A question about EMI and cable shielding.

Here's a question and I am curious if this would help EMI. Would putting a a coating of heat shrink or electrical tape on the entire coil wire cut down on EMI? I'm brainstorming and I got this idea stuck in my head and I'm wondering if this would work. Tell me what you guys think or if any of you have tried this.

Hi,,,I have never tried this but know it would not work....To provide the type/form of shielding you are asking about it would have to be made of metal or a metallic compound...Most EMI is not usually introduced through the wire itself because of the already adequate shielding provided on the wires that they use..........JJ



Edited 1 time(s). Last edit at 04/08/2015 03:37PM by jimmyjiver.

EMI is frequency. It can be many frequencies. Frequency can penetrate things like tape, paper, even brick etc. Try this experiment, wrap a coin in electrical tape, drop it on the ground and sweep with your detector. See if the coin is picked up????? And different frequencies depending on the frequency and power penetrate much more than others. I.E microwave ovens. You coil cable is shielded to minimize/prevent this penetration of unwanted frequencies. Your coil though can act like an antenna for these unwanted frequencies. And with the higher sense levels metal detectors possess/are capable of, these nuisance frequency(s) detected causes things like noise, loss of detection depth, etc.



Edited 1 time(s). Last edit at 04/08/2015 02:18PM by tnsharpshooter.

This is more typical way to Suppress EMI: [www.alliedelec.com]

The problem is it really is not working in the frequency range needed to suppress the noise that affects our Detectors. Out systems work in the Khz range not Mhz range. So power lines, Ballasts used for florescent lights, Older cordless phones, Some Garage door openers tend to be more of an issue then other forms of noise. We are most times affected by Harmonics of a lower frequency. Plus the biggest noise receptor is the coil which we want to be receptive to those frequencies. So noise Suppression has to happen inside the box not outside.

Bryanna - Nebraska

Current - New to me but not new MXT Pro and T2 SE2 - Previous Minelab Sovereign GT, Minelab Safari, Whites DFX, Whites Eagle Spectrum
Smile its a good for you!

99.99999% (made up figure) of emi is being received by your coil its self not the cable. EMI is typically proportional to Rx coil size.

EMI could be coming from anywhere into the machine at some vulnerable point..

COIL?
CABLE?
CONTROL BOX?

doubt its the cable..

probably the coil but dont discount the control box either..

I had a problem once with a Fisher I.D. EDGE ..it would go crazy occasionally and would not settle down...it would happen out of nowhere and anywhere..


I found the culprit to be a capacitor on the circuit board next to the coil connector...You could just get your hand withing 3 inches of it around the outside of the box and the machine would go into high tone beeping...

I built a alumimum box insert out of 1/16" aluminum on my metal break and inserted it into the control box it fit snuggly inside..The but all electronics back in and never hea danother problem wiht erratic behavior...I ende dup doing quite afew EDGE boxes for people and no one ever complained about erratic noisy behaviro again...

on a side note it took the solid aluminum to stop the noise...aluminum tape and foil and such did not do it.. the actual thicker aluminum solved the problem..

I told the factory about it back then but they did not make any changes..Heck they were bought out shortly after that and the EDGE ceased to exist..

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

Hi 88 Junior,

No, probably not much can be done by simply wrapping the cable in something else?

After years of making coils and experimenting with different cables, about the only thing you 'could do' is, to wire in a series of "ferrites" and best placed at the coil connector area.

Well I guess my brainstorming was a failure this time. I wonder what First Texas done exactly to combat the EMI problems to the F-75 & T2 to get rid of the EMI in the new DST.

I don't know but it works. My F75LTD2 is now my quietest running machine running wide open using Disc and AM.

This is more typical way to Suppress EMI: [www.alliedelec.com]

The problem is it really is not working in the frequency range needed to suppress the noise that affects our Detectors. Out systems work in the Khz range not Mhz range. So power lines, Ballasts used for florescent lights, Older cordless phones, Some Garage door openers tend to be more of an issue then other forms of noise. We are most times affected by Harmonics of a lower frequency. Plus the biggest noise receptor is the coil which we want to be receptive to those frequencies. So noise Suppression has to happen inside the box not outside.

Bryanna - Nebraska

Current - New to me but not new MXT Pro and T2 SE2 - Previous Minelab Sovereign GT, Minelab Safari, Whites DFX, Whites Eagle Spectrum
Smile its a good for you!

Keith, Sounds like you built a nice box to shield the electronics. The more modern the design the better they are at Noise suppression. Noise was not as big a deal 40 years ago - well it was just not as many sources of noise so it did not get as much attention. Now noise suppression is designed into the circuit boards. And this before they do any active noise suppression. What ever First Texas did with the F75 and T2 works But sounds like the Racer and CoRe are both pretty well designed as well. My Minelabs always seemed able to find a quite channel and where not too bothered by noise unless you got crazy on the gain. MXT does OK the noise is there but it is not a problem. Coils do make a difference and the T2 and F75 do see more noise with the larger coil. I would assume most detectors are the same way - bigger antenna (coil) = more EMI problems.

