GPX4500 - Depth

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GPX4500 - Depth

Post  buck06 on Tue Jan 20, 2009 7:08 pm

i feel like iam not getting much proformamce out off my 4500. i am using a 470 x 300goldstaker momo coil and i feel that my 11.. standard coil works just as good in custom mode . in hot ground cant get gain over 8 and stablizer 6 . i auto tune and set up pritty close to jp settings on his dvd but feel that i am not getting good depth from 4500 or coil any tips out there cheers buck
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Re: GPX4500 - Depth

Post  nero_design on Wed Jan 21, 2009 1:09 am

The 11" standard DD coil (Pseudo-Mono) is probably the ideal all-purpose coil and it's exceptionally useful for any type of hunting when Nuggets are the target. In hot ground, both the Gain & Stabilizer are usually not going to go above 8 without some instability and bad signal corruption involved... so that's normal.

When using non-Minelab coils, I believe a few people have noted that the third-party coils offer lighter weight yet sacrifice some degree of depth (20%?) and there's a difference in power-drain too. Since the bungee cord takes the weight from the detector/coil, weight is rarely an issue for most people - regardless of the coil used. The 470 x 300mm Goldstalker has been a popular coil because of it's light weight and possibly more so because people on YouTube can be seen using them to dig for nuggets.

You might want to look at JP's suggestions for deeper seeking settings (posted here in another thread) and be sure to consult your manual as well since most aspects of the settings are covered in detail there. Note that interference and signal-softening can (and will) occur if you are wearing metal on your belt or within several feet of the coil. If you carry a backpack, be sure to place any metal keys, blades and radios in it rather than on your hip when using anything LARGER than the 11" coil. The 11" coil plus any smaller coils are usually quite stable since they are less prone to metal and electrical interference nearby. The 11" coil may seem stable to many when compared to a larger Mono but usually that stability issue is related to the proximity of metal carried by the detectorist. These larger coils light be less sensitive to smaller nuggets but they put out an ENORMOUS electromagnetic field which extends well over 50 feet from the coil. Another thing you need to remember is that you literally have to walk over a nugget to find it with any detector (so a degree of luck is involved) and also, you need to be listening to the FAINT sounds which would herald a nugget at depth. If you ONLY dig louder targets, you will only find larger items (often junk) at depth or smaller junk near the surface. They give up the loudest tones in most cases. Gold is most often quite faint until you scrape away an inch of topsoil from over the target and rescan it. If you are digging small lead targets at depth, then you ARE almost certainly listening to the detector correctly. But the larger coils will often ignore smaller nuggets under 1.5 grams and so the likelihood of finding a large nugget is diminished statistically since the likely number of subgram nuggets exceeds the multi gram nuggets by a ratio of over 1000 to 1.

Cheers,

Marco
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Re: GPX4500 - Depth

Post  Jonathan Porter on Wed Jan 21, 2009 7:37 am

buck06 wrote:i feel like iam not getting much proformamce out off my 4500. i am using a 470 x 300goldstaker momo coil and i feel that my 11.. standard coil works just as good in custom mode . in hot ground cant get gain over 8 and stablizer 6 . i auto tune and set up pritty close to jp settings on his dvd but feel that i am not getting good depth from 4500 or coil any tips out there cheers buck

Depth is relative, it all depends on the ground conditions you are detecting in, the type and size of coil you are using and the settings you have implemented on your machine. It is a little hard to offer advice on exactly what settings you are using in "Custom Mode" because there is a plethora of choices available, is it the "High Mineral" preset for instance or something else? All the Search Mode options on the GPX-4500 are user configurable, for instance after a "Reset Default" procedure on my 4500 the Custom Search Mode choice comes up with Hi-Mineral when I select the Custom search mode switch position on the front end cap, is this the mode you feel is getting better depth with the standard 11" over suggestions I have made in the video for Monoloops?

Depth can be confused sometimes with the way the detector is set up, for instance if you have the Volume controls way down then the response coming from the machine will sound very faint which could suggest the detector has limited depth, however once the settings have been corrected the response can be heard loud and clear. Looking at the settings in the Factory Preset of Custom mode, the Gain is set at 6 (a little on the low side) but the Motion is set at Medium (a little on the high side) but what is of main concern to me is the Audio is set on Boost which will make signals stand out much clearer but will also tend to make the unit noisy in hot ground (hence the lower Gain setting of 6). Now because you have been using the supplied standard DD coil the coil will handle a lot of the mineralisation noises so will seem to be quite bright on target responses, however you have knocked off a fair bit of performance by electing to use a lower Gain setting.

