By Steve Herschbach
I took the MDT 8000 up to Tahoe this morning for a few hours of wading. Beach is heavily loaded with magnetite sands. There is a lot of deeper sandy material, but also some scoured out areas with gravel and rocks. The sand tends to have few targets. The gravels are the base and thick with targets in some areas, including lots of deeply rusted ferrous stuff, some of it quite large. I like hunting the gravels due to the target density. It however is not very VLF friendly stuff due to hot rocks and magnetite sand.
The MDT struggled to stay quiet in the gravels. Due to the target density I decided to run in 18 kHz DISC for this session, but the high tone pinging was pretty continuous. The good news is I was after mid tone targets so this was not a huge issue. The mid-tone false signals were far less prevalent. Still, I wanted to see what I could do to make the machine run quiet. With Sensitivity 6 I could get a good manual ground balance at 614. I tried Salinity 15, no improvement. I turned on Black Sand mode. No improvement. I lowered sensitivity to 2, so DISC Mode, GB 614, Black Sand On, Salinity 15, Sensitivity 2.... no real improvement on this high tone pinging.
However, at DISC Mode, GB 614, Sensitivity 6, BS Off, Salinity Off, the unit was well behaved on the sandy material. It is just the gravels where it was noisy. The reality for me, since I was not hunting coins was.... I don't care. Rather than dumb the machine down I just ran the higher settings in the gravels and ignored the high tone pinging. Simply chased mid-tones. There was some mid-tone falsing but not enough to be an issue for me. I'm used to running machines hot and noisy and hunting by ear so was actually happy with the resulting setting. Like I say though, a coin hunter might get frustrated.
The results below, all the recovered targets. Nothing was super deep, but that is no surprise here as this is normally the kind of stuff I'd run a PI in. Was getting the right kind of targets and only a few items tricked me, three bottle caps heavily encrusted with rust being of note. There is also one dime and one quarter than came up mid-tone, but I recovered nails with both so I think that skewed the target id. As far as target id numbers, I have no idea. I was just digging any halfway decent sounding mid-tone.
Like I said, I am happy with the mix. I like to see tabs and nickels and unfortunately corroded zincs - all gold range targets. And a 14K white gold cross pendant, breaking a gold jewelry drought I've been experiencing lately.
I'm still a MDT newbie, but basically find the machine easy to run and quite capable of doing what I want it to do. If my mention of the ground noise is off-putting, do not let it be. This is some really nasty stuff, and any VLF is going to suffer here. I thought the MDT did quite well.
By Keith Southern
Quarter under a sheet of aluminum foil.
Tarsacci has the foil I.D .number Notched out which is about 6-7 ID..
Note the Safari is for demonstrative purposes only.
By Steve Herschbach
I explained on another thread that I was interested in giving the MDT 8000 a spin looking for gold nuggets in trashy locations. All mining camps are places where supplies were hauled in, and none of it left the site, but is scattered everywhere. Miners were not into wasting time, and if possible built their shack, or cabin, or small town, right in the middle of where they were mining. It is not uncommon therefore that there is good gold right in and around some of the trashiest locations in old mining camps. Time has passed and often the wood is gone, rotted away, or left behind when the structures burned to the ground. Old nails and remnants of rusted cans are the most common items, but every manner of metal item that might be needed to survive and mine in the wilderness might be found.
There are detectors that might do better on the tiniest gold nuggets than the Tarsacci MDT 18000, but the MDT has a hot 18 kHz mode that is more than sufficient for common VLF nugget hunting tasks. I knew without even trying it that the MDT 8000 would have the sensitivity I was looking for. My main question was whether it offered anything I could not live without for finding gold nuggets in locations littered with ferrous trash. It is also very common in mining areas that the ground is quite mineralized, though that is not something that is universal.
I gave the MDT a go at a location where there used to be a shack built on some gold bearing ground out in the Nevada desert. The shack is gone, but there are plenty of cans, remnants of cans, nails, door hinges, bed springs, stove parts, etc. All the metal stuff that was ever brought there, but was not valuable enough to be scavenged as the years passed.
The bottom line is the MDT 8000 did not disappoint, and I did manage to find a gold nugget in the limited amount of time I had. The nugget is interesting to me in that after cleaning it weighs exactly 1 gram, as weighed on my very accurate digital powder scales. I find a lot of nuggets that weigh about a gram, but I don't really recall ever finding one that was 100% spot on before. It's probably happened and I did not take notice of it, but this time I did.
Gold nugget fresh out of the ground
Exactly 1.00 gram!
The good news is I did not find anything particularly difficult about using the MDT 8000 on this short test run. I bounced back and forth between mixed mode and disc mode a bit, and far preferred mixed mode. I am big on audio information, usually running detectors in full tones and preferring modulated audio. I also prefer having visual target id information available, I'll take all the tools I can get, but in general I hunt by ear and prefer complex audio. Many people would find the way I run my detectors to be too noisy or busy but with nearly 50 years of detecting under my belt my detectors talk to me and I want to hear everything they have to say.
So mostly mixed mode, black sand and salinity off, sensitivity to max, and ground balance manual 668 on this ground.
This is admittedly a very preliminary report based on limited use. However, It does not take me long to come to general conclusions about metal detectors. The Tarsacci MDT 8000 is more than capable for the task of VLF nugget detecting, with gold sensitivity as good or better than popular prospecting models running in the 18 - 20 kHz range. While the machine is very capable, there are a couple things that left me shrugging my shoulders a little bit. First, the audio. The tones chosen for revealing non-ferrous targets are extremely high, with the high tone being almost out of my discernible frequency range. Imagine a "tink" sound like tapping a glass bottle with a knife handle. I have some definite high frequency hearing loss, and while the MDT is usable for me, I'd be lying if I said I loved the audio. There are no tone adjustments I am aware of on the MDT, so it falls into the realm of something I just have to live with. There is some ability to modify the response by perhaps trying different headphones looking for those that deliver the tones as they are in the best fashion possible, but that's about it.
