In the field with the GPZ 19 Coil

I have been swinging the GPZ 7000 19” coil now for over 6 months, so I feel a bit more informed to share some thoughts on the coil, how it compares to the stock 14x13” coil, and what detector settings have been working for me.

Ergonomics

First up – yes, the coil is not super light.  It is a big coil, with a lot of wire inside, so yes, it is going to be heavy.  However, with a few adjustments, and a little time getting used to it you should be able to swing it for extended periods.  Here are a few tips that can help - you may want to use all or just some of these, so just experiment and see what works best for you:

1. Use the swing arm, as this will transfer some of the load to your other arm.  It also helps to maintain proper coil control - keeping the coil parallel to the ground and at a consistent height.
2. Use both J-Struts in the harness and the cross piece.  This will transfer the tension of the bungy cord across both sides of your waist.
3. Put a drink bottle in the optional battery pouch.  You should always carry water with you, especially when expecting to dig big holes, but this will also help to keep your harness in position.
4. I've used the coil with my normal set-up of no swing arm and just one J-Strut and this works fine on flat terrain with no obstacles.  For harder terrain, the use of a thicker/longer bungy and wrapping the bungy around the top of the handle is working well.  This also aids in proper coil control.
5. Some users prefer the use of a Hip stick in place of the J-Strut, which allows the use of different backpacks, but I am more than happy with the Pro-Swing harness.  Once adjusted correctly they are great to use.
6. There is also an aftermarket solid skid plate available for the GPZ 19.  This allows the coil to glide across rocks and sticks with relative ease, which makes using it much more enjoyable. The only negative is that debris will get stuck in the top, so you will need to regularly tip the coil upside down to clean it out.

After a while of experimenting and trying different set-ups, my preferred method is to use a longer heavy duty bungy cord which is strapped on under the lower shaft clip.  It helps to maintain an even coil height above the ground, and has even stretch so you don’t get the harness pulling in any direction.  With the bungy and flat bottom skid plate, the GPZ 19 has become my primary coil when using the GPZ 7000 in open ground.  The other benefit of the longer bungy mounted closer to the coil is that when you bend down to recover a shallow target you don't have to unclip it.  With this set-up, on relatively flat terrain I’m finding that I can handle the coil for many hours no problem.  Just remember, we all have different body geometry, so what is working for me may not be ideal for you.

Settings In The Field

With the GPZ 14, I tried not to overthink my settings, so my general setting-up process was:

1. Try Normal Ground Type - can it work?
2. Nope, okay into Difficult.
3. Start with HY and see how it goes.
4. Adjust sensitivity as high as possible before the ground says stop (sometimes this is below default).
5. Now set Smoothing accordingly.

With the GPZ 19, there is still a lot of experimenting to do with different combos, but I think the thought process should be similar to the above.  You need to just turn it on and go and see where you can run it – it will rarely be the same in different locations.  It is a big coil strapped to a very powerful machine, so if there's a gram plus bit buried at depth there is a good chance we are going to hear it, but having the right settings to suit the conditions at hand can make a difference to our gold take.

After using the GPZ 19 coil in several different locations, and hitting those locations when the ground is dry, or shortly after rain, I can confidently say that the coil does behave a little differently compared to the GPZ 14.  For example, in some soils with the GPZ 14 I've found High Yield to be the go over General, but with the GPZ 19 it doesn't react as much to the ground but it can pick up more EMI particularly in High Yield, so General often provides smoother operation.  It is a big coil, and as with big coils in the past you will give up a bit of sensitivity to really small targets, but in saying that it is still very sensitive for its size.  I’ve found several pieces with it well under 0.2g.  Not that you want to find small bits all day, but I’d rather not leave them behind either.  If you are using it for general poking around, then keep it in High Yield.  If you are using it in an area you have already detected with the GPZ 14 and you suspect there may be some deeper targets lurking, then General will give you a little more punch.

In milder soils I have found that I can push the Sensitivity setting with the GPZ 19 a little higher compared to what I’d use with the GPZ 14, but in doing so I often need to select Low Smoothing to get a smoother threshold.  I try and avoid High Smoothing where possible, but if the ground allows a very high Sensitivity setting (i.e. higher than 15), and the result is more instability from EMI, then I don’t hesitate to go to High Smoothing.  I will only use High Smoothing when using headphones as the signals can be somewhat filtered out, and can be easy to miss.  In areas with higher mineralised soils and lower EMI, the combination of General, Difficult, Sensitivity below 10 and Smoothing on Low or even Off has produced very well - pinging good gold from 0.2g up to 2 grams.  When hunting in General, I use High Yield as a target checker on those iffy signals, so I always do my ferrite balance on both setting combos at the start of my session.  Early morning and very late arvo when EMI levels drop is when I’ll go into High Yield and switch Smoothing Off and this has produced a few extra colours – mainly smaller targets with a very weak response that were missed in General.

In the latest patch that I’ve been working, I have tried using High Yield / Normal with a reduced Sensitivity but the ground has been too mineralised.  This may be due to the lower layers of soil being quite moist, and this may change when the ground properly dries out.  On some deeper sections of ground I've tried General, Difficult, Volume 9, Smoothing Off, Sensitivity 7 and this has also worked well, particularly late in the arvo when EMI levels drop.  With these settings I detected a couple of nice pieces around a gram at depth right where I had gridded with the GPZ 14 a few days earlier.  My typical audio settings using headphones have been Low Smoothing, Threshold 27, Volume 10-12 (depending on wind), and Volume Limit 8.

Normal Ground Type

If you want to get maximum punch out of the GPZ 19 coil and the “Zed”, then Normal Ground Type is what really kicks the Zed into gear in my opinion.  Normal is best utilised in milder soil types, and Sensitivity will need to be set to suit conditions.  Don’t be afraid to drop it fairly low, as if you can get it to run smooth enough, you will still be achieving greater punch compared to Difficult.  If you want to use Normal, but are having difficulty in High Yield or General, then the combination of Extra Deep, Normal and a lower Sensitivity can often work very well.  You will experience a loss of sensitivity to small targets with this combo (which can be a good thing at times), but the detector will still be tickling those deeper layers of soil looking for that elusive nice lump of yellow.  I haven’t found one yet, but have dug my fair share of very deep junk to know this combo will produce the goods with the GPZ 19 strapped to the end of the shaft.  If ground conditions allow, then Normal / General will give you the best punch on chunky gold over a gram, but if the gold is even slightly odd shaped or has some ironstone attached then High Yield is the go.

Final Words

As a bit of a summary, here are the Gold Mode and Ground Type combos I’d use in different scenarios:

• Highly mineralised soils with a history of reef gold – High Yield, Difficult
• Medium-High mineral soil with mixed gold types – General, Difficult
• Medium Mineralised soils with large deep gold – Extra Deep, Normal
• Mild Ground, mixed gold type with the chance of some better bits – High Yield, Normal
• Low mineralised ground with maximum depth on most targets - General, Normal

These are ideal settings, but remember you have to adapt to the conditions.  During detector training a common question I’m often asked is “How do I know I’m in mineralised ground?”  My response is always the same – “The detector will tell you.”  With the GPZ 19 coil this is more important than ever, as the emphasis should be on listening.  We can’t see what the electromagnetic field is doing, but we can hear it through the threshold and all the little nuances that go with it.  That next little threshold wobble, or slight rise in tone that doesn’t track out could be the big lump we all hope for!

For any questions, you can get in touch through my website: www.phasetechnical.com.au