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Emi Frustration


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I've had my Eqx 800 for over 16 months and have operated it in the field over 300 hours.  I have all three coils though usually swing the stock 11".  Mostly I run in Park 1 but have experimented with all other modes.  I've run with Recovery Speed in {4,5,6,7}, but typically start out in 5 and adjust from there as conditions dictate.  I always run Iron Bias at 0.  I almost always do an auto ground balance.  Regardless of EMI I always start out with a Noise Cancel sequence as well.

From day 1 I've had trouble with EMI.  I never run gain higher than 22 and usually it's in {18,19,20} if I can get away with it.  The town I live in has most of their power transmission lines underground, and usually either in the curb strip or (if there is no curb strip) under the street.  Occasionally in the past I've had trouble with EMI with all my IB/VLF detectors, but nothing like what I experience with the Eqx 800.  The noise cancel process never does much when the EMI is bad.  When things are pretty quiet, that's when I notice a positive effect.

If I can't get the Eqx stable in multi-IQ and gain of 17 I just switch to single frequency.  Usually 5 kHz is noisy but I can almost always find a mid-frequency (usually 10 kHz and 15 kHz and always 20 kHz) that allows me to hunt with gain about 20, plus or minus.  Thus I have an operating detector in the worst case, but I lose the power and features of multifrequency.

This weekend the problem really became exacerbated.  I received permission to hunt an 1850 homestead which I'm 90% certain has never been detected.  Probably making matters worse was that I was salivating over the anticipated finds ("sugar plums dancing in my head").  When I got situated and turned on the Eqx I was blasted by EMI noise.  After a while I realized I was right over (or very near) the underground power transmission lines on the property!  (I didn't know they had 120V electricity in 1850.  ?)  As I got farther from the lines the detetor got quieter (not silent by any means) but in nearly 10 hours of hunting I was able to run multi-IQ less than an hour.  The only frequency that was consistently quiet (gain on 19) was 20 kHz.  5 kHz surprisingly worked better than 10 kHz and 15 kHz.  (I tend to shy away from running 40 kHz except when hunting native gold.  40 kHz was slightly noisier than 20 kHz when I checked.)  In case you haven't surmised it from my tone, I had pretty much a bust weekend hunt -- 3 Wheat pennies, oldest 1940, being the highlight.  A bit more evidence: I brought the Fisher F75 with Detech Ultimate 13" coil and it wouldn't quiet down either (ran the gain down to 30; there is a major gain shift going from 30 to 29 and things did quiet down below 30).  To make matters worse, the area (not suprisingly) was inundated with nails.  For most of the time I was running with Recovery Speed = 5 and getting about 6 or so grunts per (one way) swing.  When I decided to try RS = 7 the rate doubled.  Oh, the iron nails were so bad that I couldn't find quiet ground to do an auto GB, so just went with GB = 0.

When I have problems/questions/concerns I always begin by looking at the most likely source -- the detectorist, then the ground/location.  The last thing I do is blame the detector whether an individual case ('lemon') nor espeically the design.  When I read reports here it seems lots of people run gains of 23-25 and others recover coins from 8-10 inches (even 12 in) of depth on dry land.  The deepest coin I've ever found was no more than 7 inches deep, and I've found over 1500 coins with the Eqx.  I know Steve H. in particular downplays those depths because of ground considerations but my ground, although not Florida sand, is still considerably milder than much of the US West.  Occasionally posters talk about EMI problems but it seems to be an unusual occurrence, not nearly every time out like it is for me.  In the recent thread on Dankowski's forum (http://www.dankowskidetectors.com/discussions/read.php?2,166825,page=1) which Steve H. called attention to, Tom D. mentions about how debilitating EMI is.  Throw in ground issues and trash, especially iron, and modern IB detectors can still be fighting hard to distinguish/separate -- even give VDI hints at -- good targets.

When my hunt fires blanks for old coins (which has been happening a lot lately), rather than thinking "there was nothing there to find" I feel I've left a lot in the ground.  I really do have some good old sites and it boggles my mind there might be nothing left to recover.  My first culprit is the EMI I have to deal with robbing me of opportunities (and iron trash is my second target).  But after 300 hours I'm left wondering -- do I have an underperforming detector.  Phrunt recently chronicalled his issue with grounding problems on his Teknetics T2 and how things improved after he found and fixed the problem.  There has been much discussion about the potential wide variation in coil perfomance due to manufacturing inconsistencies.

