Minelab GPX4500 tips, settings, questions

[Heatho]

Could inverted kinda be a way of discriminating?

Hey Dave, no, Inverted just changes signal tones from low high to high low or vice versa. I guess it does help discrim large targets from small but any target could potentially be a gold nugget.

Yes with the Stabiliser, lower number higher influence. I think starting from 1 and going up could be counter productive, Start at the factory preset level and go either way from there. If it's quiet at the factory level try going up, if it's a bit chattery take it down until it smooths out enough to be reasonably stable.

 

[rc62burke]

Hi Davent
Mate before you start playing with settings etc, you need to be certain of the source of the unwanted noise, Ground Noise or EMI.
EMI will still be present when the coil is held still.
Ground Noise is present when you sweep the coil side to side.
cheers
Lee

 

[BigWave]

Dave,
If your machine suddenly starts continual warbling, then that's likely radio traffic or another detector close-by providing EMI. Try manual tune to quieten the machine (suggest between 80 and 100).
Also, try using Motion: "Slow" (or very slow) and Audio Type: "Quiet". This will make a big difference, but means you have to go slow. Also try Soil Timings: "Enhance" and Search Mode: "Deep" on your front-end cap.
If the machine still won't quieten down and it's not EMI, then you may want to have your coil checked. Tried another coil?

 

[user 4485]

Hi Davent
Mate before you start playing with settings etc, you need to be certain of the source of the unwanted noise, Ground Noise or EMI.
EMI will still be present when the coil is held still.
Ground Noise is present when you sweep the coil side to side.
cheers
Lee

Lee is right & on re-reading your post/s it does seem a little unclear if you are sure whether it's ground noise or EMI? You need to know so you can tune or balance it out effectively.

Dave,
If your machine suddenly starts continual warbling, then that's likely radio traffic or another detector close-by providing EMI. Try manual tune to quieten the machine (suggest between 80 and 100).
Also, try using Motion: "Slow" (or very slow) and Audio Type: "Quiet". This will make a big difference, but means you have to go slow. Also try Soil Timings: "Enhance" and Search Mode: "Deep" on your front-end cap.
If the machine still won't quieten down and it's not EMI, then you may want to have your coil checked. Tried another coil?

I would auto tune first & go from there. These machines are designed to pick the best channel for you & IMO using suggested settings may not work in different areas let alone the same area all the time.
Also if you select Motion: "Slow" (or very slow) and Audio Type: "Quiet" then Search Mode: "Deep" on your front-end cap unless you have changed the "Deep" search mode to your own preferences it will revert back to the factory presets of Motion "Very slow", Audio type "Deep" & a preset gain of 9.
This is why it's recommended to:
1. Select an appropriate Search Mode
2. Select the desired Audio Type
3. Adjust Rx Gain until the threshold starts to break up
4. Adjust Stabilizer to smooth out the threshold.

 

[Davent]

I actually think its a combo of both ground noise and emi.
When the coil is still, it sometimes warblers, and when on the move, can be quiet, then warble over a small area and then be stable, go back to the area, and warble starts again..... will take it to an area where it has run quiet before, and play with it out there again. Both area,s are pretty close to the stuart highway, and unfortunately, the grey nomads and road trains are flat out this time of the year.

Bet the grey nomads get on the CB,s every time they pass a gold field "hey john and liz,, this is an old chinese gold field on our right hand side over" then the radio traffic starts and my machine goes nuts.....

 

[user 4485]

http://www.minelab.com/__files/f/11043/KBA%2000-1%20Metal%20Detector%20Basics%20and%20Theory.pdf
This may be worth a read & has a section on electro magnetic noise sources (Section 2 - 2.1) that may give you some better ideas on where it's coming if EMI?

 

[Davent]

Thanks mbasko, from what Ive read there, it actually could have been the rain in and near Darwin, some 100km as crow flys to the north, apparently it was a very wet start to May, and there may have been some lightning, sheet and fork around the top end that day.
Now , need to play on some stable ground, get it all going nice, then hit the area again and see how different the soil is.
May need to buy one of those flash Detech 15"DD ultras.....

 

[PhaseTech]

Very easy to tell if the noise you are getting is from ground or EMI - just stop moving your coil. Ground, like targets will only respond when your coil is moving.

If the noises go away, then it is ground noise, in which case drop your Rx Gain first.

If the noises stay when you've stopped moving the coil, then it's EMI. So how to deal with EMI?

