:
-------------------------------------------------------
> Didn't Whites have that small diameter coil that c
> ould be used around metal fences? I remember it wa
> s thick and shielded on the top to prevent a signa
> l from anywhere but the bottom of the coil. I neve
> r used one, but I remember seeing them advertised.


Goodmore, I think you're remembering the Jimmy Sierra co-axial coils for White's. (Garrett and C&G also made several co-axial coils for their own detectors.)
They're not exactly 'shielded on top', per se....it's a special winding design.....but they are wound in such a fashion as to make them quite thick.

I believe a search for "coaxial metal detector coil" may give you more info.
mike

NASA-Tom Wrote:
-------------------------------------------------------
> mida....... with current technology "shielding the
> top of the coil" would create a large/interfering
> 'null'..... of which..... would distort the overal
> l footprint of the coil.
>
> Gary.......the MDT is fairly good at mitigating EM
> I; yet, there is no mode/means/methodology that is
> user/operator adjustable .....to fix/mitigate EMI
> when you encounter it....on the Tarsacci. The only
> thing that I do is...... drop Sens to '5'. If I ha
> ve to go lower in Sens....... I will switch to a d
> ifferent brand unit. There have been times whereby
> ......I switched to a different frequency on the M
> DT..... with 'some' success in EMI mitigation. Som
> etimes a freq change can make the problem worse. W
> hen trying one of the other freq's...... IF this f
> ixes the EMI issue....,,,,,,......,,,,,,.......,,,
> ,,,,........ it now becomes a matter of: Did this
> freq change 'self-defeat' the intended conductivit
> y of targets being hunted.
> Chris....yes. Sometimes Black Sand "ON" can mitiga
> te certain types of EMI. I have experienced this a
> few times.

Tom, can you elaborate more why top shieling would not work?

midalake........ First...... the coil of a metal detector is not to be looked upon as a 'antenna'. It does not impart antenna theory. Think of the coil of a metal detector as a 'inductive loop'....... that inductively 'couples' with a metallic object within its electromagnetic field. This field is a 'null'. , . , . , . , . , aka: a perfectly balanced field......between the Xmit & Rcv loops. When a metallic implement enters its field...... the field is badly disrupted. This electromagnetic footprint (field)..... is below the coil .....and ABOVE the coil...in equal fashion. (((EM field looks like a doughnut....above and below the coil))).
If a 'shield' is placed above the coil..... this will badly (fatally) distort the 'balanced' field. EVEN IF (to include) the shield is designed in such a fashion as to be a faraday-cage (metal mesh shield).
In the old days....... the bolt and wingnut that holds the coil onto the lower shaft....... would create a null spot(s)....... above-and-beneath the coil!!! In the old days...... we would swing a coil that had blind/bliss 'null' spots underneath the coil.......BUT........ because you could not see the electromagnetic footprint of the coil........ nor how badly the 'field' was distorted. Heck...... many detectors even used metal (usually aluminum) lower shafts!!! The detector would not report a 'target' response ....because of the metallic shaft and/or steel bolt/wingnut combo...... because they were stationary to the coil. Yet.... blind spots ensued.

But.......but........BUT.........(not to be a kill-joy)......,,,,,,, I still feel that a paraboloid reflector above the coil (as long as it is held EXTREMELY stationary)..... could be 'nulled' above the coil (or reciprocal-juxtapose the 'above' EM footprint .....into the 'below' EM footprint)........,,,,,,,and................... ultimately.............. achieve our desired intent! But...... as of now.....there's a couple of physics defiants to surmount.

Tom, what an informative reply, i've learned a great deal by following your posts, thank you for continuing to share your knowledge!

So does it follow that the conductors of the coil cable are also an issue for the reasons you describe?

(((Tim.......my concern is.......I chased more people away!!!!......and they ran over to findmall or other forums!)))

The coil cable on most of today's modern detectors IS shielded. Although not perfect........ the cable is hardly detectable to the coil (the detector).

Once again............ I'm still shocked that we are still: * Within the antiquated methodology of a lump-of-wire at the end of a stick...... to find buried objects.

(((It's hard to think outside the box....... when you are imprisoned deeply within the interior of the (proverbial) box))).

Tom,

Do you personally have anything in mind and is there something in the works to alter that "lump of wire at the end of a stick" ?
As I have mentioned in the past, I run here for all technical / operational information. The wealth of information you freely share I do not take for granted.
I sincerely appreciate your willingness to share your knowledge.



