van0014

I've been unlucky enough with the V3i that the preamp gain setting and sensitivity can't be set high anywhere. I suspect they don't have good noise rejection. You could adjust those settings to see if it helps with the interference. Just take a note on the current settings for pre amp and sensitivity, so you can change back without resetting the profile. These detectors have an awesome level of control, and thankfully you can make lots of profiles and reset them individually

Properly comparing the two should involve understanding the fundamental principal used for each detector's version of MF signal processing. Some do it well, and others don't. I'll focus on multi frequency, since it might generally be considered less sensitive. It's an engineering challenge to effectively get the most out of MF, so the advantage depends a lot on the specific implementation. The Rx signal must be properly handled in an MF detector. It's very complex. Because of the wideband nature, there's a wider spectrum to filter and process. If MF has a loss in signal strength, that can be compensated by boosting the Tx signal at the cost of battery life. Low quality MF detectors would be expected to underperform, if such detectors don't properly transmit or process the signal. It takes a good deal of R&D to get MF working at it's best. The White's V3i is an example of a good attempt at 3 simultaneous frequencies. It's not modern anymore though

So it must be a proprietary chip? I found no info about what it could be, but could remove it from the board and follow traces and datasheets to try and find out. That takes a bit of dedication to do though, looking through a sea of datasheets. So normally people who do it have more experience than me, and can narrow it down from PCB layout and supply pins I'm ambitious, and think there's still a chance for an aftermarket coil. It seems unlikely for minelab to make their own IC. So it could be an easily available IC that needs a little work on PCB design to make a working coil. The patent for GM1000 talks about operating the coil in resonance, or possibly in a phase locked loop. A bit of R&D is probably needed to make coils of a different size. The passive components could be optimized for the standard coil design. As an experiment, I could adapt a 12" detech coil to see how it behaves with the GM05 IC. If that works ok, then replicating the PCB would be the main challenge for aftermarketting, instead of needing more thorough R&D or reverse engineering. The IC has 5 input wires to the coil, Tx, Rx and shield. That'd be a cool experiment. I'd want aftermarket for the sake of getting deeper targets Edit: I tried the 12" coil. It was detected and sensing targets, but for some reason couldn't get any deeper than the stock GM10 coil. I'm guessing the IC or the circuit on it is tuned for the GM05 coil it came from

The GM1000 coils have an IC onboard. I've taken apart a GM05 just to see what's in there. Long ago, I threw away the coil but kept the PCB. The wires were very thin, but didn't appear to be litz, as is normally assumed. The IC reads: LGHN N885 649 Hard to tell what that main IC does. Surely it couldn't handle both the ADC and DAC. The top pins come from the detector