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Geotech

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  1. C59 & C60 need to match each other in value to 1% or less. Otherwise GB will be noisy. Reg was shorting C50 which does eliminate a high-pass filter stage. I've never tried it but see no downside to doing it.
  2. There are 3 modes: Vibe only Beep only Beep+Vibe For each mode, there are 3 sensitivity settings.
  3. F-Pulse has no volume control, it always runs at max volume. If there was anything I could do to make it louder I would but it is limited by the mechanical enclosure. Same with the vibe strength. I am utterly shocked that a factory reset would have any effect whatsoever on volume or vibe strength. No idea how that could be but if it worked, then good!
  4. I had a QED (PL3) on loan for a while and, honestly, I was a bit disappointed with it. I considered it a little better than the TDI, but not as much as I expected. I found it to be noisy and temperamental, and the weird 2-step threshold adjustment was just awful. This particular unit didn't have the 3D printed parts I've heard about, instead I found the mechanicals to be perfectly reasonable. In any case, the Impulse Gold was clearly outperforming the QED in the tests I was able to do. Given that Garrett did a really nice job on the Axiom (way better mechanicals than we can do) I would expect to be south of the Axiom price. Some PI detectors have simpler designs that are cheaper to build. I designed the TDI-SL to sell for $999 MSRP and it could have been sold for $600 with good margins. Probably the Sea Hunter, even with that enclosure, is not expensive to build. The Impulse AQ (and Gold) are difficult to build, especially for FTP which is accustomed to mass assembly-line production. We are still struggling with the AQ, which is why it's been such a challenge to ship detectors. That's one of the key issues to address on the Gold before it goes into production.
  5. The HaHa emoji is probably appropriate, too. That's what most folks think of when they think of FTP.
  6. Hartley oscillator, which is pretty tolerant of the coil tap. But getting the 3 coils more closely matched may be more critical.
  7. There is an "Impulse Gold" in development. I field tested it in June and it works pretty well, sees sub-grainers about the same as the SDC. There were some minor issues that needed addressing and FTP moves at glacial speeds so that's still in the works. Otherwise, there are other developments on the VLF/MF side but I have no exposure to those.
  8. This is sad news indeed. I worked with Eric a lot and had hoped to visit with him one more time but then Covid arrived. Eric's willingness to share his knowledge is a key reason Geotech was created and also why I have spent most of my time focusing on PI technology. He was not only generous, he was a very kind man. I will miss him greatly.
  9. I'll betcha I'm the only other person here who found this interesting. I had a White's BFO with a Triplet coil and was curious what made it a Triplet coil, but not curious enough to destroy the coil to find out. Thanks for the tidbit, curiosity satisfied.
  10. Without knowing for sure what the mods were, it's just a guessing game. Since the TDI PCB is mostly surface mount trying out those guesses is difficult and potentially damaging. You really need to find a modded TDI and look inside.
  11. Sorry, I don't know what was involved in the threshold mod. When I was designing the SL Reg suggested a modification to the design of the SAT amps that resulted in a smoother threshold, so I suspect this might be the mod he was doing to the TDI. However, he also had a mod for the SL whereby he removed the changes to the SAT amps, and I don't know why.
  12. For those who forego headphones in order to hear snakes and such, I use "transparent" Koss UR40 headphones. They are "transparent" because they don't block outside ambient sound so you can still hear everything around you but the detector response is right in your ear. I've played around with those tiny speakers and tested maybe 20 different ones. I thought they sucked and would make for very poor detector audio, even with the speakers pointing at you. It's possible they could be made better with a proper acoustical chamber design (in the same way Bose can make a mundane speaker sound phenomenal) but that's not my expertise and probably not a skill with any detector manufacturer. So the answer is to brute-force it with a big speaker, and that means putting it where it will fit, usually pointing out the back.
