dd coil

I have a ? does a dd coils center bar the knife edge from front to the back of the coil get wider the deeper you detect. Reason being the nox with any recovery speed fast or slow well separate a tab from a dime at 1 to 2 inches if the tab is 3 inches from the dime same plane.in muti

But when you raise the detector to 4 or 5 inches it only shows the tab .There by telling me it see's both targets but only ids the tab.subey

subey.......the answer is mildly complicated. But......here goes:

When the coil is extremely close to the 2 targets under the coil........ there is a much higher propensity for the coil to 'saturate' on the target that is directly underneath the center beam of the DD coil. The unit will then ID this specific target ....that is nearly 'touching' (((the center beam of))) the coil. Even though the other target is also underneath the coil...... it is not in the EM footprint 'flooded' area of the coil ((the center beam)).........so........the signal-strength of the target that is NOT under the center beam of the coil...is strong; yet, no where near as strong ((signal-strength)) as the center target that is nearly 'touching' the center beam of the DD coil.

ONCE the coil is raised several inches above the ground (above the two closely placed targets)..............nearly all detectors will "composite-saturate" the two targets together.,.,.,.,. and report the two targets as one target. The ID should be a 'averaging' of the two differing conductivities......combined///.....collectively. {{{(((The only detector to NOT do this.......and CONTINUE to keep the targets 'separated'.... is...... the XP platforms)))}}}.
As you continue to raise the DD coil further away from the ground.......... the DD electromagnetic footprint: becomes more narrow. You can see/witness/tell this...... by raising the coil higher-and-higher ....as you continue to sweep the coil over a target.,.,.,.,., and you will audibly witness the detectors report to be shorter and shorter in audio length/duration. At the deepest of depths.......the footprint is VERY narrow.

SO why doesn't the nox separate these in muti it has the speed or is something else going on .Since the center bar gets smaller the deeper you go wouldn't it separate at depth better . sube

It has nothing to do with processing speed (Target Recovery Response speed); but/rather....... a different Operating System. ((Right now: XP proprietary)).
Yes.,.,.,.,., the deeper you go with a DD coil...... the better it separates. BUT....... the deeper you go....the more minerals and additional targets: impede!

Thanks for the reply Tom .subey

subey that might answer the request you sent me to try on the new Deus 2. I wonder how that will work in multi on the Deus 2?

I wonder how that will work in multi on the Deus 2?
That's what i want to know thanks calabasb .subey

Target separation vs distance from the coil is a matter of geometry plus magnetic curvature. With a dime and pull tab separated by 3" it is easy to get separate responses at close depths because only one target is in the peak response area at a time. And to help even more, the other target is in a hard curvature of the field and looks like an on-edge target, making it look weaker.

As the coil is raised, both targets are geometrically closer to being in the peak detection zone at the same time, plus the field curvature is more uniform. So separation gets harder, and the two targets begin to blend into a single composite target. Normally for a dime and a pull tab the composite response will be somewhere in between, maybe a zinc cent. In your case, it sounds like the dime response got weaker with distance faster than the pull tab response, so the composite response ended up being mostly pull tab.

A big thanks for the reply.So now that i know whats happening i have another ?.
Running the nox at 4 khz single frequency the dime rules and the pull-tab is weak there by giving the id of the dime.
So if we had a smf detector that had a range of frequency from 4khz to 8 khz in muti would this be a better set up for targeting higher conductors.
I know nickles and gold signals would be weak but in a park or fairgrounds i am not looking for red rocks (nickels) or gold .
So is it possibly to have a smf detector run at lower frequency.
And another ? what about a fast smf would that separate any better . subey

subey......... Yes...... 4-Khz is ideal for dimes. (And somewhat off-frequency for mid-conductor aluminum soda-tabs). This has TWO "pluses". There is GREATER attraction (resonant freq) to the dime............ and......................LESS attraction to the soda-tab. Summationally ....... a DOUBLE "plus" for your targeted intent. But........ running a single frequency has disadvantages: Worse ID-reliability at deeper depths. EMI susceptibility. Less (multi-freq comparator) ability to recognize-and-mitigate/cancel mineralization. Less ability to handle/generate better SNR (Signal-to-Noise-Ratio).

Running a lower 'group' of frequencies via SMF (Simultaneous Multi Frequency).........will indeed take away some of the exceptionally strong signal-strength of the solo 4-Khz signal. ""How much"" signal-strength reduction is determined by the 'weighted-factor' of each of the individual freq's.....in the group of SMF frequencies.
The unique thing is: Even though 4-Khz in some real-World applications....will acquire a dime to SLIGHTLY greater depths over SMF; . , . , . , . , . , . the overall real-World collective composite of all the advantages of SMF....... will WIN in most real-World scenarios. SMF can analyze......and 'rid'.....ground feedback, mineralization blowback........and other metallic particulate contaminants ........to a better degree than a single operating frequency.
SMF caveat = This is ALL contingent upon good/intelligent/proper engineering-application that SMF additionally affords.......over any single frequency. Just because you may have/run/use SMF...... does not mean that the design engineers 'applied' all of the ADDITIONAL attributes that SMF presents/affords.

