OK, now this is how I set it up, can't say if everybody agrees with me. I feel it's the deepest and most sensitive way of using the 2500 in AM. Mind you it does take getting used to (it's not as bad as you think), but if you stick with it, I think you'll be surprised. First switch into the AM mode, then turn <STRONG>"off"</STRONG> auto-track (that's right, turn it off). The 2500 runs much more stable with it off. Set the threshold to a little more than a hum so you can hear the changes while manually GB'ing. Make absolutely sure that there is no metal or high mineral deposits under the coil for a few feet around, excluding your boots. Unless you plan on hunting with the coil way out in front of your boots, I GB with the coil out in front of me the same distance that I normally swing it. Manaully GB the machine to neutral for starters. After getting used to hunting like this, then I would go back and try GB'ing to <STRONG>very</STRONG> slightly possitive <STRONG>and</STRONG> (here comes the screams) very slightly negative. I've hunted both ways and have quieted down the machine while negative without any real bad effects, except for some hot rocks and ID'ing a bit off. Go back and set the threshold to a <STRONG>slight</STRONG> hum. I also turn "on" the imaging. This might be a bit much for novices, but I feel it's a great feature.
<STRONG>Note:</STRONG> If the mineralization in the ground you're hunting changes a lot, or if you don't want to go through all the above steps to GB, you can always push and hold the AM button and let the 2500 GB for you. I do this in certain areas, and the 2500 will get it pretty darn close to what you get manually GB'ing. Also, you don't have to go in and out of the modes to change the threshold while setting. Go up and down from about 8" to 1-2" while holding the button, and <STRONG>give it time</STRONG> to do its' thing. You'll see the bars moving around 'till it settles down, then it's ready. Whether you release the button near the ground, in the air, or somewhere in between, you'll have to experiment with. Where I hunt it does make a difference, leaving the final setting slightly negative or possitive. Don't sweat this part, it'll be pretty close, you can play with this later.
You will get the bu-bu-bu almost constantly while hunting this way, <STRONG>but</STRONG> it's a lot more constant and less erratic. You'll soon learn to live with it, and when you go over something (even small and deep), you'll know it! You may also want to set the tone to "3", as to me it's a lot easier to deal with than a higher tone. Oh, and use good headphones with the volume not too loud.
A totally different way to use AM is to turn "on" the auto-track, but then turn the threshold down way below silent. I've had it at 5.6 and it does still goes pretty deep, but I feel it's still too erratic for my liking, and less sensitive.
For the record, these are the other machines I own and use, and the 2500 (running in AM) is my depth machine by far.
Whites IDX Pro (modified with manual GB & adj SAT speed)
Tesoro Bandito II MM
Tesoro Golden MM
Fisher CZ-20
HH
Tony (L.I.)
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