Help With Equinox Ground Noise

[Badger-NH]

The only time I get EMI is when running Multi near powerlines.  Rather than lower the Sensitivity and lose depth, I just switch to one of the single frequencies and that usually solves the problem.  I rarely go lower than 24 on my Sensitivity.

[Hardtimehermit]

Yes Jeff, very good post most of yours have helped me out with detecting in downtown Reno, and in general. 

happy swinging! ? ht

[Jeff McClendon]

2 hours ago, Badger-NH said:

The only time I get EMI is when running Multi near powerlines.  Rather than lower the Sensitivity and lose depth, I just switch to one of the single frequencies and that usually solves the problem.  I rarely go lower than 24 on my Sensitivity.

I would love to be in your situation. Even when I am in a remote area in my part of the world, most of the ground is so mineralized that running at 22 is about all my Equinoxes will do even with recovery speed adjustments. 

I have done a good bit of testing on in the ground targets and in my test garden, but all of that is in moderate to high mineralization, so my results are just my results and may not apply to you. Lowering sensitivity for example from 22 to 18 while in Multi to help alleviate EMI does not result in massive amounts of depth loss where I am. Changing to a single frequency that is not bothered too much by EMI and keeping my sensitivity at 22 doesn't result in the same depth capabilities as staying in Multi, in fact I lose depth capabilities and the enhanced ability to hit poorly oriented or partially masked targets. Also, target ID completely goes out the window here and all deeper non-ferrous targets give numerical and tone IDs from the mid 20s to high 30s or even 40. So discrimination is pointless and I have to dig everything or risk missing good targets. Again, those are just my results in pretty bad dirt and EMI. I will try to stay in Multi even with lowered sensitivity instead of changing to say 4khz or 20kHz and keeping sensitivity above 20.

Chuck, I did not notice an EMI stability improvement in Multi frequency after any of the upgrades. Adding a quiet 4kHz single frequency in the last upgrade is really great especially when I get the chance to detect on mild ground for deep high conductors. I do wonder what sort of filtering may be happening in 4kHz to help keep it quiet that might effect depth.

[GB_Amateur]

13 minutes ago, Jeff McClendon said:

Lowering sensitivity for example from 22 to 18 while in Multi to help alleviate EMI does not result in massive amounts of depth loss where I am.

(Sorry if I've asked this before, particularly if you've answered.)  Do you think this is because turning up the gain also amplifies the ground noise?  I've wondered if rather than these two effects being equally magnified, that turning up the gain (sometimes) actually increases the ground signal compared to the intended target signal.  Same question with iron targets (e.g. nails) relative to non-ferrous targets.   That's something I need to play with in my test setup when I get it cleaned (but waiting for warmer weather).

20 minutes ago, Jeff McClendon said:

Changing to a single frequency that is not bothered too much by EMI and keeping my sensitivity at 22 doesn't result in the same depth capabilities as staying in Multi, in fact I lose depth capabilities and the enhanced ability to hit poorly oriented or partially masked targets. Also, target ID completely goes out the window here and all deeper non-ferrous targets give numerical and tone IDs from the mid 20s to high 30s or even 40. So discrimination is pointless and I have to dig everything or risk missing good targets.

Sounds like my experiences but I'm pretty sure my soil is not as 'magntized' as yours -- only half scale on the Fishers.  Using the Equinox, for shallow(er) targets I can get away using single frequency and still get decent dTID's.  But most of my older coins fall below the cutoff where reliable dTID's get lost.

The park I've been detecting this past year is for the most part far enough from EMI that I can run gain of 24 quietly.  (There are exeptions.)  Still I haven't found a coin deeper than 8" or so.  I don't know if that's because there aren't any deeper coins (really doubt that), whether I'm just not getting the coil's deep sensitive zone over them, or possibly I'm getting to the limit the ferromagnetic ground components allow.  But this last point would seem to be inconsistent with the depths you've reached in likely much stronger mineralization.  Sounds like I need to experiment with lower gain....

 

[Jeff McClendon]

This is just my opinion. It may be born out of facts and experiences but I am definitely not an electrical engineer.

The ground itself and EMI are always targets, period.

For fixed single frequency detectors, the only ways to lessen the effects of ground noise (besides ground balancing) and EMI (besides noise reduction adjustments if the detector has that feature) are to lower the sensitivity and/or use a smaller DD coil. If you happen to be detecting with a single frequency detector operating at the wrong fixed frequency for EMI/ground mineralization conditions you may be screwed or you better have a different detector operating at a different frequency handy. For simultaneous multi frequency detectors that are also very high gain detectors like the Equinox, my statement holds twofold or threefold true depending on how many frequencies are being used. Multi IQ will get a great look from multiple perspectives at any detectable target which makes it potentially very accurate but also overly sensitive to all detectable targets including ground mineralization "fog" and "clouds" of EMi.

Lowering the sensitivity a bit using Multi may perform better on coin sized or larger deep targets if the Equinox is too chatty along with slightly adjusting the recovery speed if you have an 800. Also, the Park 1 or Field 1 vs Park 2 or Field 2 setups for deeper targets question is one I haven't been able to answer. I have found deep silver, copper, gold and deep V nickels past 12" in both 1 and 2 modes with sensitivity at 22 or less and recovery speeds that are still on default settings........?

For the absolute deepest detecting or for tiny stuff like micro jewelry and gold prospecting I use the Gold modes in Multi, rely on the target ID numbers and VCO tone aspects while adjusting recovery speed and sensitivity according to ground and EMI conditions.

[Badger-NH]

Going from 20 to 25 on Sensitivity gives me a gain of at least a half inch of depth for each increment.  I think all my single frequencies are deeper than Multi.

I relic hunt in Field 1 almost exclusively because it has shown to be deeper than Park 1.  I mostly use Multi for mineralized ground and iron and prefer the single frequencies for clean ground.

[Jeff McClendon]

Chuck (GB_amateur)

So, I forgot to pose this question which I don't know the answer to but which is at the heart of this discussion even though it is lurking in the background....

Are ground noise and EMI still a factor for target ID accuracy and especially depth, even when they seem to have been "silenced"?

 Is using the Equinox in Multi (which is the way the Equinox was designed to be used optimally according to Minelab with single frequency operation being for diagnostic or emergency use) the best solution for ground noise/mineralization whether silent or audible but not the best solution for bad EMI.

Your example of running at almost max sensitivity using the Equinox in low EMI but ground that is moderately mineralized according to your Fisher F75 makes me wonder.

[Badger-NH]

I've always thought EMI was just noise and that it had no effect on target depth.  I suppose it might interfere with target ID.

[Jeff McClendon]

 

13 minutes ago, Badger-NH said:

I've always thought EMI was just noise and that it had no effect on target depth.  I suppose it might interfere with target ID.

The ground and any physical object may have a dampening effect on EMI but distance from the source to me is more important. A sensitive detector can pick up EMI from buried power and communication lines and from buried wireless transmitters. Plus, the top of the search coil is almost always exposed to any EMI in the area. So, I am not certain whether EMI can effect actual depth or not. Until someone proves to me that EMI has no effect on actual depth (whether I lower sensitivity or not to deal with it in really mild ground for instance), I will leave that as an open question.