NASA-Tom Wrote:
-------------------------------------------------------
> (((Tim.......my concern is.......I chased more peo
> ple away!!!!......and they ran over to findmall or
> other forums!)))
>
> The coil cable on most of today's modern detectors
> IS shielded. Although not perfect........ the cabl
> e is hardly detectable to the coil (the detector).
>
> Once again............ I'm still shocked that we a
> re still: * Within the antiquated methodology o
> f a lump-of-wire at the end of a stick...... to fi
> nd buried objects.
>
> (((It's hard to think outside the box....... when
> you are imprisoned deeply within the interior of t
> he (proverbial) box))).

Jim....... I have merely but one conceptual notion up my sleeve. ((( I am in Theory-to-Proof phase ))).
But....... there is one entity (at present) that is working on a (somewhat tangential) targeted idea; yet, it is a fairly large decelerator to 'aggregate design intent'.

This is the limit as to what I can share... on this segment of the time-continuum.

Thanks Tom for the reply.

I know that I have alluded to this before.....about the EQX; yet, it has become "primary"......and to a huge extent.

First: We know that (say) Park Mode-1 is designed for deep high conductors.......like silver coins. We also know that (say) Field Mode-2 is designed for low conductors.........like the tiny paper-thin coins of old European.
I have been 'trying' to use these available Modes for their exact design intent. BUT.

Secondly: The performance of the EQX is phenomenal........... but only with caveat/stipulation: Mitigation of EMI. Now if you are a person that runs your EQX at factory presets........ you may never run into EMI. , . , . , . then all of this may be a moot point. But...... if you always try to run your Sens above 21 ((where the performance is truly at))........ a new rule needs to be imposed: Start using Park Mode-1, Park Mode-2, Field Mode-1, Field Mode-2, Beach Mode-1, Beach Mode-2 as the primary tool in your toolbox ...to mitigate EMI. You will still need to perform Noise Cancel in EACH of any/all-of-the Modes. The rule-of-thumb is: If one particular Mode allows you to run Sens 2-points higher (or more) ....... over your Mode-of-choice........ you will need to forgo your Mode-of-choice.....and choose the Mode that presents the least EMI.

Example: (((Punishment & relinquishment of 'pride'))). I am an old silver dime hunter at heart (actually: silver Half Dime hunter). My stubbornness of pride (most times) prevents me from deviating from Park Mode-1......which is THE Mode that is most frequency-resonant to silver dimes. I WILL find the Noise Cancel channel in Park Mode-1 ....that presents the least EMI. , . , . , . , . , . , then adjust Sens accordingly....to allow for a hunt........in MY Mode-of-choice. (((Bad idea.............and proven: time-and-time again))). Nutshell example: At one particular site..... I was only able to run Sens on '20' in Park Mode-1.....after manually finding the best Noise Cancel channel. This site I had beat to death. Somewhat recently (about 2 months ago)...... I decided to hit the same site.,.,., but with different mindset. Sure enough..... Park Mode-1, Noise Cancel channel '-7' was best...... and (again) would only allow for a Sens setting of '20'. After about 15-minutes of experimenting........ I discovered Field Mode-2, Noise Cancel channel '+7'...... allowed Sens to run as high as '23'.......so I hunted in this configuration. About 35-minutes into the hunt....... I hit what appeared to be a possible silver dime signal. Weak, repeatable signal...... with nearly no coil airgap forgiveness. I was fairly certain I had a high conductor in the ground. In no hurry to dig it up...... I decided to play with the different Modes (and Noise Cancel) on this particular target. I immediately switched back to Park Mode-1, found the best Noise Cancel channel...........then painfully discovered .... the EQX would NOT detect this target! Neither would any of the other Modes......DUE TO EMI! I dug the target up. It was indeed a silver dime! (1962 Rosie). Just shy of 9" deep. ----Continuing to hunt in this configuration...... I found plenty of other targets that Park Mode-1, Sens 20...would not find. ------At one point (much later) in the hunt......some form of new EMI occurred........... then Beach Mode-1, with Sens on 21....became the best performer. (((Beach Mode-1 is nearly identical in performance to Park Mode-1.....in reference to deep high conductors))).
The only single frequency that seemed to express minimal EMI issues at this site....was 20-Khz. The silver dime could not be detected in this single-freq Mode.

