EMI and the GPX-4000 and GPX-4500


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Hey Everyone,

What I often do is pick up my 4500 manual and read the same section even if I just read it a week ago, I always seem to pick up on something I previously missed, take the AUTO TUNE feature.

In the GPX-4000 manual it states “If AUTO TUNE is not working well in SLOW or VERY SLOW MOTION, try selecting MEDIUM settingâ€

In the GPX-4500 manual it states “Any interference is made more obvious with a faster motion setting. Therefore, you can assist the AUTO TUNE function in selecting the quietist frequency band by selecting FAST MOTION before performing the AUTO TUNE process.â€

Question #1.

Why was the FAST MOTION setting not recommended in the 4000 manual?

Question #2

What about GAIN, would you not want you’re GAIN to be set to (20) when performing an AUTO TUNE?

Thanks

Tony Teixeira

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Tony,

When I first got my 4000, I read a very intelligent post by AZ4AU Mike on Bill Southern's forum that said before you auto tune

he suggested putting the detector in Fixed and set a fairly high gain. I don't remember if he mentioned the Motion setting.

I think what you say makes good sense. If you up the sensitivity on these settings you are enabling Auto Tune

to read the highest amount of EMI to arrive at it's setting. At least I think that's what you're getting at.

BTW I do use Mikes suggestions and I think he was in the ball park.

And again, as I almost always mention in these topics, the biggest boon to good detecting

is to become a fanatic about Ground Balancing correctly.

This single trait is the hallmark of the best detectorists I have seen.

You have raised another interesting topic - one that I am sure will

attract some interesting and informed comments.

Flak

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Hi Flak,

Yep, that's what I am getting at.

You know I think with all these whistles and bells I need to break my detector into modules so to speak like in programming, I call this one the "eliminate EMI" module, lol.

Hmmmm, It would be nice to know what functions impact EMI going into the machine before any filters impact the data, I don't know if FIXED has an impact at this point, I was thinking MOTION, GAIN..... maybe the STABILIZER?

At least I would think MOTION and GAIN would make the detector very susceptible to EMI and would be set high before AUTO TUNE.

Hopefully someone will chime in.

Tony

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Hi Tony,

Well sofar a two person thread. It will change.

I went out today for about two hours before the wind came up to about 45 and I

couldn't take the buffeting.

I set Motion to Fast, Gain to 15 and Fixed (just for kicks) before I AutoTuned.

Then I set gain at 10, Motion to Very Slow and hunted with Ground Balance in Tracking.

I think there was a definate difference - for the better. The place where I was is famous

for very bad EMI and it was almost completely eliminated. I didn't even tweek the AutoTune.

The other thing I noticed was that when the wind started gusting it messed with the signal if the coil was

more than a few inches off the ground, but did not effect the threshold when I had coil at

the correct sweep height.

I didn't find any gold, but the tiny pieces of metal and wire I found were in the most heavily

hit spot I know of and these pieces, amidst a sea of dig holes, surely would have been dug up if they had been heard.

fwiw,

Flak

ps, I see on that Oz forum where you posted the same question, there is a reply to the reasons for autotuning

in Fixed...did you see it?

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ps, I see on that Oz forum where you posted the same question, there is a reply to the reasons for autotuning

in Fixed...did you see it?

Flak,

WOW! That's cool that you can notice a difference, especially if it's for the better.

No I am not seeing it the post for the reason why, but I do see where Spinifex say's "I think the text book version would be to stay in fixed whilst auto tuning". Is that what you mean?

I think I will setup a mode like "test A" with a FAST MOTION, HIGH GAIN, FIXED and anything else that makes the detector supseptible to EMI and use that mode for startup with AUTO TUNE.

Hey next time post a nugget! I am the one in charge of posting wire, lead and BB's. ;)

Take Care!

Tony Teixeira

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Tony,

Yes, Spinifex' post about the text book version was what I was referring to.

