On my mind -- Random Thoughts

steveg....... absolutely! I use a clad dime to check the air-test results between 2 (or more) silent Noise Cancel Channels. So far..... it is the only way to differentiate between the two silent Noise Cancel Channels. One problem that I have run into is......... I have seen/witnessed/experienced one 'quiet' Noise Cancel Channel......"change" performance (somewhere in mid-stream) to give the performance lead to the OTHER quiet Noise Cancel Channel.........unsuspectingly. The only way to find out is..... to perform another air-test (sometimes every 10-minutes)!
Many times a site has audible EMI on EVERY Noise Cancel Channel...... making it more 'audibly easy' to delineate/differentiate "which" channel presents the best mitigation.

Chris...... in most cases ...... that is true. When you are running multiple frequencies...... you have multiple chances to catch EMI. ((( It is not uncommon for me to try all the different Modes......ie: Beach Mode, Field Mode, Park Mode....... to see if THAT can fix a EMI plagued site. Especially if I have a 4-hour round-trip time vested )))!!!

NASA Tom Have you ever had enough change in EMI running a single frequency to salvage a site/trip?

Chris

Chris...... yes. Crazy thing is....... on 2 occasions...... ONLY 40-KHz worked. That's my last choice for the intended copper/silver coin hunt. But...... it (somewhat) kept me in-the-game. I did not have a CZ (or other brand) with me. Just a EQX......and my backup EQX. (((Made me re-think my operating procedure).

I'm ignorant on Pulse Induction machines. Are they normally as susceptible to EMI as VLF platforms?

Chris

I don't remember my TDI or Infinium being all that susceptible to EMI. But my GPX is definitely more susceptible that my Equinox to EMI.

In general.... most PI's are a bit less sensitive to EMI.

Years ago, I recall that some detectorists warned us about EMI from cell phones.
"Leave your cell phone in the car," they would say.

I haven't noticed any obvious EMI while carrying my iPhone 11 and using my
Tarsacci MDT 8000 or Nokta/Makro Multi Kruzer. Of course, if it's silent EMI,
I would have difficulty noticing.

Are modern cell phones less likely to cause EMI, or are we all suffering silently?
And are certain detecting frequencies more/less prone to cell phone EMI?

TallTom Wrote:
-------------------------------------------------------
> Years ago, I recall that some detectorists warned
> us about EMI from cell phones.
> "Leave your cell phone in the car," they would say
> .
>
> I haven't noticed any obvious EMI while carrying m
> y iPhone 11 and using my
> Tarsacci MDT 8000 or Nokta/Makro Multi Kruzer. Of
> course, if it's silent EMI,
> I would have difficulty noticing.
>
> Are modern cell phones less likely to cause EMI, o
> r are we all suffering silently?
> And are certain detecting frequencies more/less pr
> one to cell phone EMI?

That's a great question, Tom! I have similarly not noticed any negative effects from my phone with respect to audible EMI, so I have (somewhat sloppily) assumed that it's probably not a big issue. BUT -- since I ALWAYS have my phone with me, and have never done any explicit silent EMI testing with my machine/phone (i.e. checking performance with the phone turned off, vs. with it turned on), I really DON'T know for sure if silent EMI related to the phone, may be affecting my performance or not...

Steve



Edited 1 time(s). Last edit at 09/23/2021 07:41PM by steveg.

There is a higher propensity of silent EMI with cell phones (vs detector)....... as compared to obvious audible EMI. I DO notice that when my cellphone rings....... THEN it produces audible EMI on the detector. Sooooooo....... I choose to keep my cellphone in the car whilst detecting.

It seems we need to do some controlled testing.