Is there a standard set of tests to find out if a detector is suffering from poor shielding or other EMI anomalies?  Should I be contacting Minelab USA (and will they even believe me -- I'm sure they get lots of complaints by inexperienced detectorists)?  Sorry for the long rant, but the losing streak is getting to me.

 

 

 

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Its Hard to hunt above 22 sensitivity in most of my areas but I do everything I can to not drop below 20 if possible. I normally run wide open but will start using discrimination to quiet the detector down before I drop below 20.

If coin hunting I will notch out 1-11 and 14-17 which helps quiet the detector down noticeably. I also noise cancel and ground balance frequently.. sometimes manually selecting my channel if I’m not happy with the Auto choice, although most of the time it seems to pick the best channel. I have learned to hunt through quite bit of noise over the years. It’s taken myself a long time but I now trust my brain to sort out the noise.. it’s amazing how a certain tone amongst a sea of noise can stop you in your tracks..

Bryan

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Though I don't have a Nox, there is one field that has overhead transformers nearby. I can run my Tejon with stock coil with no issued at all fairly close to them and run it with full gain+ and it doesn't even chatter. I run my AT Pro in the same area with the stock coil and it does pretty well but if i get too close to the transformers it starts to become unstable. Lastly with the Nel Big on the AT Pro in the same area I can't get to 100+ yards of the transformers without it being so unstable it is useless. Even with the gain down to the minimum the VDI goes bonkers.

With that being said, I would try a single frequency >20 and if need be use a smaller coil.

I do wrap my wires a bit different, i run them from the coil with very long coil "fewer winds" near the coil on the abs shaft cinched off with velcro strap then tighter winds to take up the rest further up. I know the wires are pretty well shielded but I want to have minimal interference where it is closer to the coil. I started to do that as the Nel Big will actually sound off on the upper shaft when I set it down as I tend to keep the shafts short (reducing the weight to swing) and found a bit more stability on that coil.

The deepest coin i found was seated dime about 15" in one area and a 1950's dime in another are around 14" with the big coil. Both those areas were swampy and had a ton of top soil before you hit clay. Majority of my coins i find are far less than 10".

You may want to see where that clay line sits at that old area and maybe you can use a much smaller coil with the same success.

I really believe that coins don't sink past clay or at least I haven't seen that to be the case unless the ground had some construction around and it was turned up. I believe fields are only turned over 6" or so.

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The thread is already full of great tuning tips so I will focus on the “how to check Equinox” part.

I’ll be the one and pipe up to suggest there are times when you need another detector but your F75 seems to confirm this is not just an Equinox issue. Our power grid system is is fairly poor and generates lots of stuff it should not. Throw in a new wireless device or cell tower being installed on every corner and it gets worse. And the killer... some of the new LED lighting is really bad and everything is going LED.

I’m not saying it’s impossible that you machine has an issue but I don’t know how one could know short of having another Equinox with which to compare. Did you use the small coil? That often helps a lot with EMI and eliminates the stock coil at least as a possible issue.

Once you lose confidence it’s hard to get it back. Try and find someone nearby with an Equinox to compare to and worst case send it off to Minelab to be checked. I’m not sure what they will do but it sure can’t hurt.

Multifrequency is more susceptible to EMI and it’s unpredictable as to what works and where. I never could get a White’s V3i to work at a large number of places in Anchorage, AK so much so I gave up after trying a couple. It was not until I moved to Reno I became happy with the machine.

 

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my cure for EMI problems with my Nox 800 is lowering the sensitivity, lowering the recovery speed (had much impact - I use 4), Iron bias (I use 4), use descrimination -9 to 0 NOT all metal as EMI sometimes effects lower numbers more, use different programs....maybe Field 1 is quieter than Park 2 or .......???? Try and find out which program is acting the quietes? Sometimes EMI is bad when I hold the coil still but disappears when I start swinging the coil. Single frequency does do the trick but first I try the before mentioned. A 6" coil is waiting for me in CA. I'll bring it home when I return and give it a try. One more thing - perform noise cancel with coil flat of the ground. Manual ground balance (pumping the coil over a clean spot) All this helped me hunting some places I could not hunt before.

