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Author Topic: new mod settings on 4500  (Read 9155 times)

shepcal@sti.net

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new mod settings on 4500
« on: November 28, 2016, 11:51:54 am »
Getting ready for second trip to Q for this year with latest mods on my 4500. Last month there, I did as you suggested- went to factory default settings, run in normal, set rear gain at 5, was able to set front gain almost at max. I noticed I was able to lower threshold to 11:30-12 o’clock and still have smooth threshold (before, I needed to run at 1-1:30 to be smooth).
   I’m running the 12” EVO coil. Quartzsite is pretty neutral as far as mineralization. As suggested, hit areas I found gold before and dig up what I missed. I’m king of one nugget patches and when I find a nugget, I grid- no gold last trip. Being honest, wasn’t out for long days cause it was bloody too hot for this ol ass. My first target was foil at close to 2’ down (had to go back to camp to get pin-pointer to confirm it wasn’t in sidewall of hole and it wasn’t). Believe, I just didn’t over any gold. Dug some pretty deep small targets tho, slivers of lead, minute pieces of rust.
   The 12” EVO is all I ran last month. This next trip, I am going to start off with the NF 20” RM. My thoughts on settings: smooth signal is an absolute must! Low mineralization, so set front gain at max, back gain at 5, if smooth run back gain up a notch or two, when it gets a bit scratchy, lower front gain till smooth. When I work an area with the 20”, if I get a good target, I’ll mark and come back with the 12”.
   Any suggestions or recommendations?


Joeboy

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Re: new mod settings on 4500
« Reply #1 on: December 05, 2016, 10:48:41 pm »
I like the 20" mono its a good coil, i use to walk around detecting with it lapping my swing about half the coil. Than realised one day i was only giving my self only about 50% chance of hitting a big nugget at depth by doing that. Now when i use a big coil like that, i only increase my lap by a quarter or 1/3  so i dont miss anything deep at the narrow end, hey good luck in Q hope you find a bit.
Joeboy.

woody

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Re: new mod settings on 4500
« Reply #2 on: December 16, 2016, 06:12:43 pm »
I was out today playing with a 25" NFA Mono and comparing to a 15" FWE  and I am gobsmacked that the 15" could get far better response on 18" and 24" targets of various sizes.

I was at the Laanacoorie test site and I was really struggling to get a signal at 3'6" with the 20" mono, the 15" Evo could cot hear the target, a standard detector was hard pushed to hear anything at 3' deep.

Joeboy

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Re: new mod settings on 4500
« Reply #3 on: December 17, 2016, 06:20:39 pm »
Gday what is a 15" FWE ?

woody

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Re: new mod settings on 4500
« Reply #4 on: December 17, 2016, 07:21:21 pm »
Flat wound evolution.

Joeboy

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Re: new mod settings on 4500
« Reply #5 on: December 17, 2016, 08:12:51 pm »
That is a surprise 25" not as good as the 15 evo! At 40% bigger you'd expect the opposite. I ran some tests a while ago with my 14 elite vs 18 elite on a stock 45, wasn't expecting a big difference between them on a 3 ounce. A bit over 6" increase in depth using the 18" elite. Pretty good i say.

woody

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Re: new mod settings on 4500
« Reply #6 on: December 19, 2016, 10:04:22 am »
Some pointers on the new mods on the GPX detectors.

The manual frequency (tune) control on the back lcd panel is now made into a frequency control that can adjust the transmitter pulse to smaller or larger values, massively greater than the adjustment range in a factory standard detector.

Setting the manual tune to low numbers is perfect for really big coils as longer pulses can energise bigger gold at depth to get a larger return signal, lower numbers also allow you to use more gain as the extra long pulse on transmit is also matched by longer off time before the receiver turns on allowing most ground noise and hot rocks to fall out of the detection window, longer off times are detrimental to finding small gold.

When setting the manual tuning higher there are a number of factors to take into account, the manual tuning has a limit that is governened by how good the coil that you are using is made, it needs low capacitance to decay faster than the receiver turns on, a slow decaying coil will allow back emf into the receiver in the detector and kill the performance. I always say test the setting on a test target to make sure that you are not cranking everthing up but killing the performance, it is a bit like driving on wet roads, gentle on the accelerator.

When using high frequency numbers on the manual tuning using too much gain ( either the one we add or the gain in the back menu) can allow too much ground noise into the detector and jam the electronics in such a way that it will not respond to metal targets. It "ALL" depends on the type of ground and type of coil. On non mineralised soil the main problem is the coil, on very hot ground the main problem is ground noise.

In normal timings the detector is far more forgiving when you crank up the gain and frequency but beware some hot rocks will also be more detectable but you can lower the frequency to reduce the respone or if there are many just ground balance on a known hot rock and lock the detector into fixed tracking, this will eliminate all hot rocks with the same characteristics but also gold with similar decay as the hot rocks, you would need to be careful doing this but it can make undetectable areas detectable.

The higher numbers are pushing the limits of the GPX and GP detector technologies, the higher frequencies do not work the same in all modes , especial fine gold on a GPX 5000 as fine gold already seems to switch the receiver on faster and thus you cannot crank up the gain and frequency with high capacitance coils as the detector will go deaf.

