PI user request

[Anonymous]

Hi All
As a user of Minelab PI detectors there are many things that are of concern regarding the depth penetration of PI detectors in field conditions. A debate way down on this forum under the heading "Detecting nuggets under Red Clay" highlights some of the problems of in the field use. It would certainly be interesting to hear from Dave Johnston and Thomas Breuer etc. regarding the problems in getting a signal back from a deep target in mineral soil.
I recently did some testing with a CRO and a coil and various Minelab SD and GP detectors and was truly amazed at the distance the signal was able to travel through the air. I know about all the losses in receiving a signal back from a weak deep signal but this is where I think that the most improvement in detector technology is possible. Power saving ideas are fine but as a user I would like have a detector that can get down to where the deep nuggets are. There must be thousands of nuggets out there that are just out of reach of the present crop of metal detectors.
So how about some comments and ideas on how greater depth can be achieved.
Cheers
Steve D

 

[Anonymous]

Steve, the problem of "red clay" etc. may seem like it should be a single problem with a single solution; however, it involves several physical mechanisms which don't have a single solution other than turning down the sensitivity control-- but then, that wasn't the solution you were asking for, was it?
Right now, as far as I know, Minelab is the only company manufacturing metal detectors which attempt to cancel "red clay" and "black sand" simultaneously. The results ain't pretty, but they are sufficiently effective to be useful.
The methods for doing this have been fairly widely known in the industry for some time. About 1985 I build a prototype PI that would work black sand and red bricks quietly while finding metal. I believe others were doing it in England prior to that, although I didn't know it at the time.
I suspect that when some other company takes the problem of "red stuff" seriously, whatever solution they come up with will probably be about as effective as Minelab, and probably about as user-unfriendly, all for the same reasons. (I'm referring to the issue of cancelling the red stuff, and not other unrelated issues of product desirability.) I have a few ideas about possible improvements (sorry, can't discuss them here), but they're just details, no huge leap forward.
Minelab made cancelling the red stuff a high priority because the Australian market is primarily gold prospecting and because of the widespread occurrence of maghemite clays and laterites in Australia. The weird responses that result from cancelling the red stuff were a price worth paying. Here in the U.S.A. the primary emphasis was, and still is, on coinshooting/relic hunting machines, where discrimination and target ID features are more important than ground cancellation.
--Dave J.