GMT 24K Conundrum, Orx & Nox Too!

[Jeff McClendon]

So, I have an area in the Colorado Rockies that I am trying to successfully detect with the GMT 24K. The main issue here is tons of magnetite and I mean tons. Imagine a regular sized plastic sandwich bag with a 2" thick sandwich sized amount of dirt inside it instead of a sandwich. I brought a couple of bags full of dirt like this home from an area that appears to be a drainage ditch that was at the end of a sluice run in a hydraulicked area. I got almost 1 cup full of varying from speck to marble sized magnetite by panning out that bag of dirt, so about 1/3 of the dirt was magnetite. So far, I have detected this long trench with a GMT 24k and an XP ORX with 9"HF coil. The 24K shows 8 segments of mineralization and a phase reading of 85 in Ground Scan mode. The ORX ground balances at 88 with the mineralization bar full. The GMT 24k overloads at sensitivity 4, VSAT maximum in VCO audio and no iron cancel. The ORX does not overload but I have to constantly ground balance, with sensitivy on 70, reactivity on 2.5 and Disc IAR 2, frequency 50. Getting any kind of zip zip signal in this sea of double beep boings is proving difficult.

As I said, I brought some dirt home to test. I figured with all of the advanced settings on the GMT 24K I should be able to find something that works. I took one of the bags outside and laid it flat on a plastic 24"x12" Igloo cooler. With the 24K, 6.5" concentric or 10X5" DD coils in VCO Zip audio mode, sensitivity 3, VSAT maximum, threshold 2, XGB auto, I got various amounts of ground noise and plenty of medium to loud double beep boings while bobbing the coil or swinging over the bag. Just what I expected. If I ground balanced and locked XGB when pumping the coil it almost silenced the magnetite and I could swing over the bag with much quieter, little responses but still clearly magnetite boings. If I then pressed the Iron Cancel button (iron cancel discrimination was set on the numeral 2 not 2 bars so no bars were showing) the magnetite was virtually silent. I switched to beep audio and still virtually silent with just a faint threshold response, meaning that instead of a high tone or low tone there was a faint, medium tone, 2 way threshold target tone apart from the reference threshold, I guess. I took a .2 gram flat nugget and placed it under the corner of the bag of dirt and reset the settings to what I started with, VCO zip tone, XGB auto, no Iron Cancel and carefully ground scanned over the area of the bag that the nugget was not under to let the XGB system reset. Sweeping the nugget a few times I got mostly boing magnetite signals with a very faint hard to distinguish zip sound. I pressed Iron Cancel (still set on number 2, also tried 1 with the same result, no disc bars showing) and got virtually nothing, with no zip zip responses of any kind. I locked the quietest XGB setting, with the lock button, no Iron Cancel and VCO audio. I got a nice zip zip with a little magnetite boing. I pressed Iron Cancel and literally got no signal of any kind, complete silence during sweeps. I thought WTH, and pressed the beep mode button for high and low tone pitch audio. I did not get a high tone or a low tone but I did get a very clear 2 way medium tone threshold response with a very quiet background except for the actual threshold tone.............? I removed the nugget and swept over the bag again with the same settings and got only a very faint medium pitched threshold?? tone occasional response. So, hunting this area in VCO audio, XGB locked, Iron Cancel off,  sens. on 3, VSAT maxed, might work but I would be digging a lot of magnetite. Hunting in Beep mode with Iron Cancel On and listening for that medium whatever it is tone might work too.......?

There is no mention of this medium toned, what I am calling threshold tone response in the manual anywhere. I used to hear something like this on my MX5 using multi tone modes with the threshold set on low when I encountered a target that was just past the range of normal detection audio or numerical target ID detection. The MX5 let me know something was there. I am not sure what this tone is called or if it is the same thing that is happening on the 24K. Personally I like it if I can depend on it........... Any comments would be greatly appreciated.

