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Noise the enemy of detectorists

15 Oct 2010

The first thing new comers to detecting will learn is, detectors are all about noise; they can seem like a talkative child who rambles on incessantly with the poor listener not being able to make head or tail of what it is they are trying to say. Noise or the lack of it is one of the main reasons why Minelab have what is considered to be the “World’s Best Metal Detection Technologies”. In my first blog as a guest writer for Treasure Talk I want to talk about noise and why I feel the lack of it makes the GPX 5000 so unique.

Stability in a metal detector is important for two reasons, one is user fatigue (spurious noises are frustrating and very tiring especially over long periods of time) and the other is, any sort of audio response that is not generated by a good target has the potential to mask or hide a gold nugget in the ground.

During testing I always try to re-visit areas that have been productive in the past to get a gauge on the overall performance compared to previous models, there is no better indication of an improvement in design than finding nuggets in an area you’re intimately familiar with. The first and most obvious thing I noticed with the GPX 5000 is it runs noticeably quieter than the GPX 4500 in all timings not just the new Fine Gold timings (Smooth, Enhance and Fine Gold are all in the same family of timings that effectively ignore mineralisation with Monoloop coils). In one instance I managed to find an ounce of gold missed on previous passes with the older detector. As I became more familiar with the GPX 5000 I started to ask myself the question “why are all these nuggets still in the ground?”

gpx 5000 metal detector gold

In the end I came to the conclusion that it is noise or the lack of it that allowed me to find those nuggets, the GPX 5000 was running so quiet and stable that I was able to easily identify signals missed on previous passes with other units.

The GPX series of detectors offer a range of options for the operator, those options allow the end user to make choices on the way the detector behaves. Learning to optimise the detector so it has maximum performance and minimum noise in a given environment is what operators should be aiming for. Minelab cannot make those decisions for you because each location is unique to you, but they can provide options in the detector to give you the tools to maximise your chances of success, discovering what those options do is part of the learning curve.

These are the settings I used with a Monoloop coil in quiet ground. If the ground is mineralised (noisy) then all you have to do is change the timings switch to either Enhance or Fine Gold and the Tracking switch to Fixed using the Quick Trak button to re-ground balance, you can also elevate the Gain if conditions allow.

Front Panel:
Ground Balance: Tracking
Coil/RX: DD
Soil/Timings: Normal
Search Mode: General

Menu:
Backlight: Off (saves a smidgen on battery power)
Battery Test: Battery charged every day
Volume Limit: 10 (with speaker use it is best to go lower than FP to help prevent oscillation)
GB Type: General
Special: Not relevant as Normal is selected on Front Panel (I leave mine in Fine Gold)
Manual Tune: 98

General:
Motion: Slow
RX Gain: 11(FP) to 13 depending on conditions (I rarely go higher than 14, more gain can equal more noise)
Audio: Deep
Audio Tone: 63
Stabilizer: 8
Signal: 19 (higher Tone is better suited to higher Signal settings)
Target Volume: 8 with external booster and speaker, 12 using inbuilt battery booster and speaker
Response: Normal
Tracking: Medium
Iron Reject: Off (discrimination doesn’t work with Monoloop coils)

Jonathan Porter

Comments

Johathan Hi,I own 2 Minelabs GPX,s, I have also a couple of your well presented DVD,s and in keeping with the accurate detail in them I assume that even with a Monoloop coil on you still have the Front Panel setting to Coil/RX:DD ?
Posted By: Che on October 16, 2010 07:45pm
Hello Che, it all depends on the conditions at the time, I've now found with the GPX 5000, Mono mode runs very stable compared to DD and as such I tend to find myself using Mono mode a lot these days. However this might change once our weather patterns start to settle down, of late we have had nation wide weather systems dropping a lot of rain combined with large storm cells which doesn't help detecting conditions.
Posted By: Jonathan Porter on October 18, 2010 11:36am
Hi JP, are these settings for the GPX 5000 only or can you use them on the GPX-4500. Am a newbie who has just bought a new GPX-4500 after using a mates GP 3000 earlier this year.
Posted By: flyboymickey on October 18, 2010 02:39pm
Hello Flyboymickey, yes those settings will work fine with the GPX-4500. The only differences are in the Gain with the Factory Preset in the General search mode of the GPX-4500 being 8 and the lack of Fine Gold timings.

If conditions allow you can use the Gain up to 10 or even 11 without too many issues so long as you keep the Motion settings near Slow or even Very Slow. Usually I would prefer to back off the Gain first before slowing down the Motion though.
Posted By: Jonathan Porter on October 18, 2010 03:13pm
Hello Johathan, iv was wondering if u might be able to offer some insight and encouragement.
Iv spent most my life working in the bush and id love to take up Gold prospecting as a hobby but was wondering how viable could it be and if it can be more than a hobby. Its my dream to work in the bush and be my own boss some day. Is it a gamble or with the right equipment and training could u make it a career
Posted By: Cabe on October 18, 2010 08:01pm
Cabe, this is a curly question that I am often asked. Generally I would advise against trying to detect for a living unless you are prepared to have some lean times and don't mind roughing it for weeks on end.

If after these comments you still want to take a crack at it then I suggest before you do so become as proficient with your detector as possible. As an example during a detecting season (which these days generally lasts from 3 to 6 months during the winter months) I'll only have a handful of goldless days, assuming of course I am in country where a few bits can be had on occasion.

So in the mean time before quitting your job and heading for the wide blue yonder get yourself up to scratch by regularly finding gold in close to home areas during weekends/holidays etc, to give yourself the best chance of success. This also includes researching prospective areas for future lengthy trips away, attending training days and seminars and perhaps joining a club or group of people who don't mind showing you the ropes.

It can be done but I always recommend caution, with gold sitting on record highs at the moment (over AU$44.00 per gram at time of writing) you don't need a lot every day to make ends meet, but starting out from scratch would be a lot to ask unless you had something behind you and did not need to find gold straight away.

A lot of semi-retired and fully retired Australians (Grey Nomads as they are becoming fondly known as now) are supplementing their incomes with their Minelab metal detectors, I don't see why you shouldn't be able to too once you become more experienced with your detector and get to know some of the haunts.

Are there any "Grey Nomads" (or not so grey like myself:-)) lurking on this blog who are supplementing their incomes with the gold they find with their Minelabs? It would be interesting to read of your experiences.
Posted By: Jonathan Porter on October 19, 2010 03:20pm
Thanks Jonathan, thank u for ur truthfulness but encouraging words im still super keen to get out there and give it a red hot go as soon as i can but i will be researching and fine tuning my skills well before i turn my hobby into a possible career.

Cheers.
Posted By: Cabe on October 19, 2010 07:25pm
That's good to hear Cabe, that way you're fully prepared when you decide to make the sea change :-)
Posted By: Jonathan Porter on October 20, 2010 10:39am
Thanks for your great first post here Jonathan. I find that noise is more of concern to me than targets are. I worry when people turn the gain up so high in order to increase the target response without being concerned about what it does to the noise.
Posted By: Phil on October 25, 2010 09:28am
Phil you are so right, I often see this with detector operators where they will dumb down the detector rather than give up on elevated Gain settings. To my way of thinking it is not the loudness of the response that is important but the obviousness of the response instead, in other words how well the signal stands out from the background noise.

It would be nice to have a suggested Gain level indicator for the GPX 5000 similar to the E-Trac which measures the ground conditions in real time making suggestions for the Gain levels as you go, this would give operators a clearer idea of where to set the Gain rather than taking a guess and potentially ramping it up too much.
Posted By: Jonathan Porter on October 25, 2010 05:12pm
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