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Date Posted: 13:24:31 03/29/02 Fri
Author: Steve Herschbach
Subject: Re: GMT - SAT ?
In reply to: Ralph 's message, "GMT - SAT ?" on 12:35:28 03/29/02 Fri

Hi Ralph,

The GMT does have a totally new SAT.

Now, my take on auto-threshold is that is simply smooths out variations in the threshold. In theory the faster the SAT speed is the smoother the audio should get, but at a loss of sensitivity to smaller signals because they are also smoothed out. The older SAT units lost lots of depth at higher SAT settings.

The GMT has a new SAT that is created through software in the microprocessor. Supposedly to create less loss of depth at higher SAT settings. Whatever.

My point is this... the GMT introduces it's own static as the SAT is cranked up. I never noticed this on the older units.

This is not likely to be an issue normally. But for my bench test style quartz sampling with the detector jecked to the max, I noted the threshold getting much raspier as the SAT was turned up. At full gain, audio boost on, the machine is ''quieter'' at SAT settings below 2. Turning the SAT up does introduce a smoothness but at the same time a static is introduced.

This is with good headphones of course. I've tried this with two units, same results. It's milder with the stock coil but is there. It is much more obvious with the small coil.

The static introduced at these kind of ''hopped up'' settings was such that I got better bench test results on the gold ore at the lowest SAT settings.

I do not have an older Goldmaster around at the moment. Can someone please get one, plug in headphones, go full gain, audio boost on if available, set SAT at lowest, bare threshold, then run SAT up and note results? In theory the threshold shold go from a poppy, spiky sound to a smoother sound with no outside noise introduced. If has one of these machines and a GMT to make a direct comparison it would be helpful.

I can't see this being an issue in the field, but any introduction of ''outside noise'' whether by electronics or software is not a good thing.

In any case, I have always run the SAT as low as possible in the field while still getting a threshold I can work with. My old Compass Gold Scanner Pro had an auto-threshold so slow you had to really work it slow, but it sure got great depth. So I tend to always push my SAT settings slower, not faster.

Steve

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