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I have nothing really to add that has not been said...there are some places that I can not hunt and it's always underground wires that are causing the problem. I always carry two detectors just in case. as eluded to above maybe try running it in the stock programs. I run mine similar to the way you run yours.

strick

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It all boils down to harmonics. Trick is this case is to find the frequency that gives you best balance of detection depth with the least amount of noise and then choose the largest coil that balances that all out. I would think you should be fine with the stock coil and just be a matter of cycling through the frequencies until you find one that works. In tough areas you at least have that advantage of a wide choice of frequencies to pick from.

I would try to wrap the wire a bit different too, have fewer winds as possible on the lower pole then take up the slack further up. This might reduce some of the noise or at the minimum it looks more sophisticated.

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Perhaps this may be the unusual circumstance when Noise Cancel would be more effective if done with the coil on or near the ground? I haven't hunted where underground power lines lie, but it seems you have mostly tried all the conventional methods of tackling your emi overload. 

Given your situation I'd venture to suggest making all your other settings first and then play with sensitivity and noise cancel last. Trying NC with coil grounded. Worth a shot.

 

 

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I do not have a Nox, but I have found that EMI can come from anywhere and sometimes it is a process of elimination of where it is coming from. The following EMI issue I had was from the least expected source and still do not understand why it happened.

I purchased a Makro Kruzer over a year ago and shortly after I got it I decided to see what depth I could get on coins in the type of soil we have here in Colorado. I had my White's TDI  with me and I use that detector for hunting older parks and get great results in find older coins that normally out of range of VLF type detectors. My experiment was to locate a deep sounding coin with the White's TDI and then use the Makro Kruzer to see what type of a response the detector would give me. I had hunted this park many times before with the White's TDI and never experienced any EMI issues and I normally run the detector at full gain. That day I was having a hard time running the White's TDI even with the gain greatly reduced. I was becoming very frustrated as I went to different areas in the park and no improvement. I did manage to locate some coins with the White's TDI, but the coins were much shallower than previous hunts. I hunted for a couple of hours and tried different settings to try to eliminate the EMI. Frustrated I made my way back to my car and was packing up to go and try a different park. I put the Makro Kruzer in trunk and for some reason I turned on the White's TDI and the EMI issues were gone. I got the Makro Kruzer back out to see if that was indeed the problem and yes that was problem. More unbelievable was the detector was turned off.   Luckily it only took me a couple hours to figure it out.

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  • 3 weeks later...

Decided a bit of followup is in order as my post left some things up-in-the-air.  (Thanks for all the thoughtful and helpful responses.)  I haven't gotten in much hunting time since that 1850's homestead weekend for various reasons.  But the two new locations (both public parks) I have searched have given me little to no EMI problems.  In one case I just set the gain to 20 but did run it up to 22 and didn't get any interference.  In the other case I ran most of the 4 hour session in Park 1, gain 22 and even tried 25.  Still no noticeable EMI!  Neither of these parks is located in my hometown where I've done 99% of my coin hunting.

So, what's going on?  I think underground power lines are the main source, with possible additional headaches from private radios (like they sometimes or at least used to have at construction sites).  There are so many sources of problematic EMI and as others have pointed out, they vary a lot by location and even by time.  My hometown has long ago converted from overhead power transmission to underground, and I'm sure the depth at which they are buried is a factor.  In my cases there are likely other variables, too.

As far as why I don't find coins deeper than about 6 inches, I think I'm getting a read on that now that I've installed my test-stand.  I'll post more evidence as I collect it, but from what I've seen so far, it is the ground magnetic susceptibility affecting the TID.  (Sound familiar?  Steve just mentioned this with regards the using TID for dig/no-dig decisions when using the Eqx for hunting native gold.)  My current thinking is that the TID drops as depth increases and I'm mentally rejecting (discriminating against) low tones.  (This problem isn't unique to the Eqx and might even be universal.)  Stay tuned.

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