Very strange damping effect

[Riss]

Probe type DD - transmitting coil -1.6 millihenry, its resistance is 4.5 ohms, its own resonant frequency (measured with the cable, of course) = 200 kilohertz - the calculated total capacitance is 380 picofarads. Receiving coil - 5.4 millihenry, resistance - about 24 ohms, its own resonant frequency -100 kilohertz, the calculated capacitance is 470 picofarads. The transmitting coil is included in the H - bridge with 4 pieces of 6N60. Bipolar PI, about 200 microseconds current flows through the coil. About 12 microseconds after the current through the coil has died down (the oscilloscope probe is connected to both ends of a 0.1 ohm resistor connected in series to TX coil ) very weak decaying sinusoidal oscillations with a period of about 28-30 microseconds are observed (which is very strange!!!). Without a damping resistor, this transmitting coil has a terrifying "ringing" with a period of about 6 microseconds (the H bridge adds capacitance ). I changed and tried everything, I thought, but I could not understand why the period of these oscillations is like that?!?

[Riss]

The probe has a diameter of 32 cm. On it is the stone of pure magnetite. The receiving coil is shunted with a 4.3 kilohm resistor. Photo 098 is directly from the receiving coil (without amplification), the oscilloscope probe is in position 1/10, the oscilloscope sensitivity is 2 millivolts per division. Photo 538 - the same conditions, but the stone is positioned on the probe, as in the photo. 146 - like 538. 955, 542, 016, 777 - current through a 0.1 ohm resistor. 468, 635, 837, 689,186,123 and 978 - above is the current through the coil (a little over 1 ampere), and below is the voltage on the transmitting coil from one arm of the X-bridge. 068 – the same, but without damping. 175,718 – the ringing without damping. 332,233 – the ringing from one arm, but with damping. The voltage was measured at a sensitivity of 50 volts/division.

[Riss]

I am adding the remaining 10 photos...the effect in question is clearly visible in photos 123 and 955 .A 0.1 ohm resistor is mounted on one terminal of the TX coil . The mass of the probe on channel 1 of the oscilloscope is hooked to the common point of the 0.1 ohm resistor and the TX coil. The probe clip on channel 2 ( it only measures voltage ) is hooked to the other end of the TX coil. The output of one arm of the H -bridge is connected to the 0.1 ohm resistor, the other arm of the H -bridge is connected directly to TX coil . Photos 175, 718, 332, 233 are from channel 2 (one arm of the H -bridge) with the oscilloscope ground connected to the minus of the bridge power supply - about 8 volts.

[Carl-NC]

2 things would help.
First, show a schematic of the TX circuit and how the oscope probes are attached.
Second, show 1 photo at a time, inline, and explain what it is and what is wrong with it. Like this:

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This is the blahblah waveform with V/div = ___ and t/div = ___. It shows blahblah....

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Sorry, with 20 photos that I have to keep clicking on and some confusing text, I have no idea what's going on.

[Detectorist#1]

Hello Riss,
It is a little strange to use 6N60 in simple H-bridge with maybe 12V power supply. Max voltages on the TX coil are far from 600V. Carl is right - first give to us used schematic with damping resistor and without damping resistor. Also how current sensor resistor is connected (serially to TX coil or in common source point of lower FETs) and how the screens of the two coils ( if they exists) are connected?