Testing the Modded GP's

Hi All, sorry to all those that sent me emails and messages when I went out and also thanks for the birthday greetings.

I went out as you know for around 5 weeks and took 4 detectors with me, a GP Extreme and 2 x 3000 plus my own 3500. I also built a 15 x 5 rectangular mono coil for the trip. I had 2 other people come with me, John a first timer with a modded 3000 and Mal with a 2200 modded also. The first day we had to go to a different area than I had planned and turned up nothing then we went to the next stage on a station that a mate owns in the Tuckanurra area. The first day I pinged a 1gm piece near an old workings and then sent John over to the same area and he got a 1.95gm specie with around 1.5gm of gold. So he was happy. I was using the coil I made and he was using the 11"DD in mono mode. Both detectors were running sensitive 2 and handled the mineralised ground with ease. We shifted around the station a bit and even though I used my trike to find areas we never found another piece. Poor old Mal never found anything but was a great character and was happy just to be in the bush. After a week he decided to go and we went to an old camp for a morning of detecting to see if he could get a piece. After a while he called me over to run the 3500 over a signal to see what I thought. It sounded sweet and I thought he had finally found a piece, especially after I dug 6" and still had a target. This was undisturbed deep ground. To our surprise at around 11" up pops an old .22 shell! Amazing how it got that deep! especially in flat ground with no visible erosion!

He left and John and I moved into the Cue area as I was going to wait for my mate who was coming up in a week. I decided to take him to the old Emily mine area as I never fail to scrounge a few bits there. I had to go into town with a flat to get repaired and left John to carry on. He found a little patch that he eventually got around 5 or 6 pieces all the size of .1 - .2gms. I found another piece of around .5gms and then John had to go home due to business commitments so I was on my own. I went over his patch again and only found one more .3gm piece. I had issues at the Emily area with the detector going berserk over the salty ground and even tested the other detectors I had with the same result. Even so I started to pull out the mods and could not get the detector to behave. I then went on the Trike to behind Cuddingwarra mine to some scrapings and found another target with my coil at .2gm. I found another 2 nuggets all tiny and again. So I know had 5 nuggets for a total of 1.5gms.

I contacted my mate who also had to change his plans due to Harmony reneging on written permission to go on Kirkalocka land. So I shifted to the Jean Well area around 30Kms south of Cue to wait for him. I then found my smallest target to date of .15gm with my home made coil so now it had found my biggest target and smallest. Funnily enough both were around the 3-5" mark.

When my mate arrived he had his GPM modded 2000 another mate had a tweaked 2000 and finally one with a 4500. On the trip my mate (Outback) has the midas touch when it comes to finding gold and had a couple of nuggets already. They tested the 4500 on these targets and others and he could hear all the targets found with the 4500 on his 2000.

The fellow with the 4500 had hurt his back a day or so before and had to go because of his suffering. So unfortunately I never got to see the 4500 in action on the salt lakes to see how it run. My mate got another 1gm and then an 8.5gm.

To get to the reporting of the detectors and performance, on salt the 2000 definitely outperformed the GP's for noise. I was getting so frustrated especially when my mate found 2 targets immediately and we tried to find them first with the 0ther 2000 running my 10" elliptical Coiltek coil, he could hear them with ease. I then tried with my 3500 with the 11"dd in mono mode in salt timings. ABSOLUTELY NOTHING not even a whisper. It was a .2gm at about 1" down. He then found another and called me over to try the GP again as this target was louder. Again nothing. He then suggested to put the GP in normal mode. I did this and there it was immediately a good signal but extremely noisy when waving the coil enough to drive you crazy after 1 minute! I didn't have a smaller mono coil but had a 10" Elliptical DD that I put on and left the detector in normal mode and mono. I the started to find targets but none were gold, just bullets and rubbish.

We then went to another part of Lake Austin and I left the detector in that configuration. I then found the only target for the rest of the day and that turned out to be a 2gm at around 6" down. I was finally "At one" with the detector on salt. This target was actually quite satisfying as someone had found some bullets and made the mistake (which pissed me off)by re-burying the targets!! This actually lost him the 2gm nugget (serves him right:woohoo: ) because he reburied the target he couldn't distinguish the other target 3" from his hole. A lesson learned here I think!!!

Anyway, I found a few more nuggets on the trip all small and we never found any patches just one here and there. I came home a little disappointed with the gold that I had found 11 pieces for 7gms but gained a wealth of experience and because of this I am very confident with the detectors ability.