I've just put up a Blog talking about this very issue

http://phasetechnical.com.au/gpx5000-how-to-deal-with-emi/

 

[Davent]

Many thanks to all who replied, special thanks to old hand, and Nenads blog.
thanks fellas. Turns out, (new to me) charcoal, and wet charcoal is pretty noisy......well it did rain that morning, so ground was wet, plenty of burnt stuff around. So ground noise with EMI from choppers and road traffic near the high way ....perfect storm, also learnt a lot about settings, esspecially from old hand, so thanks all.
cheers dave.

 

[Hedigs]

Awesome info! Thankyou

 

[reynard]

G,day all, I am after opinions on wether you detect in tracking or fixed and. Why. I run a 4500 and have tried both but the jury is still out. All opinions great fully accepted.

 

[old hand]

Hi mate I am running a new 45 with a NF 15 super light evo I use fixed all the time ,I got into the habit back in the gp extreme days the word was that by using fixed you gained a bit more depth than tracking I do not know if its right or not but still use fixed and I will not change, another think with using fixed the detector tells when the ground conditions change regards john

 

[reynard]

thanks john. I have always used tracking and we are having a lean time at the moment, so was wondering if maybe we are not tracking targets out.
jim

 

[BigWave]

Most l know run in fixed. Just be sure to re-balance regularly. Like old hand, I like to know when the ground changes.

 

[reynard]

thanks bw this is the way I,ve been thinking. going to be in the triangle at Inglewood from next weekend for a week so will give it a try . jim

 

[Westaus]

I read an article in Australia Gold and Gems were they talked about the Mylar strips in some detectors became faulty, cannot remember if the 4500 was mentioned. However these strip can crack right near the connection and one of the key issues was ground balance? So not sure if a connection issue or not. Something to consider if you feel there is an issue.

 

[reynard]

thanks westaus, no trouble with ground balance just trying to decide witch is the better mode to run in

 

[markgoldhunter]

I have always run in fixed but this year with the elite coil on I have swung back to tracking and as soon as I get a target I switch to fixed that way no chance to track out a target and I find I can tweak the gain a point or two as the tracking takes care of any uneven ground responses. p.s. i'm at Wedderburn at the moment if you want to take a run up next week. cheers mark.

 

[user 4485]

This was my preferred way to run the SD2200D mainly due to no quick track button. I'm pretty sure there is a post on here somewhere by Nenad explaining the advantages of using tracking in some situations much better than I can.
Basically my thoughts are in ground with a lot of variable mineralisation it can be beneficial to use tracking like MGH suggests above - flick to fixed or hold the quick track button in once a target is located.

Ground Balance reset in Tracking
While detecting in Tracking you should periodically test that you are still in harmony with the ground by stopping, then raising and lowering the coil. If the Threshold remains stable
then you are still Ground Balanced. If there is a change in the Threshold then you need to reset the Ground Balance setting.
Do this by continuing to raise and lower the coil, or repeat the
procedure on p. 40.
While raising and lowering the coil press and release the Quick-Trak button. A short beep will be heard which lets you know that a three second, fast auto-Ground Balance is initiated
prior to returning to Tracking. Once the audio has stabilized you can continue searching.
If you find that the Ground Balance needs to be reset quite regularly, you can select a Faster Tracking speed. Three Tracking speed options (p. 70) are available from the LCD menu.
Note: In highly variable ground the Tracking may not instantly update the GB setting when you detect over a large mineralisation change; so there may be a period of time where
you will experience some ground signals. To avoid missing any faint target signals you may have to reset the ground balance, and slow down your detecting sweep speed to allow the
Tracking to keep up with the ground variations.

Like mono coils the constant use of fixed seems to be ingrained to a lot of GPX users, myself included when I had one. In hindsight the ability to use tracking or DD coils or other little used settings to suit individual situations is one of GPX strong points & a lot of people get stuck on set ways of running - which is fine - but if I ever get a GPX again experimenting to find settings that suit myself or if I thought a DD coil will run better in certain ground would be things I'd do more rather than just follow the flock.

 

[GypsyGoldAu]

Tracking = \/ \/\/\/\/ /\/\/\/~~~/\/\/\

Fixed= ----------/\---------/\---------

which is easier to look at/hear?...

For my $$$ it's fixed all the way, & regular balancing as the ground alerts to changes.

I find tracking just too exhausting to listen to and define the response, especially those whisper quiet threshold breaks that aren't really a weeoo or wooee response, just a break in the audio.

Gypsy