By the way, I ran the ORX and Equinox over the same target scenario. The ORX in Gold 1 with a little tweaking could hit the nugget but only with sensitivity turned way down (60 -70) in order to quiet the magnetite responses down enough to hear the target. Frequency 50 kHz, GB 88, Sensitivity 60 to 70, Reactivity 2.5 Disc IAR 1 or 2, Iron Volume off, Threshold 4,  tons of ground balancing required just to hear a clear zip, zip. The Equinox 800, 6" coil Gold 1 multi, -9 rejected,  GB 1, sensitivity 15, threshold 10, recovery speed 4 to 6, FE 0, had no problem giving a beautiful zip, zip on the .2 gram nugget with minimal ground noise............Hum!

Jeff 

[Steve Herschbach]

Really ground for a SDC 2300 as there are places where a VLF simply will not satisfy. You have to dumb them down so much to deal with the ground you end up spitting in the wind. I can't help you with the 24K tone question, but in ground like that first thing I'd do is ditch the concentric for a DD, preferably the small one.

[Jeff McClendon]

My new SDC 2300 arrives today, can't wait.......big thanks to Rob Allison for the excellent bundled deal with military discount too. It will get the next crack at the area mentioned in this topic.

I also tried the 10X5 elliptical DD last time I was at this spot and during my testing today. Very little difference. I do not have the small DD elliptical. 

The Equinox aced this problem with minimal adjustments.  I think I know the answer but I would love to hear more opinions..........

Jeff

[Jeff McClendon]

SDC 2300 arrived safely, put some batteries in, ran through the startup sequence, ground balanced over the magnetite dirt, scanned it=no response, put the 0.2 gram nugget under the bag and detected it clearly and easily. 
 

Amazing detector.   
 

Jeff

[Steve Herschbach]

I‘ve not run into ground yet where I have not been able to get my Equinox to make me as happy as a VLF can. Truly though once you get used to something like the SDC a VLF seems a waste of time. The SDC will have you digging every bit of trash though so no perfect answers. Hopefully we will get SDC type performance in a regular detector housing someday. A SDC configured like the 24K with coil set to match... there I go, dreaming again! 

[EL NINO77]

 ....I would try to use the Frequency Shift function - where a stronger deviation from the main center frequency of the detector upwards should help reduce the strength and amount of RX received detector signal ..- and in this case more stable and better detection ...
It is best to use the Shift frequency and at the same time try to reduce the sensitivity of the detector ... to an acceptable level...

I used this trick with success with some detectors - which, when working on the main central frequency, it was not even possible to properly tune the ground because they already switched to overload when transferring GB ...

[Mark Gillespie]

10 hours ago, Jeff McClendon said:

SDC 2300 arrived safely, put some batteries in, ran through the startup sequence, ground balanced over the magnetite dirt, scanned it=no response, put the 0.2 gram nugget under the bag and detected it clearly and easily. 
 

Amazing detector.   
 

Jeff

Very excited for you. 

[bado1]

SDC is a great machine...Congrats on your purchase!

I believe that Steve is right on the money....there are places (most IMHO) that VLFs just can't do the job due to the ground conditions. I've seen many guys get frustrated trying to detect (successfully for gold) with a VLF. Yes, there are certain areas and conditions where a VLF can operate for nugget shooting but they are not a good primary tool for use as a nugget shooter. I believe that a guy should have both a PI and a VLF and know when and how to use each for their specific strengths. If I could only have one it would be a PI. 

Good luck!

Dean

[Steve Herschbach]

I can get a VLF to work anywhere, but the reality in bad ground is you are getting 50% or less of their possible depth in milder ground. You also have to really know your machine well to work halfway effectively in the worst ground.

Or you can get a SDC 2300 and just turn it on and go detecting, almost no knowledge or expertise required. It will cut though hot rocks and mineralization that will stop the best VLF, and will get small gold under those conditions better than possibly any other PI made. The SDC will detect gold as small as most 19 kHz VLF gold detectors but under conditions where those detectors are ineffective. And though it has the reputation as a small gold machine, it will punch quite deep in larger gold, as deep as an 8” mono coil will allow.

If it was not for the expense the SDC 2300 is the perfect beginners machine for nugget detecting. Easy to operate, and although it makes you dig everything, many people would say you should be doing exactly that anyway on any decent gold location.