Geotech

If by conductive ground you mean salt/alkali, then maybe with the 17" because it has a differential RX for interference cancelation (so I am told). This should reduce the volumetric response of a salt matrix. This is true of any detector, so (ferinstance) if this same coil was available for the Zed7 you would get the same benefit. The audio was one thing I would like to have had more time to play with. In the situation I was in, my first impression was "this is awful." But in real field conditions and with more time to learn it, I might find it to be valuable. JP seems to like it, and I would defer to him on this. I would guess that the 13/18 coils are basically made like Fig 7 in Chet's first post. Fig 4 is a good candidate for the 17 coil. Whether the windings are actually spiral/solenoidal, I don't know. The depth differences between spiral/solenoidal and scramble are not all that much, but spiral/solenoidal has lower self-capacitance and much better manufacturing repeatability, so I would guess so.

Maybe a marketing dept. Anyway, the 8k coils are not toroidal in any sense of the word. They are concentrics, and the biggest improvement has been to elevate the TX coil to prevent surface magnetic saturation. The 17" coil is an interference-canceling type so it is very similar to a coaxial.

I got a chance to try the 8000, for about 2 minutes. I gotta say, the stereo audio is really busy. I think a lot of folks won't like it right off but it may be one of those things that if you stick with it and really figure it out it might be useful. Again, I had 2 minutes with it and it was set to whatever default settings, with no opportunity to explore any further.

Yeah, I've found AI to be wrong as much as right. No, there are not 5 major filters in a metal detector. Of the ones listed above, the ground filter and the motion filter are the exact same thing, it is just often called different names. The frequency filtering and EMI filtering are largely the same thing, it's just bandpass channelization filtering. The "target ID filter" is just a minor part of the noise filtering, and there are other noise filters as well.

I vaguely recall this was a problem with early MX Sports. The problem was the hold-down resistor in the soft-power circuit was too large and sometimes didn't drain the static charge off. The moment you insert the battery pack, it turns on. This problem may be amplified by the fact you had water ingress and that may have made the static charge problem worse. Question: once the detector is on, can you press the power button to toggle the backlight? If you can, then the power button is fine. If you cannot, then the power button may be stuck. If the power button seems to work, then follow the advice if cleaning with 92% (or better) alcohol.

I don't understand the purpose of the module.

Yes, it's possible to make a DD coil for the GB2.

It was a highly dysfunctional family who refused to let go of the company when they had the chance. They had a low regard for engineers and fired a couple of the key engineers, kept one they shouldn't have, and the rest (including me) resigned. That left the company with no continuity in development. They tried to rebuild engineering but the new hires had no experience in designing detectors so all of the momentum in PI and SMF just fizzled. The MX Sport was the best they could muster, and it was just an MXT in a new housing.

That would be my guess. Probably there was a SuperMax20 and SuperMax30 coils.

The early TM808 (with cave mode) was a copy of the TF900, which was a copy of the 3D Electronics model created by Jim Karbowski (Bigfoot coil fame). The later TM808 was a 6000/D Series 3 repackaged. The only detector Garrett continued was the GM24k, but they should have also continued the TM808 and the TRX. To dig a 3 foot hole in rocky soil, go to your local high school and get 2 large football players. Seriously, if you are cache hunting the guy who buried the cache probably did not dig a 3 foot hole in rocky soil, either. Tree roots are another issue, they may have not been there when the cache was buried. Hametta is (or was) still selling probes under the name Intex Systems. I have a couple of them. The only other similar device is the Gold Spear made by a guy in Sweden (guldstrom.com). It has up to a 2 meter probe you shove in the ground, if it contacts metal it beeps. It's made for sandy stream beds, you are unlikely to have success in rock ground.

It's a Coinmaster 5000/D Series 2, most likely produced by the Inverness factory for the Euro market. Inverness did this a lot, they would take a design from Sweet Home, make some modifications, and create a new name. They often bought the parts from Sweet Home and assembled the detectors in Scotland. No idea on the SM20/N/SM30 switch, never seen it before.

Depends on exactly what I'm looking for and exactly the ground conditions. Generally I'd probably prefer a PI with a 1m coil if obstacles aren't plentiful. Maybe a TM808 if maneuvering is difficult. A TF900 or old TM808 with cave mode (pure TR) if I want to do ground mapping.

@Norvic, I don't have a GM2k so I'll use an Eq800. When you make an FFT on the oscope you want to use a lot of waveform cycles to increase the resolution bandwidth (RBW) of the FFT. In the plots below, the first has roughly 2 complete waveform cycles and the RBW is only 2kHz, which makes the FFT look blobby. In the second plot I've increased the time scale to capture 20 cycles and the RBW is now 200Hz, and the FFT is starting to look useful. The final plot is another 10x increase in the time scale, the RBW is 20Hz, and the FFT is very sharp looking. For the pickup coil, you don't need a 1/2 wavelength or anything close to that; metal detectors work in the near field, not far field, so there is no EM wave to capture. For the plots above, I wrapped 20 turns of 0.5mm wire around the nearest available coffee mug (~90mm diameter) and used this as a pickup coil. It's also important to add a parallel damping resistor (~1kΩ) or it will ring terribly. On a Faraday cage, here is the one I used at White's: It was about 8x8x7 feet with 2 layers of screen mesh: one copper, one steel. Oddly, just the steel or just the copper would not do the job, but the combo would. We had 2 of these in the factory, mostly to eliminate detector-detector interference when testing 2 detectors at the same time, but it also helped with other EMI. The noisiest place to test a metal detector is a metal detector factory.

That signal doesn't look right at all.

Facebook Marketplace eBay Various detector forum classifieds Also try metaldetectordistributors.com, Ettore used to be one of the biggest movers of the TM808 for White's. Maybe he still has NOS (unlikely) or refurbs or trade-ins.