Nuggets?

That is a long story and not for this thread.

(I also see that the skunk is eyeing me from over in the corner where he stays

when he is visiting, which is most of the time these days...).

Flak

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Tony,

Yes, Spinifex' post about the text book version was what I was referring to.

Nuggets?

That is a long story and not for this thread.

(I also see that the skunk is eyeing me from over in the corner where he stays

when he is visiting, which is most of the time these days...).

Flak

Hey Flak, whenever you make it out this way again, I have a few spots with plenty of skunk traps scattered around.

DigDeep

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Hey Tony,

I tried amping up the gain and a few other things when doing the auto tuner. What I got was the detector choosing way different frequencies each time from 53 to around 200 and several in between. I think mainly it was because the detector was being bombarded with so much EMI it could not find a usable frequency.

When I went back to my settings I run in it would stay between 95 & 120.

In about every case I still found it happiest at one particular number (101).

In the area I was in last, I get the odd EMI wiggle worble and bang, can't tune out, they are too infrequent (usually planes), then the EMI that if you tune for one you get the other - just have to pick the lesser of two evils, and last but not least you get the vicious ninja EMI that out of nowhere twists up everything, sometimes last for a 30 sec. sometimes for an hour, then Poof - gone.

Planes - military - radar - secret spy stuff lol, who knows.

(Flak I have hunted where you usually do and I feel your pain, damn it sucks EMI eggs there)

DigDeep

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Hey DigDeep,

I go out there not only because of the obvious reason that it is closest

and I don't get much more than a quickie day trip these days, but I

quite like tough detecting. It makes me learn the machine much better

than I would if I could just get away with turning it on an going.

When you find something in tough conditions you know you've earned it.

If I could get out to the Dale more I would be happy. I love that

place, I think it is loaded with possibility but it takes time over the coil

to find anything and I am just so short on time these days.

Continued good hunting, I know you do well and I

know you earn what you find. Just a few minutes watching you a

few weeks ago told me you know what you are doing.

All the best,

Flak

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I tried amping up the gain and a few other things when doing the auto tuner. What I got was the detector choosing way different frequencies each time from 53 to around 200 and several in between. I think mainly it was because the detector was being bombarded with so much EMI it could not find a usable frequency.

DigDeep

DigDeep,

Yea, I guess if you were in an area where the EMI stayed at constant frequency or without much variance the AUTO TUNE would get you to a great reference channel to hunt in, but if you had a variable change in frequencies all the time it would not help.

Maybe that's why Montana and QLD Sandy hunt with the manual tune highlighted in their menu.

Well, I enjoyed this topic and I hope to play around with settings this weekend, I am hoping to see more of a consistency as Flak did. Boy, that EMI must be KILLER on the larger sensitive aftermarket coils....lol.

Take care!

Tony

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  • Admin

Hey Guys,

This is a very interesting thread. I will tell you what I have experienced using the Minelab PI for the last 16 years. There is no doubt on the GPX series if you place your Gain and Motion higher and "Auto Tune" it you will notice much smoother results when you go back to a slower motion and lower gain after the unit has completed the "Auto Tune." However, there have been times this little tip worked miracles with really bad EMI, but there was also some times it didn't seem to do much at all.

Flak - I seen you have noticed the new Goldstalker Searchcoils are less affected by EMI. Trev mentioned during his visit to Arizona that the new coils have much better shielding that helps elliminate EMI. I noticed it right away on the new coils when I was testing them some time ago.

As far as adjusting freqs from 1 - 250 manually, keep in mind the lower freqs seem to be better for deeper ground and the higher freqs better for more sensitivity. This is just what I have noticed over the years with both the GPX-4000 and GPX-4500.

As an experiment one time I tossed down a very small 2 grain gold nugget on the surface. I "Auto Tuned" the GPX-4500 and it stopped at 241. When I went over the nugget it just screamed. I then retuned the unit and it landed on 52 and the nugget wasn't as loud. I probably lost about 1/4 the signal I got with the higher freq.

