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Last Post 26 Apr 2021 02:58 PM by  ROBERT MARTINEZ
GMT
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ROBERT MARTINEZ
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13 Jun 2020 11:02 AM
    I recently purchased a Whites GMT. It came with the 6"x9" Double D coil and a 8"x14" Sierra Gold Max coil. I took it out to the gpaa claims in the Morristown area. Towards the end of my testing and it was getting hot. I put the big coil on. I got up on this hill overlooking a wash and started detecting. I got this positive zip zip sound. I scraped the loose gravel with my boot and still got a good signal. I scraped down another 2-2 1/2" and found a .04 gram flake of lead. I wish now I had started with that coil. Just thought I would share that. I was set at 2.5 gain and around 2 on s.a.t. the ground was balanced around 60 if I remember right. The other coil balanced around 70-71. I had the double D coil set around 3-4 gain and 2 1/2-3 s.a.t. Later when I learn this detector I'll increase the gain.
    ROBERT MARTINEZ
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    05 Jul 2020 04:36 PM
    So today I went out to Kings claim North of Morristown and tried out the 8" x 14" coil on my GMT. I can't believe how tiny the targets it can detect. I spent 7 hours detecting and found many junk targets. And in that 7 hours I didn't wander very far. It takes awhile to detect a section of ground. Lots of birdshot bits of wire mesh etc. As I was leaving I realized I didn't test the depth of the coil. Most of the targets I found were surface finds and a few around 3" deep. So I stopped on the south end of kings and buried a .7 gram piece of old lead about 3 plus inches down. I set the detector with a low threshold in my headphones and no sensitivity or sat. I could detect the target easily. I then dug up the target and buried it 6.5 inches down and passed the coil over the target again with no sensitivity. It was on the edge of detection. I turned the sat to 3 and the sensitivity to 5. It blasted loud in the headphones. I could have buried it lower but I felt comfortable that I wasn't missing targets when I had been detecting earlier. I just realized I never used the audio boost. I was really surprised that I could detect the target with no sensitivity. Hope this helps someone out there. Good luck detecting. ☺
    ROBERT MARTINEZ
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    08 Aug 2020 01:33 PM
    So the other day I was testing a receiver/transmitter bluetooth thing I got off of Amazon on my GMT. I had a good set of Bluetooth ear buds already. The very first thing I noticed is that I was able to turn the threshold way lower than I could with my regular wired headphones. I was able to adjust the gain or sensitivity higher before I could hear instability sounds. I was able to hear my .04 gram test nugget loud. I read the directions that came with the detector and it touches on the headphone subject but really doesn't explain why they're important. Check out high ohm headphones with your detector to see which ones sound the best. My ear buds are also clear sounding and not muffled. I plan to wear shooting ear muffs to help with wind while using these. Hope this helps someone.
    ROBERT MARTINEZ
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    25 Sep 2020 12:49 PM
    So when I used my Bluetooth ear buds I noticed that I could hear everything. I had to turn the volume down on the ear buds so a buried tin can didn't make me deaf. I then set up the detector to the just barely but audible threshold and ground balanced while my gain was around 5. I used the SAT to around 2.5 - 3. Hope this helps anyone.
    ROBERT MARTINEZ
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    28 Oct 2020 08:00 AM
    When turning on my GMT, and I noticed it works basically the same with my gold bug pro and xterra 70, I have my SAT around 3 and I'll set the detector to around 7 while the detector is held in the air. I then slowly turn up the threshold until I just start to get a sound. Sometimes it's a sputtering noise then I turn it up a tiny bit more so that I know the threshold will be audible when I ground balance. By the way my headphones are set at a comfortable level when I'm doing this. I ground balance in a large area around me to find the least ground balance signal and balance to that area. Then I see how stable the detective is as I slowly sweep the coil back and forth. If it's noisy where I can't hear the sound the threshold made when I first set it then I lower the gain until I can distinguish the ground noises from the threshold and constantly ground balance as I do this. Just figured I would pass that on. Hope it helps.
    ROBERT MARTINEZ
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    11 Nov 2020 12:54 PM
    I went out to the claims this past weekend. The first thing I noticed is that the GMT concentric 6" coil reads the ground around 62-65. The 5"x9" coil reads it at 71-72. Also the concentric coil required higher S.A.T. speeds. I thought I would have to swing faster but the ideal speed was actually slower. The overlap has to be closer and the ground balance I figured out manually balancing has to be faster up and down to outrun the S.A.T. I had to flip into fast track to figure out where to start the manual ground balance. The coil sees very tiny targets easily in the ground but when you get them out of the ground that's a whole nother thing. I had to flip into signal boost a few times. I guess I need to figure that out.
    ROBERT MARTINEZ
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    13 Nov 2020 02:21 PM
    I came across this story about a guy finding a 27oz nugget out by one of my friends claim. I ordered a 27oz lead fishing weight to test my detector settings on. The nugget was found with a VLF detector 2' deep. Figured I would bury the weight and listen to what I should be listening for. Just doing air tests, I can only get about 1'6" away from the coil. I have a concentric 9" 7khz coil and I put the 14" elliptical concentric on my GMT and my 6"concentric coil and the same results. I know that the air tests are around half the distance you can actually detect. Does this sound like a fish story using a vlf detector? Maybe it was a pulse induction detector. But either way I was surprised that the huge heavy weight was so hard to detect. And gold will be harder to hear even more. Very interesting test. I'm still going to bury it and find out the limit of my detectors.
