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On my mind -- Random Thoughts

Posted by NASA-Tom 
Re: On my mind -- Random Thoughts
September 21, 2021 01:36AM
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 )))!!!
JCR
Re: On my mind -- Random Thoughts
September 21, 2021 02:22AM
NASA Tom Have you ever had enough change in EMI running a single frequency to salvage a site/trip?

Chris
Re: On my mind -- Random Thoughts
September 21, 2021 11:21PM
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).
JCR
Re: On my mind -- Random Thoughts
September 22, 2021 04:47PM
I'm ignorant on Pulse Induction machines. Are they normally as susceptible to EMI as VLF platforms?

Chris
Re: On my mind -- Random Thoughts
September 22, 2021 05:45PM
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.
Re: On my mind -- Random Thoughts
September 23, 2021 01:22AM
In general.... most PI's are a bit less sensitive to EMI.
Re: On my mind -- Random Thoughts
September 23, 2021 04:18AM
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?
Re: On my mind -- Random Thoughts
September 23, 2021 07:40PM
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.
Re: On my mind -- Random Thoughts
September 23, 2021 08:06PM
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.
JCR
Re: On my mind -- Random Thoughts
September 23, 2021 09:10PM
It seems we need to do some controlled testing.

Chris
Re: On my mind -- Random Thoughts
September 24, 2021 12:06PM
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.
Re: On my mind -- Random Thoughts
September 24, 2021 12:47PM
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.
Re: On my mind -- Random Thoughts
September 29, 2021 01:11AM
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! )))
Re: On my mind -- Random Thoughts
September 29, 2021 01:49PM
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.
Re: On my mind -- Random Thoughts
December 05, 2021 03:46PM
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' ))).
Re: On my mind -- Random Thoughts
December 05, 2021 04:37PM
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! )))
Re: On my mind -- Random Thoughts
December 05, 2021 06:25PM
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.
Re: On my mind -- Random Thoughts
December 06, 2021 12:50AM
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!
Re: On my mind -- Random Thoughts
December 06, 2021 02:56AM
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!
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