The EQX is a VERY fast SMF Operating System (O.S.). ((( User-friendly/adjustable.... via Target Recovery Response speed adjustability ))). BUT......... once again.......... in our example/case.......... Target Recovery Response speed has nothing to do with your example. 'Speed' is not the answer. I have reported the following....several times on this forum; yet, it is worth repeating (in a very abbreviated fashion) ........to illustrate a textbook perfect example:
If you have a XP GMP.......do the following test = Electrically 'short' a Nickel and a Dime together. . . . . by compressing the two coins together...between your fingers. Allow the dime to hide BEHIND the Nickel. Then slide the Dime out from behind the Nickel....by about 50% (you can expose the Dime to a MUCH lessor degree....for your shocking discovery testing). Now wave these two coins back-and-forth---back-and-forth---back-and-forth in front of the XP GMP coil. It does NOT matter what distance you wave the coins....from the coil. If the XP is in 3-Tone...... you will hear BOTH targets report ..... in proper orientation........and in proper conductivity. , . , . , . , . , . even though BOTH coins are compressed/electrically shorted unto each other. ===== Once again...... microprocessor 'speed' has nearly NOTHING to do with this nirvana target separation. On the EQX..... changing your TRR will not fix this condition.

These are the type of posts I love reading!

((( BUT...... these are the type of posts that chase other people ....to the other forums!!! Too "geekey". Too technical! )))

Great thread, especially when the info comes from NASATom and Geotech. Thanks for taking the time. Much appreciated.

NASA-Tom --

The "geeky" and "technical" stuff is not available at the other forums. This forum is unique, and quite valuable for a few reasons in my opinion, including...

1. NOT CENSORED (largely because it is not "sponsored" and thus the purpose is not to "drive sales" but to allow honest, open dialogue)...

2. "ADVANCEMENT" of the hobby is the primary goal

3. The expert, technical, engineering-type information available is second to none...

These things may not appeal to all, but there are plenty of other places for folks to go, if it doesn't appeal to them. If the worst thing that goes on here, that might "drive a few folks away," is that the discussion is too "technical" at times, well...I think that's a much more "benign" thing than what usually drives folks away from other forums...

The expertise is why I COME to this forum, and I'm certain there are many others who do as well.

Thanks for all of the info you provide, and thanks, subey, for starting the thread.

Steve



Edited 1 time(s). Last edit at 11/22/2021 07:17PM by steveg.

What Steve said! I'm not interested in egos arguing over something that doesn't help me be a better detectorist.

Chris

JCR Wrote:
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> What Steve said! I'm not interested in egos arguin
> g over something that doesn't help me be a better
> detectorist.

Here, here! That was a great post, and give me geeky all day long. Over the years I’ve been a member here, I have learn tons from Tom’s posts and many other very knowledgeable and informative people, but I haven’t learned a thing from peeps arguing about what detector is better or what detector is junk. Not interested, I move on quickly.

Thanks Tom, for providing us a forum that really educates.

You're welcome Gary.

There is a bit of a price to pay.....(attributes/consequences) for the First Amendment.

I love this site!!!

We need more of these posts.

I try to ignore the noise of some of the chest thumpers. The stuff in these types of posts is the goods.



Edited 1 time(s). Last edit at 11/23/2021 02:38PM by dave_e.

One more ? do all targets that are under the coil that are not under the center bar of the coil skew the id of the machine.
Thanks for your reply. subey

I love the in-depth information provided by Tom and others in this forum. Thank you for that! I feel I always learn something by reading great posts like this one. I'll take geeky all day long.

-Kerry

subey Wrote:
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> One more ? do all targets that are under the coil that are not under the center bar of the coil skew
> the id of the machine.

Yes, and the effect will vary with depth.

Thanks Carl this is what i always thought but on another forum a member with 15000 post and seems to know everything told me no only what's under the center bar.
I have done my own test and what you say is true boy this never gets old 51 years detecting and so much to learn to up my game .subey

subey. Yes. Anything under the coil is "weighted-average" in.........in composite fashion. A large part of the "weighted" factor is: A target directly underneath the center beam of the coil is (db: UP///amp-gain: UP) much stronger; hence, more heavily weighted in the ID averaging. A target that is under the coil; yet, not underneath the center beam.... is (db-DOWN) substantially less/reduced signal-strength.......and is proportionately LESS weighted in the ID determinant factor. M-IQ in concert with proper algorithms (collectively).....is uncanny in its ability to correctly ID the target directly underneath the center beam of the coil.....in real dirt.........nearly completely ignoring other (slightly lessor signal-strength) targets that are also underneath the coil. , . , . , . , . , (and M-IQ could be technologically advanced.... yet, another generational notch).

We are indeed advancing....... just a bit slower than my aging arms/body like.