SUMMATION: Utilize all of the Modes of the EQX as another form of NOISE CANCEL CHANNEL!!!! (((You have NO idea how inhibiting/violent EMI truly is!!!)))

Tom I love it when I see you have made a long post I know I'm getting ready to learn something! I know you have covered it in many other threads but when you are testing channels for EMI are you solely using a dime in a air test to see depth differences? When checking for how high you can take sensitivity are you using the same technique or are you going by audible interference also? My dirt is really hot most of my spots 4 and 5 bar on a t2, and I get a ton of ground feed back with anything over 14 or 15 sensitivity but I still run it hot and just deal with the noise

A very timely reminder. With new detector offerings being introduced this is a major issue to consider. It appears there is progress being made on EMI problems by some of the main players. Exciting times.

Chris

Gosh Pedlar........ If ONLY to have you simply test/try a Tarsacci in YOUR specific (bad) dirt...... and without any financial committal !!!
When I am analyzing/testing EMI (and the mitigation thereof)...... I DO use a clad dime for air-test deltas/differences. It is a true gauging methodology. BUT..... IN the dirt is just as critical. You can learn (painful) things like...... I'm air-testing a dime at 13" with current atmospheric conditions...... BUT....... this (unrecovered-----soon to be recovered) dime at 8" is just shy of detection at all.

Chris......true again.
Yes..... "What If"...... the top-end/top-price XP Deus-2 WAXES the mid-line/mid-priced Equinox! Then all (of my 'above') data......again, becomes a moot point! (I speculate .....this might be true). Right now...... calabash is our only source....,,,,,,,,that tests things in a fashion that most of us (on this particular forum) would do.......and articulates in no uncertain terms.

Pedlar mills Wrote:
-------------------------------------------------------
> Tom I love it when I see you have made a long post
> I know I'm getting ready to learn something!

+1

Tom right now of any detector out there including all the new ones the tarsacci is the one I would buy if I was able to buy one right now. Bad dirt is the one thing I'm not seeing talked about with the new detectors coming out and it is at the top of my list in importance

And as much as 'bad dirt' has been talked about....... the topic appears to be (deliberately) avoided. NOT conclusive; yet, has my 'concern'.

NASA-Tom Wrote:
-------------------------------------------------------


> Once again............ I'm still shocked that we are still: * Within the antiquated methodology of a lump-of-wire at the end of a stick...... to find buried objects.
>
> (((It's hard to think outside the box....... when you are imprisoned deeply within the interior of the (proverbial) box))).


Tom - What are the alternatives to a spool of wire on a stick?

As of right now....... not much. We are still incarcerated within the mindset of inductive-coupling........(via a coil)........for detection of metal. OLD TECHNOLOGY!!!

In 1908.....Henry Ford said: "What the hell are we doing....still using old, antiquated internal-combustion engines for propulsion". ---Guess where we still are today!?!? (((Although this might have something to do with [--power hungry dirty money--] politics, Rockefeller, Vanderbelt, OPEC....etc......))).

My only thought is......... If we are to STILL stay within the incarcerations/limitations of ElectroMagnetic energy (EM) for detection of metal:
We have already 'bent' the EM footprint of the energy with a DD coil (thus proving we CAN bend the EM footprint and still stay with the confines of a 'balanced field'); ......should we not further investigate bending the field into a more confined corridor (via a pair of 45-Deg angled 'director stacks' mounted above the outboard perimeter of the coil)?!

