4) How does adjusting the
discrimination setting affect the meter readings on the MXT?
An
interesting feature to note about the MXT's ID system is that the discrimination setting does not affect the
display output. This is not mentioned in
the book or the video. No matter the
discrimination setting, the VDI and probability bar output are exactly the
same. The discrimination setting only
affects the sound output. The
engineering guide for the MXT states that the visual ID is
a bit more accurate than the audio discrimination in most cases. I have found that the best results occur when
I use all the information available - gauging in my head both the sound output
as well as the meter display. It takes a
bit of practice, but is worth it. It is
possible to find targets that are within the audio discrimination setting. I have found nickels using the display only
when I had the discrimination cranked up nearly to the max. by observing the
output on the meter, specifically the VDI meter. All three of these ID systems (target
response sound, the VDI/potential ID, and the probability bar) are independent
and all 3 should be considered in deciding whether or not to dig a target. It is good experience to learn to use that
probability bar - it helps a lot in trashy areas. Whenever you get a high probability bar
indication, it is pretty reliable. The
high reading will usually be correct, or something very similar (I have gotten
a full bar quarter reading over a penny that was probably buried at least 20
years - though nearly all other consistent full bar quarters I have dug while
coin shooting were just that - quarters).
Another
thing to note about the discrimination is that when the setting is zero, you do
have true zero discrimination - no disc at all.
This is important to know when prospecting for nuggets or beach hunting
for earrings.
5) The target ID on my MXT seems so much
more jumpy than other detectors I've used.
Why?
Many
detectors (including many by Whites) average the readings when you make
multiple passes over a target. The MXT does not - with the MXT if you make 10 passes, you
get 10 different independent readings.
This is why the MXT seems to be more jumpy on
target ID than most, if you are not used to it.
Good targets usually give pretty consistent non-iron indications. Iron and irregularly shaped junk targets like
pull tabs usually jump around and are inconsistent on the MXT ID system. Foil usually jumps
around a lot too as it is usually oddly shaped.
If you make 4 passes over the target and get 1. quarter (with low
probability); 2. Iron,
with high probability; 3. $1 with low probability; and then 4. Iron; then the target is almost certainly rusty
iron junk. If you get some consistent
good readings in trashy areas, it might be a good target close to junk. Try to isolate the good target by moving the
coil back and forth in different directions.
6) I'm having problems with
my MXT in trashy areas. What can I do?
Mixed
junk and good targets in the same spot can cause all kinds of problems with the
MXT ID system because the coil can have 2 or more targets underneath
it at the same time - so it combines readings from both. This is true for all VLF detectors and is why
some areas like the trashy parts of parks, etc.
can be the most productive - no one else wants
to hunt there.
If
there is at least a little space between the targets, most of the time iron
junk and good targets within a few inches of each other just makes the readings
inconsistent. Sometimes a target will
read one thing sweeping from one direction, and read different on the return
sweep coming from the other direction.
This all makes it real tough to decide dig / no dig in trashy
areas. Making use of the smaller MXT coils is probably the first recommended adjustment to working in
trashy areas. The small coils are very
useful in separating junk from good targets in trashy places - and the
difference is significant. The smaller coils
can sometimes find targets that are completely masked by iron junk close to the
target. The 5.3 concentric would be best
for coin shooting in trashy areas with low to moderate soil mineralization, the
4 x 6 DD is probably better in higher mineralization soils.
One
technique that I have learned to try is turning 90 degrees and making a second
set of sweeps in an X pattern over the target if I am uncertain. This technique is mentioned on the Whites MXT video, but not in the manual.
Sometimes a junk target will indicate consistent penny or $1 with but
always with lowest probability. Do the 90º turn make another set of passes from a different
direction. If the target indicates
better, dig it. If it jumps around and
shows iron or hot rock, move on. The
90º turn makes a big difference sometimes.
In trashy areas, one can use the VCO pinpoint to find the location of
the nearby targets, then choose lines of direction to
pass over the targets without passing over multiple ones. Except for a few real deep targets, it is
rare that a target will read "iffy" in multiple directions. As far as the deep targets, when working
areas where older targets may be present, probably any target at 6 inches or
deeper giving consistent non-iron readings ought to be dug. This will lead to digging a little extra
trash, but also will lead to some fantastic finds.
7) How do various kinds of
targets sound in the VCO pinpointing mode?
Coins
and other non-ferrous (not magnetic) targets tend have sharp pinpoints and go
from nothing to max to nothing very quickly, over a short distance. Iron junk tends to have large broad pinpoints
as if they were much larger than they are - they go slowly up to max and then
down - a rusty bolt will act as if it were as big as a coffee can to the pin
pointer. The pinpoint trigger can be
used to help ID targets. This same
difference in the MXT's response can be noted in regular operating modes as iron is said
to sound broader or mushier, and the sound of coins or gold is said to be
sharper or more peaked. However, the
effect is more easily noted in the VCO pinpoint modes.
8. How accurate is the depth reading in the VCO
pinpoint mode?
The
depth reading is excellent if the target is a coin or coin
sized and fairly close to the surface.
At the maximum detection depth of the MXT, the estimated depth readings are not as accurate. Remember that the depth reading on the meter
assumes a coin sized object - if smaller, the target will be shallower, if
larger than a coin, the target will be deeper.
I regularly hunt a park where there is a buried brass head sprinkler
system at about 4-5 inches. These brass
heads sound out clear as a quarter and read on the meter as being at 0 depth. However,
although they pinpoint sharply like a coin, they also pinpoint much larger than
a quarter. It takes about 2 seconds to
shove my screwdriver in far enough to find a large object at 4-5 inches, then I
know its a brass sprinkler (I've dug enough of them to know). It is safe to say that if you've dug a 4 inch
hole for a target that is supposed to be at 1 or 2 inches, and the hole is
correctly centered over the target, that the deeper target is much larger than
the coin indicated. On
the other hand, a target smaller than a coin will usually be found shallower
than the meter's depth indication.
9) I am having problems in
the VCO pinpoint mode. Any tips for a
better technique?
With
the 950 concentric, most targets, including coins, make a significant tone
change when the target crosses over the edge of the inner opening of the
coil. It is easy to get the target under
the inner opening based on the tone, and after that one can find the exact
location by doing an X pattern over the target and listening for the sound change
when the target passes across the inner edge - out of the opening and under the
coil. This technique can be used to both
locate a target as well as measure its size.
Using this technique, I can usually find a near surface coin on the
first try with my probe - if I don’t hit it on the first try, I am usually not
far off.
The
DD coils are a bit harder to pinpoint with, but still not a problem. The sensitive area under a DD coil is blade
shaped, so by making an X pattern over the target, it is possible to pinpoint a
target using the DD to a fairly tight area.
When pinpointing with either the DD’s or the concentric coils, practice
is the key to accuracy.