With the mods I fine tuned them and only now can I confidently say which ones work and which do nothing. I took out the CPU frequency mod this did nothing in my opinion and on the tests I run I saw absolutely no gains or benefits. I was told that it eliminated hot rocks, it didn't in fact it enhanced them.

The last piece of gold I found was a .05gm nugget at around 1". I was using the 11"DD in mono mode with normal (standard) Frequency in Sensitive 2 mode. The target did come up a little with the higher frquency but not by much, the CPU frequency did not add anything other than eliminate the target after the first swing in Medium tracking where as in normal CPU it took a couple of swings before it disappeared. By that time I had tossed out my Discrimination knob and replaced with a switch to change the internal gain from High gain (around twice the gain of a 4500) and standard 3500 gain. I could hear the target with both but the higher gain setting was much more pronounced obviously. The 3500 was only slightly noisier with the high gain but still very stable.

In my comparisons with the 4500 and 3500 I found the 4500 to be very stable but in reality couldn't match the 3500 for performance with the same coils. HOWEVER the 4500 will run a mono coil with ease where we need to use a DD. On my final analysis the 4500 with a mono and a 3500 with a DD and high gain and sensitive 2 are an equal match! The only benefits are how quiet the 4500 runs and its ability to ignore hot rocks and those condensed mineralised ground signals. Almost everyone I met out on this trip was running a 4500 and they are very good and worth buying. However if they increase the gain in the next model they would be unbeatable. The 3500 when in Medium tracking was very good at eliminating hot rocks and ground noise when you sweep over them a few times, in fact following JP's advice in hist 3500 update DVD on tracking I found that 10/10 times I could eliminate a hot rock and ground but I still dug them just in case and always will until I find a nugget that reacted the same.

In Summary, the overall winner in my opinion was the 2000GPM. It could work with bigger coils than I on salty ground. This makes me believe the GP's gain is too high in standard. On my next trip I will be testing this theory. But to implement into detectors you must have a switch to change the gain and this is hard if you want the discrimination feature as there is no room for the extra switch. It is very big on the inside. So I would recommend for those that run in Salt a lot, either the 2000 or the 4500 but having said this I don't know how the 4500 handles salt and whether it would detect those small pieces my mate found with the 2000. Maybe JP could comment on the 4500 on salt and give some insight? I know that in salt mode on the GP you lose at least 20% sensitivity and even with a 14" salt coil I found the GP detectors too bloody noisy!

I also found the best way to run my threshold was just barely audible at around 12-12:30 o'clock.

I have to end this now have some things to do but will try and continue updating you as I am able. Maybe better if you ask questions rather than me trying to give all details.

Catch you all later

Hi Inhere, thanks for the advice regards coils but I only used that mode for convenience and when tested against a similar size mono there wasn't much in it but know where you are coming from. Just for your info the coil switch for DD and Mono just uses a different pre-amp configuration but in cancel mode I am not sure but will check our circuit diagrams for it. Just that it has nothing to do with timings. That is only on the soil switch.

Yes the gain is not twice as much as what is in the GP but what I meant was that the gain increase is twice as much as the gain control function in a 4500 just bad wording. The gain difference on the GPX is not how it appears (0 -15) the actual gain increase as example from FP-8 to 15 is only around 10% difference if that. My gain is up to 50% higher than standard in the GP series and on the GP's only increases the noise factor slightly when the ground become mineralised. That's why I have a switch but most of the time I run the high setting as I also change filtering and not just gain as we did with the 2000.

So I stand corrected on actual gain increase and hope this clears it up.

On another topic and No Doug I am not knocking Minelab. Apparently some of the recent sales of 4500's have had some problems. Not sure what exactly but a mate of mine told me on his last trip a fellow had bought 2 and one worked fine and the other didn't. Rumour has it that ML sold up to 7000 this year in WA and obviously some are slipping through the QC. Still I recommend the 4500 as a good detector which is the best detector ML have so far produced. Even though the modded GP's are giving it a run for the money the 4500 overall is a good detector without the need of modding. So far all the hype about EMI issues appears to be just that, I have had a couple to mod and test and saw a lot in the field and none had EMI issues. In fact in my workshop I can run a 4500 a hell of a lot better than I can any other model. I think that maybe they could improve the EMI rejection a lot more but unless you only want to work in EMI affected areas it still outshines the others. Sometimes when you haven't radically changed your concept some things have to be a compromise but ML have done a pretty good job.

Hi Dave a quick and effective mod is internal gain and filtering and the sensitive 2. That's all you need. Putting the sensitive 2 would be okay externally but you would still require a socket so in that case why bother a switch is just the same. The only way of giving any increase in performance is to run an external amp/booster. This will allow you to hear a little better.