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CONTENTS
Double-D Modes
Double-D Modes manage noise from EMI or conductive (salty) ground when using the
GPX 14™ Double-D coil. These modes are only available when a Double-D coil is in use.
A Double-D coil has characteristics that allow it to cancel out EMI and conductive (salt) signals. A Double-D coil contains two
back-to-back 'D' shaped copper wire windings that overlap in the centre of the coil.
The GPX 6000™ can sense targets in each of these two windings. EMI, conductive (salt) signals, and targets all produce
a different response in each winding that can then be compared. EMI signals produce mostly identical responses in each
winding because they are from distant sources. Salty soil is effectively a large and relatively uniform noise source, hence it
produces a larger signal in one specific winding (the transmit winding). In comparison, gold nuggets produce a very different
response in each winding as the coil moves over them. The signal from the nugget varies depending on the detector swing as
well as the nugget depth.
By subtracting the response from these two windings in different proportions, the detector effectively minimises the
response from distant EMI or conductive (salty) ground. This subtraction also affects target responses. The response from
deeper nuggets is reduced, while shallower nuggets are mostly unaffected. This means that a Double-D coil can be set to
optimally cancel either EMI or conductive (salty) ground. Sensitivity to shallow targets will still be quite good in either case
but deep targets will be more difficult to detect.
Set the Double-D Mode
START `
1. Press the Noise Cancel button
for at least 2.5 seconds.
(Default)
Long press for at
least 2.5 s
Long press the Noise Cancel button for at least 2.5 seconds to
toggle between the two Double-D modes.
The icon for the currently enabled Double-D mode is displayed.
Choosing the Right Double-D Mode
EMI Cancel (default): use when noise is caused by atmospheric interference.
EMI is noise that is present when holding the coil stationary.
Conductive Ground Cancel: use when noise is caused by interference from conductive (salty) soils. Conductivity is the
cause of noise that is present when raising and lowering the coil in the air between knee and shoulder height above
the ground.
Double-D Mode Guide
EMI Cancel (default)
Reduces the effect of EMI.
Conductive Ground Cancel
Reduces the effect of conductive (salty) soils.
Use when detecting:
`Near power-lines
`In stormy weather
`Close to other detectors
Use when detecting:
`In large open gold fields with conductive (salty) soil
`In wet ground
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