Chris

There's a fair amount of 'variables' .... that would need to be made: 'constant(s)'...... in order for this test to retain validity. But............. I believe it could be done.,.,.,.,.,. with proper logistical configuration.

does atmospheric EMI (any or all types) have an effect on targets in the ground and/or mineralization (regardless of a detector) or does it just mess with reception? .. and if it does effect the targets/mineralization .. has the effect been measured .. or defined?

it would seem that if 20 people sitting in a coffee shop can send and receive data to and from anywhere, with little or no effect from those around them, including their surroundings .. that in a similar fashion a single transmitter/receiver could do the same in the relatively small cylinder

if you had a detector that could tell you with 90% certainty that the target 30 inches below its coil was a 1797 US dime .. would you dig it? .. what if it was 40 inches, or more .. or 75% or less? .. or an 1838 dime .. where is your cut off?
random thoughts this morning.

What is of concern is........ EMI (of nearly any type/source)..... hampers the receive signal of any detector. Analogy: If a radio is playing softly in a room...... you may only miss the conversation(s) of the folks that are whispering in the room. If the radio is playing at a medium volume level..... you will miss hearing folks that are talking in a normal tone of voice. If the radio is playing loudly....... you will miss all conversations. Yes......... it affects the transmitting (talkers)...,,,,,......,,,,,,......,,,,,,,....... but you are only concerned about receiving their voices in your ears.

((( I would gladly dig 40" for a 1797 dime!!! And that's what archaeologists do! )))

TallTom Wrote:
-------------------------------------------------------
> Years ago, I recall that some detectorists warned
> us about EMI from cell phones.
> "Leave your cell phone in the car," they would say
> .
>
> I haven't noticed any obvious EMI while carrying m
> y iPhone 11 and using my
> Tarsacci MDT 8000 or Nokta/Makro Multi Kruzer. Of
> course, if it's silent EMI,
> I would have difficulty noticing.
>
> Are modern cell phones less likely to cause EMI, o
> r are we all suffering silently?
> And are certain detecting frequencies more/less pr
> one to cell phone EMI?

I have lots of experience with cell phones since everyone at the main beach seems to be carrying a $$^%$&# Cell Phone.
First, cell phones can have a horrible effect on detection.
MDT- Did not see any noticeable cell interference. Only about 70 hours on the machine. Did not make any connection to silent EMI either.
Equinox, a disaster around cell phones. I made a custom tinfoil surround of the pod, which does a good job of reduction. I would say about 90%. Now there has to be 4-5 people watching me will cell phones to cause issues. I would say without question the Equinox has silent EMI Issues. Both with Cell Phones and Communication equipment.
I suggest with beach hunting and many cell phones to stay away and go slower until the cell phones are out of range. 30 feet away, or so.
I have not tried to noise cancel cell phones, as the issue is tempoary.

I (really) need D.E.'s & C.D.E.'s to think about something:

A coil is 2-dimensional (X-Y)
The dirt we search is 3-dimensional (X-Y-Z)

((( I want to expound more ....but...... it would 'lead' and 'mislead' ))).

TomD - Thank you for the analogy! Now I understand in more detail how EMI cripples performance.
Cellphones question: if I have my phone on me, can performance of the detector suffer effects of EMI even if my cellphone is in airplane mode or completely shut off ?


NASA-Tom Wrote:
-------------------------------------------------------
> What is of concern is........ EMI (of nearly any t
> ype/source)..... hampers the receive signal of any
> detector. Analogy: If a radio is playing softly in
> a room...... you may only miss the conversation(s)
> of the folks that are whispering in the room. If t
> he radio is playing at a medium volume level.....
> you will miss hearing folks that are talking in a
> normal tone of voice. If the radio is playing loud
> ly....... you will miss all conversations. Yes...
> ...... it affects the transmitting (talkers)...,,,
> ,,......,,,,,,......,,,,,,,....... but you are onl
> y concerned about receiving their voices in your e
> ars.
>
> ((( I would gladly dig 40" for a 1797 dime!!! And
> that's what archaeologists do! )))

