Emi Revisit

[midalake]

So for you experts on EMI interference.  Does EMI effect the powerhead?, coil? or both????   Thanks. 

[GB_Amateur]

Is this an anology:  does the wind affect the sail, the hull, or both?  I think the answer to both questions is the same -- stronger effect on the sail but under certain circumstances (e.g the sail is furled) then the effect on the hull is noticeable.

OK, the analogy isn't quite perfect, because who would ever (intentionally) operate a metal detector with the coil detached?  However there have been situations here where people have reported interference when an electronic device is close the to control head but moving it away even a small distance improves things.

As a side note, IMO there is a risk in asking for expert answers.  Define 'expert'.  If you leave it up to the individual then you will drive away people who are expert but also modest while at the same time keeping those who aren't expert but have unrealistic egos.  In my case, for another analogy I (mis-)quote the old Holiday Inn Express commercial:  "I'm not an expert, but I did read detectorprospector.com last night." 

[CPT_GhostLight]

I'm no expert by any stretch of the imagination, but I have some experience with electromagnetic fields and interference. EMI has the potential to affect any electronic device. We live in a virtual soup of constant and intermittent EMF sources so electronic devices are being bombarded by EMI while emitting it as well. This is why electronics manufacturers go to great lengths to mitigate EMI into and produced by their devices.

Without going too far down this rabbit hole, the short answer is yes both control box and coil and even the cable of metal detectors are all susceptible to EMI. The cable is shielded and control box uses electronic EMI control, so they are less susceptible to EMI disruption, but the coil is a giant electromagnetic antenna so it is the most affected by EMI.

HTH

[Tom Slick]

EMI can, and does affect both the control box and the coil. Some companies do a better job of eliminating or reducing the effects of EMI on their detectors but most detectors (if not all) still suffer the consequences of EMI .

[Badger-NH]

Reducing the effects of EMI might detract from the performance of the detector as we've seen with the various F-75 and T-2 models. The models with DST (Digital Shield Technology) are less affected by EMI while the models without DST are noticeably deeper.

[GB_Amateur]

17 minutes ago, Badger-NH said:

Reducing the effects of EMI might detract from the performance of the detector as we've seen with the various F-75 and T-2 models. The models with DST (Digital Shield Technology) are less affected by EMI while the models without DST are noticeably deeper.

I can turn off DST on my Fisher F75 Black ('Limited') w/DST.  In that case do I restore the depth/sensitivity loss back to the pre-DST version?  Yes, First Texas is the right place to direct this question.  I just bring it up because I don't think it's as simple as F75 model without DST being more sensitive/deeper than F75 model with the DST option.  But if there is evidence that my and similar units (with DST that can be toggled on/off) go deeper with DST off than when it's on, that would be support for your claim of shielding reducing sensitivity/depth.  I'm pretty sure some have said that's true and maybe it's convincing enough to seal the conclusion.  I've not looked into it myself (neither in testing nor in researching YouTube, etc.).  And even though I've read the manual several times, all I remember it saying there is that the user has the option of turning it off.  I don't remember it saying "to get more depth...".

[Badger-NH]

2 hours ago, GB_Amateur said:

I can turn off DST on my Fisher F75 Black ('Limited') w/DST.  In that case do I restore the depth/sensitivity loss back to the pre-DST version?  Yes, First Texas is the right place to direct this question.  I just bring it up because I don't think it's as simple as F75 model without DST being more sensitive/deeper than F75 model with the DST option.  But if there is evidence that my and similar units (with DST that can be toggled on/off) go deeper with DST off than when it's on, that would be support for your claim of shielding reducing sensitivity/depth.  I'm pretty sure some have said that's true and maybe it's convincing enough to seal the conclusion.  I've not looked into it myself (neither in testing nor in researching YouTube, etc.).  And even though I've read the manual several times, all I remember it saying there is that the user has the option of turning it off.  I don't remember it saying "to get more depth...".

 

As far as I know, you can't have it both ways. By adding DST to the machine, you lose the performance of a non-DST machine. I have both the F-75 LDT DST and the T2 SE non-DST. The T2 is much hotter and gets nearly an inch more depth on a dime. They say the same thing about the original F-75.

 

[GB_Amateur]

3 minutes ago, Badger-NH said:

 

As far as I know, you can't have it both ways. By adding DST to the machine, you lose the performance of a non-DST machine. I have both the F-75 LDT DST and the T2 SE non-DST. The T2 is much hotter and gets nearly an inch more depth. They say the same thing the original F-75.

That's certainly evidence and thanks for providing it.  One thing, though, is that so far you are comparing two different detectors even though they have a lot of DNA in common.  Better evidence would be F75 pre-DST model vs. F75 later version which was labeled 'DST', which I realize is a comparison you aren't in position to make.  Also something I didn't see in your posts is whether you've looked for depth differences for your F75 with DST engaged and with it disengaged.  I confess I've never tried that; in fact I've always just operated with DST engaged.

Unfortunately (to some extent) for me I came along after all this was hot news in the forums.  I do recall some mention of it here previously, but that mention included some skepticism as well, if I remember correctly.  Maybe our forum here wasn't even around when all this was the hot topic.  Although I'm pretty adamant in following this site, the others I only touch when I'm researching a particluar topic (e.g. how a particular brand's coil I'm interested in performs on a particular detector) or someone here links to an interesting thread.

 

[Badger-NH]

13 minutes ago, GB_Amateur said:

That's certainly evidence and thanks for providing it.  One thing, though, is that so far you are comparing two different detectors even though they have a lot of DNA in common.  Better evidence would be F75 pre-DST model vs. F75 later version which was labeled 'DST', which I realize is a comparison you aren't in position to make.  Also something I didn't see in your posts is whether you've looked for depth differences for your F75 with DST engaged and with it disengaged.  I confess I've never tried that; in fact I've always just operated with DST engaged.

Unfortunately (to some extent) for me I came along after all this was hot news in the forums.  I do recall some mention of it here previously, but that mention included some skepticism as well, if I remember correctly.  Maybe our forum here wasn't even around when all this was the hot topic.  Although I'm pretty adamant in following this site, the others I only touch when I'm researching a particluar topic (e.g. how a particular brand's coil I'm interested in performs on a particular detector) or someone here links to an interesting thread.

 

Yes, I depth tested it both ways with DST on and off, and saw no difference in performance. In fact, I saw little if any difference in EMI either, so I ran mine with DST off most of the time. I think I read somewhere that the difference between on and off was very small. Lots of F-75/T2 info if you search Tom Dankowski's site.

 

[midalake]

8 hours ago, Tom Slick said:

EMI can, and does affect both the control box and the coil.

 

4 hours ago, GB_Amateur said:

That's certainly evidence and thanks for providing it.

 

4 hours ago, Badger-NH said:

s far as I know, you can't have it both ways.

I guess the reason is:  Has anyone tried an EMI Bag over their detector or one of the multiple EMI reducing products on the coil?