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In accordance with the research plan (topic code FMNN-2019-0004, state registration number AAAA-A19-119020190065-6), LAHD continued work on the creation of a modern hardware and software measuring complex for conducting electromagnetic sounding of the earth's crust using the TEM method using pseudonoise sounding signals.

In September this year, LAHD employees carried out a series of field experiments with a manufactured experimental sample of the measuring complex. The main tasks solved in the process of experimental work are further development of the technology for conducting field measurements, improvement and debugging of algorithms and software for data processing. The goal is to obtain high-quality curves of the field formation in a wide dynamic (≥ 150 dB) and frequency (0.2 ÷ 40,000 Hz) ranges of recorded signals. Field experiments were carried out at the near test point "Polygon, MGD".

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Five measurement sessions were performed, each of which consisted of two stages. At the first stage, the responses of the earth's crust to the impact in the form of pulsed M-sequences of the magnetic flux created in the earth's crust by the current flowing in the induction probe frame were recorded. At the second stage, the measuring channel was calibrated using the same shape as when probing the M-sequences of current pulses, but supplied to the graduation coil of the induction sensor.

When processing the sounding and calibration data, the difference between the recorded sounding and calibration signals was calculated. Further, the correlation processing of the difference signal with an ideal single probe M-sequence was carried out.

The use of the new technology for field measurements and data processing made it possible to exclude the direct field recorded by the induction sensor through the upper half-space (air). Only the response of the earth to the probing action that passed through the measuring channel was taken into account.