Just some things I have noticed.

Take care,

Rob Allison

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Tony,

I should have added

I was using one of the newer Goldstalker 14" Mono's.

While that coil is not as sensitive to EMI as some of the larger coils

it still gets hit pretty hard.

What's your next topic going to be?

Flak

Flak,

Your turn to pick a topic! I wish DigDeeps question on Specific vs General would have received my feedback, I thought in OZ it would have had more.

I know I will have more questions next week. ;)

Are you down in SoCal with DigDeep?

Tony

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Flak - I seen you have noticed the new Goldstalker Searchcoils are less affected by EMI. Trev mentioned during his visit to Arizona that the new coils have much better shielding that helps elliminate EMI. I noticed it right away on the new coils when I was testing them some time ago.

Hey Rob,

Little confused here, That D3 coil Trevor used was a DD and when I asked if he plans to build mono coils he said "Tony: Great souvenier indeed. The Goldstalkers are already in MONO." so I assume no change in the MONO design.

So when you say "Trev mentioned during his visit to Arizona that the new coils have much better shielding that helps elliminate EMI" this would only apply to the new DD coil since the MONO Goldstalker will remain the same.

Am I understanding this right?

Thanks

Tony

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I will have to try setting the RX and Motion just a little higher than normal and try the auto tuning. When tried it I had them pretty maxed out and maybe was overboard.

DigDeep

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  • Admin

Hey Tony,

That is correct, the Goldstalker Searchcoils right now are all Monoloops. These are the newest version of the Coiltek coils that include the new lightweight design, better shielding and "no false" properties. Since Coiltek made five coils (6, 16 & 18-inch rounds and 14 & 18.5-inch ellipticals) many have requested DD coils in the same designs. The D3 coil that I have is a Goldstalker with all the same properties as above, but in DD rather than Mono.

I'm sure in the near future more DD coils will be available.

Talk with you later,

Rob Allison

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Hey Tony,

That is correct, the Goldstalker Searchcoils right now are all Monoloops. These are the newest version of the Coiltek coils that include the new lightweight design, better shielding and "no false" properties. Since Coiltek made five coils (6, 14 & 16-inch rounds and 14 & 18.5-inch ellipticals) many have requested DD coils in the same designs. The D3 coil that I have is a Goldstalker with all the same properties as above, but in DD rather than Mono.

I'm sure in the near future more DD coils will be available.

Talk with you later,

Rob Allison

Thanks for clearing that up for me.... By the way, 14" Round Goldstalker? I never seen one advertised. What are they going for?

Tony

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Tony,

Yes I'm in SoCal with DigDeep.

DigDeep,

You might be ok not to totally max out the RX,

but do turn Motion to Fast, I think it'll please you..

Rob,

I like the Goldstalker coil, it still falses a bit but not nearly as much as most of the

earlier coils of all sorts of brands that I own.

I like the sound of the new Nuggetfinder Advantage coil too, but that will

have to wait until the skunk decides to head out for another area and I can

find enough to pay for one.

I'm trying to think of a topic...

Flak

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Hey Flak, have you had a chance to run your dual speakers, if so how do you like them.

They sound pretty nice for summer months and I have already came up on three Rattlers :unsure: this month.

I think Rob has a new speaker that works well with the 4500 but I am not sure if or how they can be wired up dual.

DigDeep

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DigDeep,

I have used dual speakers for about four years and really like them

(not bragging here, I just happened on them early on).

I also use headphones fairly often (more often than I like), what with

the wind that's been so frequent lately in the desert, and when I'm hunting

with people who are close-bye I give them a break.

But dual speakers are my first choice to hunt with.

In all the time I have hunted I have only seen two rattlers

and when I hear how many other people see,

I get the spooky feeling that I may not have been seeing as many as I should have.

:blink:

Flak

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