Sensors & Software pulseEKKO, Product Manual

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Appendix B
221
The radar electronics clip any signals above the 50 millivolt level. Diagram b) shows the type of
result that will be measured if clipping occurs in the signal pre-conditioning circuitry. When this
data is finally high pass filtered, a blank zone in the area where the original signal had a large
wow above the clipping level of the electronics can appear. This results in a blank section on the
record with no reflections visible.
In the second case where signal saturation clipping occurs, there is no software correction for
this. You must be aware that this can occur in some geologic settings and the antenna spacing
should be increased to reduce the wow signal amplitude below the clipping level of the receiver
electronics. You can also reduce the transmitter voltage if you are using a Variable Power (VP)
transmitter. As a best practice use an antenna separation at least equal to the length of the
antenna being employed. For example, 100 MHz antennas should have an antenna spacing of
at least one meter, a 50 MHz antenna system should use an antenna spacing of two meters.
This rule depends on the level of wow or inductive response present at the particular site.
Processing affects only displayed data, not recorded data.
Other Types of Filters
For dealing with the inductive wow response, high pass filtering is necessary. If an alternative
high pass filter is available or you want to try a different type of high pass filtering, the raw data
contains all of the information and experimentation can be carried out using the raw data.
A DC removal can also be used to remove a DC level from all the traces in the input data set.
This is done by taking all the points in each trace and calculating the average signal level for
that trace. This value is then subtracted from each point in the trace. This process is repeated
for each trace in the data set. Typically, traces will have approximately the same DC shift in a
given data set. DC removal, in some cases, can be used instead of DEWOW. For example, a
DC shift correction applied to high frequency radar data rather than a DEWOW correction may
be more effective in reducing artifacts.
If you are unsure about which correction to apply use DEWOW.