Bryanna - Nebraska

Current - New to me but not new MXT Pro and T2 SE2 - Previous Minelab Sovereign GT, Minelab Safari, Whites DFX, Whites Eagle Spectrum
Smile its a good for you!

I think FTP over the last few years worked on ways to SHIELD the coil more than orignal design concepts had....

And at the same time I believe the signal now is way more processed through how should I say a D.S.P. unit...the signal is cleaned up and also any remaining noise is audibly removed in the end..this can be sensed in that the unit is more slightly latent and slightly less depth and less spark to the audio report...

the hyper feel is almost gone...

A machine like a DEUS or GMP or even the newly released Racer is way more quiet than the old F75 or T2 but they still have the hyper feel and some spark..

the F75 seems overly processed at times...

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

I have seen a few comparison videos between the Old F75 and New F75 and can not notice any loss of Sparkyness. But my guess is the tests did not real highlight that very well. Depth seemed the same as well. I am still debating on the T2 vs F75 in theory the F75 should be a bit hotter - but I am not really seeing it. Could be my T2 is one of the better ones. I expected to find the F75 better in all ways but not so - but that is another post.

On noise issues I think you are correct in that the noise is being masked and filtered both using DSP. In most of the comparisons I have seen working depth is about the same and the absence of noise means more find in areas that before where way too noisy on the old F75/T2 at least that is what is being reported - since I have never swung a T2 or F75 without DST onboard I have nothing to compare with.

Seem to remember someone saying they could not use the Racer at one location because of noise. Would of been interesting to see how the F75/T2 did in the same noise environment.

Keith Southern Wrote:
-------------------------------------------------------
> I think FTP over the last few years worked on ways
> to SHIELD the coil more than orignal design
> concepts had....
>
> And at the same time I believe the signal now is
> way more processed through how should I say a
> D.S.P. unit...the signal is cleaned up and also
> any remaining noise is audibly removed in the
> end..this can be sensed in that the unit is more
> slightly latent and slightly less depth and less
> spark to the audio report...
>
> the hyper feel is almost gone...
>
> A machine like a DEUS or GMP or even the newly
> released Racer is way more quiet than the old F75
> or T2 but they still have the hyper feel and some
> spark..
>
> the F75 seems overly processed at times...
>
> Keith

Bryanna - Nebraska

Current - New to me but not new MXT Pro and T2 SE2 - Previous Minelab Sovereign GT, Minelab Safari, Whites DFX, Whites Eagle Spectrum
Smile its a good for you!

"Times They Are A Changing"

Comes to mind..


Noise gone from the Hyper gain units...yet still very powerful..

Less intricate setttings to adjust for world classs performance results in iron unmasking..


No telling what's next...

Im having to adjust as I go here lately...almost having to force myself on how to accept what should not be..


Yes>>>>>>> "Times They Are A Changing"

Bob Dylan knew it 50 years ago LOL!!!

Keith

“I don't care that they stole my idea . . I care that they don't have any of their own”
-Nikola Tesla

I love that song! Yes the times they are a changing

Keith Southern Wrote:
-------------------------------------------------------
> "Times They Are A Changing"
>
> Comes to mind..
>
>
> Noise gone from the Hyper gain units...yet still
> very powerful..
>
> Less intricate setttings to adjust for world
> classs performance results in iron unmasking..
>
>
> No telling what's next...
>
> Im having to adjust as I go here lately...almost
> having to force myself on how to accept what
> should not be..
>
>
> Yes>>>>>>> "Times They Are A Changing"
>
> Bob Dylan knew it 50 years ago LOL!!!
>
> Keith

Bryanna - Nebraska

Current - New to me but not new MXT Pro and T2 SE2 - Previous Minelab Sovereign GT, Minelab Safari, Whites DFX, Whites Eagle Spectrum
Smile its a good for you!

Keith Southern Wrote:
-------------------------------------------------------

> I told the factory about it back then but they did
> not make any changes..Heck they were bought out
> shortly after that and the EDGE ceased to exist..

See what happens to companies that don't listen to Keith!

Pleasant Garden, NC
AT Max, Nokta Impact, MX Sport, Nokta FORS Relic, GPX 4800, Infinium, Racer, Deus, F75SE, Nautilus DMC II (order of acquisition, last to first)

Does an archeologist argue with a plow? A bureaucrat with a bulldozer?



Edited 1 time(s). Last edit at 04/09/2015 02:35PM by ncwayne.