EPL II Wrote:
-------------------------------------------------------
> TomD - Thank you for the analogy! Now I understand
> in more detail how EMI cripples performance.
> Cellphones question: if I have my phone on me, can
> performance of the detector suffer effects of EMI
> even if my cellphone is in airplane mode or comple
> tely shut off ?
>
>
> NASA-Tom Wrote:
> --------------------------------------------------
> -----
> > What is of concern is........ EMI (of nearly any
> t
> > ype/source)..... hampers the receive signal of a
> ny
> > detector. Analogy: If a radio is playing softly
> in
> > a room...... you may only miss the conversation(
> s)
> > of the folks that are whispering in the room. If
> t
> > he radio is playing at a medium volume level....
> .
> > you will miss hearing folks that are talking in
> a
> > normal tone of voice. If the radio is playing lo
> ud
> > ly....... you will miss all conversations. Yes.
> ..
> > ...... it affects the transmitting (talkers)...,
> ,,
> > ,,......,,,,,,......,,,,,,,....... but you are o
> nl
> > y concerned about receiving their voices in your
> e
> > ars.
> >
> > ((( I would gladly dig 40" for a 1797 dime!!! A
> nd
> > that's what archaeologists do! )))


Airplane mode allows WIFi so mainly 2.4GHz and 5GHz so it could still interfere in theory.

When your cellphone is 'off'........ should be zero interference.
When cellphone is in 'airplane' mode......... should interfere very little/minimal.
When cellphone is 'on'.......... and functioning normally; yes. And can also induce 'silent' EMI. BE CAREFUL!

After reading this post, I will be shutting off my phone. Once again I thank you for your guidance. - Jim


NASA-Tom Wrote:
-------------------------------------------------------
> When your cellphone is 'off'........ should be zer
> o interference.
> When cellphone is in 'airplane' mode......... shou
> ld interfere very little/minimal.
> When cellphone is 'on'.......... and functioning n
> ormally; yes. And can also induce 'silent' EMI. BE
> CAREFUL!

I have alluded to this before; yet, as-of-recent......... it is in the forefront again:

EVERY increment of EMI mitigation is what will add: performance, depth, enhanced/accurate ID's and stability............................for the foreseeable technologically-advancing future of ANY/ALL Mfr's.

ONCE we mitigate/rid EMI............. the focus will be:
Every 4% decrease in sensitivity to iron.......will present a full "Generation-Gap" from current technology (and competitors).

Remember: Aluminum is in a LOT of old home sites. Iron is in ALL old home sites.

It is encouraging to know these things are being actively addressed and not just accepted as is.

Chris

NASA-Tom,

Very interesting. I'm surprised that in your list of improvements that EMI mitigation could bring, you included "enhanced/accurate IDs." The others make sense, but it seems a very "tall challenge" in this age of wireless/cellular...

Now, the decrease in sensitivity to iron is obvious, in terms of what a huge improvement that would be, but there again, a very "tall order," I would think. Just thinking about the improved unmasking, AND (hopefully) a decreased propensity for high-tone "falses" off of nails -- particularly square nails...what a welcome improvement it would be to have a machine "desensitized" to iron, even to some rather small degree.

Steve

Tom,

Have you seen the EMI preview screen on the Rutus Atrex?

You move through your frequencies while watching the graph to see where the least amount of emi is occurring.

What are your thoughts on it?

Chris: I look at it as: Opportunity to excel.........AND: Technological advancement.

steveg: Probably the best way for me to explain it is: If EMI presents a 40% signal-strength........ and a given target presents a 45% signal-strength............. ,,,,,,,,,,, ............ Effectively.....the detector only has a 5% delta/difference to try to ascertain a ID. (((And...... EMI ...ALSO generates its own form of a ID))).

dave_e: No ...... I have not! But it sounds VERY intriguing!!! It would be a tool that could REALLY help aid in: correct Noise Cancel channel(s).

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

As far as iron mitigation/reduction.,.,.,.,.,.,.,., there's several methodologies that can/could be employed............to include: collectively. All of them require 'engineering controls' =
Selecting a Operating Frequency(s)............ is the old-fashioned (yet, somewhat effective) way.
Time-Domain (timed-out) ......... is another method. (Cannot expound upon this......at present time. Maybe later).
Algebraic/Algorithm(s) that more-so "enhance/emphasize" the non-ferrous component....of a ferrous + non-ferrous co-locate. , . , . , . , . , . , . even if the ferrous signal is stronger (but not at saturation).
Amplify non-ferrous phase-shift..........whilst employing counter-productive (retardation of) ferrous magnetic-lines-of-flux shunt coil-winding technology. (((Windings that are out-of-phase of the magnetic lines-of-flux))).

