The new Nugget Finder XP coils have been available for a while now and some good information is starting to filter back down from end users on their performance. The following is a few things I have noticed during my short time with one and also feedback from the Rohan Johnson at the factory here in Australia, Chris Gholson at AZO and various other users around the world who have contacted me personally.

Firstly it needs to be understood how the XP concept came about; through experimentation Nugget Finder Australia discovered that an initial raise in pitch on any target was a far more readily identifiable target response especially in highly mineralised ground. So every Nugget Finder DD that left the factory from serial number 5000 onwards was a dedicated XP coil (this enhanced the larger targets). As you can imagine this helped in the discovery of some very impressive finds (see the latest Gold Gem and Treasure Magazine).

If you cast your mind back to the beginning of the year you will probably recall a five ounce slug I found with a Nugget Finder SL 20”DD on the prototype GP3500, what I didn’t know at the time was that is was an XP variant coil. Funnily enough Rohan informed me I was the only one outside of the factory who actually commented about the reverse signal response on large targets at depth. The reason the information wasn’t made public was because Nugget Finder had the switchable option already in the design stage to help compensate for a lack of good sensitivity to small nuggets which the XP variants lacked. Rather than market two coil types and run the risk of alienating customers by forcing them to purchase two separate coils Nugget Finder decided to do something that has never been done before and provide us the end user the option of obtaining both versions in the one purchase, hence the totally new XP switchable DD coil.

One of the true powers of a Minelab PI detector is the fact that they have two channels working in conjunction with each other, where one is least sensitive the other is most sensitive. The raising and lowering signal response is dictated by which channel is the most sensitive, eg; if it is a large target at depth the channel that makes the lowering and then raising response will sound off, and vice a versa, however if both channels are capable of making a response you will receive a confused signal which is both channels responding equally at the same time (see our video “The Outback Prospector”). This raising and lowering response is chosen by Minelab at the factory when the machine is built and could be changed around if they so wished (the SD2000 was reverse of this – high/low on large targets and low/high on small).

Rohan has discovered a way of manipulating this response by changing the phase of the coil, so you can now switch between these options to tailor your coil to suit the type of detecting you are doing. However there are always compromises and in this instance because of the shift in phase when going to XP mode you leave yourself open to a little more interference which can be confused with the coil being noisy. The other trade off with XP mode is the reduction of performance when using Cancel mode (Cancel mode is a phase change itself so I am not surprised by this).

However going by feedback I have received there have also been a few gains in performance by going with the XP option, namely an obvious increased ability to handle really hot ground but also increased depth performance when operating in XP mode and Mono mode on a GP3500 (Enhance on an extreme). I have not had the opportunity to try this out for myself but feedback both from the factory and other prospectors is very positive.

To sum up, the phase change is an option that no other coil manufacturer has ever attempted; I would advise most detector operators to use the Normal mode for probably 70% of the time depending on the terrain as it provides the best sensitivity for smaller gold and less proneness to interference. The XP/Mono mode needs to be investigated as it should provide a smoother threshold compared to DD mode and could quite easily cut back on the instability issue. It should also be noted that using XP mode won’t always cause your machine to become noisy, the interference type has to be present in the first place to cause it and can be tuned out to a certain extent when it does.

XP mode is dynamite on large nuggets in extreme ground types, tests have proven this conclusively in some of the worst ground in Australia. It would probably pay to reinvestigate any favourite areas that have been too noisy in the past as I have been told nuggets have been recovered at only moderate depths in well detected areas that did not present a recognizable response in normal mode.

When changing phases (either XP to Normal or vice a versa) you should turn off your machine. When going into XP mode, use the Minelab recommended tune procedure first to establish if any major interference is present then once the direction has been established place the unit on the ground with the coil flat and hit the tune button. Once this has been done you can then fine tune the frequency (if you have a 3500) to clean things up even more.

If the noise is still too much for you then revert to normal mode, you still have incredible performance thanks to the superior design set of the Nugget Finder DD range. I would also advise you to take a few different sized targets and learn how the different responses sound (high/low, low/high), having said that I am not of the opinion burying targets is a good way to go especially with a DD coil as it can give inconsistent results.

Hope this has helped clarify the New Nugget Finder XP range

JP © Jonathan Porter 2005

Nugget Finder XP Report courtesy of aurumaustralis producers of the 'Outback Prospector' and 'The Latest Update' instructional DVD