  13. MAP pricing was created back in the 1970s to deal with mega-dealers like Kellyco. It was intended to create a level playing field between them and the mom&pop dealers. You could not advertise a detector for less than MAP but you could sell it for less than MAP. To skirt the advertising restriction dealers often added a bunch of accessories "for free." Usually they were junk, but it's the illusion that counts. Detector companies usually have the policy that they will not compete with their own dealers. So if the company sells direct, it is usually at MSRP and not MAP. I think what may have happened is that the T2 had been listed at MAP and now it's been raised to MSRP. Typically MAP is 80-85% of MSRP. Their price is correct. This is a special edition "audiophile" version of the coil. It uses oxygen-free copper Litz for the winding, the housing is carbon nanotubes formed under the heat and pressure of the sun, the cable has double defluorinated Teflon coaxial cables using niobium-germanium conductors with a polymorphine SuperFlex jacket, and a titanium connector housing with beryllium contacts. It performs exactly the same as the standard coil but allows the owner to sneer at those with lesser equipment.
  14. Todd at CentervilleElectronicsWest tells me that he has a new source for replacement TDI battery packs.
  15. The exact same PCB was used in all those TDI variants. I don't recall if the software was modified for a fixed pulse delay or if it naturally defaulted to 10us. Plug in a pot and see what happens.
  16. Yes, that's exactly the plot I was thinking about, thanks!
  17. Nice plot, GB. Pimento, I was looking on Geotech for the very plot we're probably both thinking of, can't find it. Locator, that illustrates it quite nicely... a big coil will go deeper for big objects than a small coil. Ferinstance, if you want to detect a deep ammo box full of silver, use an 18" coil, not a 6" coil.
  18. In a nutshell: Big coil = more depth on big targets, less depth on small targets, worse separation Small coil = more sensitivity to small targets, less sensitivity on big targets, better separation Concentric coil = Slightly better depth, easier pinpointing, worse ground handling DD coil = Slightly worse depth, harder pinpointing, better ground handling There is way way more to it than this, I would need to write 3 chapters to do it justice.
  19. What Phrunt talks about is EMI interference and can be used to trace an active power line. The V3 has a frequency offset control that you normally adjust to make it quiet to EMI; instead, you want to get near a powerline and adjust it for maximum interference. Try it in MF mode and each SF mode to see which is most sensitive, my guess would be the 2.5kHz mode. If you have access to an end of a pipe or cable you can inject your own signal and trace it, again using interference. The signal generator needs to have fairly precise control because you want to tune it to the operating frequency of the detector (say, 2.5kHz) and then move it a few Hertz off for maximum interference. Connect the (+) signal to the pipe/cable, and connect the (-) signal to a ground probe that's 10-20 feet perpendicular to the pipe/cable. Obviously, never use this method on a live cable. If you need to trace a PVC pipe, it alone can't be detected but sometimes smart installers lay a tracer wire in with the pipe. Where the pipe comes out of the ground, look for an unconnected wire sticking out. If you find one, go thank the guy who installed it.
  20. It's an example of exceptional marketing. MF has an inherent disadvantage in that it is, by necessity, a wideband system which is more susceptible to EMI. But with both SF & MF it depends on how well it's designed.
  21. As mentioned 100 or so times on these forums, BBS & FBS are 2-frequency detectors, not 17 or 28.
  22. The SL board is a newer design and has some changes to make it quieter. It was intended that the TDI would switch to the SL board but it never did. The SL board has more options for mods. Yes, lowering the cap values makes the demods faster with a slight loss of depth. I would leave them alone, I'm not even sure why Reg lowered them on the SL as it also tends to be noisier.
  23. Compare your Minelab curve to the price of gold over the same time span and you'll have your answer. A very large percentage of ML revenue is in African gold prospecting and sales there are very dependent on the price of gold.
  24. I'm not sure what you mean by "turntables." In the TDI, C59-C60 (same as C20-C21) are already 0.22uF but you could decrease them to 0.1uF to equal the SL speed improvement. The 2 caps need to be matched to 1% or better. The TDI has no C56 or D20-21, and C42 is C50 in the TDI and can be shorted. I'm not familiar with the other mods in Jim's post. I think the preamp replacement was the LME49990 but without some other changes just replacing the opamp won't do much.
  25. Jeff, it's likely that something in the transmitter popped, maybe the TX FET overheated. Components should be able to handle up to a 20V battery but there is a chance that a high battery voltage will cause the TX to run hot. Unlike the TDI, the FET on the SL does not have a heat sink, rather it uses the PCB as a heat sink. I'm surprised that 14V caused a problem. Let me know what you find out from Todd.
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