White’s Electronics Spectra VX3 - Manual (Page 39)

Page 4-2
Spectra VX 3 User’s Guide
One reason for using multiple frequencies is that some tar-
gets respond better to certain frequencies than others. Targets
that are thin and made of low-conductive metal — typical of
most jewelry — respond better to higher frequencies, which is
why many gold nugget detectors are designed to run at much
higher frequencies than most other detectors. High conductive
targets, especially those that are thick, respond better at lower
frequencies. Also, ground mineralization has a weaker response
at lower frequencies, resulting in better ground penetration in
highly mineralized areas.
Three Frequency
The default frequency mode for most programs is standard
Three Frequency . In this mode, VX 3 simultaneously transmits at
2.5kHz, 7.5kHz, and 22.5kHz. 3-frequency mode gives the best
overall response to the broadest range of target conductivities.
In any frequency mode VX 3 will plot the VDI responses in
the SpectraGraph screen and also calculate an overall VDI
number for the target. In 3-frequency mode the results from at
least two responding frequencies must agree in order to display
the VDI number and generate a tone response. This helps mini-
mize false positives.
Salt Compensate
Salt Compensate mode is the same as Three Frequency