GPX4500 - Performance

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GPX4500 - Performance

Post  mulgadansa on Thu Apr 16, 2009 10:02 pm

I thought I’d chuck my two bobs worth in regarding how I think the 4500 performs after having used it over the past year.
A bit of background on me just to try and establish some sort of credibility (or not).
I started prospecting back in 1978, based in Meekatharra WA, and went full time in 79. I went on to do this for a job until 1985. The last year of that was washing alluvial dirt (75-100 ton a day) through a sluice plant we built at Nannine.
The weapon of choice back then was the Garrett Deep Seeker. My partner and I found a truckload of the yellow stuff with those machines. We met a couple of young guys who convinced us that the Groundhog was a better machine and that is what we then used for the next couple of years (the Groundhog thing is leading somewhere later in this missive).
We were a couple of those guys that ran around the countryside knocking over patches with a backblade or dozer. I’ve since revisited a lot of those sites and the revegetation where we’d shifted the dirt is fairly impressive.
Anyway, back to the new machine. I bought my 4500 a year ago. Pretty impressive unit (I wasn’t going to use the word “impressive” again but couldn’t think of another word that conveyed the same message). I’ve used several of the PI machines, admittedly only on a part time basis, as family matters dictated that prospecting took a back seat.
The earlier machines were dead simple to use and very effective. The 4500 is a different kettle of fish. I sorted out how to get what I feel is the best out of the machine, no doubt the settings I run on are completely different to guys in the Eastern states.
What really peeved me was that the 4500 is horribly prone to EMI, whereas earlier machines were not so. Balance that with the ability to run smooth in some very ordinary country and I guess you’ve got a trade of sorts.
Back to that thing about the Groundhogs. I was in my shed a couple of months ago and the old A2B was sitting there gathering dust and looking miserable with its’ tiny six inch coil (I’m running a 17x10 mono on the 4500). I thought crap, we never had any EMI issues with those machines (I know they are chalk and cheese but bear with me). I always thought that these big coils are just an antennae for the EMI, so rang Petra at Reeds and ordered an 8” Commander mono.
I’ve done a couple of runs with it now and when the big coil starts arcing up I plug the 8” on and guess what, almost no EMI!
If you want to extend your day without EMI, try the smaller coil, I love it.
I’ve had great service out of ML but I can’t believe they have released the 4500, together with the rather large price tag, without dealing with this EMI issue. They should have sorted it out by now, given how long and how many detectors they have produced. They promote the unit as the bees knees for large monos, yet they are unstable in our conditions. At least now I can live with half the day on the big coil and the latter part on the baby one chasing small stuff.
It’s interesting that I run on one particular setting (in the meld of thousands available on the 4500) that no one has ever mentioned on this or other forums. It makes a massive difference and I’m not gonna say anything further on that matter.
All in all I think the 4500 is a brilliant unit, albeit with no greater depth capability than previous units. It’s only the smoothness that lets you hear beyond the hotrocks and ground noise.
Cheers
Brett
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Post  buck06 on Thu Apr 16, 2009 10:29 pm

cool stuff brett my year about the same .the advice on smaller coil is great diddnt even think of that affraid i am still trying different things with the 4500 as there are so many different settings and that many different soil types that i dont think everybody has tryed so its everdays a school day for me . cheers cheers buck
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Re: GPX4500 - Performance

Post  Jonathan Porter on Fri Apr 17, 2009 8:05 pm

Brett is it possible your secret setting might be the cause or at least be promoting your problems with EMI (Sharp mode springs to mind here). The main problem with EMI lately is the VERY unstable weather patterns we have been experiencing throughout Australia this summer (and still are).

To keep a balance on your GPX 4500, pay attention to the FP settings in the General Search Mode option of the 4500 as they are very close to the way Minelab set their other GP series machines (especially things like Gain, Motion, Stabilizer etc).

Hope this helps,

JP
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Post  buck06 on Sat Apr 18, 2009 10:57 am

you are pritty correct jp the fp are pritty close to getting rid of those spikes What a Face . ihave one area where every know and then it dosnt matter what machine you run it is nealy imposable to detect . finally worked out it was a tv towwer which moves it direction sometimes . i thaugh it was me but have tryed 2200 3000 3500 4500 on those bad days it dosent matter Question Question we just go somewere else buck
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Re: GPX4500 - Performance

Post  mulgadansa on Sat Apr 18, 2009 11:35 am

Gday Buck and JP
JP, I don't use Sharp and I run my gain as close to 8 as possible, only dropping a point off that if it's absolutely necessary. I'll try and get that a bit higher on the rare occasion when conditions permit. I think the gain is probably the most critical filter on the machine but Motion (I try and use Slow) and Stabiliser (almost always run 10), make up the Trifecta for me. They are the most important filters affecting the integrity of the 4500. I think if you lower other factory presets you are just starting to dumb down the machine further but not to the same extent as those three settings.
Using Slow in the Motion setting means you have to do just that, swing at a reasonably slow rate, not Patch Finding pace.
I notice on the forum that a lot of guys sing the praises of Enhance. I've tried it heaps of times and it's just too noisy where I'm working. I know you've been over here JP, so you'd understand what we're up against in the Murchison/East Murchison with the banded irons, magnetites and a whole host of other materials of similar natures.
Yep, the weather has been mud for the past year or more but other ML users I've been out with who use older models, don't have nearly the same issues with EMI.
The 4500 are great machines but I'll just about bet the next model will have gotten rid of the EMI issue. If not I might just have a talk to Ismael and see what he can do for me.
cheers
Brett
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