Out of time!

NASA-Tom,

Makes sense on the VDI.

The time-domain way of dealing with iron, is very interesting, but for my purposes, you'd have to have a machine that essentially does both PI and VLF simultaneously, AND -- importantly -- with the VLF side of the house offering VDI accuracy at depth at least up to the Multi-IQ/FBS standard. If that could all be done, in one unit...OH MY...

Meanwhile, your "amplify non-ferrous phase-shift" in conjunction with "coil windings out-of-phase with magnetic lines of flux" sound VERY intriguing...as it sounds like this approach would look to minimize the "magnetic" problem (which I believe is what makes iron "harder for a detector to deal with" than other metals, yes?)

Steve



Edited 2 time(s). Last edit at 04/07/2022 05:59PM by steveg.

NASA-Tom,

Forgive me if this has been covered before but it seems that the current discussion is with cellphones producing EMI and silent EMI. My question is "Do you get the same EMI and silent EMI from an Apple Watch"? I have never noticed any EMI from mine but never thought about the silent EMI. I receive calls on mine at times on the beach with my Equinox. It seems not to bother it but...what about silent EMI???

Joe

“Never approach a bull from the front, a horse from the rear or a fool from any direction.”

steveg........yes, the 'magnetic' component of iron is certainly one of the inhibitors of ElectroMagnetic energy emanating from the source (the coil).

Joe......... my previous mindset about detectors & cell-phones has always been: they both operate on entirely different spectrums of frequency. A night-and-day difference in their operating frequencies...............sooooooooo............... how could they even interfere with one-another. UNTIL........ I had a Fisher F75 "light-off" on me...... the split second that my cellphone rang. And THIS was the 'beginner' of my EMI/Silent-EMI studies with cellphones ....vs....detectors. Yes....... a Apple watch is a Bluetooth and RF emanating source; hence, can cause EMI and/or Silent EMI.

Also........................ and I don't believe I have ever stated this for the record: You can have audible EMI that reduces performance of a detector......... AND ............ SILENT EMI ON TOP OF........ EMI. BOTH. Which (in turn) would reduce performance; yet, another notch lower.

On my mind........again:
Today's current technology/metal detectors work on two generations of advancement. What if a third advancement were to be invented/implemented:

1. Detection of metal.......via the disruption of a 'balanced EM field'. (Present)
2. Conductivity of metal...via 'phase shift' of signal. (Present)
3. Density of metal...........via preamble & postamble sharpness/harshness of signal. (Future)

Density of metal, aluminum is very low and gold very high. It would be a very accurate metal detector. Would it need a new detector technology to do that.

VLF detectors are based on magnetic and conductive properties. Is it possible to add density of metal to a vlf?

So Tom you need to develop a new metal detector based on density of metal and you would be very rich man.

Density -- if it could somehow be hinted at by a machine -- would be a HUGE advancement, even if initially only "rudimentary" in effectiveness. That said, I would prefer the "output" (lower density vs. higher density) to be NOT ONLY audible, but also some type of "on-screen/visual" type of output. I can envision hunting a park, where can slaw, pull tabs, ring pulls etc. abound -- i.e. parks where I don't often even bother trying to dig "mid tones" due to the "trash-to-treasure" ratio being so poor. BUT -- if I had "visual" analysis tools, specifically focused on the "density" aspect, I could see stopping to more thoroughly interrogate and examine MANY more "mid-tone" signals in park/turf-type sites than I currently do, as such visual display output would offer a tool specifically focused on improving that "trash-to-treasure" ratio. I have heard anecdotes (unsure how accurate) where some V3i users learned, over time, to be able to utilize visual/on-screen output from the various xmit frequencies to their advantage, in this regard (i.e. gaining hints as to which mid conductors might be more "diggable" than others, in a gold-ring-hunting application).

Steve