NASA-Tom Wrote:
-------------------------------------------------------
> I know that I have alluded to this before.....abou
> t the EQX; yet, it has become "primary"......and t
> o a huge extent.
>
> First: We know that (say) Park Mode-1 is designed
> for deep high conductors.......like silver coins.
> We also know that (say) Field Mode-2 is designed f
> or low conductors.........like the tiny paper-thin
> coins of old European.
> I have been 'trying' to use these available Modes
> for their exact design intent. BUT.
>
> Secondly: The performance of the EQX is phenomenal
> ........... but only with caveat/stipulation: Miti
> gation of EMI. Now if you are a person that runs y
> our EQX at factory presets........ you may never r
> un into EMI. , . , . , . then all of this may be a
> moot point. But...... if you always try to run you
> r Sens above 21 ((where the performance is truly a
> t))........ a new rule needs to be imposed: Start
> using Park Mode-1, Park Mode-2, Field Mode-1, Fiel
> d Mode-2, Beach Mode-1, Beach Mode-2 as the pri
> mary tool in your toolbox ...to mitigate EMI.
> You will still need to perform Noise Cancel in EAC
> H of any/all-of-the Modes. The rule-of-thumb is: I
> f one particular Mode allows you to run Sens 2-poi
> nts higher (or more) ....... over your Mode-of-cho
> ice........ you will need to forgo your Mode-of-ch
> oice.....and choose the Mode that presents the lea
> st EMI.
>
> Example: (((Punishment & relinquishment of 'pride'
> ))). I am an old silver dime hunter at heart (actu
> ally: silver Half Dime hunter). My stubbornness of
> pride (most times) prevents me from deviating from
> Park Mode-1......which is THE Mode that is most fr
> equency-resonant to silver dimes. I WILL find the
> Noise Cancel channel in Park Mode-1 ....that prese
> nts the least EMI. , . , . , . , . , . , then adju
> st Sens accordingly....to allow for a hunt........
> in MY Mode-of-choice. (((Bad idea.............and
> proven: time-and-time again))). Nutshell example:
> At one particular site..... I was only able to run
> Sens on '20' in Park Mode-1.....after manually fin
> ding the best Noise Cancel channel. This site I ha
> d beat to death. Somewhat recently (about 2 months
> ago)...... I decided to hit the same site.,.,., bu
> t with different mindset. Sure enough..... Park Mo
> de-1, Noise Cancel channel '-7' was best...... and
> (again) would only allow for a Sens setting of '20
> '. After about 15-minutes of experimenting........
> I discovered Field Mode-2, Noise Cancel channel '+
> 7'...... allowed Sens to run as high as '23'......
> .so I hunted in this configuration. About 35-minu
> tes into the hunt....... I hit what appeared to be
> a possible silver dime signal. Weak, repeatable si
> gnal...... with nearly no coil airgap forgiveness.
> I was fairly certain I had a high conductor in the
> ground. In no hurry to dig it up...... I decided t
> o play with the different Modes (and Noise Cancel)
> on this particular target. I immediately switched
> back to Park Mode-1, found the best Noise Cancel c
> hannel...........then painfully discovered .... th
> e EQX would NOT detect this target! Neither would
> any of the other Modes......DUE TO EMI! I dug the
> target up. It was indeed a silver dime! (1962 Rosi
> e). Just shy of 9" deep. ----Continuing to hunt
> in this configuration...... I found plenty of othe
> r targets that Park Mode-1, Sens 20...would not fi
> nd. ------At one point (much later) in the hunt.
> .....some form of new EMI occurred........... then
> Beach Mode-1, with Sens on 21....became the best p
> erformer. (((Beach Mode-1 is nearly identical in p
> erformance to Park Mode-1.....in reference to deep
> high conductors))).
> The only single frequency that seemed to express m
> inimal EMI issues at this site....was 20-Khz. The
> silver dime could not be detected in this single-f
> req Mode.
>
> SUMMATION: Utilize all of the Modes of the
> EQX as another form of NOISE CANCEL CHANNEL!!!! ((
> (You have NO idea how inhibiting/violent EMI truly
> is!!!)))


Tom D. it's interesting that, although their intent with the two Park and Field modes, are as per their documentation, weighted for high or low conductors, there are not only other applications for these modes but they may not per se work as advertised (which isn't necessarily a bad thing!). I've used the low conductor modes with great success in finding uber deep old silver in tough ground. It also does, as advertised, well on low conductors as the $1 gold coin I dug was a solid 7" deep target. Impressive for such a small target, but to it's credit it's a heavy target with a lot of mass for it's size. I have also found that the various modes between Park and Field can also highly enhance the audio response using one mode over another.

Great points on yet another application for the modes/frequencies to mitigate EMI. EMI plagues some sites to the point of unhuntable if you bring the wrong detector.

Nasa Tom' latest revelation is very timely for me as I am looking forward to my 1st SMF detector(NM Legend) I have no experience with the advantages or peculiarities that Multi IQ or similar processing brings to the field. The Mode descriptions, whether ML, NM or XP are to vague out of necessity. I'm counting on knowledgeable people giving their insight. In the meantime I have decided to just set up several custom program profiles in Park, Field & Beach that are identical to learn the new machine. It should be instructive and will be fun to learn.

Chris