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Wondering About Max Depth For SDC


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I went back to the deep canyon this morning. I found 2 that I missed the other day. It seems peculiar that I found 4 quality nuggets in there with a total weight of over 1/4 oz, but nothing deeper that about 8 inches. The canyon is all bedrock with overburden ranging from 0 to about 2 ft. I covered just shy of 2 miles of this good looking ground and obviously had decent success, but just wondering what I might be missing. I found no nuggets on the margins of the wash, everything would have been right in moving water during heavy rain runoff. Today's fatboy was smack in the middle of the wash, but found a hidey hole in jagged bedrock. Perhaps when that new Minelab Super detector comes around, this spot will give up its secrets. Today's take, 3.3, and .4 grams.

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Condor,

I have no gold to show for my SDC efforts (minimal) so far, but i will offer the resilts of air testing here at "Casa Sonora" in Gold Canyon - where there is no gold.

Using a nickel as a target, i get:

SDC on preset - 12" plus a little -on setting 5 - 13"

SD-2100 14" coiltek mono - 14" and a bit - with 8" ML mono 12" plus a bit.

One thing worth mentioning. My house is EMI hell, mild mannered Whites machines protest at having to work here. My TDI never gave me a nice threshold and the ATX I had was never entirely smooth.

The SDC warbles a lot even after noise cancelling. In fact, even at preset 3, it is more warbly than my SD-2100 with a 14" mono coil. I'm not especially pleased about that after reading many reports about it's EMI resistance. Having said that, it is very quiet over the ground, doesn't have the usual sort of touch sensitivity. However it gives a solid good sigmal every time I brush the top of any green living desert plant, for example a palo verde sprout.

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The SDC is very, very sensitive and so responds to the the high EM interference around a house badly. At home is a poor place to performance test a PI detector - even after noise cancelling. You need to take it out far from power lines to get a more realistic evaluation of its performance. Its not really intended for "in town" use. I had no problems with touch sensitivity on green or dry plants with it in many hundreds of hours this summer in California, Nevada and Alaska.

 

The SDC is not a detector for large nuggets deep, either. I dug a 3/8 ounce specimen piece at about 9 inches this summer in Alaska with my SDC, but if you want maximum depth of nuggets of a few grams and larger, you want to use a GPX 5000. 

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Thanks for the feedback Chris,

Unfortunately some patches have powerlines, including the ones I was out on this weekend here in AZ - and EMI immunity was widely reported in the forums. Also, I was struck by the comparison with the SD-2100. Basically, my SDC is no more resistant to EMI than my SD-2100. So do you reckon that that is generally true - or is my SDC worse than average or my SD better than average.

If yours doesn't react like mine to things like a 3" high green Palo Verde sprout, then perhaps I need to send mine in for a checkup. I did, after all, carefully note what occurred. Perhaps I will do that, after all, my unit's performance seems to be significantly different from yours.

As far as depth, I sort of have the opposite conclusion than you seem to suppose. I have read many hundreds of posts on US and OZ forums and got the clear impression that the SD-2100 was not in any way clearly inferior to GPX series detectors when it came to depth on larger nuggets. Given that, the fact that my SDC comes within a small margin of my SD-2100 when that detector is using a well regarded 14" mono coil is pleasing to me.

Given that, and acknowledging the differences between air tests and real ground depth, I was very pleased with the depth of the SDC. I,am pleased with the detector overall,

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Hopefully we can get JP to weigh in on not only theoretic depth, but daily experience on let's say a 1.5 gram nugget. We all recognize gold content, ground conditions etc will affect depth, but an 8inch coil has an inherent depth limitation. I'm not bitching mind you, I've found an oz of Yuma gold over the past month, and I've found gold measuring in grains at impressive depths. I just want a better understanding of my limitations.

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The only time I have had issues with the SDC bump falsing, has been when the coil cover got full of sand. The coil cover is not the tightest and does fill up. You might check that before sending it in.

 

JP and/or Steve can offer their opinions, but I would say that for nuggets less than 1.5 grams, the SDC would have an advantage over the 5000, nuggets in the 1.5 to 2.5 grams, they are pretty close, and bigger than that, the 5000 would have a depth advantage. I got one nugget about 1.2 grams as I remember that was about 6+ inches, but the signal at the ground surface very weak and I only dug on it as I had found other gold very close by.

