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GPZ 19 compared to GPZ 14 - Nugget Dig!

30 Mar 2017

Like all things new, it takes time for results to feed back into the general community. Overall, there have been some very good reports from people using the GPZ 19 coil. Early adopters who have been tough enough to brave the heat of summer here in Australia have been reaping the rewards, as well as fast-tracking their experience levels for when the weather cools off, come Easter time…

Late last year, on Christmas Eve, I woke to a cool morning with cloud cover and some spare time on my hands, so I got up before the sun and headed for one of my test patches in one of the Clermont General Permission areas here in Central QLD. (You can find maps of these General Permission areas and access requirements on the Queensland government website: https://www.qld.gov.au/recreation/activities/fossicking/central-gold/)

My chosen location has produced a lot of gold for me over the years and is one of my favourite sites to test new equipment, as I am extremely familiar with the area. Finding gold there with new equipment means there is an improvement in performance over what I’ve used previously, especially due to the intimate knowledge I have of this site.

GPZ19 compared to GPZ14 Nugget Dig

This location is extremely variable and mineralized. The old-timers potholed and surfaced it back in the late 1860’s and, since the advent of metal detectors, it has continued to produce ‘sluggy’ gold to this day, particularly since the SD 2000 was released in 1995. I first started testing metal detectors here in 1996 and have revisited the location hundreds of times over the years, the most productive years for me being with the GPX-4500 and the Enhance timings.

On this occasion, I had a clear goal in mind: I was chasing the deeper more solid nuggets, so to that end, I was prepared to only get one signal all morning or even no targets at all. For heavy ‘shotty’ gold General/Difficult is the GO-TO mode: it provides a clear advantage over High Yield/Difficult in noisy variable ground and is the mode I HIGHLY recommend for GPZ 7000/GPZ 19 users in Victoria and W.A. where:

  • the gold-bearing soil can be deep;
  • surface minerals are highly mineralized and variable;
  • the gold tends to be heavy and solid in nature.

General/Difficult tends to ‘kick in’ on nugget sizes from around 10 grams and up, depending on shape and depth.  Conversely, High Yield is very good at detecting the tiny nuggets and specimen gold. 

It took me four hours to lock onto a suspect target response at the base of a tree right up under the edge of an old boy’s digger hole. Initially the response was extremely faint, just like someone twanging the surface tension of water without breaking through, causing a ripple like waver in the threshold that would not go away. After digging away and widening the hole, the signal improved and I soon realized this was a golden opportunity to compare the GPZ 14 coil against the GPZ 19, so I went back to the 4x4 and grabbed the smaller coil and my smartphone so I could film the event. Holding a smartphone, whilst swinging the GPZ 19 one-handed, is no easy task, so I apologize for the shaky footage! It is also very hard to convey the distances of the coil sweep over the target when filming from above, but experienced users should be able to easily see the differences between the modes and coils.

What is of particular importance is the performance difference between the two coil sizes. Minelab have claimed an “Average 30%” depth advantage of the GPZ 19 coil over the GPZ 14. In this case the video easily shows the depth advantage, which, in some cases, can be a lot more! You will notice in the edit I have not cut the “swing over target” footage when comparing modes except between coil changes. The comparison footage is shown in real time without edits.
(I would also like to point out that even though General/Normal was providing a reasonable signal response, the Normal Ground Type is not really practically usable at this specific site due to the extreme variableness of the ground.)

GPZ19 compared to GPZ14 Nugget DigAll modes were individually Ferrite balanced and a local Ground Balance (GB) was also achieved. My preferred method is to ‘pump’ the coil between changing modes. This is to fine tune the GB which was set in Auto. In situations like this, once it’s been decided to dig, I highly recommend operators to pre-configure the USER button of the GPZ 7000 to the Ground Balance function and once balanced, FIX the GB by placing it in Manual. If you pay careful attention to the footage you can hear the Auto GB taking the edge off the target response after repeated swinging of the coil. This is especially noticeable with the GPZ 19 coil and the settings that produced the weakest signal response.

So take a look at the video! I got a massive ‘buzz’ out of the difference in signal response between the two coil sizes…

If I’d only had the GPZ 14 coil on that day, that nugget would still be in the ground. It makes me wonder what else I‘ve missed at other locations around Australia!

GPZ19 compared to GPZ14 Nugget DigThe nugget was recovered at 22+ inches depth, weighed in at touch over 26-grams and was a beautiful water-worn crystalline “Herring Bone” nugget. A few days after Christmas I returned to the location and scored a fantastic 30-gram piece right out in the open with dig holes all around. I know for a fact that I have had my GPZ 14 coil over this exact ground, and only very recently. The signal was a real eye popper and what I would call an easy “dig me” response; more proof the GPZ 19 coil is providing an ‘edge’ over the GPZ 14 when the gold is present. On New Year’s Day I returned in 40 degree Celsius temperature and ‘nailed’ a solid little 12-gram slug at reasonable depth, taking my total for 12 hours detecting at this location to a tad over 2-ounces!

The GPZ 19 coil requires commitment and an understanding of the right locations required to see its advantages, it is not a prospecting tool to improve coverage unless you’re strong of arm. The real benefits are in the deeper soils, chasing the ‘sluggy’ pieces. However, I’ve also done well in High Yield chasing large specimen gold and Enrichment type deposits. In Normal Ground Type and quieter soils, it is mind-boggling how deep the GPZ 19 detects and also surprising how sensitive it still is on the smaller stuff, but it does require INPUT AND EFFORT from the operator to achieve these results. I’ll be swinging the GPZ 19 coil a lot more this coming winter – will you?