Lets break the detector up into a few components, first there are the timings, these are the power tools of the detector that allows you the operator to deal with the vast majority of ground types you are likely to encounter in Australian Gold Fields. These timings are designed to be used with vary coil choices, for example the Smooth and Enhance timings are designed for use with Monoloop coils to provide ground ignoring capabilities better in some cases than a DD coil in noisy ground types, however there is a trade off because to get rid of ground signal you also have to get rid of some good signals too so it is advised to only use these timings in areas where the ground signal is persistent.

Next we have the choice of DD or Mono coils or even the ability to convert a DD coil to a pseudo Monoloop,
nero-design said
The 11" standard DD coil (Pseudo-Mono) ...........
(nero's comment is not quite correct, all DD coils attached to a GP series machine can be converted to a pseudo Monoloop as it is the detectors electronics that does the converting not the coil attached. However it is a very handy feature that has netted me hundreds upon hundreds of nuggets in the past).

Generally speaking I recommend new users become proficient with the supplied DD coil as it provides plenty of performance for a learner as well as the added benefit of discrimination in trashy areas.

Here are my recommendations for the use of a DD coil in medium to Mild ground types,

Front End Cap

Coil/RX DD mode
Ground Balance Tracking
Soil/Timings Special or N (Normal) (see comments on Menu choice about Timings)*
Search Mode G (General)
Threshold 1 -2 O'clock

Rear End Cap (Menu Selections)

Backlight OFF
Battery Test 8.0+v
Volume Limit 12
Ground Balance Type General
Special Sensitive Xtra *(this only becomes available if the Special switch position is selected on the Front end cap)
Manual Tune (usually when visiting a new area perform an auto tune as per the manual then fine tune from here)

Search Mode Menu

General

Motion Slow
RX Gain 8
Audio Deep
Audio Tone 62 (high Tone if your ears are good lower if any hearing damage)
Stabilizer 10
Signal 19 (use a lower Signal number if you run lower Tone)
Target Volume 8 for headphones 12 for speaker
Response Normal
Tracking Medium (this becomes disabled if Fixed is selected on the Tracking switch)
Iron Reject 4 to 5 (only use if a DD coil is attached)

To take advantage of a Monoloop coil everything can stay the same as above if the ground conditions allow, if mineralisation becomes persistent then move the Soil/Timings switch to Enhance or select Smooth in the Special menu section. For maximum depth use the Normal timings (N) on the Soil/Timings switch.

These larger coils might be less sensitive to smaller nuggets but they put out an ENORMOUS electromagnetic field which extends well over 50 feet from the coil
Just to clarify, Large Mono coils do have a reduction in sensitivity so there is no point chasing tiny nuggets in shallow ground, however they do not have the ability to sense a target 50 feet away although there magnetic field might extend that far, but they can suffer problems with interference because they are in effect a very large antennae.

Hope this helps,

JP
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Re: GPX4500 - Depth

Post  nero_design on Wed Jan 21, 2009 11:26 am

JP, hate to contradict you in any way (and perhaps my opinion on this is actually in error) but it's my understanding that the only Double-D coils guaranteed to switch to effective (Pseudo) Mono are the Commanders and that it's a myth that all DD coils will do this properly - although they certainly should. Minelab said elsewhere online they wouldn't be able to vouch for after market coils in this respect. I've spoken to a few Prospectors who, like yourself, do this for a living and they told me that not all DD's did this reliably.... just the Commanders. Since the coils are driven by the control box, I agree that all DD's should in theory be switchable.

As you've been using this feature, did you encounter a noticeable difference in depth when switching between the two modes using the same coil? I tend to switch to "Mono" when pinpointing along the edge of the coil although I've taken to using a Garret handheld Pinpointer lately to speed up the process.

One last thing, I was advised by Minelab not to tilt my coil on edge when pinpointing in Mono Mode DD or with Mono Coils. There were no specifics other than "don't do that" when they heard this is what I did to poke the edge of my coil against the soil.
Your thoughts as to why they'd ask me not to do this?


buck06: The setting posted by JP above should be ideal for your coil on Milder soil. Hot soils require similar settings (which he posted elsewhere on the forum for another member).
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Re: GPX4500 - Depth

Post  Jonathan Porter on Wed Jan 21, 2009 12:13 pm

JP, hate to contradict you in any way (and perhaps my opinion on this is actually in error) but it's my understanding that the only Double-D coils guaranteed to switch to effective (Pseudo) Mono are the Commanders and that it's a myth that all DD coils will do this properly - although they certainly should. Minelab said elsewhere online they wouldn't be able to vouch for after market coils in this respect. I've spoken to a few Prospectors who, like yourself, do this for a living and they told me that not all DD's did this reliably.... just the Commanders. Since the coils are driven by the control box, I agree that all DD's should in theory be switchable.

I have only ever come up against one coil that had difficulty switching to Mono mode on a GP machine which was a little Coiltek elliptical DD and that was a long time ago (not sure how they are now, for a laugh try the small Commander version and you will find your pinpoint method is arse about because the transmit receive is back to front compared to the other DDs in the Commander range lol! (you can tell this by where the coil cable enters/exits the coil)).

