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Spectra VX
3
User’s Guide
Ground Filter
Modern VLF metal detectors use electronic filters both to
remove unwanted noise — such as electromagnetic interference
(EMI) from radio signals and power lines — and to remove the
portion of the received signal due to ground mineralization (see
Chapter 1). Different filters offer trade-offs in performance.
Severe mineralization usually requires more filtering which can
affect depth. High EMI likewise requires more filtering. The
type and amount of filtration will usually affect loop sweep
speeds.
VX
3
allows you to choose between two filter settings:
• 5Hz Bandpass — Lower mineralization, good EMI rejection,
allows slower sweep speed
• 12.5Hz Bandpass — Higher mineralization, good EMI rejec-
tion, requires higher sweep speed
Most programs use the 5Hz Bandpass filter as the default. This
is the best overall choice for low-to-moderate mineralization,
has good EMI rejection, and allows for a slower sweep speed
while still working well with faster sweep speeds. In extreme or
highly variable mineralization
VX
3
can become chattery when
sweeping the loop; the 12.5Hz Bandpass filter may help.