Jonathan Porter

Aurum Australis

To read more about the GPZ 19 Super-D coil, click here.

Comments

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great video mr p thanks for taking the time on your report & filming some great info there just go's to show how good the 19 inch coil really is
cheers bob
Posted By: bob f 57 on March 31, 2017 04:50pm
Thanks for the great video JP. Excuse my ignorance but what do you mean by "Enrichment type deposits"? Is this a reference to the finer non-nuggety reef gold?

Regards

Col
Posted By: Col Douglas on April 01, 2017 02:11pm
Thanks for passing on some tips. on your video what settings are you using to use with general/difficult?
Cheers.
Posted By: bradlook on April 03, 2017 06:17pm
Hi Col, enrichment just means a reef like gold deposit. Not all sources of alluvial gold are in quartz reef like structures but instead are in iron rich rocks associated or in contact with quartz reefs, in this case the gold was in a blend of quartz and ironstone hence the term Enrichment rather than reef.

Enrichment's tend to be a mass of gold with nothing more at depth, just a clump or enriched matrix (quartz and Ironstone) sections in rotten country rock where the gold has been formed, perfect for a metal detector like the GPZ 7000.

Hope this helps
JP
Posted By: Jonathan Porter on April 04, 2017 06:05am
Hi bradlock, my settings are as follows when chasing larger nuggets in noisy ground with the GPZ19 coil. I use a B&Z booster through twin speakers for the audio so the Volume settings are lower than what is need with the WM12 speaker only.

Audio Smoothing OFF
Sensitivity 9
Target Volume 8
Volume Limit 10
Threshold 27
Tone 60
Ground Balance Auto
Ground Type Difficult
Gold Mode General

For more info on the B&Z Booster go here....
http://outbackprospector.com.au/b-z-booster/

The booster is needed to cleanly amplify the audio so the speakers can be heard, the B&Z has plenty of volume control without much distortion.

Hope this helps
JP
Posted By: Jonathan Porter on April 05, 2017 05:47am
Thanks JP.

Col
Posted By: Col Douglas on April 05, 2017 06:44am
Hi JP,
Firstly,
I love your posts and videos, keep up the fantastic work.
I was hoping you might be able to clear somethings up for me please.
When you GB,
Do you do the "walk and sweep" method and then "ferrite balance"?
or
Can you only pick one method?
IF only one method allowed, then how do you decide which one to use?
Also, is there any "list" so to speak of showing different gold modes and ground types combinations to help know what depths and sizes you are targeting?
Eg,
HY/Normal = ? Hy/Difficult = ? Hy/Severe = ?
General/Normal = ? General/Difficult = ? General/Severe = ?
ExtraDeep/Normal = ? ExtraDeep/Difficult = ? ExtraDeep/Severe = ?

I have found "info" regarding settings for large deep nuggets but what if I also wanted to check for small shallow gold?
What settings would suit small, shallow bits?

Sorry to ask so much in one go :)
Posted By: madhatter on May 21, 2017 09:39pm
Hi madhatter, it is best to always use the ferrite when performing the GB process. Usually I place the ferrite on the ground and swing over the ferrite using the recommended figure 8 procedure with Quick-Trak button engaged then pump the coil up and down to one side with Quick-Trak released. When there is no ground signal with the pumping action I then swing the coil back over the ferrite again to confirm if has been balanced out totally, if not then hold in Quick-Trak and perform the whole process again. When Quick-Trak is engaged the detector is expecting to balance out ground and the ferrite all at the same time so its usually best to expose the detector to both evenly. Only use the walk and swing method if you do not have a ferrite.

Gold modes should be seen as a guide to the target size you are seeking, so High Yield is best for smaller nuggets, General is as the name suggests better for smaller through to larger pieces and Extra Deep is not so good on tiny gold but still has good depth on big nuggets.

Ground Type mode is dictated by the severity of the ground you are operating in, in the case of the GPZ there are few places where Normal can be used exclusively especially in Australia so Difficult is the main stay of most operators here, there is a fair amount of difference in target response between the High Yield and General when in the Difficult mode, so around the 8 gram mark General can generate a better response compared to High Yield especially if the nugget is solid and dense. The GPZ tends to not look at the weight of a target but more its surface area and how well it grabs the transmit field, so if a target is roughish in nature it will lend itself better to giving a better response in High Yield, whereas General can give a much better response on more solid pieces that capture the transmit signal more readily. (as per the video)

In Normal Ground Type modes the difference is not so pronounced and tends to come down to the level of ground signal, High Yield will be a tad noisier than General in Normal modes. High Yield will however provide less EMI like responses so can be handy to use in proximity to other GPZ users and EMI days/areas.

General does provide very good sensitivity to smaller gold but you have to listen carefully. Best bet is to go over the ground in both modes to make sure you have covered all the bases.

Good luck out there
JP
Posted By: Jonathan Porter on May 23, 2017 06:17am
Thank you for posting your B&Z settings on this post JP, I purchases one for my 5000 that I've not setup/used as of yet and with my purchase of the 7000, am going to set it up on that machine instead and your info helps.. thanks again for a great video....
Jennifer Bond
Posted By: Jennifer on August 06, 2017 07:06am

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