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Well, my SDC almost never falses on anything. EMI is not something I can say I have put to serious test as all my use has been away from power lines.

Depth? Well, 8" coils can do pretty darn well actually. Still, I do not believe in doing "fair tests" as much as just getting results. A GPX 5000 with an 18" mono will totally blow the SDC away for depth; the larger the nugget, the more the margin, but twice as much depth on a large nugget would not be surprising.

If an area has been hit hard, like for instance Rye Patch, I am sure few big nuggets are left. The SDC excels is hammered locations. It also does well in virgin ground, but if as is true in Condor's case a person is going remote and getting into areas with little previous hunting, big nuggets may still be available that a deeper seeking detector would do well on.

But couple grams and under? If that is all the area has I at least am pretty confidant the SDC will do a real good job. Maybe a GPX will snag a few solid 2 grammars a hair deeper than the SDC but it will not be handfuls.

We only get to use one detector and coil at a time. We all just have to make a call on what we want to use in any location. I can promise anyone if they find a gully and pull quite a few nuggets out of it with one detector until nothing remains, then you almost have to try something else also just to be sure. You may find the first machine got it all. You may find the first machine missed a couple. Or maybe the first machine missed a lot. Since every site is unique you just don't know.

Just my personal history. If I hunt an area hard and find gold, I have almost always been able to go back and find smaller gold. But when I gear up and go look in the same place for the big ones deeper I think may be there - they usually are not. Now that is just me but basically it also reveals some basic statistics. Smaller gold is more common than big gold so shifting smaller is just more likely to get results. It also is just easier to miss small gold. It may be stuff you can only hit at an inch or two. A sloppy swing, you miss one. A little gully washer taking off a little soil, more little nuggets appear. Scrape the surface, roll some rocks, more little nuggets appear. The big stuff though, it gets found pretty easy, and very often simply by the first coil over it.

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The SDC is seeing things a lot differently compared to previous Minelab PIs thanks to MPF, because of this the targets it sees are not necessarily dictated by weight anymore but more to do with time constant, especially the Fast Time Constant targets which sometimes can actually weigh quite a lot. Friable gold, prickly specimen gold anything that resists being "livened up" by traditional PI transmit pulses, especially in ground types that are too mineralised or deep for traditional CW detectors (VLF) or a combination of both are well suited to the SDC.

As far as EMI goes the SDC is far superior to any previous Minelab PI machine, but you have to consider a couple of things before you make that call, one is Mains noise is always going to be an issue with a highly sensitive instrument like the SDC, as such if you get too close you will start to hear it pulse. However Sferics noise is greatly reduced with the SDC, a lot of noise generated by power lines is Sferics noise gathered over great distances, fence lines especially ones that pass under power lines also do this along with buried telephone lines and power cables, all of these tend to gather this type of EMI and channel it. The GPX 5000 is especially prone to this type of noise even at great distances whereas the SDC is very resistant to it.

The SDC runs a much faster Motion filter compared to the Slow Motion filter of the GPX 5000, as such it can sound twitchy to the ear especially at high Gain levels, you combine this with a small amount of EMI being present and it can sound busier overall in the threshold, however if you really listen to the threshold you will soon realize the general twitchiness of the threshold is much more consistent compared to the lunging sporadic nature of previous Minelab PIs.

I sometimes get a bit of falsing off green plants with my SDC too, I think it is a static discharge that occurs in very low humidity areas.

Hope this helps

JP

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Thanks, JP - lots of good imformation.

My EMI complaints are pretty much of the mains power supply type. Around my neighborhood the domestic power distribution net is 100% underground, with the transformers in boxes on the ground. It's totally abuzz with AC noise. A really tough environment where none but the most insipid detectors of the 20 or so different ones I have used here are unaffected. I was just surprised at the SDC being just as susceptible to it as my lovely old Sd-2100.

As I said before, I am quite pleased with the depth the SDC displays against the usual targets I encounter - now if they were only gold instead of the growing collection of lead I have. I may have to take up muzzleloading shooting again and cast my own bullets!

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