Correct sequence to adjusting GPX settings?

G'day again....

In case I have missed some key understanding somewhere I am curious to know if there is a hard and fast rule as to the order of adjustment / correct sequence in setting up/tuning the Rx Gain - Stabilizer - Threshold on the 4500 once you have turned the machine on? Is this the correct order until its all humming OK or just a case of a little bit here and a little bit there depending on soil conditions ?

thanx

Mal

G'day Mal

According to the manual the stabalizer is adjusted last after making adjustments to the Rx gain etc.

From the manual:
"Note: Regardless of which Audio Type is selected, the optimal position of the stabilizer is one number below the point where the threshold begins to chatter."

"Tip: By turning the stabilizer control close to minimum (<3) the threshold will be very stable, but you will lose a lot of sensitivity to smaller targets. This can be a desirable feature in certain scenarios, such as looking for large nuggets in a high-trash area, or using the GPX-4500 to search for coins or treasure."

"Tip: We recommend the best order for setting these controls are:
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."

The manual can be downloaded from the minelab web site if you don't have one.
http://www.minelab.com/aus/consumer/knowledge-base/product-manuals

cheers dave

Thanks Dave....I tend to scan rather than read and therin lies the problem...didnt sink in.

I tend to prospect alone and not discuss settings too much with others in the field or come across too many other prospectors when I am out and about. I only use small monos and can usually be found running between the quartz and ironstone.

Dont get me wrong bout this but I can generally get my machine to run pretty smooth and I have managed to find gold through good research and persistence and good luck. I have almost nutted out most settings to maximise my machine's best performance and maybe I just want get that little bit extra. When I bought the 4500 new in early Jan 2010 I bought the JP DVD and booked in for a couple of different training days and I thought .....yep...I am thinking I am on the right track here. The DVD says set the Threshold to 2 oclock. OK fine. Then I am told that RxGain is set about 8 and the Stabiliser about 10 but then others telling me its always set about 1 below that of the Gain????. OK fine. (And by the way I got gold around here on those settings :-))

Anyway..the first course I did I got a set of references between the Rx and Stabilizer. It depends on conditions like still early morning, cool, still air to windy etc.

Rx 12...... 13........ 14
Stab 6-7....... 5-6 ....... 5
No mention about Threshold with any of this but thats OK.

Second Training day I did elsewhere...

Rx 7-13 (10 for cool air still morning)
Stab 8-13
Wind up gain then wind up stab 1 or 2 morer either way??????
Still no talk about Threshold settings as well. (I am still thinkin 2 o clock Thresh yep yep)

What threw the spanner in the works for me was the discussion by members here and on another forum re Bogene's setting ideas that I only recently discovered in some old posts and I wasnt up to speed with. I had never thought of running the Threshold from anything less that the 2 oclock position before. Let alone having a big difference between the Rx and the Stabilizer. And these guys (disciples?)are running around with next to nothing Threshold so whats happened to all the rules in running the GPX?

So now what has changed for me. ....I run my Rx from 8 to 13 and my Stab goes down the other way towards 6or7 all depending on the conditions at the time. And Threshold can be around 10 oclock depending how my hearing is going for me with my underslung earpieces on the day.
And finally ...is all my waffle above here just about turning the machine on with the previous threshold set say at about 10 bells and then dialling in the Rx and Stab to get that nice smooth humm and away we go...or is it just a never ending tweak here and a tweak here all the time.

Hope this sort of makes sense and sorry about my confessional here but its helping me to clear up some of the theory that has been confusing me on and off for some time.

Any further thoughts welcome

Mal

though i have a 5000 the settings are almost the same.

i usually run Gain at 13. this new coil allows me to run it at 14. I usually wind the gain up until it starts becoming unstable, then i knock it back one. I then adjust the stabiliser. Usually it remains where it it. i'll try and increase it by one point at a time, but if it becomes unstable i back it off. These really are the only two adjustments i make on my 5000.

I have only been detecting for a year and had the 5000 for 5 months, but i try and keep settings simple and adjust these 2 settings.

G'day Mal

Its interesting that you have noticed there is not much talk about where to run the threshold. JP's DVD's are a good benchmark on how to setup your machine.

I have noticed that not all 4500 machines are quite the same when it comes to where the threshold knob is positioned to get the same level of sound. I run mine at about the 11'Oclock position and that is good on mine.

To find out the best position for yours is to turn it up to say 3'Oclock then back it off until its got no sound then gradually turn it up until you have a nice smooth hum, not to loud, this is usually somewhere between 10'Oclock to 12'Oclock positions.