Minelab make these detectors in such a way that the operator cannot get into trouble by putting fixed limits on the gain and fixing the frequeny. By knowing what you are doing and by changing these fixtures greater performance can be obtained. My own tests indicate that using high numbers in the manual tuning small gold sensitivity is greatly enhanced, specimen gold can be detected that normally would be ignored, greater ground control can be obtained by matching the front end gain to the ground type and adjusting to just remove excessive ground growning while swinging the coil.

So these are the things that need to be considered, ground type, coil type, gain settings both front and back, the front one we add is far more important than the one in the back menu, i always say put the back one on say 5 or around that number but it is not hard science, it is only a suggestion to get you started , i have seen operators use it at 18 and turn the front one down to work non mineral soils in high emi areas, i have seen professional prospectors turn the back gain to 1 and the front nearly all the way up using fine gold but using a lower frequency.

The correct way to understand the moddifications is to test the detector with the coils and ground type, there are so many variables that it is impossible to write up settings due to all variables.  As an example i use a 14" mono coil with back gain on 6 and front gain about half in normal mode and frequency of around 160 around Ballarat, when I go to Dunolly i use back gain on 8 and lower the front gain to 1/3 and the frequency to 120 but this is based on the ground type.  At the end of the day you need to buy a test target in the ground and test the settings to see what is the best, after a while you will master the controls and get more gold.

Joeboy

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Re: new mod settings on 4500
« Reply #7 on: December 19, 2016, 06:37:42 pm »
Hi Peter how would someone with out any tech background identify if a coil is of low or high capacitance, Is it by design.
Regards Joeboy.

woody

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Re: new mod settings on 4500
« Reply #8 on: December 19, 2016, 06:55:21 pm »
It is nearly impossible without testing equipment, the easiest way is to connect the coil to a variable frequency source and connect a small resistor in series with one coil wire and vary the frequency with an oscilloscope across the resistor, when resonance is achieved the signal voltage across the resistor will rise. The higher you can get the frequency the better in most cases but other effects like ringing need to be observed. Another way is to buy an automatic LCR type meter and measure the inductance, these give a Q reading, the higher the Q the better in most cases.

Joeboy

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Re: new mod settings on 4500
« Reply #9 on: December 19, 2016, 07:44:02 pm »
Cheers Peter, didnt think it would be easy.
Definitely a good thing to know about tho, like you said it would make a big difference how high you can effectively run frequency and gain. I assume the flat wound coils being so sensitive to tiny bits, are low capacitance.

filternozzle17

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Re: new mod settings on 4500
« Reply #10 on: August 06, 2017, 08:37:21 pm »
It is nearly impossible without testing equipment, the easiest way is to connect the coil to a variable frequency source and connect a small resistor in series with one coil wire and vary the frequency with an oscilloscope across the resistor, when resonance is achieved the signal voltage across the resistor will rise. The higher you can get the frequency the better in most cases but other effects like ringing need to be observed. Another way is to buy an automatic LCR type meter and measure the inductance, these give a Q reading, the higher the Q the better in most cases.

Would this type of LCR meter be okay to use:

UT600 series RCL meter is a kind of 3.5-bithandheld digital meter with stable performance, safety, reliability, highaccuracy and manual range.
It can be used to measure the magnification times β of audion, diode forward voltage drop and circuit continuity.
UT 603 is applicable to testingresistance, capacitance and inductance of electronic laboratory, productionline, maintenance point and teaching.
It is the ideal tool of maintaining formany users.
Specification:
Resistance (Ω): 200Ω/2KΩ/20KΩ/200KΩ/2MΩ/20MΩ Best Accuracy: ±(0.8%+1)
Capacitance (C):2nF/20nF/200nF/2uF/20uF/200uF/600uF Best Accuracy: ±(1%+5)
Inductance (H): 2mH/20mH/200mH/2H/20H Best Accuracy: ±(2%+8)
Features:
Display Count:1999
Manual Range: √
Diode: √
Transistor: √
Continuity Buzzer: √
Low Battery Indication: √

woody

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Re: new mod settings on 4500
« Reply #11 on: August 06, 2017, 10:38:36 pm »
You need the inductance to measure down into uh. Not mh.

filternozzle17

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Re: new mod settings on 4500
« Reply #12 on: August 07, 2017, 09:16:25 am »
You need the inductance to measure down into uh. Not mh.

Will this one do the job:

Modle:LC100-A
Effective display digits: 4 digits
Interface: Mini USB interface and 5.5DC Socket
Capacitance measuring range: 0.01 pF to 10uF
The minimum resolution: 0.01 pF
Inductance measuring range: 0.001 uH to 100mH
Big inductance measuring range: 0.001 mH to 100H
The minimum resolution: 0.001uH
Measurement accuracy:1 percent
LCD display mode: 1602
Test frequency range: L/C about 500KHZ Big inductance 500HZ
Size:3.15x1.97x0.82 inch
Pls reset to zero before testing
Test frequency of this item is higher, it is not suitable for measuring the electrolytic capacitor
Package include:
1x High precision L/C meter board
1x mini usb power cable

woody

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Re: new mod settings on 4500
« Reply #13 on: August 07, 2017, 10:10:02 am »
Total overkill , but if its cheap...