    Leo Lorenz
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    15 Nov 2020 12:33 AM
    But you need to take into consideration that a target in the ground builds up a "halo effect" around that target which allows it to be seen at greater depths than an air test does. This affects your detectors sensitivity.
    ROBERT MARTINEZ
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    16 Nov 2020 12:04 PM
    This person did gesture with their hands that the target was big. So maybe the weight is right just the target was more spread out making it bigger. Easier to detect deeper?
    RICHARD POTTER
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    31 Dec 2020 01:30 PM
    I am interested in getting a larger coil for my wife's GMT to use it here in AZ. Where is the larger coil available and do you know the cost? Thanks for a very good and detailed write-up. Maybe we will run into you out on the San Domingo claims.
    Dick Potter
    ROBERT MARTINEZ
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    06 Jan 2021 10:34 AM
    Just of the top of my head I would say Kellyco would have a large coil for the GMT. Thanks for the comment.
    ROBERT MARTINEZ
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    19 Jan 2021 10:10 PM
    I purchased a 6" concentric coil cover for a goldmaster 24k concentric coil for my GMT 6" concentric coil. It fit perfectly in case anyone else is looking for one for their coil.
    ROBERT MARTINEZ
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    01 Feb 2021 04:29 PM
    So I went out to some GPAA claims to make a short video about how I set up my GMT and Gold bug Pro. I didn't say in the video but when you hunt always keep your threshold constant. If when searching it goes silent you might be searching to fast. It's very eye opening just how slow you have to move the coil across the soil. The amount of mineralization will dictate how fast or slow to move the coil across the ground. But you can hear the detector searching the ground if you just move as fast as the detector is telling you. You will hear targets. The targets may not sound like a zip zip sound. It may be a drawn out sound. Anyways here is the link to the video. You might have to copy and paste it to the search bar to go to it.

    https://youtu.be/PSQhFUXOask
    ROBERT MARTINEZ
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    21 Feb 2021 05:24 PM
    I made a demonstration video of using the threshold to hear targets while gold detecting. Copy and paste link to YouTube video. Read the description with the video to learn more. Hope this helps someone.



    https://youtu.be/4w7TAY8kvfg
    ROBERT MARTINEZ
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    11 Apr 2021 09:11 AM
    So after I turn on my detector and get my threshold set, I turn on my fast track or auto ground balance. If I can't get my detector to ground balance I slowly turn down my gain or sensitivity till the detector auto ground balances. Then I switch to manual ground balance and ground balance the detector with just a little bit of a positive on the down stroke of the coil. And every once in awhile I'll switch back to auto to see if I need to adjust my sensitivity then repeat the process. This helps me keep my detector at a proper gain or sensitivity setting. I hope this helps someone out there.
    ROBERT MARTINEZ
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    20 Apr 2021 10:57 AM
    So I was out at the Morristown claims again. I had the 6" concentric coil on my GMT. I went to the east end of Golden Dreams and detected. I had a gain of just a little over 2 and maybe a 2.5 on the S.A.T. That gave me a smooth threshold sound I then turned down the threshold to barely audible. I found bird shot here and there. The smallest being around .06 gram. I purposely kept a stable threshold setting to see how well the machine did. I think the deepest I got a signal was about one and a half inches deep for the bird shot. Bits of wire were naturally deeper because they're steel and hot rocks were quite abundant. I drove up to Vulture bait the south end and the gain was about the same. You can really tell when there's a difference in the threshold. I was surprised to find so many targets. I was able to not add SAT and it ran smooth but every once in awhile I would get a lapse in the threshold. Lowering gain didn't seem to help so I added a little SAT and that helped. I never had the SAT above 3 on my machine.
    ROBERT MARTINEZ
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    26 Apr 2021 02:58 PM
    I found that on my GMT detector that out at the Morristown claims when I first turn on my detector I have all my dials at a minimum. I have my headphones plugged in and the volume turned up on them. I have my detector held in the air then start turning up the threshold till I just start getting a noise then I slowly add a little more volume to make sure I hear it properly. The next thing I do while still holding the detector in the air is start dialing up the SAT. I get it to make the threshold unstable then I start slowly turning it down until my threshold is smooth. You really have to listen close. Sometimes I have to do it twice. Now I have my toggle in fast track. Now time to ground balance the detector. I turn up my gain or sensitivity until my detector is obviously out of ground balance. I keep pumping the coil up and down while turning down the gain slowly. I keep listening to the machine until the detector all of the sudden doesn't make a noise either up or down and the threshold is smooth. I next look at the readout on the screen about the ground balance. For instance on my detector in Morristown it read 65 so I flip the toggle to manual ground balance and adjust the numbers to match with the plus or minus buttons depending on which way I need to adjust. I listen carefully once there to the threshold and ground balance perfectly. Now my machine is set. I flip the toggle back to fast track and turn the threshold down to barely audible. Don't worry about the number settings on the detector. This is the starting point for the detector to search. I search in fast track and if I hear a target I flip into manual to locate it. Now remember this is the starting point for detecting. Search and listen carefully for those tiny signals. Read the manual and it will all make sense now. I hope this info is useful for someone. Good luck hunting, the rest is up to you.
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