Expecting too much or a dud?

[JohnApthorp]

I recently went out & buried a 1.5gram piece of lead fishing sinker at a depth of 3 inches in fairly quiet soil. The purpose was to test my wife's AT Pro & my AT Gold with a variety of coils. This is not a test to compare detectors, just to test the coils on the same target at different depths. The results surprised me. (All coils were genuine Garrett coils)

Test 1.
Lead at 3 inches.

AT Gold using the STD 8" x 5" coil - detected the target 100%..........Target buried at 6inches - Not detected.

AT Pro using the 8" x 5" coil - detected the target 100%..........Target buried at 6inches - Not detected.

AT Gold using the 9" x 6" coil - detected the target 100%..........Target buried at 6inches - Not detected.

AT Pro using the 9" x 6" coil - very "Iffey" detection - 25%..........Target buried at 6inches - Not detected.

AT Gold using the 11" x 9" coil - detected the target 100%Target buried at 6inches - detected the target 100%.

AT Pro using the 11" x 9" coil - detected the target 100%..........Target buried at 6inches - Not detected.

Test 2.
A $1.00 coin buried at 6 inches.

AT Gold using the STD 8" x 5" coil - detected the target 100%

AT Pro using the 8" x 5" coil - detected the target 100%

AT Gold using the 9" x 6" coil - detected the target - just - 25%

AT Pro using the 9" x 6" coil - Target NOT detected.

AT Gold using the 11" x 9" coil - detected the target 100%

AT Pro using the 11" x 9" coil - detected the target 100%

Unfortunately I forgot to test the 4" sniper coil.(Onset of "Oldtimers" disease I think - Doh!)

I did honestly expect better performance from the 9" x 6" coil. I realise that the AT Gold operates on 18khz & the AT Pro operates on 15khz but I've been led to believe that the coils are inter-changeable.

Has anyone else compared this coil? If so, what were the results?


Thanks for any sensible advice - did I get a dud or am I expecting too much?

PS: I did a full factory re-set prior to doing all the test. All metal mode was used with the sensitivity at 2 bars below max. (Used at full if target wasn't detected.) AT Gold - All metal mode, AT Pro - in STD at Zero (all metal) New batteries in both machines.

Gary.

 

[MikeLab]

Freshly buried targets do not detect as deeply. The AT Gold can detect a pull tab at nearly five inches with the sensitivity level at two bars with the 5x8. Larger coils work better for larger targets. They read more ground and this can actually work against detecting smaller targets. Ground balance over clean ground is most important. My feelings are many people do not take precise ground balancing seriously enough. Larger coil even more important. Then there is coil control.

 

[grumpysrb]

There are advantages and disadvantages to both large and small coils. You choose which is best for you and go with it.

 

[jbr13]

Gary, From what I have gathered the 9X6 coil is a concentric coil vs the other two being DD coils. I would guess this is where the difference in depths are coming in, and plus the AT Gold being a little more sensitive than the Pro.

Here is a link on coils that may help. http://www.garrett.com/hobbysite/hbby_searchcoil_tech_sheet.aspx#

 

[grumpysrb]

What settings. I have never had trouble detecting a small target at 6 inches. But I use full sens or 1 bar below most of the time. I don't understand the 25%, is that it detected one out of 4 times?