John,
I only ran the in house air test on the gallon paint can as an example. Tesoro Super Trax and Minelab xt 18000 both with standard 10 inch elliptical coil, both got about 26 to 27 inches. A modified Tesoro Bandido with 7" coil, about 23 inches. A Discovery Coin Trax 8" coil about 27" (with autotune on), a Garrette 450 coin machine 8 1/2" coil), about 26" (had to hold button to activate all metal mode). I did these to show how the coil size can influence air test differences.
I had to run the Goldscan test outside, got about 36 to 37 inches. Too many gadgets running, and too small of a house to get a true reading.
Your idea of air testing is a good one, but I would like to add a word of caution. I ran a similar test about 10 years ago with several detectors using similar objects, including a quart jar of coins, a regular size tin can, and a gallon paint can. At that time I experimented with a Whites, a Tesoro, a Technetics, a Bounty Hunter (made by Technetics),a Fisher, a Garrett (I think, but may have been a Compass), and a pulse unit. The pulse unit was of German design.
At that time I also found you can increase the appearance of increased depth capabilites by digging a hole in the ground and leaving it open. I had several detectors that could see a one gallon paint can which was 3 feet down to the top of the can, with the hole open. I filled the hole and only the pulse unit could barely detect it, and that detector had a much larger coil.
Earlier when I mentioned I compared depth capabilities of the Goldscan and the SD I mentioned I buried the objects. I also re-packed the dirt. The reason for burying the targets and repacking the dirt was to get more accurate real environment indications. I have found air tests and buried tests show significant depth differences, especially in mineralized ground. Even failing to re-pack the dirt can make a slight difference.
Testing metal detectors is fun except I am getting too old to run out and dig a three foot deep hole. I have been using them for over 30 years, actively testing them for 18 or so years, and seriously hunting for gold for about 14 years.
My experience tells me that I may not be able to tell you the model of your detector, but I suspect I know the name of the company.
It would be fun to have people try a buried test also, but not in the house. Wives might get upset. Just kidding.
Reg
