1.5 mm steel ball @ 8 cm

[pito]

The black mark on the stick is 8 cm from the coil, hard to see in the video, but when looking directly at the oscilloscope, the changes are visible at 10 cm.
https://www.youtube.com/shorts/Lr-NrUZ2_TA

[Detectorist#1]

Hi pito,

Yes, this is impressive! The high sensitivity for the steel is normal to PI MD. Also, the shape of the antenna points that this is differential RX construction with 2 RX coils. It is normal for differential construction to have high sensitivity. 7 years ago, I made similar construction and I was very proud from the results at the table. But when I began to move antenna with fixed ball - surprise! - the magnetic field of the Earth generates strong signals
and it is need to reduce 10 times sensitivity of the receiver to avoid false signals. All this happen with double samples in RX signal for EFE elimination. The things go better when I modified the detector to use bipolar TX pulses and changes in RX part. Also I think that it is not serious to show results at scope! You have to build whole MD with sound indication.

[pito]

I might make the sound later, for now out of curiosity I wanted to see from what distance it is possible to detect the ball.
the magnetic field of the Earth generates strong signals = not convinced about this EFE, it is on my list of investigation, simple test - moving coil 50 cm from earth with disabled Tx - I don't see EFE ......

[Detectorist#1]

Hi pito,

Go ahead, the signals depend of direction of moving.