New AT Pro.

[twotap]

Received AT Pro Saturday ground balance shows 91-92. How would you rate that soil? mild, mineralized? Any advantage to manual GB such as a bit + or -?

 

[Turak]

That's about like mine in a lot of places.....some go as low as 85 some as high as 94. That's using my 8 x 11 DD coil.

It would be considered 'Highly mineralized.

Typical Ground Balance Ranges:
80–99: Highly ferrous (magnetite, ferrous oxide minerals,
black sands, hot rocks, terra cotta)
60–80: Moderately mineralized soils (red clay, brown clay,
iron-bearing clay minerals, etc.)
20–60: Likely an iron object
0–20: Highly conductive, non-ferrous minerals such as
saltwater

Which means a few things;
Your going to lose a little depth because of it no matter what coil you use.
Your probably going to get a little better depth with the DD coils than with the concentric coils.
Iron masking may give you problems in extreme areas (hot rocks, black sands, etc.
etc.

Don't worry though, it's not typically much of a problem, if at all.....

I hit pennies, dimes, quarters, etc at 10 inches + with no problem using the 8.5 x11 DD coil.......
sometimes a little more, sometimes a little less depending on the soil conditions (moist vs dry) , item type , resting angle if a coin, etc.

Always a good idea to ground balance when switching areas, soil types, dry vs wet, etc.

Especially if you change the coils. You WILL get different GB readings with different coils 8.5x11 vs 5x8 vs etc and different machines (AT Pro vs AT Gold).

 

[mtdoramike]

Manual ground GB is usually good for mineralized soil like beaches. Some I have had to go alittle positive and some slightly negative to help with the chattering.


mike

 

[JLJLochland]

Have you ever been in an area where the mineralization changes so many times in 50 or 60 feet that you could not keep it balanced. I didn't know what to
do except to reduce sensitivity and hold the detector farther away from the soil. Nothing really worked, and I finally gave up.

 

[Turak]

I've seen a few areas like that where they had filled an area in. They must have had multiple dumps with different trucks/types/sources for the top-fill.

That is one area where the AT Gold has a feature the AT Pro does not.......Adjustable Ground Balance Window. NICE feature.

IT is what is says.....basically you set a window with a value ranging from 0 - 6. So this effectively spreads the ground balance over a range.

So lets say you ground balanced and it was 90 AND you had the ground balance window set to 5. the number sets both the + and - range.

This would make your 'effective' ground balance 85-95.

Here is straight from the AT GOLD Book;

------------------------------------------------------------------------
Adjustable Ground Balance Window™—Experienced
prospectors recognize that mineralized ground is often a
mixture or matrix of different soils, rocks, and pockets of
concentrated mineralization, each possibly requiring a slightly
different ground balance setting. In such cases it may not
be possible to find a single ground balance setting that
simultaneously balances to the different ground components.
This is not a result of limited ground balance resolution; rather,
this is due to localized variations in the ground minerals.
For conventional detectors operating in All Metal Mode,
these ground variations can produce subtle audio responses
that reduce the operator’s ability to discern faint signals,
resulting in missed targets. Even detectors with continuous
ground tracking cannot compensate for these localized
ground variations.
Garrett has addressed this issue with its adjustable
Ground Balance Window which allows the operator to
effectively “spread” the ground balance setting in order to
simultaneously ground balance to a range of values. This
smooths out the audio by reducing the subtle ground
responses and allows the operator to hear those faint targets.
To access this feature, press and release the GND BAL
button to enter Manual Ground Balance mode. Use the (+)
or (-) IRON DISC buttons to adjust the GB Window between 0
and 6 as displayed on the LCD above IRON DISC. Press and
release the GND BAL button again to exit this mode. Note:
adjustments to the GB Window take effect only after exiting
Ground Balance mode and apply only to the All Metal Mode.
To optimize the setting, switch to All Metal Mode, ground
balance the detector, and set the GB Window to zero or a
small value. Then exit to All Metal Mode, sweep the coil
over a clean area and listen for ground responses. If ground
responses occur, increase the GB Window by 1, exit to All
Metal Mode and sweep the coil again. Repeat this process
until the ground response reduces to an acceptable level.
It is recommended to use the minimum GB Window setting
needed. Using an excessive setting could reduce sensitivity
to faint targets. The default value of 2 is optimum for most
conditions.
As described above, this setting allows the detector to
simultaneously ground balance to a range of values. For
example, with Ground Balance set to 83, and the GB Window
set to 2, the ALL Metal Mode will be operating with an
effective ground balance spread of 83 ± 2 (81 to 85); thereby
minimizing the subtle responses caused by ground variations
within this range. This feature can even be used to reduce the
response to some hot rocks and terra cotta.
With the GB Window set to zero (0), the AT Gold will operate
like a conventional All Metal detector.
---------------------------------------------------------------------------------


Using an AT Pro, not a lot you can do.

I have found you can try the following, in order of possible helpfulness;

Turn down your sensitivity a notch or two.
Manually ground balance it a bit (+ or - , usually negative 5 or so) one way if that does not work try the other way.
Use a smaller coil.
Try a changing frequencies, but probably won't help much in this case.