I've been using one on the beach for about a year, so I'm not the consummate expert but I do pretty well. Here's my settings:
Disc: 0
Notch: 0
Mode: disc
Tone ID: variable
Volume: if you have volume adjustable headphone, volume full high and adjuct the headphones, otherwise adjust volume on the unit to suit
Sensitivity: start out at the "beach" setting on the dial. Sensitivity is increased when turned counterclockwise, which is counterintuitive. In stable sand, increase until you start to get false signals, then back off a bit. That will give you max depth. Most times you'll bee between 10:00 and 2:00 on the dial.
Threshold: Set as far to the left as you can and still get a smooth tone.
Put your control box in a plastic bag if you intend to get anywhere near the water. Feel free to PM me if I can help more. You have a GREAT all round machine, capable of anything you ask of it, sand or dirt.
VBDave
