here is an article I wrote for my website, you may find interesting:
Coin garden testing with Etrac and SEF 6x8 coil
Ok tonite I spent some more time testing.........I was using the etrac and had on my 6x8 SEF coil
the coin garden was set up 4 yrs ago and coins are at a measured 7.5" and as on large plastic plates to prevent turning, sinking etc.
I started in auto +3 (etrac was at 19) and I could hit on them but barely, so I flipped it in to manual 19 and it screamed out on the coins easily, so i backed it off to 18, 17, 16, and still could hit them, when I went to 15 it could still hit on the quarter but struggled out a kerthunk over the dime and penny.
I tried fast on, fast off, deep on, deep off....tried them BOTH ON at once, but OFF at once. And still I am convinced that Fast ON and deep OFF gives the best most consistent readings, I passed over these targets over and over and over........
I tried difficult ground, normal etc.....did not seem to affect readings good or bad,
then I tried smooth response, long, and normal. Smooth works and sounds GREAT on the deep targets but real crappy on shallow targets, seems like it would be VERY hard to pinpoint shallow targets in smooth, Long was horrible to me regardless. I still prefer normal.
From my testing on sensitivity manual of 19 with the 6x8 coil is every bit as powerful as 24 when using auto +3, that was a little shock to me, signal in 19 manual was more clear and crisp than 24 in auto +3. So if your in an area and can ONLY get manual 19, trust me it goes pretty DEEP
Yes hard to believe, so i tried it over and over and over....lol
So from this test I decided that I am gonna do something that is have MORE confidence in using my 6x8 coil in yards, not being worried I will miss deep coins. Because my coin garden has only been there 4 yrs, I can imagine how much better a coin will sound out if it has been there 75-100 yrs. But just with 19 manual I should safely be able to detect 80% of the coins in my area, most oldies here are 5-7" range. And I should be able to push it to 22-24 manual in most yards without trouble, in case there are some real deepies.
And I also decided that the current setting I am using are still the BEST for ME in MY soil in MY area.....maybe not in your area but for me, deep OFF and Fast ON and normal response is what I choose to stay with.
Hope this was not too boring of a read for you all.