The other thing is that many discriminating detectors have a common enemy, the flat remnants of steel cans. Think steel cans, thin wall wood stoves, thin steel roofing... bits and pieces of flat steel anything. Coin and jewelry hunters are quite familiar with the challenges presented by bottle caps. If anything the problem is worse in old mining camps due to the volume and variety of this type of trash item. And unfortunately the MDT 8000 is as prone to calling these ferrous targets non-ferrous as are multitudes of other detectors. That's not a knock on the MDT, but it's a bit of magic that if present would make it or any machine stand out in these types of situations.
Some problem items, and a small brass item
One of the first non-ferrous targets I found with the MDT 8000 is some kind of very small brass.... something. A little pin-like object. I was impressed by this find before I found the gold nugget, and it alone told me the MDT had the hots needed for the job. I can only speculate how the MDT would do with a small coil... no doubt extremely well on very small targets. For now however the coil that comes with the MDT 8000 is the only one available, and since this machine is aimed at the beach market, all the push from other people seems to be for a larger coil. I'd be surprised therefore if a smaller coil is ever made for the machine. The existing coil is very good, though for nugget detecting it would benefit from a solid bottom scuff cover/skid plate, to make it less prone to hanging up on sticks or sharp edged rocks.
What about the target id on the gold nugget? I have to admit I was paying no attention to target id at all so do not know. I was just listening for any medium and high non-ferrous tones and digging those.
To sum up, I am not here to promote the Tarsacci MDT 8000 as a gold nugget detector and am not saying anyone should go out and get one just for that purpose. I would say however that if anyone has this detector, it is as capable, if not more so, of performing the task as many detectors made specifically for gold nugget prospecting. I plan on giving the detector another and more lengthy workout at another location in the future, though it may be a few weeks before I report back. In the meantime, for anyone with an interest, I recommend watching this video below by Keith Southern. Pay particular attention to the sounds the detectors makes to get an idea of what I mentioned above as regards the tones. And let's close with one more look at that first gold nugget with the Tarsacci MDT 8000.
One gram gold nugget found by Steve at trashy site using Tarsacci MDT 8000
In this article, relic hunter Keith Southern explains how to use the Salinity Balance to “punch” through bad ground, quiet down nail infested areas, recognize big iron and work around it!
You cannot Salt balance to iron the way you Salt balance to the soil, not even if it’s a little rusty Sqaure nail. This is because iron is a solid metallic object. However, you can desensitize it some, to work in your favor!
Say your on 18Khz and ground balanced. Set to disc -30, sweep around and find some iron in the site like buried nails. Small iron grunts. When you find the nails which should be easy if its a house site, a heavy concentration of them is alway's there.
Turn Salt balance on and raise coil up above the nails about a foot, bob coil say from foot to 11 inches above the nails or whatever it takes to barely hear them on the down stroke you want to find where they just start to come in weak. Just a slight wah sound. When it starts to wah pull back up.
You want to find that spot above the nails where they are weak .Right where they begin to be seen on down stroke. Start adjusting your salinity balance up a number and push down maybe just an inch but still having to keep maybe a foot above the nails. Go up a number then check with slight push.
You’ll eventually find a spot where the nails start to get weaker response. Find the spot on the dial that they are the weakest or even does not report at all on say the slight push towards them.This is the spot you want it at then stop adjusting.You can move back out of the nails and do one more ground grab.then your ready to hunt.
You'll still hear the nails as grunts, however they are not gone but they are DESENSITIZED, somewhat to the machine.Think 16 penny nails may look like a 12 penny nail to the machine analogy.Or now, a square nails looks like a finishing nail to it. Maybe not that great but to just give a picture to the minds eye !
Here's what works for me in iron on 18khz for square nails....may or may not work for you in the soil without some tweaking..18Khz, Sensitivity 7,Theshold -2, Black sand off, Salinity about 43, Ground is usually around 800 area.
Sweep speed dependent for best results.think CZ speed.
Use -30 disc to help on troublesome flip flop or ping pong iron.The machine is very good at ID'ing iron accurately.The tiny small pieces of cut nails may call you out but the -30 disc will let you know its flopping. Bigger iron nails on up are actually quieter than a VLF on falsing.
The sonar hit will also tell you its a good target VS a quick sharp ping/chirp of nail false.
Sonar hit has that good round feedback sound.
What's crazy is you'll get a get sonar hit with no iron buzz but open up the hole and investigate and you'll see alot of nails in hole too with the keeper target.
Where as say on your F75 a good hit may be also grunt hit grunt on same target. The Tarsacci isolates the good target and reports only that.Very very quick machine. If it gets a sense of a non ferrous piece it locks on it.
Also targets that are somewhat affected by the salinity balance,,,that is, very low conductors. They will seem to ID more by purity than by conductance.
Foil for example, to the machine will be different than a good alloy like gold or lead or brass etc. Now say foil, on a vlf reads 2 and a pistol ball reads well on Tarsacci the foil can be fluttery or wavy or disappear And foil reading 2 as the salt balance is neutralizing it but the Pistol ball that reads 2 will slap hard.
This is what happens to light iron some of makeup of it is desensitized and the small targets or low conductors jump out better than it can on a VLF where its reading a nail as strong .nail can overtake the pistol ball on VLF but on Tarsacci the nail looks slightly less to the circuit.....SLIGHTLY but in terms of unlocking that's a BIG step.