Minelab have a disclaimer suggesting the Commander DD coils be used to achieve the full effectiveness of the GP range but this does not mean that all other coils do not work. I mentioned the correction because your post implied the coil was what triggered the Pseudo Mono mode and not the electronics which is incorrect.

As you've been using this feature, did you encounter a noticeable difference in depth when switching between the two modes using the same coil?

There is quite a BIG trade off in depth when using a (Minelab or otherwise) DD coil in pseudo Mono mode, for the best depth use the coil in DD mode in Normal timings. Mono mode generates a brighter signal response compared to DD mode but also suffers from more feedback from noisy ground (although not as bad as a True Mono coil), I used the mode a lot with the larger Minelab DDs years ago in shallow mineralised ground where the Mono mode really pumped up the signal response on small shallow targets but still maintained some good handling of the mineralisation.

One last thing, I was advised by Minelab not to tilt my coil on edge when pinpointing in Mono Mode DD or with Mono Coils. There were no specifics other than "don't do that" when they heard this is what I did to poke the edge of my coil against the soil.
Your thoughts as to why they'd ask me not to do this?

When you tilt the coil out of level plane you could allow a lot more interference into the equation which can drown out a good response. I tilt the coil on edge all the time to pinpoint targets especially in a DEEP hole both with a DD in Mono mode using the left edge (or the right on the little elliptical Commander cheers ) or any edge of a Monoloop coil, so am unsure what their reasoning would be other than what I have said above. To be honest I prefer to steer clear of discussions where "Minelab supposedly said this and that" because there is too much room for misquoting/missunderstanding etc I think Minelab give pretty good advice and don't want to get hung up in a "They said this" and "You said that" debate. Embarassed
I suppose we could look at it from two angles, one is the "Minelab by the book version of fundamentalism" or the "tried and trued after many years of experience in the fieldism", either way you still end up pretty close to the mark. Cool

Respectfully,

JP
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Re: GPX4500 - Depth

Post  nero_design on Wed Jan 21, 2009 12:26 pm

Thanks JP. The proof is always in the tasting of the pudding. I try to treat the detectors and coils I've used as nothing more than effective tools for the job, regardless of brand. Your observations are much appreciated. Cheers!
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Re: GPX4500 - Depth

Post  alchemist on Wed Jan 21, 2009 1:23 pm

Hi Buck,
I just want to re-emphasize what JP said about tuning. I’ve never had good consistent results from the autotuner. Do it manually. Dial up the middle of the band 128 and then go a few clicks above or below until it quietens down, then increase your gain, and/or stabilizer, then fine tune again, and you may be able to up the gain a little more, but when you start to swing the coil you may find you will have to reduce it a bit.

I find in the areas I hunt that my tuning spot will range between 120 and 132. Of course for you it will be quite different, but in one area for instance I will often get a dead spot at 120, and begin detecting and after awhile a warble might start up, I know from experience to wind it over to 128 and all will be sweet for perhaps 5 minutes or an hour and then I will need to set it back to 120 again, sometimes a shift in wind direction will cause it to warble. This area has lots of TV, Radio, and microwave comms.

I had to note this when I read that you autotune. I didn’t get maximum performance from my machine until I started experimenting with the manual tuner.

Cheers
Grey.
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reply to the following: JP, Nero, alchemist

Post  buck06 on Sat Jan 24, 2009 9:32 am

Thanks for all the info. going out 2day to try the setting and advice. Will keep you all posted......

Good luck to all.

buck06
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Re: GPX4500 - Depth

Post  Beer Beeper on Thu Feb 26, 2009 6:20 am

nero_design wrote:
"When using non-Minelab coils, I believe a few people have noted that the third-party coils offer lighter weight yet sacrifice some degree of depth (20%?) and there's a difference in power-drain too. Since the bungee cord takes the weight from the detector/coil, weight is rarely an issue for most people - regardless of the coil used."

Not only here but I noticed you have also said this before as well that aftermarket coils(like CoilTek GoldStalker and NuggetFinder) have about 20% less depth than Minelab Commander coils, of course of the same size and winding. In other words the Commanders have about 20% more depth. I am not saying you are wrong, as you could very well be right. But has this been done in a ground test or some sort of test to prove this?? If this is true I would buy Commanders instead of the new NF Advantage coils!

P.S. Thanks for the good posts JP, Marco, and everyone.

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Re: GPX4500 - Depth

Post  Guest on Thu Feb 26, 2009 5:38 pm

I find that odd... else most pro's would be using commanders not nugget finders and coilteks.
If anything I found the opposite re: depth.
Plus the weight of the commanders was a factor even though I use a hipstick

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Re: GPX4500 - Depth

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