If you have the threshold to loud (turned up to high) you can drown out (mask) the faint soft signals.

I have tried Bogene's settings but they wern't for me, some people like them.

I tend to run my detector on RX gain 12 and stabalizer 6 a lot of the time, and depending what size coil I have on will run the audio in boost if its a small coil(11") and deep if its a larger coil(16"). I run the front end cap switches in "Search mode" in "G", "soil timings" in "enhance" most of the time, "Ground Balance" in "Fixed" when running enhance, "Coil RX" in "Mono".

This works well for me.

cheers dave

I often find operators insisting on running high Gain levels on their detectors and having to back off other controls to compensate for the instability of the detector. All previous Minelab PI machines which had fixed Gain settings were running on the equivalent of '8' for the 4500 or '11' on the GPX 5000. Obviously having the ability to run higher Gain levels is an advantage in the later digital detectors but operators need to keep in mind the other controls that are also adjustable such as the Stabilizer control etc.

As a good rule of thumb, assuming you are using a Smooth type timing, a setting of 8 on the Stabilizer function will allow an elevated Gain setting a few points above FP which will help compensate for the signal response loss due to the timing. Too low on the Stabilizer and information can be lost, too much Gain and good information can also be lost in the resultant clutter. If you are having to back off your Motion and Stabilizer setting then that suggests you are running too much Gain, so why not back off the Gain setting a little first and see what happens?

In a lot of ways a higher Stabilizer setting will allow more raw information through than having a high Gain setting, so why not experiment with a Lower than FP Gain setting and a higher than FP Stabilizer setting? If the detector sounds unstable you can easily go to a Very Slow Motion setting and then adjust your swing speed to suit.

At the end of the day the detector needs to be stable relative to the conditions you're detecting in. The conditions are dictated by atmospherics, ground mineralisation levels, coil size, target size and orientation and lastly your mind set. Having faith in the way your detector is set up conditions wise goes a long way to having a positive experience, generating a positive experience is never going to happen if the detector is driving you crazy!!!

JP

Jonathan, you are so right about getting more raw information by boosting the gain. Yesterday I found a little speci on a mullock heap with gain on 8 and stabilizer on 10 , then went over the entire mullock heap and found 2 more targets. Not wishing to give up on the mullock heap, I boosted the gain to 15 just to experiment and found another 8 targets! You couldn't walk around with this setting , but on a suspect mullock heap it's worth having a go.

Thanks to everyone for taking the time out to explain the settings in better detail for me. Its a lot clearer now than when I had the tunnel viewer on before. Most of the time up until now, the 4500 machine ran reasonably smoothly on basic settings but it could quite easily get out of whack due to changing conditions. I didnt get the best out of my machine and thats where my lack of understanding came in regarding the tuning. I am pretty sure now that I will get a lot more pleasure out of the 4500 than I had previously.

I cant waít to get out and pick over a couple of old patches of mine with some new settings to see if I missed anything from my previous efforts.

Much appreciated once again

Mal

Whilst on the subject GPX.....can I digress slightly and ask about the "tune" button on the 4500.....
If you do the 180 degree when the unit is switched on and you don't get any change in signal....is it neccessary to press the tune button......as yet I have not heard any change when I do the "180".
However, when I press the tune (just for the exercise) the base signal changes pitch.
Just curious.........
Thanks.

sandy2010 wrote:Whilst on the subject GPX.....can I digress slightly and ask about the "tune" button on the 4500.....
If you do the 180 degree when the unit is switched on and you don't get any change in signal....is it neccessary to press the tune button......as yet I have not heard any change when I do the "180".
However, when I press the tune (just for the exercise) the base signal changes pitch.
Just curious.........
Thanks.

I only ever do the 360 deg tune method when the threshold is warbling away like a Tom Cat on a hot tin fence!! To get an accurate as possible Auto Tune bump the Gain up flat out, increase the Motion to Fast and the Stabilizer to 20, then with the coil at right angles to the ground and the detector stem held out in front of yourself hip height off the ground do a 360 deg turn listening to the threshold, once the noisiest section is ascertained hold the detector still at that point and press the Auto Tune button, let the detector go through the process then listen to the threshold, manually turning the Tune control from within the menu to get it just right, then revert the Gain, Stabilizer and Motion settings to original settings.

Hope this helps,

JP

MANY THANKS FOR THE INFO JP............